E2v TSEV8388B User Manual - page 7
Overview
TSEV8388B - Evaluation Board User Guide
1-3
0973D–BDC–02/09
1.3
Board
Mechanical
Characteristics
The board layer’s number, thickness, and functions are given below, from top to bottom.
The TSEV8388B is a seven-layer PCB constituted by four copper layers and three
dielectric layers.
The four metal layers correspond respectively from top to bottom to the AC and DC sig-
nals layer (layer 1), two ground layers (layers 3 and 5), and one supply layer (layer 7).
The upper inner ground plane (layer 3) constitutes the reference plane for the 50
Ω
impedance signal traces. The lower inner ground plane (layer 5) is used for dielectric
substrate rigidity and is a replica of the upper ground plane.
The backside metal layer is dedicated to the power supplies planes, surrounded by a
ground plane.
The three dielectric layers are respectively (from top to bottom) constituted by a low
insertion loss dielectric layer (RO4003) (layer 2) and two parallel BT/Epoxy dielectric
layers (layers 4 and 6).
Considering the severe mechanical constraints due to the wide temperature range and
the high frequency domain in which the board is to operate, it is necessary to use a
sandwich of two different dielectric materials, with specific characteristics:
A low insertion loss RO4003 Hydrocarbon/wovenglass dielectric layer of 200 µm
thickness, chosen for its low loss (–0.318 dB/inch) and enhanced dielectric
consistency in the high frequency domain. The RO4003 dielectric layer is dedicated to
the routing of the 50
Ω impedance signal traces (the RO4003 typical dielectric
constant is 3.4 at 10 GHz). The RO4003 dielectric layer characteristics are very close
to PTFE in terms of insertion loss characteristics.
A BT/Epoxy dielectric layer of 2 mm total thickness which is sandwiched between the
upper ground plane and the back-side supply layer.
Table 1-1. Board Layers Thickness Profile
Layer
Characteristics
Layer 1
Copper layer
Copper thickness = 35 µm
AC signals traces = 50
Ω microstrip lines
DC signals traces (GORB, GAIN, DIODE)
Layer 2
RO4003 dielectric layer
(Hydrocarbon/Wovenglass)
Layer thickness = 200 µm
Dielectric constant = 3.4 at 10 GHz
–
0.044 dB/inch insertion loss at 2.5 GHz
–
0.318 dB/inch insertion loss at 18 GHz
Layer 3
Copper layer
Copper thickness = 35 µm
Upper ground plane = reference plane 50
Ω microstrip return
Layer 4
BT/Epoxy dielectric layer
Layer thickness = 630 µm
Layer 5
Copper layer
Copper thickness = 35 µm
Lower ground plane (board mechanical rigidity)
Layer 6
BT/Epoxy dielectric layer
Layer thickness = 630 µm
Layer 7
Copper layer
Copper thickness = 35 µm
Power planes = V
EEA
, V
EED
, V
EET
, V
DD
, V
CC
, V
PLUSD
ground plane