Design IV. E232 Fall 07

Transcription

1 Design IV Fall 07 Class 7 Bruce McNair bmcnair@stevens.edu 7-1/27

2 Example Low-Pass Filter Design (like HW2 Problem 3.18) A(f) db f Cutoff (corner) frequency 7-2/27

3 Transmission Systems Analog signal transmission S1( N1) S2( S1( N1) N2) + S3 S2 S1 N1 + N2 + N3 ( ( ( ) ) ) Subsystem 1 Subsystem 2 Subsystem 3 Noise=N 1 Noise=N 2 Noise=N 3 Noise from each stage combines with input noise and cannot be removed 7-5/27

4 Transmission Systems Digital signal transmission Subsystem 1 Subsystem 2 Subsystem 3 Noise=N 1 Noise=N 2 Noise=N 3 Output at each stage is regenerated, allowing transmission to start with clean, unimpaired signals. Signals change at established points in time, with specific allowed levels 7-6/27

5 Today s topics Computerized Data Acquisition Architecture Components Signal representation A/D conversion 7-7/27

6 Computerized Data Acquisition Measurement system architecture System under test sensor sensor sensor sensor signal conditioning signal conditioning signal conditioning signal conditioning S e l e c t o r Analog-todigital converter(s) Computer Computercontrolled test equipment GPIB/HPIB/IEEE-488 signals controls 7-8/27

7 Computerized Data Acquisition Measurement system architecture System under test sensor sensor sensor sensor signal conditioning signal conditioning signal conditioning signal conditioning S e l e c t o r Analog-todigital converter(s) Computer Computercontrolled test equipment GPIB/HPIB/IEEE-488 signals controls 7-9/27

8 Computerized Data Acquisition Components Display Hard Disk External devices I/O interfaces CPU RAM Computer Keyboard, Mouse Removable Media (CD, DVD,USB) 7-10/27

9 Computerized Data Acquisition Signal representation +V 1 TRUE 0 0 FALSE All information is represented by a series of 1 s and 0 s using Base-2 arithmetic 7-11/27

10 Computerized Data Acquisition Signal representation In Base-10 arithmetic: = (8 x 10 2 ) + (4 x 10 1 ) + (9 x 10 0 ) 7-12/27

11 Computerized Data Acquisition Signal representation In Base-10 arithmetic: = (8 x 10 2 ) + (4 x 10 1 ) + (9 x 10 0 ) In Base-2 arithmetic: = = (1 x 2 9 ) + (1 x 2 8 ) + (0 x 2 7 ) + (1 x 2 6 ) + (0 x 2 5 ) + (1 x 2 4 ) + (0 x 2 3 ) + (0 x 2 2 ) + (0 x 2 1 ) + (1 x 2 0 ) = /27

12 Converting Base-10 to Base-2: Computerized Data Acquisition First, recognize powers of 2: ~ ~ 1,000, ~ 1,000,000, /27

13 Computerized Data Acquisition Converting Base-10 to Base-2: Successive integer division by 2, noting remainder Remainder: 2)849 2)424 -> 1 2)212 -> 0 2)106 -> 0 2)53 -> 0 2)26 -> 1 2)13 -> 0 2)6 -> 1 2)3 -> 0 2)1 -> 1 0 -> 1 -> /27

14 Computerized Data Acquisition Converting Base-2 to Base-10: Successive doubling with addition of bits = = (((1 x 2) + 0) x 2) + 0) x 2) + 1) x 2) + 0) x 2) + 0) x 2) + 1 = /27

15 Representing binary numbers Computerized Data Acquisition : MSB LSB 7-17/27

16 Representing binary numbers Computerized Data Acquisition : MSB LSB Representing negative numbers 2 s complement: : Sign MSB LSB 7-18/27

17 Representing binary numbers Computerized Data Acquisition : MSB LSB Representing negative numbers 2 s complement: : Sign Invert bits Add MSB LSB 7-19/27

18 Arithmetic with 2 s complement Computerized Data Acquisition X s complement numbers can be added (subtraction by adding negative numbers) continually, as long as final result can fit in word size. 7-20/27

19 Analog-to-digital converters Computerized Data Acquisition MSB Analog input signal (e.g., 0-10V) A/D converter N-bits 2 N levels LSB 7-21/27

20 Computerized Data Acquisition Analog-to-digital converters Parallel/Flash A/D V ref R/2 R R R R R R/ Encoder: > > > > > > > > 0000 V in 7-22/27

21 Digital-to-analog converters Computerized Data Acquisition R - + V out b 3 b 2 b 1 b 0 2R 2R 2R 2R -V ref R R R 2R 7-23/27

22 Digital-to-analog converters Computerized Data Acquisition R - + V out b 3 b 2 b 1 b 0 2R 2R 2R 2R -V ref R R R 2R Voltage divider 7-24/27

23 Digital-to-analog converters Computerized Data Acquisition R - + V out b 3 b 2 b 1 b 0 Summing 2R 2R 2R 2R junction -V ref R R R 2R V = K( b 2 + b 2 + b 2 + b 2 ) out /27

24 Computerized Data Acquisition Successive approximation A/D converter Comparator V in Approximation of input + - Input > < approx. Reference voltage D/A converter Control logic Output logic Adjust digital signal to input 7-26/27

25 Next topics Computerized Data Acquisition Sampling Quantization effects Fourier Transform and frequency domain analysis 7-27/27