Introduction to Communications Ref: SMAD Sections – 13 Communications Architecture Introduction to Space Systems and Spacecraft Design Space Systems Design

2 Introduction to Communications TT&C (Operations) How is this connection made? Laser RF – radio frequency What is the comm used for? Data Relay Data Collection Sensors Introduction to Space Systems and Spacecraft Design Space Systems Design

3 Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

4 Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

5 Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

6 Communications Architecture Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

Your car? They set in the parking lot by day and garage by night. Your car? We have an engineering challenge. Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

Cold at night. Hot sun by day. Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

TMThWSFSu 50 0 F 90 0 F 80 0 F 70 0 F 60 0 F You need to measure the max and min temperatures in the cars within one degree over a period of one week. Here is how the temp varies. Max Min Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

TMThWSFSu 50 0 F 90 0 F 80 0 F 70 0 F 60 0 F How do we measure the temperature? We bought this, will it work? It would be better if in F. Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

TMThWSFSu 50 0 F 90 0 F 80 0 F 70 0 F 60 0 F We bought this, will it work? Lets look closer at scale. Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

Maybe wrong scale. Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

Can we get one degree accuracy in reading this scale? Lets look close at the scale. I can not read this within one degree accuracy! Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

We assume so. Can we get one degree accuracy in reading this scale? Got this. Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

TMThWSFSu 50 0 F 90 0 F 80 0 F 70 0 F 60 0 F How often do we take the measurement of temperature? We got the right accuracy now. Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

TMThWSFSu 50 0 F 90 0 F 80 0 F 70 0 F 60 0 F Once a week? Not going to find the min and max that way! Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

TMThWSFSu 50 0 F 90 0 F 80 0 F 70 0 F 60 0 F How often do we take the measurement of temperature? Ten times a week at random times? Not going to find the min and max that way! We can see that. Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

TMThWSFSu 90 0 F 80 0 F 70 0 F 60 0 F Ok, now maybe we take many measurement points! 50 0 F Maybe lots. Maybe better, but good enough? We don’t know. Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

TMThWSFSu 90 0 F 80 0 F 70 0 F 60 0 F Fortunately there was a mathematician named Nyquist F The Nyquist theorem - In practical measurements. Sample rate = 2.2 f max Sampling faster does not produce more accurate data. To reproduce the waveform exactly, sample 2x the max freq in data. Sample rate = 2f max Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

Measuring analog signals What accuracy do you need? What sample rate do you need? Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

21 Baseband Data Types of Data (Satellite Use) Analog Digital Analog Digital Discrete two state representation of conditions - Switches On/Off - 0/1 - 0/5v Natural occurring - Temperature - Wind velocity - Voltage - Current - Vibration Baseband Data Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

22 Analog to Digital Converter Introduction to Space Systems and Spacecraft Design Space Systems Design

23 Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

24 Now that you have converted analog to digital, how good is it? What is a measure of good ? Example: Consider you have a 3 bit ADC. 3 bits represent 8 states If 6.3v gives  110 A --  D If now, you do a D  A you will get 6.5v You have a 0.2v ERROR Quantization Error6.3v v 6.0v6.5v Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

Quantization Error What effects quality of digitized signal? How often do you sample – sample rate? How often do you sample – sample rate? What is the resolution of the ADC? What is the resolution of the ADC? Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

26 Jameco # ADC0831CCN $1.95 MAX1003 Low-Power, 90Msps, Dual 6-Bit ADC $3.96 MAX1402 5V, 18-Bit, Low-Power, Multichannel, Oversampling (Sigma Delta) ADC $8.95 MAX Bit, 20Msps, +3.3V, Low-Power ADC with Internal Reference $14.25 MAX107 Dual, 6-Bit, 400Msps ADC with On-Chip, Wideband Input Amplifier $29.25 MAX105 Dual, 6-Bit, 800Msps ADC with On-Chip, Wideband Input Amplifier $35.95 Comparison of ADC Increase ADC resolution Increase ADC resolution More Data More, More, More, More  bits to transfer to store to store How do you reduce quantization error? Introduction to Space Systems and Spacecraft Design Space Systems Design

27 What about sample rate, how much is enough? From the Nyquist theorem – if f s = 2f m the signal can be reproduced exactly Where fs is the sample frequency f m is the maximum frequency in the signal f s = 2.2f m found to be minimum in practice Practical limits on sampling rate ---  fs = 2.2fm quantitization error -  cost, amount of accuracy needed How often do you sample – sample rate Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

