Adc 08 Pulsem
-
Upload
mehboob-khokhar -
Category
Documents
-
view
225 -
download
0
Transcript of Adc 08 Pulsem
![Page 1: Adc 08 Pulsem](https://reader035.fdocuments.in/reader035/viewer/2022062306/577ccd621a28ab9e788c346b/html5/thumbnails/1.jpg)
ANALOG & DIGITAL COMMUNICATION
By Engr. Hyder Bux MangrioInstitute of Information & Communication
TechnologiesMehran University of Engineering and Technology,
Jamshoro.
09TL-BATCH
Today's Lecture:27Digital Pulse Modulation
05/03/[email protected] 1
![Page 2: Adc 08 Pulsem](https://reader035.fdocuments.in/reader035/viewer/2022062306/577ccd621a28ab9e788c346b/html5/thumbnails/2.jpg)
Most widely used Developed in 1937 at the Paris
Laboratories of AT&T by Alex H. Reeves. PCM is a method of serially transmitting an
approximate representation of an analog signal.
The PCM signal itself is a succession of discrete, numerically encoded binary values derived from digitizing the analog signal
05/03/[email protected] 2
![Page 3: Adc 08 Pulsem](https://reader035.fdocuments.in/reader035/viewer/2022062306/577ccd621a28ab9e788c346b/html5/thumbnails/3.jpg)
In pulse-code modulation (PCM), an analogmessage signal is represented by a sequence of coded pulses, which is accomplished byrepresenting the signal in discrete form in both time and amplitude PCM is the most basic form of digital pulse Modulation A PCM system contains three main blocks: PCM transmitter Transmission path Receiver
05/03/[email protected] 3
![Page 5: Adc 08 Pulsem](https://reader035.fdocuments.in/reader035/viewer/2022062306/577ccd621a28ab9e788c346b/html5/thumbnails/5.jpg)
Steps of Pulse Code Modulation1. Quantization : The max. expected amplitude
of the analog signal is first "quantized" (it is divided into discrete numerical levels) quantized range = 2 (by the power of no. of converter bits)
Quantized Level= 2n
Where n is number of converter bits
05/03/[email protected] 5
![Page 6: Adc 08 Pulsem](https://reader035.fdocuments.in/reader035/viewer/2022062306/577ccd621a28ab9e788c346b/html5/thumbnails/6.jpg)
05/03/[email protected] 6
![Page 7: Adc 08 Pulsem](https://reader035.fdocuments.in/reader035/viewer/2022062306/577ccd621a28ab9e788c346b/html5/thumbnails/7.jpg)
2. Sampling: The process of determining theinstantaneous voltage at these given intervals of time
05/03/[email protected] 7
![Page 8: Adc 08 Pulsem](https://reader035.fdocuments.in/reader035/viewer/2022062306/577ccd621a28ab9e788c346b/html5/thumbnails/8.jpg)
3. Encoding : The "encoded binary value" isproduced representing an approximation of amplitude at the time of the sample.
– The binary value representing the amplitude is then serialized to form the PCM signal and transmitted onto the communication channel.
05/03/[email protected] 8
![Page 9: Adc 08 Pulsem](https://reader035.fdocuments.in/reader035/viewer/2022062306/577ccd621a28ab9e788c346b/html5/thumbnails/9.jpg)
9
Figure : A 3-bit PCM system showing analog to 3-bit digital
Digital signal
Sampling pulses
Digital clock
Serial PCM
output
Analog
input
Pulse
generator
Sampler
Encoder
t
t
Ts
001011101111
1 2 3 000010100110
31
57
1
011 11 0 10 1
2 3
10 04
A(t)
0 4
![Page 10: Adc 08 Pulsem](https://reader035.fdocuments.in/reader035/viewer/2022062306/577ccd621a28ab9e788c346b/html5/thumbnails/10.jpg)
10
For input signal minimum amplitudeSQR = minimum voltage / quantization noiseFor input signal maximum amplitudeSQR = maximum voltage / quantization noise
![Page 11: Adc 08 Pulsem](https://reader035.fdocuments.in/reader035/viewer/2022062306/577ccd621a28ab9e788c346b/html5/thumbnails/11.jpg)
11
Linear quantizng in PCM systems has two major drawbacks.
(i) The uniform step size means that weak analog signals will have a much poorer S/Nq than the strong signals.
(ii) Systems of wide dynamic range require many ending bits and consequently wide system bandwidth.
Companding Companding is the process of compressing, then
expanding.Or nonlinear encoding/decoding, called companding
![Page 12: Adc 08 Pulsem](https://reader035.fdocuments.in/reader035/viewer/2022062306/577ccd621a28ab9e788c346b/html5/thumbnails/12.jpg)
12
000
001
010
001
100
101
110
111 Linear analog-to-digital converter
transfer characteristic.
N
Full scale, or VFS
Dig
ital o
utpu
t cod
e
q
Sample voltage input(Volts) Vmax
(Volts)
} q0
+ q / 2
- q / 2B. Quantum uncertainty or quantization noise, ± q/2
Fig : Linear ADC characteristic and quantization noise.
![Page 13: Adc 08 Pulsem](https://reader035.fdocuments.in/reader035/viewer/2022062306/577ccd621a28ab9e788c346b/html5/thumbnails/13.jpg)
05/03/[email protected] 13
![Page 14: Adc 08 Pulsem](https://reader035.fdocuments.in/reader035/viewer/2022062306/577ccd621a28ab9e788c346b/html5/thumbnails/14.jpg)
Given a sine wave whose peak-to-peak amplitude utilizes the full range of a 12 bit A/D converter, compute the SQNR.
05/03/[email protected] 14
![Page 15: Adc 08 Pulsem](https://reader035.fdocuments.in/reader035/viewer/2022062306/577ccd621a28ab9e788c346b/html5/thumbnails/15.jpg)
05/03/[email protected] 15
![Page 16: Adc 08 Pulsem](https://reader035.fdocuments.in/reader035/viewer/2022062306/577ccd621a28ab9e788c346b/html5/thumbnails/16.jpg)
delta modulation converts or encode the message into sequence of binary digits.
05/03/[email protected] 16
Figure: Delta Modulator
![Page 17: Adc 08 Pulsem](https://reader035.fdocuments.in/reader035/viewer/2022062306/577ccd621a28ab9e788c346b/html5/thumbnails/17.jpg)
05/03/[email protected] 17
![Page 18: Adc 08 Pulsem](https://reader035.fdocuments.in/reader035/viewer/2022062306/577ccd621a28ab9e788c346b/html5/thumbnails/18.jpg)
05/03/[email protected] 18
![Page 19: Adc 08 Pulsem](https://reader035.fdocuments.in/reader035/viewer/2022062306/577ccd621a28ab9e788c346b/html5/thumbnails/19.jpg)
05/03/[email protected] 19
![Page 20: Adc 08 Pulsem](https://reader035.fdocuments.in/reader035/viewer/2022062306/577ccd621a28ab9e788c346b/html5/thumbnails/20.jpg)
05/03/[email protected] 20