A 4-Bit 360o 10 GHz Digitally-Controlled Passive Phase Shifter With Digital Logic Control On-Chip in 0.15 μ m Indium Gallium Arsenide (InGaAs) pHEMT Process

A 4-bit 360 ^o digitally-controlled phase shifter at center frequency ($\mathrm{f}_{\mathrm{o}}$) of 10 GHz (6-18 GHz) in 0.15 $\mu$m pHEMT low noise process (that can be further extended to 5, 6, 7, or 8 bits in the future) is presented in this paper. While digital phase shifters are not unique, what this paper shows is how to implement the phase shifting blocks alongside with its digital control circuitry that a lot of commercial phase shifter of similar genre do not include. Implementing digital control in InGaAs can be problematic. This paper studies, analyzes and implements digital inverters and buffers in InGaAs embedded with the phase shifting blocks. T-bridge topologies were used for the phase shifting blocks of $22.5^{\mathrm{o}}$, $45^{\mathrm{o}}$, $90^{\mathrm{o}}$, and $180^{\mathrm{o}}$ units. The post layout simulation of the full phase shifter had reflection coefficient S 11 & S 22 of 4.5 dB or better, insertion coefficient S 21 & S 12 of 30 dB or better, and a 1-dB compression point of 18 dBm or greater of input power for all frequencies (6-18GHz) and all phase shifting bits (for $0^{\mathrm{o}}$ to $360^{\mathrm{o}}$); which is similar to commercial GaAs phase shifters of today on the market (however they do not employ digital logic and require multiple pads for the on and off bits).