One approach to reduce this interference, known as frequencydivision multiplexing, allocates different carrier frequencies to different users or for dif. Pam modulation and demodulation abstract this project proposes a bjtbased modulation and demodulation circuit which helps us transmit signals from transmitter to receiver. Pulse position modulated ppm ground receiver design for. The performance can be varied by varying the width of the pulses. Demodulation is defined as extracting the original informationcarrying signal from a modulated carrier wave. So can have amplitude modulation am frequency modulation fm phase modulation pm frequency and phase combined are known as angle modulation 8. In this pulse position modulation system, the amplitude and width of pulses is kept constant, while the position of each pulse, in relation to the position of a recurrent reference pulse, is varied by each instantaneous sampled value of the modulating wave. Manufacturer of basic communication trainer amplitude modulation demodulation trainer, frequency modulation demodulation trainer, ppm modulation demodulation trainer and tdm modulation demodulation trainer offered by kitek technologies private limited, mumbai, maharashtra. The ppm can be demodulated both synchronously and asynchronously.
Telecommunications pulse modulation and sampling pam. Digital modulation and demodulation fsk,psk,bpsk,qpsk techniques. More particularly, the present invention relates to a ppm demodulation device used in the field of optical communication for demodulating reception data that is subjected to pulseposition modulation ppm with a pulse signal inserted into a predetermined symbol position. Pam ppm pwm modulation demodulation trainer kit is used to study sampling, pulse modulation demodulation and signal reconstruction process. The modulation and demodulation waveforms of pwm and ppm signals are shown in fig8. First, just consider a simple example of throwing a paper for a much far distancecould u do that with ease. The present invention relates to ppm demodulation devices. Jun 17, 2014 introduction to modulation and demodulation 1. Frequency modulation fm frequency modulation is the process of varying the frequency of a carrier wave in proportion to the amplitude of a baseband signal. This is the technique called pulse width modulation pwm which is in use since a long time for controlling motor speed and other similar inertial machineries. Demodulation is extracting the original informationbearing signal from a carrier wave. It is another type of ptm, where the amplitude and width of the pulses are kept constant and only. The amplitude modulation am modulation index can be defined as the ratio of the peak value of the message signal to the amplitude.
Ppm pulse position modulation basics, circuit, working. The signal output from a demodulator may represent sound an. The ramp will attain different heights in each cycle since the widths are different and the heights attained are directly proportional to the pulse width and in turn the amplitude of the message signal. Dpsk, and pulse position modulation ppm optical waveforms at 2. Modulation and demodulation of pulse position modulation with. To study and perform pulse amplitude modulation and demodulation. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors. Note, when a modulator is set up, v dc is fixed at a particular value. Eee2009eee2009 communicationscommunications contents introduction to communication systems analogue modulation am, dsbsc, vsb, ssb, fm, pm, narrow band fm, pll demodulators, and fll loops sampling systems time and frequency division multiplexing systems, nyquist principle, pam, ppm. Explain generation and demodulation of pam, ppm and pwm with waveforms. This method is widely used for optical communication systems such as optic fiber and ir remote controls, where efficiency is required and little or no external interference occurs.
Aug 06, 2018 in this video, i have explained ppm pulse position modulation by following outlines. Dec 05, 2014 types of modulation sine wave carrier described by 3 parameters. Ppm, pm and dm are actually baseband digital signal coding and. However, pam, pwm, and ppm modulations are similar to am. Fm demodulation using pll in fm modulation when the bandwidth becomes so large that the input noise power is relatively large, the performance of the fm system degrades rapidly and the system exhibits a threshold. Using a sine waveform there are three parameters which we can use to modulate a message onto the carrier. Vectors and modulation cse 466 interfacing 3 spose m and n are orthogonal unit vectors. The circuit designed is simple, easy to understand and implement. It is this process that is called demodulation or detection. The modulation techniques are classified into two major types. The learning material provides exhaustive technology details and experimental assistance. We have discussed previously the different types of modulation techniques, let us understand the basic difference between pam, pwm, and ppm. To study and perform pulse position 6 to study and perform pulse code modulation and demodulation. A modulation technique that allows variation in the position of the pulses according to the amplitude of the sampled modulating signal is known as pulse position modulation ppm.
