Computime Limited CT-EM2531 ユーザーズマニュアル
EM2531/01
ZigBee- Ready RF Transceiver Modules
side. The rest of the PCB board should have a ground plane as large as possible, preferably as
large (in one dimension) as the antenna itself, to make it act as a a reflector mirror to the antenna. A
quarter wavelength Antenna on a PCB must be shorter than the wire antenna due to the influence
of the dielectric material of the PCB. The length reduction depends on the PCB thickness and
material, as well as how close to the edge of the board the antenna is placed. Typical reduction is to
75-90 % but must be found empirically.
The length of a quarter-wave antenna is given in the table below.
large (in one dimension) as the antenna itself, to make it act as a a reflector mirror to the antenna. A
quarter wavelength Antenna on a PCB must be shorter than the wire antenna due to the influence
of the dielectric material of the PCB. The length reduction depends on the PCB thickness and
material, as well as how close to the edge of the board the antenna is placed. Typical reduction is to
75-90 % but must be found empirically.
The length of a quarter-wave antenna is given in the table below.
If, for space reasons, the track is made even shorter than the resonating quarter of wavelength, the
antenna should be matched to 50 ohms using a series inductor and a shunt capacitor.
antenna should be matched to 50 ohms using a series inductor and a shunt capacitor.
PCB Layout Recommendations
For recommended layout pads for the module, please reference
Mechanical Dimensions
The area underneath the module should be covered with solder resist in order to prevent short
circuiting the test pads on the back side of the module. A solid ground plane is preferred.
Unconnected pins should be soldered to the pads, and the pads should be left floating. For the
module version with integrated antenna, the RF pad can be soldered, but the pad should not be
connected further. The two ground pads (pin 10 should be grounded for all variants.)
When using the onboard chip antenna, careful attention is required to the layout of the PCB where
the module is mounted. In Figure 3 a mother PCB is shown with a recommended placement of the
module.
circuiting the test pads on the back side of the module. A solid ground plane is preferred.
Unconnected pins should be soldered to the pads, and the pads should be left floating. For the
module version with integrated antenna, the RF pad can be soldered, but the pad should not be
connected further. The two ground pads (pin 10 should be grounded for all variants.)
When using the onboard chip antenna, careful attention is required to the layout of the PCB where
the module is mounted. In Figure 3 a mother PCB is shown with a recommended placement of the
module.
Figure 3 A recommended placement of the module on a mother PCB (Shaded area is
ground-plane on mother PCB)
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