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FM GENERATION

FM GENERATION. Direct Method: when the frequency of carrier is modulated by information signal Indirect Method: when the phase of carrier is modulated by information signal. Generation of FM waves. Varactor diode modulator( Direct method) Reactance modulator( Direct method)

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FM GENERATION

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  1. FM GENERATION Direct Method: when the frequency of carrier is modulated by information signal Indirect Method: when the phase of carrier is modulated by information signal

  2. Generation of FM waves • Varactor diode modulator( Direct method) • Reactance modulator( Direct method) • Crosby FM direct transmitter • Armstrong method (Indirect method)

  3. - more capacitance. - less capacitance.

  4. Varactor Diode FM modulator

  5. CIRCUIT DIAGRAM OF VARACTOR DIODE MODULATOR

  6. FET REACTANCE MODULATOR .

  7. Modulating signal Career Frequency modulation Phase modulation

  8. INDIRECT FM GENERATION Integrator

  9. + =

  10. FREQUENCY UP-CONVERSION • With FM and PM modulators, the carrier at the output is generally somewhat lower than the desired frequency of transmission. • There are two basic methods of performing frequency up conversion. • Heterodyning process • Frequency multiplication

  11. HETERODYNE METHOD OF FREQUENCY UP-CONVERSION

  12. MULTIPLICATION METHOD OF UP-CONVERSION

  13. BLOCK DIGRAM OF CROSBY DIRECT FM TRANSMITTER

  14. Block Diagram of FM Receiver

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