1hz
=
1/ sec
The seventh note of the major scale
Derivative unit
1
kilohertz (kHz)
kilohertz (kHz)
10^3
hertz
1
000
hertz
1
MHz
MHz
10^6
hertz
1
000
000
hertz
1
gigahertz
ghz
10^9
hertz
1
000
000
000
hertz
1
peaceful
Terahertz
10^ 12
hertz
1
000
000
000
000
hertz
1
Paihe
phz
10^ 15
hertz
1
000
000
000
000
000
hertz
1
Ai He
ehz
10^ 18
hertz
1
000
000
000
000
000
000
hertz
Electricity (voltage or current) can be divided into DC and AC. In communication applications, alternating current is usually used for signal transmission. With the change of time, the amplitude of sinusoidal AC signal is positive and negative, and it propagates forward at a certain energy and speed (see figure 1).
Usually, we call the number of times the sine wave amplitude changes repeatedly within 1 second as the "frequency" of the signal, which is expressed by f; The time required for a signal waveform to change once is called "period", which is expressed by t and the unit is seconds. The distance that a wave travels in a period is called "wavelength", which is expressed by λ and the unit is meter.
F, t and λ have the following relationship:
f= 1/t
v=λ。 f
Where v is the propagation speed of electromagnetic wave, which is equal to 3x10.8m/s.
The unit of frequency is hz, abbreviated as Hz, and expressed by the symbol Hz. Hertz (h? Hertz) is a famous German physicist, 1887, who confirmed the existence of electromagnetic waves through experiments. In order to commemorate him, later generations set "Hertz" as the unit of frequency.
Commonly used frequency units are kilohertz (khz), megahertz (mhz) and gigahertz (ghz).
1khz= 10^3hz
1mhz= 10^6hz
1ghz= 10^9hz
1thz= 10^ 12hz
1phz= 10^ 15hz
There are sometimes many frequency components in the electric signal carrying information; Mark the position of all these components on the frequency axis, and express the size of each component in terms of power or voltage, which is the "spectrum" of the signal. The frequency range it occupies is called the frequency band range of the signal. For example, in telephone communication, the frequency range of voice signal is 300 ~ 3400Hz；; In FM broadcasting, the frequency range of sound is 40 Hz ~ 15 kHz, and the frequency range of TV broadcast signal is 0 ~ 4.2 MHz.