Analog adaptive FIR filter having independent coefficient sets for each filter tap
First Claim
1. An analog finite impulse response filter having a filter input and a filter output, the filter comprising:
- a set of N≧
2 multipliers, each having first and second multiplier inputs and providing a corresponding multiplier output;
a set of N track and hold taps in one to one correspondence with said set of multipliers, each of said taps receiving said filter input and providing a tap output that remains constant except when said tap is triggered to set said tap output to a sample of said filter input, wherein said tap output is provided as said first input of said corresponding multiplier;
a set of N coefficient selectors in one to one correspondence with said set of multipliers, each of said coefficient selectors including N tap coefficients and providing a selected one of said tap coefficients to said second input of said corresponding multiplier, wherein said selected tap coefficient is selected according to a time delay since said corresponding tap was most recently triggered; and
a summing junction receiving all of said multiplier outputs and providing their sum as said filter output.
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Abstract
A finite impulse response filter having tap weight rotation is provided, where each tap has a corresponding coefficient selector. Each coefficient selector includes N coefficients, where N is the number of taps. Each coefficient selector provides one of its corresponding coefficients as an input to a multiplier. Each multiplier also receives an input from a triggered track and hold tap. The tap coefficients are selected according to the time delay since the corresponding track and hold tap was most recently triggered. In this manner, the tendency of multiplier gain nonuniformity to degrade filter operation in the presence of tap weight rotation is reduced. In another embodiment, an offset selector is provided, to reduce the tendency of component offsets to degrade filter operation in the presence of tap weight rotation.
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Citations
18 Claims
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1. An analog finite impulse response filter having a filter input and a filter output, the filter comprising:
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a set of N≧
2 multipliers, each having first and second multiplier inputs and providing a corresponding multiplier output;
a set of N track and hold taps in one to one correspondence with said set of multipliers, each of said taps receiving said filter input and providing a tap output that remains constant except when said tap is triggered to set said tap output to a sample of said filter input, wherein said tap output is provided as said first input of said corresponding multiplier;
a set of N coefficient selectors in one to one correspondence with said set of multipliers, each of said coefficient selectors including N tap coefficients and providing a selected one of said tap coefficients to said second input of said corresponding multiplier, wherein said selected tap coefficient is selected according to a time delay since said corresponding tap was most recently triggered; and
a summing junction receiving all of said multiplier outputs and providing their sum as said filter output. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for analog finite impulse response filtering of a filter input, the method comprising:
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providing a set of N≧
2 samples of said filter input, wherein each of said samples remains constant in time except when triggered to be set to a current sample of said filter input;
providing a set of N coefficient arrays in one to one correspondence with said samples, each of said arrays having N coefficients;
selecting from each of said coefficient arrays a selected coefficient according to a time delay since said corresponding sample was most recently triggered;
calculating a product of said selected coefficient with said corresponding sample for each of said samples; and
calculating a sum of said products and providing said sum as a filter output. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification