A Compact 275–320-GHz Reflection-Type Phase Shifter

This letter presents a WR-3.4-band reflection-type phase shifter (RTPS) in a 250-nm InP double heterojunction bipolar transistor (DHBT) technology. A reflective load with an L-section network is implemented using a diode-connected transistor, a transmission line, and a shunt capacitor. The reference impedance of the reflective load is set to a low impedance of 30
$\Omega $
, thus leading to a low-loss variation over a wide operating bandwidth. To minimize the chip area, a quadrature hybrid for combining reflected signals is implemented using a compact broadside coupled-line coupler. The measurement shows that the RTPS provides a continuous 180° phase shift with an average insertion loss of 9.9–10.9 dB over a frequency range from 275 to 320 GHz. The loss variation is only 1 dB. The root-mean-squared (RMS) amplitude and phase errors maintain below 2.9 dB and 7.3°, respectively. The chip size including all probing pads is as small as
$0.37\times0.46$
mm
²
, and the core size is only 0.02 mm
²
. The dc power consumption is zero.