Definition 1 (chivalrous): signal is the expression or transmission carrier of information.
The message is the specific content of the signal.
Definition 2 (generalized): A signal is a physical quantity that varies with some parameters.
Representation of signals
(1) Mathematical expression-function
(2) Waveform diagram
Signal classification
1. Deterministic signal and random signal
Determine the signal: the signal has a certain value at every point in the definition domain.
Random signal: a signal that does not meet the definition of definite signal.
2. Continuous time signals and discrete time signals
Continuous-time signal: The signal domain is a continuous interval, usually x(t), t? r .
The domain of a signal is a continuous interval.
Discrete-time signal: The definition domain of the signal is some discrete points, which are usually expressed by x[k], k? Me.
The domain of the signal is some discrete points.
The relationship between the two
Analog signal: Time signal with continuous amplitude.
Digital signal: Time signal with discrete amplitude.
3. Periodic signals and aperiodic signals
4. Energy signal and power signal
Energy signal: normalized energy is non-zero finite value, and normalized power is zero.
Power signal: the normalized energy is infinite, and the normalized power is non-zero and finite.
Definitions of normalized energy w and normalized power p;
Note: A signal can be neither an energy signal nor a power signal, but it cannot be both an energy signal and a power signal.
Concept and classification of signals
The concept of 1. 1 signal
Signal is the medium of information transmission, and signal is the physical quantity representing information. For example, electrical signals can express different information through changes in amplitude, frequency and phase. This kind of electric signal can be divided into analog signal and digital signal.
Classification of 1.2 signal
There are many ways to classify signals. Signals can be divided into deterministic signals and nondeterministic signals (also called random signals), continuous signals and discrete signals (namely analog signals and digital signals), energy signals and power signals, time-domain signals and frequency-domain signals, time-limited signals and frequency-limited signals, real signals and complex signals. According to the mathematical relationship, the characteristics of the value, processing and analysis, whether the value is a real number.
Digital signal and analog signal:
Analog signal: analog signal refers to the signal waveform that changes through the change of analog information. Its main feature is that its amplitude is continuous and it can take an infinite number of values. But it can be continuous or discontinuous in time.