coaxial architecture. tree-and-branch architecture express trunk
TRANSCRIPT
Coaxial ArchitectureCoaxial Architecture
Tree-and-Branch ArchitectureTree-and-Branch Architecture
Express Trunk
HFC ArchitectureHFC Architecture
Tap
node
HUBS
Businessesamp in building
Customer Homes
Headend (Node) Optics RX/TX
Active Device
Fiber Optic Cable
RF
Other cable outputs
Rural NetworkRural Network
Headendor Node
Optics RX/TX
LPI
LPS
1411
24 21Two-Way Tap
Four-Way Tap
Eight-Way Tap
Near Passive NetworkNear Passive Network
Directional Coupler
Splitter
17
26
29
29
Passive NetworkPassive Network
Slope Equalizer
Two Way Tap
Four Way Tap
Headendor Node Node
29
17
4
2023 17
11
26
Sample HeadendSample Headend
DT 815 Amp
out
HubEDFA
EDFA
Return TX
Return TX
DWDM
HUB
1
23
5008ET2
Public switch
Com21 Analog Video55-550 MHz
HCX comController
2 W
ayR
Fs
plit
ter
2 WayRF splitter
430MHz
DWDD
2RRX
2RRX
Connector PartsConnector Parts
BootBody
Ferrule
Types of ConnectorsTypes of Connectors
Biconic FC
D4SC
ST
Optical Loss ExampleOptical Loss Example
Optical Transmitters and Optical Transmitters and ReceiversReceivers
Coaxial Plant DesignCoaxial Plant Designand Operationand Operation
TopicsTopics
• Overview
• Optical Transmitters
• Optical Receivers
• Units of Optical Power
• Power Budget
Optical Transmitter and ReceiverOptical Transmitter and Receiver
Input ElectricalInput ElectricalSignalSignal
Input ElectricalInput ElectricalSignalSignal
Reproduced Reproduced Electrical Electrical
SignalSignal
Reproduced Reproduced Electrical Electrical
SignalSignal
Optical FiberOptical FiberOptical FiberOptical Fiber
ReceiverReceiver ReceiverReceiver
Optical SignalOptical SignalOptical SignalOptical Signal
TransmitterTransmitterTransmitterTransmitter
Optical Fiber
Laser
OpticalConnector
Drive LevelControlRF Input
Drive LevelTest Point
Optical TransmitterOptical Transmitter
BiasCurrent
ModulatedOptical Output
ThresholdCurrent
Input RF
Current
Opt
ical
Out
put P
ower
Laser Performance
Curve
Laser Drive LevelsLaser Drive Levels
Clipped Output
Bias Voltage
PreAmp
PostAmp
RFOut
Test Point
Fiber
OpticalConnector
Photo Detector
Optical ReceiverOptical Receiver
Units of Optical PowerUnits of Optical Power
Optical Power EquationsOptical Power Equations
dBm = 10 log mW
mW = inverse log (dBm/10)
+/-10dB Optical Power Table+/-10dB Optical Power Table
Optical Power (dBm) Optical Power (mW)30 1,00020 10010 10 0 1
-10 0.1 -20 0.01
-30 0.001
Power Budget FormulaPower Budget Formula
P b = T p - Rin where
P b = the Power Budget
T p = output Power of the Transmitter and
R in = required input to the receiver
Optical NodeOptical Node
NOR NRT
System RF out
Optical Node OperationOptical Node OperationOptical Node OperationOptical Node Operation
Node/Amplifier Block DiagramNode/Amplifier Block Diagram
Light Light to RFto RF
ConverterConverterLevelLevel
ControlControlAttenuatorAttenuator Tilt Tilt
GeneratorGenerator
PrePreAmpAmp
Split
ter
Split
ter
PostPostAmpAmp
PostPostAmpAmp
PostPostAmpAmp
PostPostAmpAmp
HH
LL
HH
LL
HH
LL
HH
LLCombinerCombiner
RF toRF toLight Light
ConverterConverterto RFto RF
-20 dB-20 dB Rf TPRf TP2020
dBmVdBmV
9Apad
-30 downTest Point
RFGainadjust
Opticalalarm
Opticalmonitoring T/P
Forward Optical Receivers/NOR’S
Diamond Net RF Module
Amplifier Technology
Coaxial Plant DesignCoaxial Plant Designand Operationand Operation
TopicsTopics
• Semiconductor Configurations in CATV–Single - Ended Amplifier–Push - Pull Amplifier–Parallel - Hybrid Amplifier
Semiconductor Amplifier Semiconductor Amplifier ConfigurationsConfigurations
2nd Harmonicplus Noise
Single - Ended AmplifierSingle - Ended Amplifier
Push - Pull AmplifierPush - Pull Amplifier
PushPullStage
PushPullStage
ADVANTAGES: High Gain and Reduced DistortionsADVANTAGES: High Gain and Reduced Distortions
Parallel - Hybrid AmplifierParallel - Hybrid Amplifier
Pin Pout
Amplifier Configurations
Coaxial Plant DesignCoaxial Plant Designand Operationand Operation
• Describe the most common amplifier configurations and discuss their usage.
