MRF24J40-I MICROCHIP [Microchip Technology], MRF24J40-I Datasheet - Page 54

• Manufacturer Part Number: MRF24J40-I
• Manufacturer: MICROCHIP [Microchip Technology]

A.2
The following guidelines are intended to aid users who
are not experienced in high-frequency PCB layout
design.
FIGURE A-9:
• It is important to keep the original PCB thickness
• The first layer width of a 50Ω characteristic
• Avoid having microstrip lines longer than 2.5 cm,
• Except for the antenna layout, avoid sharp
• Digital lines by definition are prone to be very
DS39776A-page 52
MRF24J40
since any change will affect antenna performance
(see total thickness of dielectric) or microstrip
lines characteristic impedance.
impedance microstrip line is 12 mils.
since that line might get very close to a quarter
wave length of the working frequency of the board
which is 3.0 cm, and start behaving as an
antenna.
corners since they can act as an antenna. Round
corners will eliminate possible future EMI
problems.
noisy when handling periodic waveforms and fast
clock/switching rates. Avoid laying out a RF signal
close to any digital lines.
PCB Layout Design
Note:
FOUR BASIC COPPER FR4 LAYERS
Care should be taken with all ground lines to prevent breakage.
Advance Information
Signal Layout, Thickness = 1.8 mils
Dielectric ε = 4.5, Thickness = 7 mils
RF Ground, Thickness = 1.2 mils
Dielectric ε = 4.5, Thickness = 19 mils
Power Line Routing, Thickness = 1.2 mils
Dielectric ε = 4.5, Thickness = 7 mils
Ground, Thickness = 1.8 mils
The printed circuit board is comprised of four basic FR4
layers: signal layout, RF ground, power line routing and
ground (see Figure A-9). The guidelines will explain the
requirements of these layers.
• A via filled ground patch underneath the IC
• A power supply must be distributed to each pin in
• Decoupling each power pin is a tedious task,
• Passive components (inductors) must be in the
Figure A-10 and Figure A-11 illustrate the ground and
power plane for the RF board.
transceiver is mandatory.
a star topology and low-ESR capacitors must be
placed at each pin for proper decoupling noise.
especially when the noise is affecting the perfor-
mance of the transceiver in a specific bandwidth.
Usually, low value caps (15-27 pF) combined with
large value caps (100 nF) will cover a large
spectrum of frequency.
high-frequency category and the SRF (Self-
Resonant Frequency) should be at least two
times higher than the operating frequency.
© 2006 Microchip Technology Inc.