Single standard multimedia ifpll and fm radio demodulator. The baseband model of analog phaselocked loop and its linear theory were discussed on the lecture. The most useful of these is that it largely ignores fluctuations in the amplitude of the input fm wave. By the parallel interface, set the carrier frequency 2. Fm receiver design using programmable pll springerlink. Pll is widely used in wireless applications, such as am demodulator, fm demodulator, frequency selector and so on. Mar 20, 2015 the schematic diagram shows the connections of the cd4046b as an fm demodulator. Objectives of this lecture university of pittsburgh.
The increase or decrease in the frequency around the carrier frequency is termed as options. The most popular electronic method for fmpm demodulation is the phase locked loop. Pll demodulator for positive and negative video modulation. Definition of pll the phaselocked loop pll is a feedback system that may be used to extract a base band signal from a fm carrier, especially under low snr. This video covers the use of a 565 pll as a fm demodulator. The circuit shown below is of a pll fm stereo demodulator designed based on the an7415. Level implementation of binary fsk bfsk modulator and demodulator. Design and implementation of pll for frequency demodulation. Single standard vifpll demodulator and fmpll detector. Pdf design of a digital fm demodulator based on a 2nddegree. Conventional fm discriminators does not occur threshold improvement while fm demodulator using phaselocked loop pll improves threshold. The frequency modulator and demodulator structures are as explained below.
Njw2307 njw2307vc3 fm modulationdemodulation with pll. The function of the feedback loop around the vco is to adjust the phase of vco output so that it equals. Pll circuit track the input frequency by controlling a voltage input of a vco voltagecontrolled oscillator. Digital stereo radio dsp pll fm receiver module 87mhz or 76mhz 108mhz with serial control features. In the first model, you are provided a fm structure that is very similar to the theoretical background of this experiment.
Phase locked loop pll it is the best frequency demodulator. The fm demodulator baseband block demodulates a complex input signal and returns a real output signal. For our final design project, we designed a phaselocked loop circuit, implementing the 4046 ic chip. The fm modulator and demodulator are designed to satisfy the constraint for the application in personal wireless communication and digital audio broadcasting. Operation of forced monaural if muting or vco stopping by. The phase locked loop or pll fm demodulator operated because the loop was set to track the instantaneous frequency of the incoming fm signal. The block i was testing is the classic demodulator circuit using a pll, and a plain vainilla ic amp, as shown in the image. Our approach has been to combine several of these circuits onto an allinone. Implementation of fm demodulator algorithms on a high performance digital signal processor tms320c6711 dsp franz schnyder christoph haller. In this paper, we explore the design of a digital fm receiver using the approach of an alldigital phase lockedloop adpll. The input is a passband representation of the modulated signal.
Design of a digital fm demodulator based on a 2nddegree order alldigital phaselocked loop. Pdf fm modulation refers to the process of modulating a carrier wave with respect to the input message signal. A phase locked loop can be an fm modulator, an fm demodulator, and it can be an integral part of an am demodulator, where it derives the carrier frequency with great stability and is heterodyned with the rf. Tda8296 digital global standard low if demodulator for analog tv. The phase locked loop pll as a demodulator is studied in the experiment entitled fm demodulation and the pll in this volume. Features wide supply voltage range down to low supply voltage.
Pll is a kind of automatic tracking system, which is able to detect the input signal frequency and phase. The amplifier also functions as the low pass filter. Fm radio receiver with digital demodulation a senior project. Two of them mixed and pll demodulator are are implemented on the dsp tms320c6711dsk.
I searched for the working principle of this demodulator but there is one thing i couldnt understand and i couldnt find an answer to. Phase locked loop, pll fm demodulator or detector is a form of fm demodulator that has gained widespread acceptance in recent years. Fsk demodulator with pll 15 msc in electronic technologies and communications digital communications systems practice 5. The internal block diagram shows that ic 565 pll consists of phase detector, vco, and amplifier. Pll lm565 the lm565 is a general purpose phase locked loop pll containing a stable. Recovery of carrier by phaselocked loop pll pll note.
