User Guide

LE866 Hardware Design Guide
1VV0301355 Rev. 5 Page 60 of 91 2019-04-05
The interface board is realized on a FR4, 4-layers PCB. Substrate material is
characterized by relative permittivity ε
r
= 4.6 ± 0.4 @ 1 GHz, TanD= 0.019 ÷ 0.026 @ 1
GHz.
A characteristic impedance of nearly 50 Ω is achieved using trace width = 1.1 mm,
clearance from coplanar ground plane = 0.3 mm each side. The line uses reference
ground plane on layer 3, while copper is removed from layer 2 underneath the line. Height
of trace above ground plane is 1.335 mm. Calculated characteristic impedance is 51.6 Ω,
estimated line loss is less than 0.1 dB. The line geometry is shown below:
6.1.3.2. Transmission Line Measurements
An HP8753E VNA (Full-2-port calibration) has been used in this measurement session.
A calibrated coaxial cable has been soldered at the pad corresponding to RF output; a
SMA connector has been soldered to the board in order to characterize the losses of the
transmission line including the connector itself. During Return Loss / impedance
measurements, the transmission line has been terminated to 50 Ω load.