2005年ITU亚太地区监测业务培训-教材3

Monitoring
Law & Enforcement
Planning & allocating
Inspection
Spectrum Engineering
Licensing & Billing
Rules Regulations & associated standards
Frequency Coordinating
Which assignments need detailed analysis?
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Culling
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How to cull
Frequency criteria (frequency separation) Distance between interfering transmitter and victim receiver Local environment consideration
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How to eliminate Desensitization Interference
Horizontal or vertical separation of antenna Improve the selectivity of the receiver: -- insert band pass filter Select another frequency
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Table 5, Receiver Intermodulation Determination of Intermodulation Products
IM Product Im Product 1 Im Product 2 Im Product 3 Im Product 4 Im Product 5 Im Product 6 Im Product 7 Im Product 8 Im Product 9 Im Product 10 Fa 165.240 165.240 165.240 165.240 165.150 165.150 165.150 163.500 163.500 165.330 Fb 165.150 163.500 165.330 164.370 163.500 165.330 164.370 165.330 164.370 164.370 2Fa-Fb 165.330 166.980 165.150 166.110 166.800 164.970 165.930 165.670 162.630 166.290 2Fb-Fa 165.100 161.760 165.420 163.500 161.850 165.510 163.590 167.160 165.240 163.41
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Why we need EMC
Operators need clear spectrum All the system need co-exist peacefully Use Spectrum efficiently an effectively
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Overview
Interference Model Culling Propagation Interference Analysis
What is? How and when it occurs?
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Content
Interference Model Culling Propagation Interference Analysis
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Why perform a cull
In a frequency congested environment, the Spectrum Manager must use a valid and reliable means to identify potential interference problems which can occur between thousands of assigned frequencies in the area.
CH4
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Transmitter Noise
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Receiver Des from strong nearby transmitter within RF passband of the Proposed Receiver
Proposed Receiver RF Pass Band
For Receiver IM
Strong RF Signals nearby Victim receiver being saturated IM product falls in to a transmitter’s pass band transmitter’
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Intermodulation
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Intermodulation (IM) Analysis
Where does it come from?
For Transmitter IM
2 or more transmitters stand nearby and intermodulated Final output amplifier turns non-linearity nonNew frequencies radiate out
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Co-Channel Interference
Interference falls on frequency within the receiver’s pass band Can only be eliminated at its source
CH1
CH2
CH3
CH4
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Frequency Reuse
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How to eliminate transmitter noise
Install a band-pass filter at the transmitter output Increase geographical separation Selecting another frequency
ITU ITU ITU ITU
RR RRRR RR
9
Interference Model
Co-Channel (Co-frequency) Interference Co(CoAdjacent Channel Interference Intermodulation Transmitter Noise Receiver Desensitization ……
EMC Analysis and Engineering
Mr. Wang Jian
Spectrum Engineering Division State Radio Monitoring Center wangjian@ +86-10-6835 5711
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National Spectrum Management
Transmitter B
Transmitter A
Proposed Receiver
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Intermodulation Mathematics
Intermodulation Second Order Third Order
Formula Fa ± Fb 2Fa ± Fb, Fa ± 2Fb |Fa ±Fb ±Fc|
Increase the efficiency of frequency usage
Co-channel Cell Co-
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Frequency Reuse
Minimum distance separation to provide sufficient isolation between co-channel stations In cellular mobile systems, Co-channel reuse ratio Q= D/ R
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EMC
ElectroMagnetic Compatibility Analysis Analyzing the impact of introducing a new Radio Frequency assignment into an existing environment of Radio Frequencies.
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What about CDMA
卫星
Interference effect: Capacity Loss Coverage Loss
基站
移动台
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Adjacent Channel Interference
In-band energy from adjacent Channel
CH1
CH2
CH3
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Intermodulation interference
Receiver Intermodulation
Transmitter B
Proposed Receiver
Transmitter C
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Intermodulation interference
Transmitter Intermodulation
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IM make EMC more Complicated
Newly assigned Freq
EXISTING SYSTEM
EXISTING SYSTEM
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Interference Model Summary
Co-Channel Interference CoAdjacent Channel Interference Intermodulation Transmitter Noise Receiver Desensitization
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Receiver Desensitization
Automatic Gain Control (AGC) :
Undesired Signal Gain