The Eurofighter Typhoon is a state-of-the-art combat aircraft. BAE Systems has been working with other leading aerospace companies to make sure the Eurofighter Typhoon is unparalleled in design and performance.
The company needed a new test suite for more efficient RF cable characterization within major units of the aircraft. These units, produced at BAE Systems Samlesbury, have high-performance coaxial cables that require testing prior to delivery to ensure that no damage has occurred during installation. Every cable has a different operating frequency, cable length, and routing characteristics, and each of these characteristics impacts performance.
The original method required specialist engineers to conduct testing, but this was expensive, and it limited testing to a small window of time. However, a system in which shop operators conducted the tests would mean more flexibility for production, and the ability to conduct 24-hour-a-day, seven-day-aweek testing.
BAE Systems consulted with TBG Solutions of Sheffield, UK (www.tbgsolutions.com) to define the parameters needed for a more effective test system. The operators, who may have little RF engineering knowledge, would need to conduct all testing requirements for the three product areas. The system would have to automate the test equipment setup routines and test each product fully, including individually testing each cable as required. A system had to be developed that also would implement phase matching and that BAE Systems could easily update for growth. Finally, they wanted the system to use the existing Anritsu scalar analyzer, and the equipment needed to meet strict security requirements for use with potentially sensitive information.
The test system has four major components: the PXI controller, a vector measurement system, the existing Anritsu network analyzer, and the software. The controller communicates with the Anritsu network analyzer through its GPIB interface. This helps the operator measure scalar quantities, such as standing wave ratio and transmission loss, in addition to vector quantities such as phase difference. NI LabVIEW graphical programming software from National Instruments (Austin, TX), along with several LabVIEW toolkits, was used to develop the application.
With NI tools, the new phase-matching, data-capture software was developed. The software was then customized for this particular application. Additionally, advanced custom analysis functions were created to manipulate the incoming data set for comparison against test procedure requirements.
The system consists of two main sections: the PXI chassis, which contains the vector analyzer, and the GPIB interface to the scalar system. The PXI technologies were assembled in the NI PXI- 1045 chassis to create a vector analyzer, which helps operators accurately measure the phase difference between two RF cables in the gigahertz range. The operators connect the cables under test across the two switch cards to minimize any difference in switching path lengths between the two units. The test frequencies are in the gigahertz range, and any delay introduced by either of the switch cards can result in inaccurate measurements.
Because the system is for operators with limited knowledge of RF engineering, it was essential that the system display the right information for the operator to make the correct cable connections without displaying redundant details. This was achieved by using picture rings to illustrate the setup, calibration, and testing steps. These pictures show operators exactly what to connect and where.
The test system also must determine when a system calibration is required. Several test-sequence iterations were attempted to ensure that calibrations were kept to a minimum because they have an adverse effect on test duration. With the resulting sequence, operators can batch test cables at the same frequencies, as long as there are no physical restrictions due to the design of the aircraft.
The vector analyzer was controlled through the GPIB interface to conduct all calibration and test routines without operator interference. This was particularly difficult because the analyzer was in constant use and could not be released for off-site work. The control VIs (virtual instruments) were developed off-site and commissioned on-site when production program time allowed.
Using the LabVIEW Report Generation Toolkit for Microsoft Office, operators can record the results in Excel documents. With these results, aircraft inspectors can see quickly and easily the overall result and keep the graphical detail sheets for future reference.
This article was written by Alastair Kane of TBG Solutions, using National Instruments products. For more information, Click Here