The left and right channels each limited to 15khz are multiplexed into a single baseband signal using amplitude modulation using frequency modulation to shift the baseband. Digital modulation bnrg university of california, berkeley. Modulation summary l phase shift keying is often used, as it provides a highly bandwidth efficient modulation scheme. This form of modulation varies the frequency in line with the modulating signal.
Let us take a look at the structure of fm transmitter and fm receiver along with their block diagrams and working. Frequency versus amplitude modulation l amplitude modulation am l changes the amplitude of the carrier signal according to the amplitude of the message signal. Frequency modulation frequency deviation bandwidth of fm. Most radio systems in the 20th century used frequency modulation fm or amplitude modulation am for radio broadcast. Fm has poorer spectral efficiency than some other modulation formats. Frequency modulation frequency deviation bandwidth of. Filtering is performed by a bank of gabor bandpass filters. Modulation, analog modulation, digital modulation, am,fm. Frequency modulation is widely used for fm radio broadcasting. Scientech techbook 2203 frequency modulation and demodulation techniques is a comprehensive learning solution specifically designed to study basic operation as well as to provide conceptual and step by step understanding of frequency modulation and demodulation techniques through observation of waveforms at various test points. Digital modulation can then be defined as the process. Frequency modulation is used in audio frequencies to synthesize sound. Amplitude modulation is mostly used in the form of electronic communication.
Amplitudeshift keying ask frequencyshift keying fsk phaseshift keying psk all of these techniques vary a parameter of a sinusoid to represent the information which we wish to send. This principle is at the heart of amplitude modulation. Its main advantage is that it is more resistant to additive noise than am. 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. Switch on am and fm simultaneously and observe the results. 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. Frequency modulation is that from of angle modulation in which the. It is also used in telemetry, radar, seismic prospecting, and monitoring newborns for seizures via eeg, twoway radio systems, music synthesis, magnetic taperecording systems and some videotransmission systems. A tutorial introduction to optical modulation techniques. Frequency modulation frequency modulation, the differences between am and angle modulation, the relationship between fm and pm, calculate modulation index, signal bandwidth, sideband frequencies and power levels, frequency spectra of an fm signal, fm transmitter, the differences between am and fm superheterodyne receivers, including capture. Linear modulation techniques vary the amplitude of a high frequency carrier. In the continuouswave modulation, a high frequency sine wave is used as a carrier wave.
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. 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. Ok, we now know that frequency modulation generates side bands, and that the modulators frequency determines where they lie. Amplitude modulation am frequency modulation fm phase modulation pm amplitude modulation. We begin our discussion of digital modulation by starting with the three basic types of digital modulation techniques. An introduction to frequency modulation sound on sound. As a result, most data transmission system use psk and qam. Amplitude modulation was developed in the beginning of the 20th century. It can be achieved in a number of ways, but the simplest uses a single diode rectifier circuit. But in frequency modulation the instantaneous angular frequency. Using amplitude modulation to shift the baseband signal fm radio 88mhz108 mhz.
Wide band fm first lets know about the frequency modulation 3. Modulation, analog modulation, digital modulation, am,fm,pm. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. The fhss modulation technique uses the available channels to transmit and receive data, but rather than staying on any one channel, it rapidly switches between channels using a pseudorandom pattern that is based on an initial key. Digital modulation and demodulation fsk,psk,bpsk,qpsk techniques. This video lecture discusses different types of modulation techniques. The am fm modulation model and a multiband analysisdemodulation scheme is applied to speech formant frequency and bandwidth tracking. Frequency modulation fm is the most popular analog modulation technique used in mobile communications systems. In particular, we discuss amplitude and frequency modulation. It was the earliest modulation technique used to transmit voice by radio.
Fm or frequency modulation is the process of varying the in instantaneous frequency of carrier signal accordingly with instantaneous amplitude of message signal. It is interesting, then, to find that am and narrowband fm produce similar changes in the frequency domain. What is fm, frequency modulation electronics notes. Modulation fm, amplitude shift keying ask, phase shift keying psk, etc. Phase modulation phase modulation is a change in the carrier phase angle. Amplitude modulation definition, types, solved examples. For recording the video signals by vcr systems, frequency modulation is used for intermediate frequencies.
