WO1993026110A1 - Dc tracking circuit for ginomy data slicer - Google Patents
Dc tracking circuit for ginomy data slicer Download PDFInfo
- Publication number
- WO1993026110A1 WO1993026110A1 PCT/GB1993/001226 GB9301226W WO9326110A1 WO 1993026110 A1 WO1993026110 A1 WO 1993026110A1 GB 9301226 W GB9301226 W GB 9301226W WO 9326110 A1 WO9326110 A1 WO 9326110A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- signal
- threshold level
- control signal
- data
- change
- Prior art date
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/06—Dc level restoring means; Bias distortion correction ; Decision circuits providing symbol by symbol detection
- H04L25/061—Dc level restoring means; Bias distortion correction ; Decision circuits providing symbol by symbol detection providing hard decisions only; arrangements for tracking or suppressing unwanted low frequency components, e.g. removal of dc offset
- H04L25/065—Binary decisions
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/06—Dc level restoring means; Bias distortion correction ; Decision circuits providing symbol by symbol detection
- H04L25/061—Dc level restoring means; Bias distortion correction ; Decision circuits providing symbol by symbol detection providing hard decisions only; arrangements for tracking or suppressing unwanted low frequency components, e.g. removal of dc offset
- H04L25/062—Setting decision thresholds using feedforward techniques only
Definitions
- This invention relates to a system for data recovery and in particular to a system for extracting binary data from an analogue signal containing such data .
- Such systems are utilised, for example, in digital communications systems in which digital data is transmitted, which data is a mixture of digitised analogue information and control data, such as synchronising data.
- data has to be recovered from the demodulated signal which is, of course, an analogue signal.
- An example of a transceiver which could utilise such a system is described in our European patent application 0333419 which is incorporated herein by this reference.
- the demodulated signal which is output from the frequency discriminator is filtered, and then passed to a data recovery circuit in the form of a data slicer before being applied as digital data to a data processor.
- the present invention is essentially concerned with data recovery circuits of this and similar type, although we do not wish to be limited to the particular arrangement shown in EP 0333419, which is presented simply by way of example, for the purpose of explanation.
- the fundamental purpose of a data recovery circuit is to decide what the smoothly varying analogue input signal represents m binary terms.
- the circuit element which carries out such a task is the comparator but because in this application the signal is constantly crossing and recrossing the threshold level as the 1 's and O ' s of the data are received, the comparator is often referred to as a slicer.
- the slicer is thus the basic component of the data recovery circuit, and its output is a binary signal representing either 0 or 1. More complex systems are known, but the simple slicer system is quite effective.
- the problem with the slicer system is choice of the optimum slicer threshold level.
- the threshold level must be able to vary in order to quickly adjust to a freshly acquired signal; on the other hand, the threshold level must not be forgotten too quickly in the event that the input signal fades, or becomes unreliable.
- the slicer input or output signals may be filtered and thence used to generate a variable threshold level based on a reasonable estimate of the centre of the input signal. This works well provided that the data comprises a reasonably balanced mixture of O ' s and 1 's .
- the philosophy adopted for the present invention is that a workable threshold value should be quickly acquired when the input signal first appears, but that the rate of change of threshold value should be slowed down when the extracted data is positively indicated as already being good or is expected to be of inadequate quality to permit changes.
- the invention provides means for measuring the signal strength and for altering the rate of change of the threshold level in accordance with this measurement. In particular, rapid changes in the threshold level will only take place if the signal strength is not below a predetermined critical value.
- means are additionally provided for detecting whether the system is in synchronism, for example frame lock acquisition, and for altering the rate of change of the threshold in accordance with this decision.
- rapid changes of threshold level will be allowed.
- the advantage of the prevention of rapid tracking, provided synchronism is achieved, is that any short duration interference does not alter the threshold level.
- the measured signal strength is high then the incoming signal should be good and worth rapidly tracking; however, if synchronism has been achieved, there is no longer any need for rapid tracking of the threshold level as the data is now about good enough and any further refinement of the optimum threshold level can be allowed relatively slowly.
