Compact rectangular microstrip antenna for conical radiation pattern

Portable communication systems require compact microstrip antennas (MSA). A rectangular MSA (RMSA) with a shorting pin at one of the radiating edges exhibits dual frequency operation with a broadside radiation pattern (see Wong, K.L. et al., Electron. Lett., vol.33, no.8, p.646-7, 1997). A compact MSA with a conical pattern can be realized using an RMSA with shorting pins placed at both the radiating edges (see Srinivasan, V. et al, Microwave Opt. Technol. Lett. vol.24, no.1, p.11-13, 2000). It exhibits dual frequency operation with a conical pattern at f₁ and a broadside pattern at f₂. We have also studied the effect of variation in the spacing between the shorts on resonance frequencies and input impedance. With two opposite corners shorted, a square MSA fed diagonally has triple frequency operation with conical patterns at the lower and higher resonance frequencies, f₁ and f₃, and a broadside pattern at the middle frequency f₂. The resonance frequencies are tunable by changing the spacing between the shorts. Theoretical results for these configurations using the multiport network model (MNM) (see James, J.R. and Hall, P.S., 1989) and the method of moments based IE3D software from Zeland Software Inc are presented.