Introduction to RF & Wireless - Part 1

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Part 1 covers RF signal behavior, wireless systems hardware and wireless systems operation

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Introduction to RF & Wireless - Part 1

  1. 1. A man pushing his car stopped outside a hotel. Assoon as he got there he knew he was bankrupt. Why?
  2. 2. A man pushing his car stopped outside a hotel. Assoon as he got there he knew he was bankrupt. Why?
  3. 3. Carl Weisman’sIntroduction to RF & Wireless Two Day Seminar Module 1
  4. 4. Course ObjectivesExplain ♦ RF signal behavior ♦ System hardware makeup ♦ Wireless systems’ operationCommunicate ♦ Using over 300 termsHave Fun
  5. 5. Daily Schedule8:30 am – 10: 00 am Fun10:00 am – 10:15 am Break10:15 am – 11:45 am FunNoon – 1:00 pm Lunch1:00 pm – 2:30 pm Fun2:30 pm – 2:45 pm Break2:45 pm – 4:15 pm Fun
  6. 6. Course AgendaDay One • Morning (Module 1) – Introduction to RF • Afternoon (Module 2) – RF hardwareDay Two • Morning (Module 3) – Older systems & mobile telephony • Afternoon (Module 4) – Newer systems & the future
  7. 7. Module 1 - Introduction To RF 1. The Basics 2. RF Behavior 3. Modulation 4. Noise
  8. 8. Module 11. The Basics2. RF Behavior 3. Modulation 4. Noise
  9. 9. 1. The Basics VocabularyTransmitters & Receivers Signals
  10. 10. 1. The Basics VocabularyTransmitters & Receivers Signals
  11. 11. VocabularyElectronics Terms ♦ Voltage: A potential between 2 points (Volts) ♦ Current: A flow of electrons (Amps) ♦ Power = Voltage x Current (Watts) ♦ Energy = Power x Time (Watt-hours) ♦ AC: Varies with time (e.g., wall outlet) ♦ DC: Constant (e.g. flashlight battery) The Basics - Vocabulary
  12. 12. VocabularyMore Electronics Terms ♦ Signal: Electrical energy made to vary in a predetermined way ♦ Device: An electronic gadget that is indivisible ♦ Component: Same as a device ♦ Circuit: A collection of interconnected devices ♦ RF: Radio Frequency ♦ Wireless: A marketing term The Basics - Vocabulary
  13. 13. VocabularyPrefixes ♦ pico: trillionth 10-12 0.000000000001 ♦ nano: billionth 10-9 0.000000001 ♦ micro: millionth 10-6 0.000001 ♦ milli: thousandth 10-3 0.001 ♦ Kilo: thousand 103 1000 ♦ Mega: million 106 1000000 ♦ Giga: billion 109 1000000000 The Basics - Vocabulary
  14. 14. Mu Not Mooµ The Basics - Vocabulary
  15. 15. 1. The Basics VocabularyTransmitters & Receivers Signals
  16. 16. Transmitters & ReceiversAn Interesting Thing To Know ♦ An electrical signal can move from place to place two different ways: 1) As current on a conductor (e.g. a wire) 2) As invisible waves in the air The Basics - Transmitters & Receivers
  17. 17. Transmitters & ReceiversWireless Communications The Basics - Transmitters & Receivers
  18. 18. Transmitters & ReceiversWireless Communications The Basics - Transmitters & Receivers
  19. 19. Transmitters & ReceiversWireless Communications Transceiver The Basics - Transmitters & Receivers
  20. 20. 1. The Basics VocabularyTransmitters & Receivers Signals
  21. 21. SignalsThere Are Two Kinds Of Signals ♦ Analog: Can take any value ♦ Digital: Can take one of two values (high, low) The Basics - Signals
