AN3394

Application to DEMO-CR95HF-A demonstration board

Doc ID 018754 Rev 5

13/29

2

Application to DEMO-CR95HF-A demonstration

board

This section describes in detail the numerical application corresponding to the DEMO-

CR95HF-A demonstration board.

If your application requires a different antenna, use the DEMO-CR95HF-A Gerber files

available for http://ww.st.com to design your own antenna. Guidelines on how to design an

antenna can be found in Section 4: Main criteria for key antenna design.

2.1

Antenna parameters

This section describes part 3 of circuit shown in Figure 9: CR95HF parallel matching circuit

intermediate simplification.

2.1.1

Antenna serial equivalent model

Figure 11.

Antenna parameters without EMI filter

Where values from Equation (I.4) give:

The capacitance is included in the inductance presented above. As a result:

Equation (II.1)

Where

Antenna quality factor, defined with antenna parameter.

IM(x):

Imaginary part of the complex number x.

RE(x): Real part of the complex number x.

ω:

Resonance pulsation [rad/s].

Q

A

IM Z

load

()

[]

RE Z

load

()

---------------------------------

ω L

A

×

R

A

-----------------

61 1

,

=

=

=