Multi-beam 4 GHz Microwave Apertures Using Current-Mode DFT Approximation on 65 nm CMOS

TL;DR

This paper presents a novel 65 nm CMOS current-mode design for multi-beam RF aperture synthesis using a simplified DFT approximation, enabling high-bandwidth operation exceeding 4 GHz with multiple simultaneous beams.

Contribution

It introduces a current-mode CMOS approach employing a simple coefficient DFT approximation for efficient multi-beam RF aperture synthesis without phase-shifters.

Findings

Achieves operation up to 4 GHz with 8 independent beams

Uses simple circuitry with coefficients in {0, ±1, ±2}

Demonstrates potential for high-bandwidth multi-beam RF systems

Abstract

A current-mode CMOS design is proposed for realizing receive mode multi-beams in the analog domain using a novel DFT approximation. High-bandwidth CMOS RF transistors are employed in low-voltage current mirrors to achieve bandwidths exceeding 4 GHz with good beam fidelity. Current mirrors realize the coefficients of the considered DFT approximation, which take simple values in $\{0, \pm1, \pm2\}$ only. This allows high bandwidths realizations using simple circuitry without needing phase-shifters or delays. The proposed design is used as a method to efficiently achieve spatial discrete Fourier transform operation across a ULA to obtain multiple simultaneous RF beams. An example using 1.2 V current-mode approximate DFT on 65 nm CMOS, with BSIM4 models from the RF kit, show potential operation up to 4 GHz with eight independent aperture beams.