Design of a low-noise wideband fixed IF subharmonic mixer at W-band

This paper provides an idea for designing a highly efficient, second-order broadband fixed-IF subharmonic mixer. Attention is paid to the step-by-step design process with detailed fabrication methods. With the purpose to improve the accuracy of simulation, the diode model is separated into the passive (linear) and the active (nonlinear) model. HFSS is utilized for the linear simulation of the mixer model while ADS is utilized for the non-linear simulation of the mixer. A tapered RF probe at the RF port is utilized to achieve wideband performance. The circuit of the presented mixer is printed on the 75 mu m Quartz substrate and mounted in a waveguide block using split block technology. Measured results indicate an admissible conversion loss (better than 10.2 dB) over the RF bandwidth from 84 to 105 GHz. A moderate local oscillator power (9 dBm) is needed for this operation. The proposed mixer circuit is verified by test data. The measured port isolation between LO and RF is at least 36 dB. The least measured value of DSB noise temperature and conversion loss is 845 K and 7.2 dB, respectively at 85.2 GHz. The proposed Anti-parallel diode pair (APDP) based diode mixer shows better LO-RF isolation and conversion loss over other W-band mixers reported to date.