Bit pattern synchronization in acquired waveforms
View Patent ↗A waveform processing system performs operations that may include identifying a location of a specified bit pattern within a coherently sampled repeating pattern input signal. In some examples, multiple periods of a repeating pattern signal are acquired using coherent sampling techniques such as, for example, coherent interleaved sampling (CIS). In such examples, the sampled waveform may be converted to a binary pattern that can be searched to locate a match to a predetermined or user-specified bit pattern. In one illustrative example, the identified location may be used to display the sampled waveform. In another example, the identified location may be used to measure pattern-dependent jitter of the sampled waveform.
1. A method to process a signal with repeating information having a time period of repetition, the method comprising the steps of:
receiving a synchronizing signal having a frequency substantially equal to or sub-harmonically related to a bit rate of the signal being processed and substantially synchronous with a bit phase of the signal being processed;
synchronizing a phase-locked loop to the synchronizing signal;
sampling the signal being processed over multiple periods of the repeating information to produce a sampled waveform, the sampling being performed in accordance with the synchronizing signal;
post-processing the sampled waveform to form a coherently sampled waveform representing one period of the repeating information; identifying a location within the coherently sampled waveform at which a portion thereof matches a desired binary sequence;
synchronizing, though rotation of the coherently sampled waveform, so that the identified location is positioned at a location representative of a predetermined time within the time period of repetition; and
measuring pattern dependent jitter in accordance with the synchronized portions of the formed coherently sampled waveform.
2. The method of claim 1 , further comprising displaying at least a portion of the synchronized coherently sampled waveform.
3. The method of claim 1 , further comprising storing in a data store information about the identified location.
4. The method of claim 1 , further comprising selecting a portion of the synchronized coherently sampled waveform based on the identified location.
5. The method of claim 4 , further comprising displaying on a display device the selected portion of the synchronized coherently sampled waveform.
6. The method of claim 1 , wherein processing the waveform comprises digitizing the sampled waveform.
7. The method of claim 1 , wherein the sampled waveform is processed using information about the length of the time period of repetition.
8. The method of claim 1 , wherein the desired binary sequence comprises at least one don't care bit.
9. The method of claim 1 , wherein the waveform being processed comprises a pseudo-random binary sequence (PRBS).
10. A method to process a signal with repeating information having a time period of repetition, the method comprising the steps of:
receiving a synchronizing signal having a frequency substantially equal to or sub-harmonically related to a bit rate of the signal being processed and substantially synchronous with a bit phase of the signal being processed;
synchronizing a phase-locked loop to the synchronizing signal;
sampling the signal being processed over multiple periods of the repeating information to produce a sampled waveform, the sampling being performed in accordance with the synchronizing signal:,
post-processing the sampled waveform to form a coherently sampled waveform representing one period of the repeating information; identifying a location within the coherently sampled waveform at which a portion thereof matches a desired binary sequence;
synchronizing, though rotation of the coherently sampled waveform, so that the identified location is positioned at a location representative of a predetermined time within the time period of repetition; and
displaying at least a portion of the coherently sampled waveform relative to the synchronized portions of the desired binary sequence.
11. The method of claim 10 , further comprising the step of measuring pattern dependent jitter based on the synchronized portions of the formed coherently sampled waveform.
12. A waveform processing system comprising:
an acquisition module to acquire samples of an input signal for a plurality of periods of a repeating binary pattern in the input signal, the acquisition being performed in accordance with a synchronizing signal having a frequency substantially equal to or sub-harmonically related to a bit rate of the input signal and substantially synchronous with a bit phase of the input signal;
a processor operatively coupled to post-process data representing the acquired samples; and
a memory containing instructions that, when executed by the processor, cause operations to be performed, the operations comprising:
synchronizing a phase-locked loop to the synchronizing signal;
sampling the input signal over multiple periods of the repeating binary pattern to produce a sampled waveform, the sampling being performed in accordance with the synchronizing signal;
processing the sampled waveform to form a coherently sampled waveform representing one period of the repeating binary pattern;
identifying a location within the sampled waveform at which a portion thereof matches a desired binary sequence;
synchronizing, though rotation of the sampled waveform, so that the identified location is positioned at a location representative of a predetermined time within the time spanned by a single repetition of the repeating binary pattern; and
performing at least one of the following two operations: (1) measuring pattern dependent jitter based on the synchronized portions of the formed binary pattern; and, (2) displaying at least a portion of the sampled waveform relative to the synchronized portions of the binary pattern.
13. The system of claim 12 , further comprising selecting a portion of the formed binary sequence in accordance with the identified location.
14. The system of claim 12 , further comprising a digital storage oscilloscope that includes the acquisition module.