Sampling rate converter data flow control mechanism
View Patent ↗A sampling rate converter that converts an incoming stream of data, clocked at a first frequency, to an output stream of data that can be clocked at a second frequency is described. The sampling rate converter up-samples an incoming data stream, filters the up-sampled incoming data stream, interpolates the filtered up-sampled data stream, and then stores the interpolated filtered up-sampled incoming data stream in a FIFO at the first frequency. The interpolated filtered up-sampled data can then be read from the FIFO at the second frequency. A control block that includes a numerically controlled oscillator (NCO) that generated the first frequency is provided. Control of the NCO's production of the first frequency is based on the status of the FIFO, how the data stream is modulated, and the sampling rate ratio of the incoming data stream with respect to the output or read rate of data stream.
1. A sampling rate converter for performing a sampling rate conversion of an incoming stream of data clocked at a first frequency and output at a second frequency; the converter comprising:
an up-sampling circuit adapted to up-sample the incoming data stream;
a filter adapted to filter the up-sampled incoming data stream;
an interpolation filter adapted to interpolate the filtered up-sampled incoming stream of data;
a FIFO adapted to store the interpolated filtered up-sampled incoming stream of data (the IFUI stream of data), the FIFO being adapted to store the IFUI stream of data at the first frequency and being further adapted to enable reading of the IFUI stream of data from the FIFO at the second frequency so as to output the stored IFUI stream of data at a second corresponding rate;
a control block comprising a numerically controlled oscillator (NCO) wherein the NCO is adapted to generate the first frequency; and wherein control of the NCO is based on information representative of the status of the FIFO, information representative of the modulation of the stream of data, and a ratio of sampling rate change between the incoming stream of data and output stream of data.
2. The sampling rate converter according to claim 1 , wherein the information representative of the modulation of the stream of data is derived from a count, during a predetermined period, of a number of quadrants passed by a vector corresponding to a modulated symbol of a wireless telecommunication protocol.
3. The sampling rate converter according to claim 2 , wherein the predetermined period corresponds to a set of 50 symbols to be modulated.
4. The sampling rate converter according to claim 1 , wherein the interpolation filter is based on dynamic interpolation.
5. The sampling rate converter according to claim 1 , wherein the interpolation filter is based on static interpolation.
6. The sampling rate converter according to claim 1 , wherein the interpolation filter is based on a linear interpolation filter of a first order, combined with a 4× up-sampling.
7. The sampling rate converter according to claim 1 , wherein the sampling rate converter is integrated into a transmission circuit of a User Equipment for a wireless telecommunication network.
8. A mobile communication device comprising a transmission circuit wherein the transmission circuit comprises sampling rate converter adapted to perform a sampling rate conversion of an incoming data stream clocked at a first frequency and an output stream of data clocked at a second frequency; the converter comprising:
an up-sampling circuit adapted to up-sample the incoming data stream;
a filter adapted to filter the up-sampled incoming data stream;
an interpolation filter adapted to interpolate the filtered up-sampled incoming data stream data;
a FIFO adapted to store the interpolated filtered up-sampled incoming data stream (the IFUI data stream), the FIFO being adapted to store the IFUI data stream at the first frequency and being further adapted to enable reading of the IFUI data stream from the FIFO at the second frequency so as to output the stored IFUI data stream at a second corresponding rate;
a control block comprising a numerically controlled oscillator (NCO) wherein the NCO is adapted to generate the first frequency; and wherein control of the NCO is based on information representative of FIFO status, representative of the modulation of the data stream, and representative of a sampling rate ratio of the sampling rate of the incoming data stream and the output data stream.
9. A process of performing a sampling rate conversion of an incoming data stream clocked at a first frequency and then output as an output data stream at a second frequency; the process comprising:
up-sampling the incoming data stream;
filtering the up-sampled incoming data stream;
interpolating the filtered up-sampled incoming data stream;
storing, into a FIFO, the interpolated filtered up-sampled incoming data stream (IFUI data stream), said storing being performed at the first frequency and the reading of said FIFO being performed at the second frequency so as to output the stored data at a second corresponding rate;
controlling a numerically controlled oscillator (NCO) used to generate the first frequency based on information representative of a status of said FIFO, a modulation of the incoming data stream, and a ratio of the incoming data stream and the output data stream sampling rate change.
10. The process according to claim 9 , wherein the information representative of the modulation of the incoming data stream is derived from a count, during a predetermined period, of a number of quadrants that pass by a vector corresponding to a modulated symbol.
11. The process according to claim 10 , wherein the predetermined period corresponds to a set of 50 symbols to be modulated.
12. The process according to claim 9 , wherein the interpolation filter is based on dynamic interpolation or static interpolation.
13. The process according to claim 9 , wherein the interpolation filter is on a linear interpolation filter of a first order, combined with a 4× up-sampling.
14. The process according to claim 9 , wherein the process is used in a transmission circuit of a User Equipment for a wireless telecommunication network.