MRF89XAM8A Datasheet, PDF (16/34 Pages) Microchip Technology – 868 MHz Ultra-Low Power

MRF89XAM8A
FIGURE 2-9:
PCB LAYER STACK UP
0.032”
± 0.005”
1/2 oz. Copper
8 mil FR4
1/2 oz. Copper
12 mil FR4
1/2 oz. Copper
8 mil FR4
1/2 oz. Copper
Top Copper
Ground Plane
Power Plane
Bottom Copper
2.3 PCB Antenna
The PCB antenna is fabricated on the top copper trace.
Figure 2-10 illustrates the trace dimensions. The layers
below the antenna have no copper traces. The ground
and power planes under the components serve as a
counterpoise to the PCB antenna. Additional ground
plane on the host PCB will substantially enhance the
performance of the module. For best performance,
place the module on the host PCB by following the
recommendations given in the Section 1.2, Mounting
Details.
The PCB antenna was designed and simulated using
Ansoft Designer^® and HFSS™ 3D full-wave solver
software by ANSYS Inc. (www.ansoft.com). The goal of
the design was to create a compact, low-cost antenna
with the best radiation pattern. Figure 2-11 illustrates
the simulation drawing and Figure 2-12 and
Figure 2-13 illustrates the 2D and 3D radiation
patterns. As shown by the radiation patterns, the
performance of the antenna is dependant upon the
orientation of the module. Figure 2-14 illustrates the
impedance simulation and Figure 2-15 illustrates the
simulated PCB antenna VSWR. The discrete matching
circuitry matches the impedance of the antenna with
the SAW filter and MRF89XA transceiver IC.
FIGURE 2-10:
PCB ANTENNA
DIMENSIONS
2.5mm
16.8mm
1.0mm
1.1mm
8.4mm
0.5mm
DS70651A-page 14
Preliminary
© 2010 Microchip Technology Inc.