• Identify the components for each of the amplifier configuration and explain their functions and importance.
ObjectivesObjectives
Forward Amplifier CharacteristicsForward Amplifier Characteristics
Amplifier Output TiltAmplifier Output Tilt
11dB of tilt @ 750 MHz
50 MHz 750 MHz0 dBmV
20 dBmV
10 dBmV
0 dBmV
20 dBmV
10 dBmV
50 MHz 750 MHz
Attenuator FunctionAttenuator Function
0 dBmV
20 dBmV
10 dBmV
50 MHz 750 MHz
Effect of Cable
20 dB
0 dB
10 dB
50 MHz 750 MHz
Effect of Equalizer
10 dBmV
50 MHz 750 MHz
Combined Results
Equalizer FunctionEqualizer Function
Response EqualizerResponse Equalizer
Examples of Peak to ValleyResponses. With ResponseEqualizers Installed
These are available in either bumps or traps
Equalizer SelectionEqualizer Selection
= = =
Interstage Eq Set fordesired Tilt @ Output
Secondary Eq Set Additional Tilt 50 MHz 750
MHz
20 dB
12 dB
62E750/11
11 dB
8 dB
50 MHz 750 MHz
11 dB
PostAmp
Hig
hL
owH
igh
Low
DCTP
ShortingStub to OneSecondary orDC 4-8-or 12
Pad
Hig
hL
ow
InputAtten
InputEQ
PreAmp
DCTP
ManualGain Adj.
ResponseEqualizer
Interstage Slope Eq.
ALSC Optional Plug In
InterStageAmp
DistEQ
Hig
hL
ow
Interstage Atten.
DCTP
Pad
PostAmp
Amplifier Block Diagram withAmplifier Block Diagram withALSC / AGCALSC / AGC
Forward Amplifier CharacteristicsForward Amplifier Characteristics
Forward SweepForward Sweep
SYSTEM AMPLIFIER
METER
SWEEP GEAR
Sweep System RequirementsSweep System Requirements
HeadendCombiner
Sweep Transmitter
Fiber Transmitter
Node
Fiber Optic Interconnect
AMP 1
ReferenceAmp 2
Amp 3
Amp 4
Amp 5
Amp 6
*The remaining amplifiers in the cascade are compared to the reference.
