A Fully-Passive 4-Channel RF Beamformer with Ultra-Low Insertion Loss at 12GHz X/Ku-Band for Low-Power Applications in 28nm CMOS

Current methods of radio frequency (RF) beamforming require significant power, making them impractical for power-constrained applications. An ultra-low loss fully-passive, 4-channel, 12GHz, RF beamforming IC with passive loss of 5.4dB is presented. This is more than 3dB better than similar state-of-the-art beamformers. The IC utilizes series-combined antenna elements with transmission-line transformers for power combining and balanced impedance phase shifters for ultra-low loss phase shifting. The implemented circuit allows for a passive design with wide scan angle, ±55°, large fractional bandwidth of 30%, and high linearity >+ 16dBm. Since the RF beamformer has sub-6dB of passive losses and high linearity it can be used as a front-end circuit, on the antenna node, to realize system-level improvements in spatial filtering and array gains without power-intensive pre-amplification.