A Consideration on Low Profile Design of a Wideband Ring Microstrip Antenna Fed by an L-probe

This paper presents low profile design of a wideband ring microstrip antenna (MSA) fed by an L-probe. The proposed antenna consists of a ring patch and a feeding L-shaped probe (L-probe) situated beneath the patch. In order to design a wideband MSA fed by an L-probe, a height of approximately 0.1 to 0.15 wavelengths at the center frequency is often needed. In this paper, low profile design of the wideband ring MSA fed by an L-probe with a height of less than 0.1 wavelengths is investigated. The design frequency is at around 0.6 GHz. Air layers are assumed among the patch, the L-probe, and the ground plane. Two designs of the wideband ring MSAs fed by an L-probe with a height of 88 mm and 40 mm are presented by using the electromagnetic simulator Mentor IE3D. The simulated results reveal that 40% and 28% fractional bandwidths of less than −7.4 dB reflection are obtained for the designed MSAs with a height of 88 mm and 40 mm, respectively. It is also confirmed by the simulation that gain of the MSA with a height of 40 mm is larger than that of 88 mm.