In fm, the amplitude of the modulating carrier is kept constant while its frequency is varied by the modulating message signal. Depending upon the modulation techniques used, they are classified as shown in the following figure. Overview of fm modulation techniques modulator type short description advantages disadvantage block diagram key feature switched capacitor a chipinternal transistor is switched on and off by the modulating signal. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam. It explains what is modulation and classification of modulation. These modulation techniques are continuous wave modulation. Jul 30, 2019 amplitude modulation am frequency modulation fm phase modulation pm amplitude modulation. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. Dec 26, 2018 this ezed video explains frequency modulation.
There are essentially two basic methods of generating frequency modulated signals. Modulation and demodulation techniques request pdf. It is often called as am and is commonly used in transmitting a piece of information through a radio carrier wave. Learn about two techniques for recovering the baseband signal from a frequency modulated carrier. Frequency modulation offers improved performance over amplitude modulation, but it is somewhat more difficult to extract the original information from an fm waveform. Frequency modulation, fm frequency modulation has the advantage that it is possible to limit amplitude noise on the signal because it is only the frequency variations that carry the required information. In both cases a lowfrequency spectrum including the. Modulation techniques pwm and pulse code modulation. Frequency modulation is used in radios which is very common in our daily life. In the continuouswave modulation, a high frequency sine wave is used as a. This type of modulation technique is used in electronic communication. Frequency modulation techniques infineon technologies. Pdf modulation is an integral part of every modern communication systems and. Fm basics 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 carrier wave.
Nov 17, 2017 this video lecture discusses different types of modulation techniques. The typical frequency of the transmitted and received signal is. Frequency modulation fm is a form of modulation in which changes in the carrier wave frequency correspond directly to changes in the baseband signal. The bandwidth produced is a function of the highest. The application of the heterodyne principle to modulation is shown schematically in figure 143. Radio frequency rf modulation techniques basics dummies. Narrowband fm involves a limited modulating bandwidth and allows for easier analysis. To answer this, we must turn to the second attribute of the modulator its gain, a 2 and introduce a new concept called the modulation index, or simply. Fm produces multiple sideband frequencies above and below the carrier frequency. 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. Hence info is carried in the phase or frequency of the carrier.
The classical marconi radio used a modulation technique known today as. Am and fm timedomain waveforms for the same baseband and carrier signals look very different. What is frequency deviation, what is bandwidth of fm wave, carsons rule related videos 1. Change the modulation depth for 400 hz and 1 khz am and observe the results. Other methods of demodulating an am signal use synchronous techniques and provide. Amplitude and phase can be modulated simultaneously and separately. The first frequency modulation was invented by edwin howard armstrong in. Fm is considered an analog form of modulation because the baseband signal is typically an analog waveform without discrete, digital values. The amfm modulation model and a multiband analysisdemodulation scheme is applied to speech formant frequency and bandwidth tracking. The power efficiency is the ability of a modulation technique. However if st is sinusoidal, then the instantaneous frequency deviation of the anglemodulated signal is. Principles of communication modulation tutorialspoint. Frequency modulation and phase modulation are closely related. Each radio station is assigned 200 khz, to transmit a stereo audio.
Chapter 8 frequency modulationfm fm was invented and commercialized after am. Digital modulation is the process by which a sequence of pulses message of duration t is transformed into a sequence of sinusoidal waveforms, st of duration t. Change time base back to resolve carrier frequency and repeat last four points for fm modulation changing the maximal peak deviation in the range 0200khz. Thus, if mt is the message signal and ctacosw c t then fm signal will be. 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. Amplitude modulation is an increase or decrease of the carrier voltage ec, will all other factors remaining constant. 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. Amplitude modulation is a process by which the wave signal is transmitted by modulating the amplitude of the signal. Fm signal produced finally is proportional to concentration. Instantaneous frequency the instantaneousfrequencyof cos. Fm transmitter is the whole unit which takes the audio signal as an input and delivers fm modulated waves to the antenna as an output to be transmitted.
424 335 1020 471 918 8 140 76 459 1108 140 862 425 1447 990 500 709 509 786 357 299 780 517 222 632 33 503 741 531 504 1211