A 38 to 44GHz sub-harmonic balanced HBT mixer with integrated miniature spiral type marchand balun

This work presents an active balanced sub-harmonic mixer (SHM) using InP double heterojunction bipolar transistor technology (DHBT) for Q-band applications. A miniature spiral type Marchand balun with five added capacitances for improved control of amplitude and phase balance is integrated with the SHM. The measured results for the SHM demonstrates a conversion gain of 1.2 dB at an RF frequency of 41 GHz with an associated LO power of 5 dBm. The conversion loss remains better than 3 dB from 38 to 44 GHz. The LO to IF isolation is better than 42 dB within the bandwidth of the mixer and confirms the excellent balance of the integrated spiral type Marchand balun. The DC power consumption of the SHM is only 22.5 mW under normal mixer operation.