RC11xx(HP)-TM
RC25xx(HP)-TM
RC17xx(HP)-TM
2016 Radiocrafts AS
RC11xx(HP)/25xx(HP)/17xx(HP)-TM Data Sheet rev. 1.48 Page 69 of 86
2016 Tiny Mesh AS
Radiocrafts
Embedded Wireless Solutions
Antenna Connection
The antenna should be connected to the RF pin. The RF pin is matched to 50 Ohm. If the antenna
connector is placed away from the module at the motherboard, the track between the RF pin and the
connector should be a 50-Ohm transmission line.
On a two layer board made of FR4 the width of a micro strip transmission line should be 1.8 times the
thickness of the board, assuming a dielectric constant of 4.8. The line should be run at the top of the
board, and the bottom side should be a ground plane.
Example
: For a 1.6 mm thick FR4 board, the width of the trace on the top side should be 1.8 x 1.6 mm =
2.88 mm.
The simplest antenna to use is the quarter wave whip antenna. A quarter wave whip antenna above a
ground plane yields 37-Ohm impedance and a matching circuit for 50 Ohm is usually not required.
A PCB antenna can be made as a copper track where the ground plane is removed on the backside.
The rest of the PCB board should have a ground plane as large as possible, preferably as large as the
antenna itself, to make it act as a counterweight to the antenna. If the track is shorter than a quarter of a
wavelength, the antenna should be matched to 50 ohms.
The lengths of a quarter-wave antenna for different operational frequencies are given in the table below.
Frequency
[MHz]
Length
[cm]
433
16.4
865-867
8.2
868
8.2
915
7.8
2450
2.9