Abstract:
Bidirectional gain of a wide rectangular slot antenna resonating over the 6 − 8.5 GHz band is enhanced by loading a pair of conducting sheets on the ground plane edges. These sheets are vertically loaded with respect to the slot antenna for meeting two purposes – (i) to appropriately converge the oblique radiation of the slot towards the broadside direction for enhanced gain and (ii) to retain the original impedance band (reflection coefficient ≤ −10 dB) of the slot by avoiding the formation of a resonant cavity (as in the case of superstrate loaded antennas). Optimized antenna using FR-4 substrate of side 50 mm has an overall size of 2.2λ0 × 1.2λ0 × 0.5λ0, where λ0 is the free-space wavelength at the mid-band frequency of the operating band. Measurements of fabricated antenna prototype demonstrate an impedance band of 5.97–8.53 GHz with bidirectional radiation pattern, with peak in-band gain of 5.52 dBi. The average gain improvement in the band is 3.99 dB, relative to the wide-slot antenna without sheet loading. The main attraction of the proposed method is its non-resonant nature, which enables almost uniform gain enhancement throughout the original impedance band, with bidirectional radiation pattern.