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 architecture i am trying to use is pllbased fm demodulator like the one below. Phase comparator i is used for this application because a pll system with a center frequency equal to the fm carrier frequency is needed. To look at the operation of the pll fm demodulator take the condition where no modulation is applied and the carrier is in the centre position of the passband the voltage on the tune line to the vco is set to the mid position. Both the input and output signals are real scalar signals. Objectives to study the operation of a pll and its application to demodulate a fsk signal. This is why pll can be used to demodulate fm signal. Objectives of this lecture define and mathematically describe angle modulation explain the difference between fm and pm describe fm and pm waveforms define frequency deviation and modulation index frequency analysis of an fm waveform determine the bw requirements explain the fm modulatordemodulator.
This schematic is essentially identical to many examples that appear on the web and app notes. It is a high performance fm detector due to its key advantages such as linearity and low manufacturing costs. Pdf pll based high frequency fm modulator researchgate. La72912v fm modulator and demodulator ic overview the la72912v is a fm modulation and demodulation singlechip ic. In addition to audio signal, it can also be used in data pulse. For the sake of simplicity, ka 1 and ar ac have been chosen lowpass. The phaselocked loop pll circuit is widely used in communication and control systems.
Pll circuits can demodulate an fm frequency, multiply frequencies, synchronize processor clocks, and a host of other things. The fm demodulator passband block demodulates a signal that was modulated using frequency modulation. Wave soldering is a joining technology in which the joints are made by. May 25, 2018 this video covers the use of a 565 pll as a fm demodulator.
In digital fm receiver, pll is the main part to capture and lock the signals at different. Capture, lock, and hold frequencies are discussed and calculated as well as the testing of the circuit on a breadboard. There is no way i know of that it can be used to create the am sideband ie, vary the carrier frequency amplitude to do what you want. Experiment a suitable setup for measuring some properties of a vco is illustrated in figure 2. May 29, 2017 the research article presents the design of different components of fm receiver. Pll fm multiplex stereo demodulator datasheet catalog. The input fm signal and the output of the vco is applied to the phase detector circuit.
Xr2212 is a highly stable, monolithic pll phase locked loop ic specifically designed for communication and control system applications. Functions ask modulation and demodulation video signal fm. In this paper, pll fm detectors were designed from the pll integrated circuits where the frequency demodulation was obtained directly from the pll circuit by taking the center frequency of the pll todesign the fm carrier frequency. Pdf fm modulation refers to the process of modulating a carrier wave with. Nov 26, 2012 simple phase locked loop application demo duration.
C4 and c5 are the dc decoupling capacitors for the left and right output channels. Dutton ee3 winter 2004 3 3 fm demodulation using the pll now that youve seen how the pll tracks a signal, we will explore one of its applications, fm demodulation. Simple phase locked loop application demo duration. The combination results in a phase lock, where the pll circuit matches the phase and frequency of the input signal. A rough idea of how a phase lock loop can demodulate an fm signal follow. The la3361, pll fm multiplex stereo demodulator, is designed for low supply voltageuse appliance such as portable radio or car stereo. In all pll applications, the phaselocked condition must be achieved and maintained.
If the message was a single tone, from its amplitude can you estimate the frequency deviation of the fm. A noncoherent detector has only one input, namely, the modulated signal port. In order to avoid distortion, many applications require operation in the linear region, that is, the total variance of the phase. You will model the pll, and recover the message from the fm signal. Fm demodulator circuits are found in any receiver that uses fm. Pll or phase locked loop is used as a fm demodulator. The lm565 is a general purpose phase locked loop pll containing a stable, highly linear voltage controlled oscillator vco and a double balanced phase detector with good carrier suppression. Introduction to fm using a vco vol a2, ch 10, rev 1. Since the vco is controlled to follow the input frequency, then the controlling signal is directly proportional to the modulating signal. To keep the loop in lock, the voltage controlled oscillator within the loop needed to track the frequency of the incoming signal.
