Digital timing correction system, method and apparatus
View Patent ↗The method and system of digital timing correction in a digital baseband communication system is disclosed. In one embodiment, a method includes receiving samples at a predetermined time interval based on a current clock signal of a receiver clock, reading in a prompt sample of the received samples and a successor sample of the received samples based on a control signal, interpolating a projected sample based on the prompt sample, the successor sample and a predetermined time offset, determining the time offset for interpolation, by accumulating sampling frequency offset between the receiver clock and a reference clock, relative to a sample timing of the prompt sample, resulting in an interpolated data sample rate reduced by an integer multiple factor compared to a received sample rate and receiving a next sample of the received samples based on the current clock signal of the receiver clock.
1. A method, comprising:
receiving samples at a predetermined time interval through a series connected delay elements based on a current clock signal of a receiver clock;
strobing in a prompt sample and a successor sample from output of each of the series connected delay elements for interpolation based on a control signal, wherein the control signal is generated by:
determining a time offset for interpolation, by accumulating sampling frequency offset between the receiver clock and a reference clock, relative to a sample timing of the prompt sample;
if the accumulated time offset is less than the sample timing of the prompt sample, generating the control signal to strobe one clock earlier than the normally generated control signal;
else if the accumulated time offset is greater than the sample timing of the successor sample, generating the control signal to strobe one clock later than the normally generated control signal;
else normally generating the control signal to strobe at an integer multiple of the current clock signal of the receiver clock;
interpolating a projected sample based on the prompt sample, the successor sample and the predetermined time offset with an interpolated data sample rate reduced by an integer multiple factor compared to a received sample rate; and
receiving in a next sample of the received samples through the series connected delay elements based on the current clock signal of the receiver clock.
2. The method of claim 1 , further comprising:
applying a simple linear interpolation to obtain the projected sample.
3. The method of claim 2 , wherein the simple linear interpolation to obtain the projected sample comprises:
y ( nT S )= x ( nT S )+μ·( x (( n+ 1) T S )− x ( nT S ))
wherein x is the received sample, y(nTs) is the projected sample sampled at time index n, x(nTs) is the prompt sample sampled at time index n, x(n+1)Ts is the successor sample sampled at time index n+1, and μ is the predetermined time offset between y (nTs) and x (nTs).
4. The method of claim 3 , wherein:
if a μ value is less than 0, generating the control signal to strobe one clock earlier than the normally generated control signal and adding 1 to the μ value;
else if the μ value is greater than 1, generating the control signal to strobe one clock later than the normally generated control signal and subtracting 1 from the μ value; and
else normally generating the control signal to strobe at an integer multiple of the current clock signal of the receiver clock.
5. The method of claim 1 , further comprising:
applying a higher order interpolation to obtain the projected sample.
6. The method of claim 1 , further comprising:
strobing in a next prompt sample and a next successor sample from the output of the series connected delay elements based on the control signal.
7. A non-transitory computer readable medium embodying a set of instructions that, when executed by a computer, causes the computer to perform the method of claim 1 .
8. A system, comprising:
a receiver module having a receiver clock to receive samples at a predetermined time interval through a series connected delay elements based on a current clock signal of the receiver clock and to strobe in a prompt sample and a successor sample from output of each of the series connected delay elements for interpolation based on a control signal, wherein the receiver module comprises:
a controller module to generate the control signal, wherein the controller module is configured to:
determine a time offset for interpolation, by accumulating sampling frequency offset between the receiver clock and a reference clock, relative to a sample timing of the prompt sample;
determine if the accumulated time offset is less than the sample timing of the prompt sample and, if the accumulated time offset is less than the sample timing of the prompt sample, to generate the control signal to strobe one clock earlier than the normally generated control signal;
determine if the accumulated time offset is greater than the sample timing of the successor sample and, if the accumulated time offset is greater than the sample timing of the successor sample, to generate the control signal to strobe one clock later than the normally generated control signal;
else to normally generate the control signal to strobe at an integer multiple of the current clock signal of the receiver clock; and
an interpolation module to interpolate a projected sample based on the prompt sample, the successor sample and the predetermined time offset with an interpolated data sample rate reduced by an integer multiple factor compared to a received sample rate,
wherein the receiver module to receive in a next sample of the received samples through the series connected delay elements based on the clock signal of the receiver clock.
9. The system of claim 8 , wherein the interpolation module further applies a simple linear interpolation to obtain the projected sample.
