Engineering, Polytechnic and Vocational Training Equipment-> Digital Communication Trainers

[1] 2 [ Next»]   Click to Enlarge ANALOG SIGNAL SAMPLING CIRCUIT. MODEL IBL-DCT ?1 The purpose of the Analog Signal Sampling Circuit is to illustrate how an input signal can be transformed into a series of samples. The trainer also provides a Sample/Hold output in addition to Sampled output so that comparison can be drawn between the two outputs. This enables the student to study the effect of different sampling frequencies on the waves. An Oscilloscope is an important requisite to observe the outputs. The board contains an analog switch, which performs the Sampling and Hold operations. This instrument has Signal Conditioner, Analog Switch and Unity gain buffer amplifier, Pulse generator suitable for generating Time division signal, sample and hold amplifier and necessary power supplies, as part of the experimenter. Two external message signals must be provided as input of two different channels, for possible reconstruction. These signals can be either from any function generator of 1KHz, or from any other source. See Enlarge Click to Enlarge SIGNAL RECONSTRUCTOR TRAINER. MODEL IBL-DCT?2 Signal reconstruction by the very name suggests that the received signal is not in the form that can be used directly. This can be for several reasons. In this trainer it is attempted to acquire the data from Analog Signal Sampling Circuit Trainer Model DCT-1 as signal source, to this experimental module. The signal reconstruction in this module is accomplished by the use of filters. This has necessary hardware to experiment and study the process of reconstruction. The experimental procedure consists of connecting the respective blocks using 22SWG wire patch cords. An external dual beam oscilloscope is required to view waveforms at different points on the trainer. See Enlarge Click to Enlarge TIME DIVISION MULTIPLEXER TRAINER. MODEL IBL-TDM?1 The Time Division Multiplexing (TDM) is a method to use the same transmitting channel to transmit messages coming from different sources as its input. The number of message channels that a TDM system can handle successfully depends on the cycle frequency of the TDM switcher. In order to have loss-less transmission of all the messages, the switching frequency of the TDM system, must be much higher switching frequency than, any of the message signal frequencies. This illustrates how time division multiplexing takes place. This TDM trainer can handle two message channels. This trainer has built in pulse generator, which is used as TDM switch for time division multiplexing. Two different message signals must be connected as input to this TDM trainer from external function generator of 1 KHz. The message signals can be SINE, SQUARE, RAMP etc. An external oscilloscope is an important requisite for the experiment. This trainer has blocks consisting of clock generator, Channel selector, time division multiplexer, in addition to built-in power supplies. The necessary connections are established using 22SWG wire patch-cords. See Enlarge Click to Enlarge 8 BIT MAGNITUDE COMPARATOR. MODEL IBL-DMC-1 Magnitude comparator trainer is intended to study the comparison between two binary number systems. It is used to determine the weight-age of two binary numbers and decide which number is (a) equal = (b) less than < or (c) greater than > the other number. This is an important concept that is used extensively in digital communications systems. This comparison is analogues to determine which car is running faster than the other or which is cheaper than the other etc. Of-course one has to decide this after due consideration of comparing other operating parameters also. The application of magnitude comparison is very wide in nature and the limit is only imagination and innovation. For example, the result of such a comparison is used to set the duty cycle of a clock signal that is used to generate synchronization signal. Therefore it is necessary to understand what this magnitude comparator is all about. The scope of this trainer restricts itself in experimenting to find out upto the comparisons only. This trainer uses 8-bit magnitude comparator as basic building block. The necessary signal generation is accomplished by using switches as inputs and LEDs as output indicators. This trainer uses two sets of BCD thumbwheel switches as inputs. One set of two (the first switch in units position, the other in tens position) switches-A, act as a comparing input while the other set of two switches-B, as compared number. There by allowing you to set numbers in the range of 0 to 9910, as inputs to the comparator. There are two numbers of 4 bit magnitude comparators, with a provision to cascade the outputs of first block with the inputs of next block, thus allowing you to make an 8bit comparator system. This trainer has other associated electronics also as part of the experimental setup. See Enlarge Click to Enlarge LINE CODING DEMONSTRATOR. MODEL IBL-DCT-3 Line coding demonstrator is intended to demonstrate the principles of LINE CODING. In digital transmission of data, over wire or optical fiber systems, the digital data is transmitted in binary form after proper signal conditioning. The data so transmitted must be securely received, at the intended receiving station. In order to