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Electrical Communications Systems ECE.09.331 Spring 2009

Electrical Communications Systems ECE.09.331 Spring 2009. Lab 3: Pre-lab Instruction. Shreekanth Mandayam ECE Department Rowan University http://engineering.rowan.edu/~shreek/spring09/ecomms/. ECOMMS: Topics. Plan. FM Signal and Spectrum FM Detection Slope Detector FM Generation

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Electrical Communications Systems ECE.09.331 Spring 2009

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  1. Electrical Communications SystemsECE.09.331Spring 2009 Lab 3: Pre-lab Instruction Shreekanth Mandayam ECE Department Rowan University http://engineering.rowan.edu/~shreek/spring09/ecomms/

  2. ECOMMS: Topics

  3. Plan • FM Signal and Spectrum • FM Detection • Slope Detector • FM Generation • Voltage Controlled Oscillator (VCO) • Phase Locked Loop (PLL) • FM Detection • Lab Project 3

  4. J1(b) |S(f)| / (Ac/2) J2(b) J3(b) J0(b) 0fc-3fm fc-2fm fc-fm fc fc+fm fc+2fm fc+3fm f FM Signal & Spectrum Single-tone FM Signal Single-tone FM Spectrum

  5. FM Detection FM Signal, We need a frequency-voltage converter Slope Detector

  6. Frequency- voltage converter AM Detector LPF Envelope Detector |H(f)| vo(t) f fi(t) t Slope Detector

  7. FM Generation Voltage Controlled Oscillator f0=fc Control Voltage Instantaneous Frequency m(t)

  8. Signal Source Amplifier vi + Output A S vo vs - b Feedback Network Oscillators: Principle Barkhausen Criteria for oscillation: Ab = -1

  9. Oscillators Waveforms Schmitt Trigger Oscillator

  10. v10 Flip-Flop Changes State Switch Open, C charges Switch Closed, C discharges Vc1 t Vc2 Intersil 8038 Precision Waveform Generator/Voltage Controlled Oscillator

  11. fi -fvco Phase Detector LPF A fi vo Loop Filter fvco VCO Phase Locked Loop Hold (lock) Range, fH Capture Range, fC f fo

  12. Lab Project 3:Frequency Modulation and Detection

  13. Summary

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