Frequency modulation consists of encoding information onto a carrier signal by varying the frequency of the carrier. Analog information is formatted using three separate processes. When expressed as a percentage it is the same as the depth of modulation. Ppm is a modulation technique to increase transmission efficiency in the fso communication system. 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. Then it simulates an additive white gaussian noise awgn channel, demodulates the received signal, and plots the original and demodulated signals. A binary 1 is denoted by a transition from a positive pulse to a negative pulse in the middle of. This is basically modulating the intensity of the signal in order to transmit information.
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. Modulation is the process of encoding information onto a carrier signal which has frequency fc. In electronics and telecommunications, modulation is the process of varying one or more. To learn more about digital modulation, see digital modulation. Baseband transmission sends the information signal as it is without modulation without frequency shifting while passband transmission shifts the signal to be. The process of superimposing a low frequency signal onto a high frequency signal three modulation schemes available. This site is like a library, use search box in the widget to get ebook that you want.
Frequency modulation fm is a form of modulation in which changes in the carrier wave frequency correspond directly to changes in the baseband signal. This carrier signal is called the modulated signal, while the information carrying, or baseband signal is referred to as the modulating signal. What links here related changes upload file special pages permanent. Chapter 6modulation techniques shandong university. We discuss discrete changes in the characteristics of the carrier digital modulation in 14. In the usual development of data modulation techniques as presented in most communications texts, the. Modulation technique pdf we begin our discussion of digital modulation by starting with the three basic types of digital modulation techniques. The pulse amplitude returns to a zerovolt level for a portion usually onehalf of the pulse or bit period manchester. Ask, fsk, and psk can be readily extended to multiple level mary signaling and demodulated coherently or non coherently. Understanding modern digital modulation techniques. Use time domain and frequency domain to identify the characteristics of these baseband pulse modulations. Hapter modulation and demodulation mit opencourseware. The pulse amplitude returns to a zerovolt level for a portion usually onehalf of the pulse or.
The baseband signal usually consist of a finite set of symbols. Passband signals were originally baseband, but were modulated, or frequencyshifted or upconverted for some purpose, usually to make them fit in a passband channel. The sampling rate, or number of samples per second, is. Pulse code modulation systems are commonly used in public and private telephone networks. So now lets discuss different types of pulse modulation techniques in detailpulse modulation can be categorized broadly into two types. We reiterate and elaborate on those reasons in section 14. Each symbol represents n bits, and has m signal states, where m 2n. In the past 20 years or so, research and development in digital modulation techniques have been very active and have yielded many promising results. Digital baseband modulation techniques chapter 4 receiver design chapter 5 digital bandpass modulation and demodulation techniques. Rf and baseband techniques for software defined radio. 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. This is accomplished through modulation of radio signals. 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.
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. Techniques baseband modulation using rectangular pulses and binary pulse amplitude modulation pages 7688. Click download or read online button to get rf and baseband techniques for software defined radio book now. 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. Baseband is a signal that has a nearzero frequency range, i. Pulse code modulation an overview sciencedirect topics. Bandpass modulation and demodulation techniques communication systems, dept. One way to reduce the transmission bandwidth is to reduce the message bandwidth.
Implement baseband pulse modulations of pam, pwm and ppm. Baseband pulse modulations are mainly used over guided transmission media such as pair wires and optical fiber. In particular, we discuss amplitude and frequency modulation. 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. 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 ber performance improvement for qpsk modulation when using loglikelihood ratio llr instead of harddecision demodulation in a convolutionally coded communication link. Baseband modulation and demodulation techniques are fundamental to communication systems. In telecommunications and signal processing, baseband signals are transmitted without modulation, that is, without any shift in the range of frequencies of the signal. 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. 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.
In order to minimize the bit error probability, we use a technique known as. The syllabus and lecture slides in adobe pdf format for the one semester undergraduate course ee4512 analog and digital communications are given here. 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. 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. Amplitude modulation early radio ee 442 spring semester. We consider binary modulation schemes and multilevel modulation schemes here. The amplitude modulation am modulation index can be defined as the ratio of the peak value of the message signal to the amplitude. Request pdf digital modulationbaseband techniques digital modulation is the process which transforms an input bit stream into a digitally encoded. If we consider the voice signal then voice signal band is approximately 4khz.
Ee4512 analog and digital communications chapter 3. Besides ask and ook, duobinary baseband modulation has also be implemented by bell laboratories, who transmitted a 2. The aim of digital baseband modulation methods, also known as line coding. 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. Baseband modulationdemodulation techniques wikiversity.
Once a signal has been modulated, information is retrieved through a demodulation process. 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. Pdf advanced modulation techniques for low papr in vlc. The example samples an analog signal and modulates it. 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. 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.
In all cases, the formatting step results in a sequence of binary digits. 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. Linear modulation techniques vary the amplitude of a high frequency carrier signal. All about modulation part i basic concepts, signal space, constellations and phase shift keying modulations psk, qpsk, oqpsk, mpsk.
The power efficiency is the ability of a modulation technique to preserve the fidelity. With llr demodulation, one can use the viterbi decoder either in the unquantized decoding mode or the softdecision decoding mode. Textual information is transformed into binary digits by use of a coder. Unit 1 lab 1 unit 1 lab 1 baseband pulse modulations. Pdf modulation is an integral part of every modern communication systems and provides a. These are analog modulation formats amplitude, phase, frequency or quadrature modulation with baseband binary linecode messages having rectangular bit symbol pulses. That means voice signal contains frequencies ranging from 04khz. Optical wireless communication systems employ imdd. Baseband modulation techniques are also called line codes. Ee4512 analog and digital communications chapter 3 chapter 3 digital baseband modulation techniques goals in communication system design pages 7576. 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. This paper concentrates on baseband pulse time modulation techniques that are used to modulate data for. Modulation technique an overview sciencedirect topics.
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