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Design and implementation of miniaturized tri-band microwave bandpass filter

Ponnammal P. (Department of Electronics and Communication Engineering, SRM Institute of Science and Technology, Kattankulathur, India)
Manjula J. (Department of Electronics and Communication Engineering, SRM Institute of Science and Technology, Kattankulathur, India)

Microelectronics International

ISSN: 1356-5362

Article publication date: 10 May 2022

Issue publication date: 17 May 2022




This paper is aimed to study the design of a miniaturized filter with tri-band characteristics. In this paper, perturbation is used to realize circuit miniaturization and multi-band by exploiting the inductive property. During this process, vias are added for twofold benefit, namely, circuit miniaturization and enhanced frequency selectivity at high frequency. Thus, with the introduction of the shorting via, the single-band dual-mode bandpass filter is converted into a tri-band filter with a smaller electrical size.


This paper presents the design and characterization of a miniaturized two-port filter with tri-band operating characteristics. The proposed filter is constructed using a square patch resonator operating at 5.2 GHz with a capacitively coupled feed configuration. A square perturbation is added to the corner of the square patch to achieve diagonal symmetry and to excite dual mode. The perturbation offers a sharp transmission zero defining bandwidth of the proposed filter. In addition, a shorting post is introduced to achieve an 88% size reduction by lowering the operating frequency to 1.8 GHz.


The prototype filter has insertion less than 1.2 dB and return loss better than 12 dB throughout all the realized frequency bands. The prototype filter is fabricated and the simulation results are validated using experimental measurements. The realized fractional bandwidths of the proposed bandpass filter are 11/5.6/1 at 1.8/4.6/5.85 GHz, respectively. The quality factor of the proposed antenna is greater than 80 and a peak Q-factor of 387 is realized at 5.85 GHz. The high Q-factor indicates low loss and improved selectivity. The rejection levels in the stopband are greater than 20 dB.


The results indicate that the proposed filter is a suitable choice for low-power small-scale wireless systems operating in the microwave bands. The realized filter has the smallest footprint of 0.36λeff  × 0.19λeff where λeff is the effective wavelength calculated at the lowest frequency of operation.



Funding: No funding was obtained for executing this research.

Conflicts of interest/competing interests: There is no conflict of interest with respect to this submission.

Availability of data and material (data transparency): No new data was generated.

Code availability (software application or custom code): The work does not involve any software codes.


P., P. and J., M. (2022), "Design and implementation of miniaturized tri-band microwave bandpass filter", Microelectronics International, Vol. 39 No. 2, pp. 91-99.



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