Demonstration of a Ku-Band N-Path Downconverter in GaN-on-SiC

This paper presents a Ku-band, interference tolerant downconverter based on N-path passive mixers implemented in GaN-on-SiC process. The mixer-first topology employs sinusoidal quadrature LO, but includes a transformer-based splitter between I and Q mixers to reduce loss due to LO overlap in the mixers. At 17 GHz, the circuit achieves a measured in-band conversion loss of 9.5dB, out-of-band blocker-induced input 1-dB gain compression (OOB B1dB) of 10.4 dBm and input third-order intercept point (OOB IIP3) of 21.8 dBm. The chip takes in 11 dBm of LO input power which translates to a competitive linear efficiency of 10.8 dB. The downconverter maintains its loss and linearity properties across 15.5-18.5 GHz. The chip's integrated LO buffers consume 32 mA at 8 V supply and occupies 2.06mm x 1.26mm die area only. To the best of authors' knowledge, this is the first demonstration of N-path passive mixers in GaN technology in RF/mmWave frequencies.