Design Guide

RF Characteristics
A DIVISION OF TRIMBLE
38 Hardware Overview
increasing the moduleʼs sensitivity. Lower “M” values send data at higher rates,
decreasing the sensitivity somewhat.
The region of operation is also a factor. The Nano has slightly better receive sensitivity in
the regions that fall within the range of 865 to 868 MHz than in regions that fall within the
range of 917 to 928 MHz.
The following table gives the sensitivity for region and “M” value at a transmit output level
of +27 dBm.
Note that sensitivity is strongly affected by the success rate required by the application.
The sensitivity values in the table reflect a very high read success rate (greater than
90%). Tags typically will begin to respond sporadically at receive levels that are 5 dB
lower than the values shown in this table.
Receiver Adjacent Channel Rejection
The ThingMagic Nano receives signals that are centered at +250 kHz from its own
carrier. The width of the receive filter is adjusted to match the “M” value of the signal
being sent by the tag. An M value of 2 require the widest filter and an M value of 8
requires the narrowest filter. If operating in an environment where many readers are
present, observe the performance of one reader as the other readers are turned on and
off. If the performance improves when the other readers are turned off, then the system
may be experiencing reader-to-reader interference. This reader-to-reader interference will
be minimized by using the highest “M” value that is consistent with the tag read rates
required by the application.
Region “M” Value Sensitivity
North America and
subsets of 917 to 928
MHz band
8-57 dBm
4-55 dBm
2-45 dBm
EU and India (865 to 868
MHz
8-60 dBm
4-58 dBm
2-49 dBm