Electrical computers: arithmetic processing and calculating – Electrical digital calculating computer – Particular function performed
Reexamination Certificate
1998-12-02
2001-10-30
Malzahn, David H. (Department: 2121)
Electrical computers: arithmetic processing and calculating
Electrical digital calculating computer
Particular function performed
C708S319000
Reexamination Certificate
active
06311203
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multiplication device for performing multiplication on a multiplicand and plural fixed coefficients and for subsequently outputting the product obtained for a selected one of the fixed coefficients, and also to a fixed coefficient type finite impulse response (FIR) digital filter having a plurality of such multipliers.
2. Description of the Related Art
A multiplication device used in a fixed coefficient FIR digital filter is well known which performs multiplication on a multiplicand and plural fixed coefficients find then outputs the result (product) obtained for a selected one of the fixed coefficients.
FIG. 11
shows the prior art multiplication device 500 for multiplying a common multiplicand X by two fixed coefficients C1 and C2 and then outputting one of the two results, that is, the result obtained for a selected one of the coefficients. As shown in
FIG. 11
, this multiplication device
500
has two multipliers
50
and
51
. One multiplier
50
multiplies the multiplicand X by a fixed coefficient C1 and outputs the result to a selector
52
. The other multiplier
51
multiplies the multiplicand X by another fixed coefficient C2 and likewise outputs the result to the selector
52
. The selector
52
selects one of the multipliers
50
and
51
based on a selection control signal, which is set according to the fixed coefficient to be used, and passes the result from the selected multiplier
50
or
51
as the product of the multiplication.
The prior art multiplication device
500
as thus described requires the same number of multipliers as the fixed coefficients to be dealt with thereby. An obvious problem with this configuration is that the size of the multiplication device necessarily increases as the number of fixed coefficients increases.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a multiplication device having a simplified configuration for performing multiplication on a common multiplicand and two fixed coefficients and then outputting the result of the multiplication for a selected one of the coefficients.
It is a further object of the present invention to provide a fixed coefficient taipe FIR digital filter comprising a plurality of such multiplication devices.
A multiplication device designed to accomplish the foregoing objects of the present invention multiples a multiplicand X and two fixed coefficients C1 and C2, where C1>C2, and outputs the result of the multiplication for a selected one of the fixed coefficient C1 or C2. This multiplication device comprises a multiplier for multiplying the multiplicand X and the average CA of the fixed coefficients C1 and C2; a shift register unit comprising one or more shift registers for shifting the multiplicand X up according to the position of a “1” bit in a remainder coefficient, which is obtained by subtracting the average CA from the fixed coefficient C1, and an adder for obtaining the arithmetic sum of bit shifted data output from the one or more shift registers; and a selection means for selecting one of the fixed coefficients C1 or C2 based or a specific control signal.
When the fixed coefficient C1 is selected, the selection means outputs the sum of the product from the multiplier and the arithmetic sum obtained by the shift register unit. When the fixed coefficient C2 is selected, the selection means outputs the difference between the product from the multiplier minus the arithmetic sum obtained by the shift register unit.
By thus using a multiplier and a shift register unit that is simpler than the multiplier in contrast to the prior art device that requires the use of the two multiplies, the multiplication device according to the present invention can be made compact and at lower cost.
If in place of the multiplier a shift register unit comprising one or more shift registers for shifting the multiplicand X up according to the position of a “1” bit in the average CA, and an adder for obtaining the sum of the shifted data output from the one or more shift registers are used, the multiplication device of the invention can be made on an even smaller scale and lower cost.
A fixed coefficient FIR digital filter having a plurality of multiplication devices according to the invention is also provided. This digital filter comprises a shift register for shifting the multiplicand X up according to the position of a “1” bit in bit data common to two or more remainder coefficients used by the plurality of multiplication devices, and a shift register for shifting the multiplicand K up according to a position of a “1” bit in bit data obtained by subtracting said common bit data from a remainder coefficient. Redundant shift registers can thus be eliminated from the plural shift register units, and the digital filter cain thus be reduced in scale.
REFERENCES:
patent: 5159567 (1992-10-01), Gobert
patent: 5243552 (1993-09-01), Asakura
patent: 5313414 (1994-05-01), Yang et al.
patent: 5815422 (1998-09-01), Dockser
patent: 5841684 (1998-11-01), Dockser
patent: 6141674 (2000-10-01), Unkrich et al.
Murakami Shuji
Wada Yasushi
Malzahn David H.
McDermott & Will & Emery
Mitsubishi Denki & Kabushiki Kaisha
LandOfFree
Multiplier, and fixed coefficient FIR digital filter having... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Multiplier, and fixed coefficient FIR digital filter having..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multiplier, and fixed coefficient FIR digital filter having... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2611625