A compact attenuator integrated phase shifter with switchable trimode operations

This article presents a compact attenuator integrated phase shifter with switchable trimode operations. The proposed structure consists of simple reflection-type attenuator and phase shifter with Lange coupler for wideband performance. The reflective circuits for attenuator and phase shifter are implemented with HEMT's and varactor diodes. By separately adjusting the control voltages for attenuator and phase shifter, the designed circuit can operate in trimode: attenuation-mode, phase shift-mode (PS-mode), and loss variation compensated phase shift-mode (LVC-PS-mode). The proposed circuit is implemented in 0.15-μm GaAs low noise pHEMT process and provides the input and output return losses always better than 12 and 15 dB, respectively. Using LVC-PS-mode, the measured maximum phase shifting range of 80° with the measured insertion loss variation within ±0.05 dB from 15 to 25 GHz can be achieved. The chip size of the fabricated core is about 1.5 × 0.65 mm² excluding test pads.