ON Semiconductor AND9670/D Quick Start Manual page 10

Left Hand Circular Polarized Antenna
The following tag reading measurement is performed with the antenna[5] provided with the SensorRFA−GEVB[2].
The reading distance about 135 cm can be achieved, in front of the antenna with the tag in the horizontal plane as shown in
the picture below. The blue reading area as referenec shows the max distance with the whip antenna about 60 cm.
Figure 12. Reading Distance with Circular Antenna vs. Whip Antenna
Optimum reader range area and maximum reading distance can be selected depending on the application with the reader
antenna type and tag position/orientation respectively. If the tag position is mostly in front of the antenna and higher reading
distance is required, the circular polarized antenna[5] can be used but at the expense of higher price and size. But even with
a small sized and cheap whip antenna [3], a decent reading performance can be achieved if the position and orientation for both
antenna and tag are selected carefully.
AUTOPOWER AND TX ATTENUATOR
After successuful reading of the SPS tag, the console window output following data e.g. for temperature sensor:
Found Tag (type = TEMP, label = 55c97, temp = 23.8, rssi = 13, tx_att = 6)
whereby
•
Label = Last 5 hex digits of tag Tag Identification Data (TID)
•
Temp = Temperature of the tag
•
RSSI = Received Signal Strenght Indicator (RSSI) value from 0−31 whereby 0 ist the weakest and 31 is the strongest
signal
•
TX Attenuator used for the reading the tag and can be set from 0 to 19 wherby the value 0 dB is set with highest RF
power and 19 dB results in the lowest RF power
The loaded sample program is using the pre−compiled library instanced with AS3993_RFID rfid in the main.c file.
In order to be able to change the TX attenuator or switch on/off the Autopower parameter within the AS3993_RFID library,
following steps are recommended to import the library into the workspace:
AND9670/D
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