WO1993026104A1

WO1993026104A1 - Device and method for detection of intermittently repeating information

Info

Publication number: WO1993026104A1
Application number: PCT/US1993/005258
Authority: WO
Inventors: John Decatur Williamson
Original assignee: Smart Tag Systems, Inc.
Priority date: 1992-06-05
Filing date: 1993-06-03
Publication date: 1993-12-23

Abstract

A device (10) for detecting information at least intermittently repeating in information units such as digital words, without knowledge of the content or format of such information, includes a shift register (14) for receiving and storing a preselected number of information units and a comparator (16) that compares the information content and format of a first information unit with at least one successive information unit. Upon the occurence of a match in comparator (16), comparator (16) generates a match signal (43) furnishing the information to an output latch (18). Thus, by comparing preselected, successive information units, valid information that at least intermittently repeats may be distinguished from noise and other signals not including information.

Description

DEVICE AND METHOD FOR DETECTION OF INTERMITTENTLY REPEATING INFORMATION

TECHNICAL FIELD

The present invention relates in general to devices for identifying infor¬ mation in a signal. More particularly, the present invention pertains to devices and methods for distinguishing between information conveyed by a signal trans¬ mitted via a communications channel and noise appearing therewith. More spe- cifically, the present invention relates to devices and methods for identifying information transmitted by digital electromagnetic signals in the absence of any knowledge of the form or content of such information.

BACKGROUND ART Information transmission is the lifeblood of a technology based society.

Innumerable applications rely upon the timely and correct receipt of information. So important is the correct receipt of information, an entire science has been developed for the primary purpose of distinguishing between information and noise, and facilitating instantaneous, error-free reception and extraction of such information. Given the pervasive presence of digital electronics, much of this effort is focused upon identification, error-free reception and extraction of information from digital signal carriers.

Two exemplary applications where the identification of information is cru¬ cial involve the remote data collection and processing fields of electronic article surveillance and automatic identification. Work in these fields, as in others, has centered around two basic approaches for identifying whether a received signal contains information. In one, potential information detected in the received signal is compared to a list of all valid information. If a match is found, the detected information is assumed to be valid. Typical of this approach are the devices disclosed in U.S. Patent Nos. 4,096,477 to Epstein et al. and 4,463,353 to Kuzara. Epstein's identification system using coded passive transponders employs a combinational logic analyzing circuit shown in Fig. 5 and described at Col. 3, lines 49-53 which compares the received and decoded pulse pattern to a pre¬ selected list of pulse patterns stored in its memory. The animal feeding and monitoring system of Kuzara similarly compares a coded identifier signal gener¬ ated by a commercially available programmable encoder described at Col. 6, lines 41-48 included in the electronic identity tag worn by the animal to a list of preselected coded identifier signals stored in a corresponding decoder.

The other basic approach for identifying whether a received signal includes information relies not upon prestored knowledge about all possible valid informa¬ tion, but upon conveying the correct format and content of the information trans- mitted as part of the information. In U.S. Patent No. 4,471,345 to Barrett, Jr. the receiving portal unit in a randomized tag to portal communication system employs a preselected preamble sequence (i.e., identification packet) to ascertain whether received information is valid. As more fully shown in Figs. 4 and 8B and described at Col. 5, lines 44-50 and Col. 16, lines 1-48, respectively, this device also checks the format of the received signal (e.g., frequency and bit rate) to further verify the likelihood its information content is valid.

It will be appreciated that both these approaches are entirely dependent upon an a priori knowledge of the correct information to be conveyed. In the first instance that knowledge is preselected and stored in the receiving device; in the other instance that knowledge is transmitted along with information itself. As such, both approaches suffer from several deleterious limitations.

Perhaps the most significant limitation is that in many applications, includ¬ ing those of electronic article surveillance and automatic identification, knowl¬ edge of all valid information may be difficult or, practically speaking, impossible to ascertain in advance of transmission. As the magnitude of information avail¬ able for transmission increases, the storage and signal processing required for verification with such approaches is more likely to be prohibitive. In systems that convey information digitally, use of, for example, a 23 bit identification code would require storing and checking more than 8.4 million possible code combina- tions, far too costly in both memory and processing time for most applications. Other disadvantageous aspects of the above noted approaches should be also appreciated. For example, these approaches verify only that the information perceived to have been received is among the information that may be validly conveyed for that application; these approaches do not verify that the information perceived to have been received was what was actually transmitted. Also, where information characteristics are transmitted with the information, precious band¬ width is devoted to information integrity instead of information content and addi- tional time is required for extracting and processing the embedded information characteristics.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a device and method that verifies with a high degree of certainty whether a signal that may include information of an unknown format and content does include information.

