The more frequently used technique to realize broadband and dual band microstrip antenna is by cutting the slot at an appropriate position inside the patch. In this paper, an in-depth analysis of dual band rectangular slot cut rectangular microstrip antenna and plus shaped slot cut broadband rectangular microstrip antenna is presented. The dual band slot cut antenna is reported to be resonant at 3640 and 4080 MHz. Through the analysis it was observed that the slot modifies the resonance frequencies of TM 11 and TM 02 mode of the rectangular patch and optimizes the impedance at them to realize dual frequency response. Further when an additional horizontal slot is cut inside the above rectangular slot which realizes plus shaped slot, it further reduces TM 02 mode resonance frequency and along with the TM 11 patch mode, yields broadband response. The proposed analysis gives an insight into the functioning of the slot cut patch antennas operating at higher order modes as well as it will help them in designing them in given frequency band.

Broadband suspended microstrip antenna on thicker substrate is realized by using non-contact L-probe feeding technique. The guidelines for selecting total L-probe length are not available in the reported literature. In this paper, an analysis of broadband L-probe fed variations of microstrip antenna like, circular microstrip antenna, annular ring microstrip antenna, rectangular microstrip antenna, E-shaped microstrip antenna and half E-shaped microstrip antenna, is presented. It was observed that, total L-probe feed length nearly equals quarter wavelength at the resonance frequency of equivalent patch. Further using this quarter wavelength approximation, L-probe fed rectangular and circular microstrip antennas were redesigned at different frequencies which results into the broadband response with formation of loop inside the VSWR = 2 circle. The comparison between two non-contact feeding techniques of microstrip antenna, namely proximity feed and L-probe feed is presented. The two have similar performance in terms of bandwidth and radiation pattern, with proximity feeding technique to be the simplest method to be implemented in thicker substrates.