US3729684A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Data demodulator employing multiple correlations and filters
Assignee: Lockheed Martin Corp
•
Filing: 1971-07-01
•
Granted: 1973-04-24
•
Expires: 1991-07-01
Abstract
Abstract A demodulator useful for demodulating multi-phase differentially coherent phase shift keyed (PSK) signals. In the four phase case, a pair of correlators operate upon the identity and non-identity of the PSK signal and two replicas of itself derived from the preceding baud or frame interval to produce first and second correlation signals. The first and second correlation signals are then filtered by means of first and second digital counter type filters with the direction of counting being controlled by corresponding ones of the correlation signal. The output of the filters are then compared with one another in sign and magnitude to detect the modulating information.
Inventors
- 👤 D Shuda
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 22:42
CPC Classifications
H; H04; H04L; H04L7/00; H04L7/02; H04L7/033; H04L7/0331; H04L27/00; H04L27/18; H04L27/22; H04L27/233; H04L27/2331
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
212 words
A demodulator for an n phase differentially coherent PSK signal where n is an integer and each phase vector represents two bits of information, said demodulator comprising a delay element for delaying the PSK signal by one baud + OR pi /n; first and second EXCLUSIVE OR or networks for correlating the PSK signal with the baud + pi /n and baud - pi /n versions of itself, respectively, to provide first and second bivalued correlation signals; synchronization means responsive to said PSK signal to provide during each baud thereof a sequence of timing pulses followed by a reset pulse the pulse sequences being substantially centered in the middle of the bauds; first and second bidirectional counters responsive to said first and second correlation signals, respectively, to count said timing pulses in a first dIrection when the associated correlation signal has one of its values and in a second direction when it has the other of its values; a comparator for comparing the signs and magnitudes of the count values in said counters after each such pulse sequence so as to detect which of the n phase vectors is encoded in each baud; and means for applying the reset pulse to said counters so as to reset them to an initial condition.
Claim 2
Dependent Claim
212 words
A demodulator for an n phase differentially coherent PSK signal where n is an integer and each phase vector represents two bits of information, said demodulator comprising a delay element for delaying the PSK signal by one baud + OR pi /n; first and second EXCLUSIVE OR or networks for correlating the PSK signal with the baud + pi /n and baud - pi /n versions of itself, respectively, to provide first and second bivalued correlation signals; synchronization means responsive to said PSK signal to provide during each baud thereof a sequence of timing pulses followed by a reset pulse the pulse sequences being substantially centered in the middle of the bauds; first and second bidirectional counters responsive to said first and second correlation signals, respectively, to count said timing pulses in a first dIrection when the associated correlation signal has one of its values and in a second direction when it has the other of its values; a comparator for comparing the signs and magnitudes of the count values in said counters after each such pulse sequence so as to detect which of the n phase vectors is encoded in each baud; and means for applying the reset pulse to said counters so as to reset them to an initial condition.
Claim 3
Dependent Claim
74 words
The invention according to claim 1 wherein said comparator includes means for producing a magnitude signal having first and second values when the count value of the first counter is greater and lesser, respectively, then the count value of the second counter, and means responsive to the signs of the count values and to the magnitude signal to produce a pair of binary signals representative of the bits encoded on the detected phase vector.
Claim 4
Dependent Claim
179 words
The invention as set forth in claim 2 wherein n + 4 and the four phase vectors are at pi /4, - pi /4, +3 pi /4 and +5 pi /4 radian referenced to zero or 2 pi radians of the carrier signal; wherein the first value of said magnitude signal is indicative of either the +3 pi /4 or the - pi /4 vector and the second value is indicative of either the + pi /4 or the +5 pi /4 vector; and wherein the binary signal producing means responds to the first value of said magnitude signal to produce said binary signal pair with values corresponding to +3 pi /4 and - pi /4 vectors when the sign of the count value of the first counter is positive and negative, respectively, and further responds to the second value of said magnitude signal to produce said binary signal pair with values corresponding to the + pi /4 and +5 pi /4 vectors when the sign of the count value of the second counter is positive and negative, respectively.
Claim 5
Dependent Claim
83 words
The invention as set forth in claim 1 wherein said delay element also delays the PSK signal by 1/3 baud; wherein a third EXCLUSIVE OR network is provided to correlate the PSK signal with the 1/3 baud delayed version of itself to produce the third correlation signal; and wherein the synchronization network includes an oscillator coupled to a pulse divider network to produce said pulses, and means responsive to the third correlation signal to synchronize said pulse divider network with said PSK signal.
Claim 6
Dependent Claim
160 words
A demodulator for detecting the information contained in a modulated carrier signal said demodulator comprising: a delay element for delaying said modulated signal and having a plurality of outputs therefrom at which differently delayed replicas of said modulated signal appear; a like plurality of EXCLUSIVE OR networks for correlating the undelayed signal with the delayed replicas of itself to provide a like plurality of bivalued correlation signals; a source of clock signals; a like plurality of bidirectional counters, each responsive to a different one of said correlation signals to count said clock signals in a first direction when the associated correlation signals have one of their values and in a second direction when it has the other of its values; a comparator network for periodically comparing the signs and magnitudes of the count values in said counters so as to detect the information encoded in said modulated signal; and means for periodically resetting each of said counters to initial conditions.
Claim 7
Dependent Claim
160 words
A demodulator for detecting the information contained in a modulated carrier signal said demodulator comprising: a delay element for delaying said modulated signal and having a plurality of outputs therefrom at which differently delayed replicas of said modulated signal appear; a like plurality of EXCLUSIVE OR networks for correlating the undelayed signal with the delayed replicas of itself to provide a like plurality of bivalued correlation signals; a source of clock signals; a like plurality of bidirectional counters, each responsive to a different one of said correlation signals to count said clock signals in a first direction when the associated correlation signals have one of their values and in a second direction when it has the other of its values; a comparator network for periodically comparing the signs and magnitudes of the count values in said counters so as to detect the information encoded in said modulated signal; and means for periodically resetting each of said counters to initial conditions.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-04-23 | 1976-10-23 | 1977-04-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-04-23 | 1980-10-23 | 1981-04-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-04-23 | 1984-10-23 | 1985-04-24 | $7700.00 | Window Closed / Lapsed |