accomplish this function, several schemes are designed and adopted. One such a scheme is called as LINE CODING. There are many methods in line-coding formats. Each one of the methods offers one or more of the following advantages over the other. For example, (a) the line coding is used in telephone line applications for spectrum shaping. (b) This is also used to recover bit clock for synchronization with the received signals. (c) To eliminate DC component, that is likely to accompany with the received signal, which otherwise introduce base line wandering. (d) To increase the bandwidth, of transmitted data, compared to other schemes. Using this trainer the student can observe waveform of a selected scheme as described below, using an oscilloscope. The schemes available on this trainer are: a. Unipolar Non Return Zero (NRZ) b. Unipolar Return Zero (RZ) c. Polar Non Return Zero d. Polar Return Zero e. Bi-Polar Non Return Zero and f. Bi-Polar Return Zero. In order to accomplish this the trainer has a built in sequence generator, and necessary building blocks for conducting one of the above schemes. It is necessary to connect an external square wave generator as input to the sequence generator with at-least 100KHz at TTL levels. This instrument has built-in power supply. See Enlarge Click to Enlarge AMPLITUDE MODULATION / DE-MODULATION (AM) TRAINER. MODEL IBL-AMD-1 Amplitude modulation is method of transmitting analog signals, usually voice (intelligence) frequency on a high frequency carrier wave. Changing the modulation index varies the amplitude modulation. In this trainer has all the means to achieve this. This trainer consists of both transmitter and receiver. While the carrier wave is internally generated, the voice signal or output of sine generator is usually used as input signals for transmission purposes. This trainer has suitable microphone input, and signal conditioner. At the output it has an audio power amplifier and speaker to receive the demodulated signals. An optional 1 KHz function generator with 1 V PP amplitude, and a dual beam oscilloscope is immensely useful to view the waveforms at different stages of modulation and demodulation. See Enlarge Click to Enlarge FREQUENCY MODULATION / DE-MODULATION (FM) TRAINER. MODEL IBL-FMD-1 Frequency modulation is by far the most important communication means. This finds an application in transmitting systems. This is preferred, because of its ability to eliminate associated noise, there by providing high fidelity in the audio at the receiving end. This trainer is to understand the concept of generating a FM signal for further analysis. This trainer requires a modulating signal, often called as message signal. This can be a SINE wave generated by an external audio generator as one input. The carrier wave is generated by the internal electronics in the trainer itself. By using an external Oscilloscope the FM wave can be observed at its output terminals. This has a built-in demodulation setup, which reconstructs the message signal and is available for observation. You can use this trainer to measure the modulation index. See Enlarge Click to Enlarge PULSE CODE MODULATION / DE-MODULATION (PCM) TRAINER. MODEL IBL-PCM-1 This trainer is same as Fiber Optic Pulse code modulation trainer Model FOT-7. The only difference in PCM-1 is that a connecting patch cord is used instead of Fiber Optic cable. Otherwise it is the same as FOT-7. The purpose of this trainer Model PCM-1 is to introduce you to the Pulse Code Modulation (PCM) and demodulation technique. A multimode Fiber Optic cable is used for data transmission and reception. In this trainer, you will understand and investigate the following processes. All the major blocks of this trainer are designed from fundamental building blocks instead of using a dedicated CODEC. As a result, all the blocks of CODEC are dissected and are available as separate building blocks for study. This facilitates the student to understand the quantization process and view the quantified and encoded data using 8 bit LED displays at the transmission side. Observe the serial transmission and reception of this quantified decoded data at a test point, observe the decoded 8 bit received data on LED display etc. This data is further reconstructed and the original signal is available at an output terminal for analysis. As a result of this design, the student can see various stages of the PCM transmission and reception processes for himself. Features of PCM blocks are Digitization of an analog signal, Observe the quantization (encoding) of incoming signal, Measurement of quantization noise, Serialization of quantized signal for onward transmission, Serial data capture, Decoding of quantified signal, Observation of received signal, Reconstruction of received signal, and Study of aliasing. In order to achieve the above, the trainer has necessary built in input signal sources. a) Continuously variable analog input in the range of 0 to 5 VDC, b) Function generator with Sine, and Square wave inputs in the range of 200Hz to 20KHz c) Microphone input after proper signal conditioning, for voice transmission and d) Provision to connect an external signal source. The output of the transmitted and received signals, decoded signal and finally the reconstructed outputs can be observed on the oscilloscope. In order to