QM Radio Transmitter Module
Application Information
Antenna Design
The design and positioning of the antenna is as
crucial as the module performance itself in
achieving a good wireless system range. The
following will assist the designer in maximising
system performance.
The antenna should be kept as far away from
sources of electrical interference as physically
possible. If necessary, additional power line
decoupling capacitors should be placed close to
the module.
The antenna ‘hot end’ should be kept clear of any
objects, especially any metal as this can severely
restrict the efficiency of the antenna to receive
power. Any earth planes restricting the radiation
path to the antenna will also have the same effect.
Best range is achieved with either a straight piece
of wire, rod or PCB track @ ¼ wavelength
(15.5cm @ 433.92MHz). Further range may be
achieved if the ¼ wave antenna is placed
perpendicular in the middle of a solid earth plane
measuring at least 16cm radius. In this case, the
antenna should be connected to the module via
some 50 ohm characteristic impedance coax
QFMT1-XXX
Application Circuit
For detail application information please see
datasheet DS600
Helical Antenna
RF
34mm @ 433MHz
17 turns equally spaced
∅
= 5mm (inside)
Whip Antenna
RF
15.5cm @ 433MHz
Figure 2: Antenna Configurations To Be Used
With The QM Transmitter Module
DS301-2
Oct 02
©2000
REG No 277 4001, England.
Page 4
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