Producing a frequency-representative signal with rapid adjustment to frequency changes
AssigneeNational Semiconductor Corporation
InventorsGeorge Adrian Hariman, Kenji Tomiyoshi
Life of this patent
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Abstract
A feed-forward path is combined with a feed-back path to produce an output signal representation of an input signal frequency. The feed-forward path adjusts the output signal representation in response to a change in the input signal frequency, and does so in a response time that is independent of the feed-back path. Input frequencies can be represented as voltages, and first and second input frequency ranges which differ from one another can both be represented in the same range of voltages.
Claims18
An apparatus for representing a frequency, comprising:
- an input for receiving an input signal having an input frequency;
- an output for providing an output signal that represents said input frequency;
- a feed-forward path coupled between said input and said output, wherein said feed-forward path includes a voltage-to-current converter that produces a current which represents said input frequency;
- a feed-back path coupled to said output and to a node in said feed-forward path, said feed-back path having a time delay associated with operation thereof;
- and
- in response to a change in said input frequency from a first frequency value to a second frequency value, said feed-forward path operable independently of said time delay to adjust said output signal from exhibiting a first characteristic that represents said first frequency value to exhibiting a second characteristic that represents said second frequency value.
An apparatus for representing a frequency, comprising:
- an input for receiving an input signal having an input frequency;
- a frequency-to-voltage converter coupled to said input said frequency-to-voltage converter including an output and first and second frequency-to-voltage conversion circuits coupled to said output, said first frequency-to-voltage conversion circuit converting a first range of values of said input frequency into a range of voltages at said output, and said second frequency-to-voltage conversion circuit converting a second range of values of said input frequency into said range of voltages at said output, said second range of values of said input frequency differing from said first range of values of said input frequency;
- and
- a decision circuit coupled to said frequency-to-voltage converter for deciding which of said first and second frequency-to-voltage conversion circuits is to drive said output of said frequency-to-voltage converter.
A method of producing a signal representation of an input frequency, comprising:
- using a range of voltages to represent a first range of input frequencies during a first time period;
- using said range of voltages to represent a second range of input frequencies that differs from said first range of input frequencies during a second time period;
- and
- distinguishing between the first time period when said range of voltages is used to represent said first range of input frequencies and the second time period when said range of voltages is used to represent said second range of input frequencies.
Dependencies are inferred from the claim text.