Waveguide Systems for Calibrating SAR Test Probes
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NPL have developed calibration probes and Wave Guide Systems to measure the specific absorption rate (SAR) of exposure of humans to radio frequency fields in the frequency range 100kHz to 10GHz.
Electric field probes are used to determine the specific absorption rate (SAR) of radio frequency energy in liquid phantoms for exposure safety assessment and product compliance testing of devices, for example mobile phones.
NPL offers waveguide systems for calibrating these probes in liquid. The probe is positioned in the waveguide using a precision linear translation stage with a 1-micron resolution magnetic encoder, and the probe can be rotated for axial isotropy assessment.
The waveguide and positional stage are mounted on a rigid support stand capable of housing up to four waveguides, so that a range of frequency can be tested. Each waveguide has a multi-layer dielectric-matching layer, and this gives superior input return loss compared to single layer windows.
For longevity, the upper dielectric is PEEK, as this has excellent chemical resistance and low moisture absorption, and the waveguides have corrosion resistant coatings. The systems come with calibration software suitable for IndexSAR and SPEAG probes, although other makes can be accommodated at request.
| Tuned frequencies available |
900 MHz, 1450 MHz, 1800 MHz, 1950 MHz, 2450 MHz, 5.2 GHz, 5.8 GHz. |
| Capacity per stand | 4 waveguides |
| Input return loss | > 25 dB |
| Positional display resolution | 1 micron |
| Typical calibration uncertainties | ± 8% |
| Compatibility | SPEAG and IndexSAR probes (other makes at request) |
On-site installation and staff training for these systems is also available.