Coded data generation or conversion – Digital code to digital code converters – Data rate conversion
Reexamination Certificate
2003-03-19
2004-07-27
Tokar, Michael (Department: 2819)
Coded data generation or conversion
Digital code to digital code converters
Data rate conversion
C345S182000
Reexamination Certificate
active
06768430
ABSTRACT:
TECHNICAL FIELD
This invention relates to signal sampling and more particularly to a system and method for adjusting the sampling rate for repetitive signals.
BACKGROUND
A long-running trend in communication and other systems is the use of higher and higher signal frequencies. As signal frequency is increased, the difficulty of characterizing a signal by measuring its time history also increases, to the point that direct acquisition is impractical. However, if the signal of interest is repetitive, its time history can be established by a process known as subsampling, wherein the signal is sampled at a rate that is below the Nyquist sampling frequency for the signal.
For subsampling, the sample rate is chosen such that each successive sample follows the previous sample by some number of signal repetitions plus some time increment. If the time increment is small compared with the period of signal repetition, then the sequence of samples will be a fine-grained time history of the signal, where the equivalent time resolution is equal to the selected time increment. For a repetitive signal, the sequence of samples is identical to that which would be obtained by sampling the signal at a time interval equal to the equivalent time resolution. The sample sequence can be displayed in real-time with a conventional oscilloscope.
Subsampling at a fixed sample rate is only applicable to particular signal repetition rates. Other repetition rates require changes to the sample frequency, and/or the ability to store and reorder the samples.
Digital communications systems, among others, typically utilize binary data streams with fixed data rates. However, it is often desirable to employ test signals of various pattern lengths and therefore various signal repetition rates. But physical limitations of sampling hardware typically constrain the sample rate to a narrow range. If the sample rate cannot be arbitrarily specified, it is not possible to subsample signals of any given repetition rate and thus the range of test signals is limited.
When the required sample rate cannot be realized, the elapsed time between samples will not equal some number of signal repetitions plus some small time increment. Instead, the elapsed time between samples may be equal to some number of signal repetitions plus a significant fraction of the repetition time. Consequently, the samples do not directly represent a time history, but can be reordered to form an equivalent time history. The requirement for data reordering is a severe limitation, because a conventional oscilloscope cannot directly display the samples. Instead the samples must be stored and then reordered according to the relationship between repetition and sample rates, before the display of the samples can take place.
BRIEF SUMMARY
The present invention is directed to a system and method which expands the applicability of subsampling to a larger range of signal repetition rates while reducing the range over which the sample rate must be tuned to accommodate a given signal. The resulting sample sequences are in the correct order, enabling direct display with an ordinary oscilloscope or other instrumentation.
In one embodiment, a technique is used such that decimation of the samples also improves the response characteristics of the sensor. The system and method provides for a number of different procedures for sampling a signal of a given length. All other parameters being the same, the system allows more freedom in selecting the sample rate to correctly subsample a repetitive signal.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.
REFERENCES:
patent: 4802098 (1989-01-01), Hansen et al.
patent: 5115404 (1992-05-01), Lo et al.
patent: 6121799 (2000-09-01), Moser
patent: 6278435 (2001-08-01), Etheridge et al.
patent: 6567027 (2003-05-01), May
patent: 6590512 (2003-07-01), Roh et al.
Agilent Technologie,s Inc.
Nguyen Linh Van
Tokar Michael
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