High efficiency 293 GHz radiating source in 65 nm CMOS

This letter presents a J-band radiating source (284-301 GHz) based on a differential Colpitts oscillator with an on-chip antenna in 65 nm CMOS. The source radiates the third harmonic of the oscillation frequency, which is also generated in the voltage controlled oscillator (VCO) itself due to its large voltage signal. An integrated loop antenna serves also as the load inductance at the drains of the VCO transistors, acting as a choke at the fundamental and matched antenna at the third harmonic. The antenna has a directivity above +9 dBi across the tuning range. This frequency source has a DC-to-RF radiated power efficiency of 2.8%, a radiated power of -2.7 dBm and an EIRP of +6.4 dBm, taking a silicon area of only 0.26 mm².