  22. 22. Analog SignalsA Very Special Analog Signal ♦ Sine wave: The Basics - Signals
  23. 23. Analog SignalsProperties Of A Sine Wave Speed The Basics - Signals
  24. 24. Analog SignalsProperties Of A Sine Wave Speed Frequency The Basics - Signals
  25. 25. Analog SignalsProperties Of A Sine Wave Speed Frequency (Hertz) The Basics - Signals
  26. 26. Analog SignalsProperties Of A Sine Wave Speed Amplitude Frequency (Hertz) The Basics - Signals
  27. 27. Analog SignalsProperties Of A Sine Wave Speed Amplitude Frequency (Hertz) Wavelength
  28. 28. Analog SignalsProperties Of A Sine Wave 90º Phase Speed Amplitude 360º 0º 180º Frequency (Hertz) 270º Wavelength
  29. 29. Analog SignalsA Special Relationship ♦ Frequency x Wavelength = Constant ∴When you know one you know the other ♦ The constant is usually the speed of light The Basics - Signals
  30. 30. Visual DepictionHigh frequency = Many waves Occurring frequently Close together The Basics - Signals
  31. 31. Visual DepictionLow frequency = Few waves Occurring infrequently Far apart The Basics - Signals
  32. 32. Analog SignalsWhat Makes Sine Waves Special? ♦ Every analog signal is just a summation of multiple sine waves
  33. 33. Analog SignalsWhy Is All Of This Important? 1) Because everything in the wireless world is frequency dependent • Components are specified over certain frequencies • Applications are specified over certain frequencies 2) And because it is sine waves that travel through the air as invisible waves The Basics - Signals
  34. 34. Analog Signals Frequency (Hertz) ApplicationFrequencies 60 Electrical wall outletOf 2,000 The human voiceSome 530,000 AM radioApplications 54,000,000 VHF television 88,000,000 FM radio 824,000,000 Cellular phones 1,850,000,000 PCS phones 11,700,000,000 DirectTV™
  35. 35. Analog Signals Wavelength (meters) ApplicationWavelengths 5,000,000 Electrical wall outletOf 152,500 The human voiceSome 566 AM radioApplications 5 VHF television 3 FM radio 0.3 Cellular phones 0.1 PCS phones 0.02 DirectTV™
  36. 36. Analog SignalsFrequency Band Frequency Range L-Band 1 – 2 GHzBands S-Band 2 – 4 GHz C-Band 4 – 8 GHz X-Band 8 – 12 GHz K-Band 12 – 40 GHz The Basics - Signals
  37. 37. Analog Signals Term Frequency RangeFrequency RF Frequency Less Than 1 GHzRanges Microwave Frequency Between 1 GHz & 40 GHz Millimeter Wave Frequency Greater Than 40 GHz The Basics - Signals
  38. 38. Digital SignalsAn Example Of A Digital Signal The Basics - Signals
  39. 39. Digital Signals Properties Of A Digital SignalAmplitude (0 or 1) The Basics - Signals
  40. 40. Digital Signals Properties Of A Digital SignalAmplitude (0 or 1) Frequency The Basics - Signals
  41. 41. Digital Signals Properties Of A Digital SignalAmplitude (0 or 1) Frequency = Data Rate The Basics - Signals
  42. 42. Digital Signals Properties Of A Digital SignalAmplitude (0 or 1) Frequency = Data Rate (bits/second) The Basics - Signals
  43. 43. Analog vs DigitalAnalog Signals ♦ Occur naturally ♦ Represent information AND ♦ Travel through the air as invisible wavesDigital Signals ♦ Are man made ♦ Represent information only
  44. 44. Analog to Digital ConversionHow Is ItDone?
