Design and Implementation of a Miniaturized Filtering Antenna for 5G Mid-Band Applications

Abstract

Combining a microwave filter with an antenna results in a low-cost, efficient, and small-size selective radiator called a filtering antenna or filtenna. In this work, a compact filtering antenna is presented to radiate within the 5G mid-band frequencies along (3.6–3.8 GHz) with strong rejection for the frequencies outside this range. The proposed filtering antenna consists of a crescent-shaped planar monopole antenna that is electromagnetically coupled with a reduced-size capacitively loaded loop (CLL) microwave band-pass filter. The miniaturization of CLL is achieved by utilizing a single ring CLL structure instead of two rings to reduce the filter size to half without affecting the filter performance. The filtering antenna in this work is fabricated on a Rogers RT5880 substrate with dimensions equal to 24.2 × 27 × 0.8 mm3. Good congruence between the measurements and the simulation results, and both verify the antenna’s perfect operation along the 5G mid-band frequency range. The simulated and measured peak realized gain values of the proposed structure are 2.24 dB and 2.2 dB, respectively. Furthermore, the power pattern of the designed filtering antenna is omnidirectional, which is very convenient for portable 5G mid-band devices. Compared to other works, it is found that in spite of the small dimensions of the filtering antenna (24.2 × 27 × 0.8 mm3), the antenna has a bandwidth that covers the range 3.6–3.82 GHz with a maximum gain value equal to 2.2 GHz and omnidirectional pattern which makes the antenna very suitable for 5G mid-band applications.