Amplitude and frequencyphase modulation zurich instruments. Instead of outputting digital values that are either low 0v or high 5v. Armstrong, known as one of the founding fathers of radio technology, invented the superheterodyne radio receiver in 1918 and frequency modulation fm in 1933 1. Polar view of digital iq modulation contd transmission signal is sine wave at frequency f 0 with information encoded in discrete values of amplitude and phase. Other modulation methods amplitude modulation the amplitude of the carrier signal is controlled by the modulating signal pitfall of am. Those light waves may be sent through a transparent medium as a laser beam, or contained within a fiber optic cable. Minimum shift keying msk is one of the most spectrally efficient modulation schemes available. We therefore assume mta mcos2 f mtfor pm and mta msim2 f mtfor fm. Modulation is the process of altering the characteristics of the amplitude, frequency, or phase angle of the highfrequency signal in accordance with the instantaneous value of the modulating wave. Phase of the baseband signal changes from 0 deg to 180 deg 2 transitions1 bit per symbol q out of phase phase diagram 1 0 i in phase qpsk. In this scheme during every bit duration, denoted by t, one of two phases of the carrier is transmitted. Digital phase modulation and demodulation request pdf. Frequency modulation is the process of varying the frequency of the carrier signal linearly with the message signal. In phase modulation pm the instantaneous angular frequency.
What is carrierless amplitude and phase modulation. Therefore, at t1, the phase modulated carrier also changes corresponding to e1, as shown in figure a. Where n index of refraction of medium wave travels. Phasemodulation and demodulation techniques are more complex than modulation and demodulation based on amplitude and frequency. If the phase of the high frequency carrier wave is varied in accordance with the instantaneous value of the modulating signal, then such a technique is called as phase modulation. Request pdf digital phase modulation and demodulation digital phase modulation is a class of power and bandwidthefficient modulations widely used in telecommunications. Phase modulation pm is used primarily in digital communication amplitude, frequency and phase modulation. The other type of modulation in continuouswave modulation is the angle modulation. As a result, most data transmission system use psk. Phase modulation, pm is sometimes used for analogue transmission, but it has become the basis for modulation schemes used for carrying data. Phase modulation is the basis for many digital modulation formats, in which a modulated signal is divided into inphase 0. Quadrature modulation the occupied bandwidth can be reduced by converting the data to two slower streams and impressing each stream on the sine and cosine of carrier.
The advantage of cap over qam is the simpler implementation. However, more recently with the advent of lowcost microcontrollers and the introduction of domestic mobile telephones and satellite communications, digital modulation has gained in popularity. Matlab has unwrap function to remove discontinuities. This is further divided into frequency and phase modulation. This is shown in block diagram form in figure 2 below. Phase modulation pm is that form of angle modulation in which the instantaneous angle. Put scope in xy mode put am signal on vertical put intelligence signal on horizontal through rc phaseshift network possible results see fig 223. In pulse modulation, a periodic sequence of rectangular pulses, is used as a carrier wave. Amplitude modulation am frequency modulation fm phase modulation pm click on the links given above to know more. Types of modulation 6 flynnkatz 7810 analog modulation amplitude modulation, am frequency modulation, fm double and single sideband, dsb and ssb digital modulation phase shift keying. The application of the heterodyne principle to modulation is shown schematically in figure 143. Phase modulation equation of phase modulation pm wave.
May 31, 2015 carrierless amplitude phase modulation cap is essentially a different implementation of traditional quadrature modulation qam. For example, quadrature phase shift keying qpsk is performed as follows. In a quadrature phase modulation format such as quadrature phase shift keying qpsk, where four phase angles are used to represent the digital bits, two bits of digital information are able to be carried with each phase angle, so that the information can be represented as 00, 01, 10, and 11. Modulationtypesamplitude,frequency,phase modulation.
Frequency modulation and phase modulation presented a certain immunity to noise, whereas amplitude modulation was simpler to demodulate. Msk is a special case of continuousphase frequency shift keying cpfsk which is a special. All about modulation part i basic concepts, signal space, constellations and phase shift keying modulations psk, qpsk, oqpsk, mpsk. Optical modulation a tutorial introduction to optical modulation techniques by gary breed editorial director t his article introduces the subject of optical modulation, the process of applying information to a light wave.
Trapezoidal patterns method to check proper modulation of am signal more revealing than viewing signal on scope procedure. Going back to the original equation of the carrier, change the phase the underlined term only from a constant to a function of time. Phase modulation weichih wang southern taiwan university of technology. Pwm is a technique which uses digital means to get an analog result. In other words the speed of rotation around the circle is modulated about the mean value. A tutorial introduction to optical modulation techniques. I always had difficulties in understanding frequency modulation fm and its.
