Digital Signal Processing Reference
In-Depth Information
Table 5.3
A Sampling of Alternate Laminate Systems
Chemistry
Product Name
Dk/LT at 10 GHz
PPO
Megtron 6
3.4/0.004
BT
G200
3.65/0.015
Polyamide
N7000-1
3.8/0.016
Cyanate Ester
N8000
3.5/0.011
Ceramic
RO4003
3.4/0.0022
used in RF applications. The RO4000 series of materials from the Rogers Corpora-
tion [14] are reinforced hydrocarbon/ceramics that have low and stable
Dk
values.
Theses are popular in high-performance digital and RF applications.
5.4
Circuit Board Traces
The copper conductors used to interconnect circuits (the traces) are formed either
on the boards surface (the outer layers) or buried within the circuit board material
(inner layers). Outer layer traces are called microstrip (or microstripline); inner
layer traces are called stripline.
The four basic topologies used to interconnect digital circuits are shown in Fig-
ure 5.4. Microwave and RF designers use additional topologies that are not shown.
The outer layer traces can either be exposed microstrip or embedded microstrip,
and the inner layers can be either stripline or dual stripline.
Soldermask
Trace
Dielectric
Plane
Embedded
microstrip
Exposed microstrip
Stripline
Dual
stripline
Figure 5.4
Types of circuit traces used to connect digital circuits. Microstrips are formed on the
outer layers, while inner layers create striplines.
