4. Course Objectives
Explain
♦ RF signal behavior
♦ System hardware makeup
♦ Wireless systems’ operation
Communicate
♦ Using over 300 terms
Have Fun
5. Daily Schedule
8:30 am – 10: 00 am Fun
10:00 am – 10:15 am Break
10:15 am – 11:45 am Fun
Noon – 1:00 pm Lunch
1:00 pm – 2:30 pm Fun
2:30 pm – 2:45 pm Break
2:45 pm – 4:15 pm Fun
6. Course Agenda
Day One
• Morning (Module 1)
– Introduction to RF
• Afternoon (Module 2)
– RF hardware
Day Two
• Morning (Module 3)
– Older systems & mobile telephony
• Afternoon (Module 4)
– Newer systems & the future
7. Module 1 - Introduction To RF
1. The Basics
2. RF Behavior
3. Modulation
4. Noise
9. 1. The Basics
Vocabulary
Transmitters & Receivers
Signals
10. 1. The Basics
Vocabulary
Transmitters & Receivers
Signals
11. Vocabulary
Electronics 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. Vocabulary
More 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
15. 1. The Basics
Vocabulary
Transmitters & Receivers
Signals
16. Transmitters & Receivers
An 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
28. Analog Signals
Properties Of A Sine Wave
90º Phase
Speed
Amplitude 360º
0º 180º Frequency
(Hertz)
270º
Wavelength
29. Analog Signals
A 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
32. Analog Signals
What Makes Sine Waves Special?
♦ Every analog signal is just a summation of
multiple sine waves
33. Analog Signals
Why 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. Analog Signals
Frequency (Hertz) Application
Frequencies
60 Electrical wall outlet
Of 2,000 The human voice
Some 530,000 AM radio
Applications 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. Analog Signals
Wavelength (meters) Application
Wavelengths 5,000,000 Electrical wall outlet
Of 152,500 The human voice
Some 566 AM radio
Applications 5 VHF television
3 FM radio
0.3 Cellular phones
0.1 PCS phones
0.02 DirectTV™
36. Analog Signals
Frequency Band Frequency Range
L-Band 1 – 2 GHz
Bands S-Band 2 – 4 GHz
C-Band 4 – 8 GHz
X-Band 8 – 12 GHz
K-Band 12 – 40 GHz
The Basics - Signals
37. Analog Signals
Term Frequency Range
Frequency
RF Frequency Less Than 1 GHz
Ranges Microwave Frequency Between 1 GHz & 40 GHz
Millimeter Wave Frequency Greater Than 40 GHz
The Basics - Signals
39. Digital Signals
Properties Of A Digital Signal
Amplitude
(0 or 1)
The Basics - Signals
40. Digital Signals
Properties Of A Digital Signal
Amplitude
(0 or 1)
Frequency
The Basics - Signals
41. Digital Signals
Properties Of A Digital Signal
Amplitude
(0 or 1)
Frequency = Data Rate
The Basics - Signals
42. Digital Signals
Properties Of A Digital Signal
Amplitude
(0 or 1)
Frequency = Data Rate (bits/second)
The Basics - Signals
43. Analog vs Digital
Analog Signals
♦ Occur naturally
♦ Represent information AND
♦ Travel through the air as invisible waves
Digital Signals
♦ Are man made
♦ Represent information only
45. Digital Data Rate
Human Voice
♦ Highest frequency = 4000 Hz
Sample Rate
♦ Twice the highest frequency = 8000 samples/sec
Granularity
♦ 8 bits/sample
Data Rate
♦ 8 (bits/sample) X 8000 (samples/sec) = 64 Kbps
46. Analog vs Digital
Analog Signals
♦ Advantages: Can travel wirelessly
♦ Disadvantages: Susceptible to noise
Digital Signals
♦ Advantages: Noise resistant, compression
♦ Disadvantages: Expensive RF hardware
The Basics - Signals
59. Decibels
The 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. Decibels
The Only Math You'll 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. Decibel Conversion
Examples
Change 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
65. dBm
What Is It?
♦ A measure of power NOT change
In The RF World
♦ The "standard" unit of power is 1 milliwatt
Definition
♦ dBm = "dB above 1 milliwatt"
RF Behavior - Decibels
66. dBm
Example
Gain of device = 30 dB
"Change" Output of device = 30 dBm
"Power"
Output = 30 dB above 1 milliwatt = 30 dBm
RF Behavior - Decibels
68. dBm
Recall From Before
0 dBm 19 dBm
Input = 0 dBm = 1 milliwatt
Total change = +19 dB
Output = 19 dBm ≈ 100 milliwatts
RF Behavior - Decibels
69. dBm
Another Example
20 dBm 39 dBm
Input = 20 dBm = 100 milliwatt
Total change = +19 dB
Output = 39 dBm ≈ 10 watts
RF Behavior - Decibels
70. 2. RF Behavior
Loss & Gain
Decibels
Bandwidth
RF in the Environment
Match
71. Bandwidth
What Is It?
♦ A range of frequencies (in Hertz)
♦ Defined by the highest & lowest frequency
Where Is It Used?
♦ Components
♦ Wireless applications
RF Behavior - Bandwidth
72. Bandwidth
Example 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. Bandwidth
Example 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. Percentage Bandwidth (BW)
What Is It?
