Design, optimization and realization of compact bandpass filter using two identical square open-loop resonators for wireless communications systems

In wireless communications systems, the microstrip filter has an important job in terms of selectivity and elimination of the undesired signals. Microstrip filters are always preferred over the lumped filters at a larger frequency for their compact size, lighter weight, lower cost, and higher performance. In this paper, the design, optimization, and realization of a compact narrow-band bandpass filter using two identical square open-loop resonators is presented for a frequency of 2.4 GHz.This filter is printed on a RO6010 substrate with a dielectric constant of 10.2, a thickness of 1.27 mm and a tangent loss of 0.0023. The proposed filter is intended for wireless communications systems such as (RFID, Wi-Fi, Bluetooth, and WLAN) and medical applications systems that operate at the resonance frequency of 2.4 GHz. This bandpass filter has very high selectivity in the bandwidth of 290 MHz, the small size of (9.4 x 23.1) mm(2), and small insertion loss of -0.23 dB. The proposed filter structure is easy to fabricate and the achieved results are very encouraging.