Pdf modulation is an integral part of every modern communication systems and provides a. Textual information is transformed into binary digits by use of a coder. Modulation techniques lmodulation can be done by varying the l amplitude l phase, or l frequency of a high frequency carrier in accordance with the amplitude of the message signal. We reiterate and elaborate on those reasons in section 14. We consider binary modulation schemes and multilevel modulation schemes here. A tutorial on the most common digital modulation techniques used in both wireless and wired communications and how they compare to one another in spectral efficiency with relevant examples. In the past 20 years or so, research and development in digital modulation techniques have been very active and have yielded many promising results.
This site is like a library, use search box in the widget to get ebook that you want. Baseband transmission sends the information signal as it is without modulation without frequency shifting while passband transmission shifts the signal to be. Digital modulation techniques fuqin xiong pdf from traditional techniques such as fsk, bpsk, qpsk and qam to in its comprehensive overview of digital modulation applications, it seeks to offer a. What links here related changes upload file special pages permanent. Passband signals were originally baseband, but were modulated, or frequencyshifted or upconverted for some purpose, usually to make them fit in a passband channel. Request pdf digital modulationbaseband techniques digital modulation is the process which transforms an input bit stream into a digitally encoded. The sampling rate, or number of samples per second, is. The ber performance improvement for qpsk modulation when using loglikelihood ratio llr instead of harddecision demodulation in a convolutionally coded communication link.
Modulation technique pdf we begin our discussion of digital modulation by starting with the three basic types of digital modulation techniques. We discuss discrete changes in the characteristics of the carrier digital modulation in 14. In order to minimize the bit error probability, we use a technique known as. In the usual development of data modulation techniques as presented in most communications texts, the. Techniques baseband modulation using rectangular pulses and binary pulse amplitude modulation pages 7688. Amplitude modulation early radio ee 442 spring semester. Click download or read online button to get rf and baseband techniques for software defined radio book now. These are analog modulation formats amplitude, phase, frequency or quadrature modulation with baseband binary linecode messages having rectangular bit symbol pulses. Bandpass modulation and demodulation techniques communication systems, dept. Pulse code modulation an overview sciencedirect topics. In electronics and telecommunications, modulation is the process of varying one or more. Analytical equivalent and baseband equivalent the bandpass signal can be decomposed into a lowpass modulation function multiplied by a complex exponential carrier by using eulers formula and defining a new baseband equivalent modulation function, xbbt. Ee4512 analog and digital communications chapter 3 chapter 3 digital baseband modulation techniques goals in communication system design pages 7576.
Optical wireless communication systems employ imdd. So now lets discuss different types of pulse modulation techniques in detailpulse modulation can be categorized broadly into two types. Baseband modulation and demodulation techniques are fundamental to communication systems. One way to reduce the transmission bandwidth is to reduce the message bandwidth. In pcm systems, a waveform codec takes samples of an analogspeech waveform and encodes them as modulated pulses, represented by logic 1 high and logic 0 low. Digital modulation techniques by fuqin xiong, available at book depository with free delivery worldwide. In continuous wave modulation amplitude modulation, frequency modulation, phase modulation the carrier wave used is continuous in nature, while in case of pulse modulation, the carrier wave is in the form of pulses.
The amplitude modulation am modulation index can be defined as the ratio of the peak value of the message signal to the amplitude. Ask, fsk, and psk can be readily extended to multiple level mary signaling and demodulated coherently or non coherently. Use time domain and frequency domain to identify the characteristics of these baseband pulse modulations. The pulse amplitude returns to a zerovolt level for a portion usually onehalf of the pulse or bit period manchester. Ee4512 analog and digital communications chapter 3. Baseband is a signal that has a nearzero frequency range, i. In particular, we discuss amplitude and frequency modulation. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Each symbol represents n bits, and has m signal states, where m 2n. The power efficiency is the ability of a modulation technique to preserve the fidelity. The process of superimposing a low frequency signal onto a high frequency signal three modulation schemes available.
Baseband modulation techniques are also called line codes. Digital baseband modulation techniques chapter 4 receiver design chapter 5 digital bandpass modulation and demodulation techniques. Digital modulation techniques are essential to many digital communication systems, whether it is a telephone system, a mobile cellular communication system, or a satellite communication system. Ppm is a modulation technique to increase transmission efficiency in the fso communication system. For example, each ethernet connection has a dedicated ethernet cable, so it can be modulated as baseband. Fm is considered an analog form of modulation because the baseband signal is typically an analog waveform without discrete, digital values.
This is accomplished through modulation of radio signals. Ppm is an orthogonal baseband modulation technique and has been studied extensively in optical communication for its superior power efficiency compared to any other baseband modulation techniques and thus makes it well suited for handheld devices that require low consumption. This paper concentrates on baseband pulse time modulation techniques that are used to modulate data for. When expressed as a percentage it is the same as the depth of modulation. Pulse code modulation systems are commonly used in public and private telephone networks. Baseband modulationdemodulation techniques wikiversity. Although the example uses phase modulation, most elements of this example apply to other analog modulation techniques as well. Radio, tv, cell phones must use modulations like am, fm or qam, since they share the air medium with many other transmitters, and each one must fit in a thin slice of the bandwidth.
A binary 1 is denoted by a transition from a positive pulse to a negative pulse in the middle of. Linear modulation techniques vary the amplitude of a high frequency carrier signal. Bandpass ask is similar to baseband pulse amplitude modulation pam in chapter 2, baseband modulation and demodulation, but fsk, psk, and qam are new nonlinear modulation techniques. Then it simulates an additive white gaussian noise awgn channel, demodulates the received signal, and plots the original and demodulated signals. This carrier signal is called the modulated signal, while the information carrying, or baseband signal is referred to as the modulating signal.
Most radio systems in the 20th century used frequency modulation fm or amplitude modulation am for radio broadcast a modulator is a device that performs modulation. If we were to implement every possible combination of demodulation algorithm, carrierrecovery technique, and clock regeneration as a distinct model, the combinatorial explosion of different models would become unmanageable. Baseband pulse modulations are mainly used over guided transmission media such as pair wires and optical fiber. This is basically modulating the intensity of the signal in order to transmit information. Modulation is the process of encoding information onto a carrier signal which has frequency fc. Pdf advanced modulation techniques for low papr in vlc. In telecommunications and signal processing, baseband signals are transmitted without modulation, that is, without any shift in the range of frequencies of the signal.
Hapter modulation and demodulation mit opencourseware. The aim of digital baseband modulation methods, also known as line coding. Besides ask and ook, duobinary baseband modulation has also be implemented by bell laboratories, who transmitted a 2. Implement baseband pulse modulations of pam, pwm and ppm. Once a signal has been modulated, information is retrieved through a demodulation process. The pulse amplitude returns to a zerovolt level for a portion usually onehalf of the pulse or. Introduction to iq demodulation of rfdata september 15, 1999 page 3 of 1 introduction 1. Modulation technique an overview sciencedirect topics.
If we consider the voice signal then voice signal band is approximately 4khz. The modulation concept, baseband signal, bandpass signal, message signal, carrier signal, modulated signal, modulation, types of modulation, amplitude modulation am, angle modulation, frequency modulation fm, phase modulation pm. With llr demodulation, one can use the viterbi decoder either in the unquantized decoding mode or the softdecision decoding mode. Frequency modulation consists of encoding information onto a carrier signal by varying the frequency of the carrier. Results 1 24 of 24 digital modulation techniques by fuqin xiong and a great selection of similar used, new and collectible books available now at. Unit 1 lab 1 unit 1 lab 1 baseband pulse modulations. To learn more about digital modulation, see digital modulation. The baseband signal usually consist of a finite set of symbols. These modulation formats can possess rather wide transmission bandwidths. 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.
That means voice signal contains frequencies ranging from 04khz. An audio signal is lowpass filtered to 10 khz, resulting in a baseband signal with a spectrum from 0 hz or strictly, 20 hz to 10 khz. The syllabus and lecture slides in adobe pdf format for the one semester undergraduate course ee4512 analog and digital communications are given here. Analog information is formatted using three separate processes. Chapter 6modulation techniques shandong university. The example samples an analog signal and modulates it. In all cases, the formatting step results in a sequence of binary digits. Frequency modulation fm is a form of modulation in which changes in the carrier wave frequency correspond directly to changes in the baseband signal. All about modulation part i basic concepts, signal space, constellations and phase shift keying modulations psk, qpsk, oqpsk, mpsk. Understanding modern digital modulation techniques. Rf and baseband techniques for software defined radio.
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