GB/T 20851.5-2007[including 2012XG] Electronic toll collection -- Dedicated short range communication -- Part 5: Test methods of the main parameters in physical layer (English PDF)

3.1 Symbols

Following symbols apply to this Part.

dBc refers to the ratio of power to carrier signal power

dBm refers to the ratio of power to 1mW, 0 dBm = 1mW

e.i.r.pcon refers to spurious equivalent isotropic radiated power

e.i.r.pmax refers to maximum equivalent isotropic radiated power

fc refers to center frequency of signal source transmitted signal

fTx refers to nominal carrier frequency

fTxa refers to actual carrier frequency

GT refers to test antenna gain

GRx refers to receiving antenna gain of device under test

GTx refers to transmitting antenna gain of device under test

m refers to modulation index

Pcon refers to spurious emission power

Pcw refers to single-frequency signal power of device under test

Pcwo refers to signal source and single-frequency signal power of test antenna

Po refers to signal source output power

deltaf refers to carrier frequency error

3.2 Abbreviations

Following abbreviations apply to this Part

DSRC Dedicated Short Range Communication

ETC Electronic Toll Collection

OBU On Board Unit

RBW Resolution Band Width

RSU Roadside Unit

VSWR Voltage Standing-Wave Ratio

4.1 Power meter

- Power measurement range. -60 dBm ~ +20 dBm;

- Frequency range. 10 MHz~18 GHz;

- Power measurement error. ±3%.

4.2 Frequency meter

- Frequency range. 10 Hz~+20 GHz;

- Frequency measurement error. ±10 x 10-9.

4.3 Microwave signal source

- Frequency range. 250 kHz~20 GHz;

- Frequency accuracy. fc x 10 x 10-9;

- Phase noise. Less than -98 dBc/Hz@10 GHz, 1 kHz bias.

4.4 Spectrum analyzer

- Frequency range. 3 Hz~26.5 GHz;

- Dynamic range. Not less than 70 dB;

- Resolution bandwidth. 10 Hz~3 MHz;

- Background noise. Not greater than -140 dBm/Hz.

4.5 Vector signal analyzer

- Frequency range. DC~6 GHz;

- Vector modulation analysis type. Amplitude modulation, frequency modulation and

phase modulation analysis.

4.6 Digital oscilloscope

- Bandwidth. 1 GHz;

- Sampling rate. 2 Gsa/s;

- Memory depth. 2 M points for each channel;

6.4.1 Conduction test

6.4.1.1 Test equipment

Power meter.

6.4.1.2 Test steps

Test steps are as follows.

a) Set the operating frequency of transmitter of device under test; set device under test

in a non-modulation state, i.e. carrier state;

b) Set transmitting frequency of device under test to the maximum value;

c) Use power meter to measure power Pcw of transmitting antenna port of device under

test; calculate corresponding equivalent isotropic radiated power, in dBm;

computational formula.

e.i.r.pmax = Pcw X GTx

Repeat the above steps to measure equivalent isotropic radiated power at other carrier

frequencies.

6.4.2 Radiation test

6.4.2.1 Test equipment

Power meter, microwave signal source.

6.4.2.2 Test steps

Test steps are as follows.

a) Set the operating frequency of transmitter of device under test; test the device under

test in a non-modulation state, i.e. carrier state;

a) Set the transmitting power of device under test to the maximum value;

b) Use power meter to measure the power Pcw;

c) Under the same test conditions, use microwave signal and test antenna of known

gain GT to replace the device under test, and use power meter to measure power

Pcwo; adjust the output power of microwave signal source, until Pcwo is equal to Pcw;

d) Adjust corresponding equivalent isotropic radiated power, in dBm; computational

formula.

e.i.r.pmax = Po X GT

frequency bands, until the power measured by spectrum analyzer is equal to Pcon;

f) Calculate spurious emission e.i.r.pcon at corresponding frequency bands, in dBm;

computational formula.

e.i.r.pcon = Po X GT

Repeat above steps to measure spurious emissions of frequency bands at other carrier

frequencies.

6.6 Modulation mode and modulation index

6.6.1 Test equipment

Vector signal analyzer.

6.6.2 Test steps

This test may be completed at radiation or conduction test conditions. Test steps are as

follows.

a) Set the operating frequency of transmitter of device under test; set the device under

test in a state of continuous emission of test signal;

b) Set transmitting power of device under test to the maximum value;

c) Set modulation index of device under test to the minimum value within its allowable

range;

d) Use vector signal analyzer to measure the modulation index of device under test;

e) Change the operation frequency of transmitter of device under test; measure the

modulation index at other carrier frequencies;

f) Set modulation index of device under test to the maximum value within its allowable

range;

g) Use vector signal analyzer to measure the modulation index of device under test;

h) Change the operating frequency of transmitter of device under test; the remaining

settings are unchanged; test the modulation index under other carrier frequencies.

6.7 Bit rate

6.7.1 Test equipment

Digital oscilloscope.

6.7.2 Test steps

Attachment.

GB/T 20851.5-2007 "Electronic toll collection - Dedicated short range

communication- Part 5.Test methods of the main parameters in physical

layer" National Standard No. 1 Amendment

The contents in Chapter 1 "This Part is applicable to the test of main parameters of

the physical layer of electronic toll collection dedicated short range communication

road side unit (RSU) and on-board unit (OBU)" is change to be "This Part is applicable

to highways and city roads electronic toll collection system. Fields such as automatic

vehicle identification, vehicle access management may reference to this Part for the

use".

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