  45. 45. Digital Data RateHuman Voice ♦ Highest frequency = 4000 HzSample Rate ♦ Twice the highest frequency = 8000 samples/secGranularity ♦ 8 bits/sampleData Rate ♦ 8 (bits/sample) X 8000 (samples/sec) = 64 Kbps
  46. 46. Analog vs DigitalAnalog Signals ♦ Advantages: Can travel wirelessly ♦ Disadvantages: Susceptible to noiseDigital Signals ♦ Advantages: Noise resistant, compression ♦ Disadvantages: Expensive RF hardware The Basics - Signals
  47. 47. The Basics The end
  48. 48. Module 1 1. The Basics2. RF Behavior 3. Modulation 4. Noise
  49. 49. 2. RF Behavior Loss & Gain Decibels BandwidthRF in the Environment Match
  50. 50. 2. RF Behavior Loss & Gain Decibels BandwidthRF in the Environment Match
  51. 51. Energy Is Conserved
  52. 52. DevicesTwo Types Heat Power Supply Gain Heat Loss
  53. 53. Loss & GainVocabulary ♦ Gain: Also called amplification & power gain ♦ Loss: Also called insertion loss & attenuation RF Behavior - Loss & Gain
  54. 54. Loss & GainComponent Active PassivePossibilities Gain “Amplifier” Impossible Loss Many Many RF Behavior - Loss & Gain
  55. 55. Loss & GainAre Cumulative Total gain = 100 RF Behavior - Loss & Gain
  56. 56. 2. RF Behavior Loss & Gain Decibels BandwidthRF in the Environment Match
  57. 57. DecibelsWhats The Problem? 1000 Watts 0.000000000001 Watts RF Behavior - Decibels
  58. 58. DecibelsDefinition Decibels = 10 x log10(Pout/Pin) RF Behavior - Decibels
  59. 59. DecibelsThe Basics ♦ Measure a change (e.g. output vs input) ♦ Bigger (i.e, gain), decibels are positive ♦ Smaller (i.e., loss) , decibels are negative ♦ Decibels are abbreviated "dB" RF Behavior - Decibels
  60. 60. DecibelsThe Only Math Youll Need To Know ♦ +3dB means 2 times bigger ♦ +10 dB means 10 times bigger ♦ -3dB means 2 times smaller ♦ -10 dB means 10 times smaller ♦ Add and subtract decibels only RF Behavior - Decibels
  61. 61. Decibel Conversion ExamplesChange Factors Decibels 4000 2 x 2 x 10 x 10 x 10 3+3+10+10+10=36 dB -4000 -36 dB 5000 10 x 10 x 10 x 10 ÷ 2 10+10+10+10-3=37 dB 8000 2 x 4000 36 dB + 3 dB = 39 dB 6000 37.5 dB ≈ 37. 78 dB RF Behavior - Decibels
  62. 62. Summing DecibelsRecall From Before Total gain = 100 RF Behavior - Decibels
  63. 63. Summing DecibelsNow With dB 10 dB 10 dB Gain Gain Total gain = 20 dB RF Behavior - Decibels
  64. 64. Summing DecibelsOne More Example Total change = +19 dB RF Behavior - Decibels
  65. 65. dBmWhat Is It? ♦ A measure of power NOT changeIn The RF World ♦ The "standard" unit of power is 1 milliwattDefinition ♦ dBm = "dB above 1 milliwatt" RF Behavior - Decibels
  66. 66. dBmExample Gain of device = 30 dB "Change" Output of device = 30 dBm "Power" Output = 30 dB above 1 milliwatt = 30 dBm RF Behavior - Decibels
  67. 67. dBm Conversion
  68. 68. dBm Recall From Before0 dBm 19 dBm Input = 0 dBm = 1 milliwatt Total change = +19 dB Output = 19 dBm ≈ 100 milliwatts RF Behavior - Decibels
  69. 69. dBm Another Example20 dBm 39 dBm Input = 20 dBm = 100 milliwatt Total change = +19 dB Output = 39 dBm ≈ 10 watts RF Behavior - Decibels
  70. 70. 2. RF Behavior Loss & Gain Decibels BandwidthRF in the Environment Match
  71. 71. BandwidthWhat Is It? ♦ A range of frequencies (in Hertz) ♦ Defined by the highest & lowest frequencyWhere Is It Used? ♦ Components ♦ Wireless applications RF Behavior - Bandwidth
