K-band LTCC star mixer with broadband IF output network

This paper presents a hybrid star mixer in a surface mount package. The frequency of operation ranges from 14 GHz to 27 GHz with an achieved conversion loss of as low as 8 dB. The device is optimized for local oscillator drive levels of down to 7.5 dBm. A focus is set on the design of the passive structures, especially the balance of the Marchand balun. An IF output network with an inherently low series inductance is introduced, offering larger IF bandwidths compared to known solutions. The mixer was fabricated as a surface mount device in LTCC technology. Measurements confirm the design methodology and show good agreement with the simulation results.