A high-selectivity double-mode SIW bandpass filter utilizing the modified parallel coupled microstrip lines

ABSTRACT

In this article, a high-selectivity double-mode substrate integration waveguide bandpass filter utilizing modified parallel coupled microstrip lines (MPCML) is presented. The designed method is analyzed in detail. Six metal vias are designed to perturb TE-₁₀₁ mode and TE-₁₀₃ mode. The resonant frequency of the perturbed TE-₁₀₁ mode is shifted to high frequency, close to that of TE-₁₀₂ mode, which caused the formation of passband. The resonant frequency of the perturbed TE-₁₀₃ mode is shifted to high frequency, improving out-of-band performance. Simultaneously, the coplanar waveguide structure is used to adjust the external quality factor. Two rectangular slotlines are introduced to adjust center frequency and bandwidth slightly. Two rectangular stubs are designed for better source and load matching. Three transmission zeros (TZs) are obtained to improve the selectivity. The designed MPCML promotes the generation of TZs. Another TZ is obtained by the coupling between TE-₁₀₂ mode and TE-₁₀₃ mode. The designed filter operates at 14.4 GHz with bandwidth of 800 MHz. The measured return loss is better than 15 dB, and the minimum insertion loss is 1.60 dB. The measurement is agreed with the simulation.

KEYWORDS:

• Bandpass filter
• dual-mode
• high-selectivity
• MPCML

Declaration of interest statement

The authors declare that there is no conflict of interests regarding the publication of this article.

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article.

Additional information

Funding

This work was supported by National Natural Science Foundation of China (No: 61871063) and Chongqing Technology Innovation and Application Development Project (cstc2019jscx-msxmX0079).