  72. 72. BandwidthExample 1 An amplifier provides 30 dB of gain from 75 MHz to 125 MHz. What is its bandwidth? Highest frequency = 125 MHz Lowest frequency = 75 MHz Difference = 50 MHz = Bandwidth RF Behavior - Bandwidth
  73. 73. BandwidthExample 2 Cellular telephony in the US operates between 824 MHz and 894 MHz. What is the bandwidth? Highest frequency = 894 MHz Lowest frequency = 824 MHz Difference = 70 MHz = Bandwidth RF Behavior - Bandwidth
  74. 74. Percentage Bandwidth (BW)What Is It? ♦Another way to describe bandwidthHow To Calculate It (from previous example) 1. Bandwidth = 70 MHz 2. Ave frequency = (824 + 894)/2 = 859 MHz 3. %BW = 70 MHz/859 MHz x 100% = 8% RF Behavior - Bandwidth
  75. 75. BandwidthWays To Describe It ♦Narrowband: %BW < 50% ♦Wideband: %BW > 50% ♦Octave: Highest frequency = 2x lowest frequency ♦Decade: Highest frequency = 10x lowest frequency RF Behavior - Bandwidth
  76. 76. 2. RF Behavior Loss & Gain Decibels BandwidthRF in the Environment Match
  77. 77. RF In The EnvironmentFree Space Loss Skin Effect Absorption Reflection
  78. 78. RF In The EnvironmentFree Space Loss Skin Effect Absorption Reflection
  79. 79. Free Space LossRF signals spread out as they travel through the air Power density: Watts per square meter RF Behavior - RF In The Environment
  80. 80. Free Space Loss (FSL)Formula FSL = A function of frequency & distance FSL > 120 dB RF Behavior - RF In The Environment
  81. 81. Free Space LossRecall From Before 1000 Watts RF Behavior - RF In The Environment
  82. 82. Free Space LossRecall From Before 60 dBm Free Space Loss = 120 dB RF Behavior - RF In The Environment
  83. 83. Free Space LossRecall From Before 60 dBm -120 dB RF Behavior - RF In The Environment
  84. 84. Free Space LossRecall From Before 60 dBm - 60 dBm -120 dB RF Behavior - RF In The Environment
  85. 85. Free Space LossRecall From Before 60 dBm Free Space Loss = 120 dB - 60 dBm RF Behavior - RF In The Environment
  86. 86. RF In The EnvironmentFree Space Loss Skin Effect Absorption Reflection
  87. 87. Skin EffectWhat Is It? ♦ When an RF signal is on a conductor, it resides only on the surface Signal on the surface No signal inside RF Behavior - RF In The Environment
  88. 88. Skin EffectWhat Is The Implication? ♦ RF signals cant penetrate conductors (e.g. metal) ∴Metal can be used to control airborne RF waves RF Behavior - RF In The Environment
  89. 89. RF In The EnvironmentFree Space Loss Skin Effect Absorption Reflection
  90. 90. AbsorptionWhat Is It? ♦ When RF waves travel through the air, some things they encounter cause attenuation • Air • Rain • Foliage RF Behavior - RF In The Environment
  91. 91. AbsorptionAnd ♦ Absorbed energy gets converted to heat Heat RF Behavior - RF In The Environment
  92. 92. AbsorptionLook Familiar? Heat RF Behavior - RF In The Environment
  93. 93. AbsorptionWhat Else? ♦ Also called atmospheric attenuation ♦ Measured in dB Heat RF Behavior - RF In The Environment
  94. 94. AtmosphericAttenuation
  95. 95. AbsorptionRecall From Before Output Power Free Space Loss Absorption RF Behavior - RF In The Environment
  96. 96. RF In The EnvironmentFree Space Loss Skin Effect Absorption Reflection
  97. 97. ReflectionWhat Is It? ♦ When RF waves travel through the air, some things they encounter cause the signal to be reflected • Buildings • Mountains • Automobiles
