Apparatus for clock recovery from digital data

Claim 2

A clock recovery circuit for producing a clock signal from an information signal having a data rate R and a frequency spectrum centered at f, said clock recovery circuit comprising: means for producing a converted signal by frequency-converting the information signal to a frequency f 1 ; spectral shaping filter means for filtering said converted signal to produce a filtered signal, wherein said spectral shaping filter means passes the spectral line at f 1 +R/2 while attenuating substantially all other frequency components of said converted signal; means for doubling the frequency of the spectral line signal to produce a double signal; means for converting said doubled signal back to the center frequency f, wherein the resulting signal is the recovered clock signal having a frequency R.

Claim 3

The clock recovery circuit of claim 1 wherein the means for doubling the frequency of the spectral line signal includes a nonlinear device.

Claim 4

The clock recovery circuit of claim 1 wherein the means for doubling the frequency of the spectral line signal includes zonal bandpass filter means responsive to the doubled signal for removing unwanted frequency components therefrom.

Claim 5

The clock recovery circuit of claim 1 including narrow bandpass filter means responsive to the doubled signal, wherein said narrow bandpass filter means passes only the frequency components in a narrow bandwidth around the center frequency thereof.

Claim 6

The clock recovery circuit of claim 4 wherein the narrow bandpass filter means includes a phase-locked loop.

Claim 7

The clock recovery circuit of claim 5 including means for determining the relationship between the phase of the recovered clock signal and the phase of the baseband information signal, and for producing a correction signal that is input to the phase-locked loop for changing the phase of the recovered clock signal.

Claim 8

The clock recovery circuit of claim 1 including: phase shifter means responsive to the recovered clock signal; and means for determining the relationship between the phase of the recovered clock signal and the phase of the baseband information signal, and for producing a correction signal that is input to said phase shifter for shifting the phase of the recovered clock signal.

Claim 9

The clock recovery circuit of claim 1 wherein the means for reconverting the doubled clock signal includes: means for providing an oscillating signal; mixer means having a first input terminal responsive to the doubled clock signal and a second input terminal responsive to said oscillating signal, for producing a mixed signal; filter means responsive to said mixed signal for removing unwanted frequency components therefrom to produce the recovered clock signal.

Claim 10

The clock recovery circuit of claim 1 including comparator means responsive to the recovered clock signal for sharpening the edges of thereof.

Claim 11

The clock recovery circuit of claim 1 wherein the baseband information signal is substantially bandlimited to a bandwidth of R/2.

Claim 12

A clock recovery circuit for producing a clock signal from a baseband information signal having a data rate R, said clock recovery circuit comprising: means for producing an oscillating signal; mixer means having a first input terminal responsive to the baseband information signal and a second input terminal responsive to said oscillating signal; wherein said mixer means produces a first mixed signal centered at a frequency f, wherein f is the frequency of the baseband information signal frequency plus said oscillating signal frequency, and a second mixed signal centered at a frequency of the baseband information signal frequency minus said oscillating signal frequency; filter means for removing said second mixed signal; spectral shaping filter means for filtering said converted signal to extract the spectral line signal at f+R/2; means for doubling the frequency of the spectral line signal to produce a double signal; and means for converting said doubled signal back to baseband, wherein the resulting signal is the recovered clock signal having a frequency R.

Claim 13

A clock recovery circuit for producing a clock signal from a baseband information signal having a data rate R, said clock recovery circuit comprising: means for producing an oscillating signal; mixer means having a first input terminal responsive to the baseband information signal and a second input terminal responsive to said oscillating signal; wherein said mixer means produces a first mixed signal centered at a frequency f, wherein f is the frequency of the baseband information signal frequency plus said oscillating signal frequency, and a second mixed signal centered at a frequency of the baseband information signal frequency minus said oscillating signal frequency; filter means for removing said second mixed signal; spectral shaping filter means for filtering said converted signal to extract the spectral line signal at f+R/2; means for doubling the frequency of the spectral line signal to produce a double signal; and means for converting said doubled signal back to baseband, wherein the resulting signal is the recovered clock signal having a frequency R.

