Broadband microwave mixer mounted on suspended line baluns

The performance of a microwave balanced mixer which is mounted on the suspended microstrip baluns is investigated. The mixer is in the conventional double-balanced ring form and the two ports (RF and IF) are terminated by the same real impedance (50 ohms). The pump power requirements for to provide matching at either ports is investigated and the conversion losses are calculated. A new type of balun is proposed for RF port termination which is consist of a normal microstrip and a phase inverting suspended microstrip line. It is shown that this balun theoretically has infinite bandwidth when the odd-order characteristic impedance of the suspended line Y_oo=2Y₀. The mid frequency of operation is selected as 10 GHz and the bandwidth of about 2 octave (3-12 GHz) with less than 8 dB loss (6 dB measured at 9 GHz)