Texas Instruments TIRIS SCBU025, Справочное руководство

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2.6 How to Measure Antenna Voltages
2.7 How to Use the Charge-Up Diagrams
How to Measure Antenna Voltages
Each diagram has several lines or 'envelopes' on it, each representing a different voltage applied to the
antenna. The smallest 'envelope' (that closest to the antenna) shows the magnetic field induced by the
lowest voltage applied to the antenna, and the largest 'envelope' shows the field induced by the highest
antenna voltage (see
Table 2-1 ).
The antenna voltage applied is set according to the regulations of the country in which the system is to be
used.
Table 2-1 is a table of antenna voltages allowed for each country with a charge-up time of 50 ms
and a receive time of 40 ms. By comparing these voltages with the relevant line on the antenna isofield
diagram, you can see what the charge-up distance will be for the country that the system will be used in.
Table 2-1. Maximum Antenna Voltages (Peak-to-Peak)
(1)
Antenna
Country Comments
G01C G02C G03C S01C
Netherlands 39 98 21 361 CISPR
Germany 43 107 23 393 CISPR
Denmark 43 107 23 393 CISPR
United Kingdom 94 236 51 650
(2) (3)
PEAK
Japan 371 713
(2) (3)
203 650
(2) (3)
PEAK (provisional value only)
United States 499
(2)
713
(2) (3)
272 650
(2) (3)
RMS (100 ms window)
France 688
(2)
713
(2) (3)
375
(2)
650
(2) (3)
RMS
Australia 707
(2)
713
(2) (3)
386
(2)
650
(2) (3)
PEAK (provisional value only)
(1)
The figures given in this table have been agreed with the relevant government agencies and are for "portable equipment". For
some countries, (for example, the Netherlands), if the equipment is made a permanent fixture, it is possible to obtain permission
for higher antenna voltages to be used.
(2)
These voltages cannot be achieved using the RF Module RI-RFM-001. It should be possible to achieve these levels if you use
the RF Module RI-RFM-002 which allows approximately twice the antenna voltage of the 001.
(3)
Temperature limit of antenna.
The antenna voltages can only be measured using an oscilloscope with a 10 M
Ω
probe across the
antenna terminals (metal-to-metal contact). Check the peak-to-peak level and then reverse the probe
contacts and check again; the highest reading is the correct reading.
To work out the charge-up range for a particular antenna, you must first look in Table 2-1 to see what
antenna voltage is allowed in the country that the system will be used in. Now go to the charge-up
diagram for the antenna, and see where on the diagram (usually between two lines) that value falls. This
will show you the readout range (in a environment with an acceptable noise level).
The innermost line (or envelope) shows the reading range possible with the lowest allowed voltage, and
the outer line is the range possible with the maximum voltage. On
Figure 2-5 A, we have marked the
voltage value for each line to show how this works.
Examples 1 and 2 provide two examples of how to work out the charge-up distance for a particular
antenna in two different countries.
Example 1: Using Antenna G02C in Japan
1. Look in Table 2-1 , and you will see that the allowed voltage for antenna G02C in Japan is 713 V.
2. Now go to Figure 2-6 A. 713 V falls just inside the outer line, which represents 730 V.
3. Using a ruler, line up the 713 V "spot" with the side axis. This shows you that you have a charge-up
distance of just over 70 cm (just over 27.5 inches).
SCBU025 – November 1996 How the System Works 11
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