Demodulationdemodulation demodulation is digitaltoanalog signal conversion. Frequency division multiplexing, fdma amplitude modulation and demodulation. In part i you will learn how to design an amplitude modulator am and in part ii you will be able to demodulate an am signal. Modulation and demodulation principle borrow from radio telecommunication take a wide band signal few hz to khz modulate it with a single frequency the carrier signal which is the frequency associated to a given station emit the signal given the station frequency, a receiver follows a demodulation.
Practical approach of producing delta modulation and. Delta modulation its block diagram and applications. Modulation and demodulation pdf on the various aspects of modulation and demodulation. A typical f c for lowrate telephone line modems is 1800 hz approximate center of 300 3400 band, and for 1200 baud signaling 1200 pulses per. The goal of this experiment is to become familiar with fm modulation and demodulation.
Delta modulation is a scheme to permit the use of a simple quantizing strategy for constructing the encoded signals which are oversampled purposely, to increase the correlation between adjacent samples of the signal, as seen in differential pulse code modulation method. The purpose of this lab is for you to gain familiarity with the concepts of amplitude modulation and demodulation. To show the adaptive delta modulation adm voice coding scheme which is the best coding scheme procedure when compare to all other techniques. Theory shows that in order to transmit a wave effectively, the length of the. Delta modulation is process in which one bit per sample is assigned, unlike pcm.
But the term demodulation tends to be used more widely when referring to the process of extracting the modulation from the signal. Delta modulation quantizing noise analytical and computer. This chapter describes the essential principles behind modulation and demodulation, which we introduced briefly in chapter. Pwm converts an audio signal into a sequence of pulses having constant amplitude, but the width is proportional to amplitude of an audio signal. Most radio systems in the 20th century used frequency modulation fm or amplitude modulation am for radio broadcast a modulator is a device. There are many types of modulation so there are many types of demodulators. Frequency modulation fm is the encoding of information in a carrier wave by varying the instantaneous frequency of the wave. The number of signicant energy contained spectral lines, is limited, so we can use the fm nodulation, with. Delta modulation is a simplified form of dpcm technique, also viewed as 1bit dpcm scheme. Amplitude modulation is defined as the process in which the amplitude of the carrier wave ct is varied about a mean value, linearly with the baseband signal. If the pulse is lower in value, resulting in a negative value, a 0 is used.
Then, students will use labview to program an am demodulator and use. Human ear has a build in ability to become more or less sensitive to audible signals. Codes used for adaptive delta demodulation decoding process. For this purpose delta modulation, adaptive delta modulation, differential pulsecode modulation is used to compress the data. Then inner products dot products are 1 1 0 can interpret inner product as projection of vector 1 v1 onto vector 2 v2in other words, inner product of v1 and v2 tells us how much of vector 1 is there in the direction of vector 2. Ee4512 analog and digital communications chapter 6 the dsbsc am coherent receiver has a bandpass filter centered at f c and with a bandwidth of twice the bandwidth of st because of the lsb and usb. Delta modulation dm watch more videos at videotutorialsindex.
In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a modulating signal that typically contains information to be transmitted. To ensure accurate reproduction of an analog signal. There are different types of modulation and so are demodulators. The input signal is added to a triangular wave and the sum is fed into a signum function, whose output is the pd. The delta modulator comprises of a 1bit quantizer and a delay circuit along with two summer circuits. Adaptive delta modulation block diagram and applications. Modulation allows us to transmit multiple signals in the same medium i. The term and technology us used in both telecommunications and signal processing in analog frequency modulation, such as fm radio broadcasting of an audio signal representing voice or music, the instantaneous frequency. Adaptive delta modulation reasons to use adaptive delta modulation. The modulation and demodulation problems for efficient multicarrier communications are considered in this study. Understanding delta modulation and adaptive delta modulation. Since, the delta modulation transmits only one bit for one sample, therefore the signaling rate and transmission channel bandwidth is quite small for delta modulation compared to pcm. To improve the quality of reception to increase the range of communication need of demodulation the wireless signal consists of radio frequency high frequency carrier wave modulated by audio frequency low.
