Özet:

In microwave systems, frequency tunable planar antennas have become common place as it is increasingly difficult to cover all the necessary frequency bands required. These antennas are low profile, conformable to planar and nonplanar surfaces, simple and inexpensive to manufacture using modern printed-circuit technology. The work presented in this paper proposes a electronically reconfigurable planar antenna by using only one varactor diode. Varactor diode from Skyworks Solutions Inc. (SVM1251) has been used as tuning element. It provides a tunable capacitance range from 53.65 to 2.79 pF with reverse voltages varying between 0 and 8 V. A 50 Ohm resistor as dummy load, and two 68 pF SMD capacitors are incorporated within the structure in order to protect the DC supply to Network Vector Analyzer from dc current, in addition to having an effect on the size reduction. Proposed antenna operate frequency between 400 MHz and 1116 MHz that include ultra-high frequency (UHF) for radio frequency identification (RFID) and Global Systems for Mobile Communications (GSM) applications. Proposed compact antenna having the overall physical size of 8 mm x 8 mm (0.0203λ x 0.0203 λ) is numerically modeled on FR4 substrate having loss tangent, dielectric constant and height of 0.025, 4.3, and 1.61 mm respectively in the CST Microwave Studio numerical calculation program over the frequency range from 300 MHz to 1.5 GHz. The proposed electrically tunable directional antenna has better return loss level higher than 25 dB with reduced size with novel geometrical structure in the operating frequency between 400 to 1116 MHz.

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