Gain switching device with reduced error for watt meter
First Claim
1. In a switching apparatus for generating a switching function for controlling an input signal having at least a first component of a first frequency, said switching function having an error component at a frequency related to said first frequency,error reducing means for reducing errors resulting from interaction between said first component of said input signal and said error component of said switching function, said error reducing means comprising:
- first means for receiving said error component of said switching function,second means for receiving another function, andcombining means connected to said first and second means for combining said error component of said switching function and said another function to produce a second switching function having a reduced presence of said error component of said switching function and having a second component of a second frequency having a relationship to said first frequency different from the relationship of said frequency of said error component to said first frequency, said combining means providing said second switching function to said switching means thereby reducing errors due to interaction between said first component of said input signal and said error component of said switching function.
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Abstract
A gain switching apparatus for a signal is controlled by a switching function formed as a function of the signal. The apparatus is provided with a circuit for reducing errors due to common frequency components in the switching function and in the signal being switched thereby. In order to reduce DC error resulting from multiplication of the switching function by a parameter representing the switched signal, the common frequency component of the switching function is substantially eliminated and replaced by a component at a frequency which is a multiple of the common frequency. A simplified logic circuit is provided to perform the frequency multiplication and the resultant error reduction.
30 Citations
23 Claims
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1. In a switching apparatus for generating a switching function for controlling an input signal having at least a first component of a first frequency, said switching function having an error component at a frequency related to said first frequency,
error reducing means for reducing errors resulting from interaction between said first component of said input signal and said error component of said switching function, said error reducing means comprising: -
first means for receiving said error component of said switching function, second means for receiving another function, and combining means connected to said first and second means for combining said error component of said switching function and said another function to produce a second switching function having a reduced presence of said error component of said switching function and having a second component of a second frequency having a relationship to said first frequency different from the relationship of said frequency of said error component to said first frequency, said combining means providing said second switching function to said switching means thereby reducing errors due to interaction between said first component of said input signal and said error component of said switching function. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A gain switching arrangement for providing a plurality of gains to a varying input signal comprising:
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(a) first path means for conveying said input signal through a first gain producing circuit and for providing a first gain thereto, (b) second path means for conveying said input signal through a second circuit having a second gain different from said first gain, (c) output means, (d) switching means for selectively switching said input signal through said first or said second path to said output means responsively to a switching signal, and (e) control means for generating said switching signal and for controlling said switching means to select a specific path for conveying said input signal to said output means, (f) said control means including (i) comparing means for comparing an instantaneous value of said input signal with a threshold value and (ii) signal providing means responsive to said comparing means for providing said switching signal and for causing said first or second paths to be selected by said switching means for conveying said input signal to said output means. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23)
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Specification