Abstract: A method of splitting a signal (10) into two parts (10?, 10?) is disclosed together with signal processing circuitry (22) for the same. The method comprises the steps of derotating the signal (10) whereby the frequency band of the derotated signal overlaps zero frequency; and splitting the derotated signal into two parts, a first signal part (10?) consisting substantially of positive frequency signal components and a second signal part (10?) consisting substantially of negative frequency signal components. Also disclosed is methods, incorporating such a method of splitting a signal, for identifying the presence of in-band interference (11) in a signal and for despreading a spread spectrum signal.

Abstract: A method of code phase tracking for CDMA type communication is disclosed together with apparatus including a GPS receiver (10 to 15) for the same. The method uses a modified early-minus-late correlation function to determine the code phase error between a target pseudorandom noise code of an incoming signal and locally generated replica codes. The early-minus-late correlation function is modified compared to the true function whereby the gradient of the modified function at zero code phase error is increased. This may be achieved my modifying the early-minus-late correlation function after its derivation.

Abstract: A method of correlating first and second digital signals which both contain series of numerical data values is disclosed together with a computer program, a computer-readable storage medium) and apparatus for the same. The method includes the steps of (a) sequentially calculating products of corresponding numerical data values of the first and second digital signals and providing a cumulative sum thereof; (b) upon deviation of the cumulative sum from between upper and lower thresholds levels, increasing or decreasing the cumulative sum by a predetermined amount so as to return the cumulative sum to between said threshold levels; and (c) providing a correlation parameter as a function of the number of occurrences of deviation of the cumulative sum from between upper and lower thresholds. The correlation parameter may either increase or decrease depending on whether the cumulative sum deviates above the upper threshold level or below the lower threshold level.

Abstract: A method of splitting a signal (10) into two parts (10″, 10′) is disclosed together with signal processing circuitry (22) for the same. The method comprises the steps of derotating the signal (10) whereby the frequency band of the derotated signal overlaps zero frequency; and splitting the derotated signal into two parts, a first signal part (10″) consisting substantially of positive frequency signal components and a second signal part (10′) consisting substantially of negative frequency signal components. Also disclosed is methods, incorporating such a method of splitting a signal, for identifying the presence of in-band interference (11) in a signal and for despreading a spread spectrum signal.

Abstract: A method of code phase tracking for CDMA type communication is disclosed together with apparatus including a GPS receiver (10 to 15) for the same. The method uses a modified early-minus-late correlation function to determine the code phase error between a target pseudorandom noise code of an incoming signal and locally generated replica codes. The early-minus-late correlation function is modified compared to the true function whereby the gradient of the modified function at zero code phase error is increased. This may be achieved my modifying the early-minus-late correlation function after its derivation.

Abstract: A method of correlating first and second digital signals which both contain series of numerical data values is disclosed together with a computer program, a computer-readable storage medium (24) and apparatus (21) for the same. The method comprising the steps of (a) sequentially calculating products of corresponding numerical data values of the first and second digital signals and providing a cumulative sum thereof; (b) upon deviation of the cumulative sum from between upper and lower thresholds levels, increasing or decreasing the cumulative sum by a predetermined amount so as to return the cumulative sum to between said threshold levels; and (c) providing a correlation parameter as a function of the number of occurrences of deviation of the cumulative sum from between upper and lower thresholds. The correlation parameter may either increase or decrease depending on whether the cumulative sum deviates above the upper threshold level or below the lower threshold level.