Feedforward amplification system having mask detection compensation

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 comprising
• a 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;
• and
• said 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.