We present a new circuit design for adaptive offset cancellation in a fully differential
2.4 GHz CMOS direct conversion mixer. Our circuit structure is a modification of a
Gilbert cell mixer in which offsets are cancelled by injecting cancellation currents
into the legs of the mixer by dynamically varying the bias on the active loads. We
present analysis and simulation results of our mixer with offsets present. Offsets
create non-linearities in any circuit by differentially shifting the small-signal bias
point of a matched pair; forcing once symmetrical transistors to operate in different
bias regions and create second order distortion. We focus our design to minimize
second order distortion while simultaneously canceling the large offsets found in
direct conversion receivers. Simulation results for the mixer canceling a wide range
of offsets are included. Our mixer has a gain of 6.4dB, an IIP3 of 17dBm and a noise
figure of 17dB as simulated in a .5��m HP Mosis CMOS process. / Graduation date: 2002
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/32448 |
| Date | 16 May 2001 |
| Creators | Lehne, Mark A. |
| Contributors | Stonick, John T. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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