observe the sequence of events taking place, there are two types of clocks provided, one operating at 200KHz, the other at 1Hz. During slow clocking it is possible to observe the signal flow at various test points as detailed below. a) Quantization process b) Serial transmission c) Decoded output and d) Reconstructed output. e) A power amplifier with speaker to hear the voice reception ( when sampled at 200KHz) This trainer comes with completely self-contained systems with built-in power supplies, signal sources, input output test points for signal observations, a microphone with proper signal condition, a power amplifier with speaker etc. This requires an optional external Dual beam oscilloscope to observe the PCM signal transmission at different stages of modulation and demodulation processes. Specifications: Input sources: 1. Built-in Function generator with SINE, and SQUARE waveforms. 2. Frequency: Variable frequency of 200Hz to 2KHz 3. Amplitude: Variable in the range of 0 to 5 Volts 4. Continuously variable DC source : 0 to 5V DC 5. Provision for connecting external signal source Output: 1. 8 bit LEDs to display Quantized data 2. 8 bit LEDs to display decoded data 3. Power amplifier with speaker 4. Frame timing LED to display clock signal 5. Synchronizing signal LED Built-in power supplies. All the above are available in an ergonomically designed cabinet. See Enlarge Click to Enlarge PULSE WIDTH / POSITION / AMPLITUDE MODULATION TRAINER. MODEL IBL-PUL-1 PWM: Pulse Width Modulation is the process of modulating an analog signal usually voice frequency in the form of variation of pulse width proportional to the voice (or signal) amplitude. The voice frequency is modulated on an internally generated carrier wave. The reconstruction process of this wave is by demodulating and original voice signal is recovered. This trainer requires an external function generator with 1 KHz frequency and 1 V P toP signal strength. Using a dual beam oscilloscope it is possible to observe the input signal, modulating signal and demodulating signals. PAM: Pulse amplitude modulation is a type of modulation is used as the first step in converting an analog signal to a discrete signal or in cases where it may be difficult to change the frequency or phase of the carrier. In this case the carrier is a pulse train rather than a sine wave and the spectrum of the carrier consists of several components at nwc = 2np/T where T is the time between pulses. Using this trainer it is possible to observe the modulated PAM signal and demodulated message signals on the Oscilloscope. It is necessary to study the effect of sampling pulse duration, sampling rate on the PAM signal and on the demodulated signal. Be sure to reduce your sampling frequency such that your sampling frequency is below Nyquist rate. PPM: Pulse position modulation makes use of PWM signal generated during PWM setup as input for modulation purposes. This is a 3 in 1-modulation trainer. This trainer is intended to study the basic principles of Pulse Modulation techniques. This provides a unique opportunity to construct a complete modulation setup required in a communication system. This can be best studied and experimented in the audio range. This requires two independent external function generators as necessary sources for generating carrier and signal. This trainer has all the necessary active and passive components required to perform the experiments, and built-in power supply. The output waveforms can be monitored on an external CRO. You need an external function generator, a pulse generator operating in the range of 100 Hz to 100KHz, and an Oscilloscope for observing the waveforms. See Enlarge Click to Enlarge DELTA MODULATION / DEMODULATION TRAINER . MODEL IBL-DMD-1 Delta modulation is the process of converting the message signal x(t) in 1-bit (two level) quantizer form, ie; ? ?. The correlation between the adjacent signals is increased purposely. In this way the prediction, there by the quantization error can me small. Using this trainer it is possible to study modulated step size ? at the integrator output and compare with the calculated value. It is possible to compare the message signal and integrator output and analysis can be made on this observation. It is possible to observe the occurrence of granular noise, and slope overload noise as a function of variable parameter. The following responses can be observed for the above functions, by varying the Message amplitude. By varying the sampling frequency. By using a total harmonic distortion (TDH) analyzer it is possible to measure the % of harmonic distortion. It is also possible to plot the THD by measuring the message signal frequency fc, Amplitude fa, ? step size, and the sampling frequency fs. This instrument requires an external function generator in the rang eof 100 to 10KHz with PtoP amplitude of 8V, a dual beam Oscilloscope, an true RMS voltmeter. See Enlarge Click to Enlarge FSK MODULATION / DE-MODULATION (FSKM) TRAINER. MODEL IBL-FSK-1 Frequency shift keying (FSK) is a form of FM that, with minor exceptions. The modulating signal is a digital voltage (code 1?s and 0?s) that will key the carrier to shift between only two distinct, fixed frequencies. In this case, the low frequency represents a digital 1(mark), and the higher carrier frequency is a 0 (space). The