28GHz Active Monopulse Networks with Amplitude and Phase Control and -30dB Null-Bandwidth of 5GHz
This paper presents an active bi-directional monopulse comparator at 28 GHz. The four inputs from the antenna quads are first divided and fed into two 2×2 TRX beamformer chips to perform sum (Σ) or delta (Δ) operation in either azimuth or elevation planes. A symmetrical input and output RF routing with multi-layer crossovers is implemented for wideband performance. The amplitude and phase mismatch due to both on-chip variation and off-chip routing is calibrated out with a single-point calibration at 28 GHz using fine-step VGA and phase shifters (0.2–0.3 dB/step, 5.6°/step). The measured sum (Σ) port gain of 14 dB is achieved with >30 dB null-depths for a 5 GHz instantaneous bandwidth in both planes.