System and method for signal resampling
An instrument configured to process signal data is disclosed. The instrument is operable to control and or change the sampling rate of the signal data from a first sample rate to a second sample rate different than the first sample rate.
1. An instrument configured to process first signal data, the instrument comprising:
an input adapted to receive the first signal data, the first signal data having a first sample rate; and
a controller connected to the input, the controller comprising:
a shaping filter adapted to receive the first signal data from the input and transform, using a shaping function, the first signal data into second signal data having a second sample rate different than the first sample rate; and
a timing controller adapted to control timing of the shaping filter using a dual-modulus counter,
wherein the dual-modulus counter comprises a Multi-stAge noise Shaping Digital Delta-Sigma Modulator (MASH DDSM).
2. The instrument of claim 1 , wherein the timing controller is adapted to output valid, address and time residual signals to the shaping filter to control timing of the filter output and kernel interpolation.
3. The instrument of claim 2 , wherein an impulse response of the filter comprises a windowed sinc function.
4. The instrument of claim 2 , wherein the filter comprises:
a plurality of first memories, each comprising filter kernel values stored for each zero-crossing or tapped delay output of the filter;
a plurality of second memories, each comprising values used for the interpolation of the filter kernel, the first and second memories being accessed using the address signal from the timing controller; and
combining logic inputting the time residual signal from the timing controller and using filter kernel values from the first memories and values from the second memories to interpolate filter coefficients to be applied to the input first signal data to form the second signal data having the second sample rate rate according to an assertion of control signals from the timing controller state machine.
5. An instrument configured to process first signal data, the instrument comprising:
an input adapted to receive the first signal data, the first signal data having a first sample rate; and
a controller connected to the input, the controller comprising:
a shaping filter adapted to receive the first signal data from the input and transform, using a shaping function, the first signal data into second signal data having a second sample rate different than the first sample rate; and
a timing controller adapted to control timing of the shaping filter using a dual-modulus counter,
wherein the timing controller further comprises a state machine and the dual-modulus counter comprises a Multi-stAge noise Shaping Digital Delta-Sigma Modulator (MASH DDSM) connected to the state machine, the MASH DDSM comprising:
a plurality of cascaded error feedback modulators (EFMs), each error feedback modulator (EFM) feeding a noise shaping network;
the noise shaping network adapted to cancel the quantization error of the preceding EFM while shaping the quantization error of the final EFM according to a highpass filter response, the output of which represents the fractional component of the resampling rate; and
a timing accumulator that accumulates the integer and fractional components of the desired resampling rate used to derive control signals to a state machine.
6. The instrument of claim 5 , wherein each EFM comprises a modulo-B accumulator having a carry out bit, wherein B is a programmable integer value.
7. The instrument of claim 5 , wherein the noise shaping network comprises cascaded differentiators, which are adapted to cancel quantization noise from the EFMs.
8. An instrument configured to process first signal data, the instrument comprising:
an input port adapted to receive the first signal data, the first signal data having a first sample rate; and
control logic electrically connected to the input port, the control logic comprising:
a filter adapted to receive the first signal data from the input port and transform, using a filter function, the first signal data into second signal data having a second sample rate different than the first sample rate; and
a timing controller adapted to control timing and interpolation of the filter using a Multi-stAge noise Shaping Digital Delta-Sigma Modulator (MASH DDSM).
9. The instrument of claim 8 , wherein the timing controller further comprises a state machine and the MASH DDSM is connected to the state machine, and the MASH DDSM comprises:
a plurality of cascaded error feedback modulators (EFMs), each error feedback modulator (EFM) outputting a portion of a timing control signal; and
a noise shaping network adapted to receive the portions of the timing control signal from the EFMs and to output a combined control signal to the state machine.
10. The instrument of claim 9 , wherein each EFM comprises a modulo-B accumulator and comprises a feedback loop adapted to compute a difference between an input signal and a previous quantized output signal followed by a discrete integrator or accumulator, where B is an integer.
11. The instrument of claim 9 , wherein the noise shaping network comprises cascaded differentiators, which are adapted to cancel quantization noise from the EFMs.
12. The instrument of claim 9 , wherein the shaping function of the shaping filter comprises a windowed sinc function.
13. The instrument of claim 9 , wherein the shaping filter comprises:
a plurality of first memories, each comprising filter kernel values stored for each zero-crossing;
a plurality of second memories, each comprising difference values, the first and second memories being accessed using the address signal from the timing controller; and
combining logic inputting the time_residual signal from the timing controller and using filter kernel values from the first memories and difference values from the second memories to create filter coefficients to be applied to the input first signal data to form the second signal data having the second sample rate when the valid signal from the timing controller is indicative of a time to resample the input first signal data.
14. A method of processing first signal data, the first signal data having a first sample rate, said method comprising:
inputting, at port of an input device, the first signal data;
applying the first signal data to a shaping filter adapted to transform, using a shaping function, the first signal data into second signal data having a second sample rate different than the first sample rate; and
controlling a timing of the shaping filter using a dual-modulus counter,
wherein the dual-modulus counter comprises a Multi-stAge noise Shaping Digital Delta-Sigma Modulator (MASH DDSM).
15. The method of claim 14 , wherein the first signal data is input in real time from a source generating a waveform with the first signal data.
16. The method of claim 14 , wherein the shaping function of the shaping filter comprises a windowed sinc function.