Multi-Rate Implementation Without High-Pass Filter
First Claim
1. An improved multi-rate digital filter comprising:
- a first path including a full-rate Finite Impulse Response (FIR) filter FIRF, the full-rate filter FIRF receiving and filtering an input signal to produce a filtered full-rate signal;
a second path in parallel to the first path and also receiving the input signal, the second path sequentially comprising;
a down sampler processing the input signal to produce a reduced-rate signal;
a reduced-rate FIR filter FIRR in signal communication with the down sampler to receive and processing the reduced-rate signal to produce a filtered reduced-rate signal; and
an up sampler in signal communication with the reduced-rate filter FIRR to receive and process the filtered reduced-rate signal and to provide an up sampled filtered signal; and
a summer in signal communication with the full-rate filter FIRF to receive the filtered full-rate signal and in signal communication with the reduced-rate filter FIRR to receive the up sampled filtered signal, the summer summing the filtered full-rate signal and the up sampled filtered signal to provide a filtered signal.
6 Assignments
0 Petitions
Accused Products
Abstract
A filtering method approximates a target Finite Impulse Response (FIR) (or transversal) filter and reduces computational requirements by eliminating high pass filtering required by known multi-rate filters. An input signal is copied into two identical signals and processed in parallel by a full-rate path, and by a reduced-rate path. Parallel filters are computed and applied in each path, the reduced-rate signal is up-sampled, and the two signals summed. The high pass filter required by known multi-rate filters is eliminated and the low pass filter in the prior art is implicit in a down sampling. Linear phase FIR filters are used for down and up sampling, resulting in constant group delay. Added benefits include the option of zero added latency through the filtering and the constant group delay added to the target FIR. The user may choose criteria such as minimum resolution in each band.
-
Citations
19 Claims
-
1. An improved multi-rate digital filter comprising:
-
a first path including a full-rate Finite Impulse Response (FIR) filter FIRF, the full-rate filter FIRF receiving and filtering an input signal to produce a filtered full-rate signal; a second path in parallel to the first path and also receiving the input signal, the second path sequentially comprising; a down sampler processing the input signal to produce a reduced-rate signal; a reduced-rate FIR filter FIRR in signal communication with the down sampler to receive and processing the reduced-rate signal to produce a filtered reduced-rate signal; and an up sampler in signal communication with the reduced-rate filter FIRR to receive and process the filtered reduced-rate signal and to provide an up sampled filtered signal; and a summer in signal communication with the full-rate filter FIRF to receive the filtered full-rate signal and in signal communication with the reduced-rate filter FIRR to receive the up sampled filtered signal, the summer summing the filtered full-rate signal and the up sampled filtered signal to provide a filtered signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
-
-
11. A method for filtering a signal, the method comprising:
-
providing an input signal to a full-rate a Finite Impulse Response (FIR) filter FIRF, filtering the input signal in the full-rate filter FIRF to produce a filtered full-rate signal; providing the input signal to a down sampler; processing the input signal in the down sampler to produce a reduced-rate signal; providing the reduced-rate signal to a reduced-rate FIR filter FIRR; processing the reduced-rate signal in the reduced-rate filter FIRR to produce a filtered reduced-rate signal; providing the filtered reduced-rate signal to an up-sampler; processing the filtered reduced-rate signal in the up-sampler to provide a up-sampled filtered signal; providing the filtered full-rate signal and the up-sampled filtered signal to a summer; and summing the filtered full-rate signal and the up sampled filtered signal in - View Dependent Claims (12, 13, 14, 15, 16, 17, 18)
-
-
19. A method for filtering a signal, the method comprising:
-
designing a full-rate filter using the steps of; choosing a target Finite Impulse Response (FIR) filter of length N to be modeled; designing a window W of length M used to create a full-rate filter FIRF; and term by term multiplying the window W times the first M terms of the target FIR filter to create the full-rate filter FIRF of length M; providing an input signal to the full-rate filter FIRF; filtering the input signal in the full-rate filter FIRF to produce a filtered full-rate signal; designing a reduced-rate filter using the steps of; selecting a down sampling rate; designing an anti-aliasing filter A to control aliasing due to the down-sampling; subtracting the windowed full-rate filter FIRF from the target FIR filter to obtain a residual filter R of length N; removing the leading zeros from the residual filter R to obtain a shortened residual filter; convolving the shortened residual filter with the anti-aliasing filter A; and decimating the result of the convolution to create a reduced-rate filter FIRR; providing the input signal to a down sampler; processing the input signal in the down sampler to produce a reduced-rate signal; providing the reduced-rate signal to a reduced-rate filter FIRR; processing the reduced-rate signal in the reduced-rate filter FIRR to produce a filtered reduced-rate signal; providing the filtered reduced-rate signal to an up-sampler; processing the filtered reduced-rate signal in the up-sampler to provide an up-sampled filtered signal; providing the filtered full-rate signal and the up-sampled filtered signal to a summer; and summing the filtered full-rate signal and the up sampled filtered signal in the summer to provide a filtered signal.
-
Specification