Radiation Characteristics of a Multimode Concentric Circular Microstrip Patch Antenna by Controlling Amplitude and Phase of Modes

Conventional method of beam scanning such as phased array antenna is costly by using multiple antenna elements and phase shifters. In this communication, a different method is investigated to achieve beam scanning. A multimode concentric circular microstrip patch antenna on a single substrate layer backed by a finite ground plane is presented where radiation patterns are reconfigurable. Pattern reconfiguration is achieved by exciting higher order TM_n1 modes in addition to the dominant TM₁₁ mode. Next, limited beam scan performance for linear polarization by employing mode combination and control of the amplitude and phase values is demonstrated. A prototype multimode patch antenna was fabricated and experimentally verified for the individual modes impedance matching and radiation patterns which showed acceptable agreement. The beam scan performance for a selected combination of modes of the patch was also measured.