Abstract: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. In this paper, 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 is 8.5 GHz and the pass bandwidth is 2 GHz. Then, it was validated with 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 High Frequency Structures Simulator(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.