♦Another way to describe bandwidth
How 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. Bandwidth
Ways 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. 2. RF Behavior
Loss & Gain
Decibels
Bandwidth
RF in the Environment
Match
77. RF In The Environment
Free Space Loss
Skin Effect
Absorption
Reflection
78. RF In The Environment
Free Space Loss
Skin Effect
Absorption
Reflection
79. Free Space Loss
RF signals spread out as they travel through the air
Power density: Watts per square meter
RF Behavior - RF In The Environment
80. Free Space Loss (FSL)
Formula
FSL = A function of frequency & distance
FSL > 120 dB
RF Behavior - RF In The Environment
84. Free Space Loss
Recall From Before
60 dBm
- 60 dBm
-120 dB
RF Behavior - RF In The Environment
85. Free Space Loss
Recall From Before
60 dBm
Free Space Loss = 120 dB
- 60 dBm
RF Behavior - RF In The Environment
86. RF In The Environment
Free Space Loss
Skin Effect
Absorption
Reflection
87. Skin Effect
What 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. Skin Effect
What Is The Implication?
♦ RF signals can't penetrate conductors (e.g. metal)
∴Metal can be used to control airborne RF waves
RF Behavior - RF In The Environment
89. RF In The Environment
Free Space Loss
Skin Effect
Absorption
Reflection
90. Absorption
What Is It?
♦ When RF waves travel through the air, some
things they encounter cause attenuation
• Air
• Rain
• Foliage
RF Behavior - RF In The Environment
96. RF In The Environment
Free Space Loss
Skin Effect
Absorption
Reflection
97. Reflection
What Is It?
♦ When RF waves travel through the air, some
things they encounter cause the signal to be
reflected
• Buildings
• Mountains
• Automobiles
98. Reflection
In Fact
♦ Some materials reflect the RF completely
• Metal
♦ Some reflect the RF only partially
• Wood
• Concrete
RF Behavior - RF In The Environment
99. Reflection
What Does Than Mean?
♦ Some materials absorb AND reflect RF waves
RF Behavior - RF In The Environment
101. Recap
Free space loss Due to signal spreading out
Skin effect Signal on surface of conductor
Absorption Due to the environment
Reflection Signal direction changes
102. 2. RF Behavior
Loss & Gain
Decibels
Bandwidth
RF in the Environment
Match
103. Match
Impedance
♦ Components have impedance
♦ Conductors have impedance
♦ Conductors connect components
RF Behavior - Match
104. Match
Impedance
♦ Components & conductors should have the same
impedance
• 50 ohms
♦ But they don't
• Their impedances
don't "match"
RF Behavior - Match
105. Match
Why Don't 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. Mismatch
What 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. Mismatch
Good match
Incident signal
Reflected signal
Poor match
Incident signal
Reflected signal
RF Behavior - Match
108. Match
How Is Match Measured?
♦ Two ways
• VSWR (Voltage Standing Wave Ratio)
• Return loss (RL)
RF Behavior - Match
109. VSWR
VSWR Meaning
1.0:1 Perfect match
1.4:1 Excellent match
2.0:1 Good match
10:1 Poor match
∞:1 Special cases
RF Behavior - Match
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. Return Loss
Meaning
♦ "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. Return Loss
Good match
Incident signal
High RL
Reflected signal
Poor match
Incident signal
Low RL
Reflected signal
RF Behavior - Match
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. Mismatch
How To Deal With Mismatch
♦ If the mismatch is small
• Do nothing
♦ If the mismatch is large
• Impedance matching circuit
RF Behavior - Match
120. How RF Carries Information
Wireless Communications
♦ Transmitting information wirelessly requires
TWO different signals
1. Information signal (analog or digital)
2. RF signal (sine wave) or "carrier"
121. How RF Carries Information
Modulation
♦ Combining an information
signal and a carrier signal
122. How RF Carries Information
Modulation Result
♦ One signal - the carrier
♦ The carrier is manipulated to reflect the
imparted information
• Amplitude
• Frequency
• Phase
Modulation - How RF Carries Information
123. How RF Carries Information
Demodulation
♦ Separating the information signal
from the carrier
• The carrier is then"discarded"
Modulation - How RF Carries Information
124. How RF Carries Information
How 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. How RF Carries Information
Where Is It Done?
Modulation - How RF Carries Information
126. How RF Carries Information
Where Is It Done?
Modem
Modulation - How RF Carries Information
127. How RF Carries Information
Where Is It Done?
Radio
Modulation - How RF Carries Information
128. 3. Modulation
How RF Carries Information
AM FM PM QAM
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
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
138. 3. Modulation
How RF Carries Information
AM FM PM QAM
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. Phase Shift
What Is It?
♦ Successive sine
waves starting at a
different point on
the sine wave
• Measured with
respect to the
previous sine wave
Modulation - PM
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. Phase Shift
How Does It Represent Digital Info?
♦ "0" = 0° phase shift
♦ "1" = 180° phase shift
Phase shift: 0°
Digital bit: 0
149. Phase Shift
How Does It Represent Digital Info?
♦ "0" = 0° phase shift
♦ "1" = 180° phase shift
Phase shift: 180°
Digital bit: 1
160. 3. Modulation
How RF Carries Information
AM FM PM QAM
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. QAM - 8
How 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
172. Noise
What Is It?
♦ Signal disturbance
♦ Unwanted signal(s), also called interference
Where Does It Come From?
♦ Environment
♦ Man made
Noise - What is it
173. Noise
Types
♦ 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. Noise
A Function Of Bandwidth & Temperature
♦ Noise density
♦ "Noise floor”
• Thermal noise
-120 dBm
Noise - What is it
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. Link Budget
Power out 40 dBm
Free space loss 120 dB
-80 dBm
Absorption 10 dB
-90 dBm
S/N 30 dB
Noise floor -120 dBm