毫米波宽带高中频单平衡混频器设计与实现

Design and implementation of millimeter-wave broadband high-IF single balanced mixer

摘要:

针对毫米波宽带通信、雷达和测试仪器领域的应用需求，提出一种E波段宽带高中频(IF)单平衡混频器。射频(RF)及本振(LO)信号通过多分支宽带加宽波导正交耦合器输入，通过鳍线过渡结构将信号从波导传输模式过渡到微带模式，并提供宽带中频信号及直流接地回路；中频输出低通滤波器可有效抑制LO及RF信号，并为其提供等效接地回路。利用肖特基二极管的非线性实现混频，并通过微带匹配电路最终实现宽带低损耗混频效果。混频器采用57.6、62.4、67.2 GHz 3个点频本振，将67~85 GHz的射频信号分段下变频至9.4~17.8 GHz的中频范围内。测试结果表明，在67~85 GHz射频频率范围内，射频输入功率为-15 dBm，本振输入功率为12 dBm时，混频器变频损耗为7.1~10.1 dB，对组合杂散的抑制在36 dBc以上。

Abstract:

The E-band broadband high-Intermediate Frequency(IF) single balanced mixer is proposed to meet the demand of the communication, radar and test instruments in the millimeter-wave broadband field. The Radio Frequency(RF) and Local Oscillator(LO) signals are input through the multi-branch broadband broadened waveguide quadrature coupler. The signal is transitioned from the waveguide transmission mode to the microstrip mode through the grounding fin transition structure, providing a broadband IF signal loop and DC grounding. The IF output low-pass filter can effectively suppress the LO and RF signals and provide an equivalent grounding circuit for them. The mixer employs the nonlinearity of the Schottky barrier diode to achieve mixing, and ultimately achieves a wideband low-loss mixing effect through the microstrip matching circuits. The mixer utilizes three LO frequencies of 57.6 GHz, 62.4 GHz, and 67.2 GHz to segmentally down-convert the RF signal within the range of 67~ 85 GHz to the IF range of 9.4~17.8 GHz. The test results indicate that within the 67~85 GHz RF range, when the RF input power is -15 dBm and the LO input power is 12 dBm, the frequency conversion loss of the mixer is 7.1~10.1 dB, and the undesired mixing product rejection is above 36 dBc.