Wideband Dipole Array with Balanced Wideband Impedance Transformer (BWIT)

Abstract

Within the context of modern digital phased array (DPA) radios, differential Radio Frequency (RF) front-ends provide much greater immunity to noise and distortion by suppressing second order harmonics. Recent advancements in differential RF front-ends offer high dynamic range, high linearity, and low noise in the transceiver chain. However, a major roadblock to fully differential systems is the presence of common-mode resonances. In this article, we present a novel wideband differential feed for dipole arrays that overcomes this bottleneck. Our dipole array is developed for the L-S band (viz. 1.05 GHz to 3.2 GHz) with emphasis on dual-linear polarization and resonance-free scanning to low angles. The novelty of this article is the Balanced Wideband Impedance Transformer (BWIT) feed that mitigates common-mode currents across the entire band while scanning to low angles. Array simulations are verified with measurements of an 8× 8 prototype in a volume of 384mm × 384 mm × 57 mm. The array achieves resonance-free scanning across a 3:1 impedance bandwidth with VSWR < 3 for the cases of θ = 0(Broadside), 45° (D-plane), 60° (E-plane) and across a 2.37:1 impedance bandwidth with VSWR < 3 for the case of 45° (H-plane). Measured gain achieves near-theoretical values across the operating band.