A Fixed-Tuned 85-105 GHz Subharmonic Mixer Using Schottky Diodes

This paper presents the design of a broadband fixed-tuned subharmonic (SHM) mixer at millimeter-wave frequency using commercially available simulators. GaAs based anti-parallel Schottky diode AP1/G2/0P95 from Rutherford Appleton Laboratory having cutoff frequency in THz range is chosen for the mixer design and its physical structure is modelled to reflect the diode parasites. The diode is flipped-chip bonded to quartz substrate for mixing operation. Simulations show that the conversion loss remains within 8 dB over the frequency range 85-105 GHz for an 8 dBm of local oscillator (LO) power with the minimum value of 6.5 dB at 95 GHz. Corresponding measured values are 13.58 and 7.5 dB, respectively. In all the cases, LO frequency is kept fixed at 47 GHz. Thus, the present modeling technique is found to predict well the mixer performance and the developed prototype shows a state-of-the-art performance.