A ku-band distributed SPDT switch in 0.5 μm AlGaN/GaN HEMT technology

In this paper, a wideband single-pole double-throw (SPDT) switch using the traveling-wave concept was demonstrated. Realized in 0.5 mu m AlGaN/GaN HEMT process, it achieves good performance at Ku-band despite the process being intended for low-frequency applications. This type of switch combined the off-state shunt transistors and series coplanar waveguide (CPW) lines to form an artificial transmission line. CPW is also used to eliminate parasitics associated with through-substrate microstrip vias and coupling of adjacent transmission lines. An accurate switch HEMT model was extracted and used in the design. A 9-25 GHz single-pole double-throw (SPDT) switch in conjunction with quarter-wavelength impedance transformers demonstrates an insertion loss of less than 6 dB, return loss better than 10 dB and an isolation of better than 25 dB.