Adaptive channel equalization technique and method for wideband passive digital receivers

A channel equalizer system for a wideband passive receiver for a passive electronic intelligence surveillance system, comprising:

• an equalizing filter coupled to receive digital signals from a receiver operating subject to environmental distortions, the equalizing filter having a filter response controlled by time-varying filter control signals and being configured to output filtered digital signals, the equalizing filter being configured to provide adaptive equalization of transfer function characteristics for the wideband passive receiver, and the digital signals being representative of an RF input signal spectrum comprising signals from unknown signal sources;
• a calibration signal generator configured to generate a wideband RF calibration signal to provide as a selectable RF calibration input signal to the receiver and configured to generate a desired output signal based upon the generated RF calibration input signal, the calibration signal generator being further configured to generate the wideband RF calibration signals and the desired output signals periodically over time to provide calibration dwells for the receiver during its operation;
• and
• equalizer control circuitry coupled to receive filtered digital signals as feedback and coupled to receive the desired output signal from the calibration signal generator, the equalizer control circuitry being configured to generate the time-varying filter control signals to provide adaptive equalization of the transfer function characteristics for the wideband passive receiver, and the filter control signals being configured to correct distortions caused by operational variations in the transfer function characteristics of the receiver operating subject to environmental distortions.

A method for equalizing a channel within a wideband passive receiver system for a passive electronic intelligence surveillance system, comprising:

• selectively receiving an RF input signal spectrum or an injected RF calibration input signal and processing the input signal to produce digital output signals, the RF input signal spectrum comprising signals from unknown signal sources and the receiver operating subject to environmental distortions;
• filtering the digital signals to produced equalized digital output signals, the filtering being controlled by time-varying filter control signals and being configured to provide adaptive equalization of transfer function characteristics for the wideband passive receiver system;
• and
• periodically selecting to receive the RF calibration input signal over time to provide calibration dwells for the receiver system during its operation, and when the injected RF calibration input signal is selectively received:
• generating a wideband RF calibration signal to provide the injected RF calibration input signal and generating a desired output signal based upon the generated RF calibration input signal;
• and
• processing the equalized digital output signals as feedback and the desired output signal to generate the time-varying filter control signals to provide adaptive equalization of the transfer function characteristics for the wideband passive receiver, and the filter control signals being configured to correct distortions caused by operational variations in transfer function characteristics of the receiver system operating subject to environmental distortions.