Differential bandpass filter with high common-mode rejection ratio inside the differential-mode passband using controllable common-mode transmission zero

Controllable common-mode transmission zero is proposed to improve the common-mode rejection ratio (CMRR) inside the differential-mode passband of differential bandpass filters. With the controllability of the common-mode transmission zero, the common-mode transmission zero can be moved into the frequency range of the differential-mode passband, and then the CMRR inside the differential-mode passband can be greatly improved. Two two-order filters using different resonators are designed to demonstrate the existence and controllability of the common-mode transmission zero. A four-order filter with two resistor-loaded stepped-impedance resonators (SIRs) and two resistor-loaded uniform impedance resonators (UIRs) are designed to get good selectivity of differential-mode passband and wide-band common-mode suppression besides the high CMRR inside the differential-mode passband. The design methodology and experimental results of the proposed filters are presented.

[1]  T. B. Lim,et al.  A Differential-Mode Wideband Bandpass Filter on Microstrip Line for UWB Application , 2009, IEEE Microwave and Wireless Components Letters.

[2]  Chi-Hsueh Wang,et al.  Balanced Coupled-Resonator Bandpass Filters Using Multisection Resonators for Common-Mode Suppression and Stopband Extension , 2007, IEEE Transactions on Microwave Theory and Techniques.

[3]  Quan Xue,et al.  Planar Tri-Band Bandpass Filter With Compact Size , 2010, IEEE Microwave and Wireless Components Letters.

[4]  Wen Wu,et al.  Design of Miniaturized Microstrip Dual-Mode Filter With Source-Load Coupling , 2010, IEEE Microwave and Wireless Components Letters.

[5]  Quan Xue,et al.  Dual-Band and Wide-Stopband Single-Band Balanced Bandpass Filters With High Selectivity and Common-Mode Suppression , 2010, IEEE Transactions on Microwave Theory and Techniques.

[6]  Qing-Xin Chu,et al.  A Narrow-Band Hairpin-Comb Two-Pole Filter With Source-Load Coupling , 2010, IEEE Microwave and Wireless Components Letters.

[7]  W. Eisenstadt,et al.  Combined differential and common-mode scattering parameters: theory and simulation , 1995 .

[8]  S.-M. Wu,et al.  VERY COMPACT FULL DIFFERENTIAL BANDPASS FILTER WITH TRANSFORMER INTEGRATED USING INTEGRATED PASSIVE DEVICE TECHNOLOGY , 2011 .

[9]  Quan Xue,et al.  A novel differential bandpass filter based on double‐sided parallel‐strip line dual‐mode resonator , 2008 .

[10]  Chi-Hsueh Wang,et al.  Novel Balanced Coupled-Line Bandpass Filters With Common-Mode Noise Suppression , 2007, IEEE Transactions on Microwave Theory and Techniques.

[11]  Balanced Dual-Band BPF using only Equal-Electric-Length SIRs for Common-Mode Suppression , 2010 .