Compal Electronics Inc PICONODE Manual De Usuario
PicoNode Integration Specification
37
Embedded ground-backed CPWG
Stripline
Asymmetrical stripline
9.4.2 Controlled Impedance Trace Design
9.4.2.1 Dimensions
The controlled impedance trace should have dimensions that correspond to 50 ohm ± 10% no
matter what the specific transmission line type is. The specific design depends on trace width,
thickness, dielectric constant, and distance to grounds. These dimensional factors are
controlled by the PCB fabrication shop. From a design perspective, on the PCB fabrication
drawing, clearly mark that the microstrip trace requires controlled impedance of 50 ohm ± 10%.
Also specify that the PCB shop must test to confirm that the impedance is within 10% of
50 ohms.
matter what the specific transmission line type is. The specific design depends on trace width,
thickness, dielectric constant, and distance to grounds. These dimensional factors are
controlled by the PCB fabrication shop. From a design perspective, on the PCB fabrication
drawing, clearly mark that the microstrip trace requires controlled impedance of 50 ohm ± 10%.
Also specify that the PCB shop must test to confirm that the impedance is within 10% of
50 ohms.
9.4.2.2 Ground Planes
All transmission line types except surface CPWG and embedded CPWG requires ground planes
either above the RF trace, below the RF trace, or both above and below the RF trace. In these
cases with ground planes, the RF trace must not cross any splits in the ground plane. The
ground plane directly above and below the RF trace must be continuous.
either above the RF trace, below the RF trace, or both above and below the RF trace. In these
cases with ground planes, the RF trace must not cross any splits in the ground plane. The
ground plane directly above and below the RF trace must be continuous.
9.4.2.3 Matching Network
A matching network may be used at the module’s RF pin to ensure good 50 ohm transition
between the host board and the module. Another matching network may be used on the
antenna side of the controlled impedance trace to match the antenna to 50 ohms.
between the host board and the module. Another matching network may be used on the
antenna side of the controlled impedance trace to match the antenna to 50 ohms.
9.4.2.4 Stitching Vias
Ample ground stitching vias should be used around the connectors, trace, and module. It is
recommended that a via stitching pattern be used with no more than 0.25” separation between
adjacent vias.
recommended that a via stitching pattern be used with no more than 0.25” separation between
adjacent vias.
9.4.2.5 Isolation
Since the RF signal coming from the module has already been filtered, there is no isolation
requirement.
requirement.
9.4.2.6 Example RF Trace Design
The following figure shows surface-ground backed CPWG design with 22 mil trace width, 15 mil
gap-to-surface ground plane, 2 mil thick top layer (1/2 oz copper + plating), 14 mil dielectric
thickness to solid ground plane underneath, and a FR-4 dielectric constant of 4.4. This
configuration achieves the desired 50 ohm ± 10% for the controlled impedance. Note that in
gap-to-surface ground plane, 2 mil thick top layer (1/2 oz copper + plating), 14 mil dielectric
thickness to solid ground plane underneath, and a FR-4 dielectric constant of 4.4. This
configuration achieves the desired 50 ohm ± 10% for the controlled impedance. Note that in