Patent ID: 6144255
Filing Date: 2000-11-07
Classification: H03F

Abstract:
Apparatus for reducing out-of-band frequency components of an amplified RF input signal, said amplified signal having both in-band frequency components and out-of band frequency components, and said input signal having in-band frequency components, such apparatus receiving a delayed input signal and said amplified signal, such apparatus comprising:(A) a feedback network, comprising:(i) a first combiner coupled to the input signal and the amplified signal;(ii) a variable gain-phase network controlled by first and second control signals; and(iii) an error amplifier connected to the output of the variable gain-phase network, the error amplifier amplifying the output of the network and the amplified output being delivered to a second combiner, the second combiner receiving as a second input a delayed version oft eh amplified signal; and(B) a feedback loop coupled to the output of the second combiner for adjusting the gain and phase of the variable gain-phase network in accordance with out-of-band frequency components in the amplified signal,the feedback loop comprisinga microprocessor,a frequency generator responsive to the microprocessor,a mixer having a first input coupled to the second combiner output and a second input coupled to the frequency generator,filtering and analysis circuitry including a bandpass filter and an analog-to-digital converter for measuring out-of-band energy at at least one selected bandpass frequency; andsaid microprocessor, in response to said filtering and analysis circuitry, sweeping said frequency generator output across a band of selected frequencies to find a carrier frequency of said input signal, and thereafter for reducing the energy in the out-of-band frequency components in the amplified signal.