ME910G1 HW Design Guide
1VV0301593 Rev.3 Page 64 of 97 2020-03-24
6.4.2.1. Transmission line design
During the design of the ME910G1 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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