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FSS JODY-W263 Integration Instructions Rev 02.docx
www.foresightsports.com
Figure 1: Transmission line trace design
To properly design a 50 Ω transmission line, the f
ollowing remarks should be
considered:
•
The designer should provide enough clearance from surrounding traces and
ground in the same layer; in general, a trace to ground clearance of at least two
times the trace width should be considered, and the transmission line should be
“guarded” by ground plane area on each side.
•
The characteristic impedance can be calculated as first iteration using tools
provided by the layout software. It is advisable to ask the PCB manufacturer to
provide the final values that are usually calculated using dedicated software and
available stack-ups from production. It could also be possible to request an
impedance coupon on panel’s side to measure the real impedance of the
traces.
•
FR-4 dielectric material, although its high losses at high frequencies can be
considered in RF designs providing that:
o
RF trace length must be minimized to reduce dielectric losses.
o
If traces longer than a few centimeters are needed, it is recommended to use
a coaxial connector and cable to reduce losses.
o
Stack-up should allow for wide 50
Ω
traces and at least 200 µm trace width is
recommended to assure good impedance control over the PCB
manufacturing process.
o
FR-4 material exhibits poor thickness stability and thus less control of
impedance over the trace length. Contact the PCB manufacturer for specific
tolerance of controlled impedance traces.
