Patent ID: 7778353

Claim:
A control circuit for a radio-frequency (RF) amplifier, said RF amplifier having a power-dependent characteristic amplification curve, said control circuit comprising: an RF input supplied with an RF signal at RF frequency; an RF signal splitter; a power meter; a signal coupler connected to RF input that couples said RF signal to said RF signal splitter and to said power meter; an IQ controller comprising an I path connected to an I factor input supplied with an I factor, and Q path connected to a Q factor input supplied with a Q factor; said RF signal splitter splitting said RF signal coupled thereto into two RF signals that are respectively offset in phase by 90° relative to each other, a first of said two RF signals being supplied to said I path and a second of said two RF signals being supplied to said Q path; said power meter detecting power of said RF signal coupled thereto, and emitting a low frequency (LF) signal at an output thereof representing the detected power, said LF signal having a frequency that is substantially below said RF frequency; a first pre-emphasizer stage connected to said output of said power meter that applies an I factor correction curve, dependent on said power-dependent characteristic amplification curve, to said LF signal to generate an LF I factor correction value; a second pre-emphasizer stage connected to said output of said power meter that applies a Q factor correction curve, dependent on said power-dependent characteristic amplification curve, to said LF signal to generate an LF Q factor correction value; a first adder connected to said I factor input and to said first pre-emphasizer stage that adds said LF I factor correction value to said I factor, to produce an LF corrected I factor; a second adder connected to said Q factor input and to said second pre-emphasizer stage that adds said LF Q factor correction value to said Q factor, to produce an LF corrected Q factor; a first multiplier connected to said RF signal splitter and to said first adder that multiplies said first of said two RF signals by said LF corrected I factor, to produce a first multiplier output signal; a second multiplier connected to said RF signal splitter and to said second adder that multiplies said second of said two RF signals by said LF corrected Q factor, to produce a second multiplier output; and a third adder connected to said first and second multipliers that add said first and second multiplier outputs to produce a third adder output that is supplied to said RF amplifier.