Emphasis (telecommunications)
Encyclopedia
In FM transmission
, emphasis is the intentional alteration of the amplitude-vs.-frequency
characteristics of the signal to reduce adverse effects of noise
in a communication system
.
The high-frequency signal components are emphasized to produce a more equal modulation index
for the transmitted frequency spectrum, and therefore a better signal-to-noise ratio
for the entire frequency range.
The whole system of preemphasis
and deemphasis
is called emphasis
.
The frequency curve is decided by special time constant
s. The cutoff frequency
can be calculated from that.
Emphasis is commonly used in audio digital recording, record cutting and in FM radio transmission.
Transmission (telecommunications)
Transmission, in telecommunications, is the process of sending, propagating and receiving an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium, either wired, optical fiber or wireless...
, emphasis is the intentional alteration of the amplitude-vs.-frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
characteristics of the signal to reduce adverse effects of noise
Noise
In common use, the word noise means any unwanted sound. In both analog and digital electronics, noise is random unwanted perturbation to a wanted signal; it is called noise as a generalisation of the acoustic noise heard when listening to a weak radio transmission with significant electrical noise...
in a communication system
System
System is a set of interacting or interdependent components forming an integrated whole....
.
The high-frequency signal components are emphasized to produce a more equal modulation index
Modulation index
The modulation index of a modulation scheme describes by how much the modulated variable of the carrier signal varies around its unmodulated level. It is defined differently in each modulation scheme. See:*Amplitude modulation index...
for the transmitted frequency spectrum, and therefore a better signal-to-noise ratio
Signal-to-noise ratio
Signal-to-noise ratio is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. It is defined as the ratio of signal power to the noise power. A ratio higher than 1:1 indicates more signal than noise...
for the entire frequency range.
The whole system of preemphasis
Preemphasis
In processing electronic audio signals, pre-emphasis refers to a system process designed to increase the magnitude of some frequencies with respect to the magnitude of other frequencies in order to improve the overall signal-to-noise ratio by minimizing the adverse effects of such phenomena as...
and deemphasis
Deemphasis
In telecommunication, de-emphasis is the complement of pre-emphasis, in the antinoise system called emphasis. Emphasis is a system process designed to decrease, , the magnitude of some frequencies with respect to the magnitude of other frequencies in order to improve the overall signal-to-noise...
is called emphasis
Emphasis
Emphasis or emphatic may refer to:* Emphasis , intentional alteration of the amplitude-vs.-frequency characteristics of the signal to reduce adverse effects of noise...
.
The frequency curve is decided by special time constant
Time constant
In physics and engineering, the time constant, usually denoted by the Greek letter \tau , is the risetime characterizing the response to a time-varying input of a first-order, linear time-invariant system.Concretely, a first-order LTI system is a system that can be modeled by a single first order...
s. The cutoff frequency
Cutoff frequency
In physics and electrical engineering, a cutoff frequency, corner frequency, or break frequency is a boundary in a system's frequency response at which energy flowing through the system begins to be reduced rather than passing through.Typically in electronic systems such as filters and...
can be calculated from that.
Emphasis is commonly used in audio digital recording, record cutting and in FM radio transmission.