US 6,473,471 B2 · Slope drift and offset compensation in zero-if receivers

Abstract

A method for processing a signal modulated with information symbols to account for an additive offset and slope is disclosed. First, an initial estimate of offset and slope is made and hypotheses of all possible values of a sequence of one or more information symbols are then made. For each of said hypotheses, the associated data symbol sequence is used to make an improved estimate of offset and slope and the improved estimate of offset and slope are stored against each of the hypotheses. For each hypothesis, the improved estimate of offset and slope is used in calculating an expected signal value and a mismatch between a sample of the modulated signal and the expected value is computed. The hypotheses are then sequentially extended by one symbol, the slope and offset estimates are updated and the mismatches are accumulated to form a path metric value for each extended hypothesis, and resolving between said hypotheses based on said path metric values using a Viterbi Sequential Maximum Likelihood Sequence Estimation process to produce a most likely hypothesis of said modulated information symbols substantially unimpaired by said additive slope and offset.

Claims15

Dependent claims

An improved radio receiving apparatus for direct conversion of signals to a baseband for processing, comprising:

direct conversion means for converting a radio input signal to a complex baseband signal having a real waveform and an imaginary waveform;
and
slope and offset compensation means for estimating offsets and systematic drifts in said real and imaginary waveforms and compensating for said drifts and offsets such that decoding of information modulated on said radio input signal is substantially unimpaired, said slope and offset compensation means comprising:
integrating capacitors which are driven to follow the input real and imaginary waveforms by a charge or discharge current pulse from charge pumps;
comparator means for comparing the real and imaginary waveforms with a voltage on said integrating capacitors to generate a positive/negative indication;
processing means for determining correction values for said real and imaginary waveforms wherein said correction values are used to select current magnitudes to be applied to said charge pumps, said current magnitudes being stored in one of register pairs and pairs of memory positions and said current magnitudes, for each pair of said one of register pairs and pairs of memory positions, are independent for positive and negative stepsign.

3 more elements

Dependencies are inferred from the claim text.

Slope drift and offset compensation in zero-if receivers

Life of this patent

Slope drift and offset compensation in zero-if receivers

Life of this patent

Abstract

Claims15