Test Specification for Eurobalise FFFIS

Page 34 of 332
SUBSET-085, Issue 2.2.2
November 9, 2007
4.2.2.9.2 Calibration Abstract
This calibration procedure will give a reference value P 42RL for each measurement point, defined in clause C3 of
Annex C on page 202, which shall be used to define the Reference Field in the Cross-talk protected zone. The
reference value P 42RL is reflecting the flux received by the Reduced Size Reference Loop, item 19, measured by
Power Meter 2 (P M2 ), and subsequently compensated and called P 42RL . The compensation is done to give corresponding
values between measurements with a Test Antenna and a Reference Loop used as measuring devices.
The calibration is performed with the current I u2 /B through the transmitting Reference Loop (item 7). The current
through the receiving Reference Loop (item 19) is monitored by Power Meter 3 (P lc ).
The orientation of the receiving Reference Loop is with its longest size parallel to the X axis. Locate the Activation
Antenna in position [X = 440, Y = 220, Z = 0] relative to the Reference Loop, item 7.
4.2.2.9.3 Calibration Procedure
1. Position the Reference Loop, item 19 (below called RL_probe), in the position [X = 1000, Y = 0,
Z = 220] relative to the Reference Loop. This position has previously been measured in the Side Lobe
Zone and is only measured to refer the values measured with the RL_probe to the values previously
measured with the Test Antenna. Be sure to position the electrical centre of the RL_probe aligned with
respect to the electrical centre of the Reference Loop. Also check that the X, Y, and Z axes of the Reference
Loop are correctly aligned to the X, Y, and Z axes of the positioning system.
2. Set the Signal Generator to generate an FSK signal that carries telegram type 1.
3. Adjust the Signal Generator amplitude in order to achieve a current of approximately I u2 /B through the
transmitting Reference Loop.
For calibration and compensation of the Current Sense Balun see clause H5 of Annex H on page 317.
Record the reading of Power Meter 2 and call it P SB . Calculate the difference between P SB and the value
P 42RL for position [X = 1000, Y = 0, Z = 220] measured in sub-clause 4.2.2.5 on page 31. Call it P OFFSET .
P OFFSET = P SB - P 42RL (measured in sub-clause 4.2.2.5)
Repeat
for each
position
4. Record the reading of Power Meter 2 (called P M2 ).
5. Compensate the P M2 reading with the offset value calculated in step 3. 8 Call the new value
P 42RL .
P 42RL = P M2 - P OFFSET , all values in dBm.
6. Perform 4 and 5 for all the [X, Y, Z] positions listed in clause C3 of Annex C on page 202.
7. Position the RL_probe, in position [X = 0, Y = 0, Z = 220] relative to the Reference Loop. Record the
reading of Power Meter 2 and call it P RLPREF . This value is used in the Balise measurement below.
8
The reason for this compensation is that the value of P 42RL shall be compared with the corresponding values measured
with the Test Antenna.