A Bidirectional High-Gain Cascaded Ring Antenna for Communication in Coal Mine

In this letter, a bidirectional high-gain antenna is proposed for wireless communication in tunnels or coal mines. The antenna consists of six rectangular rings in cascade and works in a standing-wave mode. The high-gain bidirectional radiation property is realized by the currents distributed in-phase on the vertical edges. The dimensions of the proposed ring are 300 × 16 × 0.6 mm³ (2.4λ × 0.128λ × 0.005λ at 2.4 GHz). The measured -10-dB bandwidth is approximately 290 MHz (2.33-2.62 GHz), the measured peak gain is 9.5 dBi, and the 1-dB gain bandwidth is about 110 MHz (2.34-2.45 GHz). The experimental results are presented and discussed, and it is shown that the proposed bidirectional antenna inherits the merits of high directional radiation gain, low profile, easy fabrication, and low wind resistance.