Read range estimate

AN3394

16/29

Doc ID 018754 Rev 5

3

Read range estimate

This section explains how to obtain the maximum read range between tag and CR95HF.

3.1

Magnetic field calculation

For a rectangular antenna, the radiated magnetic field can be estimated using the following

formula:

Figure 15.

Rectangular antenna

Equation (III.1)

Where

a:

Antenna length. [m]

b:

Antenna width. [m]

d:

Distance from tag to antenna. [m]

N:

Number of turns

i:

Current in the antenna. [A rms]

Magnetic field. [A/m rms]

rms:

Root mean square.

H

(, )

2N

×

i

×

a

×

b

×

π

a

2

b

2

4d

2

×

++

()

×

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

1

a

2

4d

2

×

+

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

1

b

2

4d

2

×

+

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

+

⎝⎠

⎛⎞

×

=