Simultaneous spatial and frequency-domain filtering at the antenna inputs achieving up to +10dBm out-of-band/beam P_1dB

Abstract

Multi-antenna transceivers with beam-forming are recently gaining interest for low GHz frequencies (<;6GHz) [1-4]. In the antenna beam, (phase-shifted) signals from multiple antennas add constructively, improving SNR, while out-of-beam signals add destructively (i.e. spatial filtering). Usually the summation point is behind some gain blocks, which then need to be capable of handling strong signals. To improve the input-referred compression point P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1dB</sub> , a fully passive switched-capacitor approach was presented in [4], providing P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1dB</sub> =+2dBm, but at a high noise penalty: NF=18dB. Here we propose to sum immediately at the baseband capacitors of passive mixer-first switched-RC downconverters. We show that this can render a direction-dependent RF impedance (spatial filtering) together with RF bandpass frequency filtering at lower noise and higher P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1dB</sub> .