A Dual-Receiver Method for Simultaneous Measurements of Radome Transmission Efficiency and Beam Deflection

Authors: Robert Luna, Tom Thomas, Dean Darsey, John Vortmeier

Characterization of radome performance involves measuring the radome-induced microwave signal attenuation and change in propagation direction. Transmission efficiency (TE) is a measurement of the percentage of microwave energy passing through the radome. Beam deflection (BD) is a measurement of the change in the direction of propagation of the energy as it passes through the radome.

Typical instrumentation configurations include one or two receivers interfaced with a monopulse antenna through a tracking loop. Tracking is mechanized at either the transmit or receive location.

The difficulty with these configurations is the complexity required to implement, coordinate, monitor, and measure tracking with sufficient speed and accuracy. MI Technologies has developed and tested a relatively inexpensive and simple dualreceiver method that provides high accuracy and fast test time. A radome measurement system of this configuration is installed and has been successfully tested for The Boeing Company.

 

A Highly Automated Approach to Obtaining Accurate Circularly Polarized Antenna Gain

Author: Marion C. Baggett

At a Department of Defense antenna measurement laboratory, an important measurement is the accurate measurement of gain for circularly polarized antennas. An additional requirement is that a wide population of engineers and technicians that do not spend a significant amount of time using the facility make the measurements as they test the antennas for their projects. The objective was to create a highly automated, accurate test structure that was easily used by visiting engineers to make high quality measurements. Consistency of results across the user population was a paramount requirement. This paper describes the instrumentation and software used to meet this objective.

 

Alignment of a Large Spherical Near-Field Scanner using a Tracking Laser Interferometer

Authors: Scott Pierce, Charles Liang

In this paper, we describe the process used to align a large spherical near-field test system. The probe positioner consists of a cantilevered arc design with a probe path radius of five meters and a scan angle of 180°. The AUT positioner consists of an MI Technologies Model 51230 azimuth positioner with a high-precision encoder. The system is aligned using an SMX Tracker 4000 tracking laser interferometer.

Alignment into a spherical system is achieved by initially defining two cylindrical systems; a primary probe positioner based system and a secondary, AUT positioner based system. Sources of mechanical error in each of these systems are identified and techniques used to control these error sources are described.

 

An Augmented Three-Antenna Probe Calibration Technique for Measuring Probe Insertion Phase

Authors: Aksel Frandsen, Doren W. Hess, Sergey Pivnenko, and Olav Breinbjerg

Probe calibration is a prerequisite for performing high accuracy near-field antenna measurements. One convenient technique that has been used with confidence for years consists of using two auxiliary antennas in conjunction with the probe-to-be-calibrated. Inherent to this technique is a calibration of all three antennas. So far the technique has mostly been applied to calibrate for polarization and gain characteristics. It is demonstrated how the technique can be extended to also measure an antenna’s phase-versus-frequency characteristic.

 

Antenna Alignment in a Near-Field Facility

Authors: Mart Hagenbeek, Arnold R.Boomstra

This paper will discuss the application of alignment techniques and tools in a near-field test facility. Standard alignment telescopes are not directly applicable in a general purpose near-field set-up because of limited dimensions of such a facility, where a direct target is not available and is often to close to the antenna to be in the focus region of the telescope itself.

Self-made optical tools will be presented to overcome this problem, including some estimates about the required and obtained accuracies. Using these tools is demonstrated as a fast and accurate way to align an antenna to the measurement set-up.

 

Antenna Pattern Comparison between an Outdoor Cylindrical Near-Field Test Facility and an Indoor Spherical Near-Field Antenna Test Facility

Authors: Jeffrey Fordham, Mike Scott

A new spherical near-field probe positioning device has been designed and constructed consisting of a large 5.0 meter fixed arc. This arc has been installed in a near-field test facility located at Alenia Marconi Systems on the Isle of Wight, UK. As part of the near-field qualification, testing was performed on a ground based radar antenna. The resultant patterns were compared against measurements collected on the same antenna on a large outdoor cylindrical near-field test facility also located on the Isle of Wight. These measurements included multiple frequency measurements and multiple pattern comparisons.

This paper summarizes the results obtained as part of the measurement program and includes discussions on the error budgets for the two ranges along with a discussion on the mutual error budget between the two ranges.

 

Evaluation of Radome Performance from Cylindrical Near-Field Measurements

Authors: W.C. Dixon, Daniël Janse Van Rensburg

This paper describes the installation and implementation of a Cylindrical Near-field Test Facility at Chelton Radomes Ltd, Stevenage, (formerly British Aerospace Systems and Equipment Ltd.), in the UK for the testing of large radome/antenna combinations. Test site commissioning and validation activities to determine measurement accuracy & repeatability for the radome performance parameters of transmission loss and boresight error, are discussed. Test data from actual measurements are presented.

 
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