Frequency divider circuit
First Claim
1. Frequency divider circuit for divisors consisting of an integral part and a fractional part which is designed in the manner of a rate multiplier and comprises:
- a digital first accumulator including a clocked data register and an m-bit first adder having a first input presented with an m-bit first digital word corresponding to the fractional part of the divisor, and having a second input fed from the output of said data register, the input of said data register being connected to the output of said first adder said first accumulator having a sum output;
an n-bit second having a first input receiving an n-bit second digital word corresponding to the integral part of said divisor and having a second input connected to the carry output of said first adder;
an n+1 bit third adder having a first input coupled to the output of said second adder, said third adder having a second input and an output;
a subtracter having its minuend input coupled to the output of said third adder output, said subtracter having a subtrahend input and an output;
a presettable counter having its preset input coupled to the output of said subtracter output, and having a count input receiving a signal to be frequency divided;
said counter having a counter output at which a pulse occurs after a number of pulses equal to the value applied to said preset input, output pulses at said counter output being the frequency-divided signal;
said frequency divided signal clocking said data register, and;
an r-bit second accumulator, wherein 1≦
r≦
m, having an input receiving the r most significant output bits of said first accumulator sum output, and having a carry output coupled to a second input of said third adder and coupled to the subtrahend input of said subtracter; and
a delay means disposed between said second accumulator carry output and said subtracter subtrahend input, said delay means having a delay equal to the period of said frequency divided signal.
1 Assignment
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Accused Products
Abstract
A divider-by-factor frequency divider circuit is described. The rate-multiplier principle of eliminating pulses as regularly as possible from a number of pulses of the signal to be frequency-divided is modified so that low-frequency variations in the frequency-divided signal are reduced at the expense of an increase in higher-frequency variations. This modification is achieved through the addition of a second accumulator, a pair of adders, a subtracter and a presettable counter to the accumulator of a frequency divider circuit. A rate multiplier with a coloring characteristic inverse to pink noise is thereby obtained.
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Citations
7 Claims
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1. Frequency divider circuit for divisors consisting of an integral part and a fractional part which is designed in the manner of a rate multiplier and comprises:
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a digital first accumulator including a clocked data register and an m-bit first adder having a first input presented with an m-bit first digital word corresponding to the fractional part of the divisor, and having a second input fed from the output of said data register, the input of said data register being connected to the output of said first adder said first accumulator having a sum output; an n-bit second having a first input receiving an n-bit second digital word corresponding to the integral part of said divisor and having a second input connected to the carry output of said first adder; an n+1 bit third adder having a first input coupled to the output of said second adder, said third adder having a second input and an output; a subtracter having its minuend input coupled to the output of said third adder output, said subtracter having a subtrahend input and an output; a presettable counter having its preset input coupled to the output of said subtracter output, and having a count input receiving a signal to be frequency divided; said counter having a counter output at which a pulse occurs after a number of pulses equal to the value applied to said preset input, output pulses at said counter output being the frequency-divided signal; said frequency divided signal clocking said data register, and; an r-bit second accumulator, wherein 1≦
r≦
m, having an input receiving the r most significant output bits of said first accumulator sum output, and having a carry output coupled to a second input of said third adder and coupled to the subtrahend input of said subtracter; anda delay means disposed between said second accumulator carry output and said subtracter subtrahend input, said delay means having a delay equal to the period of said frequency divided signal. - View Dependent Claims (2, 3)
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4. An adjustable frequency divider for use in a phase-locked loop, said frequency divider comprising:
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a digital first accumulator having a first input receiving an m-bit first digital word corresponding to the fractional part of the divisor, said digital first accumulator having a first sum output and a first carry output; a digital second accumulator having a first input coupled to said first sum output and receiving the r most significant bits of said first sum output, said second digital accumulator having a second sum output and a second carry output; an n-bit second adder having a first input receiving an n-bit second digital word corresponding to the integral part of said divisor and having a second input coupled to said first carry output; an n+1 bit third adder having a first input receiving the output of said second adder, and a second input receiving said second carry output; delay means; a subtracter having it minuend input coupled to the output of said third adder and its subtrahend input coupled to said second carry output by said delay means; a presettable counter having its preset input coupled to the output of said subtracter, a count input receiving the signal to be frequency divided and an output, said counter output being the frequency divided signal. - View Dependent Claims (5, 6, 7)
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Specification