EP0369406A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Coherent PSK demodulator using bit error rate and S/N ratio to establish synchronization
Assignee: NEC Corp
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Filing: 1989-11-14
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Granted: —
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Expires: 2009-11-14
Abstract
Abstract In a coherent M-ary PSK demodulator, an M-ary PSK detector (1) demodulates a received M-ary PSK modulated convolutional code with a carrier recovered by a voltage-controlled oscillator to produce first and second channels of demodulated convolutional codes. A convolutional decoder (7) decodes the signals of the first and second channels while correcting bit errors. An error rate detector is provided for detecting when the number of such errors occurring during a specified period of time is smaller than a predetermined value and generates a signal indicating that the convolutional decoder (7) is synchronized with the demodulated signals. The power levels of signal and noise components of the demodulated channels are detected by a power detector (11). In a frequency control circuit, a series of VCO control signals of a different value are generated as candidates for precise synchronization in response to the signal from the error rate detector in order to synchronize the PSK detector (1) successively at the candidate frequencies, and signal-to-noise ratios are successively derived from the outputs of the power detector (11). A maximum value of the derived signal-to-noise ratios is then detected and one of the candidate VCO control signals which corresponds to the detected maximum signal-to-noise ratio is adopted as a valid VCO control signal.
Inventors
- 👤 Motoya C/O Nec Corporation Iwasaki
- 👤 Susumu C/O Nec Corporation Otani
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-07 20:58
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/18; H04L27/22; H04L27/227; H04L27/2271; H04L27/2273; H04L27/186; H04L27/0014; H04L2027/0044; H04L2027/0063; H04L2027/0067; H04L2027/0071; H04L2027/0073; H04L2027/0083; H04L2027/0089; H04L2027/0093
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
273 words
A coherent PSK (phase shift keying) demodulator comprising: PSK detector means for demodulating a received PSK modulated convolutional code with a recovered carrier to produce first- and second-channel convolutional codes; carrier recovery means for recovering said carrier having a phase variable in accordance with a phase control signal derived from said first- and second-channel convolutional codes and a frequency variable in accordance with a frequency control signal applied thereto; convolutional decoder means for decoding said first- and second-channel convolutional codes, said decoder means being capable of correcting errors in said convolutional codes; error rate detector means connected to said convolutional decoder means for detecting said errors generated during a specified period of time are smaller than a predetermined value to generate an output signal indicating that said convolutional decoder means is synchronized with said first- and second-channel convolutional codes; power detector means connected to said PSK detector means for detecting power levels of a signal component and a noise component of one of said first- and second-channel convolutional codes; and frequency control means for performing the steps of (a) successively generating said frequency control signal of different values in response to an occurrence of the output signal of said error rate detector means to cause the recovered carrier to successively assume different frequencies, (b) successively deriving signal-to-noise ratios from the detected power levels which result from demodulation of the received PSK modulated convolutional code with the carrier of the different frequency values, and (c) detecting a maximum value of said derived signal-to-noise ratios to generate the frequency control signal having one of said different values which corresponds to the detected maximum signal-to-noise ratio.
Claim 2
Dependent Claim
273 words
A coherent PSK (phase shift keying) demodulator comprising: PSK detector means for demodulating a received PSK modulated convolutional code with a recovered carrier to produce first- and second-channel convolutional codes; carrier recovery means for recovering said carrier having a phase variable in accordance with a phase control signal derived from said first- and second-channel convolutional codes and a frequency variable in accordance with a frequency control signal applied thereto; convolutional decoder means for decoding said first- and second-channel convolutional codes, said decoder means being capable of correcting errors in said convolutional codes; error rate detector means connected to said convolutional decoder means for detecting said errors generated during a specified period of time are smaller than a predetermined value to generate an output signal indicating that said convolutional decoder means is synchronized with said first- and second-channel convolutional codes; power detector means connected to said PSK detector means for detecting power levels of a signal component and a noise component of one of said first- and second-channel convolutional codes; and frequency control means for performing the steps of (a) successively generating said frequency control signal of different values in response to an occurrence of the output signal of said error rate detector means to cause the recovered carrier to successively assume different frequencies, (b) successively deriving signal-to-noise ratios from the detected power levels which result from demodulation of the received PSK modulated convolutional code with the carrier of the different frequency values, and (c) detecting a maximum value of said derived signal-to-noise ratios to generate the frequency control signal having one of said different values which corresponds to the detected maximum signal-to-noise ratio.
Claim 3
Dependent Claim
49 words
A coherent PSK demodulator as claimed in claim 1, further comprising phase shifter means connected between said PSK detector means and said convolutional decoder means for correcting the phase of said first- and second-channel convolutional codes in the absence of the output signal of said error rate detector means.
Claim 4
Dependent Claim
60 words
A coherent PSK demodulator as claimed in claim 1 or 2, wherein said frequency control means repeats the steps (a), (b) and (c) to derive a plurality of said frequency control signals as candidates for a most likelihood control parameter, detects two of said candidates having an equal value, and generates said frequency control signal corresponding to the detected candidates.
Claim 5
Independent Claim
179 words
A method of establishing synchronization between a received PSK (phase shift keying) modulated convolutional code and a recovered carrier, comprising the steps of: a) demodulating said received PSK modulated convolutional code with said recovered carrier to produce first- and second-channel convolutional codes; b) controlling the phase of said recovered carrier in accordance with a phase difference between said first- and second-channel convolutional codes; c) decoding said first- and second-channel convolutional codes while correcting errors in said convolutional codes; d) detecting power levels of a signal component and a noise component of one of said first- and second-channel convolutional codes; and e) detecting if said errors generated during a specified period of time are smaller than a predetermined value; f) if said errors are detected as being smaller than said predetermined value by the step (e), successively varying the frequency of the recovered carrier; g) successively deriving signal-to-noise ratios from the detected power levels; and h) detecting a maximum value of said derived signal-to-noise ratios and maintaining said recovered carrier at a frequency corresponding to the detected maximum signal-to-noise ratio.
Claim 6
Independent Claim
179 words
A method of establishing synchronization between a received PSK (phase shift keying) modulated convolutional code and a recovered carrier, comprising the steps of: a) demodulating said received PSK modulated convolutional code with said recovered carrier to produce first- and second-channel convolutional codes; b) controlling the phase of said recovered carrier in accordance with a phase difference between said first- and second-channel convolutional codes; c) decoding said first- and second-channel convolutional codes while correcting errors in said convolutional codes; d) detecting power levels of a signal component and a noise component of one of said first- and second-channel convolutional codes; and e) detecting if said errors generated during a specified period of time are smaller than a predetermined value; f) if said errors are detected as being smaller than said predetermined value by the step (e), successively varying the frequency of the recovered carrier; g) successively deriving signal-to-noise ratios from the detected power levels; and h) detecting a maximum value of said derived signal-to-noise ratios and maintaining said recovered carrier at a frequency corresponding to the detected maximum signal-to-noise ratio.
Claim 7
Dependent Claim
39 words
A method as claimed in claim 4, further comprising the step of correcting the phase of said first- and second-channel convolutional codes if said errors are not detected as being smaller than said predetermined value by the step (e).
Claim 8
Dependent Claim
72 words
A method as claimed in claim 4 or 5, further comprising the steps of: repeating the steps (f), (g) and (h) to successively vary the frequency of said recovered carrier; storing a plurality of frequency values of said recovered carrier as candidates for a most likelihood frequency; detecting two of said stored frequency values having an equal value; and controlling said recovered carrier at a frequency corresponding to said detected frequency values.
References Cited (Backward Citations)
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