Carrier recovery for spread spectrum communications

A method for controlling carrier recovery in a spread spectrum receiver comprising the steps of:

• a. providing a symbol clock corresponding to the reception of symbols in a spread spectrum symbol;
• b. providing a sample clock corresponding to the number of digital samples per symbol;
• c. adding phase error from a prior symbol to the phase error of a current symbol;
• d. providing a first accumulated output for each symbol at a symbol rate based on the accumulated phase error;
• e. dividing the phase error of the current symbol by a number of samples per symbol;
• f. providing a divided error signal at a sample rate based on the divided phase error;
• g. accumulating the divided error signal at the sample rate;
• h. providing a phase correction signal dependent on the accumulation of the divided error signal at the sample rate and the first accumulated output;
• and
• i. adjusting an operating frequency for carrier recovery on the phase correction signal.

In a spread spectrum receiver having complex mixer circuitry to remove the carrier frequency from a sampled received signal and despreading and coordinate conversion circuitry adapted to determine an actual phase associated with each symbol recovered from the received signal, carrier recovery control circuitry comprising:

• a. symbol determination circuitry adapted to receive the actual phase value associated with each recovered symbol and determine a ideal phase value corresponding to a most likely ideal symbol value;
• b. phase comparison circuitry adapted to receive the actual phase of each recovered symbol with the ideal phase value and provide a phase error signal corresponding to the difference between the actual and ideal phase values;
• and
• c. phase accumulation circuitry configured to receive a function of the phase error signal and provide a control signal for a variable oscillator, which controls the recovery frequency of the complex mixer circuitry, said phase accumulation circuitry comprising a first phase accumulator accumulating the phase error signal per symbol to provide a first accumulator output and a second phase accumulator accumulating the phase error per sample to provide the error control signal that is dependent on the first accumulator output and the accumulated phase error per sample, wherein the sample rate is the number of samples per symbol.

An apparatus for controlling carrier recovery in a spread spectrum receiver comprising:

• a. means for providing a symbol clock corresponding to the reception of symbols in a spread spectrum symbol;
• b. means for providing a sample clock corresponding to the number of digital samples per symbol;
• c. means for accumulating phase error from a prior symbol to the phase error of a current symbol;
• d. means for providing a first accumulated output for each symbol at a symbol rate based on the accumulated phase error;
• e. means for dividing the phase error of the current symbol by a number of samples per symbol;
• f. means for providing a divided error signal at a sample rate based on divided the phase error;
• g. means for accumulating the divided error signal at the sample rate;
• h. means for providing a phase correction signal dependent on the accumulation of the divided error signal at the sample rate and the first accumulated output;
• and
• i. means for adjusting an operating frequency for carrier recovery based of a received signal based on phase correction signal.