28 For measurements for telemeter and on each subsystem, define: How many things to measure? For each measurement, what resolution? What sample rate? How long to measure – duty cycle? What effects quality of digitized signal? How often do you sample – sample rate? How often do you sample – sample rate? What is the resolution of the ADC? What is the resolution of the ADC? Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

29 Most Common data format (transmission) Digital Less Interference (Noise sources) natural man made Can correct errors Handled by many IC devices Required for many applications TV  Analog  Digital HDTV Radio  Analog  Digital satellite radio Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

30 Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

31 Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

32 Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

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35 Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

36 - Need to have an amateur license for working ground stations in amateur bands. Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

10 GHz 9 GHz11 GHz Carrier Freq band. 400 MHz500 MHz 450 MHz 37 Modulation Baseband data – data as measured – analog or digital Carrier frequency – transmitter RF with data Color TV (92.5) MHz Baseband Color TV (92.5) MHz Baseband Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

38 Modulation 400 MHz500 MHz Carrier Freq band. 450 MHz Color TV (92.5) MHz Baseband MHz – MHz Color TV (92.5) MHz Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

39 Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

40 10 GHz 9 GHz11 GHz Carrier Freq band. Color TV (92.5) MHz Baseband 9, MHz10, GHz Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

41 Modulation Methods 433 MHz433.5 MHz 2 GHz BW 0.5 MHz BW 9, MHz10, GHz Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

42 Modulation Ways to put baseband data on a carrier. Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

43 X Baseband Data Amplifier Antenna ~ Carrier Must have a way to put baseband information on the carrier frequency. Modulation RF Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

44 Modulation Types Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

45 Half amplitude change Analog amplitude change Modulation Types Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

46 BPSK Modulation Types BW = R Binary Phase Shift Keying Shift Phase 180 o R = data rate Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

47 Modulation Types Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

48 Modulation Types BW = 2R FSK Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

49 BW = R BW = R/2 BW = 2R R = data rate Modulation Methods Summary Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

50 Rx Tx Modulation Effects on Errors E b = Energy/Bit = Pr T b Pr = power in average received signal T b = bit period N o = noise spectrum density Data stream time EbEb NoNo Energy/bit = Noise EbEb NoNo (Signal/Noise Ratio) Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

51 Modulation Effects on Errors Energy/bit = Noise EbEb NoNo (Signal/Noise Ratio) Few Errors time EbEb NoNo EbEb NoNo EbEb NoNo NoNo EbEb More Errors EbEb >>N o EbEb >N o EbEb =N o EbEb <<N o Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

52 Energy/bit = Noise EbEb NoNo (Signal/Noise Ratio) Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

53 Phase Shift Keying Errors get worse for increased changes/cycle. Bit Error Rate Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

54 Errors get worse for increased changes/cycle. Bit Error Rate Disadvantage of Increased Changes/Cycle BER Increases Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

55 Bandwidth decreases for a given data rate. Some Good Here Advantage of Increased Changes/Cycle Phase Shift Keying Bandwidth decreases for a given data rate. BW = R / BW = R/2 BW = R/4 BW = R/8 Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

56 9.6dB13.3dB Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

dB 14.5dB Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

58 9.6dB13.3dB Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

dB 14.5dB Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

60 Data Checksum Data Parity Bit XXXX Parity Bit Odd parity – count of 1’s is odd Even parity – count of 1’s is even Even Parity XXXX XXX XXXX Data – good bad Checksum – created by apply an algorithm to the data to get a unique number. Error Detection & Correction -1 Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

61 Error Detection & Correction -2 How do you correct when bad? Data Checksum Calculate checksum Calculate & compare checksum X X Bad Checksum Request resend Ok, I will do a resend X X Baseband Data Baseband Data Good Checksum Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

62 Improve BER with FEC Data FEC Forward Error Correction Baseband Data Baseband Data ModulationDemodulation Extra bits used to correct errors X X Amplifier Error Detection & Correction -3 Forward Error Coding Data FEC As many bits in FEC as data Start here 10/6/2009 Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

dB 14.5dB 5 dB FEC Forward Error Correction Introduction to Communications Introduction to Space Systems and Spacecraft Design Space Systems Design

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Introduction to Space Systems and Spacecraft Design Space Systems Design 66 From Satellite Operations Slides by Dr. J. Cutler – Univ. of Michigan

67 Questions? Introduction to Space Systems and Spacecraft Design Space Systems Design