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4.2 Antenna Design
RF650
The design and positioning of the aerial 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 RF ground pin should be connected to a ground plane which should shield the aerial connection and the
PCB layout around the aerial track itself should be such as to give a 50 Ohm impedance. The aerial should be
kept as far away from sources of electrical interference as physically possible. The specified power supply
decoupling capacitors should be placed close to the module as possible and have direct connections to the
relevant pins.
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. Earth planes restricting the radiation path of the antenna will also
have the same effect.
The best range will be achieved with either a straight piece of wire, rod or PCB track @ ¼ wavelength (15.5cm
@ 433.9MHz). Increased range may be achieved if this ¼ wave antenna is placed perpendicular to and in the
middle of a solid earth plane measuring at least 16cm radius. In this case, the antenna should be connected
to the module using 50 Ohm coaxial cable and the PCB track layout tips given above should be observed.
Helical Antenna
RF
RF
15.5cm @ 433MHz
34mm @ 433MHz
17 turns equally spaced
∅
= 5mm (inside)
Whip Antenna
DS650-6 June ‘06
©2006 RF Solutions Ltd, www.rfsolutions.co.uk
Tel 01273 898000 Fax 01273 480661
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