Aspects of the present invention relate generally to analysis of transmission lines, and more particularly to a system and method of data acquisition for transmission line performance analysis and fault detection applications.
Time domain reflectometer (TDR) technology has been traditionally employed to detect faults, or “events,” which are generally characterized by impedance discontinuities or variations from nominal impedance, for example, in wire-lines such as telephone, twisted pair, unshielded twisted pair (UTP), and television (co-axial) cables, was well as other transmission lines known in the art. Separately, spectrum analyzer technology seeks to ascertain the spectral content of transmitted signals propagating through such transmission lines.
In a typical data acquisition system for use in fault detection applications, a TDR employs a pulse generator to transmit a signal pulse, or incident pulse, of electromagnetic energy through the line to be tested; a fault or impedance discontinuity existing in the line will generally reflect at least a portion of the incident pulse back to the TDR. Analysis of a detected event may be based upon numerous parameters such as, inter alia, the duration and frequency of the incident pulse, the magnitude of the reflected signal, the time delay between transmission of the incident pulse and subsequent reception of the reflected signal, and the like.
In accordance with existing systems and methods, conventional data acquisition technologies allow only a single data point to be sampled per incident pulse transmitted by the TDR; this limitation results in low signal acquisition rates, and consequently, sluggish TDR performance during normal use in certain operational modes. Additionally, restricting a TDR to acquiring a single data sample per transmitted incident pulse prevents implementation of an integrated spectrum analyzer function into a single data acquisition apparatus or unit.
Inadequate design and overall configuration of testing hardware represent important factors contributing to deficient performance and versatility of traditional transmission line test equipment. For example, a conventional TDR incorporates sampler circuitry at the input of the system; reflections of incident pulses received by the TDR are directed through the sampler to a low bandwidth amplifier and low bandwidth analog to digital (A/D) converter circuitry. While limited improvements may be achieved through use of more suitable amplification technology, as is generally known in the art, conventional variable gain and attenuation circuits are commonly constituted by complex arrays of analog selectors and resistors implemented around operational amplifier (Op-Amp) stages; introduction of such variable gain amplifier and attenuator components substantially increases both the complexity and the expense of data acquisition systems. Further, as noted briefly above, a solution based upon improved amplification and attenuation only addresses one aspect of the problem; narrow bandwidth low speed sampler circuitry and the configuration of existing hardware does not accommodate integration of TDR fault detection and spectrum analyzer functionality.
Embodiments of the present invention overcome various shortcomings of conventional technology, providing a system and method of wideband data acquisition for transmission line performance evaluation and fault detection applications. In accordance with one aspect of the present invention, for example, wideband variable gain amplifier and attenuation circuitry may be employed in conjunction with high speed sampling circuitry to facilitate event detection in a transmission line or wire; this implementation additionally allows seamless integration of spectrum analysis functionality in a single data acquisition system.
The foregoing and other aspects of various embodiments of the present invention will be apparent through examination of the following detailed description thereof in conjunction with the accompanying drawings.
Turning now to the drawings,
A user or technician at a host computer system 151 may selectively control operational characteristics or functionality of module 100 as described below. As indicated in
In that regard, host computer 151 may be coupled to module 100 using various hardware interfaces and communication protocols known in the art; while this coupling is illustrated as a serial data link in
During operation of module 100, pulse trigger 111 may control pulse generation, transmitting a pulse trigger signal 111A to pulse generator 110. As indicated in
As is generally known in the art, pulse generator 110 may transmit a pulse 110A responsive to trigger signal 111A and a timing signal 160B from clock 160. Line transformers 120 may comprise wideband coupling circuitry capable of operating in the 10 kHz-500 MHz frequency range; in that regard, a dual bipolar pulse driver and a dual balanced duplexer may be provided to analyze two transmission lines (designated by reference numerals 199 and 198) simultaneously. In particular, a bipolar pulse driver may be operative to alter input pulse 110A in a manner appropriate for the specific test to be conducted on lines 199,198; such a suitable pulse driver may then create and transmit incident pulses 120A and 120B through transmission lines 199 and 198, respectively. Incident pulses 120A,120B may be of any selected frequency and duration specified by processing unit 150 under control of host computer 151.
Transmission lines 199 and 198 may be telephone lines, twisted pair lines, unshielded twisted pair (UTP) lines, co-axial cables such as used to transmit cable television signals, fiber-optic cables, and the like. Those of skill in the art will appreciate that the present multi-function data acquisition system and method may provide integrated TDR and spectrum analysis functionality for analysis of any number of data transmission line types or variations; the present disclosure is not intended to be limited by the constitution of transmission lines 199,198 nor the nature of the signals carried therein.
