A 6-18 GHz low-profile double-podal corrugated Vivaldi antenna with enhanced gain and polarization purity for defence system applications

A low profile double podal corrugated Vivaldi antenna operating in the frequency band of 6-18 GHz is proposed in this paper, where high gain and low cross-polarization are critical requirements. The proposed antenna employs a pair of uncombined corrugated slanted-edge radiating flares on the top and combined dual podal flares on the bottom side of the substrate, which acts as a ground plane. The combined flares can generate a symmetric current of almost equal magnitude and out of phase, resulting in a significant reduction in cross polarization. An equivalent RLC circuit model is developed and simulated in ADS software to comprehend the physical mechanism of the antenna. For further verification, a prototype is fabricated and experimentally characterized. Good agreement is observed between the simulated and measured results. The measured results demonstrate a -10 dB impedance bandwidth of 11.4 GHz from 6.2 to 17.6 GHz and a maximum inter-port insertion loss of -30 dB at 16 GHz. Subsequently, the measured average cross-polarization levels of -30 dB and -26 dB are achieved in the E-and H-planes, respectively, at a typical frequency of 12 GHz. A maximum gain of 13 dB along the boresight at 18 GHz is also realized.