The simplest form of the pam modulator is an analog switch that is turned on and off at the rf carrier pulse rate. Frequency of the input carrier is fixed at constant amplitude of 1. Cme 312lab communication systems laboratory cme312 lab. Pulse amplitude modulation is the basic form of pulse modulation. Ece 4670 communication systems laboratory experiments manual spring 2010 mark a. It is still in use today in a variety of systems, including, of course, am broadcast radio. Demodulation output pcm operation with ac input modulation. Figure 7 labview vis that you need to complete the am modulation and demodulation block diagram below figure 8 completed am modulation and demodulation block diagram am demodulation. To generate amplitude modulated wave and determine the percentage modulation. Ee3 lab 1 amplitude modulation and demodulation broadcast analog television tv signals have a bandwidth of approximately 6mhz and this is achieved with a quadrature modulation.
C67 dsk implementation using cc for this part of the lab, you will demodulate the am signal generated by the arbitrary waveform generator on your lab bench. A demodulator is an electronic circuit that is mainly used to recover the information content from the modulated carrier wave. Carrier modulation allows the transmission of modulating frequencies without the use of transmission wire as a medium. Pulse amplitude modulation pam theory of and its applications. Before we study in detail about pam lets know the concepts of modulation. The purpose of this lab is for you to gain familiarity with the concepts of amplitude modulation and demodulation. By the end of this experiment, the student should be able to.
To perform the amplitude modulation and demodulation using am kit. Lab manual amplitude modulation and demodulation experiment 5 experiment 2 figure 5. This, for a sinewave, is equivalent to a phase reversal shift. The receivers used to listen to amdsbc are perhaps the simplest receivers of any radio modulation technique. Amplitude modulation and demodulation electrical and computer. Frequency division multiplexing, fdma amplitude modulation and demodulation. The second is to investigate classical analog amplitude modulation and the envelope detector. As before, this may require a manual adjustment of the voltsdiv and secdiv. Introduction in chapters 1 and 2 you studied how to apply intelligence modulation to an rfcarrier wave. Note that this is on the very low end of the recommended voltage range. The original waveform amplitude is quantized with a resulting loss of information. Analog communication lab manual, prepared by nakka.
If it is modulated by a hipolar hit stream according to the scheme illustrated in figure below, its polarity will be reversed every time the bit stream changes polarity. Ece 4670 communication systems laboratory experiments manual. The idea is simple, though the notion that it can be used to modulate signals for transmission was hardly obvious before its discovery. Restoring or recovering the message signal from the received modulated waveform that is generally corrupted by noise types of am detectors. The analog modulation part covers the generation and detection of doubleside band suppressed carrier dsbsc modulation, doubleside band with carrier also known as am modulation, quadrature amplitude modulation qam, and frequency modulation. Analog communications lab manual pdf ac lab manual pdf.
Pulse amplitude modulation pam is the simplest pulse modulation scheme. In pulse amplitude modulation system the amplitude of a carrier pulse train is varied in accordance with the instantaneous level of the modulating signal. Amplitude modulation is one of the earliest radio modulation techniques. Analog signal is characterized by the fact that its amplitude can take on any value over a continuous. Adjust the carrier and modulated signals for a modulation index of 0. Connections are made for the am modulator and demodulator as shown in the circuit diagrams. In amplitude modulation the amplitude of the carrier wave ct is varied linearly with the instantaneous amplitude of the message signal mt. Modulation allows us to transmit multiple signals in the same medium i. Each channel sharing scheme a set of basis vectors.
You must determine the analog filters passband edge frequency. In your lab write up compare this with what is expected for a modulation depth of m 1. Cme312 lab manual dsbsc modulation and demodulation experiment 6 experiment 2 dsb objectives. To study frequency modulation and determine its modulation factor 4. In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors. Students will explore the mathematical theory behind amplitude modulation and use the analog discovery 2 to visualize the effects of amplitude modulation in the time and frequency domains.
Build the simulink model of am modulator and demodulator figure7 explained in this manual. Demodulation is defined as extracting the original informationcarrying signal from a modulated carrier wave. This lab introduces students to communications theory with amplitude modulation and demodulation. As before, this may require a manual adjustment of the voltsdiv and secdiv to obtain a suitable waveform. The ideal envelope detector is a circuit which consists of two parts, the first part is a rectifier to take the absolute value of the signal, while the second part is lpf to remove unwanted component. There are different types of modulation and so are demodulators. Modulation is defined as the process by which some characteristics of a carrier signal is varied in accordance with a modulating signal. Describe phase demodulation circuit operation for the peak, lowpass filter, and conversion detectors. Demonstrate the modulation and demodulation process of dsbsc. Vestigial sideband amplitude modulation vsbam is a modulation that improves the spectral e. To demodulate the modulated wave using envelope detector. The digital modulation experiments include pcm encoding and decoding, line codes and digital. Experiment 2 experiment 6 experiment dsb sc modulation and. Dutton ee3 winter 2004 1 ee3 lab 1 amplitude modulation and demodulation 1 lab notes a word about power.
To study amplitude demodulation by linear diode detector 3. University of north carolina at charlotte department of. The standard form the amplitude modulated wave is defined as where carrier, modulating signal modulation index is defined as amplitude modulated signal. T12 measure the peaktopeak amplitude of the am signal, with m 1, and confirm that this magnitude is as predicted, knowing the signal levels into the multiplier, and its k factor. In this modulation, the signal is sampled at regular intervals and each sample is made proportional to the amplitude of the modulating signal. Now we will observe the demodulation of an am signal with the circuit shown in figure 87.
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