Broadband Digital Amplitude and Phase Control MMICs

This paper will describe the design, implementation and measured performance of broadband digital amplitude and phase control MMICs. It will also describe the design of a broadband, high isolation Single Pole Double Throw (SPDT) switch, which was a key building block used in both designs. The MMICs to be presented are a 0.5GHz-18GHz 5-bit Digitally Controlled Attenuator (DCA) and a 8GHz-12GHz 5-bit Digitally controlled Phase Shifter (DPS). Both MMICs were realized on a commercially available 0.15 mum pHEMT process from WIN Semiconductor. GaAs pHEMT processes have become the industry choice for the realization of high linearity RF switches. Fig la is a photograph of the fabricated pHEMT SPDT test structure, which is similar to the SPDT used in both MMICs. Fig lb shows the measured results for the SPDT. The paper will describe the requirements, design, layout and measured performance (first tape out) of both the 5-bit DCA (Fig. 2a & 2b) and the 5-bit DPS (Fig. 3a &3b).