Speakers
Description
The increasing complexity and stringent performances required in RF instruments and payloads demand more and more that functional verification be performed on the integrated satellite under the most realistic operational conditions.
Due to accuracy and testing speed, Near field methods are very attractive techniques for such testing. However, in standard Near field testing of small antennas on large platforms, the minimum number of samples is determined by the size of the entire satellite. This requirement leads to very long testing times even for smaller antennas.
During the frame of this activity, an advanced RF test methodology that aims at minimizing the duration and the cost of both preliminary preparation and test campaigns has been developed and validated with actual measurements. The time efficiency with respect to traditional measurements is achieved through the exploitation of measurements and simulations combined together.
The developed methodology allows to perform fast antenna measurements in the target environment applicable to Antenna Integration and Test Verification (AIT/AIV). The methodology is an add-on to standard near field measurements ranges and is the best choice for fast analysis, like verification testing, while maintaining a reasonable level of accuracy.
Two methodologies have been developed and validated:
• Stand-alone measurements methodology. This approach is based on reconstruction, by Equivalent Currents, using INSIGHT, of the measured antenna by itself. Standard numerical computational tools are used to include the effect of the surrounding environment.
• Embedded measurements methodology. The antenna and platform is measured using a reduced number of measurement points. The expansion base is derived from numerical simulation of the platform. This approach is particularly efficient when applied to small antennas in big scenarios.
Stand-alone measurements methodology has been validated with actual measurements of a GNSS antenna on ESA Sentinel Satellite.
The embedded measurements methodology has been validated with small X-band antenna on a large satellite mock-up. The number of samples is reduced with a factor close to 9, while maintaining a reasonable level of accuracy with respect to standard measurement, making this technique suitable for verification testing. No electromagnetic (EM) or mechanical information about the design of the antenna is needed (no intellectual property issues): the radiating source is modelled using a small number of EM sources placed on a volume enclosing it. The number of EM sources is equal to the number of unknowns. The scattering part is analyzed with raytracing (Satsim software) and Full Wave methods on an approximate CAD model of the satellite obtained through 3D model reconstruction by multiple images. The reduced number of measured points are used to compute the weighting coefficients to reconstruct the complete field.
The methodology can be employed for all missions embarking an antenna and can be applicable to any standard NF or FF measurements systems. The minimization of duration and cost of test campaigns is useful to reduce time-to-flight of any new space missions, with a very wide field of applications.
| ESA Technical Officer | Damiano Trenta |
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