K a -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 x 0.79 mm(2). 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.