Direct detection receiver and the helstrom bound mary ppm encodes digital data by positioning a. Explain generation and demodulation of pam, ppm and pwm with. Explain generation and demodulation of pam, ppm and pwm. A demodulator is an electronic circuit or computer program in a softwaredefined radio that is used to recover the information content from the modulated carrier wave. By varying the amplitude of the pulses the carrier signal in proportion to the instantaneous values of the analog signal the message. The task of the receiver is to discriminate between the m possible received ppm symbols with the. Pamppmpwm modulation demodulation techniques scientech 2110 scientech technologies pvt. In analog modulation technique, if the amplitude or duration or position of a pulse is varied in accordance with the instantaneous values of the baseband modulating signal, then such a technique is called as pulse amplitude modulation pam or pulse durationwidth modulation pdmpwm, or pulse position modulation ppm. In the following illustrations we will have a fixed message, v m cos m t and vary v dc to obtain different types of double sideband modulation. The term detection is the older term dating back to the early days of radio. It is very easy to convert the pwm wave to a ppm wave, and for the ppm wave the demodulation circuitry is extremely simple. The type of modulation is determined by the modulation depth, which for a fixed mt depends on the dc offset, v dc.
Then inner products dot products are 1 1 0 can interpret inner product as projection of vector 1 v1 onto vector 2 v2in other words, inner product of v1 and v2 tells us how much of vector 1 is there in the direction of vector 2. A burst power when used other than the continuous power can save the total power supplied to an inertial load while achieving the same performance from the device. Jun 14, 2017 for the love of physics walter lewin may 16, 2011 duration. Laboratory manual principles of communication system lab ee226f ivth semester prepared by. Describe phase demodulation circuit operation for the peak, lowpass filter, and conversion detectors.
It is another type of ptm, where the amplitude and width of the pulses are kept constant and only the position of the pulses is varied. Modulation and demodulation of pulse position modulation. When expressed as a percentage it is the same as the depth of modulation. For the love of physics walter lewin may 16, 2011 duration. The changes in the carrier signal are chosen from a finite number of m alternative symbols the modulation alphabet. Introduction what is communication transmitter channel receiver a communication system process of conveying message or information transmitter modifies the message signal into a form which is suitable for transmission over channel which is achieved by modulation information source. But the term demodulation tends to be used more widely when referring to the process of extracting the modulation from the signal. Modulation techniques pwm and pulse code modulation. A demodulator is an electronic circuit that is mainly used to recover the information content from the modulated carrier wave.
In practice, problems arise in baseband transmissions. Digital modulation methods can be considered as digitaltoanalog conversion and the corresponding demodulation or detection as analogtodigital conversion. Modulation and demodulation medium, it would be dif. Pam, pwm, and ppm modulations belong to analog modulation and the pcm modulation belongs to the digital modulation. Analog communication pulse modulation tutorialspoint.
The obtained simulation and experimental results confirm well with the given analysis. Storage oscilloscope is desired for satisfactory observation of pcm wave forms 4. The idea is hence to convert the pwm wave to the ppm wave and then demodulate it. Introduction in chapters 1 and 2 you studied how to apply intelligence modulation to an rfcarrier wave. This chapter describes the essential principles behind.
Introduction to modulation and demodulation the purpose of a communication system is to transfer information from a source to a destination. The proposed scheme is examined by using computer simulation and experiment. After firing there is a recovery time during which the laser cannot be fired. But if u use a stone or any other object to wind the paper, then the paper reaches more t. Transmitter and receiver are simple in amplitude modulation. Analog signal such as voice or music is converted to discrete samples and then quantized to bits. Difference between pam, pwm, and ppm comparison of pwm and pam. Amplitude modulation early radio ee 442 spring semester. Pulse duration modulation pdm or pulse width modulation pwm. When input noise power is quite large we would be inclined to use fm and allows a sacrifice of bandwidth for the sake of improved. In digital modulation, an analog carrier signal is modulated by a discrete signal. Carrier modulation allows the transmission of modulating frequencies without the use of transmission wire as a medium. It is deserved to pay attention that pcm modulation is a real digital signal that can be processed and stored by computer.
