Time Domain: Classification Flashcards
Part 1A of the Signals and Systems unit, describing fundamental classifications of signals.
What is a continuous time (CT) signal?
A signal that has values for all points in time in some interval. It is denoted as x(t), where t = time
What is a discrete time (DT) signal?
A discrete time signal has values for only discrete points in time. Effectively, it is a sequence of samples. It is denoted as x[n], where n Is an integer defined over some time interval.
When is a signal considered analogue?
A signal (CT or DT) is considered analogue if the values that the signal can have vary continuously.
When is a signal considered digital?
A signal (CT or DT) is considered digital if it can only have a finite set of possible values.
These signals are considered continuous time - continuous variable signals.
Analogue signals
These signals are considered to be discrete time - discrete variable signals.
Digital signals
When is a continuous time signal considered to be periodic?
A CT signal, x(t) is considered to be periodic with period T if:
x[t] = x(t+T), for all t
where T is a positive real constant
What is the fundamental period?
The smallest value of T that satisfies periodicity
What is the fundamental frequency of a periodic signal?
f = 1/T
What is the angular frequency of a periodic signal (CT and DT)?
ω = 2π/T, for a CT signal
ω = 2π/N, for a DT signal
When do we consider a discrete-time signal to be periodic?
A discrete-time signal is said to be periodic with period N if:
x[n] = x[n+N], for all n
where N is a positive integer constant
What are the 3 ways of representing power?
Instantaneous power, average power, total average power
How do we find the instantaneous power of a signal?
The magnitude of the signal squared at time t
What is an energy signal?
For the energy to be finite the amplitude of the signal should tend to zero as t tends to infinity, signals for which this is true are called energy signals.
What is a power signal?
A signal in which the function e.g. x(t) does not tend to 0 as t tends to infinity. This signal has infinite energy so we use power to quantify the signal instead.
