Relevant publications:

Fourth-Order Q-Enhanced Band-pass Filter Tuning Algorithm Implementation and Considerations
Joel R. Schonberger, Kansas State University, 2010

Automatic Tuning of Q-Enhanced Integrated Differential Bandpass Filters in a Silicon-on-Sapphire Process
Renee Strouts, Kansas State University, 2007

A 2.5 GHz Low-power, High-Dynamic Range, Self-tuned Q-Enhanced LC filter in SOI
Xin He and William B. Kuhn
IEEE Journal of Solid State Circuits, pp. 1618-1628, Aug 2005

A Fully Integrated Q-Enhanced LC Filter with 6 dB Noise Figure at 2.5 GHz in SOI
He, X.; Kuhn, W.B.
IEEE Radio Frequency Integrated Circuits Symposium, p. 643-646, 2004

Noise Analysis and Automatic Tuning of Q-Enhanced LC Bandpass Filters
Aaron Williams Oorsborn M.S., Kansas State University, 2002

Bandpass ΣΔ Modulator Employing Undersampling and on-chip Q-Enhanced LC Filter
Hussein, A.I.; Kuhn, W.B.
Processions of the IEEE Southwest Symposium on Mixed-Signal Design, 1999. SSMSD '99. 1999 Southwest Symposium on , 11-13 April 1999

A High Dynamic Range, Digitally tuned, Q-Enhanced LC Bandpass Filter for Cellular/PCS Receivers
Kuhn, W.B.; Yanduru, N.K.; Wyszynski, A.S.
Microwave Symposium Digest, 1998 IEEE MTT-S International ,Volume: 1 , 7-12 June 1998

Q-Enhanced LC Bandpass Filters for Integrated Wireless Applications
Kuhn, W.B.; Yanduru, N.K.; Wyszynski, A.S.
Microwave Theory and Techniques, IEEE Transactions on ,Volume: 46 , Issue: 12 , Dec. 1998

A 200 MHz CMOS Q-enhanced LC bandpass filter
Kuhn, W.B.; Stephenson, F.W.; Elshabini-Riad, A.
Solid-State Circuits, IEEE Journal of ,Volume: 31 , Issue: 8 , Aug. 1996


Q-Enhanced Filters

Filters are among the most imperative components used in RF communications, and without them multi-channel communications would be impossible to achieve.  One way filters are characterized is by their Q-Factor ("Quality-Factor").  Filters with large Q values are often described as having a "sharp roll-off" which implies that the filter's passband has well-defined beginning and end points.  Filters of low Q values will have their passband roll-off in a very shallow manner. 

Hence, filtering is of the utmost importance in communications, since interference signals are almost always unintentionally produced by RF hardware.  This noise comes from harmonic oscillations, reflections, and various other causes.  One goal of the Communications Research Lab has been to design and fabricate Q-Enhanced filters, or rather filters of very high Q values.  This process includes using refined spiral inductor techniques to create inductors that behave as ideally as possible.

Below is a video of the frequency response of a Q-Enhanced filter, heated to 75 °C.  Notice how sharp the roll-off is, as well as the narrowness of the passband.