• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-01-31
Hongzheng Zeng; Xing Chen

This letter presents the nonlinear analysis of a microwave p-i-n diode limiter using a finite-difference time-domain (FDTD) field-circuit simulator based on physical models, rather than an equivalent circuit in circuit simulation. The corresponding flat leakage power is simulated and analyzed at frequencies of 2.45 and 2.8 GHz, as well as at different ambient temperatures. Simulation results were in good agreement with experimental measurements, showing that the improved FDTD simulator can accurately model the “power jump” in flat leakage power curves as well as the effects of temperature on the p-i-n diode limiter.

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-01-15
Jiangling Dou; Shu Jiang; Tao Shen; Jianxiao Ma

An effective analysis method is proposed for broadband GaAs Schottky diode-based frequency multipliers. Frequency multipliers output power nulls in the working frequency band have been estimated and removed from the perspective of multiplier transmission notches. Transmission characteristics of the input signal from radio frequency RF input port to Schottky lumpports and the desired harmonic from Schottky lumpports to RF output port are analyzed. Key circuit parts and their dimensions that result in transmission notches are intuitively calculated and analyzed based on 3-D electromagnetic simulation. To verify the above-mentioned technique, three multiplier prototypes based on single, dual, and reverse Schottky junction diodes are fabricated and measured. The measured output power nulls coincides with simulated transmission notches. The proposed method can be utilized to intuitively and quickly remove output power nulls in broadband frequency multipliers working frequency band.

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-02-04
Zewei Wu; Xiaoyi Liao; Keqiang Wang; Minxing Wang; Youlei Pu; Yong Luo

A new topology to excite circular TE 02 mode for studying of gyrotron traveling-wave tube (gyro-TWT) is presented. The mode generator consists of a rectangular TE 10 to cross waveguide TE 44 mode converter and a cross waveguide TE 44 to circular TE 02 mode converter. To obtain a high-purity TE 02 mode output and make the generator compact, a cross waveguide with sidewall coupling apertures and a novel mode transition section with metal diaphragm are introduced. The proposed mode generator is fabricated and measured. A good agreement between simulation and measurement is obtained, and the 1-dB bandwidth from 28 to 34 GHz is obtained in back-to-back test. The angle-independent transmission demonstrates high mode purity and the presence of TE 02 mode confirmed by the field pattern measurement. The mode exciter features high mode purity, broad bandwidth, and is easy to be fabricated, which can be applied to cold-test experiments of gyro-TWT components and the high power transmission line devices.

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-01-10
Jen-Tsai Kuo; Chong Lay Ng

Explicit solution is derived for the exact synthesis of cross-coupled quadruplet filters with a real-frequency zero pair. Through a comparison of two-port S-parameters of the low-pass prototype circuit with the canonical generalized Chebyshev insertion loss function, a univariate quadratic function is formulated, and all element values of the circuit are explicitly expressed in terms of the designated zero and in-band ripple levels. The analytical expression of the sidelobe attenuation level is also obtained in terms of the zero, and vice versa. Results are checked against those from the existing literature.

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-02-04
Liang Sun; Hong-Wei Deng; Yi-Fan Xue; Jia-Ming Zhu; Si-Bei Xing

In this letter, compact-balanced bandpass filter (BPF) and filtering crossover are proposed with intrinsic common-mode (CM) suppression by using a single-layered substrate-integrated waveguide (SIW) cavity. The SIW cavity with low profile is TE n0m mode resonator, which has only one nonzero electric field component. Hence, it is also a natural frequency selection device of the differential signal. Meanwhile, the CM signal cannot excite the cavity due to the characteristics of perfect electric conductor (PEC) and perfect magnetic conductor (PMC). For the design of the balanced SIW BPF, the differential-mode (DM) equivalent half circuit is a single-ended SIW filter with height halved. Furthermore, the microstrip differential transition structure is designed to excite the SIW cavity and has little conversion between DM and CM. On this basis, a compact SIW-balanced filtering crossover is proposed using the degenerate modes TE 102 and TE 201 . Finally, compact third-order SIW-balanced BPF and filtering crossover are designed and fabricated, and the measured results show good agreement with the simulated ones.

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-20
Zhen Tan; Qing-Yuan Lu; Jian-Xin Chen

In this letter, a new differential dielectric strip resonator (DSR) filter with dual passbands is proposed. By loading a pair of ground bars underneath the traditional half- wavelength ( $\lambda /2$ ) DSR with high permittivity (supported by a low-permittivity substrate with the bottom ground plane), the TM 10 and TM 30 modes can be controlled to be in a close spacing. Meanwhile, both of them can be differentially excited for the design of the differential dual-band bandpass filter (BPF). The external quality factors and coupling coefficients for both bands can be independently controlled through proper layout; meanwhile, the common-mode (CM) suppression in the two differential-mode (DM) passbands is more than 25 dB. Finally, a differential DSR BPF with dual-band response operating at 8.13 and 11.13 GHz is given to verify the proposed idea.

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-01-23
Hyunjin Ahn; Ilku Nam; Ockgoo Lee

Design equations for the parameters of a lumped-element quadrature coupler with impedance transforming are derived. Considering on-chip implementations, it has a smaller size as compared to a quarter-wavelength transmission-line-based coupler. A 2.47-GHz quadrature coupler with impedance transforming is implemented using GaAs technology for verification. The measurement results show that the fabricated coupler achieves an insertion loss of 3.39 dB with a phase imbalance of 0.8° for through and coupled outputs at 2.47 GHz.

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-01-10
Zhenjiang Zhao; Tayeb A. Denidni

In this letter, a new hybrid coupler with symmetrical square feed using printed ridge gap waveguide (RGW) technology is introduced and investigated. This structure can find important applications in beamforming network designs. The proposed coupler has a compact size of $1.12\lambda _{g} \times 1.12\lambda _{g} \times 0.14\lambda _{g}$ and shows promising results at millimeter-wave Ka -band around 30 GHz, especially in terms of amplitude balance bandwidth and loss. The simulated results are compared with the measured data and a good agreement is achieved.

