Multi-beam spatio-spectral beamforming receiver for wideband phased arrays

This paper reports the first analog integrated spatio-spectral beamforming front-end. The proposed front-end allows for accurate beam steering of signals with large fractional bandwidths, thus minimizing beam squinting, and simultaneous and independent steering of multi-carrier signals. Different spatio-spectral beamforming strategies are discussed and compared. As a proof of concept, an 8 GHz 2-channel, 4-frequency phased-array beamformer is designed and implemented in 65 nm CMOS. The IF signal on each channel is frequency split using an all passive 4-point analog FFT. The orthogonal frequency outputs are then beam-steered using an all passive I-Q vector-combiner. The RF circuit draws 22.8 mA from a 1.2 V supply while the analog baseband consumes 135 μ W at 120 MS/s (9 pJ/conv.).