$K$-Band LTCC Star Mixer With Broadband IF Output Network

This paper presents a hybrid star mixer in a surface-mount package using low-temperature co-fired ceramic technology. The frequency of operation ranges up to 32 GHz for the RF frequency with an achieved conversion loss of as low as 5 dB. The device is optimized for local oscillator (LO) drive levels of down to 7.5 dBm. Various IF output networks with an inherently low series inductance are discussed, offering large IF bandwidths of up to 11.5 GHz with a significant improvement compared to known solutions. Optimization procedures are revealed to achieve higher port isolation and a flat conversion loss function even at low drive levels. Measurements and simulation confirm the design methodologies and approaches.