Varying a supply voltage using a DC-to-DC converter can significantly improve the efficiency of RF power amplifiers (PAs) for low-power RF transceivers. However, intrinsic switching noise from a conventional DC-to-DC converter operating in fixed Pulse-Width Modulation (PWM) can affect the system performance since the spectral components in the switching noise are confined in the fundamental switching frequency and its harmonics. This harmonic noise will have detrimental effects on the performance of the microwatt’s transmitter due to its low output power. Especially for microwatts systems, the minimized size of the inductor will increase the spurious noise due to increased peak-to-peak inductor current. By relocating the spurious noise and reducing peak noise from a switching converter, this paper proposes the technique to prevent high noise spurs in a microwatt transmitter, combining both pseudo-random frequency stepping and monotonic frequency stepping. Both modulation circuits are implemented in CMOS 0.18 µm process and incorporated to achieve the proposed DC-to-DC converter system. The measurement results indicate that the proposed PWM ramp signal modulator with random frequency modulation in a DC-to-DC converter can reduce the peak of the spurious noise-power by 22 dB. Monotonic frequency modulation with various frequency steps reduces the peak of the spurious noise-power by 18 dB.

使用DC-DC转换器改变电源电压可以显着提高用于低功率RF收发器的RF功率放大器（PA）的效率。但是，由于工作在固定脉冲宽度调制（PWM）中的常规DC-DC转换器的固有开关噪声会影响系统性能，因为开关噪声中的频谱分量仅限于基本开关频率及其谐波。由于其低输出功率，此谐波噪声将对微瓦变送器的性能产生不利影响。特别是对于微瓦系统，由于峰峰值电感电流增加，电感的最小尺寸将增加寄生噪声。通过重新定位杂散噪声并降低开关转换器的峰值噪声，本文结合伪随机频率步进和单调频率步进，提出了一种防止微瓦发射机中高噪声杂散的技术。两种调制电路均采用0.18 µm CMOS CMOS工艺实现，并结合在一起以实现所提出的DC-DC转换器系统。测量结果表明，所提出的在DC-DC转换器中具有随机频率调制的PWM斜坡信号调制器可以将杂散噪声功率的峰值降低22 dB。具有不同频率步长的单调频率调制可将杂散噪声功率的峰值降低18 dB。测量结果表明，所提出的在DC-DC转换器中具有随机频率调制的PWM斜坡信号调制器可以将杂散噪声功率的峰值降低22 dB。具有不同频率步长的单调频率调制可将杂散噪声功率的峰值降低18 dB。测量结果表明，所提出的在DC-DC转换器中具有随机频率调制的PWM斜坡信号调制器可以将杂散噪声功率的峰值降低22 dB。具有不同频率步长的单调频率调制可将杂散噪声功率的峰值降低18 dB。