应用于混合频率综合器的耦合微带线带通滤波器

Coupling microstrip line bandpass filter applied to hybrid frequency synthesizers

设计了一种应用在PLL+DDS环外混频混合频率综合器系统末端的平行耦合微带线带通滤波器,用于抑制频率综合器输出频谱中的杂散和谐波分量。带通滤波器采用平行耦合微带线形式,实现了中心频率2 350 MHz,带宽50 MHz,带内最大损耗为-5 dB,带外在2 225 MHz损耗为-47.7 dB、在2 285 MHz损耗为-29.0 dB的指标。通过对此滤波器及此混合频率综合器输出信号的测试,验证了滤波器可以有效抑制此结构的频率综合器输出频谱中的杂散和谐波分量。

This paper designs a parallel coupled microstrip bandpass filter at the ends of the hybrid frequency synthesizer of PLL+DDS mixing in the outside of the feedback loop systems.This filter is used to suppress the frequency synthesizer′s spurs and harmonic in the output spectrum.The band pass filter is designed by the parallel coupled microstrip line.The measuring results show the center frequency is 2 350 MHz and the bandwidth is 50 MHz.And the maximum loss is-5 dB in the passband.In the external bandpass,the loss of 2 200 MHz is-47.7 dB,while at the 2 285 MHz,the loss is-29.0 dB.By measuring the filter and the output signals of the hybrid frequency synthesizer,it is proved the effectivity of the filter to suppress spurs and harmonic in the output spectrum of the frequency synthesizer.