Bandwidth Enhancement of Comparator Applied in W-Band Circularly Polarized Monopulse Antenna

In this letter, a novel wideband comparator for W-band circularly polarized (CP) monopulse antenna is proposed and analyzed. The comparator mainly consists of four 3 dB waveguide couplers and a novel wideband phase shifter (PS). The bandwidth of the comparator is greatly enhanced by combining the sequential rotation feeding technique with the wideband PS technique for the first time. To verify its wideband performance, the CP monopulse antenna consisting of the comparator and a 2 × 2 CP horn array is fabricated and measured. The experimental results are in good agreement with the simulation. For the measured sum (Σ) channel, the reflection coefficient lower than −10 dB, the realized gain not less than 11.5 dBi, and the axial ratio better than 0.45 dB are realized in the whole W-band (75–110 GHz). For the measured azimuth and elevation difference (Δ) channels, the null depths of the difference patterns are less than −25.8 dB at 80, 92.5, and 105 GHz, and the difference patterns are symmetrical and stable.