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-01-09
Mi Zhou; Han Ren; Bayaner Arigong

In this letter, a novel microstrip line balun with transparent port impedance and unconnected flexible output arms is presented. The proposed balun is designed from a symmetric four-port device with an open end at its isolation port. To achieve balun function, a shunt stub is attached between the unbalanced port and the virtual open-ended port to generate a transmission zero under the even-mode circuit. Its odd-mode circuit is treated as an impedance transformer, where the transformer is independent of the terminal impedance. In addition, the proposed balun has flexible open arm branches and does not require a closed loop structure, which provides design flexibility to integrate with other devices compared to conventional closed-loop branch line baluns. The theoretical design equations are derived first to prove the design concept. Then, two prototypes are designed with 35 $\Omega$ system impedance and loaded with 50 and 75 $\Omega$ port impedance, and the measured results match well with the simulation, which further validates the proposed design theory.

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-02-04
Zheng-Bin Wang; Xin Wei; Han-Ping Fang; Hua-Mei Zhang; Ye-Rong Zhang

In this letter, a compact and broadband directional coupler is proposed for high-power radio frequency applications in the frequency band of 5–150 MHz. The coupler is composed of a suspended semiflexible coaxial cable and a series of equalizers composed of lumped components. Such design exhibits excellent performance in high power handling capacity (~kW), high directivity (~35 dB), low return loss (>20 dB), and flat coupling coefficient (45 ± 1.3 dB).

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-01-06
Jong-Min Yook; Young-Gon Kim; Wansik Kim; Sosu Kim; Jun Chul Kim

In this letter, a quasi-coaxial through-silicon-via (TSV) is presented for millimeter-wave integrated circuit (IC) packaging. The quasi-coaxial-via (Q-COV) structure in which one side ground metal is removed can minimize the interconnect length when it is mounted, in comparison to the coaxial-via (COV) structure. Simulation analysis shows that the Q-COV has similar electrical characteristics as the COV up to 100 GHz even though there is no GND on one side. To make the small signal core of the Q-COV, the silicon-core metallization process was used and a Si-interposer with Q-COVs of 50- $\mu \text{m}$ core diameter was fabricated and mounted on the glass board for signal transition analysis. The measured transition loss in the mounted Si-interposer was very small, only about 0.6 dB at 100 GHz, and the return loss was more than 20 dB for the entire measured frequency band (0–110 GHz).

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-01-03
Philipp Hügler; Tobias Chaloun; Christian Waldschmidt

A robust and wideband differential microstrip line-to-WR6-waveguide transition for mixed multilayer PCBs at $D$ -band is presented. The PCB stack is composed of three standard RF core materials with standard thicknesses. Compared to other inline transitions above 90 GHz, which are designed for single substrates, it can be applied to mixed multilayer circuits. The tapered transition is only 8.0-mm wide and 2.5-mm long, has an insertion loss between 1.2 and 1.8 dB, and a return loss higher than 10 dB for 30-GHz bandwidth around the center frequency of 120 GHz.

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-01-15
Huy Nam Chu; Ming-Jyun Jiang; Tzyh-Ghuang Ma

A new on-chip dual-band Wilkinson power divider (WPD), developed on a GaAs-based integrated passive device (IPD) process, is designed at 28/60 GHz for millimeter-wave (mmW) applications. Composite right/left-handed lines in microstrip form are employed to achieve the dual-band property. Thanks to the low-loss feature of the GaAs-based IPD process, the proposed mmW WPD ensures comparable performance when compared to its counterparts at microwave frequencies. Besides, the proposed design, one of the few on-chip dual-band WPDs designed in mmW bands, yields better performance in terms of input matching and power loss when compared with the previous work.

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-01-03
Qiuyan Jin; Jinchun Gao; Lingyu Bi; Yuqi Zhou

A novel behavior model expressing the effect of contact pressure on the passive intermodulation (PIM) performance was proposed and experimentally verified. The finite-element analysis (FEA) model of the central conductor of a typical coaxial connector was developed based on the structural analysis and contact surface modeling. Simulation results identified the current densities in the contact areas. The third-order intermodulation (IM3) power was mathematically predicted by using the nonlinear current truncation distortion model in electrical contact points. Accelerated tests were designed and conducted to produce connector samples with different contact pressures. These samples were measured by a PIM analyzer in a 900-MHz frequency band. Good agreement was obtained between the predictions and the measurements, validating the PIM analysis method and results.

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-02-05
Zhilin Su; Cuiping Yu; Bihua Tang; Yuanan Liu

This letter presents a wideband power amplifier (PA) with high efficiency integrated filtering characteristic. A novel bandpass filtering impedance transformer was proposed, which consists of a terminated coupled line structure (TCLS) and impedance tuning network (ITN), to realize the input matching network (IMN) and output impedance matching network (OMN). To enhance the efficiency of PA, the second harmonic has also been controlled perfectly. This design method can not only provide high-selectivity bandpass responses and high efficiency but also broaden the operation band. For demonstration, a wideband filtering PA operating at 2.2 GHz with a bandwidth of 400 MHz by employing a 10-W GaN HEMTs is fabricated. Measured results show the maximum drain efficiency (DE) is 68.3%–78.4% in the design band. Meanwhile, a good filtering performance was obtained. The rejection level was larger than 52.8 and 31 dB for the lower and higher suppression bands, respectively. In addition, simulation results show that the IMD2 and IMD3 were also improved simultaneously. In particular, the IMD2 value was improved about 30–40 dB.

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-01-28
Hao-Yu Liu; Xiao-Hu Fang; Kwok-Keung M. Cheng

This letter presents a modified Doherty power amplifier (DPA) combining network with wide bandwidth (BW) and high power utilization factor (PUF). For the first time, the impact of the excessive phase dispersion of matching networks on the performance of conventional broadband DPA is analytically revealed. For dispersion compensation, an optimized adaptive combining load is introduced to enhance the achievable DPA BW and PUF. For verification, a 42-dBm equal-cell DPA is prototyped to cover 1.4–2.55 GHz. Measurement results indicate that, over the prescribed frequency range, a PUF of over 0.95, back-off efficiency (6 dB) of 48%–58%, and saturation efficiency of 62%–74% can be achieved. Moreover, under WCDMA excitation, the adjacent channel leakage ratio (ACLR) was found to be better than −32 dBc with average efficiency of over 45% without applying digital predistortion techniques.

