Design of Balanced Mixer with 180 Degrees Hybrid Network Based on Cruciform Coupler

Abstract

In this paper, the balanced mixer with 180 degrees hybrid network is proposed at Q-band. The hybrid network is achieved by cruciform directional coupler on SIW and a 90 degrees delay microstrip line. Based on this structure, the isolation and conversion bandwidth of mixer has been improved significantly. Finally, the measurement indicates that mixer's center frequency is 33 GHz, conversion loss bandwidth (15 dB) is 3.3 GHz and the peak amplitude is 9.3 dB (at 32.75 GHz), isolation between RF and LO greater than 15 dB. Meanwhile, the mixer has acceptable linearity that IP1dB is nearly 4.8 dBm.