Lensless Short-Range Reflection-Mode Imaging at 275 GHz Using CMOS Concurrent Transceivers

Lensless short-range reflection-mode imaging through a cardboard cover is demonstrated at 275 GHz using a pair of concurrent complimentary metal–oxide–semiconductor transceiver pixels separated by ∼5 mm on a printed circuit board (PCB). This is the first such demonstration at frequencies above 100 GHz. The separation between the imaged object and pixels is ∼1 cm and the operation at 275 GHz allows the lateral resolution to be reduced to ∼2 mm due to a smaller wavelength. A concurrent transceiver pixel incorporating a transmitter with an effective isotropic radiated power of −18.9 dBm and a receiver with a double sideband noise figure of ∼51 dB in an area of 0.45 × 0.49 mm² is used. The reflected signals from a target must be greater than the transmitted signal directly coupled to the receiver, and this isolation between the transmitter and receiver limits the imager range and contrast. Full-wave electromagnetic simulations (ANSYS high-frequency structure simulator (HFSS)) of a PCB with a transmit and receive rectangular patch antenna with a separation of ∼5 mm show that ∼65 dB isolation at 275 GHz can be achieved. This should be sufficient to image a target with a radar cross section of 2 mm × 2 mm with a reflection coefficient of 0.1 that is 1-cm away. This work points to a path for incorporation of millimeter and submillimeter wave imaging in a handheld device.