The 3D Spherical Coordinate System

The 3D Spherical Coordinate System

Understanding Spherical Coordinates

Antenna Test Lab Co performs 3D spherical evaluations using Phi axis (roll) and Theta (turntable) stepping per the “Great Circle Cut System”. This way, native results are available directly in the standard preferred spherical coordinate system.

This enlargeable figure shows the Theta axis (turntable or azimuth control) with the Phi axis “roll positioner” (or elevation control) on top of it. Our positioners are fiber-optically controlled, and made of all plastic materials so as not to absorb RF energy. The rate of turn is 3 RPM (20 seconds) with a positioning accuracy of better than 0.2 degree. Our Photos of the laboratory show sample mounting arrangements for various items. Our chamber antennas can cover 300 MHz to 40 GHz. For increased throughput speed, our lab uses three-port VNA measurements and quad ridge horns to simultaneously take vertical and horizontal polarized antenna gain measurements.

Measurements are logged in tables of Theta and Phi spherical coordinates, per IEEE Standard 149-2021, “Test Procedures for Antennas”. The standard IEEE antenna coordinate system is illustrated below. The spherical coordinates relate to the Cartesian axes as shown in the click-to-enlarge diagram to the left.

Evaluate Your Antenna

Ready to find out more about your antenna … partner with an antenna evaluation company and never be “in the dark” again! Contact us here.