Design of Tunable Multi-Pole Multi-Zero Bandpass Filters and Diplexer With High Selectivity and Isolation

This paper presents two tunable three-pole filters and their application to a tunable three-pole diplexer. The first tunable three-pole filter utilizes both quarter- and half-wavelength resonators. By introducing electric and magnetic coupling and source–load coupling, three transmission zeroes are realized with two zeroes at the lower side, resulting in high rejection at lower side. The second three-pole filter is based on the classical cascade tri-section filter. With source–load coupling, three transmission zeroes are generated with two zeroes located on the upper side, resulting in a high rejection. Finally, a tunable diplexer is demonstrated using two tunable three-pole filters and exhibits high selectivity, high suppression, and high isolation over a wide tuning range due to the asymmetric high rejection level of the three-pole filters. The filters and diplexer are theoretically analyzed and experimentally demonstrated. Comparisons between the measured and simulated results are presented to verify the proposed designs.

[1]  Pei-Ling Chi,et al.  Three-Pole Reconfigurable 0.94–1.91-GHz Diplexer With Bandwidth and Transmission Zero Control , 2017, IEEE Transactions on Microwave Theory and Techniques.

[2]  Guo-Yun Wang,et al.  Microstrip Switchable and Fully Tunable Bandpass Filter With Continuous Frequency Tuning Range , 2018, IEEE Microwave and Wireless Components Letters.

[3]  F. Lin,et al.  Continuously Tunable 0.55–1.9-GHz Bandpass Filter With a Constant Bandwidth Using Switchable Varactor-Tuned Resonators , 2017, IEEE Transactions on Microwave Theory and Techniques.

[4]  Yuanan Liu,et al.  A Simple Planar Dual-Band Bandpass Filter With Multiple Transmission Poles and Zeros , 2018, IEEE Transactions on Circuits and Systems II: Express Briefs.

[5]  Quan Xue,et al.  Novel Varactor-Tuned Coupling Mechanism and Its Applications to High-Order Bandwidth-Agile Bandpass Filters , 2017, IEEE Transactions on Components, Packaging and Manufacturing Technology.

[6]  R. Cameron.  Advanced coupling matrix synthesis techniques for microwave filters , 2003 .

[7]  Jia-Sheng Hong,et al.  Microstrip cross-coupled trisection bandpass filters with asymmetric frequency characteristics , 1999 .

[8]  Wenquan Che,et al.  Tunable Dual-Band Filter and Diplexer Based on Folded Open Loop Ring Resonators , 2017, IEEE Transactions on Circuits and Systems II: Express Briefs.

[9]  Lin Yang,et al.  Three-Pole Tunable Filters With Constant Bandwidth Using Mixed Combline and Split-Ring Resonators , 2014, IEEE Microwave and Wireless Components Letters.

[10]  Gabriel M. Rebeiz,et al.  A 1.4–2.3-GHz Tunable Diplexer Based on Reconfigurable Matching Networks , 2015, IEEE Transactions on Microwave Theory and Techniques.

[11]  Gabriel M. Rebeiz,et al.  Tunable 1.25–2.1-GHz 4-Pole Bandpass Filter With Intrinsic Transmission Zero Tuning , 2015, IEEE Transactions on Microwave Theory and Techniques.

[12]  Lei Zhu,et al.  Design of Multistate Diplexers on Uniform- and Stepped-Impedance Stub-Loaded Resonators , 2019, IEEE Transactions on Microwave Theory and Techniques.

[13]  Gabriel M. Rebeiz,et al.  Tunable Three-Pole Diplexer with High Selectivity and Isolation , 2018, 2018 IEEE/MTT-S International Microwave Symposium - IMS.

[14]  Gabriel M. Rebeiz,et al.  A low-loss 1.4–2.1 GHz compact tunable three-pole filter with improved stopband rejection using RF-MEMS capacitors , 2016, 2016 IEEE MTT-S International Microwave Symposium (IMS).

[15]  Jin Xu,et al.  Tunable Bandpass Filter Using a Switched Tunable Diplexer Technique , 2017, IEEE Transactions on Industrial Electronics.

[16]  Sheng-Fa Chang,et al.  A compact tunable microstrip diplexer using varactor-tuned dual-mode stub-loaded resonators , 2014, 2014 IEEE MTT-S International Microwave Symposium (IMS2014).

[17]  Xiu Yin Zhang,et al.  Low-Loss Frequency-Agile Bandpass Filters With Controllable Bandwidth and Suppressed Second Harmonic , 2010, IEEE Transactions on Microwave Theory and Techniques.

[18]  Gabriel M. Rebeiz,et al.  Three-Pole 1.3–2.4-GHz Diplexer and 1.1–2.45-GHz Dual-Band Filter With Common Resonator Topology and Flexible Tuning Capabilities , 2013, IEEE Transactions on Microwave Theory and Techniques.

[19]  Dimitrios Peroulis,et al.  Tunable SIW Cavity-Based Dual-Mode Diplexers With Various Single-Ended and Balanced Ports , 2018, IEEE Transactions on Microwave Theory and Techniques.

[20]  Gabriel M. Rebeiz,et al.  A Simple and Effective Method for 1.9–3.4-GHz Tunable Diplexer With Compact Size and Constant Fractional Bandwidth , 2016, IEEE Transactions on Microwave Theory and Techniques.

[21]  Zhewang Ma,et al.  Compact, Low Insertion-Loss, and Wide Stopband HTS Diplexer Using Novel Coupling Diagram and Dissimilar Spiral Resonators , 2016, IEEE Transactions on Microwave Theory and Techniques.

[22]  Xiaohong Tang,et al.  Synthesis-Applied Highly Selective Tunable Dual-Mode BPF With Element-Variable Coupling Matrix , 2018, IEEE Transactions on Microwave Theory and Techniques.

[23]  Wei Qin,et al.  Wideband Tunable Bandpass Filter Using Optimized Varactor-Loaded SIRs , 2017, IEEE Microwave and Wireless Components Letters.

[24]  Quan Xue,et al.  Tunable Balanced Bandpass Filter With Constant Bandwidth and High Common-Mode Suppression , 2011, IEEE Transactions on Microwave Theory and Techniques.