In addition to a variable bandpass filter, one auto notch and one manual notch filter can be utilized to eliminate interfering signals. The connections are given as per the block diagram. Modulation can be defined as the process of impressing information from a modulating signal onto another signal called the carrier. Practical approach of producing delta modulation and demodulation doi. A demodulator is an electronic circuit that is mainly used to recover the information content from the modulated carrier wave. Engineers working in the field of speech coding have been actively searching for methods to reduce the bandwidth consumed by quantized speech signals. The amplitude of the carrier remains constant phase modulation pm another form.
Demodulation is extracting the original informationbearing signal from a carrier wave. Request pdf digital phase modulation and demodulation digital phase modulation is a class of power and bandwidthefficient modulations widely used in. Demodulation channel decoding is the corresponding process at the receiver of converting the received waveform into a. In order to overcome the quantization errors due to slope overload and granular noise, the step size. Pdf practical approach of producing delta modulation and. Digital phase modulation and demodulation request pdf. Pdf simulation of adaptive delta modulation using matlab. This contains a limiter, a clocked sampler, and an integrator of the type in the delta modulation utilities module. T2 obtain and examine a delta demod utilities module. Using matlab mfile and simulink to implement fm modulation and demodulation. Delta sigma modulation and demodulation lab youtube. To study the characteristics of delta modulation and demodulation kit. To maintain compact spectrum and realise dense multicarrier transmission, a novel.
A new adaptive delta modulation system iowa state university. Students will explore the mathematical theory behind amplitude modulation and use the analog discovery 2 to visualize the effects of amplitude modulation in the time and frequency domains. Getting knowledge over different modulation and demodulation techniques. Digital communication delta modulation tutorialspoint.
Delta modulation and demodulation computer science essay. The delta modulation has certain advantages over pcm as under. In the modulation process, the properties of a highfrequency signal such as amplitude, phase, etc are changed according to the lowfrequency baseband signal. Pulse width modulation pwm is a modulation technique, which converts an analog signal into a digital signal for transmission. This lab introduces students to communications theory with amplitude modulation and demodulation.
Introduction frequency modulation is a form of modulation, which represents information as. A demodulator is an electronic circuit or computer program in a softwaredefined radio that is used to recover the information content from the modulated carrier wave. Study on adaptive delta modulation and demodulation. Quantizing noise in delta modulation systems falls into two categories, granular noise and slope overload noise. Pdf efficient modulation and demodulation methods for.
Terms like diode detector, synchronous detector and product detector are widely used. Demodulation is defined as extracting the original informationcarrying signal from a modulated carrier wave. The term detection is the older term dating back to the early days of radio. Vectors and modulation cse 466 interfacing 3 spose m and n are orthogonal unit vectors. As the sampling interval is reduced, the signal correlation will be higher. Following is the block diagram of a delta modulator. Adaptive delta modulation block diagram and applications in communication systems, the modulation methods are used to transmit signals over long distances. To study and perform pulse position 6 to study and perform pulse code modulation and demodulation. The resulting signal is called the modulated signal in general, it is a bandpass signal. Frequency modulation fm is a process in which the carrier frequency is varied by the amplitude of the modulating signal i. Aly elosery october 25, 2010 this lab is divided into two parts. Digital communication delta modulation the sampling rate of a signal should be higher than the nyquist rate, to achieve better sampling.
Frequency modulation fm frequency modulation is the process of varying the frequency of a carrier wave in proportion to the amplitude of a baseband signal. Dm is the simplest form of differential pulsecode modulation dpcm where the difference between successive samples are encoded into nbit data streams. Typical modulation system the reverse process is called demodulation. A staircase approximated waveform will be the output of the delta modulator with the stepsize as delta. If the received carrier phase is assumed to be constant, each of the seven reference values will have to be shifted only once at the beginning of the simulation. Apr8 principles of sigmadelta modulation for analogtodigital.
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