Digital compensation for amplifier-induced instability

1. A method for correcting thermally-induced radar signal transient variation induced by power amplification in a pulse radar transmitter, said method comprising:

establishing a first plurality of characteristics of a reference pulse sequence having a reference digital pulse repeatable over said reference pulse sequence;

establishing a second plurality of characteristics of a transmit pulse sequence having a plurality of transmit digital pulses;

comparing said first and second pluralities of characteristics to determine a sequence difference;

providing pre-distortion coefficients for said plurality of transmit digital pulses corresponding to the signal transient variation in response to said sequence difference, said coefficients altering complex gain; and

applying said coefficients to said plurality of transmit digital pulses prior to the power amplification in the pulse radar transmitter.

2. The method according to claim 1 , wherein providing said coefficients includes searching a waveform library.

3. The method according to claim 1 , wherein said first and second pluralities of characteristics include waveform name, pulse modulation, modulation bandwidth, pulse width, pulse duty cycle and number of pulses.

4. The method according to claim 1 , wherein said pre-distortion coefficients include modulation conversion correction.

5. The method according to claim 4 , wherein said modulation correction includes at least one of amplitude modulation-to-amplitude modulation conversion and amplitude modulation-to-phase modulation conversion.

6. The method according to claim 4 , wherein said modulation correction is approximated by a second order polynomial.

7. The method according to claim 1 , wherein said pre-distortion coefficients provide phase-only pre-distortion for said complex gain.

8. The method according to claim 1 , wherein said reference and transmit pulse sequences are scheduled by respective first and second radar event messages.

9. The method according to claim 1 , wherein comparing said first and second pulse pluralities of characteristics further includes:

synthesizing a waveform;

producing reference and sample signals from said waveform, said reference signal representing said reference digital pulse, and said sample signal representing a transmit digital pulse among said plurality of transmit digital pulses;

amplifying said sample signal by said complex gain to produce an amplified signal;

cross-correlating said reference and amplified signals to produce a difference signal for each digital pulse in said second pulse sequence;

determining peak cross-correlation and corresponding time for said difference signal; and

producing said pre-distortion coefficients for said waveform.

10. The method according to claim 9 , further including storing said pre-distortion coefficients in a waveform library for comparison searches.

11. The method according to claim 9 , wherein producing said signals further includes digitizing said reference signal as a digital reference signal and said sample as a digital sample signal.

12. The method according to claim 11 , wherein said digitizing operation includes conversion to in-phase and quadrature form.

13. The method according to claim 1 , wherein said complex gain denotes mean amplitude and mean phase.