Lab2.3 Linear Pulse Code Modulation Report Zachary Trotter

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EET380 Digital Communication I Instructor: Michael Blythe Campus: Lab 2.3 Linear Pulse Code Modulation Student Name(s): Zachary Trotter Click or tap here to enter text.

2 Contents Honor Pledge: .............................................................................................................................................. 2 Abstract ....................................................................................................................................................... 3 Introduction ................................................................................................................................................. 3 Procedures ................................................................................................................................................... 4 Conclusion ................................................................................................................................................. 12 References ................................................................................................................................................. 13 Honor Pledge: I pledge to support the Honor System of ECPI. I will refrain from any form of academic dishonesty or deception, such as cheating or plagiarism. I am aware that as a member of the academic community, it is my responsibility to turn in all suspected violators of the honor code. I understand that any failure on my part to support the Honor System will be turned over to a Judicial Review Board for determination. I will report to the Judicial Review Board hearing if summoned. Date: 12/15/2023 Zach Trotter

3 Abstract The purpose of this lab to become familiar with TDM-PAM implementation the use of ADC and DAC and the implementation of a 4-Channel Baseband TDM-PCM Introduction Pulse code modulation (PCM) is a baseband digital waveform modulation in which an analog signal as the input signal is changed to relevant train of “0” and “1”. A first step in PCM is creation of PAM signal as shown in the following figure. Then a binary code word is assigned to every flat-top amplitude of PAM signal after passing through an analog to digital converter. To be able to combine and transmit multiple signals using a single transmitter over the same transmission media, the signals are multiplexed. Time division multiplexing (TDM) let combine multiple PCM signals based on their digital attribute. PCM signal is created by passing a PAM signal through an analog to digital converter (ADC). In reality, an ADCs filters the analog signal, take samples of the filtered signal, quantizes and then convert the quantized samples to unique code word that looks like random train of 0s and 1s. 12/15/2023 Zach Trotter

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4 There is a difference between TDM-PAM and TDM-PCM. In TDM-PAM the analog samples of multiple analog signals are multiplexed in time, which creates another analog signal. In TDM-PCM, the code words of different PAM signals after passing through an ADC (or ADCs) are multiplexed in time. Once a big PCM frame of multiple signals is generated, it is ready for transmission. In this lab, you will implement a simple 4-channel TDM-PAM, then you will use ADC and DAC and finally you will implement a 4-channel TDM-PCM. Throughout these steps you will use your knowledge of digital systems and digital circuits. Procedures Part A. TDM-PAM Procedure: Assemble the following circuit using MultiSIM. If you have difficulties to assemble the circuit, please download the MultiSIM file of TDM-PAM.ms11. In this circuit, the 4 function generators are creating different DC level to be able to track the operation of the TDM-PAM circuit. However, you may use a waveform instead of DC level. Be careful! do select the frequency of the waveforms less than half of the sampler frequency (5 x 1 kHz), otherwise the signal would not be uniquely recoverable at receiver. 12/15/2023 Zach Trotter

5 Like 4066, 4016 chip is also a quad of analog switches. In this circuit, you also see 4017 chip. This chip is a decade ring counter, which also may work as base-5 counter. In the above circuit, we just employ 4 channels of the available 5 channels for TDM-PAM. Experiment A.1 : Run the simulation and look at the oscilloscope screen. Describe your observation briefly. The square wave is increasing by 1at roughly .001seconds, the counter is increasing the voltage to change the square wave then when the counter resets after a count of four the voltage drops back to zero where the process repeats. Experiment A.2 : Using the two oscilloscope cursors, measure the duration of one whole period of the multiplexer. Then put the snapshot of your measurement here. Compare your measurement result with the period of the clock pulse at ring counter 4017. Write your reasoning. My measurement results come in at 3.979ms which would be almost right since the timing of the click is 1ms since the counts moves once per ms and the voltage increases from zero to 4, I think the measurement is close enough to be considered accurate based on the timing of the clock 12/15/2023 Zach Trotter

6 Task : Explain what do you need to do to increase the number of the multiplexed signals from 4 to 5? Do you have any idea how to increase the number of multiplexed signals to 10 signals? Hint: Look into the datasheet of 4017. One rich place that you may find the data sheet of this chip and any other electronic parts (no ordinary resistor, capacitor or inductor) is: https://datasheetcatalog.com . 12/15/2023 Zach Trotter

