Frequency Reconfigurable Transmit Array Antenna for X band Applications

Abstract

The increasing demand for high-gain, frequency-reconfigurable, and compact antennas has driven the development of advanced antenna architectures for next-generation communication systems. This paper presents a new frequency-reconfigurable transmitarray (TA) for X-band applications based on the integration of a Frequency Selective Surface (FSS) superstrate with a multi-layer TA employing double square-loop elements. Frequency reconfigurability is achieved by varying the unit-cell structural strip length, (str_l), from 3.0 mm to 4.2 mm, resulting in five distinct operating states (TA-state-1 to TA-state-5). The proposed design enables systematic tuning of the operating frequency from 8.5 GHz to 11.2 GHz, corresponding to a wide frequency switching range of 22.5%. A prototype of the proposed TA was fabricated and experimentally characterized. Measured results show good agreement with simulations, demonstrating a maximum peak gain of 17.2 dBi and a radiation efficiency of 92% (-0.36 dB) at 9.9 GHz (TA-state-3), while maintaining a low insertion loss of approximately 1 dB. The proposed low-profile architecture offers an effective solution for frequency-agile and multi-band communication systems, providing a favorable trade-off between frequency tuning range, efficiency, and structural simplicity.