Nearfield Measurement Services

Antenna measurements will be performed in the near-field test range, which is a qualified and operational in-door test range for qualification and acceptance testing of light-weight spacecraft antennas. Full computer aided data acquisition and automatic control of all test equipment, such as linear scanner, turntable, transmitter and receiver allow around the clock operation of the facility. For the near–field/far-field transformation, full probe correction is applied. The probe measurement and calibration including the determination of the probe coefficients is performed in a special test chamber. The control software and the highly accurate scanner with laser interferometer and laser controlled x/y-alignment was an in-house development of EADS itself. The linear scanner provides a scan height of 8 m and is basically applied for cylindrical near-field scanning. Provisions are integrated to extend the facility to a 8.0 x 9.0 m planar scanner. The scanner tower is sliding on two 12 m long rails leveled with an accuracy of 0.05 mm. The performance data of the linear scanner and the turntable are summarized in the following.

 

The chamber has four alignment windows in a height of approx. 6 m, which allow

• Easy alignment of the near-field facility itself, i.e. alignment of turntable axis w.r.t. the scanner axis, etc.
• Alignment of the test objective w.r.t. the reference co-ordinate system given by the test facility, e.g. the co-ordinate system of the turntable
• Measurement of the reflector surface of a large, light-weight reflector antenna, e.g. an unfurlable antenna in the actual test position (orientation of vector of gravity not changed) without disturbing the test environment.