  98. 98. ReflectionIn Fact ♦ Some materials reflect the RF completely • Metal ♦ Some reflect the RF only partially • Wood • Concrete RF Behavior - RF In The Environment
  99. 99. ReflectionWhat Does Than Mean? ♦ Some materials absorb AND reflect RF waves RF Behavior - RF In The Environment
  100. 100. Reflection & AbsorptionVisual Depiction Heat Incident wave Transmitted wave Reflected wave
  101. 101. RecapFree space loss Due to signal spreading outSkin effect Signal on surface of conductorAbsorption Due to the environmentReflection Signal direction changes
  102. 102. 2. RF Behavior Loss & Gain Decibels BandwidthRF in the Environment Match
  103. 103. MatchImpedance ♦ Components have impedance ♦ Conductors have impedance ♦ Conductors connect components RF Behavior - Match
  104. 104. MatchImpedance ♦ Components & conductors should have the same impedance • 50 ohms ♦ But they dont • Their impedances dont "match" RF Behavior - Match
  105. 105. MatchWhy Dont Things Match? ♦ Different standards • 50 ohms in the RF world • 75 ohms in the video world ♦ Impedance varies • Over frequency • From unit to unit RF Behavior - Match
  106. 106. MismatchWhat Are The Consequences? ♦ The RF signal gets reflected • The bigger the mismatch, the greater the reflection ♦ If too much signal gets reflected • Adverse effects RF Behavior - Match
  107. 107. Mismatch Good matchIncident signalReflected signal Poor matchIncident signalReflected signal RF Behavior - Match
  108. 108. MatchHow Is Match Measured? ♦ Two ways • VSWR (Voltage Standing Wave Ratio) • Return loss (RL) RF Behavior - Match
  109. 109. VSWRVSWR Meaning1.0:1 Perfect match1.4:1 Excellent match2.0:1 Good match10:1 Poor match∞:1 Special cases RF Behavior - Match
  110. 110. VSWR Special Cases∞:1 (VSWR is infinite) 1) Perfect open • Conductor/component left unattached 2) Perfect short • Conductor/component short circuited ALL RF ENERGY REFLECTED RF Behavior - Match
  111. 111. Return LossMeaning ♦ "The loss that the return (reflected) signal experiences" • Big RL = small reflected signal Good • Small RL = big reflected signal Bad ♦ Measured in dB • Just like insertion loss RF Behavior - Match
  112. 112. Return Loss Good matchIncident signalHigh RLReflected signal Poor matchIncident signal Low RLReflected signal RF Behavior - Match
  113. 113. Return Loss vs VSWR VSWR Return Loss 1.0:1 ∞ 1.4:1 15.6 dB 2.0:1 9.5 dB 10:1 1.7 dB ∞ :1 0 dB RF Behavior - Match
  114. 114. MismatchHow To Deal With Mismatch ♦ If the mismatch is small • Do nothing ♦ If the mismatch is large • Impedance matching circuit RF Behavior - Match
  115. 115. Impedance Matching Impedance matching circuit75 ohms 50 ohms RF Behavior - Match
  116. 116. RF Behavior The end
  117. 117. Module 1 1. The Basics2. RF Behavior3. Modulation 4. Noise
  118. 118. 3. Modulation How RF Carries InformationAM FM PM QAM
  119. 119. 3. Modulation How RF Carries InformationAM FM PM QAM
  120. 120. How RF Carries InformationWireless Communications ♦ Transmitting information wirelessly requires TWO different signals 1. Information signal (analog or digital) 2. RF signal (sine wave) or "carrier"
  121. 121. How RF Carries InformationModulation ♦ Combining an information signal and a carrier signal
  122. 122. How RF Carries InformationModulation Result ♦ One signal - the carrier ♦ The carrier is manipulated to reflect the imparted information • Amplitude • Frequency • Phase Modulation - How RF Carries Information
