access icon free Design of LPF with UW stopband and sharp roll-off rate using transfer function analysis

A novel microstrip lowpass filter with outstanding features is designed, simulated, fabricated and analysed. The proposed structure has the capability to improve frequency response in transition band and remove the 13th unwanted harmonics in the stopband. The proposed design comprises many resonators and cell attenuators. It features an UW stopband, high suppression factor and high sharp roll-off. To adjust the cut-off frequency, the transfer function and LC equivalent circuit of the main resonator are calculated. Results show that cut-off frequency and relative bandwidth of stopband of the filter are 2 GHz and 171%, respectively. Also, insertion loss <0.11 dB and return loss more than 18 dB have obtained for filter form DC to 2 GHz. The fabricated filter reaches a high figure of merit of 72,093.

Inspec keywords: harmonics suppression; band-stop filters; transfer functions; low-pass filters; UHF filters; resonator filters; microstrip filters; attenuators

Other keywords: LPF; UW stopband sharp roll-off rate; frequency 2 GHz; LC equivalent circuit; cell attenuator; microstrip lowpass filter; 13th unwanted harmonics removal; frequency response; resonator; transfer function analysis

Subjects: Microwave circuits and devices; Passive filters and other passive networks; Waveguide and microwave transmission line components

References

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      • 1. Hongand, J.-S., Lancaster, M.J.: ‘Microstrip filters for RF/microwave application’ (Wiley, New York, NY, USA, 2001).
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http://iet.metastore.ingenta.com/content/journals/10.1049/el.2017.4144
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