Research On Microwave And Millimeter Wave Mixing Technology

In modern microwave and millimeter-wave communication system,mixer is the core device of transmitting and receiving system.Its superior performance can not only improve the performance of the whole system,but also reduces the cost of signal source and improves the integration density of the system.The research of millimeter wave mixing technology plays an important role in the development of millimeter wave application system.In this paper,three mixers are developed based on three mixing modes: fundamental mixing,even harmonic mixing and odd harmonic mixing.The advantages and disadvantages of the three mixing modes are compared.Firstly,a UWB dual balanced fundamental mixer with fixed IF frequency in microwave band and a second harmonic mixer with fixed IF frequency in full Ka band are studied.This mixer has a fixed IF frequency.In the secondary frequency conversion superheterodyne receiver system,the fixed low IF frequency can reduce the difficulty of secondary down conversion design and simplify the system structure.Then a kind of W band third harmonic mixer is studied,which not only solves the difficulty of obtaining local oscillator source caused by the second harmonic mixing of W band,but also avoids the deterioration of frequency conversion loss caused by the high harmonic mixing.In order to improve the simulation accuracy and circuit performance,the physical structure and processing technology of planar Schottky diode were studied in the process of mixer design.The nonlinear equivalent circuit model and three-dimensional electromagnetic model of the diode were established,and their accuracy was verified.In order to meet the requirements of miniaturization and integration,the transition structures from guided wave systems to microstrip lines are studied,including Waveguide-microstrip probe transition,waveguide-suspended microstrip single-sided finline transition and substrate integrated waveguide-microstrip transition.In order to satisfy the degree of separation between ports and improve the quality of IF extraction signal,low-pass filters with different structures are studied and CMRC wide-band low-pass filters are selected finally.Then the ADS-HFSS field-circuit simulation method is used to simulate the harmonics of the mixer.The final test results show that the simulation method has high accuracy and can effectively predict the device performance.The test results show that the relative bandwidth of UWB dual-balanced fundamental mixer is 109%,the frequency conversion loss is less than 11 dB,and the isolation of three ports is greater than 10 dB,which is in good agreement with the simulation results.The RF frequency of Ka-band sub-harmonic mixer covers the whole Ka band,and the frequency conversion loss is less than 9.5 dB,and the isolation of three ports is greater than 25 dB,which is also in good agreement with the simulation results.The frequency conversion loss of W-band third harmonic mixer is about 12.5+2dB within 92-96 GHz,the frequency conversion loss is less than 13 dB at most frequency points,and the isolation of IF-LO port is greater than 29 dB,which can effectively avoid the leakage of local oscillator energy.