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 techniques used to transmit analogue signals are used to transmit digital signals. The problem is to convert the digital signals to a form that can be treated as an analogue signal that is then in the appropriate form to either be transmitted down a twisted cable pair or applied to the RF stage where is modulated to a frequency that can be transmitted via microwave or satellite.
The equipment that is used to convert digital signals into analogue format is a modem. The word modem is made up of the words “modulator” and “demodulator”.
A modem accepts a serial data stream and converts it into an analogue format that matches the transmission medium.
There are many different modulation techniques that can be utilised in a modem. These techniques are:
• Amplitude shift key modulation (ASK)
• Frequency shift key modulation (FSK)
• Binary-phase shift key modulation (BPSK)
•...

...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 carrier signal moves between zero and 180 degrees. On an I and Q diagram, the I state has two different values. There are two possible locations in the state diagram, so a binary one or zero can be sent. The symbol rate is one bit per symbol. A more common type of phase modulation is Quadrature Phase Shift Keying (QPSK). It is used extensively in applications including CDMA (Code Division Multiple Access) cellular service, wireless local loop, Iridium (a voice/data satellite system) and DVB-S (Digital Video Broadcasting — Satellite).
Frequency Shift Keying
Frequency modulation and phase modulation are closely related. A static frequency shift of +1 Hz means that the phase is constantly advancing at the rate of 360 degrees per second (2 π rad/sec), relative to the phase of the unshifted signal. FSK (Frequency Shift Keying) is used in many applications including cordless and paging systems. Some of the cordless systems include DECT (Digital Enhanced Cordless...

...
Topic: DigitalModulation Techniques
Course code: ELE102
Course title: Electrical science-II
Submitted to: Submitted by:
Subrahmanyam Tanala Sir vishwajeet kumar
Sec:K1901
Roll:B57
Contents
INTRODUCTION
• 1 Aim
• 2 Analog modulation methods
• 3 Digitalmodulation methods
o 3.1 Fundamentaldigitalmodulation methods
o 3.2 Modulator and detector principles of operation
o 3.3 List of common digitalmodulation techniques
• 4 Digital baseband modulation or line coding
• 5 Pulse modulation methods
• 6 Miscellaneous modulation techniques
• 7 References
INTRODUCTION
In electronics, modulation is the process of varying one or more properties of a high frequency periodic waveform, called the carrier signal, with respect to a modulating signal. This is done in a similar fashion as a musician may modulate a tone (a periodic waveform) from a musical instrument by varying its volume, timing and pitch. The three key parameters of a periodic waveform are its amplitude ("volume"), its phase ("timing") and its frequency ("pitch"), all of which can be modified in accordance with a low frequency signal to obtain the modulated...

...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 higher level of service delivery is a new air interface. Orthogonal Frequency Division Multiplexing (OFDM) is an alternative wireless modulation technology to CDMA. OFDM is a digitalmodulation and multiplexing technique. In this paper, we have discussed various digitalmodulation techniques such as BPSK (2bits), QPSK (4 bits), QAM, 16 QAM and 64 QAM. We have designed simulation environment in MATLAB with various configurations of OFDM technique. The main objective of our work is to measure Bit Error Rate with different modulation schemes and come to the best configuration to achieve better utilization of bandwidth. We have studied existing configurations with analog and digitalmodulation techniques and compared the results. The driving force behind the need to satisfy this requirement is the explosion in mobile telephone, Internet and multimedia services coupled with a limited radio spectrum. Key...

...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 the modulating signal and the output of the modulation process is called as the modulation signal.
Amplitude modulation is defined as the process in which is the amplitude of the carrier wave
is varied about a means values linearly with the base band signal. The envelope of the modulating wave has the same shape as the base band signal provided the following two requirements are satisfied.
1. The carrier frequency fc must be much greater then the highest frequency components fm of the message signal m (t) i.e. fc >> fm
2. The modulation index must be less than unity. if the modulation index is greater than unity, the carrier wave becomes over modulated.
3. Modulation index = (A-B)/(A+B). where A and B as shown in the figure below.
Figure 1: Designing modulation index
Fig2: Amplitude modulation model graph
Design Procedure :...

...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 IC555.
3.2-CIRCUIT DIAGRAM OF FSK DEMODULATOR USING PLL 555
CHAPTER 4: OPERATION OF FSK.
4.1-OPERATION OF FSK MODULATOR USING IC555.
4.2-OPERATION OF FSK DEMODUALTOR USING PLL 565.
CHAPTER 5: PROGRAMING USING MATLAB.
5.1-FSK MODULATION USING MATLAB.
5.2-FSK DEMODULATOR USING MATLAB.
CHAPTER 6: OUTPUT WAVEFORMS.
6.1-OUTPUT OF FSK MODULATOR.
6.2-OUTPUT OF FSK DEMODULATOR .
CHAPTER 7: CONCLUSION.
7.1-CONCLUSION.
7.2-REFERENCES.
List of Figures
Fig a: Pin diagram of IC 555
Fig b: Pin diagram of NE 565
Fig c: FSK Modulator using IC 555
Fig d: Fsk Demodulator using NE 565
Fig e: Fsk Output model
Fig f: Output waveform of FSK Modulator.
Fig g: Output waveform of FSK Demodulator.
CHAPTER -1
INTRODUCTION
1.1: INTRODUCTION TO WIRELESS MODEM:
A wireless modem is a type of modem which connects to a wireless network instead of a telephone system. When a mobile...

...Maxim > App Notes > Basestations/wireless infrastructure
Wireless and RF
Keywords: 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 cosine signals. A SPICE simulation is used to illustrate QPSK modulation of a 1MHz sine wave. A phasor diagram shows the impact of poor synchronization with the local oscillator. Digital processing is used to remove phase and frequency errors. Since the early days of electronics, as advances in technology were taking place, the boundaries of both local and global communication began eroding, resulting in a world that is smaller and hence more easily accessible for the sharing of knowledge and information. The pioneering work by Bell and Marconi formed the cornerstone of the information age that exists today and paved the way for the future of telecommunications. Traditionally, local communication was done over wires, as this presented a cost-effective way of ensuring a reliable transfer of information. However, for long-distance communications, transmission of...