Method and apparatus for recovering a signal from a charge transfer device
AssigneeEastman Kodak Company
InventorL. Nevil Davy
Life of this patent
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Abstract
Relatively noise-free information signals are recovered from a charge transfer device by demodulating sideband components of the output signal of the device at a selected harmonic of the pulse output frequency of the device. In a further refinement of the invention, the relative duty cycles between the clock signals employed to operate the device and the output signal from the device are chosen such that a minimum of power from the clock signals is present at the selected harmonic.
Claims8
Apparatus for recovering a baseband signal from the output signal produced by a charge transfer device, said charge transfer device being driven by periodic clock signals, to move a serial train of charge packets, representing periodic samples of a baseband signal, to an output location, and including output circuit means for sensing said serial train of charge packets at said output location and producing in response thereto a pulse amplitude modulated signal having a pulse repetition frequency f.sub.c, said pulse amplitude modulated signal comprising a baseband component and a series of sideband components disposed about harmonics of the pulse repetition frequency of said output signal, said signal recovery apparatus comprising:
- means connected to said output circuit means to receive said output signal for demodulating the sideband components of said output said signal disposed about a selected frequency Nf.sub.c, where N is an integer, to produce a detected signal having a baseband component representing the baseband component of said output signal and a series of sideband components;
- and
- low pass filter means connected to said demodulating means to receive said detected signal for passing only said baseband component of said detected signal.
A method for recovering a baseband signal from the output signal produced by a charge transfer device, said charge transfer device being driven by periodic clock signals, to move a serial train of charge packets, representing periodic samples of said baseband signal, to an output location, and including output circuit means for sensing said serial train of charge packets at said output location and producing in response thereto a pulse amplitude modulated signal, said pulse amplitude modulated signal having a pulse repetition frequency f.sub.c and comprising a baseband component and series of upper and lower sideband components disposed about harmonics of the pulse repetition frequency, said signal recovery method comprising the steps of:
- demodulating the sideband components disposed about a selected frequency Nf.sub.c, where N is an integer, to produce a detected signal having a baseband component representing the baseband component of said output signal and a series of sideband components;
- and
- low pass filtering said detected signal to remove said sideband components and recover said baseband component of said detected signal.
Dependencies are inferred from the claim text.