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CT-EM250
ZigBee-Ready RF Transceiver Modules
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Page 11 of 15
Antenna Design Considerations
CT-EM250 provides an integrated antenna. The design should be effective for many
applications requiring a compact solution containing all the critical RF parts within the
module. Applications requiring better range may consider an external antenna or
possibly even an external booster circuit (power amplifier).
The range testing using the integrated antenna shows a typical distance of 100 m
outdoor line-of-sight (LOS). If the application is used indoor, the range will be around
10 to 30 m, depending on structure and building materials.
The module with antenna is matched for use in the 2.4 GHz band. Due to the
dielectric ceramic material the antenna is shorter than a normal quarter wave antenna.
However, it can still provide high radiation efficiency (typical 1 dBi). The radiating part
of the antenna is located on one side of the PCB. The radiation pattern from the
antenna is shown in figure 2. The maximum radiation is in the plane normal to the
length axis of the antenna. For best possible omni-directional radiation the module
should be oriented so that the antenna is vertical. In order to achieve best range the
transmitting and receiving antenna should be oriented the same way with same
polarity. Indoors reflections of the radio waves will affect the range.
Figure 2 : Integrated chip antenna radiation pattern at different orientations