Signal amplitude restoration apparatus and method
AssigneeSouthwest Research Institute
InventorArthur Fleming-Dahl
Life of this patent
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Abstract
An apparatus for signal amplitude restoration has a received signal input and a scaled received signal output. An amplitude correction factor generator has an estimated signal-to-noise power ratio input and a received signal input. A variable gain amplifier uses the correction factor generator output to control its gain, and amplifies or attenuates the received signal input to provide the scaled received signal output. An average SNR estimator uses the amplifier output as its input, and provides an output connected to the estimated signal-to-noise power ratio input. The apparatus processes received signals in an iterative fashion, such that at least one of the outputs is stored for use as a feedback input during later iterations.
Claims27
An amplitude correction factor generator having a received signal input, an estimated signal-to-noise power ratio input, and a correction factor output, comprising:
- a received power estimator having a power estimator input operatively connected to the received signal input, and an estimated signal plus noise power output;
- a message signal power estimator having a signal plus noise power input operatively connected to the estimated signal plus noise power output, a message signal power input operatively connected to the estimated signal-to-noise power ratio input, and an estimated signal power output;
- and
- a scaling correction factor generator having an estimated signal power input operatively connected to the estimated signal power output and a scaling factor output operatively connected to the correction factor output.
An average signal-to-noise ratio (SNR) estimator having a scaled input and an estimated signal-to-noise power ratio output, comprising:
- a SNR maximum likelihood estimator having a scaled estimator input operatively coupled to the scaled input, and a maximum likelihood estimated output;
- a received likelihood detector having a scaled detector input operatively coupled to the scaled estimator input and the scaled input, a likelihood detector input operatively coupled to the maximum likelihood estimated output, and a received likelihood detector output;
- a running weighted averager having a detected averager input operatively coupled to the received likelihood detector output, an estimated averager input operatively coupled to the maximum likelihood estimated output and the likelihood detector input, and an estimated averager output;
- and
- a unit delay element having a unit delay input operatively coupled to the estimated averager output and a unit delay output operatively coupled to the estimated signal-to-noise power ratio output;
- wherein the SNR maximum likelihood estimator has an averaged estimator input, and wherein the unit delay output is operatively coupled to the averaged estimator input.
An average signal-to-noise ratio (SNR) estimator having a scaled input and an estimated signal-to-noise power ratio output, comprising:
- a SNR maximum likelihood estimator having a scaled estimator input operatively coupled to the scaled input, and a maximum likelihood estimated output;
- a received likelihood detector having a scaled detector input operatively coupled to the scaled estimator input and the scaled input, a likelihood detector input operatively coupled to the maximum likelihood estimated output, and a received likelihood detector output;
- a running weighted averager having a detected averager input operatively coupled to the received likelihood detector output, an estimated averager input operatively coupled to the maximum likelihood estimated output and the likelihood detector input, and an estimated averager output;
- and
- a unit delay element having a unit delay input operatively coupled to the estimated averager output and a unit delay output operatively coupled to the estimated signal-to-noise power ratio output;
- wherein the maximum likelihood estimated output is about equal to a preselected maximum Probability Distribution Function (PDF) lookup table value associated with the scaled input and the unit delay output.
A signal amplitude restoration apparatus having a received signal input and a scaled received signal output, comprising:
- an amplitude correction factor generator having a received signal input, an estimated signal-to-noise power ratio input, and a correction factor output;
- a variable gain amplifier having an amplifier input operatively coupled to the received signal input, a gain adjustment input operatively coupled to the correction factor output, and a scaled amplifier output operatively coupled to the scaled received signal output;
- and
- an average signal-to-noise ratio (SNR) estimator having a scaled input operatively connected to the scaled amplifier output and the scaled received signal output, and an estimated output operatively connected to the estimated signal-to-noise power ratio input.
A method of providing a correction factor output using a received signal input and an estimated signal-to-noise power ratio input, comprising the steps of:
- estimating a signal plus noise power output as approximately equal to a summation of the received signal input squared over a preselected time interval window;
- estimating a signal power output as approximately equal to a product of the signal plus noise power input and the estimated signal-to-noise power ratio input divided by a quantity of one plus the estimated signal-to-noise power ratio;
- and
- calculating the correction factor output as approximately inversely proportional to a square root of the signal power output.
A method of providing an average signal-to-noise ratio (SNR) estimate using a scaled input, comprising the steps of:
- estimating a SNR maximum likelihood output using the scaled input;
- determining a received likelihood detector output using the scaled input and the SNR maximum likelihood output;
- determining a new running weighted average using the received likelihood detector output and the SNR maximum likelihood output, wherein the new running weighted average makes use of a plurality of weight values, and wherein each one of the plurality of weight values is approximately equal to an incremental probability of the SNR maximum likelihood output raised to a preselected power;
- and
- storing the new running weighted average as the average SNR estimate;
- wherein the step of estimating a SNR maximum likelihood output using the scaled input includes the step of estimating the SNR maximum likelihood output using the stored running weighted average.
A method of providing a level-restored received signal output using a received signal input, a stored running weighted average, and a preselected receiver design power level, comprising the steps of:
- providing a correction factor output using the received signal input and the stored running weighted average;
- adjusting a gain of a variable gain amplifier having an amplifier input operatively connected to the received signal input, and a scaled amplifier output providing the level-restored received signal output;
- providing an average signal-to-noise ratio (SNR) estimate using the level-restored received signal output;
- and
- storing the average SNR estimate as a new running weighted average.
A receiver architecture, comprising:
- a signal amplitude restoration apparatus providing an amplitude-restored noisy signal from a receiver signal input, wherein the restoration apparatus comprises:
- an amplitude correction factor generator having a received signal input operatively connected to the receiver signal input, an estimated signal-to-noise power ratio input, and a correction factor output;
- a variable gain amplifier having an amplifier input operatively coupled to the received signal input, a gain adjustment input operatively coupled to the correction factor output, and a scaled amplifier output;
- and
- an average signal-to-noise (SNR) estimator having a scaled input operatively connected to the scaled amplifier output, and an estimated output operatively connected to the amplitude correction factor generator;
- a means for providing a local replica signal from the amplitude-restored noisy signal;
- a means for subtracting the local replica signal from the amplitude-restored noisy signal to produce an actual noise signal;
- and
- a means of down-converting the actual noise signal and the amplitude-restored noisy signal and combining them to provide a de-noised baseband signal.
Dependencies are inferred from the claim text.