Design of lowpass microstrip filter using T-shaped and elliptical resonators

Design of lowpass microstrip filter using T-shaped and elliptical resonators

In this paper, a novel design of microstrip lowpass filter has been proposed. T-shaped, modified T-shaped and elliptical resonators have been properly combined to achieve the final structure. The designed filter has a cut-off frequency at 1.643 GHz. The results indicate that the filter has a narrow transition band resulting is a remarkable roll-off rate of 128 dB/ GHz, which is considered as an outstanding achievement. Moreover, the structure benefits from a compact size, approximately 10.2 * 21.4 mm2, which equals to 0.091*0.192 λ^2g. It should be noted that is the guided wavelength at cut-off frequency. Besides, the insertion loss and return loss in the pass band is better that 0.2 and 24 dB, respectively. Finally, the result show that the proposed filter can achieve a figure of merit (FOM) of 24550.