BAE Systems Uses PXI and NI LabVIEW to Develop an Efficient RF Cable Test Suite for the Eurofighter Aircraft

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"We saved more time than originally anticipated, and the operation of the final product is so simple that operators need only minimal training. In fact, this method of testing has proven to be so successful that other BAE Systems departments are considering using this solution to meet RF testing requirements for high-performance coaxial cables."

- Alastair Kane, TBG Solutions

The Challenge:
Creating a new test suite for BAE Systems to efficiently characterize RF cables within major units of the Eurofighter aircraft.

The Solution:
Using the PXI/CompactPCI platform and National Instruments LabVIEW software to design a simplified test system that increases productivity by facilitating more flexible testing.

Author(s):
Alastair Kane - TBG Solutions
John Duncalf - BAE Systems

The Eurofighter Typhoon is a state-of-the-art combat aircraft developed in cooperation with Germany, Italy, Spain, and the UK. This sophisticated, next-generation fighter has been engineered to meet military needs for generations to come. BAE Systems, a leader in these types of joint programs, has been working with other leading aerospace companies to make sure the Eurofighter Typhoon is unparalleled in design and performance.

Developing an Effective Test Suite for RF Cables

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-a-week testing.

BAE Systems consulted with us at TBG Solutions 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. We needed to develop a system that also would implement phase matching and one that BAE Systems could easily update for growth. Finally, we wanted the system to use the existing Anritsu scalar analyzer, and we needed the equipment to meet strict security requirements for use with potentially sensitive information.

System Design and Configuration

The test system we constructed 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. We used NI LabVIEW, along with several LabVIEW toolkits, to develop the application.

With NI tools, we developed the new phase-matching, data-capture software. We then customized this software for this particular application. Additionally, we created advanced custom analysis functions to manipulate the incoming data set for comparison against test procedure requirements. We then used the data to produce the test report.

The system consists of two main sections – the PXI chassis, which contains the vector analyzer, and the GPIB interface to the scalar system.

We assembled the PXI technologies 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.

All of the system hardware is stored in an existing 3U rack–mountable, rugged container for increased protection.

Overcoming Design Challenges

During the design of the control software, we had to overcome several challenges. 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. We achieved this by using picture rings to illustrate the setup, calibration, and testing steps. These pictures show operators exactly what to connect and where.

We needed to tailor the system to BAE Systems’ specific layout design requirements and build it under tight security. Sections of the test procedure are considered sensitive, so we designed and implemented the software without knowing the full test criteria. For sensitive parts of the test, the operator must enter those parameters before beginning each test. This means all information is kept in volatile memory and is lost if the system is shut down, thus meeting BAE Systems’ security requirements.

The test system also must determine when a system calibration is required. We attempted several test-sequence iterations to ensure we kept calibrations 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.

We controlled the vector analyzer 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. We developed the control VIs off site and commissioned them on site when production program time allowed.

Producing Easy-to-Use Results

The combined system produces results for all tests conducted on each product, and the operator can produce a printout anytime.

The system displays the results in graphical and tabular formats and produces a detailed cover sheet that shows the time, date, operator, and product identifier for the test subject. The graphical format illustrates all values for the required 401 test points, with limit lines to show the pass/fail criteria. The tabular format shows the maximum values achieved and includes a pass/fail box for clarity.

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.

Simplifying the Test System

BAE Systems laid out the system specification in the early stages of this project; however, we understood that this would be a development project. The system has met or exceeded the original specifications and demonstrates that it is possible to automate RF testing without the operators having RF theory knowledge.

We saved more time than originally anticipated, and the operation of the final product is so simple that operators need only minimal training. In fact, this method of testing has proven to be so successful that other BAE Systems departments are considering using this solution to meet RF testing requirements for high-performance coaxial cables.

Author Information:
Alastair Kane
TBG Solutions
Unit 9, Century Street Industrial Estate
Don Valley, Sheffiled 59 5DX
United Kingdom
Tel: 0114 261 8111
Fax: 0114 256 2456
alastair.kane@tbg-solutions.com

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