A μ negative metamaterial using spiral resonator (SR) with an electromagnetically coupled (EMC) feeding system is proposed as a novel antenna structure. The proposed antenna is designed and fabricated on a FR4 dielectric substrate with a thickness of 1.6 mm and relative permittivity of 4.0 to achieve its radiation characteristic. The antenna is operated at frequency 2.4 GHz. To improve the antenna gain, a matching circuit is inserted into the feed line. The µnegative metamaterial is achieved by using a spiral resonator with spiral numbers N = 3, 5, 7, and 10. It is found that the negative imaginary part tends to shift leftward as the value of N increases. The simulation result of the proposed antenna structure with spiral number N = 3, strip width w = 3.1 mm, and gap width s = 0.5 mm provides the best performance with S11 = -15 dB, VSWR < 2 bandwidth of 30 MHz and gain of –0.5 dB at frequency of 2.43 GHz. The proposed antenna with matching circuit provides the antenna gain of 2.21 dB, which is better than that without the matching circuit. The dimensions of the proposed antenna are reduced by 53% compared with those of the conventional patch. Both the simulation and measurement results of the radiation characteristics of the proposed antenna show good agreement.
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