It is another object of the present invention to provide a device and method, as set forth above, wherein valid information is not preselected and stored in the device. It is still another object of the present invention to provide a device and method, as set forth above, wherein characteristics of the information being transmitted are not utilized for determination of information validity.

It is yet another object of the present invention to provide a device and method, as set forth above, wherein device resources and processing time employed to determine the validity of the information received are minimized. It is a further object of the present invention to provide a device and method, as set forth above, in which no portion of the transmission channel is utilized for transmission of the format of valid information.

These and other objects and advantages of the present invention over exist- ing prior art forms will become more apparent and fully understood from the fol¬ lowing description in conjunction with the accompanying drawings.

In general, a combinational logic device for detection of information in a signal where the information at least intermittently repeats in information units, includes means for receiving a preselected number of information units each hav- ing an information content, and means for comparing the information content of a first information unit with the information content of at least one successive information unit, and upon a match thereof generating a match signal.

In general, a method for detection of information in a signal where the information at least intermittently repeats in information units, includes the steps of receiving and storing a preselected number of information units each having an information content, and comparing the information content of a first information unit with at least one successive information unit and, upon a match thereof, generating a match signal.

In general, a device for identifying repetitive information in a signal includes means for receiving the signal and selecting portions thereof, and means for comparing a first selected portion of the signal with at least one other of the selected portion of the signal, and upon a correspondence therebetween output- ting such matching selected portion of the signal.

BRIEF DESCRIPTION OF THE DRAWING

The Figure presents a block diagram of an exemplary device in accordance with the concepts of the present invention. In this embodiment suitable for use with a digital input signal, four sequentially received words in the input signal are processed to determine if information is present.

PREFERRED EMBODIMENT FOR CARRYING OUT THE INVENTION

The Figure depicts in block diagram form an exemplary device in accord- ance with the concepts of the present invention, generally indicated by the numeral 10. Device 10, which when operated performs an exemplary method in accordance with the concepts of the present invention, relies on the principle that in many applications such as electronic article surveillance and automatic identifi¬ cation, at least intermittent repetition of the information for at least a brief period of time is common. Thus, detection of successive identical units of infor¬ mation is a highly reliable indicator of the presence of valid information. Device 10 and the method employed thereby select (or otherwise extract) and compare successive units of information, and upon a correspondence therebetween output such at least intermittently repeating information. Exemplary device 10 is configured to detect the presence of valid informa¬ tion in a digital pulse train signal where each element to be hereinafter described is suitable for processing data in units of information corresponding to the word size preselected for the application, such as 8, 16 or 32 bits. Device 10 illustrated in the Figure may be seen to include several individual combinational logic ele¬ ments including logic control 12, shift register 14, comparator 16 and output latch 18.

Logic control 12 receives an input signal 20 in the form of a digital pulse train from any signal processor (not shown) suitable for the application. Logic control 12 meters data 21 to shift register 14, and generates digital control signals including shift register clock signal 22, shift register reset signal 23 and compara¬ tor enable signal 24, all utilized as hereinafter described.

In the embodiment depicted in the Figure where information is to be moni- tored over four words, shift register 14 includes four individual registers 30, 31, 32 and 33, each of which receive shift register clock signal 22 and shift register reset signal 23. Registers 30, 31, 32 and 33 provide data output signals 34, 35, 36 and 37, respectively, for the most recent and three succeeding clock time inter¬ vals. As is well known, shift register 14 may be configured with any combination of parallel or serial inputs and outputs providing data transfer at an acceptable rate for the application.