Claim 14

A data detector responsive to a baseband information signal having a data rate R, for producing a detected signal, said data detector comprising: means for providing an oscillating signal having a frequency f; first mixer means having a first input terminal responsive to the baseband information signal and a second input terminal responsive to said oscillating signal; wherein said mixer means produces a first mixed signal centered at a frequency of the baseband information signal frequency plus f, and a second mixed signal centered at a frequency of the baseband information signal frequency minus f; first filter means for removing said second mixed signal; means for filtering said first mixed signal to extract the spectral line signal at f+R/2; a nonlinear device responsive to said spectral line signal for doubling the frequency thereof, to produce a doubled-frequency signal; zonal bandpass filter means responsive to said doubled-frequency signal for attenuating unwanted frequency components therein; a phase-locked loop responsive to the filtered double-frequency signal for extracting the spectral line at the frequency 2f+R, a fractionally-spaced equalizer responsive to the baseband information signal for time-shifting the baseband information signal and for producing a correction signal, wherein said correction signal is input to said phase-locked loop for changing the phase of the spectral line at 2f+R; frequency doubling means responsive to said oscillating signal for producing a doubled oscillating signal; second mixer means having a first input terminal responsive to said spectral line at 2f+R and a second input terminal responsive to said doubled oscillating signal, for producing a third mixed signal centered at a frequency of 2f+2f+R and a fourth mixed signal centered at a frequency of 2f-2f+R; second filter means for attenuating said third mixed signal; wherein said fourth mixed signal has a frequency R and represents the recovered clock signal; comparator means responsive to the recovered clock signal for shaping the edges thereof. data decision means having a first input terminal responsive to the recovered clock signal and a second input terminal responsive to the time-shifted baseband information signal for producing the detected signal.

Claim 15

A data detector responsive to a baseband information signal having a data rate R, for producing a detected signal, said data detector comprising: means for providing an oscillating signal having a frequency f; first mixer means having a first input terminal responsive to the baseband information signal and a second input terminal responsive to said oscillating signal; wherein said mixer means produces a first mixed signal centered at a frequency of the baseband information signal frequency plus f, and a second mixed signal centered at a frequency of the baseband information signal frequency minus f; first filter means for removing said second mixed signal; means for filtering said first mixed signal to extract the spectral line signal at f+R/2; a nonlinear device responsive to said spectral line signal for doubling the frequency thereof, to produce a doubled-frequency signal; zonal bandpass filter means responsive to said doubled-frequency signal for attenuating unwanted frequency components therein; a phase-locked loop responsive to the filtered double-frequency signal for extracting the spectral line at the frequency 2f+R, a fractionally-spaced equalizer responsive to the baseband information signal for time-shifting the baseband information signal and for producing a correction signal, wherein said correction signal is input to said phase-locked loop for changing the phase of the spectral line at 2f+R; frequency doubling means responsive to said oscillating signal for producing a doubled oscillating signal; second mixer means having a first input terminal responsive to said spectral line at 2f+R and a second input terminal responsive to said doubled oscillating signal, for producing a third mixed signal centered at a frequency of 2f+2f+R and a fourth mixed signal centered at a frequency of 2f-2f+R; second filter means for attenuating said third mixed signal; wherein said fourth mixed signal has a frequency R and represents the recovered clock signal; comparator means responsive to the recovered clock signal for shaping the edges thereof. data decision means having a first input terminal responsive to the recovered clock signal and a second input terminal responsive to the time-shifted baseband information signal for producing the detected signal.

Claim 16

A data detector responsive to a baseband information signal having a data rate R, for producing a detected signal, said data detector comprising; wherein the baseband information signal is bandlimited; means for producing a converted signal by frequency-converting the baseband information signal to a frequency f; means for extracting the spectral line signal at f+R/2 from said converted signal; means for doubling the frequency of the spectral line signal at f+R/2 to produce a doubled signal; means for converting said doubled signal to baseband, wherein the resulting signal is the recovered clock signal having a frequency R; means responsive to the baseband information signal at a first terminal thereof, for time shifting the baseband information signal to ensure alignment with the recovered clock signal; means responsive to the time-shifted baseband information signal and the recovered clock signal for producing the detected signal; wherein said means responsive to the baseband information signal at a first terminal is responsive to the detected signal at a second terminal, and wherein said means produces a correction signal that is input to said means for converting said doubled signal to baseband.

Claim 17

A data detector responsive to a baseband information signal having a data rate R, for producing a detected signal, said data detector comprising; wherein the baseband information signal is bandlimited; means for producing a converted signal by frequency-converting the baseband information signal to a frequency f; means for extracting the spectral line signal at f+R/2 from said converted signal; means for doubling the frequency of the spectral line signal at f+R/2 to produce a doubled signal; means for converting said doubled signal to baseband, wherein the resulting signal is the recovered clock signal having a frequency R; means responsive to the baseband information signal at a first terminal thereof, for time shifting the baseband information signal to ensure alignment with the recovered clock signal; means responsive to the time-shifted baseband information signal and the recovered clock signal for producing the detected signal; wherein said means responsive to the baseband information signal at a first terminal is responsive to the detected signal at a second terminal, and wherein said means produces a correction signal that is input to said means for converting said doubled signal to baseband.