Ambiguity Resolution in Amplitude-Comparison-Based Monopulse Direction-Finding Antenna Systems

In this letter, the use of orthogonal switched beams at θ = ±20° is proposed to improve the robustness against angle-of-arrival ambiguities in amplitude-comparison monopulse systems compared with the conventional use of only sum (Σ) and difference (Δ) patterns. As monotonic behavior of monopulse function inside the given field-of-view causes angular ambiguity, so such false detection can be mitigated while analyzing the echo signal through additional switched beams. Theoretical and experimental results using a corporate-fed 1 × 2 patch array antenna integrated with 3 dB/180° and 3 dB/90° hybrid couplers, which synthesizes a sum, difference patterns, and two orthogonal switched beams (θ = ±20°) at 3 GHz, endorse this improvement. The proposed antenna system can also find applications in sequential-lobing-based direction-finding systems.