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-01-28
Zach Griffith; Miguel Urteaga; Petra Rowell

We report a three-gain-stage 88–104-GHz $W$ -band solid-state power amplifier (SSPA) monolithic microwave integrated circuit (MMIC) having modest 100–140-mW output power ( $P_{\mathrm {out}}$ ), high gain, and high power-added efficiency (PAE). The MMIC technology is 250-nm InP HBT. PA $S_{21}$ gain is 29.5 dB with ±0.5-dB variation. PA 3-dB $S_{21}$ gain roll-off is between 88 and 104.5 GHz with high $\vert S_{11}\vert$ and $\vert S_{22}\vert$ return losses. DC power ( $P_{\mathrm {dc}}$ ) is 0.41 W. Across 88 –104 GHz, the PA-saturated output power $P_{\mathrm {sat}}$ is 100–120 mW with greater than 20-dB power gain and 20% PAE. At 92 GHz, peak 120-mW $P_{\mathrm {out}}$ with 20-dB gain and 24.7% PAE is demonstrated. $P_{\mathrm {out}}$ at 1-dB gain compression OP $_{\mathrm {1-dB}}$ is estimated to be 15–17 dBm. At 94 GHz and an elevated output stage bias (0.50-W $P_{\mathrm {dc}}$ ), 140-mW $P_{\mathrm {out}}$ with 20-dB gain and 24.4% PAE is demonstrated. This work contributes to and improves the state of the art for $W$ -band PAs in the simultaneous performance areas of power, gain, and PAE.

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-01-24
Van-Son Trinh; Jung-Dong Park

We present a $W$ -band four-stage power amplifier (PA) in a 65-nm CMOS using a push–pull configuration with inductive feedback neutralization which achieves the highest figure of merit (FOM) compared to the recently reported CMOS PAs. The device was gradually tapered from the output to the input stage to optimize the power-added efficiency (PAE) while achieving high power gain with compact impedance matching with a transformer (TF). Interstage conjugate matching was also carried out with a TF to design a compact high-gain PA. Working under a supply voltage of 1.2 V, the proposed PA achieves a power gain of 28.2 dB with the 3-dB gain bandwidth of 7 GHz (76.8–83.8 GHz), a saturated output power of 16.3 dBm, and a peak PAE of 14.1% at 81.6 GHz with power dissipation of 234 mW. The total chip size is 0.714 mm 2 , and the core size excluding pads is only 0.121 mm 2 .

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-01-07
Fabian Thome; Arnulf Leuther; Oliver Ambacher

This letter presents the design and performance of two single-pole double-throw (SPDT) switches operating in $V$ -band (50–75 GHz) and $W$ -band (75–110 GHz). The millimeter-wave (mmW) integrated circuits (MMICs) are fabricated in a 50-nm gate-length metamorphic high-electron-mobility transistor technology. Special attention was paid to the reduction of the insertion loss (IL). Thus, both switch MMICs achieve an IL of 1–1.6 dB (average 1.2 dB), covering the entire $V$ -band and $W$ -band, respectively. The isolation (ISO) of the switches is better than 31.6 and 28.5 dB, respectively. The input power for 1 dB of IL compression is at least 22 and 19 dBm, respectively. A wafer mapping of both circuits exhibits a high yield and low spread of IL and ISO. Based on the given results, the presented SPDT switch MMICs demonstrates state-of-the-art performance.

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-25
Eui Min Jung; Yepu Cui; Tong-Hong Lin; Xuanke He; Aline Eid; Jimmy G. D. Hester; Gregory D. Abowd; Thad E. Starner; Wang-Sang Lee; Manos M. Tentzeris

Unlike conventional energy harvesters that are tuned to individual frequencies and are directional, the proposed wideband (23% fractional bandwidth), omnidirectional system harvests from all FM towers in vicinity. Hence, it does not require each sensor node to be carefully aligned to any one source and makes itself suited for mass-deployment applications such as precision agriculture and structural health monitoring. It harvests as much as 923 $\mu \text{W}$ on a rooftop at 1.54 km from an FM tower while retaining omnidirectionality partly thanks to the proposed antenna, which has a wider bandwidth and a higher measured gain (2.0 dBi) than the commercial reference wideband antenna. It achieves competitive efficiency (56%) and sensitivity (−17 dBm) while retaining wideband operation rather than being specifically optimized to individual frequencies. The system (fabricated on low-cost FR4) harvested outside ambient FM energy indoors at the same 1.54-km location to power a wireless sensor node without needing to shut down periodically.

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-01-01
Qiuyan Jin; Jinchun Gao; Hang Huang; Lingyu Bi

An equivalent circuit model of a passive system with nonlinear characteristics was developed to simulate the forward and reversed passive intermodulation product (PIMP) powers. Mitigation methods based on signal compensation were proposed and used to reduce the interferences of passive intermodulation (PIM). The cancellation phenomena of third-order PIMP powers were observed both in the active and passive signal compensation simulations, followed by some theoretical analysis. The advantages and disadvantages of each mitigation method were discussed in detail, providing flexible selections in low-PIM design and PIM elimination in specific applications.

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-01-07
Jianxin Jing; Chao Yu

In this letter, a novel multibeam digital predistortion (MB-DPD) technique is proposed to linearize multiple beams simultaneously targeted at the multiuser scenario of millimeter-wave (mmWave) analog beamforming transmitters. It is achieved by effectively constructing the predistorted signal for each beam to remove both the intrinsic nonlinear distortion of power amplifier (PA) and the multibeam interference incurred by all beams except the targeted main beam. To validate the proposed technique, a two-beam test on an analog beamforming transmitter was carried out and the measurement results have shown that the proposed method can effectively realize the multibeam linearization, providing a promising solution for mmWave multiuser applications.

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-02-13
Sung Jun Lee; Jae Ho Jung; Jong-Won Yu

A transmitter leakage canceller (TLC) having high isolation from a transmitter (TX) to a receiver (RX) is proposed, which is for a single antenna continuous-wave (CW) radar in the 2-GHz band. The proposed TLC is based on three points to obtain sufficient TX-to-RX isolation in a bandwidth of tens of MHz. The first is the use of a quasi-balanced structure in a leakage path and an antileakage path, which makes both signals in the two paths similar in a wide bandwidth. The second point is the adoption of active circuits in the antileakage path, which provides sufficient cancellation between the two signals. However, this adoption makes both signals in two paths with different phase slopes versus frequency; therefore, the sufficient cancellation is confined to a narrow bandwidth. The last is the application of a delay line in the leakage path, which compensates the different phase slopes. Thus, a bandwidth feature of tens of MHz is obtained. Laboratory measurements show more than 60 dB TX-to-RX isolation for an arbitrary targeted 20-MHz bandwidth from 2.3 to 2.7 GHz.

