Small scale lowpass and quad-band bandpass filter for 5G application

This work offers a new small-scaled lowpass and quad-band passband filter with low insertion loss and high selectivity. By integrating a shorted interdigital capacitor (IDC), closed ring resonator, meander line, and rectangular-shaped virtual ground plane, better impedance matching and transmission properties have been attained. Initially, the lowpass response structure comprises shorted IDC and closed ring resonators. Further utilizing pairs of meander lines and rectangular stubs on both sides of ring resonators, a quad bandpass along with a lowpass filter was constructed. Excluding the fifty-ohm feedline the proposed filter area measures only 0.04λ_g × 0.06λ_g (15.6 mm×24.6 mm) at the lowpass frequency of 3dB cutoff, 0.75 GHz. The fractional bandwidth at 3-dB of the proposed four passband zones are 63.76% (1.39-2.78 GHz), 22.55% (3.26-4.09 GHz), 17.15% (4.42-5.24 GHz), and 4.3% (5.64-5.89 GHz) at operating frequencies of 02.18, 3.68, 4.78 and 5.82 GHz, respectively. Moreover, the resonance frequencies of each band can be adjusted by altering the structural parameters of the intended filter, which results in modifications to their relative lumped parameters. By doing experimental measurements that correlate with simulated ones, the suggested filter is validated. The designed filter may be useful for 5G communication frequency range-1 (FR1), 0.45-6.0 GHz bands.