Wideband Circularly Polarized Array Using Tightly Coupled Dipole Array Theory

Circularly polarized transceivers have shown superior characteristics over linearly polarized ones for space-to-ground communications. Specially, unlike linearly polarized (LP) waves that undergo Faraday rotation through the ionosphere, circularly polarized (CP) waves reduce Faraday rotation and cloud interference effects. Hence, wideband circularly polarized phased arrays are attractive for high-resolution spaceborne radars, especially at lower frequencies. For example, radar resolutions down to 1 meter require at least 150 MHz of bandwidth, viz. 150 MHz-300 MHz operation. Unfortunately, conventional wide-scanning CP phased arrays exhibit narrow-band axial ratio < 3 dB performance.