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Design And Develop A 88-108MHz  3.5W FM Transmitter
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Design And Develop A 88-108MHz 3.5W FM Transmitter

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  • 1. Design and Develop a 88-108MHz 3.5W (8Km) FM Transmitter
    Ramin Farmani - Ahmad Bahreyni
    Summer 2009
  • 2. Preface
    Designing a Transmitter
    FM & AM a brief introduction
    Class C Power Amplifier a brief introduction
    Designing Circuit
    Schematic and PCB
    Dipole and Yagi Antenna
    Tuning
    Sep-09
    88-108 MHz 3.5Watt FM Transmitter
    2
  • 3. Designing a Transmitter
    Analog & Digital Complexity
    Extra Complexity in RF Electronic
    Define our Project Requests
    Governmental Rules in Countries
    Sep-09
    88-108 MHz 3.5Watt FM Transmitter
    3
  • 4. FM & AM Modulation
    FM & AM in Broadcasting
    AM a Brief Introduction
    FM a Brief Introduction
    Sep-09
    88-108 MHz 3.5Watt FM Transmitter
    4
  • 5. Class C Amplifier
    Sep-09
    88-108 MHz 3.5Watt FM Transmitter
    5
    Ic
    Class A
    Class AB
    Class B
    Vce
    Class C
  • 6. Class B Amplifier Review
    The Class B amplifier is biased at cutoff; in other words there is no bias.
    The amplifier relies on the input signal to bias the transistor. The first 0.7 volts of the signal in is lost because the transistor does not turn on until the base voltage reaches 0.7V.
    Amplifier is very efficient but provides ‘crossover distortion’.
    Amplifier is used to amplify power in situations where waveform is not important (power supplies)
    Sep-09
    88-108 MHz 3.5Watt FM Transmitter
    6
  • 7. Class C Biasing
    The Class C amplifier has a negative voltage at the base, and zero volts at the emitter. The Base-Emitter junction is reverse biased. The transistor will turn on at a signal voltage of 4.7V. The transistor will only conduct a small pulse through to the collector output.
    Amplifier is very efficient but has very little usefulness…. Unless….
    Sep-09
    88-108 MHz 3.5Watt FM Transmitter
    7
    About 0.3V
  • 8. Class C Application
    Collector resonant circuit responds to an impulse by ‘ringing’ at its resonant frequency. This is like pushing someone on a swing. A sharp short push each trip allows the swing to oscillate back and forth at its resonant frequency. Collector impulses occur by design at the resonant frequency of the tank circuit. Resonant circuit continues to ring and restores the sine wave at the output Class C Amplifier is used in radio/RF applications and is also called a ‘tuned’ amplifier.
    Sep-09
    88-108 MHz 3.5Watt FM Transmitter
    8
    Positive alternations filled in by
    tank circuit ring
    Resonant (tank) circuit
  • 9. Designing Circuit
    Audio Preamplifier
    Sep-09
    88-108 MHz 3.5Watt FM Transmitter
    9
  • 10. Designing Circuit
    FM Modulator and Oscillator
    Sep-09
    88-108 MHz 3.5Watt FM Transmitter
    10
  • 11. Sep-09
    88-108 MHz 3.5Watt FM Transmitter
    11