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-01-09
Alwin Reinhardt; Leve Freiwald; Timo Jaeschke; Nils Pohl; Michael Höft

This letter introduces a bistatic $W$ -band continuous wave radar sensor based on a silicon-germanium (SiGe) transceiver chip with respect to its ability to measure aerosol streams with particles in the micrometer range. The introduced homodyne SiGe sensor relies on a phase-locked loop (PLL)-stabilized oscillator embedded into a monolithic microwave integrated circuit (MMIC), while up until now particle stream monitoring radars are built as waveguide systems. After the radar hardware, including the bistatic antenna configuration, is examined, the physical relationships between the particle stream and the hardware parameters are given. Finally, two different experiments with coarse metallic steel particles and fine coffee powder streams are presented and analyzed.

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-24
Hong-Yi Gan; Wen-Sheng Zhao; Li He; Yufeng Yu; Kuiwen Xu; Fei Wen; Linxi Dong; Gaofeng Wang

This letter proposes a microwave planar sensor for the characterization of magnetodielectric materials. The sensor is designed by loading microstrip lines with complementary split-ring resonators (CSRRs). Two patches are connected to the microstrip lines to couple with the CSRRs, and a pair of 50- $\Omega$ resistors are in series with the lines to provide a notch. The designed sensor can extract the permittivity and permeability of the magnetodielectric materials simultaneously. A prototype of the designed sensor is fabricated and measured for validation of characterizing the magnetodielectric materials.

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-02-13
Ramanand Sagar Sangam; Rakhesh Singh Kshetrimayum

The dispersion diagrams for the proposed spoof surface plasmon polariton (SSPP) unit [1, Fig. 1(b)] and the substrate-integrated waveguide (SIW) unit [1, Fig. 1(c)] are plotted in [1, Fig. 2] , which are incorrect and the correct dispersion curves for the same are presented here, as shown in Fig. 1 . The dispersion curves are analyzed and plotted for mode-1 simulation in the eigenmode solver of CST microwave studio. Furthermore, the dispersion curve with optimized dimensions, $L_{i}$ and $W_{i}$ , where $i\in (5,\ldots ,8)$ for the SSPP part [1, Fig. 1(a)] , is shown in Fig. 2 . The lower and upper cutoff frequencies for the passband of the filter are defined from the structural parameters of SIW and SSPP units, respectively. It can be seen from the dispersion curves of SIW and SSPP units [1, Fig. 2] that the lower cutoff frequency obtained from the SIW unit is around 7 GHz, while the upper cutoff frequency obtained from the SSPP unit is around 6 GHz ( $W=15$ mm of the SIW unit and $W=8$ mm of the SSPP unit). However, only the cutoff frequency in the dispersion curve of the SIW unit is correct, from where the lower cutoff frequency of the proposed BPF is set around 7 GHz. The dispersion curve of the SIW unit [1, Fig. 1(c)] with correct distribution trend is shown here in Fig. 1(b) . The passband of the proposed hybrid SSPP-SIW filter is about 7–11 GHz, and hence, the correct upper cutoff frequency for passband of the filter, as it can be seen from our corrected dispersion curve of the SSPP unit [see Fig. 1(a) ], is about 11 GHz. It can also be noted that $p$ is the period of SSPP in our corrected dispersion curves.

更新日期：2020-02-14
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-31
Wei-Jun Chen; Ying Tian; Jun Quan

A novel unconditionally stable finite-difference time-domain (FDTD) electromagnetic simulation method based on the weighted Laguerre polynomials (WLPs) and isotropic dispersion (ID) finite difference scheme is proposed, which introduces WLPs in the time domain and ID finite difference scheme in the space domain. Based on the analysis of monochrome waves, its numerical dispersion relation is obtained. In order to verify the superiority of this method, an example of plane wave propagation in a 2-D dielectric-loaded cavity is given. Compared with the conventional WLP-FDTD method, this method not only keeps good simulation accuracy but also requires less computing time and memory.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-11-28
Jinghui Shao; Xikui Ma; Zhen Kang; Jiawei Wang

In this letter, the propagation of an electromagnetic (EM) wave in a time-variant medium is treated with a novel methodology stemming from the precise integration time domain (PITD) method. This methodology is a generalized version of the conventional PITD method (thus GPITD, for short). In the GPITD method, the electric displacement and the magnetic induction serve as the iteratively calculated components. In order to overcome the difficulty in implementing the precise integration (PI) routine caused by the time variation of the original coefficient matrix, an effective piecewise constant coefficient matrix is constructed. Both the numerical dispersion relation and the numerical stability condition of the GPITD method are described. Successful application of the GPITD method to solve the EM propagation problem associated with a layer whose permittivity suffers: 1) an abrupt change to a new value and 2) a sinusoidal modulation, confirms its effectiveness.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-23
M. Ebrahimpouri; L. F. Herran; O. Quevedo-Teruel

This letter demonstrates that glide symmetry can be used to match the impedance of highly dense dielectric profiles in wide angle and broad bandwidth. Using glide-symmetric metasurfaces permits tuning the magnetic properties of materials, so high values of permittivity can be matched to free space in wideband. This matching is achieved without disturbing the performance of the device, since the refractive index remains fixed. The performance of the proposed matching method is validated through measurements for normal incidence. For oblique incidence, a hyperbolic dielectric lens is matched with glide-symmetric structures in simulations. These simulations demonstrate a smooth transmission of the fields, manifesting a well-matched profile of the lens.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-23
Alexander Zakharov; Sergii Rozenko; Sergii Litvintsev; Michael Ilchenko

In this letter, new patterns of symmetric trisection bandpass filter (BPF) with reflection-type half-wave resonators, mixed cross-coupling, and different paths for signal propagation are discussed. The various coordinates of the conductive connection of loads to the end half-wave resonators are used in the filter. This leads to different signal paths from input to output of the filter. Due to the various connections of loads and mixed cross-coupling, satisfying condition $K_{13} = 0$ , the same filter has different frequency responses. When we use one port position, two transmission zeros, located on the $\sigma \!$ -axis of the complex plane $s = \sigma + j\Omega$ , are generated, and we obtain a flat group delay. If another port position is used, two transmission zeros are generated on the $j\Omega$ -axis, $\Omega = (\omega /\omega _{0} - \omega _{0}/\omega)$ /fractional bandwidth (FBW), and a quasi-elliptic response is presented. In both cases, two transmission zeroes are equidistant relative to $s =0$ and they are controlled by a mixed coupling coefficient. The results of the measurements and simulation are presented.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-17
Phirun Kim; Yongchae Jeong

This letter presents the design of mixed quarter- and one-eighth modes substrate integrated waveguide (SIW) bandpass filter (BPF). The transmission zeros (TZs) of the proposed SIW BPF can provide wide stopband response and high selectivity characteristics by using different mode SIW cavities. For validation, two- and three-stage SIW BPFs with Chebyshev response were designed at a center frequency ( $f_{0}$ ) of 8 GHz. The measured results are consistent with the simulations. For two-stage BPF, the insertion loss smaller than 0.9 dB is measured within the passband of 0.65 GHz (7.75–8.4 GHz). The return loss higher than 19.7 dB is measured within the same passband. The spurious is produced at around 18 GHz ( $< 2.25f_{0}$ ). The stopbands are attenuated more than 17.31 dB from the dc to 5.68 GHz ( $0.71f_{0}$ ) and from 9.28 GHz ( $1.16f_{0}$ ) to 16.67 GHz ( $2.08f_{0}$ ). The TZs are produced at 10 GHz and around 18 GHz due to a small cross-coupling between source/load and the interaction of the higher resonant modes of cavities, respectively. For three-stage BPF, the $\vert S_{21}\vert$ and $\vert S_{11}\vert$ smaller than −1.3 dB and −18 dB are measured within the passband of 7.57–8.45 GHz fractional bandwidth (FBW = 11%), respectively. The TZs are produced at 1.102, 1.9, and $2.39f_{0}$ and provide higher selectivity and attenuation compared to two-stage BPF.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-17
Naira Jguirim; Damien Passerieux; Nicolas Parou; Claire Dalmay; Pierre Blondy

This letter presents the design and fabrication of a 287-GHz resonator and a bandpass filter. The fabrication is conducted using an additive microfabrication process, based on successive photolithography and metal electroplating steps. This process has allowed the fabrication of a single-cavity resonator and a 3.5% relative bandwidth two-pole bandpass filter. The cavity has a measured unloaded $Q$ of 137, and the filter has a measured loss of 4.6 dB and matching better than 20 dB in very good agreement with E-M simulation results.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-23
Rui Ting Yan; Hao Chi Zhang; Pei Hang He; Zheng Xing Wang; Xuanru Zhang; Xiaojian Fu; Tie Jun Cui

Spoof surface plasmon polaritons (SSPPs) have been considered as a new-type surface wave transmission line (TL) because of its single line feature. However, it cannot be directly fed by the measured system because the transmission mode of SSPP TLs is totally different from the traditional TLs like microstrip lines. Also, the existing solutions require complicated structures and a big area on the circuit space to complete the transition between the two different propagation modes. Here, we propose an ultracompact and simple transition from the microstrip line to the SSPP single-conductor TL, consisting of a very short section of gradient corrugations and a specially designed flaring ground etched on the bottom side of the SSPP TL. Numerical simulations show a good agreement with the experimental results, showing high transmission efficiency for the proposed transition in a broad relative bandwidth from 4.5 to 11.5 GHz. Moreover, this SSPP feeding prototype is easy to migrate to other single-conductor SSPP devices.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-09
Ting Cai; Chang Chen; Xiang Zhang; Fujiang Lin; Hualiang Zhang

An analog signal-interference dual-narrowband bandpass filter (BPF) by combining transmission lines and surface-acoustic-wave (SAW) resonators is proposed. The filter is based on three-path transversal filtering sections (TFSs) with two embedded one-port SAW resonators. By cascading the TFSs in-series through transmission lines, passbands with enhanced fractional bandwidths (FBWs) (i.e., larger than the electromechanical coupling coefficient $k_{t}^{2}$ of the employed acoustic-wave resonator) can be realized. For the purpose of validation, a two-stage microstrip dual-narrowband BPF with two passbands located at 868.95 and 916.5 MHz has been designed, fabricated, and characterized. It demonstrated an insertion loss (IL) of 0.89 dB at 868.95 MHz, 1.57 dB at 916.5 MHz and a bandwidth (BW) of 3.2 MHz (FBW $=3.21\,\,k_{t}^{2}$ ) at 868.95 MHz, and 2.3 MHz (FBW $=1.92\,\,k_{t}^{2}$ ) at 916.5 MHz.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-09
A. Monje-Real; N. J. G. Fonseca; O. Zetterstrom; E. Pucci; O. Quevedo-Teruel

A fully metallic glide-symmetric waveguide filter with transmission in $Ka$ -band and attenuation at its second harmonic is proposed. The filter is low-loss and cost-effective for high frequencies, and it can be easily integrated with an antenna. Glide symmetry and the possibility of breaking this symmetry provide an additional degree of freedom for passband and stopband control. A new kind of 2-D glide symmetry, referred to as braided glide symmetry, is presented, showing an increased attenuation per unit cell.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-16
Qun Li; Xiong Chen; Pei-Ling Chi; Tao Yang

This letter presents a varactor-based tunable bandstop filter (BSF) using distributed coupling microstrip resonators with the capacitive terminal. Each distributed coupling microstrip resonator consists of a coupling microstrip line, a varactor, and a capacitive terminal which is a floating pad connected to the cathode of the varactor. The capacitive terminal serves not only as a bias pad for the control voltage but also as an intrinsic capacitive path to ground. Compared to the conventional inductive terminal with the metallized via, the capacitive terminal can be beneficial to realize much higher frequency responses by taking advantage of the capacitance to ground from the floating pad. High stopband suppression level is achieved by cascading multiple distributed coupling microstrip resonators. For demonstration, a tunable BSF prototype with the frequency tuning range of 11.3–16.5 GHz (37%) is designed and fabricated. Measured and simulated results agree well and validate the design principle.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-23
Jelena Radic; Miodrag Brkic; Alena Djugova; Mirjana Videnovic-Misic; Bernhard Goll; Horst Zimmermann

An ultralow-power and low-complexity impulse radio ultrawideband (IR-UWB) transmitter (TX) is fabricated in the low-cost 180-nm United Microelectronics Corporation (UMC) CMOS technology. The TX offers control of the power spectral density (PSD) by using a tunable pulse generator and a controllable switched oscillator. It supports on-off keying (OOK) coding and occupies a total die area of 0.35 mm 2 . The measured results show the transmitter output amplitude of 130 mVp-p with the pulse width of 1.0 ns, and the PSD with 10-dB bandwidth from 3 to 8.8 GHz. The total dc power consumption is 0.6 mW, corresponding to the energy consumption of 3 pJ/pulse at 200-MHz pulse repetition frequency.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-16
Hong Soo Park; Sun K. Hong

A novel broadband RF-to-DC rectifier using an uncomplicated matching approach is proposed and tested. The proposed rectifier is based on a voltage doubler-type configuration and broadband matching is achieved by simply adding two inductors in series with each of the diodes, canceling out the large capacitance inherent in the diodes as well as producing resonances over a wide bandwidth. This uncomplicated matching network allows for a smaller circuit footprint while providing a wide bandwidth. The proposed rectifier is validated via simulation and measurement. The results demonstrate that a rectification efficiency of more than 50% is maintained over a bandwidth of approximately 83% (0.54–1.3 GHz) at 5-dBm input power, with the maximum rectification efficiency of 80% at 10-dBm input power.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-16
William Hallberg; Dhecha Nopchinda; Christian Fager; Koen Buisman

A measurement-based approach for the analysis of Doherty power amplifiers (DPAs) is presented. The DPA behavior is emulated using an active load–pull setup, exciting a single device under test (DUT) in either of two states, corresponding to the main and auxiliary branches in a DPA. The dynamic loading condition in one state is determined from the Doherty combiner parameters and the knowledge of the DUT behavior in the other state. By iterating between these states, the measurements converge to the true behavior of a complete DPA. This method provides measurement-based insights in the dynamic loading conditions and the corresponding individual device performance without having to manufacture the full DPA. The method is demonstrated by emulating and cross-verifying a 2.14-GHz DPA.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-09
Utku Alakusu; M. Sadegh Dadash; Stefan Shopov; Pascal Chevalier; Andreia Cathelin; Sorin P. Voinigescu

A 240-GHz direct conversion I–Q receiver with 74-GHz RF bandwidth is reported. It features a mixer-first architecture with fundamental local oscillator (LO)-frequency Gilbert-cell downconversion mixers, variable-gain baseband amplifiers, and a 240-GHz LO source, making it the first fully integrated 240-GHz I–Q receiver. With a phase noise of −82 dBc/Hz at 1-MHz offset, the LO source has a 27-GHz tuning range and consists of a 120-GHz voltage-controlled oscillator (VCO), a frequency doubler, and a static divide-by-128 chain. The measured peak downconversion gain is 23 dB and is adjustable over 38 dB. Along with the IF bandwidth of 59 GHz, the wide RF bandwidth makes it suitable for both high data-rate communication and emerging quantum computing applications. The chip occupies an area of 1.837 mm 2 and consumes 859 mW.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-16
Jonas Lindstrand; Markus Törmänen; Henrik Sjöland

A wideband 65-nm CMOS power amplifier (PA) is presented, with a decade frequency range from 600 MHz to 6.0 GHz. In this frequency range, the output power exceeds 26.6 dBm and the power gain and power-added efficiency (PAE) exceed 18.1 dB and 49%, respectively. For a 7.5-dB peak-to-average-power-ratio (PAPR) long term evolution (LTE) signal at 1.9 GHz, the circuit provides an average output power of 19 dBm, with a PAE of 40%, and an adjacent channel leakage ratio (ACLR) exceeding −31 dBc. In LTE measurements at 5.9 GHz, the average output power, PAE, and ACLR are 18.5 dBm, 38.8%, and −30 dBc, respectively, using supply modulation and baseband predistortion. The wide bandwidth (BW) and high performance are achieved by introducing a dual output topology with an off-chip higher order output-matching network, combined with a positive feedback cross-coupled differential cascode amplifier stage. By using supply modulation and dynamic gate bias with an injection-locked PA, improved back-off efficiency, and acceptable out-of-band and in-band distortion is obtained. The integrated circuit occupies an area of 1.0 $\times$ 0.73 mm 2 in standard 65-nm CMOS technology and uses a supply of 3.0 V.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-01-01
Chun-Yu Lin; Yi-Quan Fu; Jih-Yan Wang

A compact electrostatic discharge (ESD) protection cell is proposed for multi-band millimeter-wave (MMW) circuits in nanoscale CMOS technology. The proposed ESD protection cell consists of a silicon-controlled rectifier (SCR) and a diode as the main ESD protection devices, and an inductor in this cell is divided into several sections to resonate at multifrequencies. The proposed design has been demonstrated for 28- and 67-GHz applications. The measurement results show that the proposed design exhibits lower loss at the specified frequency bands, higher ESD robustness, and sufficiently small layout area. Therefore, the novel compact ESD protection cell will be better for multi-band MMW applications in CMOS technology.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-17
Shixiong Deng; Changzheng Gao; Shubin Chen; Jiyong Sun; Kang Wu

The threshold is a key indicator of linearity for limiters. However, the threshold of silicon-based p-i-n diode limiters drops rapidly at low frequencies. This letter presents a novel method to improve the threshold of limiters for protecting analog-to-digital converters. A silicon-based p-i-n diode and a zener diode were stacked as a thicker p-i-n diode. Three 30–300-MHz limiters using the same p-i-n diode and different zener diodes were designed. Both the simulated and measured results are presented to verify this method. The results show that the thresholds were improved by 12, 19, and 21 dB, respectively.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-23

Microwave zero-bias rectifiers are fast devices capable of rectifying RF signals without applied bias, which have applications ranging from RF power detection to terahertz imaging systems. In this letter, we present gated nanowire field-effect rectifiers (NW-FERs) fabricated with a process compatible with other RF devices on a standard AlGaN-GaN high electron mobility transistor (HEMT) platform as a new potential RF zero-bias diode. Signal rectification relies on the electrostatic modulation of the gated-NW carrier concentration, which is optimized by a judicious NW width design. NW-FERs presented a large curvature (30.1 V −1 ), close to the theoretical limit (38.7 V −1 ) for ideal Schottky diodes, and an excellent tradeoff between a flat frequency response, up to a few tens of gigahertz, and a large responsivity (3000 V/W). The compatible fabrication process and the very good results provide a promising high-performance zero-bias diode architecture that could be integrated on AlGaN/GaN microwave monolithic integrated circuits (MMICs).

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2020-01-01
Xinlin Xia; Xu Cheng; Fengjun Chen; Xianhu Luo; Xianjin Deng

In this letter, an improved balanced Colpitts voltage-controlled oscillator (VCO) with a collector–emitter cross-coupled capacitors is presented. The proposed Colpitts structure can introduce a more robust oscillation startup condition. The noise-shifting technique is used to enhance the loaded quality factor of the tank, which improves the phase noise in turn. In addition, three-bit switches composed of enhancement-mode high-electron mobility transistors (E-HEMTs) are utilized to expand the tuning range and reconfigurability of the proposed VCO. In proof of the concept, a VCO prototype is fabricated in a GaAs BiHEMT [enhancement- and depletion-mode high-electron mobility transistor (E/D-PHEMT)] process. The measured results demonstrate the best phase noise of −139.46 dBc/Hz at 1-MHz offset. To the best of our knowledge, this is the lowest phase noise among the reported ones fabricated on-chip with a similar frequency band, and it achieves a wide tuning frequency bandwidth of 21% (2.65–3.27 GHz) with peak figure of merit (FoM) of −192.26 dB and FOM T of −198.8 dB.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-09
Alina C. Bunea; Dan Neculoiu; Antonis Stavrinidis; George Stavrinidis; Athanasios Kostopoulos; Zacharias Chatzopoulos; George Konstantinidis

This letter presents a novel monolithic integrated frequency multiplier circuit for free space power generation in the ${W}$ -band (75–110 GHz). The circuit is based on a submicrometer GaAs Schottky diode monolithically integrated with a slot antenna on a GaAs semi-insulating substrate. The fabricated diode with an air-bridged Schottky contact and a U-shaped ohmic contact showed an ideality factor of about 1.25 and a zero bias cutoff frequency higher than 1.25 THz. Using input signals between 15 and 50 GHz, the free space power generated in the ${W}$ -band corresponding to $\times 2$ , $\times 3$ , $\times 4$ , and $\times 5$ frequency multiplication was measured and showed minimum isotropic conversion losses (with antenna) of 11.5, 16.9, 23.7, and 26.4 dB, respectively.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-11-28
Liang Chen; Lei Zhang; Yan Wang

This letter presents a novel compact power amplifier (PA) using the transformer-based quadrature coupler as the power splitter and combiner to achieve a large output power and high gain for automotive radar application. Compared with conventional transmission-line-based power splitter and combiner, the transformer-based quadrature coupler offers a low loss, wide bandwidth, and compact footprint. As a proof of concept, a 77-GHz PA is designed and implemented in a 65-nm CMOS technology. The measured small-signal power gain is 26.4 dB with a 8.5-GHz 3-dB bandwidth from 74 to 82.5 GHz. The measured $P_{\text {sat}}$ , OP 1 dB , and peak power added efficiency (PAE) are 15.82, 11.5 dBm, and 15.9%, respectively. In addition, the saturated output power at 77 GHz is 16.5 dBm at −40 °C and still remains as high as 13.5 dBm at 130 °C, which enables the automotive application. The proposed PA occupies a core area of $270\,\,\mu \text{m}\,\,\times 530\,\,\mu \text{m}$ and the total dc power consumption is 240 mW.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-09
Zhijun Liu; Xin Hu; Ting Liu; Xiuhua Li; Weidong Wang; Fadhel M. Ghannouchi

The behavior models based on artificial neural networks (ANNs) have been widely used in the wideband power amplifier (PA). However, the selected terms of the input signal significantly affect the complexity of the ANNs. In this letter, a method using an attention-based deep neural network (DNN) is proposed to reduce the number of selected input terms for PA modeling. This method first selects the input terms with large contributions to PA modeling offline using the DNN with an attention mechanism. Then, the selected input items are injected into the DNN to build the PA model online. Experimental results show that the proposed method requiring only 1/3 of the input items can achieve good modeling performance with low complexity.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-11-28
Paolo Valerio Testa; Corrado Carta; Frank Ellinger

This letter presents a vector-modulator phase shifter for low-power and broadband applications operating from 160 to 190 GHz. The component is implemented in a 130-nm SiGe BiCMOS technology featuring a maximum oscillation frequency of 450 GHz. Phase-control methods, inductive peaking, and circuit architecture minimize both the dissipated power ( $P~_{\text {dc}}$ ) for a given insertion loss (IL) and the silicon footprint of the component. A 360° control of the insertion phase is demonstrated for a root-mean-square (rms) IL of 5.5 dB, and a maximum rms error of 1 dB, when the power consumption is 12.4 mW. The core area of the circuit is 0.07 mm 2 . To the best knowledge of the authors, the presented solution achieves the smallest core area together with one of the lowest power consumptions for comparable IL among designs operating above 100 GHz in any fabrication process.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-09
Kyung-Sik Choi; Keun-Mok Kim; Su-Bin Kim; Byeong-Hun Yun; Jinho Ko; Jusung Kim; Sang-Gug Lee

A 915-MHz binary frequency-shift keying (BFSK) transmitter is proposed in this letter. The proposed transmitter architecture allows relaxing the frequency-tuning requirement of the conventional Internet of Things transceiver by the frequency-tripling signal-path topology. The tuning-range requirement is significantly improved down to 4% with the proposed signaling scheme, and this results in the ultralow-power synthesizer implementation. The proposed frequency tripler provides good spur rejection performance, and the adoption of a class-D switching power amplifier (PA) further improves the efficiency of the BFSK transmitter. Implemented in a 55-nm CMOS technology, the proposed transmitter achieves the output power of 5.5 dBm and 31.9% efficiency with only $207~\mu \text{W}$ of power consumption from the synthesizer.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-11-20
Wonho Lee; Songcheol Hong

This letter proposes a compact 28-GHz front-end (FE) structure that uses a common-gate (CG) low-noise amplifier (LNA) as a transmit/receive switch. The power amplifier (PA) output shares a dc bias with the CG LNA input. When the shared dc bias is high, the state of the LNA becomes passive, and the LNA operates as a turned-off shunt switch in the transmitter (TX) mode. The proposed CG LNA switch allows high isolation and linearity with a TX path insertion loss of 0.07 dB at 28 GHz. On the contrary, when the shared dc bias is low, the state of the PA becomes passive and it results in a receiver (RX) path insertion loss of 0.51 dB at 28 GHz. The path losses of the CG LNA switch are minimized by the RF floating bodies of the PA and the CG LNA. This is implemented in a 65-nm CMOS process occupying a 0.215-mm 2 core area. The measured saturation power is 15.3 dBm with 25.1% peak power-added efficiency in the TX mode, and the measured noise figure is 4.9 dB in the RX mode.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-11-28
Cuiping Yu; Ke Tang; Yuanan Liu

