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Applications information

BT-STA2425

10/13

Whichever type of antenna is chosen, the connection from the RF antenna pin,

BT_ANTENNA, must follow good RF design practice and maintain the characteristic

Figure 7.

Antenna connection

50

Ω matching depends on various factors, for instance:

"

the type of board material, for example FR4

"

the electrical characteristics of the board, for example the relative permittivity,

εr, at

2.4 GHz

"

the mechanical dimensions of the board and tracks, for example PCB thickness, track

and ground thicknesses, track width.

As an example, using a 1-mm thick FR4 board (

εr = 4.3 at 2.4 GHz) with copper thickness of

41 µm, the required track width for 50-

Ω strip-line is 1.9 mm (microstrip-type calculation)

Figure 8.

Parameters for track matching

Tools for calculating the characteristic impedance based on the physical and mechanical

characteristics of the PCB can be easily found on the internet.

Traces with Z0 = 50 ohm

Antenna connection

RF out pin

Antenna connection

PCB

thickness

Trace width

Reference ground

Parameters for trace matching

Trace thickness

Track thickness

Reference ground

PCB

Track width

thickness