We show that each technique is advantageous depending on the desired. Ee4512 analog and digital communications chapter 6 chapter 6 analog modulation and demodulation amplitude modulation pages 306309. Pulse position modulation ppm is an analog modulation scheme in which, the amplitude and the width of the pulses are kept constant, while the position of each pulse, with reference to the position of a reference pulse varies according to the instantaneous sampled value of the message signal. To study and perform pulse width modulation and demodulation. Aug 15, 2001 figure 2 schematic representation of the ppm timing scheme, t, represents the slot width, td is dead time the minimum time required for a qswitch laser to build up energy prior to emitting a pulse, m is the alphabet size and t, is a ppm word time. Pwm and ppm are used in few instances in communications systems, usually for military purpose. Ee4512 analog and digital communications chapter 6 the dsbsc am coherent receiver has a bandpass filter centered at f c and with a bandwidth of twice the bandwidth of st because of the lsb and usb. Ppm may be obtained very simply from pwm, as shown in. If the received carrier phase is assumed to be constant, each of the seven reference values will have to be shifted only once at the beginning of the simulation. Once the signal has been received, filtered and amplified, it is necessary to recover the original modulation from the carrier. Modulation is defined as the process of transmission of information such as images or videos on an electrical signal.
The pulse position modulation ppm can be actually easily generated from a pwm waveform which has been modulated according to the input signal waveform. Each channel sharing scheme a set of basis vectors. This is repeated every t seconds, such that the transmitted bit rate is bits per second. Demodulation is defined as the process of extracting this information. There are different types of modulation and so are demodulators. When we take a demodulation unit of am receiver, it consists of rc filter and a diode which will demodulate the message signal or modulating signal from modulated am signal, which is unlike in frequency modulation. To study and perform frequency modulation and demodulation. This paper presents the modulation and demodulation of pulse position modulation with carrier. Describe fm demodulation circuit operation for the phaseshift and gatedbeam discriminators and the ratiodetector demodulator. As mentioned above, ppm modulation consists of mapping each sequence of l databits into one of m 2l slotlocations according to a predetermined lookup table, and firing the laser so as to place the optical pulse in the correct slot relative to the previous pulse. Digital baseband modulation schemes baseband modulation is done before the information bits is sent out using a carrier signal popular methods for high datarate are, pcm. The ppmwc signal is generated by summing the ppm signal and the pll reference signal. Pulse position modulationppm advantages disadvantage. Each symbol may be separated from the next by t d 0 seconds.
Pulse position modulation for digital modulation pdm. The synchronous demodulation is complex as it requires synchronization of the receiver with the transmitter. The amplitude of the carrier remains constant phase modulation pm another form of analog modulation technique which we will not discuss. Pammodulationanddemodulation mini projects electronics. Pulseposition modulation ppm is a form of signal modulation in which m message bits are encoded by transmitting a single pulse in one of possible required time shifts. Eee2009eee2009 communicationscommunications contents introduction to communication systems analogue modulation am, dsbsc, vsb, ssb, fm, pm, narrow band fm, pll demodulators, and fll loops sampling systems time and frequency division multiplexing systems, nyquist principle, pam, ppm, and pwm. Modulation is the process of impressing a lowfrequency information signal baseband signal onto a higher frequency carrier signal modulation is done to bring information signals up to. In this video, i have explained ppm pulse position modulation by following outlines. Pulseposition modulation ppm is a signal modulation used for both analog and digital signal transmissions. Fm demodulation is a key process in the reception of a frequency modulated signal. Before going to discuss the difference between pam, pwm, and ppm, let us discuss individually each.
It is primarily useful for optical communications systems, which tend to have little or no multipath interference. Terms like diode detector, synchronous detector and product detector are widely used. The pulse position modulation ppm is a modulation technique designed to achieve the goals like simple transmitter and receiver circuitry, noise performance, constant bandwidth and the power efficiency and constant transmitter power. This is the technique called pulse width modulation pwm. Modulation is a technique in which message signal is transmitted to the receiver with the help of carrier signal. There are many types of modulation so there are many types of demodulators.
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