Sidelobe Reduction of TM12 Mode of Circular Patch via Nonresonant Narrow Slot

A technique to reduce the E-plane sidelobe of the TM
¹²
mode of circular microstrip patch is presented. It involves the use of a single nonresonant narrow slot embedded at the patch center. The fundamental working principle is the linear superposition of the radiated field by the patch and the embedded slot. The sidelobe level (SLL) and the peak gain are found to be dependent on the slot length. Effects of various design parameters like slot length, dielectric constant and substrate thickness on SLL and peak gain are investigated. Measurements results are provided to confirm these findings. In addition to this, to show the merit and utilization of the proposed technique, a novel single layer, easy to design and fabricate high gain circular microstrip antenna configuration is also proposed. It is a simple slot loaded circular patch having a peak gain ~ 11 dBi with SLL as low as -20 dB. Depending upon the substrate parameters, peak gains as large as 13 dBi can be attained.