Multi-Beam RF Aperture Using Multiplierless FFT Approximation

Multiple independent radio frequency (RF) beams find applications in communications, radio astronomy, radar, and microwave imaging. An N -point FFT applied spatially across an array of receiver antennas provides N -independent RF beams at N 2 log 2 N multiplier complexity. Here, a low-complexity multiplierless approximation for the 8-point FFT is presented for RF beamforming, using only 26 additions. The algorithm provides eight beams that closely resemble the antenna array patterns of the traditional FFT-based beamformer albeit without using multipliers. The proposed FFT-like algorithm is useful for low-power RF multi-beam receivers; being synthesized in 45 nm CMOS technology at 1.1 V supply, and verified on-chip using a Xilinx Virtex-6 Lx240T FPGA device. The CMOS simulation and FPGA implementation indicate bandwidths of 588 MHz and 369 MHz, respectively, for each of the independent receive-mode RF beams.