How "Radio and Television" conveys information—Introduction to Communication Technology PPT Courseware 6

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How "Radio and Television" conveys information—Introduction to Communication Technology PPT Courseware 6

1. The principle of electromagnetic waves transmitting sound and image signals

Electromagnetic waves transmit sound and image signals just like pigeons transmit messages.

The signal is first carried on the electromagnetic wave, and then the electromagnetic wave carrying the signal is emitted, and when it reaches the receiving location, the signal is detected from the electromagnetic wave.

2. The emission process of electromagnetic waves

(1) High-frequency oscillation current is generated by a high-frequency oscillator

(2) Convert the sound and image signals to be transmitted into current signals (electrical signals)

(3) Input the high-frequency oscillation current generated by the oscillator and the signal current of sound and image into the modulator, so that the high-frequency oscillation current changes correspondingly with the transmitted sound and image signal, and then the high-frequency oscillation current is The current is sent to the transmitting antenna, and the emitted electromagnetic wave carries the sound and image signal to be transmitted. That is, the so-called "adding" the signal to be transmitted to the electromagnetic wave. The electromagnetic wave with the signal is emitted.

3. Radio reception process

(1) Use an antenna to receive electromagnetic waves.

(2) Use a tuner, which is the channel selection circuit in a radio or television, to select the required electrical signal.

(3) By letting the high-frequency oscillating current pass through the detector, the sound signal and image signal to be transmitted can be "detected" from the high-frequency oscillating current. By sending the sound signal and image signal to the speaker and the TV respectively, Hear sounds and see images.

practise

The transmission process of radio broadcasting is: the microphone of the radio station converts the announcer's ________ into ________, then uses a modulator to load the audio electrical signal onto __________ (carrier wave), and then transmits it out through the antenna; the reception of radio broadcasting The process is: the antenna of the radio receives various ________. By turning the knob of the radio tuner, the ________ signal can be selected from it. The electronic circuit in the radio then takes out the ________ signal, amplifies it and sends it Convert it to ________ in the speaker, and we can hear the broadcast.

During extracurricular activities, several students discussed the reception and transmission of radio broadcasts and television signals. They made the following statements. Which one do you think is correct?

A. Radio broadcasting is the mutual conversion between optical and electrical signals.

B. The reception or emission of television signals is the conversion between acoustic and electrical signals.

C. Both radio broadcasting and television are the conversion of light and electrical signals.

D. Whether it is radio broadcasting or television, there is conversion of sound and electrical signals.

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Update Time: 2024-11-23

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