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[ZigBit 900 MHz Wireless Modules]
17
3.7
Antenna reference designs
Multiple factors affect proper antenna match, hence, affecting the antenna pattern. The particular factors are the board
material and thickness, shields, the material used for enclosure, the board neighborhood, and other components
adjacent to antenna. Following guidelines need to be followed when designing the base board for the ZigBit.
General Recommendations:
Metal enclosure should not be used. Using low profile enclosure might also affect antenna tuning.
Placing high profile components next to antenna should be avoided.
Having holes/vias punched around the periphery of the board eliminates parasitic radiation from the board
edges also distorting antenna pattern.
ZigBit module should not be pla
ced next to consumer electronics which might interfere with ZigBit’s RF band
frequency.
The board design should prevent propagation of microwave field inside the board material. Electromagnetic waves of
high frequency may penetrate the board thus making the edges of the board radiate, which may distort the antenna
pattern. To eliminate this effect, metalized and grounded holes/vias must be placed around the board's edges.
4.
Section 4
Figure 4-1. Internal schematics.
RFonly_212B_Schem
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Handling Instructions
The ZigBit Modules are fixed with an EMI Shield to ensure compliance to Emission and Immunity rules. This shield is
galvanic and NOT air tight. So cleaning of the module with IPA / other similar agents is not advised. Humidity protection
coating (conformal) will cause deviated RF behavior and coating material being trapped inside EMI Shield. So this
should be avoided. For products requiring conformal coating, it is advised to suitably mask the ZigBit before applying
the coating to rest of the ZigBit carrier board. To protect ZigBit from humidity, the housing of the product should ensure
suitable Ingress Protection standards are complied with.
The MS-147 connector should never be exposed to Varnish / similar conformal coating material which will affect
electrical connection on the surfaces of connector.
The in-built chip antenna has been tuned for the particular design
4.1.1
General recommendations
Metal enclosure should not be used. Using low profile enclosure might also affect antenna tuning
Placing high profile components next to antenna should be avoided
Having holes/vias punched around the periphery of the board eliminates parasitic radiation from the board edges
also distorting antenna pattern
ZigBit module should not be placed next to consumer electronics which might interfere with ZigBit's RF frequency
band
