Probe-fed circularly polarised monopulse radial line slot antenna

The design and performance of an annular slot planar circularly polarised array which generates sum or difference far-field patterns for monopulse tracking applications is described. The array consists of a radial waveguide the radiating elements of which consist of crossed slots designed to radiate right-hand circular polarisation in the frequency range 10.2 to 10.8 GHz. Sum and difference patterns are obtained by using a very simple phasing circuit. At 10.4 GHz the gain of the sum pattern is 12.3 dBi and the in the difference pattern is 28 dB at boresight.