Analog-to-digital conversion

Claim 3

The system set forth in claim 1 wherein the control signal is a digital signal.

Claim 4

The system set forth in Claim 2 characterized in that said first means comprises: means for changing the level of said digital control signal at a rate substantially equal to said reference frequency.

Claim 5

The system set forth in Claim 2 characterized in that said first means comprises: means for changing the magnitude of said digital control signal at a first rate; and means for changing the polarity of said digital control signal with respect to said reference level at a second rate wherein said second rate is not lower than said first rate.

Claim 6

The system set forth in Claim 4 characterized in that said first rate is a subharmonic frequency of said reference frequency.

Claim 7

The system as set forth in claim 1,2,3,4 or 5 characterized by a filter coupled to said analog-to-digital converter for attenuating the components of said digital samples occupying frequencies that are subharmonic to said predetermined band of frequencies to increase the quantization resolution of said digital samples.

Claim 8

The system set forth in Claim 5 characterized in that said analog-to-digital converter comprises a plurality of serially connected resistance means coupled to receive said reference signal thereacross, a plurality of comparators having respective first and second inputs, means for coupling respective ones of said first inputs to successive interconnections of said plurality of resistance means, and means for coupling said analog signal to said second inputs of said plurality of comparators; and said first means comprises: a source of first clocking signals having a rate substantially equal to said first rate; a source of second clocking signals having rate substantially equal to said second rate; and said second means comprises first and second serially connected further resistance means, coupled between said plurality of serially connected resistance means and said source of reference signal; a first controllable switching means coupled to said first further resistance means and responsive to said first clocking signal for selectively providing a connection thereacross; and a second controllable switching means coupled to said second further resistance means and responsive to said second clocking signal for selectively providing a connection thereacross.

Claim 9

The system εs set forth in claim 1,2,3,4 or 5 characterized in that said first means comprises: a source clocking signal having a frequency substantially equal to a subharmonic of said reference frequency; a counter, responsive to said clocking signal for developing digital values representing the number of clock pulses that have been applied to said counter; controllable complementing means coupled to said counter and responsive to said clocking signal for selectively complementing the digital values provided by said counter; and said second means comprises: digital-to-analog conversion means coupled to said complementing means for generating a dither signal representing the digital values provided by said complementary means; and means coupled to said digital-to-analog conversion means, and to said analog-to-digital converter for adding said dither signal to said analog signal.

Claim 10

In a digital television receiver including a source of analog composite video signals having luminance and chrominance signal components including a color reference burst signal component, apparatus characterized by means for generating a dither signal having a plurality of successive levels over a predetermined number of sample intervals, said levels having monotonically changing magnitudes and successive levels having polarities which alternate with respect to a predetermined reference level, said levels changing at a rate substantially equal to the frequency of said color burst reference signal; a source of sampling clock signal; an analog-to-digital converter responsive to said sampling clock signal for developing samples of said analog signal and for providing digital samples corresponding to the amplitude of said analog samples; Claim 9 continued-- means coupled to said dither signal generating means and to said analog-to-digital converter for changing the correspondence between the magnitudes of said digital samples and said analog samples by amounts proportional to the values of said dither signals; and filtering means coupled to said analog-to-digital converter for averaging predetermined ones of said digital samples to attenuate components of said digital samples occupying frequencies subharmonic to said color reference burst signal and to increase the quantization resolution of said digital samples.