Dual-band Microstrip Patch Antenna with Frequency Tuning Capability Based on Varactor Diode

Featuring independent frequency tuning capabilities for each band on a multiband antenna is quite a challenging task. In this paper, a dual-band microstrip patch antenna, with the ability to tune the resonant frequency in one band while maintaining it in the other band, is proposed. The antenna comprises two main structures arranged in a stack and is responsible for producing two different resonant frequencies. The square microstrip patch located on the top layer plays a role in producing high resonant frequencies, while the square ring element array integrated with varactor diodes in the middle layer plays a role in producing low resonant frequencies and provides a frequency tuning function. The overall dimensions of the antenna are 52 mm×52 mm×3.2 mm, cast on an FR4 Epoxy dielectric substrate with a relative permittivity of 4.4. The characterization results show that the antenna produces two frequency bands, namely 1.7 GHz and 1.975 GHz, where the low-frequency band can be tuned between 1.6 to 1.725 GHz by varying the varactor capacitance value between 0.1 to 7 pF.