Design of Wideband Multi-Ring Microstrip Antennas Fed by an L-Probe for Single-Band and Dual-Band Operations

This paper presents design of a wideband multi-ring microstrip antenna fed by an L-probe for single-band and dual-band operations. The proposed antenna consists of one or two square ring patches and an L-probe arranged in a multilayered dielectric substrate. By using a thick substrate for the L-probe and optimizing distances between the L-probe and the patches, wideband performance can be obtained. Prototype antennas for single-band and dual-band operations are fabricated and tested. Measured fractional reflection bandwidths less than -10 dB are 46.1% for the single-band antenna and 20.3% and 15.7% for the dual-band antenna, respectively. Measured gains of the test antennas in the above bandwidths are 0 to 6.9 dBi for the single-band antenna and 3.0 to 8.6 dBi for the dual-band antenna, respectively. Although the E-plane radiation pattern is slightly tilted against the frequency, stable broadside radiation is confirmed. The proposed antennas exhibit excellent performance as wideband planar antennas for single-band and dual-band operations. The proposed wideband antenna can be easily extended to a dual linearly-polarized antenna by using another L-probe at the orthogonal position.