Multi-level digital modulation & demodulation.
9.1. Introduction: So far, in looking at carrier modulated data transmission, we have concentrated mainly on binary signalling using simple forms of ASK, FSK and PSK. With a suitable pulse-shape, binary signalling can achieve a bandwidth efficiency of up to 2 bits/second per Hz using real unipolar pulses (base-band equivalent of ASK) or real bipolar pulses (base-band equivalent of PSK) at base-band. Since multiplying the base-band signal by a sinusoidal carrier doubles its bandwidth, the maximum band-width efficiency of binary ASK and binary PSK becomes one bit/second/Hz . With this band-width efficiency, a computer modem could achieve a maximum of about 3.1 kb/s over a 300-3400 kHz domestic telephone link. This is less than one tenth of what we know to be achievable. A similar calculation for the bandwidth-efficiency of binary FSK is a little more complicated, but if we take the frequency spacing used by MSK, i.e. 1/(2T) Hz, which is the minimum spacing compatible with the desirable highly property of 'orthogonality' between the 2 symbols, we may expect to achieve a maximum of slightly less than 2 bit/second per Hz. To increase the band-width efficiency over what can be achieved with binary signalling we must use multi-level modulation schemes where each symbol represents more than one bit. 9.2. Multi-level ASK and Gray coding: Perhaps the most obvious multi-level modulation technique, though rarely used, is 'M-ary ASK' which modulates the amplitude of a sinusoidal carrier with M different amplitudes. To encode N bits per symbol, rather than just one as with binary signalling, choose M=2N rather than M=2. For example, to encode 3 bits per symbol, we could have 8 rectangular symbols of heights 0, A, 2A, 3A, 4A, 5A, 6A and 7A volts. Consider what happens to the 'bit-error probability', PB , when we adopt this new signalling strategy. We can hope to keep PB...

...Digitalmodulation
differents kind and aplications form them.
DigitalModulation Techniques
The techniques used to modulate digital information so that it can be transmitted via microwave, satellite or down a cable pair are different to that of analogue transmission. The data transmitted via satellite or microwave is transmitted as an analogue signal. The...

...Communications Equipment) at point A.
3. The DCE at point A.
4. The transmission channel between points A and B.
5. The DCE at point B.
6. The DCE - DTE interface at point B.
7. The DTE at point B.
DIGITALMODULATION
Phase Shift Keying
-One of the simplest forms of digitalmodulation is binary or Bi-Phase Shift Keying (BPSK). One application where this is used is for deep space telemetry. The phase of a constant amplitude...

...(IJEIT) Volume 2, Issue 2, August 2012
Comparative Study of DigitalModulation Techniques in WIMAX
Umesh Sharma
Abstract: - The migration to 4G networks will bring a new level of expectation to wireless communications. As after digital wireless revolution made mobile phones available for everyone, the higher speeds and packet delivery of 4G networks will make high quality multimedia available everywhere. The key to achieving this...

...AMPLITUDE MODULATION AND DEMODULATION :
OBJECTIVE :
Study how to perform the amplitude modulation and demodulation and to calculate the modulation index for various modulating voltages.
Theory :
AMPLITUDE MODULATION :
Modulation is defined as the process by which some characteristics of a carrier signal is
varied in accordance with a modulating signal. The base band signal is referred to as...

...FSK MODULATION AND DEMODULATION PROGRAM USING MATLAB
LIST OF TABLES:
CHAPTER 1: INTRODUCTION.
1.1-INTRODUCTION TO WIRELESS MODEM.
1.2-INTRODUCTION TO FREQUENCY SHIFT KEYING
1.2.1-FSK MODULATOR
1.2.2-FSK DEMODULATION
CHAPTER 2: COMPONENT DESCRIPTION.
2.1-LIST OF COMPONENTS
2.2-DESCRIPTION OF FUNCTIONAL DIAGRAM
2.2.1 IC 555.
2.2.2 565 PLL.
CHAPTER 3: CIRCUIT DIAGRAM AND WORKING.
3.1-CIRCUIT DIAGRAM OF FSK MODULATOR USING...

...tutorial, QPSK, modulation, modulator, demodulator, demodulation
May 01, 2002
APPLICATION NOTE 686
QPSK modulation demystified
Abstract: Readers are presented with step-by-step derivations showing the operation of QPSK modulation and demodulation. The transition from analog communication to digital has advanced the use of QPSK. Euler's relation is used to assist analysis of multiplication of sine and...

...1.1 ABSTRACT:
2 .1 BLOCK DIAGRAM:
Fig 2.1 Block diagram for FSK modulation and de-modulation
2.2.1 PIN DIAGRAM- IC 565 :
Fig 2.2 Pin diagram for IC 565
2.2.2 PIN DIAGRAM -IC 555:
Fig 2.3 Pin diagram for IC 555
3.1 DESIGN CALCULATION:
3.1.1 FSK MODULATOR:
ON time TH=0.693RBC
OFF time TL=0.693(RA+RB)C
Total time T=TH+TL=0.693(RA+2RB)C
1
f1=...

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