A 260GHz broadband source with 1.1mW continuous-wave radiated power and EIRP of 15.7dBm in 65nm CMOS

Abstract

Terahertz spectroscopy using silicon technology is gaining attraction for future portable and affordable material identification equipment. To do this, a broadband THz radiation source is critical. Unfortunately, the bandwidth of the prior CMOS works is not sufficient. In [1], the 300GHz signal source achieves 4.5% tuning range by changing the coupling among multiple oscillators. In [2], the DAR array has 3% tuning range with radiation capability. Alternative to the continuous device-tuning method, THz time-domain spectroscopy utilizing the broadband spectrum of picosecond pulses is widely used in the optics community [3]. In this paper, a high-power pulse-based sub-millimeter-Wave radiation source using 65nm bulk CMOS technology is reported. The architecture of this transmitter is shown in Fig. 8.2.1, where four differential core oscillator pairs are mutually coupled through four quadrature oscillators. Each core oscillator pair generates 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nd</sup> -harmonic signals at 260GHz that are power-combined after radiating through eight on-chip antennas. Four shunt switches, controlled by narrow pulses (width≈45ps) modulate the radiation. The pulses are generated by local digital circuit blocks with programmable repetition rate up to 5GHz. This way, the broadband spectrum of the pulses is upconverted to the carrier frequency of 260GHz. Without modulation, the chip achieves a continuous-wave radiated power of 1.1mW. Under modulation, the measured bandwidth of the source is 24.7GHz, which makes it suitable for many FTIR-based THz spectrometers. In addition, if the switches are modulated by digital data, this chip can also be used as a transmitter for sub-millimeter/THz wireless communications.