Wideband Dual Circularly Polarized Helical Antenna Array for Satellite Applications

A novel wideband dual-sense circularly polarized (CP) helical array antenna with enhanced isolation is proposed in this letter. The left-handed CP (LHCP) radiation and the right-handed CP (RHCP) radiation in the same band are realized by exciting two concentric helical antennas with different radii and winding directions. The parameters of the two concentric helical antennas are studied to keep them operate in the same frequency range while maintaining good CPs performance. To achieve a high isolation between the two nested helical antennas, the parameters, such as the number of turns, pitches, and offset rotation angles of the two helical antennas, are studied. Then, a 2 × 2 dual-sense CP helical array antenna is developed by applying two sequentially rotated microstrip feeding networks on the same plane. To alleviate the congestion, the two feeding networks with 90° and 270° phase gradients are placed concentrically to excite RHCP and LHCP radiations, respectively. The dual-sense CP helical array antenna is prototyped and verified experimentally. The measured results agree well with the simulations, showing a wide overlapped impedance/3 dB-AR bandwidth from 3.7 GHz to 5.0 GHz [fractional bandwidth (FBW) = 30%] for both polarizations. The isolation is better than 22 dB over the frequency range.