A K- to Ka-Band Broadband Doubly Balanced Monolithic Ring Mixer

A broadband doubly balanced monolithic ring mixer with a new intermediate frequency (IF) signal extraction method implemented by 0.15 mum pHEMT process is presented. The hybrid couplers of the proposed mixer consist of multiple coupled lines and fourfold coupled line Marchand baluns. The use of multiple coupled lines leads to a die size less than 1 times 1 mm² and improves the bandwidth of the mixer. The novel fourfold coupled line allows the extraction of the IF signal directly without any extra low pass filter circuits. The mixer exhibited 8-13 dB conversion loss, high radio frequency/local oscillation isolation of 35-50 dB over 16-40 GHz and an input 1-dB compression point of 14 dBm.