MICRF112 datasheet(15/20 Pages) MICREL

15 / 20 page

Micrel, Inc.

MICRF112

December 2011

M9999-120911

(408) 944-0800

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

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.

MICRF112 데이터시트(PDF) 15 Page - Micrel Semiconductor