GE866-QUAD Hardware User Guide
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Page 39 of 82
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
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:
