An impedance transformer (IT) with wideband and high selectivity is presented in this paper. Three transmission poles were obtained within the passband and provides a wide passband response. Moreover, there are two transmission zeros (TZs) close to the passband that were achieved by a shunt parallel coupled line and provide high selectivity. For validation of proposed circuit, the ITs were designed at a center frequency (f₀) of 3.5 GHz using an impedance‐transforming ratio (r) of 5 and 10. For r = 5, |S₂₁| and |S₁₁| are 0.36 dB and 28 dB at f₀, respectively. Within the passband, |S₂₁| and |S₁₁| are better than 0.65 dB and 18 dB, respectively. The TZs at 2.65 GHz (0.76f₀) and 1.22f₀, close to the passband, were measured with attenuation better than 37 dB. The out‐of‐band attenuations are higher than 20 dB from DC to 2.77 GHz of the lower stopband and from 4.16 GHz to 9.73 GHz of the higher stopband. For r = 10, |S₂₁| = −1.4 dB and |S₁₁| = −23 dB were measured at f₀. An 18 dB return loss was obtained from 3.415 GHz to 3.694 GHz (FBW = 7.96%).

中文翻译：

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高选择性和宽带带通滤波阻抗变压器

本文提出了一种具有宽带和高选择性的阻抗变换器。通带内获得了三个传输极，并提供了宽通带响应。此外，通过并联并联耦合线获得的通带附近有两个传输零（TZ），并且具有很高的选择性。对于提出的电路的验证，的ITs在中心频率被设计（˚F ₀）的3.5 GHz的使用阻抗变换比（[R 5）和10为- [R = 5，| S ₂₁ | 和 S ₁₁ | 在f ₀分别为0.36 dB和28 dB 。在通带内，| S ₂₁ | 和S ₁₁ | 分别优于0.65 dB和18 dB。测量了通带附近的2.65 GHz（0.76 f ₀）和1.22 f ₀处的TZ，其衰减优于37 dB。从DC到较低阻带的2.77 GHz和从较高阻带的4.16 GHz到9.73 GHz，带外衰减高于20 dB。对于r = 10，| S ₂₁ | = −1.4 dB和| S ₁₁ | 在f ₀处测量到＝ -23dB 。从3.415 GHz到3.694 GHz获得了18 dB的回波损耗（FBW = 7.96％）。