The applications of phase modulation include the following. Pm and digital modulation s p where 2 is the pkpk phase change in one symbol duration, t for digital signals the modulation index. Frequency modulation is the process of varying the frequency of the carrier signal linearly with the message signal. This video lecture explains different types of continuous wave modulation like amplitude modulation am, frequency modulation fm and phase modulation pm. Frequency modulation and phase modulation is a system in which the amplitude of the modulated carrier is kept constant, while its frequency and rate of change are varied by the modulating signal.
Frequency modulation fm is an important modulation scheme both because of its widespread commercial use, and because of its simplicity. In amplitude modulation, the amplitude of the carrier wave is modified in order to transmit information. As we have seen in this document, frequency modulation can be simplified to angle modulation with a simple integrator. This section sets out the basic properties of fmpm signals and how we can produce them. Request pdf digital phase modulation and demodulation digital phase modulation is a class of power and bandwidthefficient modulations widely used in telecommunications. Frequency modulation an overview sciencedirect topics. In phase and frequency modulation, it is 90 degrees out of phase with respect to the carrier.
In the first part, the fundamental mathematical expressions for the three types of modulation are derived. The first practical system was put forward in 1936 as an alternative to am in an effort to make radio transmissions more resistant to noise. The phase modulated signal st is thus described in the time domain by. Phase modulation is the process of varying the phase of the carrier signal linearly with the message signal. There are two common forms of angle modulation, namely, phase modulation and frequency modulation. Angle modulation is further divided into frequency modulation and phase modulation. The first frequency modulation was invented by edwin howard armstrong in december181890 4. The dsbsc am coherent receiver requires a phase and frequency synchronous reference signal. Difference between amplitude modulation and frequency modulation type of modulation. Phase modulation index can be enhanced by employing frequency multiplier. Frequency and phase modulation are a form of angle modulation.
Angle modulation as the name implies always affects the phase angle and thus the frequency of the signal. Phase modulation amplitude modulation frequency modulation. Phase modulation pm is used primarily in digital communication. As phase and frequency are interrelated, this relationship carries forwards into phase modulation where it has many commonalities with frequency modulation. As we know from amplitude modulation, we need two sine or cosine waves for modulation. Pdf on jan 1, 2010, geng peng and others published modulation index estimation of frequency and phase modulated signals find, read. But phase modulation seems to be in a different categorypm radio is by no means a common term. Amamplitude modulation fmfrequency modulation pmphase modulation in phase modulation, modulation index is directly proportional to modulating voltage only while in frequency modulation, modulation index is also inversely proportional to modulat. Amplitude, phase, and frequency modulation ieee journals. Angle modulation is the process in which the frequency or the phase of the carrier varies according to the message signal.
Phase modulation equation of phase modulation pm wave. Modulation allows for the designated frequency bands with the carrier frequency at the center of the band to be utilized for communication and allows for signal multiplexing. In either case, the frequency of the modulated signal changes as a. Photonic measurement of microwave frequency based on phase modulation article pdf available in optics express 179. 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. Oct 05, 2015 the main difference between amplitude modulation and frequency modulation is that, in amplitude modulation, the amplitude of the carrier wave is modified according to the data whereas, in frequency modulation, the frequency of the carrier wave is modified according to the data. In an earlier section we saw how amplitude modulation am can be used to convey information. I always had difficulties in understanding frequency modulation fm and its frequency spectrum. When we do frequency modulation, we are differentiating the particular modulating signal which then automatically depicts it as phase modulation. Frequency modulation is a form of analog angle modulation in which the baseband informationcarrying signal, typically called the message or information signal mt, varies the frequency of a.
Amplitude, frequency and phase modulation can be applied directly by software to the generated signals, which gives great flexibility where complicated and precise waveforms are required. This modulation is very useful in radio waves transmission, and it is an essential element in. As a result, most data transmission system use psk. As the name implies, phase modulation, pm uses variations in phase for carrying the modulation. Fm signals have the same peak frequency deviation, then when mt is a sinusoidal signal set such that the pm and note. Phase modulation article about phase modulation by the. The sound quality offered by am radio stations is poorer, having low. Both modulation techniques belong to the group of angle modulation techniques. In chapter1, we investigated the way of modulating a sinusoidal carrier wave using am technique.
This form of modulation is often considered a variation of fm. Amplitude modulation an overview sciencedirect topics. Since the three variables are the amplitude, frequency, and phase angle, the modulation can be done by varying any one of them. The other type of modulation in continuouswave modulation is the angle modulation. Amplitude modulation am frequency modulation fm phase modulation pm click on the links given above to know more. An important feature of angle modulation is that it can provide better. As a result the term angle modulation is often use to describe both. The carrier amplitude is constant and the phase variation of the signal contains the information. Amplitude modulation am is an analog and linear modulation process as opposed to frequency modulation fm and phase modulation pm. What is fm, frequency modulation electronics notes. Phase modulation is similar to frequency modulation and is an important technique in digital communication systems. However if st is sinusoidal, then the instantaneous frequency deviation of the anglemodulated signal is. For example, if you set up m path 1 for normal phase modulation with a carrier frequency of 400 mhz, and a rate of 100 khz, the maximum peak deviation that you can set is 0.
