Hybrid coupled compact variations of rectangular microstrip antennas

Microstrip antennas (MSA) have several advantages, such as, lightweight, small volume and low profile planar configuration. Their main disadvantage is small VSWR bandwidth. Also, the size of a /spl lambda//2 length rectangular MSA (RMSA) is large for operation in the UHF frequency range. The size of the MSA has been reduced by using shorting posts or by cutting slots. The resonant frequency of the RMSA reduces by a factor of 3 to 4 when a single shorting post is loaded either in the middle of its edge or at its corner, but the bandwidth of the shorted RMSA is small. The configurations obtained by cutting slots in the RMSA, such as, rectangular ring, H and C shaped MSAs give the reduction in the operating frequency with the reduced bandwidth. In this paper, several hybrid coupled compact variations of RMSA have been proposed to yield broad bandwidth.