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

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 (1.2 lambda(o)), when conventional waveguides are used. Reducing the element spacing to 0.6 lambda(o) (in the azimuth plane), based on a partial Hplane waveguide, enables a 1D e-scanning range up to 84 degrees (+/-42 degrees) in the azimuth plane perpendicular to the waveguide axis. An active sub-array panel of 8 x 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 copolar 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 x 8 elements) a perfect candidate for high power e-scanned dual-polarized phased array radar for weather observations.