A cancellation circuit is provided for canceling undesirable intermodulation (IM) products in electrical circuitry. The IM cancellation circuit includes a stepping spectrum analyzer which recognizes and measures the frequencies and amplitudes of different signal components of an RF signal across a desired frequency band. This information is forwarded to a processor which contains look-up tables or the like which provides information relating to the frequencies and/or amplitudes of signal components which are intended to reside in the RF signal. By comparison of the look-up tables to the frequencies and amplitudes measured and recognized by the sweeping spectrum analyzer, the processor of the cancellation circuit is able to determine whether the signal components in the RF signal are intended "information" carrying signals or unintended IM products. Where the processor has determined that a signal component is an unintended IM product, the processor controls a variable voltage controlled oscillator and variable amplifier to create a cancellation signal having an identical frequency and amplitude as the frequency and amplitude of the IM product. A phase shifter is provided to shift the phase of the cancellation signal 180 degrees with respect to the IM product and the cancellation signal is combined with the RF signal to produce an output signal having the IM product canceled.
REFERENCE TO RELATED APPLICATION
The present application is a continuation-in-part of copending U.S. application Ser. No. 09/639,282 filed Aug. 15, 2000, now abandoned titled "INTERMODULATION PRODUCT CANCELLATION CIRCUIT," the entire contents of which is hereby incorporated by reference in its entirety.
A feed forward type distortion compensation amplification apparatus, which includes a distortion detection loop and a distortion compensation loop, cancels a first distortion element generated from the distortion detection loop by a second distortion element generated from the distortion compensation loop to generate an output signal, and controls bias levels of the main amplifier and the error amplifier based on a level of the output signal. An adaptive pre-distortion type distortion compensation amplification apparatus includes a detection unit for detecting an input power level, a control unit for storing the input power level and a bias level corresponding thereto and generating the bias level in response to the input power level, and a bias control unit for applying a bias to an amplifier unit in response to the bias level.
A method for aligning a feed forward radio frequency power amplifier includes applying a radio frequency signal to the feed forward radio frequency power amplifier and monitoring a radio frequency signal from the feed forward radio frequency power amplifier, without opening a break point of the feed forward radio frequency amplifier.
A predistorter including a modulator configured for use with an RF power amplifier or in an amplifier system that combines in a data structure correction factors for amplitude and phase non-linearities in the responses of the amplifier and the modulator. Correction factors for memory effects in the response of the RF power amplifier may also be calculated within the data structure from scale factors transferred into the data structure. Such a calculation may be based on a scaled polynomial. A circuit for applying the difference equation to the correction factors may also be included.
