A Very Compact and Sharp Roll-Off Low-Pass Filter with Four Transmission Zeros

作者：Xiao Yang; Li Lin^*

来源：Active and Passive Electronic Components, 2015, 2015: 1-6.

DOI：10.1155/2015/806276

• Compact size
• Extended stopband
• Filter dimensions
• Filter structures
• Novel structures
• Open stubs
• Transmission zeros
• Wide stopband

<jats:p>A novel structure with sharp roll-off, wide stopband, and very compact size is presented in this paper. By combining a capacitor-embedded transmission line ring and two shunt open stubs, this structure exhibits a high-performance three-pole low-pass filter (LPF) response with four generated transmission zeros. With the help of these four transmission zeros, the proposed LPF achieves improved roll-off rate, extended stopband, and significantly very compact size. To verify the feasibility of the proposed structure, a prototype LPF having the cut-off frequency at 0.63 GHz is designed, fabricated, and measured as an illustrative example. Final result shows that a roll-off rate of 109.3 dB/GHz along with a relative stopband bandwidth of 114.6% can be obtained. Moreover, the filter dimensions are as small as 15.7 mm × 26.9 mm, that is,<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mn>0.004</mml:mn><mml:msup><mml:mrow><mml:msub><mml:mrow><mml:mi>λ</mml:mi></mml:mrow><mml:mrow><mml:mi>g</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:math>, where<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"><mml:mrow><mml:msub><mml:mrow><mml:mi>λ</mml:mi></mml:mrow><mml:mrow><mml:mi>g</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>is the guided wavelength at the cut-off frequency. The filter structure is simple and easy to fabricate as well.</jats:p>

• 出版日期2015--