A 122 GHz Sub-Harmonic Mixer With a Modified APDP Topology for IC Integration

This letter presents a modified passive subharmonic mixer (SHM) topology based on an anti-parallel-diode-pair (APDP). It features a differential intermediate frequency output facilitating IC integration and improving common-mode noise rejection. An example 122 GHz SHM has been designed and tested in a 0.13 μm SiGe BiCMOS technology for a 122 GHz radar IC. SiGe HBT transistors have been diode-connected to form the APDP. The example SHM exhibits a conversion loss of 8 dB with a 5 dBm LO pumping power. The measured bandwidth extends from 117 to 124 GHz, adequately covering the 122-123 GHz ISM band, while the input 1 dB compression point and noise figure were measured to be -5 dBm and 8.5 dB respectively. Due to its superior 1/f noise performance and high linearity, the mixer is especially well suited to zero intermediate frequency radars.