Optimisation of SIW bandpass filter with wide and sharp stopband using space mapping

ABSTRACT

This work presents a substrate integrated waveguide (SIW) bandpass filter with wide and precipitous stopband, which is different from filters with a direct input/output coupling structure. Higher modes in the SIW cavities are used to generate the finite transmission zeros for improved stopband performance. The design of SIW filters requires full wave electromagnetic simulation and extensive optimisation. If a full wave solver is used for optimisation, the design process is very time consuming. The space mapping (SM) approach has been called upon to alleviate this problem. In this case, the coarse model is optimised using an equivalent circuit model-based representation of the structure for fast computations. On the other hand, the verification of the design is completed with an accurate fine model full wave simulation. A fourth-order filter with a passband of 12.0–12.5 GHz is fabricated on a single layer Rogers RT/Duroid 5880 substrate. The return loss is better than 17.4 dB in the passband and the rejection is more than 40 dB in the stopband. The stopband is from 2 to 11 GHz and 13.5 to 17.3 GHz, demonstrating a wide bandwidth performance.

KEYWORDS:

• Substrate integrated waveguide
• filter
• stopband
• space mapping algorithm
• non-physical cross-coupling

Acknowledgements

This work was supported in part by the National Natural Science Foundation of China (61271076, 61431006 and 61571227) and the Fundamental Research Funds for the Central Universities (No.30915011317 and No.30920140122005) and the Open Research Program of State Key Lab of Millimeter Waves, Southeast University (K201610).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported in part by the National Natural Science Foundation of China [grant numbers 61271076, 61431006 and 61571227] and the Fundamental Research Funds for the Central Universities [grant numbers 30915011317 and 30920140122005] and the Open Research Program of State Key Lab of Millimeter Waves, Southeast University [grant number K201610].