- a represen ⁇ tative transceiver is shown under reference 1.
- This transceiver may, for example, be of the type described in our European patent application 0333419.
- the transceiver includes means (not shown) for measuring the received signal strength of the incoming signal, and providing a logic signal at a "Low RSSI" terminal 2 which is high when the RSSI (received signal strength indicator) signal lies below some predetermined threshold, but is otherwise low.
- the transceiver further includes means (also not shown) for identifying, by bit pattern match, when the synchronising words have been received correctly, and providing a logic signal at a "Frame Sync" terminal 3 which is high when a bit pattern match has shown that the sync words have been received correctly. This is all known technology, and will not be described further.
- the demodulated data from the receiver portion of the transceiver is output at a "Demod data" terminal 4 and comprises an analogue waveform such as shown under reference 5.
- This signal is applied to one input of a slicer circuit 6 in the form of a comparator.
- the output from the slicer 6 takes the form of a digital waveform such as shown under reference 7.
- a threshold level which is adjusted by means of a low pass filter feedback network 9 to follow the variations in the input waveform 5.
- the slicer operates to compare the incoming analogue signal with the threshold level to thereby produce the digital waveform 7 in the known manner.
- the threshold level is adjusted to sit between the upper and lower levels of the input waveform and follows the variation of optimum slicing level quickly so that good data is not lost, but when the incoming data is bad the threshold level varies slowly as the signal knowledge is inadequate to optimally select the threshold level.
- the illustrated circuit utilises the "low RSSI" and "Frame Sync" signals described above to control the time constant of the feedback network 9 so that only when the RSSI shows an adequate level of signal and the system has not detected adequate synchronism are fast threshold level changes permitted.
- the terminals 2 and 3 are connected to respective inputs of a NOR gate 10.
- the output of the NOR gate is applied as a control input 11 to the feedback network 9.
- the feedback network 9 includes a low-pass filter comprising a timing capacitor C, a high value resistor R1 and a low value resistor R2.
- a switch S selectively places the resistor R2 in parallel with resistor R1 to thus lower the time constant of the filter.
- Switch S is an electronic switch under the control of the signal at input 11.
- the input 12 of the low pass filter is taken from the input waveform at terminal 4 of the transceiver 1.
- the output 13 of the low pass filter is passed to the threshold level input 8 of the slicer 6-
- the switch S has a third position in which input 12 is, in effect, isolated.
- This switch position may be used, for example, during the transmit portion of alternate transmission/reception cycles such as are used in certain communications systems. In such systems transmission and reception alternate on a cyclic basis; during transmission, if the switch S is switched to the third position, it will hold the threshold level from the previous reception window, and this level will be used to commence slicing in the next reception window. In practice, the switch S will be switched to the third position and back to the first/second position on a cyclic basis to match the alternations of reception and transmission.
