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Radio Transmitter

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RADIO TRANSMITTER
Contents
• Transmitter Fundamentals • Transmitter Types • High-Level Amplitude Modulated (AM)
Transmitter
• Low-Level Frequency Modulated (FM)
Transmitter
• Single-Sideband (SSB) Transmitter • Carrier Generators
• Crystal Oscillators • Frequency Synthesizers
• Phase-Locked Loop Synthesizer
Transmitter Fundamentals
• A radio transmitter takes the information to be communicated and converts it into an electronic signal compatible with the communication medium.
• This process involves carrier generation, modulation, and power amplification.
• The signal is fed by wire, coaxial cable, or waveguide to an antenna that launches it into free space.
• Typical transmitter circuits include oscillators, amplifiers, frequency multipliers, and impedance matching networks.
• The transmitter is the electronic unit that accepts the information signal to be transmitted and converts it into an RF signal capable of being transmitted over long distances.
• Every transmitter has four basic requirements:
– It must generate a carrier signal of the correct frequency at a desired point in the spectrum.
– It must provide some form of modulation that causes the information signal to modify the carrier signal.
– It must provide sufficient power amplification to ensure that the signal level is high enough to carry over the desired distance.
– It must provide circuits that match the impedance of the power amplifier to that of the antenna for maximum transfer of power.
• The simplest transmitter is a single-transistor oscillator connected to an antenna.
• This form of transmitter can generate continuous wave (CW) transmissions.
• The oscillator generates a carrier and can be switched off and on by a telegraph key to produce the dots and dashes of the International Morse code.
• CW is rarely used today as the oscillator power…...

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