The Boeing Company

David L Crampton

Jennifer L Vollbrecht

Lauriston Chin Wah

Anthony L McKay

Kuang Yung Liu

Peter Y Cheung

Henry P Warren

A method and apparatus for reducing intermodulation distortion is disclosed. In one embodiment, the method comprises the steps of accepting a sampled input signal V(t) wherein the input signal V(t) comprises a plurality of peaks; determining n peaks V,V, . . . Vof the sampled input signal V(t) exceeding a clip value Vat times t, t, . . . t; and modifying the sampled input signal V(t) by weighting the n peaks V,V, . . . ,Vexceeding the clip value Vof the sampled input signal V(t) by a function b(t) wherein b(t) is either a hard limiting function or b(t)=f(a, a, . . . a;t&#x2212;t,t&#x2212;t, . . . t&#x2212;t), wherein a,a, . . . aare weight values corresponding to the n peaks V, V, . . . V, and f(t&#x2212;t,t&#x2212;t, . . . t&#x2212;t) is a smooth shaping function. Intermodulation performance is then selectively improved in selected sub-bands by notch filtering prior to application to the non-linearity.

Method and apparatus for low intermodulation distortion amplification in selected bands

The digital signal is provided to the digital-to-analog upconverter ( ) such as through digital signal processing circuitry ( ). A sample rate signal and a divided sample rate signal are provided by divider chain ( ) using the clock input ( ). The divided sample rate signal is used to drive the decode circuit ( ). The digital outputs of the decoder circuit ( ) is combined with the sample rate signal in a mixer ( ) which in turn generates a digitally upconverted signal which drives a plurality of switches combined together to form the analog output ( ).

Digital-to-analog upconverter

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Rossmoor, CA, United States of America

David L Crampton