Novel Varactor-Tuned Balanced Bandpass Filter with Continuously High Common-Mode Suppression
Keywords:
Balanced bandpass filter (BPF), common-mode suppression, half-wavelength resonator, tunable filterAbstract
In this letter, a novel balanced varactor-tuned bandpass filter (BPF) designed by using the half-wavelength microstrip resonators is proposed. The frequency-tuning mechanism of the resonator is analytically investigated for designing the proposed balanced BPF. By adding a tunable capacitor to the center of the resonator, it is noted that the common mode can be suppressed to a great extent in the frequency-tuning range of the differential-mode passband. Also, it has no effect on the differential-mode response. For demonstration, a balanced BPF is designed and fabricated. The simulated and measured results with good agreement show that the center frequency of the differential-mode passband can be tuned from 0.725 GHz to 0.811 GHz, while the common-mode suppression in this frequency range is always more than 25 dB.
Downloads
References
J. Shi and Q. Xue, “Balanced bandpass filters using center-loaded half-wavelength resonators,” IEEE Trans. Microw. Theory Tech., vol. 58, no. 4, pp. 970-977, April 2010.
K. T. Chen and S. J. Chung, “A novel compact balanced-to-unbalanced low-temperature co-fired ceramic bandpass filter with three coupled lines configuration,” IEEE Trans. Microw. Theory Tech., vol. 56, no. 7, pp. 1714-1720, July 2008.
C. H. Wu, C. H. Wang, and C. H. Chen, “Balanced coupled-resonator bandpass filter using multi-section resonators for common-mode suppression and stopband extension,” IEEE Trans. Microw. Theory Tech., vol. 55, no. 8, pp. 1756- 1763, Aug. 2007.
C. H. Wu, C. H. Wang, and C. H. Chen, “Novel balanced coupled-line bandpass filters with common-mode noise suppression,” IEEE Trans. Microw. Theory Tech., vol. 55, no. 2, pp. 287-295, Feb. 2007.
X. H. Wang, Q. Xue, and W. W. Choi, “A novel ultra-wideband differential filter based on doublesided parallel-strip line,” IEEE Microw. Wireless Compon. Lett., vol. 20, no. 8, pp. 471-473, Aug. 2010.
C. H. Lee, C. I. G. Hsu, and C. C. Hsu, “Balanced dual-band BPF with stub-loaded SIRs for common-mode suppression,” IEEE Microw. Wireless Compon. Lett., vol. 20, no. 2, pp. 70-72, Feb. 2010.
Y. C. Li and Q. Xue, “Tunable balanced bandpass filter with constant bandwidth and high commonmode suppression,” IEEE Trans. Microw. Theory Tech., vol. 59, no. 10, pp. 2452-2460, Oct. 2011.
J. X. Chen, Z. H. Bao, C. Xu, and G. A. Zhang, “Uniplanar tunable bandpass filter using centrallyloaded slot-line resonator,” Microwave and Optical Tech. Lett., vol. 52, no. 12, pp. 2805-2807, Dec. 2010.
S. W. Chen, J. W. Wu, J. D. Wu, and J. S. Li, “Tunable active bandpass filter design,” Electron. Lett., vol. 47, no. 3, pp. 1019-1021, Sept. 2011.
S. R. Chandler, I. C. Hunter, and J. G. Gardiner, “Active varactor tunable bandpass filter,” IEEE Microwave Guided Wave Lett., vol. 3, no. 18, pp. 70-71, Mar. 1993.
X. Y. Zhang and Q. Xue, “High-selectivity tunable bandpass filters with harmonic suppression,” IEEE Trans. Microw. Theory Tech., vol. 58, no. 4, pp. 964-969, April 2010.
A. Tombak, J. P. Maria, F. T. Ayguavives, J. Zhang, G. T. Stauf, A. -I. Kingon, and A. Mortazawi, “Voltage-controlled RF filter employing thin-film barium-strontium-titanate tunable capacitors,” IEEE Trans. Microw. Theory Tech., vol. 51, no. 2, pp. 462-467, Feb. 2003.
