Integration Guide
Draft
EDG0208IG001
Page 11
Rev. 1.03 –4/19/07
Figure 3 - Example of a GOOD RF Thermal Relief
Antenna and RF Signal Trace
The PCB trace that feeds the RF output port must be designed for a 50 ohm characteristic
impedance, coplanar, or routed into internal layers to keep the top layer continuous around
and underneath the Enabler module. Ample ground vias should be provided around the RF
contacts, the RF trace and launch pad. If possible, keep I/O and power traces away from the
RF port. This includes traces running parallel or orthogonal to it. Thermal relief should not be
used on the antenna output port ground pads. The designer must pay close attention to the
size of the pad and thickness of the dielectric beneath the signal pad and trace. Most PCB
manufacturers can adjust the trace width to maintain 50 ohms impedance if the traces are
identified and instructions are included on the FAB drawing. This service is typically provided
at no or minimal additional cost.
For minimum RF emissions due to the fundamental frequency of operation, the Enabler
module works best with an antenna load that has a VSWR of 1.5:1 or better. The antenna
should not have gain at the harmonic frequencies, otherwise, the conducted harmonics could
get amplified to a point where the product no longer passes type approval. However, for
applications where antenna quality is less than ideal, it is recommended to have a low pass
filter (Pi structure with N=3) in the RF path to the antenna. This is a secondary plan should
there be a need to lower harmonic levels at frequencies above the PCS band. The pad
structure may also be used to match the antenna load impedance, if required. If it is not
needed, a capacitor of low reactance may be used to bridge the Pi structure.
The RF cable going between the Enable module and the antenna is very lossy, therefore, the
length of this cable should be kept as short a possible.
If multiple antennas are used in their design, care should be taken during placement selection
to minimize the coupling between the GSM antenna and the other antennas.
GOOD RF thermal relief
Summary of Contents for Enabler EDG0208
Page 26: ...Integration Guide Draft EDG0208IG001 Page 21 Rev 1 03 4 19 07 Figure 11 Back of EDG0208 01 ...
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