In this letter, an adaptive basis direct learning (DL) method was proposed for the linearization of power amplifiers (PAs). The proposed method can reduce the complexity and improve the stability performance of DL digital predistortion (DPD) structure. The experimental results show that the proposed method is more stable and can achieve improvement in normalized mean square error (NMSE) and adjacent channel power ratios (ACPRs) compared with the DL. In addition, the proposed method reduces the number of coefficients by 87%.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-16
Pei Jia; Fei You; Songbai He

An improved reconfigurable Doherty power amplifier (DPA) structure with extended bandwidth is presented. A traditional DPA structure is often used to expand the output power back-off (OBO) range by using three transistors, and the peaking amplifiers work in the same frequency band. In this modified structure, the carrier amplifier works in the whole frequency band of $f_{1}$ – $f_{3}$ , and two peaking amplifiers work in $f_{1}$ – $f_{2}$ and $f_{2}$ – $f_{3}$ , respectively ( $f_{1} < f_{2} < f_{3}$ ). In addition, switches are applied in power divider and power combining networks in order to switch peaking amplifier between frequency bands. A 1.8–3.4-GHz DPA has been demonstrated utilizing such a modified structure, and the frequency band is divided into two parts, which are 1.8–2.7 GHz and 2.7–3.4 GHz. The measured results show that 7.2–11.2 dB of saturated gain, 42.2–43.9 dBm of peaking output power, 45%–62.3% and 36.7%–48.5% of drain efficiency at peaking power levels and 6-dB OBO are delivered.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-09
Gwangsik Cho; Jinseok Park; Songcheol Hong

This letter presents a three-stage differential power amplifier (PA) with an adaptive built-in linearizer (ABL) that achieves an enhanced AM–AM linearity. Series inductors are introduced at cascode internodes to improve the output matching conditions of the cascode amplifiers and stabilize a high-gain PA operation. Capacitors at the gate in the common-gate amplifiers at the power stage are used to achieve high differential gain by reducing RF coupling at the virtual ground and equalizing the drain-source voltage swings. Broad-side coupled transmission line transformers are used for all matching networks. It has 25.5-dB peak power gain and 12.2-dBm saturation output power at 110 GHz with 3-dB bandwidth of 92.5 and 117 GHz. It has a core chip size of 0.76 mm 2 and a peak power-added efficiency (PAE) of 8.5%.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-04
Xiaoming Liu; Jing Jin; Jijian Shi; Jianjun Zhou

A comparator offset immune and area-efficient In-phase and Quadrature (I/Q) mismatch calibration technique is proposed for direct conversion receivers in the letter. Theoretical analysis is provided to explain the independence between comparator offset and error detection accuracy. For verifying the proposed method, a receiver front-end prototype, along with the proposed I/Q mismatch calibration, is designed and fabricated in the 0.18- $\mu \text{m}$ technology. Experimental results show that Image Rejection Ratio (IRR) is 61.99 dB @15 MHz with a comparator offset ranging from 0 to 14 mV. And IRR for a wideband signal from 5 to 25 MHz is enhanced from 31.6 to 43.3 dB after calibration.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-09
Xiaoming Chen; Wei Xue; Hongyu Shi; Jianjia Yi; Wei E. I. Sha

Previous studies on orbital angular momentum (OAM) communication mainly considered line-of-sight (LOS) environments. In this letter, however, it is found that OAM communication with high-order modulation can be achieved in highly reverberant environments by combining the OAM multiplexing with a spatial equalizer. The OAM multiplexing exhibits comparable performance of the conventional multiple-input–multiple-output (MIMO) system.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-20
Eduardo Moctezuma-Pascual; Gabriela Méndez-Jerónimo; Zail O. Rodríguez-Moré; Humberto Lobato-Morales; Reydezel Torres-Torres

This letter presents a parameter extraction methodology for implementing the Debye model to represent the complex permittivity of liquids at microwave frequencies. Thus, based on an electrical circuit analogy, the parameters associated with different model’s poles as well as with the low-frequency loss are straightforwardly determined through linear regressions. Excellent model–experiment agreement is achieved up to 15 GHz for four different liquid samples.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-12-10
Anton Schlegel; Sean M. Ellison; Jeffrey A. Nanzer

Many modern and emerging applications; including sensor networks, Internet of Things (IoT), industrial process monitoring, and distributed phased arrays, among others; require high-accuracy localization. Achieving submillimeter accuracy requires wideband waveforms, typically linear frequency-modulated or spread-spectrum waveforms, which limits the use of low-cost commodity hardware such as software-defined radios, which have limited instantaneous bandwidths. In this letter, we demonstrate a novel approach to high-accuracy localization using spectrally sparse waveforms and a dual-channel microwave sensor. We use a dual-tone waveform with low-bandwidth pulse modulation, where each tone is generated and received by a separate transceiver on the two-channel sensor. The individual tones may be separated by any bandwidth up to the operational limitations of the system for increased localization accuracy, while using instantaneously narrowband signals on each channel. We demonstrate localization accuracy of $530~\mu \text{m}$ with tone separations of 450 MHz on a 2-GHz carrier frequency.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-07-19
Myun-Joo Park

In the title paper, the authors proposed the model of the directional coupler using electrical balance based on a pair of coupled lines and presented its analysis. It is shown that the proposed equivalent circuit is incomplete without additional transmission line sections, and the analysis based on it cannot justify the claimed coupler performance or the design equations. A correct circuit model and the design equations are presented for the proposed coupler.

更新日期：2020-01-10
• IEEE Microw. Wirel. Compon. Lett. (IF 2.374) Pub Date : 2019-11-26
Abhishek Kumar; Sankaran Aniruddhan; Radha Krishna Ganti

The theory presented by Kumar et al. is based on the assumption that edge-coupled transmission lines (TLs) have infinite even-mode characteristic impedance and is clearly mentioned. Simulation is done to show that better than 10 dB matching can be achieved with a practical TL without using additional TL sections as long as impedance transformed by the even-mode of TL is much lower than the port impedance. The addition of extra quarter-wave TL sections can further improve the matching.

更新日期：2020-01-10
Contents have been reproduced by permission of the publishers.

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