Ndirect and indirect method of fm generation pdf

Fm modulators and transmitters sonoma state university. Lec 30 principles of communication systemsi generation of narrowband fm signal iit kanpur duration. In this video, i have explained fm generation by direct method by following outlines. Therefore, the carrier frequency change at the adder output is 0. Direct method for generation of fm signal drawbacks. Wbfm using indirect method of armstrong heterodyned low freq.

Fm generation by direct method in analog communication by engineering funda duration. Hence a narrow band fm with small frequency deviation is transformed into a wide band fm with large frequency deviation. This video will help you to understand that which devices is used for generation of fm signals. Armstrong fm transmitter indirect method of modulation. Load flow is the procedure used for obtaining the steadystate voltages of electric power systems at fundamental frequency. In this video, i have explained fm generation by indirect method of armstrong by following outlines. These points out the major advantage of phase modulation pm, or indirect fm, over direct fm. Analog communication fm demodulators tutorialspoint. Block schematic of fm receivers, fm discriminators, preemphasis and deemphasis. Fm transmitter fm transmitter block diagram direct method. Explain the indirect method of fm generation or with the.

Indirect method consists of a nbfm modulator, frequency multipliers and frequency converters. Fm modulation system fm transmitter, reactance modulator. Explain armstrong method of fm generation with the help of. The frequency multiplier section, which features several frequency multipliers.

In this method, the carrier frequency is directly varied in. To obtain a frequency modulated signal via direct method 2. In this lesson, deepak has explained the concept for generation of fm signal using indirect method. In either case, the output of the transmitter is a frequency modulated wave, and the fm receiver cannot distinguish between them. The am with no carrier or dsbsc double sideband with suppressed carrier. The direct methods cannot be used for the broadcast applications. In this method the fm is obtained through phase modulation. This method of fm generation is direct because the oscillator frequency is varied directly by the modulating signal, and the magnitude of frequency change is proportional to the amplitude of the modulating signal voltage. In this lesson, deepak has explained the concept of generation of fm signal using direct method. That is the phase modulator is crystal controlled for frequency. The frequency of such an oscillator can be varied by an amount proportional to the magnitude of an input control voltage. M armstrong so this method is properly known as armstrong method.

If you continue browsing the site, you agree to the use of cookies on this website. Advantage and disadvantage of fm generation using indirect. To understand the process of frequency modulation by direct method background theory. In this video we will tell you about demodulation of fm slope and balanced slope detector. This method is called as the direct method because we are generating a wide band fm wave directly. Generation of fm signalsindirect method lecture notes. Fm generation uses all the advantages of digital circuitry resulting in improved carrier frequency stability, modulation linearity and. What is difference between direct and indirect generation. Frequency modulation is likely to play an important part in postwar radio. This section explains the indirect method of the fm generation in detail. As its name implies, an fm signal carries its information in its frequency variations. Fm generation by direct method in analog communication by engineering funda. Fm generation by direct method in analog communication by. In this method, frequency modulation is done by using a voltage controlled oscillator.

In direct method of fm generation, as the carrier generation is directly affected by the modulating signal, it is not easy to get high order stability in carrier frequency. Frequency modulation direct and indirect fm generation. In this method, voltage controlled oscillator vco is used to generate wbfm. Basically direct methods use the concept of a voltage controlled oscillator, so let us talk about direct methods first that. The principle of armstrongs method of phase modulation, or his frequency. Modulation i wideband fm wbfm now we determine the spectrum of the single tone fm signal for an. If a voltagecontrolled capacitor is placed in the feedback loop of an oscillator and the modulation signal is applied across this capacitor, then the oscillator will change in frequency and the resulting output signal is an fm signal. Fm demodulator circuits are found in any receiver that uses fm. Advantage and disadvantage of fm generation using indirect method ask for details. All that is needed is a linear voltagetofrequency converter. In direct method of fm generation armstrong method slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising.

Methods of generation of frequency modulation that do not depend on varying the frequency of an oscillator will be discussed under the heading indirect method. Fm signal generation they are two basic methods of generating frequency modulated signals direct method indirect method subscribe to view the full document. Direct fm involves varying the frequency of the carrier directly by the modulating input. Indirect method of generation of fm signal is also known as armstrong method. The exciter section contains the carrier oscillator, reactance modulator and the buffer amplifier. Here a crystal oscillator generates carrier signal, which provides very high stability compared to direct method. Slope detector can be constructed with the help of a tuned amplifier and an envelope detector. Indirect method of fm generation armstrong method learn. Pdf an efficient algorithm and its implementation for armstrongs. Fm fm generation by vco generation by vco generation by vco modules. A simplified diagram of a commercial fm transmitter using armstrongs method the final output is required to have a carrier frequency of 91.

Turbines can be propelled by wind or flowing water. There are essentially two basic methods of generating frequency modulated signals, namely, direct fm and indirect fm. The oscillator does not change frequency, as is the case of direct fm. Then, it multiplies and mixes this waves frequency properties to achieve the desired frequency deviation and carrier frequency. The indirect method of generating wbfm was first prepared by e. Communication is a process of transmission of information from source to destination or from transmitter to receiver. How can you use a varactor diode in the generation of fm. This video will help you to understand the generation of fm signals by using indirect method of frequency modulation or armstrong method. The block diagram of generation of wbfm wave is shown in the following figure. Fm generation by direct method in analog communication by engineering.

An efficient power flow solution looks for fast convergence, minimum usage of memory computationally efficient, and a numerically robust solution for all. In most fm radio bands, the lowest audio frequency is 50hz. A crystal oscillator can be used hence the frequency stability is very high. Armstrong method generates frequency modulated wave from a pulse modulated wave. The first method can be accomplished by the use of a reverse biased diode, since the. It has better frequency stability than other method such as reactance modulator as it uses crystal oscillators. Indirect fm involves directly altering the phase of the carrier based on the input this is actually a form of direct phase modulation. Modulation i lecture 7 wideband fm generation of fm signals. There are two types of fm modulators direct and indirect. Electric power systems an overview sciencedirect topics. Generation of frequency modulation varactor diode modulator. The modulating signal in the direct method has a direct effect on the frequency of the carrier. Direct and indirect methods of generation, mathematical analysis, modulation index, frequency spectrum and bandwidth requirement.

Demodulation of fm slope and balanced slope detector. This means, first we will generate nbfm wave and then with the help of frequency multipliers we will get wbfm wave. Direct fm modulation frequency of the carrier changes according to mt. Indirect fm is obtained by modulation of the phase of the carrier i. A very simple and direct method of generating an fm signal is by the use of a voltage controlled oscillator vco. The main methods of generating electricity have been discussed below. Direct modulation is usually accomplished by varying a capacitance in an lc oscillator or by changing the charging current applied to a capacitor. Direct fm f i f c k f m t in a direct fm system the instantaneous frequency is.

Fm modulation jie liang school of engineering science simon fraser university 1. In any radio that is designed to receive frequency modulated signals there is some form of fm demodulator or detector. This method is called as indirect method because we are generating a wide band fm wave indirectly. In the armstrong method of fm generation, the phase of the carrier is directly modulated in the combing network through summation, generating indirect. Analog communication fm demodulators in this chapter, let us discuss about the demodulators which demodulate the fm wave. Indirect fm generation first produces a narrowband relatively low bandwidthfrequency fm wave, often created using an integrator, a signal multiplier, a phase shifter, and a summer. Demodulation of fm is done by frequency discrimination method and phase discrimination method. Weekend projects super simple fm transmitter duration.