  123. 123. How RF Carries InformationDemodulation ♦ Separating the information signal from the carrier • The carrier is then"discarded" Modulation - How RF Carries Information
  124. 124. How RF Carries InformationHow Is It Done? ♦ Modulator: An RF component that combines an information signal & a carrier ♦ Demodulator: An RF component that separates an information signal from a carrier Modulation - How RF Carries Information
  125. 125. How RF Carries InformationWhere Is It Done? Modulation - How RF Carries Information
  126. 126. How RF Carries InformationWhere Is It Done? Modem Modulation - How RF Carries Information
  127. 127. How RF Carries InformationWhere Is It Done? Radio Modulation - How RF Carries Information
  128. 128. 3. Modulation How RF Carries InformationAM FM PM QAM
  129. 129. Amplitude Modulation (AM)Definition ♦ Imparting information onto a sine wave by varying the amplitude Amplitude
  130. 130. Amplitude Modulation (AM)Types ♦ AM: "Analog" amplitude modulation • Information signal is analog ♦ BASK: Binary amplitude shift keying- "digital" amplitude modulation • Information signal is digital Modulation - AM
  131. 131. AMExample Modulation - AM
  132. 132. BASKExample Modulation - AM
  133. 133. 3. Modulation How RF Carries InformationAM FM PM QAM
  134. 134. Frequency Modulation (FM)Definition ♦ Imparting information onto a sine wave by varying the frequency Frequency
  135. 135. Frequency Modulation (FM)Types ♦ FM: "Analog" frequency modulation • Information signal is analog ♦ FSK: Frequency shift keying- "digital" frequency modulation • Information signal is digital Modulation - FM
  136. 136. FMExample Modulation - FM
  137. 137. FSKExample Modulation - FM
  138. 138. 3. Modulation How RF Carries InformationAM FM PM QAM
  139. 139. Phase Modulation (PM)Definition ♦ Imparting information onto a sine wave by shifting the phase of successive sine waves 90º Phase 360º 0º 180º 270º
  140. 140. Phase ShiftWhat Is It? ♦ Successive sine waves starting at a different point on the sine wave • Measured with respect to the previous sine wave Modulation - PM
  141. 141. 90° Phase ShiftIn Action Phase shift: 0°
  142. 142. 90° Phase ShiftIn Action Phase shift: 0°
  143. 143. 90° Phase ShiftIn Action Phase shift: 0°
  144. 144. 90° Phase ShiftIn Action Phase shift: 0°
  145. 145. 90° Phase ShiftIn Action Phase shift: 0°
  146. 146. 90° Phase ShiftIn Action Phase shift: 90°
  147. 147. Phase Modulation (PM)Types ♦ PM is digital modulation ONLY • Information signal is digital ♦ Many different types • BPSK: Binary phase shift keying • QPSK: Quadrature phase shift keying Modulation - PM
  148. 148. Phase ShiftHow Does It Represent Digital Info? ♦ "0" = 0° phase shift ♦ "1" = 180° phase shift Phase shift: 0° Digital bit: 0
  149. 149. Phase ShiftHow Does It Represent Digital Info? ♦ "0" = 0° phase shift ♦ "1" = 180° phase shift Phase shift: 180° Digital bit: 1
  150. 150. BPSKExample Modulation - PM
  151. 151. Phase ShiftIt Can Represent More Information ♦ "00" = 0° shift ♦"10" = 180° shift ♦ "01" = 90° shift ♦"11" = 270° shift Phase shift: 0° Digital bit: 00
  152. 152. Phase ShiftIt Can Represent More Information ♦ "00" = 0° shift ♦"10" = 180° shift ♦ "01" = 90° shift ♦"11" = 270° shift Phase shift: 90° Digital bit: 01
