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The impulse can be modeled as a Dirac delta function for continuous-time systems, or as the discrete unit sample function for discrete-time systems. The Dirac delta represents the limiting case of a pulse made very short in time while maintaining its area or integral (thus giving an infinitely high peak).
A sample is a value of the signal at a point in time and/or space; this definition differs from the term's usage in statistics, which refers to a set of such values. [ A ] A sampler is a subsystem or operation that extracts samples from a continuous signal .
Linear interpolation is equivalent to a triangular impulse response; windowed sinc approximates a brick-wall filter (it approaches the desirable brick-wall filter as the number of points increases). The length of the impulse response of the filter in method 1 corresponds to the number of points used in interpolation in method 2.
where the h[•] sequence is the impulse response, and K is its length. x [•] represents the input sequence being downsampled. In a general purpose processor, after computing y [ n ], the easiest way to compute y [ n +1] is to advance the starting index in the x [•] array by M , and recompute the dot product.
The FIR convolution is a cross-correlation between the input signal and a time-reversed copy of the impulse response. Therefore, the matched filter's impulse response is "designed" by sampling the known pulse-shape and using those samples in reverse order as the coefficients of the filter. [1]
An example is for high-resolution audio in which the frequency response (magnitude and phase) for steady state signals (sum of sinusoids) is the primary filter requirement, while an unconstrained impulse response may cause unexpected degradation due to time spreading of transient signals.
Impulse response coefficients taken at intervals of form a subsequence, and there are such subsequences (called phases) multiplexed together. Each of L {\displaystyle L} phases of the impulse response is filtering the same sequential values of the x {\displaystyle x} data stream and producing one of L {\displaystyle L} sequential output values.
If a system initially rests at its equilibrium position, from where it is acted upon by a unit-impulse at the instance t=0, i.e., p(t) in the equation above is a Dirac delta function δ(t), () = | = =, then by solving the differential equation one can get a fundamental solution (known as a unit-impulse response function)