A 28-GHz Low-Power Vector-Sum Phase Shifter Using Biphase Modulator and Current Reused Technique

In this letter, we present a low-power vector-sum phase shifter for upcoming 5G communication at 28 GHz. The ±I/±Q signals for phase synthesis by vector adder (VA) are generated by a 90° coupler and two reflection-type biphase modulators. Modulators are only biased at 0 and 1.8 V to avoid large insertion loss near their phase reversal region. Our proposed single-ended two branches quadrature structure can avoid the differential variable gain amplifier and achieve low power and compact area. In addition, we use the current reused technique to connect VA and output buffer to save dc power and suppress a change in output impedance among different phase states. The measured average peak gain is -3.75 dB at 29.25 GHz. Across all phase states, the measured IP1 dB is better than 5 dBm. The 3-dB bandwidth of S
₂₁
is 27-33 GHz. Input and output return losses are also better than 10 dB at this frequency range. Total dc power consumption is only 6.6 mW for 1.8 V supplied voltage. To the best of our best knowledge, this phase shifter has low dc power and compact area at K-band and Ka-band.