10. The system of claim 9 , wherein the simple linear interpolation to obtain the projected sample comprises:
y ( nT S )= x ( nT S )+μ·( x (( n+ 1) T S )− x ( nT S ))
wherein x is the received sample, y(nTs) is the projected sample sampled at time index n, x(nTs) is the prompt sample sampled at time index n, x(n+1)Ts is the successor sample sampled at time index n+1, and μ is the predetermined time offset between y (nTs) and x (nTs).
11. The system of claim 10 , wherein:
if a μ value is less than 0, the control signal is generated to strobe one clock earlier than the normally generated control signal and 1 is added to the μ value;
else if the μ value is greater than 1, the control signal is generated to strobe one clock later than the normally generated control signal and 1 is subtracted from the μ value; and
else the control signal is generated normally to strobe at the integer multiple of the current clock signal of the receiver clock.
12. The system of claim 8 , wherein the interpolation module further applies a higher order interpolation circuit to obtain the interpolation of the projected sample.
13. The system of claim 8 , wherein the receiver module further strobes in a next prompt sample and a next successor sample from the output of the series connected delay elements based on the control signal.
14. A control circuit, comprising:
a controller to strobe in a prompt sample and a successor sample from output of each of a series connected delay elements for interpolation based on a control signal, wherein the controller generates the control signal, wherein the controller module is configured to:
to determine the time offset for interpolation, by accumulating sampling frequency offset between a receiver clock and a reference clock, relative to a sample timing of the prompt sample;
to determine if the accumulated time offset of the projected sample is less than a sample timing of the prompt sample or greater than a sample timing of the successor sample; and
to generate the control signal to strobe one clock earlier than the normally generated control signal if the accumulated time offset is less than the sample timing of the prompt sample;
to generate the control signal to strobe one clock later than the normally generated control signal if the accumulated time offset is greater than the sample timing of the successor sample;
else to normally generate the control signal to strobe at an integer multiple of the current clock signal of the receiver clock; and
an interpolation block to obtain a projected sample based on the prompt sample, the successor sample, and the predetermined time offset, wherein the controller strobes in a next prompt sample and a next successor sample from the output of the series connected delay elements based on the control signal.
15. The control circuit of claim 14 , wherein the interpolation block further applies a simple linear interpolation to obtain the projected sample.
16. The control circuit of claim 14 , wherein the simple linear interpolation to obtain the projected sample comprises:
y ( nT S )= x ( nT S )+μ·( x (( n+ 1) T S )− x ( nT S ))
wherein x is the received sample, y(nTs) is the projected sample sampled at time index n, x(nTs) is the prompt sample sampled at time index n, x(n+1)Ts is the successor sample sampled at time index n+1, and μ is the predetermined time offset between y(nTs) and x(n)Ts.
17. The control circuit of claim 16 , wherein:
if a μ value is less than 0, the control signal is generated one clock earlier than the normally generated control signal and 1 is added to the μ value;
else if the μ value is greater than 1, the control signal is generated one clock later than the normally generated control signal and 1 is subtracted from the μ value; and
else the control signal is generated normally at an integer multiple of the current clock signal of the receiver clock.
18. The control circuit of claim 14 , wherein the interpolation block further applies a higher order interpolation circuit to obtain interpolation of the projected sample.
19. A control circuit, comprising:
a controller to strobe in a prompt sample and a successor sample from output of each of a series connected delay elements for interpolation based on a control signal; and
an interpolation block to interpolate according to:
y ( nT S )= x ( nT S )+μ·( x (( n+ 1) T S )− x ( nT S ))
wherein x is the received sample, y(nTs) is a projected sample sampled at time index n, x(nTs) is the prompt sample sampled at time index n, x(n+1)Ts is the successor sample sampled at time index n+1, and μ is a predetermined time offset between y(nTs) and x(nTs), and to determine if a μ value is less than 0 or greater than 1;
wherein the controller generates the control signal one clock earlier than the normally generated control signal if the μ value is less than 0 and to add 1 to the μ value;
wherein the controller generates the control signal one clock later than the normally generated control signal if the μ value is greater than 1 and to subtract 1 from the μ value;
else the controller generates the control signal at an integer multiple of the current clock signal of the receiver clock; and
wherein the controller to strobe in a next prompt sample and a next successor sample from the output of the series connected delay elements based on the control signal.