second variation from standard is that the carrier is not much higher in frequency than the frequency of a encoded message signal. This trainer is a demonstration unit. In this trainer, the signal to be modulated namely Sine, Square or any other signal in the range of 100Hz to 2KHz with 1-2 V Peak to Peak is applied as input to the modulating input terminal. The built-in clock generator provides the required sampling rate. It is possible to change this clock frequency by patch cording necessary RC combinations. Thus the signal to be modulated is sampled now. The FSK modem converts this into series of pulses as output after locking takes place. This signal is further processed and a Frequency Shift Keyed output is available at the demodulating output terminal. This FSK signal is further processed through a signal reconstructor circuit and the actual signal is available at the output terminals for observation. Thus various waveforms namely modulating signal, sampling clock, FSK modulated signal, Demodulated signal, reconstructed signal can be viewed on an external Oscilloscope for measurements. This trainer is assembled in an ergonomically designed cabinet, with necessary power supplies, test points for observations. This require an external function generator and an 20MHz oscilloscope for measurements. See Enlarge Click to Enlarge PHASE SHIFT KEY MODULATION TRAINER. MODEL IBL-PSKT-1 Phase Shift Key (PSK) Modulation is a form of Binary Digital Modulation. The modulation process corresponds to a scheme of switching or keying the amplitude, frequency or phase of the carrier wave between Ones and Zeros. The result of this yields three different methods of modulation, they are FSK, ASK and PSK. In Phase shift key technique, a message signal of fixed amplitude and fixed carrier wave is used to denote Ones and Zeros. The phase of carrier and the message differs by 1800 It is represented in the form of S(t) = Ac . cos(2?fct) to represent Logic 1 and S(t) = Ac . cos(2?fct + ?) to represent Logic 1 In this trainer, necessary blocks with components are available to accomplish the above task. This unit requires an additional function generator and pulse generator in the range of 100Hz to 100KHz. An external dual beam Oscilloscope is required to observe the input output waveforms. The entire instrument is assembled in an ergonomically designed FRP cabinet. See Enlarge Click to Enlarge PHASE SHIFT KEY DE-MODULATION TRAINER . MODEL IBL-PSKR-1 This unit is a PSK De-Modulator. This unit makes use of signals from PSKT-1 as input source and performs the De-Modulation process. In this trainer, necessary blocks with components are available to accomplish the above task. An external dual beam Oscilloscope is required to observe the input output waveforms. The entire instrument is assembled in an ergonomically designed FRP cabinet. See Enlarge Click to Enlarge PSEUDO RANDOM BIT SEQUENCE (PRBS) GENERATOR . MODEL IBL-PRBS-1 Pseudo Random Bit Sequence is used to scramble data in a communication system for security reasons. Some of the applications are in Cryptography, computer data security and integrity, prevent unauthorized usage of cable TV line by scrambling data, generating elaborate tonal structures unlike any known instrument, instrument voicing etc. These sequencers have several nice features. First they can be of maximal length, that is they can be as long as a register sequence can possibly be. This turns out to be one less than 2n, so that the circuit is essentially as efficient as a binary counter. Second, the number appears in an apparently random order, although, of course they repeat every time the sequence is clocked completely through 2n-1 counts. The same noise pattern repeats every n-1 clock cycles. This is used for testing audio systems. In fact pseudo noise turnout to be better than real noise. The randomness is complete over one total cycle, where real noise requires a very long (ideally infinite) time average to get true randomness. This PRBS generator makes use of 63-state count using 6 registers. The binary outputs of this sequencer are processed to obtain random analog levels. As a result of this a series of uniformly timed steps of random analog values can be generated. This can be used to test a musical system. It is possible to change the bit sequence by changing the count sequence using patch chords. See Enlarge Click to Enlarge TRANSMISSION LINE TRAINER. MODEL IBL-TLT-1 The Transmission Line Trainer consists of an experimental unit and two coaxial cables of 60 meters each of 50 Ohms RG58 and 75 Ohms RG59 in two separate units. In addition to this BNC cables of assorted lengths are supplied with this trainer. The purpose of this trainer is to study the transmission line characteristics on coaxial cables. In order to facilitate this the experimental unit is provided with necessary function generator, attneuator pads, decade Resisters, capacitors and inductors are supplied. This unit has 4 channels for conducting the experiments. Each channel is impedance matched. This also has a delay generation circuit, which can be used to set a time difference between the input and outputs. In addition to this a simple 5-band spectrum analyzer is also provided. This can provide qualitative harmonics present in an in incoming or outgoing signal. See Enlarge [1] 2 [ Next»] Go to Top