Analysis of Broadband Psi (Ψ)-Shaped Microstrip Antennas

Abstract

A new Ψ -shaped microstrip antenna is reported, which increased the bandwidth of the E-shaped microstrip antenna by cutting an additional pair of slots on the other radiating edge of the E-shaped patch. The Ψ -shaped patch yielded a bandwidth of nearly 60% at a center frequency of around 5500 MHz. It gave a maximum gain of more than 10 dBi, which reduced to less than 4 dBi towards the higher frequencies of the bandwidth. In this paper, the broadband responses of the E-shaped and the reported Ψ -shaped patches are studied. In the E-shaped patch, the pair of rectangular slots did not introduce any mode, but modified the TM₂₀ mode's resonance frequency of the patch and, along with the fundamental TM₀₁ mode, resulted in the broadband response. Furthermore, when an additional pair of slots were cut to realize the Ψ -shaped patch, they modified the higher-order TM₂₁ mode's resonance frequency of the patch. Along with the modified TM₂₀ and TM₀₁ modes, this yielded a larger bandwidth. Since the TM₂₁ mode was present towards the higher frequencies of the bandwidth, the gain was reduced to less than 4 dBi. Furthermore, a proximity-fed design of a Ψ -shaped microstrip antenna in the same frequency band was proposed. The proposed configuration gave a higher bandwidth compared to the reported Ψ -shaped patch, with better gain characteristics over the bandwidth. A proximity-fed design of the Ψ -shaped patch in the 1000 MHz frequency band was also proposed. It gave a bandwidth of more than 50% with a broadside radiation pattern, and a gain of more than 8 dBi over the complete bandwidth.