A 45–75 GHz Vector Modulator MMIC With Built-In Voltage Converter

Abstract

This letter presents a 45–75 GHz balanced vector modulator (VM) with a built-in voltage converter for quadrature phase shift keying modulation. With embedded voltage converter, the design becomes less sensitive to threshold voltage variation. The effect of the Lange coupler’s coupling factor and cold FET’s total gate width on wideband symmetry performance of the modulator is investigated. A 30-GHz operation bandwidth centered at 60 GHz is achieved by using a 0.15- $\mu \text{m}$ GaAs pHEMT process. On-wafer measurement results of the VM show that, from 58 to 67 GHz, the amplitude and phase errors are better than ±0.45 dB and ±2°, respectively. Within a wide frequency range of 45–67 GHz, for all modulation states, the amplitude and phase errors are within ±0.9 dB and ±4°, respectively, while the insertion loss is less than 11.5 dB and return loss is better than 10 dB.