V-band Broadband Harmonic Mixer

With a frequency range from50to75GHz,V-band millimeter-wave is not an atmospheric window,which attenuats quickly when propagated in the air.However it becomes an advantage,when used in space communication from satellite to satellite,no interference source from the earth matters.So,V-band millimeter-wave is now used in inter-satellite links,and draw much attention in recent years.It is a challenge to provide a high-quality local oscillator in V-band frequency,as it is difficult and costy to realize such an oscillator.Harmonic mixer technology only needs a oscillator with a frequency of1/2,1/4even1/8of the RF frequency,which will be widly used.In this paper,the anti-parallel Schottky diode pair,which is the nonlinear parts of the V-band millimeter-wave mixer,is analysised in detail.In the V-band,the diode package parasitics of Schottky diode has an significant effect on the performance of the mixer,in the design,VDI’s first anti-parallel Schottky diode pair is used,the parameters of which is simulated. With the consideration of the impact of package parasitics,an accurate ADS circuit model of the diode pair is constructed.As to the circuit degien,each passive part is built and simulated in Ansoft dimensional electromagnetic simulation software HFSS,these passive components are,a waveguide to microstrip transition structure for the RF input signal,a step impedance low-pass filter between LO and RF signal,a low pass filter for the IF signal and a diplexer for the LO signal.Then the whole circuit is built in ADS,and co-simulated with the passive part resulted from HFSS,the final result meets the required technical requirements, then make the text of its physical.The proposed V-band sub-harmonic mixer in this paper,has the advantage of low conversion loss,wide frequency band,and perfect flatness,when compared with other sub-harmonic mixer of the same frequency range reported before.The simulation result shows,a best conversion loss of about5.6dB,a conversion loss less than7.8dB in the entire passband,and a flatness of about2.2dB,the result is ideal.Its physical test and simulation results are consistent,the conversion loss is about8.5dB in the entire passband, and grows in the high frequency.Design has an important practical significance in the engineering application of V-band millimeter-wave system.