  153. 153. Phase ShiftIt Can Represent More Information ♦ "00" = 0° shift ♦"10" = 180° shift ♦ "01" = 90° shift ♦"11" = 270° shift Phase shift: 180° Digital bit: 10
  154. 154. Phase ShiftIt Can Represent More Information ♦ "00" = 0° shift ♦"10" = 180° shift ♦ "01" = 90° shift ♦"11" = 270° shift Phase shift: 270° Digital bit: 11
  155. 155. QPSKExample Modulation - PM
  156. 156. QPSKExample Modulation - PM
  157. 157. QPSKExample Modulation - PM
  158. 158. QPSKExample Modulation - PM
  159. 159. QPSKExample Modulation - PM
  160. 160. 3. Modulation How RF Carries InformationAM FM PM QAM
  161. 161. Quadrature Amplitude Modulation (QAM)What Is It? ♦ A combination of amplitude shift keying and phase shift keying • For digital information signals only ♦ Several different kinds • QAM-8 • QAM-16 • QAM-64 Modulation - QAM
  162. 162. QAM - 8How Does It Represent Digital Info? ♦ Amplitude shift keying (BASK) • "0" = low • "1" = high ♦ Phase shift keying (QPSK) • "00" = 0° • "01" = 90° • "10" = 180° • "11" = 270° Modulation - QAM
  163. 163. QAM - 8Example Modulation - QAM
  164. 164. QAM - 8Example Modulation - QAM
  165. 165. QAM - 8Example Modulation - QAM
  166. 166. Spectral EfficiencyBits/Second/Hertz ♦ BPSK: 1 bps/Hz ♦ QPSK: 2 bps/Hz ♦ QAM: 3 bps/Hz
  167. 167. RecapModulation Analog Digital AM “AM” BASK FM “FM” FSK PM N/A BPSK QPSK QAM N/A BASK+ QPSK
  168. 168. Modulation The end
  169. 169. Module 11. The Basics2. RF Behavior3. Modulation 4. Noise
  170. 170. 4. Noise What Is It?Link BudgetNoise Effects
  171. 171. 4. NoiseWhat Is It?Link BudgetNoise Effects
  172. 172. NoiseWhat Is It? ♦ Signal disturbance ♦ Unwanted signal(s), also called interferenceWhere Does It Come From? ♦ Environment ♦ Man made Noise - What is it
  173. 173. NoiseTypes ♦ AM: Unwanted changes to the amplitude • Predominantly environment ♦ FM: Unwanted changes to the frequency • Predominantly hardware ♦ PM: Unwanted changes to the phase • Predominantly hardware Noise - What is it
  174. 174. NoiseA Function Of Bandwidth & Temperature ♦ Noise density ♦ "Noise floor” • Thermal noise -120 dBm Noise - What is it
  175. 175. 4. Noise What Is It?Link BudgetNoise Effects
  176. 176. Signal To Noise Ratio (S/N)Definition ♦ A measure (in dB) of how much bigger the received signal is relative to the noise floor • AM: 40-50 dB • FM: 20-30 dB Receiver sensitivity • Digital: 10-20 dB Noise - Link budget
  177. 177. Link BudgetPower out 40 dBm Free space loss 120 dB -80 dBm Absorption 10 dB -90 dBm S/N 30 dBNoise floor -120 dBm
  178. 178. Link BudgetNoise Spectrum Signal Spectrum
  179. 179. Shannon’s TheoremMaximum Data Rate ♦ A function of bandwidth ♦ A function of S/N ratio Noise - Link budget
  180. 180. 4. Noise What Is It? Link BudgetNoise Effects
  181. 181. Noise EffectsAnalog AM No noise Noise - Noise Effects
  182. 182. Noise EffectsAnalog AM Noise Noise - Noise Effects
  183. 183. Noise EffectsDigital AM No noise Noise - Noise Effects
  184. 184. Noise EffectsDigital AM Noise Noise - Noise Effects
  185. 185. Noise EffectsPhase Modulation ♦ Unwanted phase shift (e.g., 45°) BPSK QPSK 0 0° 00 0° 45° 45° 1 180° 01 90° ♦ Shows up as increased Bit Error Rate (BER) Noise - Noise Effects
  186. 186. NoiseThe end
  187. 187. Module 1 - Introduction To RF The end

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