Presenting their results at the 2017 IEEE International Solid-State Circuits Conference in a paper titled “A 318-to-370 GHz Standing-Wave 2D Phased Array in 0.13μm BiCMOS”, the researchers disclosed the symmetrical architecture of a millimetre-sized chip able to operate broadband frequency tuning (52 GHz) independently of beam steering over an angle of 128° in the E plane and a maximum beam steering angle of 53° in the H plane.
Built using a 0.13μm SiGe BiCMOS process, the 2×2 array structure consists of four λ-size standing-wave (SW) oscillator unit cells, each made of two half-cell SW oscillators facing each other and coupled together through transmission lines in the collectors and λ/4 lines at the emitters of transistors (see figure 1).
The two half-cells operate out of phase resulting in a virtual ground along the line of symmetry and cancelation of fundamental frequency and other odd harmonics while combing the desired 4th harmonic, the paper reports.
The capacitively degenerated transistor provides a narrow-band negative transconductance that compensates for losses in the circuit and sustains the oscillation in a specific mode. The transistors also act as nonlinear devices to generate the desired 4th harmonics, fed to an onchip patch antenna for radiation.
For their experiment, the chip was simply mounted on a FR4 PCB with the supply, bias, and control voltages all provided through simple bond wires. At 344 GHz, the maximum radiated power reported was -6.8 dBm with a minimum phase noise of -93.1 dBc/Hz.
The chip consumed a total of 310-to-640 mW across the band from a 1.5-V supply.
Joint authors Omeed Momeni and Hossein Jalili concluded their paper by claiming their chip achieved the largest tuning range among fully integrated THz radiators, phased arrays, and oscillators, with the highest operation frequency and the widest beam steering range among fully integrated THz 2D phased arrays. In future work, the authors plans to integrate the chip into imaging and communication systems.
University of California, Davis – www.ucdavis.ed