Application information

SPBT2532C2.AT2

22/27

Doc ID 023461 Rev 1

8.2

Antenna coupling

Despite the type of antenna chosen, the connection between the RF out pin and the

antenna must be realized to get the maximum power transfer.

As a general rule, the characteristic impedance (Z0) of the connection must be fixed at the

value of 50

Ω. The connection trace must be matched to respect such a condition.

50

Ω¸ matching depends on various factors and elements that must be taken into

consideration:

●

Type of material, i.e. FR4 or others

●

The electrical characteristics of the material, among them the electric constant,

2.4 GHz

●

PCB and traces mechanical dimensions:

–

PCB thickness

–

Reference ground thickness

–

Trace width

–

Trace thickness.

8.3

Example of trace calculation

Example of strip line calculation:

●

To get a strip line of 50

Ω, using a 1 mm thick FR4 board, with an

with Cu thickness of 41

µm, the strip line width must be 1.9 mm (micro strip type

calculation).

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

characteristics of the PCB, can be easily found online.

Figure 13.

Parameters for trace matching