ME910C1 HW User Guide
1VV0301351 Rev.8 Page 72 of 99 2018-09-28
6.4.2. PCB Guidelines in case of FCC Certification
In the case FCC certification is required for an application using ME910C1, according to
FCC KDB 996369 for modular approval requirements, the transmission line has to be
similar to that implemented on ME910C1 interface board and described in the following
chapter.
6.4.2.1. Transmission line design
During the design of the ME910C1 interface board, the placement of components has
been chosen properly, in order to keep the line length as short as possible, thus leading to
lowest power losses possible. A Grounded Coplanar Waveguide (G-CPW) line has been
chosen, since this kind of transmission line ensures good impedance control and can be
implemented in an outer PCB layer as needed in this case. A SMA female connector has
been used to feed the line.
The interface board is realized on a FR4, 4-layers PCB. Substrate material is
characterized by relative permittivity εr = 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:
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