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US 7,555,081 B2Granted
Log-sampled filter system
AssigneeHarman International Industries, Incorporated
InventorD. Broadus Keele, Jr.
Life of this patent
Estimating the term…
Abstract
This invention provides a filter system which may be implemented with less hardware and software resources than traditional filters. In addition, the filter system structure reduces the complexities typically associated with filter design by permitting direct specification of the filter frequency response. Thus, the filter system may adaptively change the filter frequency response on the fly without incurring excessive time or computational costs. The filter system may provide a filtered signal output to any subsequent processing system, such as a voice recognition system or audio reproduction system.
Claims44
A multi-rate filter system comprising:
- an input channel configured to receive an input signal;
- an output channel configured to output a filtered signal;
- a plurality of multi-rate filter sections coupled between the input channel and the output channel, at least one of the multi-rate filter sections comprising:
- a downsampler including a downsampler input and a downsampler output connected to a subsequent multi-rate filter section;
- a finite impulse response (FIR) filter channel coupled to the downsampler output, the finite impulse response (FIR) filter channel comprising:
- a real finite impulse response (FIR) filter interpolator;
- an imaginary finite impulse response (FIR) filter interpolator coupled in parallel with the real finite impulse response (FIR) filter interpolator;
- a real gain element coupled to the real finite impulse response (FIR) filter interpolator;
- and
- an imaginary gain element coupled to the imaginary finite impulse response (FIR) filter interpolator;
- a summer connected to the finite impulse response (FIR) filter channel;
- and
- an upsampler connected to the summer, the upsampler comprising an upsampler input and an upsampler output connected to either a prior multi-rate filter section or to an output signal summer.
10 more elements
A method of filtering a signal, the method comprising:
- processing an input signal through a plurality of multi-rate filter sections, the processing in at least one of the multi-rate filter sections comprising:
- downsampling to generate a reduced rate signal;
- filtering the reduced rate signal through a real finite impulse response (FIR) filter interpolator and applying a real weight to the reduced rate signal to generate a real weighted filter output;
- filtering the reduced rate signal through an imaginary finite impulse response (FIR) filter interpolator and applying an imaginary weight to the imaginary reduced rate signal to generate an imaginary weighted filter output;
- summing the real weighted filter output and the imaginary weighted filtered output to generate a finite impulse response (FIR) channel output;
- upsampling the finite impulse response (FIR) channel output to generate an increased rate signal;
- providing the reduced rate signal to a subsequent multi-rate filter section;
- and
- providing the increased rate signal to either a prior multi-rate filter section or to a output signal summer.
6 more elements
A machine readable medium comprising instructions executable by a processor, the machine readable medium comprising:
- instructions to downsample and generate a reduced rate signal;
- instructions to filter the reduced rate signal through a real finite impulse response (FIR) filter interpolator and apply a real weight to generate a real weighted filter output;
- instructions to filter the reduced rate signal through an imaginary finite impulse response (FIR) filter interpolator and apply an imaginary weight to the imaginary finite impulse response (FIR) filter interpolator output to generate an imaginary weighted filter output;
- instructions to sum the real weighted filter output and the imaginary weighted filtered output to generate a finite impulse response (FIR) channel output;
- instructions to upsampling the finite impulse response (FIR) channel output to generate an increased rate signal;
- instructions to provide the reduced rate signal to a subsequent multi-rate filter section;
- and
- instructions to provide the increased rate signal to either a prior multi-rate filter section or to a output signal summer.
5 more elements
A filter comprising:
- an input channel configured to receive an input signal;
- an output channel configured to output a filtered signal;
- multiple finite impulse response (FIR) filter channels which implement a filter response, the finite impulse response (FIR) filter channels coupled to the input channel and to a signal summer, where the signal summer generates the filtered signal, and where each of the finite impulse response (FIR) filter channels comprises:
- a filter gain element;
- a real finite impulse response (FIR) filter interpolator coupled to the filter gain element;
- and
- an imaginary finite impulse response (FIR) filter interpolator coupled to the filter gain element.
4 more elements
Dependencies are inferred from the claim text.