A W-band broadband single balanced mixer using an improved 180-degree hybrid

In this paper, an improved wideband millimeter-wave 180 degrees hybrid is proposed and a novel W-band broadband single balanced mixer based on the new hybrid is presented. The proposed hybrid consists of a standard waveguide to suspended coplanar waveguide (SCPW) transition and a SCPW to suspended stripline transition. According to the inherent electromagnetic field characteristics of the two transitions, the proposed hybrid achieves good performances of broadband phase, power distribution and isolation. The simulated insertion losses of the two transitions and the isolation between the two signal input ports are better than 0.1 dB and 54 dB respectively. A single balanced mixer based on the proposed hybrid has been designed and fabricated at W-band. The measured single-sideband (SSB) conversion loss is less than 9.5 dB for the radio frequency (RF) range from 80 to 108 GHz. And the best SSB conversion loss of 5.8 dB is achieved with RF of 104 GHz. Moreover, the local oscillator (LO)-RF isolation is more than 30 dB over the overall W-band. The results show that the fabricated mixer has the advantages of broad bandwidth, low conversion loss, and good isolation.