无线通信原理（Principles of wireless communication）.docVIP

无线通信原理（Principles of wireless communication） Basic principles of radio communication Roger A two-way radio communication system of Motorola pioneered by the military for more than fifty years ago during the Second World War, let the soldiers in action to radio calls to each other, when the mobile phone is called walkie talkie (Walkie - talkies). Two-way radio is common in the military, where military personnel use radios without telephone lines. Today radio has been widely used for security, public services and utilities, as well as for commercial and personal purposes. The main advantages of two-way radio are direct peer to peer, without any basic facilities, so long as the two sides are tuned to the same frequency, they can talk to each other. The principle of two-way radio communication A two-way radio transceiver is used for transmitting and receiving voice information. Each two-way radio transceiver consists of a transmitter and a receiver, a microphone and an amplifier, an antenna and a set of power supplies. Portable two-way wireless communications use batteries as power supplies, while car radios can use the power of the car. The user speaks to the microphone, and the voice signal is converted to an electronic signal. The signal is amplified by the transmitter as a radio signal, then transmitted to the antenna, and the radio signal is sent to the air by the antenna. The receiving antenna receives the radio signal and sends the signal to the receiver. The receiver changes the radio signal to the original speech, and then releases it from the loudspeaker of the walkie talkie, where the original message can be heard. Simple two-way radio system When more than two radios talk to each other, they must operate at the same frequency. In the single frequency simplex radio system, each user can transmit or receive information at any time. This is different from the telephone system. The telephone is a duplex system that can speak and listen at the same time. Therefor