A Mixed-Signal Vector Modulator for Eigenbeamforming Receivers

Analog vector modulators used in eigenbeamforming receivers usually include radio-frequency (RF) variable-gain amplifiers (VGAs) to modulate both the magnitude and the phase of receiving signals. The strenuous linearity requirement of RF VGAs makes it unsuitable to be realized in CMOS. This paper applies the mathematical concept of overcomplete expansion and coarse quantization to replace the VGAs with simple switches. The operation of these switches are controlled by an algorithm running in the digital domain. The proposed mixed-signal architecture thus shifts most of the system complexity from the analog domain to the digital domain. It will be shown that this architecture scales well with CMOS technology.