AMB8426-M_8626-M_MA_EN_V2_4
Page 40 of 48
Released: Nov.2013
An optional PI-filter (Capacitor C1 to mass, Inductor L1 in series, and capacitor C2 to
mass) should be provided to allow for the possibility to tune or filter the antenna. When
no filtering/ matching is necessary the filter can be bridged with a 68 pF capacitor.
Figure 18
Matching circuit of a λ/4 antenna
A simple but effective antenna solution is an 8,6 cm long piece of wire, a Lambda/4 antenna.
This wire should point away from the module and needs a ground plane below the feeding
point. The antenna should have a minimum distance of 3,5 cm to any other metal or conductive
material.
Any metallic, metalized or conductive material utilized for the system’s housing is attenuating or
even impenetrable for radio waves. In this event, the antenna has to be placed outside the
enclosure. The RF is led through a 50 Ohm track towards a RF connector (e.g. BNC, SMA,
GSC or U.FL). This connector could protrude through the enclosure (for example SMA-/BNC
right angle connectors, Figure 19) or could be led to the outside by a pre-assembled cable (for
example GSC to SMA, Figure 20).
Figure 19
Housing break through with right angled BNC-connector
