A Phase Shifter with Integrated PA MMIC for Ka-Band Frequencies

In this paper, we investigate a Ka-band high power reflective-type phase shifter using gallium nitride (GaN) high-electron mobility varactors (HEMVARs). To that end, we use GaN varactors that are optimized for power-handling capability and integrate them with a Lange coupler to form a reflective-type phase shifter (RTPS). Analyzing the phase shifter unit cell, a decade of bandwidth is achievable. The insertion loss ranges below 3 dB while the maximum phase offset generated is between 30° at Ku-band and 7° at the upper end of the Ka-band. By including a buffer amplifier, we compensate the losses of two cascaded RTPS unit cells and measure a median relative 3-dB bandwidth of 23.3 % and positive net gain between 26 GHz and 36 GHz. In 1 dB gain compression, the MMIC delivers an output power of more than 33.9 dBm at 30 GHz. The maximum phase shift the designed MMIC can synthesize is 40° and 28° in the lower and upper range of the Ka-band, respectively. To the best knowledge of the authors, this is the first published Ka-band phase shifter using GaN HEMVARs.