LE915Ax-P
Hardware Design Guide
1VV0301680 Rev. 2
Page 31 of 51
2021-10-04
Not Subject to NDA
6.1.2.1.
Transmission Line Design
When designing an interface board, the placement of components was chosen properly,
in order to keep the length of the line as short as possible, thus leading to the least
possible power loss. A Grounded Coplanar Waveguide (G-CPW) line has been chosen, this
kind of transmission line ensures good impedance control and can be implemented in an
external PCB layer as needed in this case. A SMA female connector has been used to feed
the line.
The interface board is made on a FR4, 4-layers PCB. The 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 a track width = 1.1 mm,
clearance from a coplanar ground plane = 0.3 mm each side. The line uses the reference
ground plane on layer 3, while copper is removed from layer 2 below the line. The height
of the trace above ground plane is 1.335 mm. The calculated characteristic impedance is
51.6
Ω
, the estimated line loss is less than 0.1 dB.
The line geometry is shown below:
Figure 10:
Line Geometry
6.1.2.2.
Transmission Line Measurements
An HP8753E VNA (Full-2-port calibration) was used in this measurement session.
A calibrated coaxial cable was soldered to the pad corresponding to RF output; a SMA
connector was 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.
Содержание LE915A P Series
Страница 1: ...LE915Ax P HW Design Guide 1VV0301680 Rev 2 2021 10 04 Telit Technical Documentation...
Страница 51: ......
