Section 5.6 · Home exercises · 2 of 7
Home exercise 5.6.2: A circuit board at 5 GHz
About the home exercises of Section 5.6
Home exercises 5.6.1–5.6.3 belong to the lecture, Home exercises 5.6.4–5.6.7 to the exercise lecture.
A circuit board at 5 GHz
#A Wi-Fi signal at runs inside an FR-4 laminate with and loss tangent , . Find
- the complex permittivity and the effective conductivity ,
- the wave number , the wavelength in the board and the phase velocity,
- the attenuation in () and the loss along a track.
Strategy
A data-sheet loss tangent defines directly, and by Eq. (5.6.14). Then .
a)
b)
and , so
c)
, so a track loses .
Answer
Check
For the low-loss forms of Eq. (5.6.22) give and , both within of the exact values.
Remark
At constant the loss in dB grows in proportion to , since and : at the same track would lose . On top of this come the losses in the copper, which are of the same order. Low-loss laminates with are used above a few GHz.