Self-correcting multirate filter

A system that enables real time configuration of a resampling filter to sample a data stream, the system comprising:

• a polyphase multirate filter having a plurality of individually selectable polyphase filter components for filtering input data to generate an output data sample,;
• and
• a controller of the polyphase multirate filter which, responsive to detecting a data stream:
• measures a current phase relationship between a current resampling filter input clock signal and a current multirate output clock signal;
• identifies an initial polyphase filter coefficient index corresponding to the measured phase relationship using a mapping of the measured phase relationship within a pre-generated quantized mapping table, wherein the pre-generated quantized mapping table comprises an association of each of a plurality of sets of different values of measured phase relationships with one initial polyphase filter coefficient index that identifies a particular polyphase filter component of the multirate filter, and wherein the multirate filter comprises a plurality of polyphase filter components each uniquely identified by a different polyphase filter coefficient index and each capable of being individually selected to generate a different output data sample from processing received data;
• selects a corresponding polyphase filter component from within the multirate filter using the initial polyphase filter coefficient index identified;
• configures the multirate filter to pass data from the data stream through the corresponding polyphase filter component, wherein the corresponding polyphase filter component selected generates an initial output data sample from data of the data stream inputted to the multirate filter, and wherein the initial output data sample is derived utilizing sampling functions specific to that corresponding polyphase filter component;
• and
• in response to a request for generation of a next output data sample, updates the initial polyphase filter coefficient index to a calculated next polyphase filter coefficient index value.

A radio frequency (RF) communication device comprising:

• an RF module;
• a baseband modem coupled to the RF module;
• a polyphase multirate filter having a plurality of individually selectable polyphase filter components module and which communicates outgoing data from and incoming data to the baseband modem, wherein the polyphase multirate filter is located within one of (a) the RF module, and (b) a baseband front end;
• a controller of the polyphase multirate filter which, responsive to detecting a data stream:
• measures a current phase relationship between a current resampling filter input clock signal and a current multirate output clock signal by measuring a time interval between a first rising edge of the resampling filter input clock signal and a first rising edge of the multirate output clock signal using a measuring clock signal that is faster than both the resampling filter input clock signal and the multirate output clock signal, wherein the time interval is measured in units of full signal counts of the measuring clock signal, and wherein a total number of the full signal counts of the measuring clock within the time interval is mapped within a pre-generated quantized mapping table to one initial polyphase filter coefficient index, and each polyphase filter coefficient index is uniquely mapped to a set of one or more different numbers of signal counts of the faster measuring clock signal, wherein when the data stream is a data transmission stream generated by the communication device, the current resampling filter input clock signal and the current multirate output clock signal respectively represent the baseband modem clock signal and an RF sampling clock signal of the RF module, and wherein when the data stream is a data receiving stream received by the communication device, the current resampling filter input clock signal and the current multirate output clock signal respectively represent the RF sampling clock signal and the baseband modem clock signal;
• identifies an initial polyphase filter coefficient index corresponding to the measured phase relationship using a mapping of the measured phase relationship within the pre-generated quantized mapping table, wherein the pre-generated quantized mapping table comprises an association of each of a plurality of sets of different values of measured phase relationships with one initial polyphase filter coefficient index that identifies a particular polyphase filter component of the multirate filter, and wherein the multirate filter comprises a plurality of polyphase filter components each uniquely identified by a different polyphase filter coefficient index and each capable of being individually selected to generate a different output data sample from processing received data;
• selects a corresponding polyphase filter component from within the multirate filter using the initial polyphase filter coefficient index identified;
• configures the multirate filter to pass data from the data stream through the corresponding polyphase filter component, wherein the corresponding polyphase filter component selected generates an initial output data sample from data of the data stream inputted to the multirate filter, and wherein the initial output data sample is derived utilizing sampling functions specific to that corresponding polyphase filter component;
• in response to a request for generation of a next output data sample, updates the initial polyphase filter coefficient index to a calculated next polyphase filter coefficient index value;
• in response to a detection of at least one pre-identified trigger condition that indicates at least one of (a) a change in a timing relationship between the resampling filter input clock signal and the multirate output clock signal and (b) an error resulting from one of the initial polyphase coefficient index selected and the next polyphase filter coefficient index value calculated, self-corrects the multirate filter by adjusting the next polyphase filter coefficient index value to a new polyphase filter coefficient index value within a pre-set range of acceptable polyphase filter coefficient index values, wherein the adjusting to the new polyphase filter coefficient index value includes:
• performing a new measurement of the phase relationship;
• and selecting a new initial polyphase filter coefficient index from a newly selected quantized mapping table that provides mappings derived from a measured timing relationship of a similar resampling filter input clock signal and a similar multirate output clock signal as a newly-determined current filter input clock signal and a newly-determined multirate output clock signal, utilizing a same measurement clock.