Events or impedance discontinuities existing in transmission lines 199 and 198 may create reflection pulses 199A and 198A, respectively, which may be received by the dual balanced duplexer component of the line transformers 120. In operation, the duplexer may provide amplification of received reflection pulses 199A, 198A; such amplification at the receiver side of line transformers 120 may be a factor of 2 or more (2×) for typical TDR applications and line performance or spectrum analyses. In some embodiments, the duplexer may additionally be configured to attenuate or to cancel incident pulses 120A, 120B or their effects on the receiver side of line transformers 120, minimizing or eliminating the “dead zone” characteristic of conventional TDR equipment.
As indicated in
Sampler component 140 may generally be constituted by a high speed sampler, a high speed A/D converter, and memory for storing sample data. The sampler may sample the input (130A) at discrete time intervals or on a continuous, or streaming, basis; in that regard, sampler operation may be controlled by a sampler trigger signal 141A transmitted from sampler trigger 141 which, in turn, may be operative in accordance with a control signal 150D transmitted from processing unit 150. In this embodiment, for instance, control signal 150D may determine the operational mode in which sampler component 140 functions (i.e. discrete samples or streaming conversion at a particular frequency), while trigger signal 141A also provides information sufficient to determine the sample rate or frequency employed.
It will be appreciated that sampler trigger 141 may be operative in accordance with timing signals 160A received from clock 160 as well as control signal 150D. As is generally known in the art, asynchronous clock 160 may be configured to provide signals at two different clock rates, e.g. 80 MHz and 40 MHz, as shown in
In some embodiments, the sampler may provide sample data to the A/D converter, which may subsequently transmit digital data signals (represented by signal 140A) to processing unit 150 immediately; additionally or alternatively, output from the A/D converter may be stored as digital data samples temporarily in memory.
The memory component may be implemented in random access memory (RAM) chips, for example, or any other suitable data storage medium configured and operative to store or to buffer digital data including, but not limited to: fast static random access memory (SRAM) or transistor-based memory components; erasable programmable read only memory (EPROM); flash memory; various magnetic, optical, or magneto-optical disc media; and the like.
Amplifier component 230 comprises a high speed amplifier 231 receiving control signal input from an output attenuator control circuit 232 and an input gain control circuit 234; additionally, a digital to analog converter (DAC) component 233 may be provided. In operation, DAC component 233 may be operative to convert digital control signals 150B from a microprocessor or central processing unit (CPU), incorporated in processing unit 150 in
As is generally known in the art, attenuator circuits may be implemented on either the input side or the output side of an amplifier, or both; similarly, gain control may be implemented at either or both sides of an amplifier, or at various stages in an Op-Amp arrangement. Accordingly, those of skill in that art will appreciate that attenuator control circuit 232 may be implemented on the input side of high speed amplifier 231 and that gain control circuit 234 may be implemented on the output side of high speed amplifier 231. The
As indicated in
High speed amplifier 231 may be operative to receive input signals 120C as shown in
Accordingly, wideband variable gain amplifier component 230 may enable all the functionality of a conventional variable gain amplifier while providing much wider bandwidth; the responsive frequency range of 0.01 MHz-500 MHz represents an improvement over existing variable gain amplifiers by as great as a factor of 500. Additionally, simple control circuits 232,234 comprising PIN diodes may enable variable gain amplifier component 230 to be responsive to a voltage input range of as great as 8 volts.
Output signals 130A from high speed amplifier 231, generally corresponding to signals designated by reference numeral 130A in
Logic 242 generally comprises TDR sampler timebase logic as well as spectrum analyzer acquisition control logic as indicated in
As indicated in
For example, the programmable circuitry resident in logic 242 may be configured to toggle sampler component 240 between one of two operating modes. In the
In some embodiments, logic 242 may be designed and configured to be removable. Logic 242 implemented in a removable chip, board, or module may be removed and reprogrammed, for example, or replaced by a different hardware element having different or improved functionality. In the foregoing manner, the operability of sampler component 240 may be selectively altered or modified without requiring replacement of the entire hardware arrangement.
Output signals 242A,242B from logic 242 are generally a function of control and timing signals 150D,160A; accordingly, the mode of operation, sample rate, and other functional characteristics of sampler 241 may be controlled by signal 242A, and utilization of memory 243 may be influenced by signal 242B.
As noted above with reference to
In that regard, memory 243 may employ signal line 243A to receive sample data from sampler 241 and to transmit sample data to processing unit 150. As illustrated in
Responsive to an appropriate control input signal 150D, logic 242 may configure sampler 241 to operate as a spectrum analyzer under control of the spectrum analyzer CPLD. In a spectrum analyzer mode, sampler 241 may perform continuous, i.e. streaming, sampling and A/D conversion of input signal 130A at one or more selected frequencies; in some embodiments, for example, sampler 241 may perform sampling of input signal 130A at 40 MHz. A 40 MHz sample frequency may be adequate for many practical situations; in accordance with the Nyquist Theorem of digital sampling, a 40 MHz sampling frequency is adequate to digitize an analog waveform having a frequency of about 20 MHz. By way of a practical example, current digital subscriber line (DSL) transmission lines typically operate at frequencies up to 8 MHz, while proposed standards such as very high data rate DSL (VDSL), for example, may increase the spectra beyond 10 MHz. It will be appreciated that the
Sampler 241 may incorporate high speed A/D converter circuitry configured and operative to accommodate the bandwidth and sample frequencies of the high speed sampler during ordinary operation.
