User's Manual

GE866-DUAL Hardware User Guide
1VV0301051 Rev. 2 – 2014-04-07 7
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Mod. 0805 2011-07 Rev.2
7.2. PCB Design Guidelines
This section explains the suggested design for the
transmission line on the customer’s application board.
7.2.1. Transmission line design
During the design of the GE866-QUAD 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: