The commonly used class of digital phase modulation schemes, that is, mary phase shift keying mpsk, are described in detail. The information signal instead of being sent directly, is sent over a carrier signal. Phaseshift keying psk is a digital modulation scheme that conveys data by. Digital phase modulation and demodulation request pdf. Phase shift keying psk is the digital modulation technique in which the phase of the carrier signal is changed by varying the sine and cosine inputs at a particular time. Digital phase modulation applications of communications. The last ten years have seen a great flowering of the theory of digital data modulation. You should recall from your study of pm that there is an incidental shift in frequency as the phase of the carrier is shifted.
The net result of this is that depending on the bandwidth time product bt. A modem is an equipment that performs both modulation and demodulation. Modulation l frequency modulation fm l most popular analog modulation technique l amplitude of the carrier signal is kept constant constant envelope signal, the frequency of carrier is changed according to the amplitude of the modulating message signal. The newest fundamental signal type to join the dwc pantheon is phaseshift keying psk. Ee4512 analog and digital communications chapter 6 the dsbsc am coherent receiver has a bandpass filter centered at f c and. Modulation and demodulation does not catch any channel noise.
Quadrature modulation formats increases the bit rate by 2x using the same symbol clock frequency and therefore same occupied bandwidth. All such digital modulation methods in which the phase of the carrier contains the information to be transferred are classi. A phase modulator within a laser resonator of a singlefrequency laser can be used for wavelength tuning, or for active mode locking fm mode locking of a laser a phase modulation of a beam with moderate modulation strength is often used in laser frequency stabilization schemes, e. Psk is an mary digital modulation scheme a binary information signal directly modulates phase of an analog carrier. Modulation, analog modulation, digital modulation, am,fm. Phaseshift keying psk all of these techniques vary a parameter of a sinusoid to represent the information which we wish to send. It encodes a message signal as variations in the instantaneous phase of a carrier wave. Phaseshift keying is a type of angle modulation as is fsk pure psk modifies the phase of a carrier but preserves amplitude and frequency. Metrics for digital modulation power efficiency ability of a modulation technique to preserve the fidelity of the digital message at low power levels designer can increase noise immunity by increasing signal power power efficiency is a measure of how much signal power should be increased to achieve a particular ber for a given. Therefore we only consider the case where the message signal mtis a sinusoidal signal. Digital iq modulation phase shift keying constellations lecture 9 analog and digital iq modulation. Phase modulation is preferred for digital transmissions because it offers better protection for transmitting signals which carry binary information i. Phase modulation pm changes only the phase of the signal. If both the amplitude and the phase are varied proportional to the information signal, quadrature amplitude modulation qam results.
Pdf classifications of digital modulation, the signal characteristics of the phase of the cycle will cause the phase wrapped and reduce overlapping. Modification in phase according to low frequency will give phase modulation. Phase modulation is one of the two principal forms of angle modulation, together with frequency modulation the phase of a carrier signal is modulated to follow the changing signal level amplitude. All communications toolbox demodulator functions, system objects and blocks can demodulate binary. This text deals with continuousphase modulation from several important angles cpm design based on maximization of the minimum euclidean distance and spectral bandwidth. For digital phase modulation, we only modulate the phase of the carrier. This phase remains to this attained value until time t2, as between t1 and t2, the amplitude of. The two processes are closely related because phase cannot be changed. Phase modulation article about phase modulation by the. Rp photonics encyclopedia phase modulators, optical. Some examples of applications of phase modulators are. In nonlinear digital phase modulation with memory, the modulated signal is constrained to maintain a constant envelope and continuous phase, avoiding abrupt changes in phase. Digital modulation in digital communications, the modulation process corresponds to switching or keying the amplitude, frequency, or phase of a sinusoidal carrier wave according to incoming digital data three basic digital modulation techniques amplitudeshift keying ask special case of am.
This book is a treatise on digital modulation theory, with an emphasis on these more. There are two common forms of angle modulation, namely, phase modulation and frequency modulation. Hence info is carried in the phase or frequency of the carrier. Pdf optical single sideband signal generation using. Pdf a algorithm of fast digital phase modulation signal recognition. A special case of cpm is continuous phase frequency shift keying cpfsk. This paper analyzes the performance of digital phase modulation systems in gaussian noise and determines required signaltonoise ratio as a function of th. Psk is another form of angle modulated later define in upcoming slides constant amplitude digital modulation.
We therefore assume mta mcos2 f mtfor pm and mta msim2 f mtfor fm. 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. Because of this incidental frequency shift, fm demodulators, such as the fosterseeley discriminator and the ratio detector, can also be. In laymans terms, modulation is a technique where one changes one or more parameters of a carrier signal to carry the information. The basic digital phasemodulation system provides a coherent phase reference. Psk technique is widely used for wireless lans, biometric, contactless operations, along with rfid and bluetooth communications. This book is a treatise on digital modulation theory, with an emphasis on these more recent innovations. Amplitude and phase modulation can be used together. 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. Phase modulation equation of phase modulation pm wave. Conceptually, phaseshift keying instantly switches between two or more outofphase but otherwise equivalent oscillators. In the previous page, we saw that we can use discrete variations in a carriers amplitude or frequency as a way of representing ones and zeros. Dpsk can be significantly simpler to implement than ordinary psk since there is.
