【Audio】 also known as audio, is the ear can hear the frequency. Usually refers to the frequency between 15 and 20000 Hz (Hz).
【Frequency】 refers to the language frequency within the audio range. In the general telephone path, it usually refers to the frequency between 300 and 3400 Hz.
[Radio frequency] radio transmitter through the antenna can be effectively transmitted to the space of the electromagnetic wave frequency, collectively referred to as radio frequency. If the frequency is too low, the effectiveness of the launch is very low, it is customary to refer to the radio frequency refers to 100 kHz (KHz) above the frequency.
【Video】 TV signal contains the frequency range from tens of hours to several MHz, the video is the frequency of collectively.
A sine wave or periodic pulse acting as a carrier, called a carrier (or carrier frequency), that changes the amplitude, frequency, or phase of the carrier as the signal wave changes.
The power used to express or carry information.
Channel A path that is divided by the nature of the message. Including possible channels that have not yet been implemented.
[Analog signal] in the time is continuous or for a parameter can take an unlimited value of the signal.
【Digital signal】 The so-called digital signal, is the signal is discrete, discontinuous. This is the signal can only be limited by a number of ladder or incremental changes and values. In other words, for a digital signal, it is only necessary to calculate the number of steps without considering the size of the signal within the ladder (most commonly binary).
[Transmitter output power] refers to the transmitter to the electromagnetic radiator (antenna) radio frequency power is called the transmitter output power.
[Spurious radiation of the transmitter] Measured on the load of the nominal output impedance, the spurious radiation power of any one of the discrete frequencies does not exceed 2.5 uW when the carrier carrier frequency is less than 25W. When the carrier frequency of the transmitter is greater than 25W, the spurious radiation power of any discrete frequency should be less than 70dB of the carrier frequency.
[Adjacent channel power] For the 160,450MHz band, the power in the 16KHz band on the adjacent channel should be 70dB lower than the carrier frequency. For the 900 MHz band, the power falling within the 32 KHz band of the adjacent second channel should be 65 dB lower than the carrier frequency.
[Average power] The average power that the transmitter feeds to the specified test load at a much longer time than the cycle corresponding to the lowest modulation frequency under specified conditions.
[Peak packet power] transmitter in the specified modulation conditions, at the peak of the modulation envelope in the high frequency of a cycle to the specified experimental load on the average power.
The rated output power of the single sideband transmitter is nominal with peak packet power.
[Sideband Suppression] In the generation of a single sideband signal, the suppression of the no sideband signal is called the sideband suppression. In terms of the number of decibels without the ratio of the sideband signal level to the useful sideband signal level.
In the specified modulation, the total power of the transmitter falls within the specified frequency of a specified frequency centered on some of the specified frequencies on either side of the nominal frequency.
Level is the amount of electricity (voltage, current or power) relative to the size of the commonly used units for the decibel (or niu). Normally, the value of a certain charge is specified as a standard value, and a value is expressed by a value other than the standard value. For example, take the standard power of 1 milliwatts to zero level, when the given power of 10 mW, the level value can be obtained as follows:
Level value = 10
Thus, 10 milliwatts have a 10 dB level. If the level value is negative, it means less than zero level, and this level can be used to represent the relative size between any two power levels.
[Audio response] When the input signal level is constant, the receiver output level varies with the audio frequency within the specified audio range, called the audio response. Expressed as the decibel number of the ratio of the highest level and the lowest level.
[Duplex notification] Both parties can simultaneously send and receive the notification method is called duplex notification mode.
To achieve duplex notification needs to meet the conditions are: 1, the receiver can receive at any time to report, 2, the sender should not affect the work of the receiver.
[Half-duplex notification] Also known as "quasi-duplex" notification, is a special way of single-sideband communication. Is the use of each other "hair" to the other side of the gap to send a signal, is a "limited duplex" approach. Such as the usual call is to use the "half-duplex" approach, the other is talking, the other can only listen. Such as anxious to answer, can only use the gap between the other side of the speech can be inserted.
It is usually called a walkie - talkie. Each phone for a group of frequencies, the frequency interval of 25KHz, the use of the need to configure one or several frequency points. Telephone output power range of 5W or less (generally divided into 0.5W below, 2W, 3W, 5W several levels). This type of telephone is generally limited to the use of the machine equipped with a small whip antenna, for the use of intercom, not allowed to set up high-altitude antenna for long-distance communication to control the role of distance and reduce mutual interference.
[Decibel] is the abbreviation of Bell, equal to 1/10 of the Bell, expressed in dB, is used to measure the amplifier or attenuation of the common units.
When the magnification or attenuation of the power is expressed: decibel =
The number of decibels is 20 when the voltage (or current) is increased or decreased
[Niobi] is a measure of the gain or attenuation of the unit. It is the natural logarithm of the voltage ratio or the current ratio. When the impedance at the two points of the circuit is equal, it is one-half the natural logarithm of the power ratio. 1 Nai Bei is equal to 8.686 dB.
[Interference] The effect of the unwanted energy generated by the transmission, radiation, induction, or combination thereof on the reception of the radiocommunication system causes the reception performance to be degraded or the signal is not received. This effect is called interference The Interference according to their sources can be divided into: industrial interference, electricity interference, the universe interference, human interference and so on.
[Interference source] In a radiocommunication system, it is determined that interference is generated by radiation, radiation or induction. That is, those messy waves that interfere with the radio reception signal.
[Dedicated communication network] Dedicated communication network refers to the organs, enterprises, railways, aviation, military, meteorological and other units of the business needs of the unit set up the communication network. The transmission facilities in the private network, such as bright lines, cables, cable or microwave trunk lines, shall be constructed or rented to the communication department in accordance with the provisions of the State.
Radio control Radio control is a mandatory administrative measure taken for the use of all or part of the radio transmitting equipment and other radioactive radio waves in a specific time, area, frequency range.
Radio is a radio station that must be installed as an integral part of a vehicle at the factory.
[International Radio Regulations] The International Radio Regulations are an international radio regulation that is an important international force for the United Nations specialized agencies - the International Telecommunication Union to regulate radio communications, to adjust the interrelationships of countries in radio management activities and to regulate their rights and obligations Regulations.
Radio station A radio station that broadcasts language and music programs. Including broadcast control center, launch pad and the corresponding ancillary facilities.
[Broadcast control center] in the broadcasting system, bear the radio program production and the program signal transmission to the launch station and other tasks of the place.
[Radio broadcasting station] In a broadcasting system, a radio program is used to broadcast a broadcast program.
A television station that broadcasts a television program, including a television center, a television launcher, and a corresponding accessory.
A television station that produces a television program and transmits a program signal to a place on the launch pad.
TV transmitter, television transmitter, transmitter antenna and a variety of ancillary facilities consisting of television transmission system.
【TV channel】 broadcast a set of television programs used by the specified channel. China's use of television programs per channel, the band range of 8 MHz.
A transmission system for the exchange of television signals between several television stations.
Information theory is a science that studies the general laws of information transmission and information processing systems.
The research object of information theory is generalized information transmission and information processing system, from telegraph, telephone, fax, television, radar, until all kinds of biological nerve perception system, can be summed into this or that random process or statistical mathematics Model to further study. Therefore, the scope of information theory and its application prospects are very broad.