Analysis of circularly polarised dual-ring microstrip patch array using hybrid feed

Design and analysis of a series-fed, circularly polarised, dual-ring array using hybrid feed are presented. Two concentric ring subarrays with different element numbers formed by linearly polarised microstrip patches are arranged and energised by a hybrid feed network sequentially to generate circular polarisation (CP). The radiating elements are connected in cascade and fed by non-radiating apertures with power coupled from a lossy feeding circuit. A schematic model is developed for power distribution of the radiating elements in the array so that each will receive identical amount of power, which is essential to produce CP waves. This model can be applied on various types of series-fed arrays using non-resonant feeds as long as the power coupling mechanism is formed. The proposed design is validated through measured data, which demonstrated good CP quality, well-defined radiation patterns and moderately high gain.