Raw SweepRaw SweepB
EF
OR
EA
FT
ER
Low Level Signal TelemetryLow Level Signal Telemetry
Frequency Response Specifics
Coaxial Plant DesignCoaxial Plant Designand Operationand Operation
550MHz50 MHz
Sign
al L
evel
Ideal Response
50 MHz 550MHzSi
gnal
Lev
el
Cable KinksZ Mismatch
Non Linear
Non Linear Cable Loss Non Linear Cable Loss Characteristics Characteristics
Hardware Points of ConcernHardware Points of Concern
AmplifierAmplifier
ConnectorCable
Tap
Cable
Cable
Connector
Frequency CharacteristicsFrequency Characteristics
Peak to Valley Peak to Valley
Impedance Mismatch Impedance Mismatch
RF Suckout RF Suckout
Low End LossLow End Loss
Correcting the Characteristics of Correcting the Characteristics of an Amplifier Signaturean Amplifier Signature
Correcting the Characteristics of Correcting the Characteristics of an Amplifier Signaturean Amplifier Signature
7507505454
BeforeBefore
AfterAfter
Forward Amplifier CharacteristicsForward Amplifier Characteristics
L
Automatic GainControl(AGC series
plug-in) Optional
Thermal Control(TGSC plug-in)
Optional
Thru PowerPlug
PowerSupply +24 VDC
+24 VDCTest Point
SurgeArrestor
SurgeArrestor
ACAC
Return Amplifier ModuleLER series plug-in
OptionalReturn RF
Input/
H
L
Pre-AmpAtten. Equalizer
Test Point-30 dB Resistive
Upstream
Downstream
Output
Post-Amp
Test Point-30 dB Resistive
DownstreamOutput/
UpstreamInput
H
L
Forward Amplifier CharacteristicsForward Amplifier Characteristics
+32.5/29 dBmV+38.0/31.5 dBmV
+ 43.1 dBmV33.6 dBmV
17dB-1.5
20dB-1.0dB
23dB-0.6dB
Cable Losses
@870 MHz= 1.5dB/100ft
@50 MHz=0.5dB/100ft
29dB-0.4
+48/35.5
Forward Amplifier CharacteristicsForward Amplifier Characteristics
Needs a minimumof 8dBMv at 870MHz
40dB gain
Each port has19/6.5dBmV out
Each port has15.5/12dBmV out.
14dB2.0
11dB-3.5
Input=11/17.7dB
Network Operation and Network Operation and Maintenance ProceduresMaintenance Procedures
Intermodulation Distortions
Coaxial Plant DesignCoaxial Plant Designand Operationand Operation
Distortion Cause: AmplifiersDistortion Cause: Amplifiers55.25MHz55.25MHz
FFss Amp Amp
110.5MHz110.5MHz
FFss++
FFss
VVCCCC2 F2 Fss
2nd Harmonic2nd Harmonic
Intermodulation DistortionIntermodulation Distortion
2nd Order DistortionDiscrete Third OrderCross Modulation
DistortionsDistortions
Carrier 1Carrier 1 Carrier 2Carrier 2Carrier 1Carrier 1 Carrier 2Carrier 2ActiveActive
Beat Products = Carrier 1 +/- Carrier 2Beat Products = Carrier 1 +/- Carrier 2
Beat Product
Discrete Second Order DistortionsDiscrete Second Order Distortions
55.25 MHz 175.25 MHz
230.50 MHz
229.25 MHz
A+B
121.25 MHz
120.00 MHz
A-B
B
A
CSO Beats in a 77 Channel SystemCSO Beats in a 77 Channel System
50 100 200 300 400 500 550
10
20
30
40
50Subtraction Beats:CSO -F1, -F2, -F3
Addition BeatsCSO +F1, +F2, +F3
Frequency in MHz
NUMBER OF BEATS
60COMPOSITE SECOND ORDER (CSO)COMPOSITE SECOND ORDER (CSO)
• CSO( Single Amp.) = CSO(Spec.) + 2*(Rated Output-Actual Output)
68 + 2*(46 - 48) =
68 + 2*( -2 ) =
68 + -4 =
64 dBc
Beat Product
Beat Product = Carrier 1 +/- Carrier 2 +/- Carrier 3
Discrete Third OrderDiscrete Third Order
ActiveCarrier 1
Carrier 3Carrier 2
Composite Triple Beat DistortionsComposite Triple Beat Distortions
VideoAural
Channel A Un-modulated Carrier
Channel B
Channel A with Cross Modulation from Channel B
Cross ModulationCross Modulation
Multiple Amplifiers
CTB2Amps = 68- 20Log (2)CTB2Amps = 68- 20 x .3CTB2Amps = 62 dBc
This is true if all the amplifiers are identical.CTB is 20 Log because it is a voltage function.
2 Amplifiers
CTB#Amps = CTB1Amp - 20log (#Amps)
Composite Triple Beat Composite Triple Beat
Cross Modulation CalculationCross Modulation Calculation
• XMOD ( Cascade ) = –XMOD ( Single ) - 20Log ( N ) –where N is the number of amplifiers in cascade.