Some phase modulation and quadrature amplitude modulation formats have a higher spectral efficiency for data transmission than frequency shift keying, a form of frequency modulation. An important feature of angle modulation is that it can provide better. Frequency modulation fm tutorial in digital and analog modulation tutorial basics duration. All about modulation basic concepts, signal space, constellations and phase shift keying modulations psk, qpsk, oqpsk, mpsk. This is further divided into analog and digital modulation. Quadrature amplitude modulation qam national instruments. This changes the phase of the signal from what it would have been if no modulation was applied. Phase shoft keying, psk is widely used for data communication. Frequency modulation the frequency of the carrier signal is proportional to the modulating signal phase modulation. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam.
The amplitude modulation and demodulation technique involved in this project comprises of three stages. Carrierless amplitudephase modulation cap is essentially a different implementation of traditional quadrature modulation qam. The phase change is converted into an intensity change using interferometric schemes machzehnder, michelson, fabryperot or sagnac forms. 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. In this method of modulation the amplitude of the carrier wave is maintained constant. These methods contrast with amplitude modulation, in which the amplitude of the carrier wave varies, while the frequency and phase remain constant. Angle modulation is the process in which the frequency or the phase of the carrier varies according to the message signal.
The pwm signal plot looks something like as shown in the diagram below. Phase of the baseband signal changes from 45 deg, 5 deg, 225 deg, 315 deg 4 transitions2 bits per symbol q out of phase i in phase phase diagram 11 10 01 00 radius. Fm has poorer spectral efficiency than some other modulation formats. Introduction modulation is used in efficient radiation of signals. For example, the message signal mt is made up of two different. Pm and digital modulation s p where 2 is the pkpk phase change in one symbol duration, t for digital signals the modulation index. One of the easiest ways to implement qam with hardware is to generate and mix two sine waves that are 90 degrees out of phase with one another.
Fm frequency modulation pm phase modulation continued ee44510 22 narrowband fm only the j o and j 1 terms are significant same bandwidth as am using eulers identity, and. Readers are presented with stepbystep derivations showing the operation of qpsk modulation and demodulation. Fsk frequency shift keying d1 61 conceptually, and in fact, the transmitter could consist of two oscillators on frequencies f1 and f2, with only one being connected to the output at any one time. Just as in radio, optical systems started out with amplitude modulation, which is known as onoffkeying or ook. Principles of communication modulation tutorialspoint. Interferometer criteria for waveguide or fiber optic based. Since the three variables are the amplitude, frequency, and phase angle, the modulation can be done by varying any one of them. Fm signals have the same peak frequency deviation, then when mt is a sinusoidal signal set such that the pm and note.
The continuous phase advantage of the vco is not accompanied by an ability to ensure that f1 and f2 are integer multiples of the bit rate. Amplitude and phase modulation can be used together. Phase modulation pm changes only the phase of the signal. Frequency modulation the frequency of the carrier signal is proportional to. There are two common forms of angle modulation, namely, phase modulation and frequency modulation. This phase remains to this attained value until time t2, as between t1 and t2, the amplitude of. 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.
Amplitudemodulationanddemodulation electronics tutorial. However, they provide the benefit of higher data rates for the amount of bandwidth consumed. We shall focus more on frequency modulation in this course and less on phase modulation. Minimum shift keying msk a tutorial qasim chaudhari. Mar 05, 2019 quadrature amplitude modulation qam requires changing the phase and amplitude of a carrier sine wave. Enough about modulation theory, lets get a more practical view of what pwm really is. Spectra have a typical trapezoidal shape in linear frequency and amplitude in decibels. Even though pm is used in analog transmissions, it is widely used as a digital type of modulation wherever it controls among dissimilar phases, which is known as psk phase shift keying, and there are several forms are available in this. Aug 30, 2018 pwm stands for pulse width modulation. Quadrature amplitude modulation qam requires changing the phase and amplitude of a carrier sine wave. At time t1, the amplitude of mt increases from zero to e1. Amplitude modulation and demodulation abstracta single tone sinusoidal signal is transmitted using amplitude modulation and is demodulated at the receivers end using an envelope detector and the attenuated signal is amplified using common source bjt amplifer i.
Both modulated carriers are summed to result in a signal with amplitude and phase modulation. We can draw a set of points in the iq plane that represent symbols to transmit. The phase modulated signal st is thus described in the time domain by. Frequency modulation and phase modulation are closely related. For instance, if we transmit i 0a and q 0, then we have a simple ask system amplitude shift keying. This feature provides microcontrollers by a mean of, seemingly, outputting analog values of voltage between 05v. Therefore we only consider the case where the message signal mtis a sinusoidal signal. Frequency modulation fm looks similar to phase modulation, though frequency is the controlled parameter, rather than relative phase. Msk is a special case of continuous phase frequency shift keying cpfsk which is a special. The transition from analog communication to digital has advanced the use of qpsk. A radio frequency signal consists of an oscillating carrier in the form of a sine wave is the basis of the signal. Lecture 2829 fm frequency modulation pm phase modulation.