Frequency modulation definition of frequency modulation by. Definition of an fm signal for a baseband signal, xt. It encodes a message signal as variations in the instantaneous phase of a carrier wave. Analog communication angle modulation tutorialspoint. Amamplitude modulation fm frequency modulation pm phase modulation in phase modulation, modulation index is directly proportional to modulating voltage only while in frequency modulation, modulation index is also inversely proportional to modulat. In an fm wave, the total phase changes due to the change in the frequency of the carrier corresponding to the changes in the modulating amplitude. Amplitude and frequencyphase modulation zurich instruments. Phase modulation is one of the two principal forms of angle modulation, together with frequency modulation. Berrou c, glavieux a, thitimajshima p 2010 near shannon limit errorcorrecting pdf. The process of phase modulation is somewhat the same as that of frequency modulation. Digital phase modulation and demodulation request pdf. Even for the pure tone modulation, the fm spectrum consists of an in nite number of sidebands. Frequency modulation and phase modulation are the two complementary principal methods of angle modulation. If a constant amplitude as well as constant frequency sine wave carrier is given to the phase shifter the output is phase modulated signal.
Fm has poorer spectral efficiency than some other modulation formats. By means of the modulation vector, a new vector diagram of the phase modulation is given. Wide band fm first lets know about the frequency modulation 3. Phase modulation pm is another form of angle modulation. If we do phase modulation it is nothing but a frequency modulation. Cap carrierless amplitude phase modulation was the original approach for the modulation of a digital subscriber line dsl signal. Frequency modulation definition, basics and waveform hd. The mathematical representation of frequency modulation consists of a sinusoidal expression with the integral of the baseband signal added to the argument of the sine or cosine function. Feb 26, 2017 in frequency modulation there are two types 1. A radio frequency signal consists of an oscillating carrier in the form of a sine wave is the basis of the signal.
In frequency modulation, the instantaneous frequency of the carrier wave is modified in order to transmit information. Example commercial fm signals use a peak frequency deviation of. We also mentioned that frequency modulation fm and phase modulation pm can also be used. Fm is a so called angle modulation scheme, it was inspired by phase modulation but has proved to be more useful partly for its ease of generation and decoding. Amplitude and frequencyphase modulation i always had di culties in understanding frequency modulation fm and its frequency spectrum. Frequency modulation is a form of analog angle modulation in which the baseband information carrying signal, typically called the message or information signal mt, varies the frequency of a carrier wave. Mar 05, 2019 frequency modulation fm is an important modulation scheme both because of its widespread commercial use, and because of its simplicity. Pdf modulation index estimation of frequency and phase. Chapter 6 analog modulation and demodulation frequency modulation and phase modulation pages 334343. Frequency modulation is that from of angle modulation in which the instantaneous. Modulation fm, amplitude shift keying ask, phase shift keying psk, etc. Feb 27, 2019 this video lecture explains different types of continuous wave modulation like amplitude modulation am, frequency modulation fm and phase modulation pm. What is the difference between phase modulation and frequency.
Continuous wave modulation amplitude modulation, frequency. There is another way of modulating a, sinusoidal carrier wave, namely, angle modulation in which the angle of the carrier wave is varied according to the baseband signal. With phase modulation, the change of the phase angle is proportional to the message that is. This modulation is very useful in radio waves transmission, and it is an essential element in several digital transmission coding schemes. Carrierless amplitude phase modulation cap is essentially a different implementation of traditional quadrature modulation qam. Difference between amplitude modulation and frequency. Oct 12, 2018 theory of frequency modulation and phase modulation. The modulation index can be used to make the frequency deviation more sensitive or less sensitive to variations in the baseband value. Frenzeljr, in handbook of serial communications interfaces, 2016. The two processes are closely related because phase cannot be changed without also. This is further divided into frequency and phase modulation. Lecture 2829 fm frequency modulation pm phase modulation. Modulationtypesamplitude,frequency,phase modulation.
Phase modulation pm is a modulation pattern for conditioning communication signals for transmission. Modulation is a process by which some characteristic amplitudefrequency or phase of a high frequency carrier wave is varied in accordance with the instantaneous value of the message signal. Frequency modulation, phase modulation, and fm spectra. Transmitter radio receiver between transmitter and radio receiver. What is the difference between phase modulation and.
In phase modulation, the amplitude of the carrier signal remains unchanged while phase change occurs. Pdf photonic measurement of microwave frequency based on. The useful links to difference between various terms are provided here. Pm have much in common and they are usually concluded as angle modulation, i.
We shall focus more on frequency modulation in this course and less on phase modulation. Frequency modulation definition of frequency modulation. Theory of frequency modulation and phase modulation. Phase modulationpm is the modulation technique in which carrier phase varies based on analog baseband information signal to be transmitted using wireless device. Radio waves can carry audio, video, and digital information over great distances by using changes in a carrier waves amplitude, frequency, or phase to represent the information being transmitted. Difference between amplitude modulation and frequency modulation.