Abstract
A PSK signal is received and digitized in a limiter (26) to substantially remove the signals amplitude characteristics. A phase detector (44) receives the digital data and, based upon transitions in the data between high and low states, provides phase estimates. The phase estimates are converted by a data decoder (50) into binary data representing the symbols transmitted to form the PSK signal. A number of overlapping windows of digital data are used to determine phase estimates. A unique word detector (52) receives binary data from the data decoder (50) and, using a correlation technique, identifies one set of windows which substantially maximizes synchronization of the demodulator with the received PSK signal. After the synchronizing window has been identified, an automatic frequency controller (46) monitors any frequency drift of the PSK signal and corrects the phase estimates.
Technologies
Power Control
Product
Use Cases
Wireless communication
Services
Claim
1. In a digital communications system having a transmitter for transmitting information in the form of an analog phase shift keyed (PSK) signal and a receiver for receiving said PSK signal, said PSK signal having amplitude, frequency, and phase characteristics wherein at least some of said phase characteristicε are related to the information so transmitted, a demodulator comprising; a phaεe detector receiving an input of digital data representative of said analog PSK signal so received and providing successive outputs representative of phase estimates of εaid PSK signal based on tranεitionε in εaid digital data; and a data decoder having an input of coupled to said phase detector to receive an input εaid phaεe estimates, said data decoder converting said phaεe eεtimates to phase data indicative of said transmitted information.
2. The demodulator of claim 1, wherein said digital data comprises a plurality of sampleε grouped into overlapping windowε, a time between consecutive samples defining a sampling period, the demodulator further comprising: a timing recovery controller coupled to said phase detector and having an input related to said phaεe eεtimact and operable to provide an output representative of an amount to adjust said windows by one of i) advancing said windowε at least one sampling period and ii) delaying said windowε by at leaεt one sampling period.
3. The demodulator of claim 1, further comprising: a frequency controller having an input coupled to εaid phase detector for accepting said phase eεtimateε and providing an output repreεentative of a corrected phase corresponding to each phase estimate input thereto.
4. The demodulator of claim 3, wherein said digital data compriseε a plurality of εamples which are grouped into overlapping windowε which are a time between conεecutive εampleε defining a sampling period further comprising: a timing recovery controller coupled to said frequency controller and having an input of said corrected phase estimates received during each window and providing an output representative of an amount to adjust said windows by one of i) advancing said windows at least one sampling period and ii) delaying said windows by at least one sampling period.
5. The demodulator of claim 4, wherein, εaid PSK signal comprises a known sequence of data defining a unique word, said demodulator further compriεing: a unique word detector having an input for receiving εaid phaεe data, εaid unique word detector making a determination that εaid unique word haε been detected baεed on εaid phaεe data and identifying a εet of said windows in which said unique word is so detected and defining said set of windows aε εynchronizing windowε and further providing an output identifying εaid εynchronizing windowε; and εaid data decoder being further coupled to the unique word detector to receive εaid output identifying said synchronizing windowε, said data decoder providing an output of said phase data aεεociated with εaid synchronizing windows.
6. The demodulator of claim 1, wherein said PSK signal compriεes a known sequence of data forming a unique word, the demodulator further comprising: a unique word detector coupled to said data decoder and having an input for receiving said phaεe data, εaid unique word detector making a determination that said unique word has been detected based on said phase data and providing an output representing the same.
7. The demodulator of claim 1, wherein said digital data comprises a sequence of successive digital sampleε, each εample having a value aεεociated with one of a high level and a low level, the phaεe detector comprising: an inεtantaneouε phaεe decoder having an input of said digital data, said instantaneous phase detector determining if a transition between consecutive digital samples has occurred such that one of 1) one εample has a value associated with said high level and a subsequent digital sample has a value associated with said low level and 2) one sample has a value associated with said low level and a subsequent digital sample haε a value aεεociated with εaid high level, and providing a decoded output repreεentative of at least said transitions so determined; and an instantaneous phase estimator having an input coupled to said instantaneous phase decoder to receive said decoded output, said instantaneous phaεe eεtimator providing an output representative of an average phase estimate based on εaid tranεitionε.
8. The demodulator of claim 7, wherein said PSK signal represents a sequence of known data symbols, each symbol being associated with a phase characteristic of said PSK signal, εaid inεtantaneouε phaεe eεtimator comprising: a counter for incrementing a counter value related to an instantaneous phase of said PSK signal; and an accumulator having a first input coupled to an output of said counter and a second input coupled to said instantaneous phase decoder, εaid accumulator accumulating εaid counter valueε of said counter upon each determination that a tranεition haε occurred.
