BLK_CON

The BLK_CON function computes a "fast convolution" of a digital signal and an impulse-response sequence. It returns the filtered signal.

This routine is written in the IDL language. Its source code can be found in the file blk_con.pro in the lib subdirectory of the IDL distribution.

Calling Sequence

Result = BLK_CON( Filter, Signal )

Arguments

Filter

A P -element floating-point vector containing the impulse-response sequence of the digital filter.

Signal

An n -element floating-point vector containing the discrete signal samples.

Keywords

B_LENGTH

A scalar specifying the block length of the subdivided signal segments. If this parameter is not specified, a near-optimal value is chosen by the algorithm based upon the length P of the impulse-response sequence. If P is a value less than 11 or greater than 377, then B_LENGTH must be specified.

B_LENGTH must be greater than the filter length, P , and less than the number of signal samples.

Example

Create a filter of length P = 32:

filter = REPLICATE(1.0,32) ; Set all points to 1.0

filter(2*INDGEN(16)) = 0.5 ; Set even points to 0.5

Create a sampled signal with random noise:

signal = SIN((FINDGEN(1000)/35.0)^2.5)

noise = (RANDOMU(SEED,1000)-.5)/2.

signal = signal + noise

Convolve the filter and signal using block convolution:

result = BLK_CON(filter, signal)