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Dc Digital Transmission (AREA)
- Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU43443/93A AU4344393A (en) | 1992-06-10 | 1993-06-09 | Dc tracking circuit for ginomy data slicer |
GB9425397A GB2282942B (en) | 1992-06-10 | 1993-06-09 | DC tracking circuit for ginomy data slicer |
EP93913331A EP0645066A1 (en) | 1992-06-10 | 1993-06-09 | Dc tracking circuit for ginomy data slicer |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB929212263A GB9212263D0 (en) | 1992-06-10 | 1992-06-10 | System for data recovery |
GB9212263.9 | 1992-06-10 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1993026110A1 true WO1993026110A1 (en) | 1993-12-23 |
Family
ID=10716826
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/GB1993/001226 WO1993026110A1 (en) | 1992-06-10 | 1993-06-09 | Dc tracking circuit for ginomy data slicer |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0645066A1 (en) |
AU (1) | AU4344393A (en) |
GB (2) | GB9212263D0 (en) |
WO (1) | WO1993026110A1 (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5872468A (en) * | 1997-06-12 | 1999-02-16 | Northern Telecom Limited | Level detector circuit, interface and method for interpreting and processing multi-level signals |
GB2333214A (en) * | 1998-01-09 | 1999-07-14 | Mitel Semiconductor Ltd | Data slicer |
WO2003034674A1 (en) * | 2001-10-10 | 2003-04-24 | Telefonaktiebolaget Lm Ericsson (Publ) | Receiver with adaptive detection threshold for tdma communications |
CN103516366A (en) * | 2013-09-26 | 2014-01-15 | 中科院微电子研究所昆山分所 | Input signal intensity indicator and indicating method |
TWI634752B (en) * | 2016-02-19 | 2018-09-01 | Azbil Corporation | Filter time constant changing circuit and digital-to-analog (D / A) conversion circuit |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4318128A (en) * | 1979-07-17 | 1982-03-02 | Thomson-Csf | Process and device for retrieving digital data in the presence of noise and distortions |
US4821292A (en) * | 1987-06-03 | 1989-04-11 | General Electric Company | Adaptive limiter/detector which changes time constant upon detection of dotting pattern |
EP0400854A2 (en) * | 1989-05-26 | 1990-12-05 | Motorola, Inc. | Data centering method and apparatus |
-
1992
- 1992-06-10 GB GB929212263A patent/GB9212263D0/en active Pending
-
1993
- 1993-06-09 EP EP93913331A patent/EP0645066A1/en not_active Withdrawn
- 1993-06-09 WO PCT/GB1993/001226 patent/WO1993026110A1/en not_active Application Discontinuation
- 1993-06-09 AU AU43443/93A patent/AU4344393A/en not_active Abandoned
- 1993-06-09 GB GB9425397A patent/GB2282942B/en not_active Expired - Fee Related
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4318128A (en) * | 1979-07-17 | 1982-03-02 | Thomson-Csf | Process and device for retrieving digital data in the presence of noise and distortions |
US4821292A (en) * | 1987-06-03 | 1989-04-11 | General Electric Company | Adaptive limiter/detector which changes time constant upon detection of dotting pattern |
EP0400854A2 (en) * | 1989-05-26 | 1990-12-05 | Motorola, Inc. | Data centering method and apparatus |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5872468A (en) * | 1997-06-12 | 1999-02-16 | Northern Telecom Limited | Level detector circuit, interface and method for interpreting and processing multi-level signals |
GB2333214A (en) * | 1998-01-09 | 1999-07-14 | Mitel Semiconductor Ltd | Data slicer |
US6608871B2 (en) | 1998-01-09 | 2003-08-19 | Lsi Logic Corporation | Data slicers |
WO2003034674A1 (en) * | 2001-10-10 | 2003-04-24 | Telefonaktiebolaget Lm Ericsson (Publ) | Receiver with adaptive detection threshold for tdma communications |
KR100835847B1 (en) * | 2001-10-10 | 2008-06-05 | 텔레포나크티에볼라게트 엘엠 에릭슨(피유비엘) | Digital Data Recovery Method and Circuit |
CN103516366A (en) * | 2013-09-26 | 2014-01-15 | 中科院微电子研究所昆山分所 | Input signal intensity indicator and indicating method |
CN103516366B (en) * | 2013-09-26 | 2017-01-18 | 中科院微电子研究所昆山分所 | Input signal intensity indicator and indicating method |
TWI634752B (en) * | 2016-02-19 | 2018-09-01 | Azbil Corporation | Filter time constant changing circuit and digital-to-analog (D / A) conversion circuit |
Also Published As
Publication number | Publication date |
---|---|
GB9212263D0 (en) | 1992-07-22 |
EP0645066A1 (en) | 1995-03-29 |
GB2282942A (en) | 1995-04-19 |
AU4344393A (en) | 1994-01-04 |
GB2282942B (en) | 1996-01-24 |
GB9425397D0 (en) | 1995-02-15 |
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