© The Institution of Engineering and Technology
Tunable differential-mode filters with wide tuning range and high common-mode suppression are proposed. Step-impedance resonators terminated with varactors are proposed and used to construct the tunable filter. Symmetrical parallel coupled lines terminated with varactors are used as a negative coupling bisection, which results in convenient tuning of coupling coefficient and bandwidth control. Capacitors are placed at the four ports to adjust the external quality factor. With these techniques and the choice of a high capacitance ratio varactor, a wide tuning range up to 75% has been achieved. Tunable differential-mode filters with constant absolute bandwidth (ABW) and constant fractional bandwidth (FBW) are realised, respectively. The constant ABW filter has a −3 dB bandwidth of 95 ± 10 MHz and an insertion loss of 5.7 − 2.5 dB. The constant FBW filter has a −3 dB bandwidth of 9.8 ± 1.2% and an insertion loss of 6.0 − 1.7 dB. In addition, a capacitor is loaded on the symmetry plane to misalign common-mode resonant frequencies, resulting in high common-mode noise rejection in the whole frequency range.
References
-
-
1)
-
S.J. Park ,
G.M. Rebeiz
.
Low-loss two-pole tunable filters with three different predefined bandwidth characteristics.
IEEE Trans. Microw. Theor. Tech.
,
5 ,
1137 -
1148
-
2)
-
2. Eisenstadt, W.R., Stengel, B., Thompson, B.M.: ‘Microwave differential circuit design using mixed-mode S-parameters’. (Artech House, Norwood, 2006).
-
3)
-
10. Li, Y.C., Xue, Q.: ‘Tunable balanced bandpass filter with constant bandwidth and high common-mode suppression’, IEEE Trans. Microw. Theory Tech., 2011, 59, (10), pp. 2452–2460 (doi: 10.1109/TMTT.2011.2161325).
-
4)
-
T.B. Lim ,
L. Zhu
.
A differential-mode wideband bandpass filter on microstrip line for UWB application.
IEEE Microw. Wirel. Compon. Lett.
,
10 ,
632 -
634
-
5)
-
4. El-Tanani, M.A., Rebeiz, G.M.: ‘High performance 1.5–2.5 GHz RF MEMS tunable filters for wireless applications’, IEEE Trans. Microw. Theory Tech., 2010, 58, (6), pp. 1629–1637 (doi: 10.1109/TMTT.2010.2049166).
-
6)
-
Y.-C. Chiou ,
J.-T. Kuo ,
E. Cheng
.
Broadband quasi-Chebyshev bandpass filters with multimode stepped-impedance resonators (SIRs).
IEEE Trans. Microw. Theory Tech.
,
8 ,
3352 -
3358
-
7)
-
E.M.T. Jones ,
J.T. Bolljahn
.
Coupled strip transmission line filters and directional couplers.
IEEE Trans. Microw. Theory Technol.
,
2 ,
75 -
81
-
8)
-
11. Cameron, R.J., Kudsia, C.M., Mansour, R.R.: ‘Microwave filters for communication systems: fundamentals, design, and applications’ (Wiley, New York, 2007).
-
9)
-
C.-H. Wu ,
C.-H. Wang ,
C.H. Chen
.
Novel balanced coupled-line bandpass filters with common-mode noise suppression.
IEEE Trans. Microw. Theory Tech.
,
2 ,
287 -
295
-
10)
-
D.E. Bockelman ,
W.R. Eisenstant
.
Combined differential and common-mode scattering parameters: theory and simulation.
IEEE Trans. Microw. Theory Tech.
,
7 ,
1530 -
1539
-
11)
-
J. Shi ,
Q. Xue
.
Dual-band and wide-stopband single-band balanced bandpass filters with high selectivity and common-mode suppression.
IEEE Trans. Microw. Theory Tech.
,
8 ,
2204 -
2212
-
12)
-
C.H. Wu ,
C.H. Wang ,
C.H. Chen
.
Balanced coupled-resonator bandpass filters using multisection resonators for common-mode suppression and stopband extension.
IEEE Trans. Microw. Theory Tech.
,
8 ,
1756 -
1763
-
13)
-
W.J. Feng ,
W.Q. Che
.
Novel ultra-wideband bandpass filter using shorted coupled lines and transversal transmission line.
IEEE Microw. Wirel. Compon. Lett.
,
10 ,
548 -
551
http://iet.metastore.ingenta.com/content/journals/10.1049/iet-map.2012.0203
Related content
content/journals/10.1049/iet-map.2012.0203
pub_keyword,iet_inspecKeyword,pub_concept
6
6