A binary 1 is denoted by a transition from a positive pulse to a negative pulse in the middle of. 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. 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. The ber performance improvement for qpsk modulation when using loglikelihood ratio llr instead of harddecision demodulation in a convolutionally coded communication link. In the usual development of data modulation techniques as presented in most communications texts, the. Fm is considered an analog form of modulation because the baseband signal is typically an analog waveform without discrete, digital values. Hapter modulation and demodulation mit opencourseware. Chapter 6modulation techniques shandong university. So now lets discuss different types of pulse modulation techniques in detailpulse modulation can be categorized broadly into two types.
Optical wireless communication systems employ imdd. The example samples an analog signal and modulates it. Passband signals were originally baseband, but were modulated, or frequencyshifted or upconverted for some purpose, usually to make them fit in a passband channel. 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.
The amplitude modulation am modulation index can be defined as the ratio of the peak value of the message signal to the amplitude. 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. This carrier signal is called the modulated signal, while the information carrying, or baseband signal is referred to as the modulating signal. These are analog modulation formats amplitude, phase, frequency or quadrature modulation with baseband binary linecode messages having rectangular bit symbol pulses. What links here related changes upload file special pages permanent. Digital baseband modulation techniques chapter 4 receiver design chapter 5 digital bandpass modulation and demodulation techniques.
Baseband modulation techniques are also called line codes. Unit 1 lab 1 unit 1 lab 1 baseband pulse modulations. We consider binary modulation schemes and multilevel modulation schemes here. The baseband signal usually consist of a finite set of symbols. We reiterate and elaborate on those reasons in section 14.
This site is like a library, use search box in the widget to get ebook that you want. 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. Techniques baseband modulation using rectangular pulses and binary pulse amplitude modulation pages 7688. Frequency modulation fm is a form of modulation in which changes in the carrier wave frequency correspond directly to changes in the baseband signal. The sampling rate, or number of samples per second, is. Ask, fsk, and psk can be readily extended to multiple level mary signaling and demodulated coherently or non coherently. Understanding modern digital modulation techniques. Analog information is formatted using three separate processes.
Pdf modulation is an integral part of every modern communication systems and provides a. The pulse amplitude returns to a zerovolt level for a portion usually onehalf of the pulse or. Pulse code modulation systems are commonly used in public and private telephone networks. 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. In electronics and telecommunications, modulation is the process of varying one or more. Baseband is a signal that has a nearzero frequency range, i. The syllabus and lecture slides in adobe pdf format for the one semester undergraduate course ee4512 analog and digital communications are given here. In all cases, the formatting step results in a sequence of binary digits. Baseband transmission sends the information signal as it is without modulation without frequency shifting while passband transmission shifts the signal to be. With llr demodulation, one can use the viterbi decoder either in the unquantized decoding mode or the softdecision decoding mode.
This is accomplished through modulation of radio signals. All about modulation part i basic concepts, signal space, constellations and phase shift keying modulations psk, qpsk, oqpsk, mpsk. Modulation is the process of encoding information onto a carrier signal which has frequency fc. 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.
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. The aim of digital baseband modulation methods, also known as line coding. Ee4512 analog and digital communications chapter 3. Frequency modulation consists of encoding information onto a carrier signal by varying the frequency of the carrier. The process of superimposing a low frequency signal onto a high frequency signal three modulation schemes available. We discuss discrete changes in the characteristics of the carrier digital modulation in 14. 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.
Modulation technique pdf we begin our discussion of digital modulation by starting with the three basic types of digital modulation techniques. 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. Once a signal has been modulated, information is retrieved through a demodulation process. Implement baseband pulse modulations of pam, pwm and ppm.
Introduction to iq demodulation of rfdata september 15, 1999 page 3 of 1 introduction 1. That means voice signal contains frequencies ranging from 04khz. This paper concentrates on baseband pulse time modulation techniques that are used to modulate data for. Baseband pulse modulations are mainly used over guided transmission media such as pair wires and optical fiber. For example, each ethernet connection has a dedicated ethernet cable, so it can be modulated as baseband. Amplitude modulation early radio ee 442 spring semester. Digital modulation techniques by fuqin xiong, available at book depository with free delivery worldwide. Although the example uses phase modulation, most elements of this example apply to other analog modulation techniques as well. Request pdf digital modulationbaseband techniques digital modulation is the process which transforms an input bit stream into a digitally encoded. 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. Then it simulates an additive white gaussian noise awgn channel, demodulates the received signal, and plots the original and demodulated signals. Ee4512 analog and digital communications chapter 3 chapter 3 digital baseband modulation techniques goals in communication system design pages 7576.
Modulation technique an overview sciencedirect topics. Rf and baseband techniques for software defined radio. Baseband modulation and demodulation techniques are fundamental to communication systems. 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. In telecommunications and signal processing, baseband signals are transmitted without modulation, that is, without any shift in the range of frequencies of the signal. Textual information is transformed into binary digits by use of a coder. These modulation formats can possess rather wide transmission bandwidths.
The power efficiency is the ability of a modulation technique to preserve the fidelity. Besides ask and ook, duobinary baseband modulation has also be implemented by bell laboratories, who transmitted a 2. In order to minimize the bit error probability, we use a technique known as. Ppm is a modulation technique to increase transmission efficiency in the fso communication system. In particular, we discuss amplitude and frequency modulation. 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. Bandpass modulation and demodulation techniques communication systems, dept.
Pulse code modulation an overview sciencedirect topics. Each symbol represents n bits, and has m signal states, where m 2n. 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. 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. One way to reduce the transmission bandwidth is to reduce the message bandwidth. Linear modulation techniques vary the amplitude of a high frequency carrier signal. 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. Click download or read online button to get rf and baseband techniques for software defined radio book now. Baseband modulationdemodulation techniques wikiversity. To learn more about digital modulation, see digital modulation. When expressed as a percentage it is the same as the depth of modulation. Pdf advanced modulation techniques for low papr in vlc.
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