Comparator 16 includes a plurality of individual comparators one less in number than the number of individual registers in shift register 14. Thus, in the depicted embodiment there exists three comparators 40, 41 and 42 each of which receive the comparator enable signal 24 from logic control 12 and the most recent data output signal 34 from register 30. Comparators 40, 41 and 42 also receive one of the successively delayed data output signals 35, 36 and 37 from registers 31, 32 and 33, respectively. Upon receipt of an enable signal from control unit 12, comparators 40, 41 and 42 compare the most recent data output signal 34 with each of the last three successively delayed data output signals 35, 36 and 37, and where a match is detected, generate a latch enable signal 43 for gating the most recent data output signal to output latch 18.

Operation of device 10 is straightforward and is begun with the issuance of reset signal 22 by logic control 12 to each of the registers 30, 31, 32 and 33 in shift register 14, clearing the same. Next, data from input signal 20 for the next four successive words is clocked into register 30 and shifted into registers 31, 32 and 33, respectively. Thereafter logic control 12 generates comparator and trans¬ mits enable signal 24 to test if the most recently received data matches that received in any of the succeeding three time units. If so, those comparators find¬ ing a match generate latch enable signal 43 to output latch 18, making such data available to further signal processing circuitry for the application.

The skilled artisan should now further understand that with the device and method of the present invention the probability of a noise induced signal aberra¬ tion being verified as valid information is significantly small. The possibility of incorrect verification can only happen where identical words occur randomly in the preselected successive time units. However, even this minuscule possibility can be further reduced by increasing the number of words compared (i.e., increasing the number of compared samples) and/or lengthening the number of digits in a word (i.e., increasing the size of the compared sample).

In addition to the aspects of the present invention noted above, other alter¬ natives and features should now be apparent. For example, in the preferred embodiment shown and described herein the device was configured to process digital information. The concept of the present invention is equally applicable to analog information. In either event, as would occur to the skilled artisan, any information storage, comparator and control circuit compatible with the applica¬ tion, or device functionally reasonably equivalent thereto, should be suitable for use without departing from the spirit of the present invention. Inasmuch as the present invention is subject to variations, modifica¬ tions and changes in detail, some of which have been expressly stated herein, it is intended that all matter described throughout this entire specification or shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense. It should thus be evident that a device constructed according to the con- cept of the present invention, and reasonably equivalent thereto, will accomplish the objects of the present invention and otherwise substantially improve the art of detecting valid, intermittently repeating information and, more particularly, applications such as the remote data collection and processing fields of electronic article surveillance and automatic identification.

Claims

CLAIMS:

1. A combinational logic device for detection of information in a signal, the information at least intermittently repeating in information units, comprising: means for receiving a preselected number of information units each having an information content; and, means for comparing said information content of a first information unit with said information content of at least one successive information unit, and upon a match thereof generating a match signal.

2. A device, as set forth in claim 1, wherein the signal is digital, and said means for receiving a preselected number of information units includes logic con- trol means for receiving the digital signal and extracting said first information unit and said successive information unit from the digital signal.

3. A device, as set forth in claim 2, wherein said means for receiving a preselected number of information units further includes shift register means for storing said successive information unit, said logic control means providing said first information unit and said successive information unit to said shift register means and controlling said shift register means.

4. A device, as set forth in claim 3, wherein said shift register means includes a plurality of registers equal in number to the number of information units to be compared by said means for comparing.

5. A device, as set forth in claim 4, wherein said means for comparing includes a quantity of comparators one less in number than the number of infor- mation units to be compared.

6. A device, as set forth in claim 5, wherein said registers and said compara- tors have a number of digits corresponding to a preselected word size.

7. A method for detection of information in a signal having at least intermittently repeating units, comprising the steps of: receiving and storing a preselected number of selected portions of the signal; and, comparing said information content of a first information unit with said information content of at least one successive information unit and, upon a match thereof, generating a match signal.

8. A method for detection of information in a signal, as set forth in claim 7, wherein said step of receiving and storing a preselected number of information units includes the step of receiving a preselected number of digital information units and storing said preselected number of digital information units in a shift register.

9. A method for detection of information in a signal, as set forth in claim 7, wherein said step of receiving and storing a preselected number of information units further includes the step of receiving a digital signal and extracting the digital information units therein.

10. A device for identifying repetitive information in a signal, comprising: means for receiving the signal and selecting portions thereof; and, means for comparing a first said selected portion of the signal with at least one other of said selected portion of the signal, and upon a correspondence therebetween outputting such matching said selected portion of the signal.