terminologies and units

8/22/2019 Terminologies and Units

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Terminologies and Units

Ms. Zeng FanshengEngineer of Spectrum Engineering Division

State Radio Monitoring Center

[email protected]

+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



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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


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.

terminologies and units

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