摘要:
功率放大器(power amplifiers, PAs)会对输入的宽带线性调频信号(linear frequency modulated, LFM)引入幅度失真和相位失真,这将导致接收机脉冲压缩处理后的输出信号主瓣展宽,旁瓣电平抬高,从而恶化雷达距离分辨率甚至产生虚假目标。文中提出采用有限冲击响应滤波器(finite impulse response, FIR)模型对宽带LFM信号激励下的功放进行行为建模和数字预失真(digital predistortion, DPD)补偿。利用宽带测试平台对500 MHz 瞬时带宽LFM信号激励下峰值功率15 W 的S波段功放进行验证。实验结果表明,浅饱和和深饱和情况下FIR模型都能准确建模功放的失真特性,浅饱和情况下DPD能够补偿幅度失真和相位失真,而深饱和情况下只能补偿相位失真,经过DPD补偿脉冲压缩后的峰值旁瓣电平都明显降低。
Abstract:
Power amplifiers (PAs) introduce amplitude and phase distortions to wideband linear frequency modulated (LFM) signals, which increases the main lobe width and side lobe level after pulse compression at the receiver side, deteriorating radar range resolution or even generating fake objects. This paper proposes using a finite impulse response (FIR) filter model for behavioral modeling and digital predistortion (DPD) for PAs with wideband LFM signal excitation. A wideband test bench is set up to validate the FIR model for a 15 W S-band PA excited by an LFM signal with 500 MHz instantaneous band-width. Experimental results demonstrate that the FIR model can accurately characterize distortion behaviors when the PA operates in weakly nonlinear regions and strong saturation conditions. Both amplitude and phase distortions are compensated for PAs operating in weakly nonlinear regions after DPD, whereas only phase distortion is compensated for PAs operating in strong saturation conditions. Peak side lobe levels after pulse compression are greatly reduced in both cases after DPD.
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