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Amplitude Modulation Slides by (2003/04): Eryk Schiller, Daniel Starnowski Modulation & Detection Zdzisław Papir.

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Presentation on theme: "Amplitude Modulation Slides by (2003/04): Eryk Schiller, Daniel Starnowski Modulation & Detection Zdzisław Papir."— Presentation transcript:

1 Amplitude Modulation Slides by (2003/04): Eryk Schiller, Daniel Starnowski Modulation & Detection Zdzisław Papir

2 Amplitude Modulation DSBDouble Sideband Modulacja dwuwstęgowa AMAmplitude Modulation Modulacja amplitudy SSBSingle Sideband Modulacja jednowstęgowa VSBVestigal Sideband Modulacja z częściowo stłumiona wstęgą boczną Modulation & Detection Zdzisław Papir

3 DSB-SC Modulation Carrier: A 0 cos 0 t k – modulator constant Modulation & Detection Zdzisław Papir

4 DSB-SC Modulator x k x(t)x(t) Modulation & Detection Zdzisław Papir

5 DSB-SC Modulation x(t)x(t) -x(t)-x(t) t Modulation & Detection Zdzisław Papir

6 DSB-SC Modulation X( ) DSB ( ) g 0 - g g g W DSB = 2 g = 2 Modulation & Detection Zdzisław Papir

7 DSB-SC Detection Two possible detection techniques: Envelope detection (Detekcja obwiedni) Coherent (synchronous) detection Modulation & Detection Zdzisław Papir

8 Envelope DSB-SC Detection x(t)x(t)e(t)e(t) ! t Modulation & Detection Zdzisław Papir

9 Coherent DSB-SC Detection x cos 0 t Predetection Filter Lowpass Filter ~x(t) Modulation & Detection Zdzisław Papir

10 X( ) ½X( ) DSB ( ) 0 - g g 2 0 g - g g Coherent DSB-SC Detection Modulation & Detection Zdzisław Papir

11 Transmitter: cos 0 t Receiver: cos[( 0 + )t + ] In most cases: = 0 and variable in time Receiver: cos( 0 t + ) Coherent DSB-SC Detection Errors Modulation & Detection Zdzisław Papir

12 Coherent detection: [ x(t) cos( 0 t)]cos( 0 t + ) Detected signal: x(t) cos( ) Synchronous operation of both transmitter and receiver is necessary. Coherent DSB-SC Detection Phase Errors Modulation & Detection Zdzisław Papir

13 AM Modulation Modulation & Detection Zdzisław Papir

14 Single tone modulation: x(t) = acos m t AM =A 0 (1 + ka cos m t) cos 0 t ka = m – modulation index AM =A 0 (1 + m cos m t) cos 0 t AM Modulation Modulation & Detection Zdzisław Papir

15 A 0 (1+m) A 0 (1-m) t mA 0 AM Modulation Modulation & Detection Zdzisław Papir

16 0 - m 0 + m 0 AM Modulation Modulation & Detection Zdzisław Papir

17 AM Phasor Diagram 0 A0A0 m m Modulation & Detection Zdzisław Papir

18 P S – sidelobe power P T – total power AM Modulation Modulation & Detection Zdzisław Papir

19 X( ) ~X( ) SSB ( ) 0 - g g 2 0 g - g g Modulation & Detection Zdzisław Papir SSB-SC Modulation

20 ? X( ) SSB ( ) SSB-SC Modulation quadrature (Hilberts) filter Modulation & Detection Zdzisław Papir

21 x x + x(t)x(t) cos 0 t sin 0 t SSB-SC+ (t) - + SSB-SC Modulation Modulation & Detection Zdzisław Papir

22 Quadrature (Hilberts) Filter A( ) ( ) 1 Modulation & Detection Zdzisław Papir

23 Analytic Signal Modulation & Detection Zdzisław Papir

24 SSB-SC Modulation Modulation & Detection Zdzisław Papir

25 Coherent SSB-SC Detection x cos 0 t Predetection Filter Lowpass Filter ~x(t) Modulation & Detection Zdzisław Papir

26 Envelope SSB-SC Detection Modulation & Detection Zdzisław Papir

27 Envelope SSB-SC Detection Re Im e H Modulation & Detection Zdzisław Papir

28 x Envelope SSB-SC Detection Modulation & Detection Zdzisław Papir H

29 Nyquist Filter VSB-SC Concept H( ) Nyquist filter SSB-SC VSB-SC Vestigal SideBand Modulation & Detection Zdzisław Papir

30 VSB-SC Modulation DSB VSB Nyquist filter Modulation & Detection Zdzisław Papir

31 VSB-SC Modulation Lowpass I & Q representation of a bandpass VSB-SC signal Modulation & Detection Zdzisław Papir

32 Coherent VSB-SC Detection Requirement for a coherent VSB-S.C. detection Modulation & Detection Zdzisław Papir

33 VSB-SC Modulation Modulation & Detection Zdzisław Papir

34 VSB-SC Modulation x x + x(t)x(t) cos 0 t sin 0 t - + Modulation & Detection Zdzisław Papir

35 VSB-SC Modulation Modulation & Detection Zdzisław Papir

36 H( ) VSB-SC Modulation Modulation & Detection Zdzisław Papir

37 VSB-SC Modulation Modulation & Detection Zdzisław Papir Nyquist filter, 50%

38 componet enabling vestigal sideband filtering component enabling coherent detection VSB-SC Modulation Modulation & Detection Zdzisław Papir

39 Amplitude Modulation - different schemes DSB AM SSB VSB Modulation & Detection Zdzisław Papir


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