Mixer group delay measurements

Mixers are one of the fundamental components of many receivers and transmitters, especially in the microwave range. Any mixer-based receiving or transmitting system requires that each mixer has well-known amplitude, group delay and phase responses. A linear phase and constant group delay in particular are essential for low bit error rates (BER) during data transmission in wireless and satellite communications systems and for high target resolution for phased array antenna modules in surveillance systems. Some techniques will be introduced and discussed to address the challenging determination of mixer group delay. In particular, several cases will be included: differential and I&Q mixers, as well as mixers with an embedded LO with no common reference frequency signal accessible. Finally, the procedure to measure the group delay of a satellite in orbit will be presented.