1. 期 中 報 告 微 波 工 程 期 中 報 告 微 波 工 程 授課老師 : 陳文山 學號 :M9930203 學生 : 陳瑞傑 1

2. Electronically Tunable Filters Peng Wen Wong and Ian Hunter are with the Institute of Microwave and Photonics, School of Electronic and Electrical Engineering, Leeds, United Kingdom. IEEE microwave magazine 1527-3342/09/$26.00©2009 IEEE October 2009 2

3. Directory  Introduction  microwave systems  Conclusion 3

4. Introduction Modern high frequency systems employ multifunction receiver subsystems that have a broad bandwidth to support multiple frequency bands. This trend has led to the increased demand for filter technologies with adaptable preselection frequency behavior. New developments in the design of reconfigurable microwave filters are essential to meet the stringent demands on eliminating out-of-band noise and jamming spectral components, while simultaneously supporting multiple information channels. Although different realizations of electronically tunable filters have been developed in past decades, most previous works have concentrated on tuning the resonator frequency of the resonators either in a continuous or discrete fashion using semiconductor, ferroelectric, or micro-electromechanical systems (MEMS) varactor’s. Such tunable filters exhibit high losses due to the loading effect caused by the varactor’s impedance. Alternatively, the technique of integrating the active devices into the tunable filter design for loss compensation has been proposed and investigated. However, in designing such filters, we must take into account the distortion effect seen under large power. 資料來源 : Peng Wen Wong and Ian Hunter are with the Institute of Microwave and Photonics, School of Electronic and Electrical Engineering, Leeds, United Kingdom. IEEE microwave magazine 1527-3342/09/$26.00©2009 IEEE October 2009 4

5. microwave systems Figure 1. Electronically switchable filter bank block diagram. Figure 2. Schematic of combline filter Classical Tunable Filter Design Technique 5

6. This filter possesses the important property of maintaining a constant absolute bandwidth over almost an octave of tuning bandwidth. One of the significant drawbacks of using semiconductor varactor’s as the tuning element is the distortion effect caused by the varactors’ inherent nonlinearities. Therefore, the recent developments in electronically tunable filters have concentrated on tuning the resonator frequency of the resonators either in continuous or discrete fashion using ferroelectric or MEMS varactors. A wide variety of ferroelectric and MEMS-based tunable filters have been reported in the where low intermodulation distortion was achieved. 資料來源 : Peng Wen Wong and Ian Hunter are with the Institute of Microwave and Photonics, School of Electronic and Electrical Engineering, Leeds, United Kingdom. IEEE microwave magazine 1527-3342/09/$26.00©2009 IEEE October 2009 Figure 3. Equivalent circuit of combline filter between rth and r + 1th node 6

7. Figure 4. Impedance transforming network at input / output of the combline filter Figure 5. Internal nodal scaling of coupling network 資料來源 : Peng Wen Wong and Ian Hunter are with the Institute of Microwave and Photonics, School of Electronic and Electrical Engineering, Leeds, United Kingdom. IEEE microwave magazine 1527-3342/09/$26.00©2009 IEEE October 2009 7

8. Figure6.Varactor-loaded transmission line resonator Figure 7. Normalized overall resonator Q N versus resistance Rs 資料來源 : Peng Wen Wong and Ian Hunter are with the Institute of Microwave and Photonics, School of Electronic and Electrical Engineering, Leeds, United Kingdom. IEEE microwave magazine 1527-3342/09/$26.00©2009 IEEE October 2009 8

9. Figure 8. Equivalent circuit of active combline filter between rth and r + 1 th node Figure 9. Lumped-distributed coupled- line pair 資料來源 : Peng Wen Wong and Ian Hunter are with the Institute of Microwave and Photonics, School of Electronic and Electrical Engineering, Leeds, United Kingdom. IEEE microwave magazine 1527-3342/09/$26.00©2009 IEEE October 2009 9

10. Figure 10. Bandpass response based on low-pass/highpass cascade configuration Figure 11. Switched delay lines resonator 資料來源 : Peng Wen Wong and Ian Hunter are with the Institute of Microwave and Photonics, School of Electronic and Electrical Engineering, Leeds, United Kingdom. IEEE microwave magazine 1527-3342/09/$26.00©2009 IEEE October 2009 10

11. Figure 13. Parallel-coupled two-stage switched delay lines filter circuit configuration Figure 12. Transmission response of switched delay lines resonator with toggled output switch at point P (solid line) and at position with 20 O electrical length away from point P (dotted line) 資料來源 : Peng Wen Wong and Ian Hunter are with the Institute of Microwave and Photonics, School of Electronic and Electrical Engineering, Leeds, United Kingdom. IEEE microwave magazine 1527-3342/09/$26.00©2009 IEEE October 2009 11

12. Figure 14 shows the microstrip prototype based on SDLs approach. Such a filter possesses a superior mid-band loss advantage over the conventional approach 資料來源 : Peng Wen Wong and Ian Hunter are with the Institute of Microwave and Photonics, School of Electronic and Electrical Engineering, Leeds, United Kingdom. IEEE microwave magazine 1527-3342/09/$26.00©2009 IEEE October 2009 12

13. Figure 15. Measured transmission response of the switched delay lines reconfigurable filter Figure 16. Measured output intermodulation intercept point against frequency separation f 資料來源 : Peng Wen Wong and Ian Hunter are with the Institute of Microwave and Photonics, School of Electronic and Electrical Engineering, Leeds, United Kingdom. IEEE microwave magazine 1527-3342/09/$26.00©2009 IEEE October 2009 13

14. Conclusion Conclusion 資料來源 : Peng Wen Wong and Ian Hunter are with the Institute of Microwave and Photonics, School of Electronic and Electrical Engineering, Leeds, United Kingdom. IEEE microwave magazine 1527-3342/09/$26.00©2009 IEEE October 2009 14 A classical design technique based on a combline filter approach was shown,where minimum degradation in passband performance could be obtained across a broad-tuning range. The fundamental disadvantages associated with the conventional resonator tuning approaches were also discussed, recognizing the importance of developing new techniques for realizing tunable microwave filters. Furthermore, the filter has the ability to incorporate active switching elements in the filter circuit, without sacrificing its loss and linearity performance. With the exceptional linearity performance and power handling capability, the filter is readily adapted to poor environments. Although the use of p-i-n diodes as switching elements would result in large dc consumption, the approach could also be readily adapted for use with any switches, such as pHEMT or RF MEMS switches, to achieve extremely low power consumption.

15. 感想 這篇文章是介紹可調諧濾波器的發展，最根本的缺點與傳統的諧振腔 調諧的方法進行了討論，希望在以後可以發展出可調式諧微波濾波器 。 15