micrf112 Micrel Semiconductor, micrf112 Datasheet - Page 15

• Manufacturer Part Number: micrf112
• Description: Qwikradio Uhf Ask/fsk Transmitter
• Manufacturer: Micrel Semiconductor

Output Matching Network
Part of the function of the output network is to attenuate
the second and third harmonics. When matching to a
transmit frequency, care must be taken not only to
optimize for maximum output power but to attenuate
unwanted harmonics.
Layout Issues
PCB Layout is of primary concern to achieve optimum
performance and consistent manufacturing results. Care
must used on orientation of components to ensure they
do not couple or decouple the RF signal. PCB trace
length should be short to minimize parasitic inductance,
(1 inch ~ 20nH). For example, depending on inductance
values, a 0.5 inch trace can change the inductance by as
Micrel, Inc.
March 2008
15
much as 10%. To reduce parasitic inductance, the use of
wide traces and a ground plane under signal traces is
recommended. Vias with low value inductance should be
used for components requiring a connection-to-ground.
Antenna Layout
Directivity is affected by antenna trace layout. No ground
plane should be under the antenna trace. For consistent
performance, components should not be placed inside
the loop of the antenna. Gerbers for Figure 7, with a
suggested layout, can be obtained on the Micrel web site
at: http://www.micrel.com.
[phone]
M9999-031008
MICRF112