A New Class of Planar Ultrawideband Modular Antenna Arrays With Improved Bandwidth

The theory, design, fabrication, and measurement of a new class of planar ultrawideband modular antenna (PUMA) arrays are presented. The proposed PUMA array class achieves twice the bandwidth (from 3: 1 to 6: 1) of the conventional shorted via-based PUMA without using an external matching network and while retaining convenient unbalanced feeding, manufacturing, and assembly characteristics. The chief enabling technical innovation hinges upon the reconfiguration of shorting vias into capacitively-loaded vias that simultaneously: 1) mitigate low-frequency bandwidth-limiting loop modes and 2) shift problematic common-mode resonances out-of-band. A simple theoretical model based on ridged waveguides is proposed that qualitatively and quantitatively explains this novel common-mode mitigation. An infinite array operating over 3.53-21.2 GHz (6: 1) is designed to achieve active VSWR < {2, 2.5, 3.8} while scanning to {broadside, 45 degrees, 60 degrees}, respectively, without oversampling the aperture. D-plane cross-polarization is around {-15, -10} dB for {45 degrees, 60 degrees} scans with high efficiency, i.e., 0.5 dB co-polarized gain loss on average. A dual-polarized prototype 256-port (128 elements per polarization) array is fabricated and measured having good agreement with full-wave finite array simulations.