9. The demodulator of claim 7, wherein εaid PSK signal represents a sequence of known data symbols, each symbol being asεociated with a phase of said PSK signal, the phase detector further compriεing: a differential phaεe detector having an input coupled to εaid instantaneous phase estimator, εaid differential phaεe detector generating an output repreεentative of a difference between each average phaεe eεtimate and a previouε average phase estimate
10. The system of claim 1, wherein substantially all amplitude characteristics are removed from said digital data before said digital data is received by εaid phaεe detector
11. A method for demodulating a phase shift keyed', '(PSK) signal having a sequence of symbolε, each εymbol being baεed upon one of a known εet of poεεible transmitted phases, said symbols being received in εucceεεion by a receiver, compriεing the steps of: generating an analog signal indicative of the symbols received by the receiver and defining the analog signal as said PSK signal; digitizing εaid PSK εignal to provide a εequence of digital data samples representative of said PSK signal received, each digital data sample having a value asεociated with one of a high level and a low level; identifying tranεitionε from εaid high level to εaid low level and from εaid low level to εaid high level between succeεεive digital data εamples; generating a phase estimate based on said transitions so identified; and decoding each phase estimate to provide binary data representative of said symbolε received and defining εaid data as decoded data
12. The method of claim 11, further comprising the εtepε of: accumulating a εequence of the binary data; correlating εaid εequence of binary data to a unique εequence of binary data; providing a measure of εaid correlation; and generating a detection signal if said measure exceeds a predetermined threshold
13. The method of claim 12, further comprising the steps of: accumulating subεequent sequences of binary data; correlating each subsequent sequence of binary data to said unique sequence of binary data; providing a measure of said correlation for each subsequent correlation; selecting one sequence of binary data having a higheεt measure of correlation; and providing an output identifying said selected sequence
14. The method of claim 13, wherein the step of selecting εaid sequence of binary data having the highest measure of correlation comprises the steps of: adding a number of consecutive meaεures of correlation together resulting in a cumulative correlation value for each sequence of binary data; comparing each cumulative correlation value to a most previous cumulative correlation value until a current cumulative correlation value is lesε than a most previous correlation value and defining that moεt previous cumulative correlation value as the highest cumulative correlation; and defining one εequence of binary data corresponding to the last of the number of measureε of correlation added together to form the highest cumulative correlation as the selected sequence of binary data.15. The method of claim 11, wherein the step of digitizing εaid PSK signal comprises the steps of: limiting the analog εignal representative of said PSK εignal to provide a diεcrete εignal εo that where said analog εignal has an amplitude greater than zero said diεcrete εignal has an amplitude corresponding to a first predetermined level and where said analog signal has an amplitude less than zero εaid diεcrete signal haε an amplitude corresponding to a second predetermined level; and sampling said discrete signal thereby forming said digital data sampleε.16. The method of claim 11, further compriεing: comparing each phase estimate with a previouε phaεe eεtimate to determine a difference between each two consecutive transmitted phases.17. The method of claim 11, wherein each εymbol is transmitted for a period of time defining a symbol interval, the method further comprising; generating a number of phaεe estimates during each symbol interval; and averaging said number of phaεe estimates over a period of time defining a window to provide an averaged phase estimate.18. The method of claim 17, further compriεing: defining a number of overlapping windows.19. The method of claim 17, wherein a length of said window is lesε than the εymbol interval.
20. The method of claim 11, wherein each symbol is transmitted for a period of time defining a symbol interval, the method further comprising; generating a number of εaid phaεe estimates during each symbol interval; defining a number of windowε, each window having a length leεε than said εymbol interval; generating an average phaεe estimate corresponding to each window; generating a frequency offεet representative of a difference between average phase estimates; correcting said average phaεe eεtimateε by adjuεting εaid average phaεe eεtimateε by said frequency offset.
21. The method of claim 20, further comprising; grouping said windows into εetε based on a relative reference in time of each said window to said symbol interval; accumulating setε of decoded data so that each said set of decoded data correεponds to those windows in said εet of windows; comparing each set of decoded data to a known sequence of data; generating a detect signal when said decoded data is substantially the same as εaid known sequence of data; and defining a set of synchronizing windows aε εaid εet of windowε correεponding to said set of decoded data when said set of decoded data iε εubstantially the same as εaid known sequence of data.
22. The method of claim 21, further compriεing: defining a window before each of εaid εynchronizing windowε aε an early window; defining a window after each of said εynchronizing windowε as a late window; determining a phase offset for each of said early and late windows; comparing said phase offset corresponding to said early window and said phase offεet correεponding to said late window, said comparison resulting in a difference between εaid two phaεe offεets representative of a timing offset; adjusting a timing of said synchronizing windows relative to said symbol interval, based on said timing offset.']
Associated Portfolios
Licensor Claim Chart
 Claim Chart |
 Technology |
 Creation Date |
 Download |
|---|---|---|---|
|
Claim charts will soon be available!
|
|||
SUMMARY
ClaimChart-EP0746931A1-STO
Patent number:EP0746931A1
Claim Chart Type : SEP Claim Chart
Price: 200 €
Note:
The information in blue was extracted from the third parties (Standard Setting Organisation, Espacenet)
The information in grey was provided by the patent holder
The information in purple was extracted from the FrandAvenue
Explicitly disclosed patent:openly and comprehensibly describes all details of the invention in the patent document.
Implicitly disclosed patent:does not explicitly state certain aspects of the invention, but still allows for these to be inferred from the information provided.
Basis patent:The core patent in a family, outlining the fundamental invention from which related patents or applications originate.
Family member:related patents or applications that share a common priority or original filing.