Sub-harmonic wireless locking of a THz radiating on-chip source in 65 nm CMOS

A novel method of locking an on-chip J-band radiating source is presented in this paper. The source is based on a fundamental W-band VCO that radiates its J-band 3rd harmonic using an on-chip loop antenna, connected directly to the differential VCO without a buffer. Radiating the chip with a W-band signal using a horn antenna 50 cm away, enables wireless injection locking of the radiating source. The source can be tuned in a wide frequency range of 280 to 294 GHz with peak total radiated power (TRP) of 0.6 mW, EIRP of +7 dBm and DC to THz radiated power efficiency of 3%. With a free-running phase noise of better than -95 dBc/Hz at 10 MHz offset, the locked signal follows the phase noise of the external reference up to a locking range around 80 MHz with -25 dBm of radiated W-band power. This new concept enables simple and cost effective locked CMOS THz source arrays.