In some situations mentioned briefly above, sampler 241 may execute sampling at a particular frequency, convert the samples to digital data, and transmit the sample data to memory 243, which may perform the role of a data buffer under certain circumstances. Sample data may be stored until memory 243 has reached capacity, at which point the entire contents of memory 243 may be transmitted to a CPU (e.g. at processing unit 150 in
For analysis of the full spectral content of signals propagating through transmission lines, fine resolution may require as much as the full 32 k×8 bit data samples stored in the
As is generally known in the art of spectrum analysis, the
In addition to streaming conversion of input signal 130A, sampler 241 may be configured to halt, or to “freeze,” its output. In this embodiment, control signal 150D may instruct logic 242 to freeze the timing component of signal 242A at the logic zero level. With its clock signal frozen, sampler 241 may hold the A/D converter circuitry in a frozen mode or condition, such that the most recent sample acquired by sampler 241 may be presented at the output of the A/D converter.
Responsive to an appropriate control input signal 150D, logic 242 may configure sampler 241 to operate in a discrete sampling TDR mode under control of the sampler timebase CPLD. In contrast to conventional TDR technology, however, wideband high speed sampler 241 may be configured to acquire more than a single data sample for each incident pulse transmitted through the transmission lines. Accordingly, sampler 241 may operate at a sufficient rate to obtain data on multiple events, for example, located at different locations in the transmission line; as a single incident pulse is transmitted through the line, multiple reflection pulses caused by various impedance discontinuities may be received and processed through wideband high speed data acquisition circuitry. Employing a wideband topology through amplifier component 230 and sampler component 240 may enable the
As described above with reference to
A signal representative of the received signal (e.g. processed for amplification and attenuation of incident pulses as described above) may be transmitted to data acquisition circuitry at block 304. Initially, data acquisition may include forwarding this representative signal to wideband variable gain amplifier circuitry incorporating a high speed amplifier as indicated at block 305 for processing; gain and attenuation of the high speed amplifier may be selectively adjusted (block 305A), for example, from a remote terminal or other electronic system coupled to the data acquisition circuitry. Levels of gain and attenuation control parameters selected at block 305A may depend upon the configuration and desired operability of the system as a whole, and may generally be attained and maintained by control signal circuitry comprising PIN diodes as described in detail above with reference to
Signals amplified and attenuated as described above may be forwarded to a wideband high speed sampler at block 306. As set forth in detail above, the mode of operation of sampler and the frequency at which it operates may be selectively controlled (block 306A) by logic responsive to a remote CPU and system clock signals. Sampler modes may include, among others, TDR and spectrum analyzer functionality.
Analog output from the sampler may be converted to digital signals by high speed A/C converter circuitry as represented at block 307. Digital sample data may be stored or temporarily buffered in a data storage medium or memory (block 308) as described above. Additionally or alternatively, digital sample data may be transmitted directly to a CPU or processing unit for analysis as indicated at block 309.
It will be appreciated that various alternatives exist with respect to the
As noted above, the present system and method may enable simple control of attenuation and gain parameters in data acquisition circuitry for TDR and line performance or spectrum analysis applications. Additionally, enabling a TDR selectively to acquire multiple data samples per transmitted incident pulse may enable an integrated spectrum analyzer functionality as set forth in detail above.
The present invention has been illustrated and described in detail with reference to particular embodiments by way of example only, and not by way of limitation. Those of skill in the art will appreciate that various modifications to the disclosed embodiments are within the scope and contemplation of the invention. Therefore, it is intended that the invention be considered as limited only by the scope of the appended claims.
The present Application is related to U.S. application Ser. No. ______, filed ______, titled TIME DOMAIN REFLECTOMETER WITH DIGITALLY GENERATED VARIABLE WIDTH PULSE OUTPUT (Attorney Docket No. 083277-0272108), and U.S. application Ser. No. ______, filed ______, titled TIME DOMAIN REFLECTOMTER WITH WIDEBAND DUAL BALANCED DUPLEXER LINE COUPLING CIRCUIT (Attorney Docket No. 083277-0272109), the disclosures of which are incorporated herein by reference.
Number | Date | Country | |
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Parent | 09967633 | Sep 2001 | US |
Child | 10999743 | Nov 2004 | US |