Timing synchronization in a communication device

A method for performing timing synchronization between digital input data and a system clock in a communication device, the method comprising the steps of:

• (a) providing a system clock rate that is higher than a data clock rate, the system clock providing a plurality of system clock periods per one data clock period;
• (b) sampling the input data at periodic intervals in the system clock periods within the data clock period;
• (c) adjusting the timing between the digital input data and the system clock such that
• (d) advancing the timing of the input data in relation to the system clock includes the substeps of:
• (d1) shortening the number of system clock periods in relation to the data clock period, and shortening the sampling intervals;
• (d2) sampling the input data at the shortened intervals defined in the previous step, and
• (e) delaying the timing of the input data in relation to the system clock includes the substeps of:
• (e1) lengthening the number of system clock periods in relation to the data clock period;
• (e2) sampling the input data at normal intervals and performing an extra data insertion to fill one of the extra system clock periods, such that more data samples are provided in the data clock period;
• (f) outputting the sampled input data for the data clock period;
• and
• (g) interpolating the data samples from the previous step to smooth the output data.

An apparatus to provide timing synchronization of digital input data in a communication device, the apparatus comprising:

• a system clock that has a system clock rate that is higher than a data clock rate of the digital input data, the system clock providing a plurality of system clock periods per one data clock period;
• a first filter coupled with the system clock, the first filter samples the input data at intervals of the system clock periods and increases the sample rate of the input data by performing data insertion, the first filter operates on the resultant data with a first set of filter coefficients to provide an output;
• and
• a second filter coupled with the system clock, the second filter increases the sample rate of the output from the first filter, the second filter samples data and provides data insertion dependent on a desired timing adjust, wherein
• when a timing advance is desired, the first filter shortens the number of system clock periods in relation to the data clock period, and shortens the sampling intervals, and wherein the second filter samples the data output from the first filter with a reduced number of data insertion periods and operates on the resultant data with a second set of filter coefficients, and
• when a timing delay is desired, the first filter lengthens the number of system clock periods in relation to the data clock period, and performs an extra data insertion to fill one of the extra system clock periods, such that more samples are output in the data clock period, and wherein the second filter obtains the output from the first filter and operates on the resultant data with a second set of filter coefficients.

A timing filter that provides timing synchronization of digital input data in a communication device, the apparatus comprising:

• a system clock that has a system clock rate that is higher than a data clock rate of the digital input data, the system clock providing a plurality of system clock periods per one data clock period;
• a first filter coupled with the system clock, the first filter samples the input data at periodic intervals of the system clock periods and increases the sample rate of the input data by performing data insertion, the first filter operates on the resultant data with a first set of filter coefficients to provide an output;
• and
• an interpolation filter coupled with the system clock, the interpolation filter samples the output from the first filter, the interpolation filter samples data and provides data insertion dependent on a desired timing adjust, wherein
• when a timing advance is desired, the first filter shortens the number of system clock periods in relation to the data clock period, and shortens the sampling intervals, and wherein the interpolation filter samples the data output from the first filter with a reduced number of data insertion periods and operates on the resultant data with a second set of filter coefficients and interpolates to smooth the results, and
• when a timing delay is desired, the first filter lengthens the number of system clock periods in relation to the data clock period, and performs an additional data insertion to fill one of the extra system clock periods, such that more data samples are output in the data clock period, and wherein the interpolation filter obtains the output from the first filter and operates on the output with a second set of filter coefficients and interpolates to smooth the results.