用于毫米波谐波混频器本振端口的带通滤波器设计

Band Pass Filter Design for Local Oscillator Port of Millimeter Wave Harmonic Mixer

毫米波接收系统设计中,由于高频率的本振源获取难度大且成本高,因此毫米波频段的接收信号主要与本振信号的高次谐波分量而非本振信号进行混频,来获得基带信号。为保证本振信号及其谐波信号的质量,必须在混频器的本振端口加入滤波器,对其基本要求是通带宽、频率选择性好、变频损耗低。首先基于先进设计系统(advanced design systems,ADS)软件设计了一个用于Ka波段四次谐波混频器本振端的平行耦合带通滤波器,其中心频率为8. 5 GHz,通带宽2 GHz。然后用高频结构仿真(high frequency structures simulator,HFSS)软件进行了仿真验证,分析了基板厚度、铜箔厚度、介电常数对滤波器性能的影响。最后,对滤波器进行了加工与测试,将实际测试结果和HFSS仿真结果对比,发现两者基本一致,滤波器性能符合通带带宽、插入损耗和带外抑制的要求。

In a millimeter wave receiving system design,since the local oscillator source is difficult to obtain and the cost is high,the received signal in the millimeter wave band is mainly mixed with the higher order harmonic component of the local oscillator signal instead of the local oscillator signal to obtain the baseband signal.In order to ensure the quality of the local oscillator and its harmonic signal,it is necessary to add a filter to the local oscillator port of the mixer.Its basic requirements are the pass bandwidth,good frequency selectivity,and low conversion loss.A parallel-coupled band-pass filter for the local oscillator end of the Ka-band fourth harmonic mixer is designed based on advanced design systems(ADS)software.The center frequency is8.5GHz and the pass bandwidth is2GHz.Then,it was validated with high frequency structures simulator(HFSS)software,and the effects of substrate thickness,copper thickness and dielectric constant on the filter performance were analyzed in detail.Finally,the filter was processed and tested,and the actual test results were compared with the HFSS simulation results.It was found that they are basically the same,and the filter performance meets the requirements of pass-band bandwidth,insertion loss and out-of-band suppression.