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US 5,692,014 AGranted
Subsampled carrier recovery for high data rate demodulators
AssigneeTRW Inc.
InventorsJack K. Basham, Keith K. Yamashiro, Pascal G. Finkenbeiner, Thomas J. Kolze
Life of this patent
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Abstract
A high performance, low cost technique for carrier recovery and tracking of high rate demodulator (>200 Mbps to multi-gigabits per second) system is presented. The locally generated carrier is held in phase locked synchronism with the incoming modulated carrier through a carrier recovery scheme in which the modulated data is detected and subsampled using the bit synchronizing circuitry to provide a strobe signal for subsampling. The voltage levels of the subsampled data are analyzed to determine a phase error signal. The subsampled data are used to address a lookup table of error values stored in memory.
Claims34
A method of processing an information carrying input signal impressed on a carrier, comprising:
- detecting the input signal using an electrically controlled oscillator to generate a local carrier signal and extracting the local carrier signal from the input signal to recover a detected analog signal, said analog signal having a symbol rate;
- producing a recovered clock signal in synchronism with the symbol rate of said analog signal;
- subsampling the analog signal in an analog to digital conversion process at a sampling rate which is a function of said recovered clock signal, said sampling rate being lower than said symbol rate by a predetermined factor to generate a converted digital signal;
- and
- using the converted digital signal to produce a feedback signal used to control the electrically controlled oscillator and to thereby lock the frequency and phase of the local carrier signal to that of the carrier of the input signal.
2 more elements
An apparatus for carrier recovery in a communication receiver, comprising:
- a detector circuit for extracting a detected analog signal from an incoming modulated signal, said detected analog signal having a symbol rate;
- a synchronizing circuit coupled to said detector circuit for receiving said detected analog signal and producing a synchronized clock signal having a frequency lower than the symbol rate by a predetermined factor;
- a subsampling circuit coupled to said synchronizing circuit and to said detector circuit for producing a subsampled signal at a rate corresponding to said synchronized clock signal;
- a processing circuit coupled to said subsampling circuit responsive of said subsampled signal for producing a feedback signal based on said subsampled signal;
- and
- an oscillator circuit coupled to said processing circuit and responsive of said feedback signal, said oscillator circuit producing a recovered carrier signal in accordance with said feedback signal, and said oscillator circuit providing said recovered carrier signal to said detector circuit.
3 more elements
A method of processing an information carrying input signal impressed on a carrier, comprising:
- detecting the input signal using an electrically controlled oscillator to generate a local carrier signal and extracting the local carrier signal from the input signal to recover a detected analog signal, said analog signal having a symbol rate;
- producing a recovered clock signal in synchronism with the symbol rate of said analog signal;
- subsampling the analog signal at a sampling rate lower than the symbol rate by a predetermined factor to produce a subsampled signal;
- using the subsampled signal to recover a carrier;
- using the recovered clock signal to strobe the detected analog signal through an analog to digital conversion process whereby the analog signal is converted to a digital signal;
- using the digital signal to produce a feedback signal used to control the frequency electrically controlled oscillator and to thereby lock the frequency and phase of the local carrier signal to that of the carrier of the input signal.
3 more elements
A method of processing information carrying input signals impressed on a carrier by way of a plurality of different modulations types, said method comprising:
- detecting an input signal using an electrically controlled oscillator to generate a local carrier signal and extracting the local carrier signal from the input signal to recover a detected analog signal;
- subsampling the analog signal in an analog digital conversion process to convert the analog signal to a digital signal;
- storing a plurality of different predetermined phase error data corresponding to the plurality of different modulation types as remote lookup tables in a memory;
- based on the modulation type of the input signal, selectively accessing one of said tables corresponding to the modulation type of the input signal;
- and
- using said digital signal to address the memory of the selected table to obtain given feedback error data for use in producing a feedback signal to control the frequency of the electrically controlled oscillator to thereby lock the frequency of the local carrier signal to that of the carrier of the input signal.
3 more elements
A method of processing information carrying input signals impressed on a carrier by way of a plurality of different modulation types, said method comprising:
- detecting an input signal using an electrically controlled oscillator to generate a local carrier signal;
- and extracting the local carrier signal from the input signal to recover a detected analog signal having a data frequency;
- subsampling the analog signal at a sampling frequency lower than said data frequency to produce a subsampled signal;
- using the subsampled signal to recover a carrier;
- strobing the detected analog signal through an analog-to-digital conversion process to convert the analog signal to a digital signal;
- storing a plurality of different predetermined phase error data corresponding to the plurality of different modulation types as lookup tables in a memory;
- based on the modulation type of the input signal, selectively accessing one of said tables corresponding to the modulation type of the input signal;
- and
- using said digital signal to address the memory of the selected table to obtain one of said phase error data for use in producing a feedback signal to control the electrically controlled oscillator to thereby lock the frequency of the local carrier signal to that of the carrier of the input signal.
6 more elements
A method of processing an information carrying input signal impressed on a carrier, comprising:
- detecting the input signal using an electrically controlled oscillator to generate a local carrier signal and extracting the local carrier signal from the input signal to recover a detected analog signal, said analog signal having a symbol rate;
- producing a recovered clock signal in synchronism with the symbol rate of said analog signal;
- subsampling the analog signal in an analog to digital conversion process at a sampling rate which is a function of said recovered clock signal to generate a converted digital signal, said sampling rate being lower than said symbol rate by a factor of at least 1/N, where N is greater than 1, said converted digital signal containing frequency and phase attributes relating to the carrier;
- and
- using the converted digital signal to produce a feedback signal used to control the electrically controlled oscillator and to thereby lock the frequency and phase of the local carrier signal to that of the carrier of the input signal.
2 more elements
Dependencies are inferred from the claim text.