A Tapered Matching Transformer Integrated Sequential Phase Feed Network for Circular Polarization Array Antenna

This work proposes a sequential phase (SP) feed network with a tapered transformer, and a prototype is realized and tested. The proposed feed network comprises one input and four outputs with a sequential quadrature phase shifting. The measured results exhibit an excellent 6-dB transmission coefficient with a maximum deviation of ±1.6 dB and phase difference between two progressive ports with a maximum deviation of ±2.23° at 4.41 GHz and a wide 10-dB bandwidth of 4 GHz. Within the operating band of 3.06 GHz to 7 GHz, output ports exhibit equitable power distribution with a maximal deviation confined to ±2.6 dB. Hence, the proposed SP feed network is suitable for feeding sequentially placed radiating elements of an antenna array to generate circular polarization with broad axial ratio bandwidth.