ISM 433MHz Helical Antenna

Small helical antennas for the 433 MHz ISM band are a good example where we need advanced software that has the ability to model:

• curved wires with exact description of the helix contour

• very close wires, spaced a fraction of the wire radius

• horizontal wires almost touching the ground plane

• bent wires at right angles or less

• short segments, below 0.001 wavelength

• thick wires by means of Exact Kernel instead of thin-wire approximation

AN-SOF includes all these features.

In this example, a perfect ground plane is used to get the input impedance: 48 Ohm, very close to the 50 Ohm of the antenna datasheet. We must subtract 3 dBi from the gain to obtain the gain in free space. It is a simple model, but it coincides very well with reality.

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