A 239–281GHz Sub-THz imager with 100MHz resolution by CMOS direct-conversion receiver with on-chip circular-polarized SIW antenna

A 239-281GHz imager by direct-conversion receiver is demonstrated in 65nm CMOS process with high spectrum resolution and high sensitivity for sub-THz imaging. The sub-THz imager consists of a circular-polarized substrate integrated waveguide (SIW) antenna, down-conversion mixer and power gain amplifier (PGA). The SIW antenna is compact in area of 0.17mm² with -0.5dB gain and 32.1GHz bandwidth. The single-gate mixer can achieve 80GHz bandwidth centered at 260GHz with a conversion gain of -19dB. High resolution signal detection is achieved by a three-stage PGA with 150MHz bandwidth. The proposed sub-THz imager is fabricated with measurement results: -2dBi conversion gain over 42GHz bandwidth, -54.4dBm sensitivity with 100MHz detection resolution bandwidth, 6.6mW power consumption and 0.99mm² chip area. Moreover, frequency-dependent sub-THz images are demonstrated as well.