The second section will be the design of the fm radio front end. This device can be used in several kinds of applications. Why do we need this feedback to the nco dt in the diagram. Fm demodulator am demodulator fm receiver am receiver correct answer. The total fm signal amplitude is 500 mv, therefore, the signal must be ac coupled to the signal input terminal 14. Fm demodulation with the pll a2 143 t5 measure the properties of each element of the pll, and then predict some of its properties as a demodulator. Njw2307 is a fm modulation demodulation ic for audio signal in full duplex communication that operates from 3. Implementation of fm demodulator algorithms on a high. This means that the pll fm demodulator tends to ignore any unwanted interference which. In a pll, the dbm is used in combination with a low pass filter. A new highperformance digital fm modulator and a digital phaselocked loopbased fm demodulator have been proposed in this paper.
Operation of forced monaural if muting or vco stopping by only one pin. A typical pll circuit consists of three main components. In any radio that is designed to receive frequency modulated signals there is some form of fm demodulator or detector. Pdf design of a digital fm demodulator based on a 2ndorder all. Fm demodulator using a 4046 pll electronics forum circuits. Since the vco output tracks the fm signal, and the vco input voltage is proportional to the vco output frequency, then the vco input will be equal to the demodulated signal. The design approach is based on digital components rather than analog components such as phase detector, loop filter and voltage controlled oscillator. The demodulator contains a carrier recovery circuit its output is the recovered carrier. Led d1 is an indicator led and r1 is its current limiting resistor. A pll system can be used to implement an fm demodulator.
The phase lock loop demodulator is designed in the digital. When the input signal frequency increases, the output signal voltage decreases. The technique used to design the fm demodulator is the phase locked loop. Building simulink model for music transmission using fm modulator and demodulator baseband here, we will implement the fm modulator and demodulator using a music file as a source. A simple pll fm demodulator circuit using ic xr2212 is shown here. Because both algorithms demand the same pre and after signal preparation, the demodulation is split into sub projects to reach a high compatibility between the algorithms. In figure b, notice that pll ic consists of two power supply pins marked vcc. Its adjustment free modulationdemodulation circuit significantly reduces the number of peripheral circuits required and can contribute to lower production costs. Restoring or recovering the message signal from the received. A phaselocked loop pll is an electronic circuit with a voltage or currentdriven oscillator that is constantly adjusted to match in phase and thus lock on with the frequency of an input signal. In telecommunications and signal processing, frequency modulation fm is encoding. The architecture i am trying to use is pll based fm demodulator like the one below.
Pll fm detectors can easily be made from the variety of phase locked loop integrated circuits that are available, and as a result, pll fm demodulators are found in many types of radio equipment ranging from. This means that the pll fm demodulator tends to ignore any unwanted interference which appears alongside the input signal. The most popular electronic method for fmpm demodulation is the phase locked loop pll. Pll fm demodulator block diagram the working of a pll fm demodulator is very easy to understand. C1 is the input coupling capacitor which blocks any dc voltage present in the multiplexed input signal. Since there is a significant source of ir noise at around 40 to 70 khz, i decided to go for a higher center frequency of 120 khz. In this case, since the source is a multimedia file rather than a pure sine wave, we need dsp processing, which is resampling and filtering. The design approach is to design the fm demodulator as if it were an analog phase lock loop. The research article presents the design of different components of fm receiver. The use of the quadrature detector andor the phaselocked loop for fm demodulation is also considered. When a pll is locked on an fm signal, the vco tracks the instantaneous frequency of that signal. Pll phase locked loop can be used to make a fm demodulator. Jun 29, 2014 the block i was testing is the classic demodulator circuit using a pll, and a plain vainilla ic amp, as shown in the image. Digital stereo radio dsp pll fm receiver module 87mhz or.
1447 1248 434 750 12 307 1434 140 1187 489 584 1645 1227 1231 1151 1119 1133 1591 1559 268 1609 1266 1129 934 803 1152 109 220 1446 440 1162 400 735 1354 733 786 1342 5 1280 1084