Cellular Equipment White Papers
Taming the Quadrature Modulator
Overview In any real system there are errors on all signals, and modulators are no exception. This paper focuses directly on the quadrature modulator (QM) system blocks. By applying a linear, first order error model to the ideal quadrature modulator equation, it is shown that there are nine error terms, plus output compression, that the design engineer must pay attention to. Each of these error terms is individually examined for its effect on the QM output signal. It is shown that, in general, offset errors produce signal leakages, and gain errors produce modulation distortions. Error signals that can be filtered out are identified. Non-filterable leakage and distortion terms that require nulling adjustments are also identified. A calibration procedure is proposed that provides maximum performance with a minimum of steps.
| Publisher | Tropian | File Format | PDF, requires Acrobat Rdr 5 |
|---|---|---|---|
| Date Published | January 2000 | Downloads | 65 |
| Format | White Papers | ||
| Topics | |||
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