While eliminating any RF or IF phase shifting or combining, this array architecture simplifies scaling to a larger number of nodes.
Silicon devices continue to shrink and, in doing so, become more suitable for applications in bio-medical devices. Examples include large-array, low-power ultrasonic imagers as well as lab-on-chip devices for rapid pathogen detection and DNA sequencing. In addition, diagnostic medical imaging can benefit from the continual cost reduction and/or miniaturization of silicon devices. To leverage silicon’s evolution, a group of researchers recently focused on pulsed-radar technology that can enable the dielectric measurement of tissue for imaging. In this scalable array architecture for three-dimensional (3D) imaging, multiple single-element phase-coherent-transceiver (TRX) chips (which boast programmable transmit pulse-delay capability) are mounted on a common printed-circuit board (PCB) to realize the array.
To enable this transmit chip, an integrated, 94-GHz phase-coherent pulsed radar with on-chip antennas was designed by Amin Arbabian and Mustafa Rangwala from Stanford University together with Steven Callender, Shinwon Kang, and Ali M. Niknejad from the University of California at Berkeley. The transceiver chip achieves a 10-GHz frequency-tuning range and 300 ps of contiguous pulse position control, which paves the way for its use in a large-array imager with time-domain transmit beamforming. That phase-coherent transceiver can transmit and receive pulses as narrow as 36 ps, which translates to 30 GHz of bandwidth. According to interferometric measurements, it can attain single-target range resolution beyond 375 μm. Delay measurements show that the time of RMS error would be less than 1.3 ps. See “A 94 GHz mm-Wave-to-Baseband Pulsed-Radar Transceiver with Applications in Imaging and Gesture Recognition,” IEEE Journal Of Solid-State Circuits, April 2013, p. 1055.