Planar Helix normal mode
Image of the Planar Helix normal mode.

This antenna is similar to the antenna used on board #11 in design note DN031 from Texas Intruments. The antenna is typically used for wireless communication in the 915 MHz ISM band. It is advantageous because of its low profile compact size, mechanical strength, and the fact that it can be integrated onto to the same printed circuit board as other electronics.

Compared to its wire counterpart in Antenna Magus, this robust substrate mounted helix has a similar diameter, but reduced physical height.

The radiation pattern resembles a doughnut with a 3 dB beamwidth of approximately 90 degrees in the phi = 90° plane, and maximum radiation in the broadside direction (the plane normal to the helix axis, or phi = 0° plane).

Typical reflection coefficient versus frequency (50 Ω system) with and without matching and typical radiation pattern at the centre frequency