Analytic Signal (DSP Blockset)

Compute the analytic signal of a discrete-time input.

Library

Signal Operations, in General DSP

Description

The Analytic Signal block computes the complex analytic signal corresponding to each channel of the real input. The real part of the output is a replica of the real input; the imaginary part is the Hilbert transform of the input.

where H{·} denotes the Hilbert transform. In the frequency domain, the analytic signal retains the positive frequency content of the original signal while zeroing-out negative frequencies and doubling the DC component.

The block computes the Hilbert transform using an equiripple FIR filter designed using the Remez exchange algorithm. The linear phase filter imposes a delay of one half the Filter order on the input samples.

You can choose frame-based or sample-based operation by selecting (or deselecting, respectively) the Frame-based inputs check box. In both sample-based and frame-based operation, the output is the same size as the input.

Sample-Based Operation

When the Frame-based inputs check box is not selected (default), the block assumes that the input is a 1-by-N sample vector or M-by-N sample matrix. Each of the N vector elements (or M*N matrix elements) is treated as an independent channel, and the block computes the analytic signal of each of the channel over time.

Frame-Based Operation

When the Frame-based inputs check box is selected, the block assumes that the input is an M-by-N frame matrix. Each of the N frames in the matrix contains M sequential time samples from an independent signal. The illustration below shows a 6-by-4 frame matrix:

The Number of channels parameter specifies the number of independent channels (columns), N, in the matrix. The block computes the analytic signal of each channel independently.

Frame-based operation provides substantial increases in throughput rates, at the expense of greater model latency.

Dialog Box

Filter order: The length of the FIR filter used to compute the Hilbert transform.
Frame-based inputs: Selects frame-based operation.
Number of channels: For frame based operation, the number of columns (frames) in the input matrix.