An ideal frequency modulated fm signal discriminators output is pro. The difference between the modulation and demodulation is that modulation is to transfer the message signal by adding it with the carrier signal while demodulation is the process of filtering out the actual message signal from the carrier signal. The term demodulator is used because the demodulation process is considered to be the opposite of modulation. 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. What is fm, frequency modulation electronics notes. Two of them mixed and pll demodulator are are implemented on the dsp tms320c6711dsk. It works not only with amplitude modulation but also with frequency and phase modulation.
The fmmodulated signal has its instantaneous frequency that varies linearly with the amplitude of the message signal. Jun 05, 2015 guide students to gain a working understanding of theories such as demodulation, bandwidth, and carsons rule. In telecommunications and signal processing, frequency modulation fm is the encoding of information in a carrier wave by varying the instantaneous frequency of the wave in analog frequency modulation, such as fm radio broadcasting of an audio signal representing voice or music, the instantaneous frequency deviation, the difference between the frequency of the carrier and its center. Frequency modulation and demodulation file exchange. Guide students to gain a working understanding of theories such as demodulation, bandwidth, and carsons rule. If a high pass filter is used, the demodulation process is much more linear since the. Pulse modulation in the pulse modulation, the continuous signal is converted into a series of pulses, each proportional to the amplitude of the signal and corresponding in time. The circuit in which restoration is achieved is called the detector. The block diagram of a discretetime version of a pll is shown in the. The spectrum of an fm signal is quite complicated and is dependent on mf.
The goal of this experiment is to become familiar with fm modulation and demodulation. Slide 6 narrow band fm slide 7 bandwidth of an fm signal slide 8 demod. 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. A bandpass filter isolate the fm signal with carrier frequency n.
Each channel sharing scheme a set of basis vectors. Using a phaselockedloopfor fm demodulation a device called a phaselockedlooppll can be used to demodulate an fm signal with better performance in a noisy environment than a frequency discriminator. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam. A noncoherent detector has only one input, namely, the modulated signal port. A interesting solution is to solve this with digital signal processing. In any radio that is designed to receive frequency modulated signals there is some form of fm demodulator or.
For a perfect modulation, the value of modulation index should be 1, which means the modulation depth should be 100%. Fm modulation and demodulation will be presented and you will implement two types of demodulators, the frequency discriminator and the phaselocked loop. Mar 05, 2019 frequency modulation fm is an important modulation scheme both because of its widespread commercial use, and because of its simplicity. To understand the theoretical foundations for angle modulation as well as frequency modulation fm and demodulation. 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. Learn about two techniques for recovering the baseband signal from a frequency modulated carrier. Modulation fm, amplitude shift keying ask, phase shift keying psk, etc. Phasemodulation and demodulation techniques are more complex than modulation and demodulation based on amplitude and frequency. However this is much less of an issue these days because many radio. In modulation, one characteristic of a signal generally a sinusoidal wave known as the carrier is changed based on the information signal that we wish to transmit modulating signal.
Difference between modulation and demodulation compare the. In this chapter we will discuss ways of demodulating am, cw, fm, phase, and pulse modulation. Once a signal has been modulated, information is retrieved through a demodulation process. This principle is at the heart of amplitude modulation. Therefore, phase modulation is in reality a second form of frequency modulation. Fm demodulation august 29, 20 by ashutosh bhatt frequency modulation fm is a technique in which the frequency of a transmitted waveform is varied according to the variations in the message wave. Berrou c, glavieux a, thitimajshima p 2010 near shannon limit errorcorrecting pdf.
The am fm modulation model and a multiband analysis demodulation scheme is applied to speech formant frequency and bandwidth tracking. Fm modulation introduction in this lab, you will investigate frequency modulation fm and its properties. In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors. In an earlier semester project, four fm demodulation algorithms were developed and tested on their suitability. Jul 02, 2018 in this video, i have explained frequency modulation fm by following outlines. The circuit in which restoration is achieved is called the detector or demodulator both of these terms are used in neets. Am modulation where the amplitude of the carrier does not depend on the value of the modulating signal. Definition of an fm signal for a baseband signal, xt. As we have seen in this document, frequency modulation can be simplified to angle modulation with a simple integrator. One of the minor disadvantages of frequency modulation is that the demodulator is a little more complicated, and hence slightly more expensive than the very simple diode detectors used for am.
In addition to audio signal, it can also be used in data pulse. As a result, most data transmission system use psk. During this lab you will create an fm signal by modulating an audio waveform onto a carrier, examine the spectrum of the modulated carrier, evaluate the modulated carrier when the modulation index is varied and. Filtering is performed by a bank of gabor bandpass filters. Fm can be created by applying message signals directly to a voltagecontrolled oscillator vco, so that the vcos output will be a function of the input signal. Frequency modulation offers improved performance over amplitude modulation, but it is somewhat more difficult to extract the original information from an fm waveform. First lets look at the i and q waveforms that are produced when we apply quadrature demodulation to frequency modulation. Fm has poorer spectral efficiency than some other modulation formats. To implement the simulink models for fm including a basic sinusoid and a multimedia file music to analyze each signal in time and frequency domains using time scope and spectrum analyzer. Frequency modulation we wary the frequency of the carrier linearly with the modulation. It is the extent of modulation denoted in percentage, and is denoted by m. Amplitude modulation, am, is one of the most straightforward ways of modulating a radio signal or carrier.
Analog communication fm demodulators in this chapter, let us discuss about the demodulators which demodulate the fm wave. The discussion then moves to binary phase shift keying bpsk and shows how this simpler format is modeled using the generic quadrature modulation models. The phase angle cannot change without also affecting a change in frequency. That could be the amplitude, phase, or frequency, which result in amplitude modulation am, phase modulation pm, or frequency modulation fm. Implementation of fm demodulator algorithms on a high performance digital signal processor tms320c6711 dsp franz schnyder christoph haller 11.
Fm demodulator circuits are found in any receiver that uses fm. The received fm waveform is a 100 khz carrier modulated by a 100 hz sinusoid. Quadrature frequency and phase demodulation radio frequency. In this video, i have explained frequency modulation fm by following outlines. Frequency modulation fm is the standard technique for highfidelity. Implementation of fm demodulator algorithms on a high. Slide 3 discretetime fm modulator slide 4 single tone fm modulation slide 5 single tone fm cont. Fm modulationdemodulation with pll general description package outline njw2307 is a fm modulation demodulation ic for audio signal in full duplex communication that operates from 3. The amfm modulation model and a multiband analysisdemodulation scheme is applied to speech formant frequency and bandwidth tracking. Modulation and demodulation hold dominant positions in communication. Modulation and demodulation techniques request pdf. A similar approach is then taken for developing models for multiple phase shift keying mpsk, minimum shift keying msk, and frequency shift.
Modulation is defined as the process of transmission of information such as images or videos on an electrical signal. The input data is a sine wave of frequency 4 hz and amplitude 1 v. Teach the basics of frequency modulation and demodulation. Frequency modulation consists of encoding information onto a carrier signal by varying the frequency of the carrier. Demodulation is defined as the process of extracting this information.