DocumentCode :
1290361
Title :
Lumped-Element Fully Tunable Bandstop Filters for Cognitive Radio Applications
Author :
Ou, Yu-Chin ; Rebeiz, Gabriel M.
Author_Institution :
Electr. & Eng. & Comput. Sci., Univ. of California at San Diego, La Jolla, CA, USA
Volume :
59
Issue :
10
fYear :
2011
Firstpage :
2461
Lastpage :
2468
Abstract :
This paper presents tunable lumped-element bandstop filters for the UHF-band cognitive radio systems. The two-pole filters are implemented using lumped elements with both single- and back-to-back silicon varactor diodes. The single diode filter tunes from 470 to 730 MHz with a 16-dB rejection bandwidth of 5 MHz and a filter quality factor of 52-65. The back-to-back diode filter tunes from 511 to 745 MHz, also with a 16-dB rejection bandwidth of 5 MHz and a quality factor of 68-75. Both filters show a low insertion loss of 0.3-0.4 dB. Nonlinear measurements at the filter null with Δf = 2 MHz show that the back-to-back diode filter results in 12-dBm higher third-order intermodulation intercept point than the single diode filter. A scaling series capacitor is used in the resonator arm of the back-to-back diode filter and allows a power handling of 25 dBm at the 16-dB rejection null. The cascaded response of two tunable filters is also presented for multiband rejection applications, or for a deeper rejection null (>;36 dB with 0.6-dB loss at 600 MHz). The topology can be easily extended to higher order filters and design equations are presented.
Keywords :
band-stop filters; cognitive radio; silicon; varactors; back to back diode filter; cognitive radio applications; filter quality factor; low insertion loss; lumped element fully tunable bandstop filters; nonlinear measurements; silicon varactor diodes; single diode filter; two pole filters; Bandwidth; Capacitors; Filtering theory; Integrated circuit modeling; Inverters; Microwave filters; Resonator filters; Bandstop filter; cognitive radio; lumped element;
fLanguage :
English
Journal_Title :
Microwave Theory and Techniques, IEEE Transactions on
Publisher :
ieee
ISSN :
0018-9480
Type :
jour
DOI :
10.1109/TMTT.2011.2160965
Filename :
5975230
Link To Document :
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