How "Radio and Television" conveys information—Introduction to Communication Technology PPT Courseware 3

Description

How "Radio and Television" conveys information—Introduction to Communication Technology PPT Courseware 3

Preview before class

1. What are RF signals and video signals?

2. What are AM and FM?

Teaching objectives

Common sense understanding of radio and television transmission and reception.

Review questions:

①How are electromagnetic waves generated? How can you indirectly observe its existence through experiments? (Electromagnetic waves are generated by oscillating currents; when you turn on a fluorescent lamp, you will hear noise from a nearby radio. This noise is generated when the electromagnetic waves emitted are received by the radio when the circuit is turned on and off.)

②What are the frequency and wavelength of electromagnetic waves? What is the propagation speed of electromagnetic waves in vacuum? What is the relationship between wave speed, frequency and wavelength? (The frequency of the electromagnetic wave is equal to the frequency of the oscillating current; the distance the electromagnetic wave propagates forward each time the current oscillates represents the wavelength of the electromagnetic wave; the propagation speed of electromagnetic waves in vacuum is 3 × 108 meters/second; wave speed = wavelength × frequency.)

①The oscillator generates high-frequency oscillating current (similar to a homing pigeon that can fly far away);

② Use a microphone to convert the sound signal into a changing current (similar to a letter to be sent);

③Use a modulator to superimpose the two currents to obtain a high-frequency modulated electrical signal (similar to tying a letter to a carrier pigeon);

④ The high-frequency modulated electrical signal is sent to the antenna, and the antenna emits electromagnetic waves (similar to the release of homing pigeons).

Writing on the blackboard: High-frequency oscillating current → Sound signal current → High-frequency modulated electrical signal → Emitting radio waves

Classroom test:

(1) We call the current converted from sound _____, and the current converted from images _____.

(2) Letting the amplitude of the radio frequency current change with the audio current is called _____; the sound of TV programs uses audio signals to control the radio frequency signal, and letting the frequency of the radio frequency current change with the audio current is called _____.

(3) By rotating the tuning knob of the radio, you can select the signal of a specific frequency of a radio station. This process is called _____.

(4) Antennas play an important role and are used for _____ and _____.

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Update Time: 2024-11-07

This template belongs to Physics courseware Beijing Normal University Ninth Grade Physics Volume 2 industry PPT template

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