Digital phase modulation is a versatile and widely used method of wirelessly transferring digital data. Optical single sideband signal generation using phase modulation of semiconductor optical amplifier june 2004 ieee photonics technology letters 165. This was because optical detectors are only sensitive to amplitude optical power and not to phase, and manipulating the phase of optical signals at high frequencies is difficult. Both processes aim to achieve transfer information with the minimum distortion, minimum loss and. Because phase and frequency are related to each other, a generic digital phase modula. Just as in radio, optical systems started out with amplitude modulation, which is known as onoffkeying or ook. Basic concepts, signal space, constellations and phase shift keying. Modulation summary l phase shift keying is often used, as it provides a highly bandwidth efficient modulation scheme. Digital modulation in communications systems an introduction. In phase modulation pm the intelligence is contained in the amount and rate of phase shift in a carrier wave. Interferometer criteria for waveguide or fiber optic based. Therefore, at t1, the phase modulated carrier also changes corresponding to e1, as shown in figure a.
Interference when two or more optical waves are present simultaneously in the same region of space, the total wave function is the sum of the individual wave functions. At that time it seemed odd to us that the subjects of errorcorrecting codes and data modulation were so separated. Again gmsk can be viewed as either frequency or phase modulation. Their signal waveform expressions, signal constellations, and power. Modulation is a process of mapping such that it takes your voice as an example of a signal converts it into. All about modulation part i basic concepts, signal space, constellations and phase shift keying modulations psk, qpsk, oqpsk, mpsk.
Phase shift keying is a special case of dpm in which the phase of the carrier is selected, in accordance with the digital symbol. Phase modulation and demodulation in matlab download. Digital phase modulation and demodulationdigital phase. Phase modulation the phase of a carrier wave is varied in response to the vibrations of the sound source in phase modulation pm. The code describes the way to modulate or demodulate a signal shift in its phase. Request pdf digital phase modulation and demodulation digital phase modulation is a class of power and bandwidthefficient modulations widely used in. The phase of the carrier is advanced or retarded up to 90o over the course of a bit period depending on the data pattern, although the rate of change of phase is limited with a gaussian response. Chapter 6modulation techniques shandong university. I think the spelling need to be checked,as ppt hasnt a meaning, anyhow, modulation means to include a certain message from any type into another transmitted carrier signal, including it has three types,am,fm, and pm pm is phase modulation wh. Phase modulation weichih wang southern taiwan university of technology. Phase modulation we can transmit the information of mt by varying the angle.
Performance of digital phasemodulation communication systems. The source code and files included in this project are listed in the project files. Analog modulation refers to the process of transferring digital low frequency baseband signal, like digital bitstream from computers over a higher frequency carrier signal such as a radio frequency band. With digital frequency modulation, the frequency of a carrier or a baseband signal is varied in discrete sections according to binary data.
Digital modulation in somewhat similar to the analog modulation except base band signal is of discrete amplitude level. Quadrature phase shift keying modulation pdf quaternary phase shift keying qpsk. Agilent digital modulation in communications systems iikt. Each symbol represents n bits, and has m signal states, where m 2n. This form of modulation is often considered a variation of fm. In order to transmit computer data and other digitized information over a communications channel, an analog carrier wave can be modulated to reflect the binary nature of the digital baseband signal. A sinusoid has three different parameters than can be varied.
Pm changes the phase angle of the complex envelope in direct proportion to the message signal. The following matlab project contains the source code and matlab examples used for phase modulation and demodulation. Ask, fsk, psk, and qam are all forms of digital modulation. Bpsk encodes one binary bit per symbol by a 180 o phase change of the carrier the occupied spectrum bandwidth is proportional to the symbol frequency. Frequency modulation fm looks similar to phase modulation, though frequency is the controlled parameter, rather than relative phase. Phase modulation pm phase shift keying psk digital modulation amplitude shift keying ask.
Cpm is an example of nonlinear digital phase modulation with memory. Phase modulation definition is modulation of the phase of a radio carrier wave by voice or other signal. It has its origins in a collabor ation among the authors that began in 1977. Amplitude modulation am changes only the magnitude of the signal. Phase modulation definition of phase modulation by. Fm signals have the same peak frequency deviation, then when mt is a sinusoidal signal set such that the pm and note. Phase modulation pm pm or phase modulation is the process of varying the instantaneous phase of carrier signal accordingly with instantaneous amplitude of message signal. If we compare digital modulation to analog modulation, we see that the abrupt transitions created by digital modulation result in. For a perfect modulation, the value of modulation index should be 1, which implies the percentage of modulation should be 100%. Modulation is the process of influencing data information on the carrier, while demodulation is the recovery of original information at the distant end from the carrier. The parameters of the carrier that can be modified are the amplitude.
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