Download - Terminologies and Units
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Terminologies and Units
Ms. Zeng FanshengEngineer of Spectrum Engineering Division
State Radio Monitoring Center
+8610-68355711
Radio Monitoring and Spectrum Management Training
(China,23-31,May,2005)
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Content
1. Units;
2. Antenna gain;
3. ERP & EIRP;4. PFD;
5. Station Coordinates;
6. Database.
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dB
Expressing the ratio of two values
dB = 10 log (P2/P1)
P2 --- Variable power ,(watt, milliwatt or microwatt),
P1 --- Reference power, (watt, milliwatt or microwatt).
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Why we choose dB?
e.g. Pr=10watts, Pt=10000watts,
Pt/Pr=1000
10 log (Pt/Pr)=10log(Pt/)-10log(Pr)=30dB
in linear scale
in logarithmic scale
Pt/Pr
1000
30
x
y
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dBw / dBmw / dBw
Expressing the ratio of two power
dBx = 10 log (P2/P1)
P2 --- Variable power ,(watt, milliwatt or microwatt),P1 --- Reference power,commonly equal to 1, (watt, milliwatt
or microwatt).
X --- Variable
e.g.
P1=1watt,P2=5watts, 10log(5watts/1watt)=7dBw
P1=1mW,P2=5mW, 10log(5mW/1mW)=7dBmw=7dBm
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dBv / dBc
Expressing voltage or current ratios
dB Voltage = 20 log (V2/V1),or dB Current = 20 log (I2/I1)
V2(I2) --- Variable voltage, (volt, ampere),
V1(I1) --- Reference voltage, commonly equal to 1, (volt,
ampere).
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dB units and their reference levels
Unit Reference
dBw 1 watt
dBm 1 milliwattdBkW 1 kilowatt
dBV 1 volt
dBmV 1 millivolt
dBV 1 microvoltdBV/m 1 microvolt/meter
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Conversion
dBkW = dBW - 30
dBm = dBW + 30
dBmV = dBV + 60
dBV = dBV + 120
dBm = dBV - 107 (impedance = 50 ohms)
dBV/m = dBV + ke/dB(m
1) (ke is antenna factor )
dBm = dBW + 30
dBmV = dBV + 60
dBm = dBV - 107 (impedance = 50 ohms)
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dBm/dBW dBmV/dBV
dBm = dBW + 30
dBmV = dBV + 60
dBmmwmwmwwatts 40)1/1010log(10)1/10log(10 3
dBwwwatts 10)1/10log(10
dBmVmVmVdBVoltVolt 80)1/1010log(20V20)1/10log(20 3
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dBm/dBV
dBm = dBV - 107 (impedance = 50 ohms)
P --- MilliWatt, U---MicroVoltage, R---Ohms
)log(10)log(20)log(10
2
RUP
R
UP
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Exercise
1. Power=25watts = ? dBw = ? dBm
2. Voltage = 0.5 V, Impedance =50ohms, Power=?dBm
Power=20log(0.5)-137=(-6)-107=-113 dBm
Power=10log(25watts/1watt)= 13.98 dBw
=13.98 dBw + 30dB = 43.98 dBm
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Antenna gain
Omni-directional
Gi, dBi
Directional
Gd,dBd
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Antenna Directional Characteristics
isotropic dipole
Gi (dBi) Gd (dBd)
dBd =dBi - 2.15 dB (logarithmic scale)
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omni-directional directional
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Effective Radiated Power (ERP)
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ERP
ERP = P L + Gd;
P --- Transmitter Power, dBw;
L --- Loss, dB;
Gd--- Antenna Gain, dBd
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ERP (Cont.)
ERP=y-0.25-x-0.25+z
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Equivalent Isotropically RadiatedPower (EIRP)
EIRP = P L + Gi
P --- Transmitter Power, dBw;
L --- including Connector Loss, Cable Loss,
Ancillary Equipment Loss, etc.dB;
Gi--- Antenna Gain, dBi.
ERP = 0.61 EIRP (linear scale)ERP =EIRP - 2.15 dB (logarithmic scale)
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Power flux-density (PFD)
2/dBW m
2
2
2i
4
4pfd
4
(pfd)
dAgPP
d
gPd
P
eeer
ee
e
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Designation of Emissions
For example: 27M0G7WDT
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Longitude & Latitude
GPS
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Height
Altitude
Above sea level/Above ground
Effective Height
Height finder
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Database
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Technical Data
Transmitter output power;
Antenna type and associated gain;
Cable/transmission line loss;
Effective radiated power(ERP);
Station coordinates.
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Database
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Collection and input
Accuracy
Maintenance
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summary
dB/dBW/dBV;
Antenna gain;
Effective Radiated Power (ERP);
Equivalent Isotropically Radiated Power(EIRP);
Field-Strength and Power Flux-Density;
Designation of Emissions;
LongitudeLatitude & Height;
Database.