NPL and NIM worked in collaboration to design and build an extrapolation range for antenna measurements. Over the course of the project, the NPL team made multiple site visits, produced over 300 design drawings, and manufactured and tested hundreds of parts. In addition to the hardware supplied, the project also included the provision of software, procedures, validation and training.
The extrapolation range is a chamber lined with radiation absorbing material in the form of foam pyramids, loaded with carbon particles. It is essentially a reflection-free environment for testing microwave antennas. The measurement system comprises a computer-controlled carriage that moves on a precision rail guidance system to vary the separation between the antennas, while recording the received power. The data obtained is processed to obtain the gain and polarisation properties of the antenna under test.
The equipment was shipped to China and installed by a team from NPL and the newly-completed extrapolation range produced excellent results. The performance of the precision rails, an essential part of the extrapolation range, was much better than expected, leading to very low uncertainties in antenna parameter measurement, along with optimised system configuration.