Airbus Defence and Space

ANTENNA & PAYLOAD MEASUREMENT

Compact Range Measurement Services

The services are performed in an indoor test range for testing of large weight multi-beam antennas on subsystem and payload level. Further measurement services for radar-cross-section and antenna performance of scaled aircrafts, helicopters and missiles can be offered.


The Airbus Defence and Space Compensated Compact Range (CCR 75/60) at Ottobrunn is an in-door far-field test range for testing of large and multibeam antennas as well as radar cross-section measurements of structures and scaled models of aircraft, missiles, helicopters, etc. Special software was developed to analyze and compare different compact range principles and to design an optimum compact range fitting in the anechoic chamber. The result is a compact range with two double curved reflectors providing a quiet zone of 5 x 5.5 x 6 m. The design is of the front-fed Cassegrain type. The cross-polarization is only determined by the feed and negligible contributions of the serrations, allowing cross-polarization figures of <-40 dB within the quiet zone. For the co-polar field distribution within the quiet zone an edge taper of typically 0.6 dB at the sub-reflector edge is assumed.

The geometry of the serrations, with a length of 1.50 m, is determined by a GTD (Geometrical Theory of Diffraction) analysis program optimizing the geometry under the condition that the quiet zone is kept free from edge diffracted rays of the reflectors/serrations.

Special seismic blocks which are decoupled from the building construction are provided for the two reflectors, the turntable and the feedhorn positioner. The feedhorn is located in a special chamber (access by door on 1st floor) 5.25 m above the ground floor and is linked by a large opening to the clean area of the CCR hall.

Planar movement of the feedhorn by ± 1m allows highly accurate beam scanning of about ±3° without significant disturbance of the phase and an amplitude distribution in the quiet zone. Consequently, measurements can be performed without any movement (rotation) of the test device.

A further test objective directly related to this performance is the capability of C/I measurements of multiple spot beam antennas. These isolation measurements can be performed by simultaneous operation of more than one feedhorn at different positions in the focal region area.

The high surface accuracy of the reflectors (RMS < 25 mm) required the installation of a special air conditioning system providing a laminar air flow in the front and back of the reflectors.

The size of the absorbers is selected according to the varying radiation properties in the chamber and the lowest operation frequency of 1 to 2 GHz.

The test range was qualified in 1989 for frequencies up to 200 GHz (partly under ESTEC contract) and is fully operational since then. In 2001, within the ADMIRALS study for ESA/ESTEC, measurements were also performed up to 503 GHz.

For antenna tests the CCR Facility is instrumented with a dedicated five axis precision turn table which guarantees a high degree of freedom. For payload tests a heavy duty positioner is available.

The RF-instrumentation is based on the HP 8530 System and fast switching frequency synthesizers. The high speed TTL interface between turn table controller and RF equipment allows frequency multiplexing and transmit and receive multi channel measurements.


End to End Radiated Performance Tests on Satellite Level
In addition to the above described antenna test an end to end radiation test at satellite level could be necessary for the customer. Airbus Defence and Space can offer its experiences in this field to give best support to the customer.

The CCR has the special feature to generate multiple quiet zones to be centered around the respective satellite antennas. The multiple quiet zones are generated by laterally shifted positioning of the range feed outside the focal point, resulting in a semi-plane wave. The high quality of the multiple quiet zones - or the so called scanned plane waves - is caused by the long focal length of the compact range reflector layout.

This scanning capability introduces the opportunity of creating two or more independent quiet zones in different positions (e.g. for transmit and receive antenna simultaneously), operating at different frequencies and polarization’s.

Most of the payload parameters can be measured directly or have to be calculated from a set of measurement values. Thus it is possible with this test facility and this test configuration to perform payload antenna and transponder tests in a very short time frame and with high measurement accuracy.

Due to this excellent scanning performance of the Compensated Compact Range this type of facility is best suited for end to end payload tests. Companies like Space Systems Loral, Lockheed Martin and Alcatel did theses type of measurements for INTELSAT-8, INTELSAT-9, INTELSAT-X and EUTELSAT programs in exact the same type of measurement facility.

The end to end radiated test will be performed in the above described Compensated Compact Range. A typical test flow for payload tests is shown below.

For high power satellite testing, the test facility is equipped with a large high power absorber wall and an infrared monitoring system for safety reasons.

 

Main Characteristics of the Compensated Compact Range CCR 75/60 OTN:

Measurement Capabilities

Test Objectives Pattern, Gain, EIRP, C/I, Payload Performance,

RF-Sensing, Radar Cross Section

Frequency Range 1.5 - 200 (500) GHz
Polarization Linear, Circular
Operation

Fully computer controlled measurement system:

  • 24 h a day operation
  • Ultra-high speed data acquisition
  •  
Frequency, polarization and beam multiplexing

Test Antenna Positioner

5-axis (pol/el/az/lin/az)

Antenna under Test Size / Mass

< 5.5 m

Antenna Mass

< 1 - 4 tons

 

 

Quiet Zone Performance (1.5 - 50 GHz)

 

Dimensions (W x H x D) 5 x 5.5 x 6 m
Max. Amplitude / Phase Ripple ± 0.5 dB / ± 5
Max. Cross-polarization -40 dB
Typical Measurement Accuracy ± 1 dB @ - 30 dB signal level

 

Geometrical/Mechanical Characteristics

Main Reflector (W x H) 7.5 m x 6.0 m (exclusive Serrations)
Subreflector (W x H) 5.4 m x 5.3 m (exclusive Serrations)
Serration Length 1.5 m
Reflector Surface Accuracy 25 μm RMS
Positioner Accuracy 0.003 degree
Bore Sight Accuracy 0.014 degree


Chamber Conditions

Anechoic Chamber (L x W x H) 24.8 m x 17.5 m x 10.8 m
Chamber Temperature 21 ± 2°
Relative humidity 30% < h
rel < 70 %

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