Multi Probe Systems for Spherical Near Field Measurement and OTA Testing

Multi Probe Systems for Spherical Near Field Measurement and OTA Testing

Microwave Vision Group (MVG) has introduced two multi-probe systems for spherical near-field measurement and OTA testing, particularly suited for large DUTs and high accuracy applications. In spherical near-field antenna measurements, the number of samples required for characterization is a function of the frequency and physical dimensions of the DUT (device under test). This number of samples must be consistent with the Nyquist criterion, which defines the spacing between measurement points (samples) on the minimum sphere surrounding the DUT at less than half a wavelength. This sets the minimum quantity of points to be measured. Only in this way will sampling in the near field be sufficient to fully process the far-field.

In a spherical antenna measurement performed by a multi-probe test system, the DUT rotates in azimuth while the electromagnetic field surrounding the device is simultaneously scanned by the multi-probe array.

The SG EVO is the latest MVG SG system integrating oversampling from the probe array. It is most suitable for heavy DUTs and high accuracy applications. The unlimited oversampling capabilities synchronized with the electronically scanned probe array of the SG Evo or SG 64 give fast and accurate antenna measurement results in minutes.

Key features of SG EVO:

  • SG EVO is a multi-probe system that operates from 400 to 30000 MHz.
  • The probe system is ideal for spherical near-field measurement and OTA testing, particularly suited for large DUTs and high accuracy applications
  • It incorporates oversampling positioning within the arch, eliminating the need to tilt the device under test (DUT) when oversampling, and consequently avoiding gravitational deflections of the DUT and azimuth positioner, even when testing heavy DUTs.
  • The SG Evo can be configured with multiple parallel receivers, to reduce measurement time, especially when testing multiple frequencies or devices with many potential antenna beam states.

Key features of SG 64:

  • SG 64 is a multi-probe system that operates from 70 to 18000 MHz.
  • It is designed for testing antennas and wireless devices.
  • SG 64 has been developed to measure stand-alone antennas or antennas integrated with subsystems. 
  • It is also ideal for CTIA certi?able measurement facilities.

The angular spacing between two probes of an array, for example, 5.29° for the MVG SG 64, is suitable for small to medium-sized antenna testing at low frequencies. However, for large antennas and/or antennas operating at higher frequencies such as millimeter waves, more measurement points, or samples, are necessary to respect the Nyquist criterion.

Oversampling creates additional virtual probes by a slight mechanical rotation in elevation of the DUT positioner or the probe array. Both oversampling techniques are applied using MVG patented technology. This rotation (± 2.6° max for the SG 64) plus an additional electronic scan of the probe array, introduce more data collection points, resulting in a complete view of the measurement sphere, and thus an accurate analysis capacity.

Oversampling using the DUT positioner requires tilting the device around its phase center and functions well for relatively light and balanced devices. For large, heavy, or oblong antennas and/or operating in millimeter-wave frequencies, oversampling via an elevation rotation of the probe array ensures that the DUT does not experience gravitational deflection during the test. This provides the highest accuracy to meet optimal measurement performance.

Click here to learn more about SG Evo.

Click here to learn more about SG 64.

Oversampling via multi-probe arrayOversampling via goniometer

Publisher: everything RF