Introduction to Space Systems and Spacecraft Design Space Systems Design
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Introduction to Space Systems and Spacecraft Design Space Systems Design Communications - Decibel Ref: SMAD Sections – 13 Communications Architecture
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Communications - Decibel Ref: SMAD Sections – 13 Communications Architecture. Introduction to Space Systems and Spacecraft Design Space Systems Design. Communications - Decibel. Dealing with large and small signal levels. Decibels -- powers of 10. Absolute power. - PowerPoint PPT Presentation
Transcript of Introduction to Space Systems and Spacecraft Design Space Systems Design
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
Communications - DecibelRef: SMAD Sections – 13 Communications Architecture
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
Communications - Decibel
Dealing with large and small signal levels
Decibels -- powers of 10PdB = 10Log10 (P2/P1)
Absolute power
PdB(dbW) = 10Log10 (P2(W)/1(W)
units - dbWunits - W
units – 1 W
PdB(dbm) = 10Log10 (P2(mW)/1(mW)
units - dbmunits - mW
units – 1 mW
Amplifier gain/loss
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
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Communications - Decibel Dealing with large and small signal
levelsDecibels -- powers of 10
PdB = 10Log10 (P2/P1)
PdB(dbW) = 10Log10 (P2(W)/1(W)
PdB(dbm) = 10Log10 (P2(mW)/1(mW)
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
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Communications - Decibel
Output (dBW) = Input (dBW) + Gain(dB)
Dealing with large and small signal levels Decibels -- powers of
10
Output (W) = Input (W) x Gain
Add decibel
Multiply absolute values
Component Loss (-Db)
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
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Communications - Decibel
Output (dBW) = Input (dBW) + (- Loss(dB))
Dealing with large and small signal levels Decibels -- powers of
10
Output (W) = Input (W) x Loss
Add decibel
Multiply absolute values
Loss is value < 1.0
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
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Communications - Decibel
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
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Communications - Decibel
PdB = 10Log10 (P2/P1)
P1 P2
Comparing Power Levels using Decibels
When (P2/P1) > 0 dB is positive
When (P2/P1) < 0 dB is negative
Amplifier – gain in power
Let P1 = 4 watts
Let P2 = 8 watts
P2/P1 = 2 ratio
P(dB) = 3 dB
Let P1 = 8 watts
Let P2 = 4 watts
P2/P1 = 0.5 ratio
P(dB) = -3 dB
Attenuation – loss in power
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
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Communications - Decibel
PdBm = 10Log10 (P(mw)/1mw) reference to 1mw
Absolute Power Levels using Absolute Power Levels using DecibelsDecibels
PdBw = 10Log10 (P(w)/1w) reference to 1w
= 10Log10 (1mw/1mw) = 0dBm
= 10Log10 (8w/1w) = 9dBw
Every time it doubles, add 3dB
Every time it is 1/2, subtract 3dB
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
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Communications - Decibel
0 dBw = 1 watt
3 dBw = 2 watts
6 dBw = 4 watts
9 dBw = 8 watts
10 dBw = 10 watts = 1 watt x 101
20 dBw = 100 watts = 1 watt x 102
30 dBw = 1000 watts = 1 watt x 103
100 dBw = 10 M watts = 1 watt x 1010
Powers greater >= 1 watt
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
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Communications - Decibel
0 dBm,= 1 milliwatt
-3 dBm = 0.5 milliwatts
-6 dBm = 0.25 milliwatts
-9 dBm = 0.125 milliwatts
-10 dBm = 0.100 milliwatt = 1 milliwatts x 10-1
-20 dBm = 0.010 milliwatts = 1 milliwatts x 10-2
-30 dBm = 0.001 milliwatts = 1 milliwatts x 10-3
= 0.001 milliwatts = 1 microwatt
Powers greater <= 1 watt
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
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Communications - Decibel
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
12
Communications - Decibel
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