Design And Develop A 88-108MHz 3.5W FM Transmitter
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Ramin Farmani - Ahmad Bahreyni Summer 2009 Design and Develop a 88-108MHz 3.5W (8Km) FM Transmitter
Transcript of Design And Develop A 88-108MHz 3.5W FM Transmitter
Ramin Farmani - Ahmad BahreyniSummer 2009
Design and Develop a 88-108MHz 3.5W (8Km)
FM Transmitter
Apr 13, 202388-108 MHz 3.5Watt FM Transmitter
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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
Apr 13, 202388-108 MHz 3.5Watt FM Transmitter
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Designing a Transmitter
Analog & Digital Complexity Extra Complexity in RF Electronic Define our Project Requests Governmental Rules in Countries
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FM & AM Modulation
FM & AM in Broadcasting AM a Brief Introduction FM a Brief Introduction
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CLASS C AMPLIFIER
Vce
Ic
Class A
Class AB
Class B
Class C
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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)
+V12V
1kTP1
1.0 kHz
-5/5V
1k
NPN
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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….
-4V DC
+V12V
1kTP2
1.0 kHz
-5/5V
1k
NPN
About 0.3V
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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.
1uF C1
1uH
-4V DC
+V12V
TP3
1.0 kHz
-5/5V
1k
NPN
Positive alternations filled in by tank circuit ring
Resonant (tank) circuit
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Designing Circuit
Audio Preamplifier
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Designing Circuit
FM Modulator and Oscillator
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