DSP Blockset

Time and Frequency Terminology

A number of different terms are used to describe the characteristics of discrete-time signals found in Simulink models. These terms, which are listed in the table below, are frequently used in Chapter 5, "DSP Block Reference," to describe the way that various blocks operate on sample-based and frame-based signals.

Term	Symbol	Units	Notes
Sample period	Ts Tsi Tso,	Seconds	The time interval between consecutive samples in a sequence, as the input to a block (Tsi) or the output from a block (Tso).
Frame period	Tf Tfi Tfo	Seconds	The time interval between consecutive frames in a sequence, as the input to a block (Tfi) or the output from a block (Tfo).
Signal period	T	Seconds	The time elapsed during a single repetition of a periodic signal.
Sample rate, or Sample frequency	Fs	Hz (samples per second)	The number of samples per unit time, Fs = 1/Ts.
Frequency	f	Hz (cycles per second)	The number of repetitions per unit time of a periodic signal or signal component, f = 1/T.
Nyquist rate		Hz (cycles per second)	The minimum sample rate that avoids aliasing, usually twice the highest frequency in the signal being sampled.
Nyquist frequency	fnyq	Hz (cycles per second)	Half the Nyquist rate.
Normalized frequency	fn	Two cycles per sample	Frequency (linear) of a periodic signal normalized to half the sample rate, fn = / = 2f/Fs.
Angular frequency		Radians per second	Frequency of a periodic signal in angular units,  = 2f.
Digital (normalized angular) frequency		Radians per sample	Frequency (angular) of a periodic signal normalized to the sample rate,  = /Fs = fn.

Note    In the block dialog boxes, the term sample time is used to refer to the sample period, Ts. An example is the Sample time parameter in the Signal From Workspace block, which specifies the imported signal's sample period.

Discrete-Time Signals

Discrete-Time Signals in Simulink