Ka-Band GaN HEMT Phase Shifter With T-Type Structure for Beamforming Applications

We designed a 6-bit Ka-band gallium nitride (GaN) phase shifter (PS). A low-pass
$T$
-type network was adopted for all bits constituting the PS to suppress the increase in size. The bandwidth of the entire PS was determined by the bandwidth of 90° and 180° bits. Instead, bits lower than 90° bit were designed to suppress loss as much as possible within a range that does not affect the entire bandwidth. To this end, the size of the series transistors constituting the low bits was increased to reduce the ON-resistance. Furthermore, the increased parasitic capacitance of the transistor reduced the required inductance, further reducing the area. The PS was designed using the 150-nm GaN HEMT process. The core size was
$3.65\times0.79$
mm2. At the frequency ranges of 36–39 GHz, the insertion loss and rms magnitude error were measured to be lower than 8.68 and 0.62 dB, respectively.