An Ultra-Compact X-Band Dual-Polarized Slotted Waveguide Array Unit Cell for Large E-Scanning Radar Systems

Abstract

A design of an X-band dual-polarization slotted waveguide antenna (SWGA) array for high polarization performance over 200 MHz bandwidth and wide scan in the azimuth plane, ideal for high-power dual-polarized radar system, is presented. The proposed design uses a compact array unit cell where the overall dimensions are reduced to 50% in comparison with that of the dual-polarization slotted waveguide array antenna using the conventional rectangular waveguides. The new design overcomes the fundamental limitation of zero electronically scanning, due to the large element spacing (1.2λ °), when conventional waveguides are used. Reducing the element spacing to 0.6λ ° (in the azimuth plane), based on a partial H-plane waveguide, enables a 1D e-scanning range up to 84°(±42°) in the azimuth plane perpendicular to the waveguide axis. An active sub-array panel of 8× 8 elements, excited with 8 high-power transmit and receive modules, is proposed. This active sub-array can be scaled to obtain a large array without any constraints in size and power. The proposed design uses longitudinal shunt slots on the partial H-plane waveguide for V-polarization antenna and non-inclined edge wall slots on the conventional waveguide for H-polarization antenna. The proposed design offers stable impedance, gain, cross-polarization isolation and excellent co-polar pattern mismatch over the whole frequency band of interest. Having a cross-polarization isolation better than-60 dB and co-polar pattern mismatch around ± 0.12 dB across the scanning range, make this array unit cell (8× 8 elements) a perfect candidate for high power e-scanned dual-polarized phased array radar for weather observations.