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7 Then, after selecting one manufacturer’s product as shown below: Select a proper part to open its datasheet in pdf format, as shown below: The physical, electrical and functional details of the chip’s characteristics are in the opened datasheet. Space for answer to the given task: If more signals need to be multiplexed, the timing should be changed for the outputs. The transition period for the master reset signal needs to be longer. Below is the timing diagram for the 4017 IC chip. 12/15/2023 Zach Trotter

8 Part B. Analog to digital conversion and digital to analog conversion In this part of the lab, you will convert a given analog signal to digital and then, convert it back to analog form. Procedure: Assemble the following circuit using MultiSIM. If you have difficulties to assemble the circuit, please download the MultiSIM file of ADC_DAC.ms11. The ADC and DAC blocks that are used in this circuit are generic ADC and DAC chips. Just as reminder, those blocks that are green in MultiSIM-11 are not functioning and work just as schematic. 12/15/2023 Zach Trotter

9 Experiment B.1 : Run the simulation and look at the oscilloscope screen. Describe your observation briefly. Write about all three waveforms. There are three waveforms on the oscilloscope screen . The RED waveform is the AC waveform going into the ADC . The BLUE waveform is the digital signal that has been built from the converter and passed through the comparator . The GREEN waveform is the rebuilt analog signal by passing the digital signal through a resistor and bleed capacitor to smooth out the waveform Experiment B.2 : The low-pass RC filter that is used after the DAC is used for signal reconstruction. Can you make a connection with the time shift of the low pass filter’s output and the flat-top signal (the blue signal on oscilloscope screen)? The timing shift comes from the low - pass filter building the waveform off of the leading edge of the flat - top waves . If you look at the oscope , you can see the signal matches every step in the step and down of the wave . Experiment B.3 : Now, you increase the sampling frequency from 10 kHz to 50 kHz. Briefly explain how the reconstruction error will change in filter’s output. 12/15/2023 Zach Trotter

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10 The reconstruction error has been greatly decreased and is now able to take more samples over this period of time thereby cleaning up the signal making the reconstructed signal more smooth . Part C. Pulse Code Modulation (PCM) Procedure: Please download the MultiSIM file of PCM_TDM.ms11. In this part of the lab, you will simulate a linear PCM-TDM, using basic chips. As you see in the schematic of this system, a PAM signal that you created in the part “A” of this lab is given to an ADC. To send the ADC’s output over a serial line, we used a shift register as parallel to serial converter. 74165 is an 8-bit parallel-in serial-out shift register. Experiment C.1 : Run the simulation and look at the oscilloscope screen. Describe your observations. Please include the snapshot of the signal along you’re your write-up. The scope shows 4 signals, the RED signal is the output of the 74165 IC chip, that is the PCM-TDM. The Green signal is the clock signal, that would be a 5VDC signal that stays high and the blue signal is the modulation signal. 12/15/2023 Zach Trotter

11 12/15/2023 Zach Trotter

12 Experiment C.2 : You find an amount of shift between the system’s output and the generated PAM. Which of these parts does make this delay? The ADC is what creates the delays. Experiment C.3 : Without changing the frequency of the sampler, what can be the maximum frequency of the launched signal to the 4016 chip? 10kHz Experiment C.4 : based on the full scale voltage (5 V) and the code word size of ADC (8-bit), can you find the SQNR, Dynamic Range and the average quantization error of this PCM system? Dynamic Range = DR = Vmax/Vmin = 2^n or DRdB = 6.02db/bit = 8- bits*6.02= 48.16dB SQNR = (S/N = 1.76 +6.02(8)= 49.92dB) = (S/N)q(dB) = 8 log3(256^2 = 42.34dB) The average quantization error for the system is q = Vmax/2^n = 5/256 = 0195V Conclusion  Describe TDM-PAM. Time division multiplexed - Pulse amplitude modulation is a technique where narrow carrier pulses are used and sampled pulses are placed between these pulse using time division multiplexing .  Based on your experience in this lab, please briefly explain how a TDM-PCM signal is generated. A TDM-PCM signal is built using a PCM signal and multiplexing it through time division. This entails placing other Pulse-code modulated signal on the same carrier as the original using time division multiplexing. 12/15/2023 Zach Trotter

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13 References 4017 Datasheet pdf - Decade Counter/Divider with 10 Decoded Output - Fairchild Semiconductor . (n.d.). Www.datasheetcatalog.com. Retrieved December 14, 2023, from https://www.datasheetcatalog.com/datasheets_pdf/4/0/1/7/4017.shtml Frenzel, L. E. (2016). Principles of electronic communication systems . Mcgraw-Hill Education. 12/15/2023 Zach Trotter