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Using Calibration to Optimize Performance in Crucial Measurements
Builders and users of RF/microwave cable assemblies must specify and guarantee the performance of their cables for characteristics such as return loss, insertion loss, phase stability and VSWR. Cables must be 100 per cent tested in order to ensure specification compliance and optimum performance. Typically, critical measurements such as these require highly skilled engineers to operate complex vector network analyzers (VNA). The high cost of testing is a major challenge when considering tight budgets and margins. Utilizing DCM Industries’ 30+ years of cable testing experience, the Model COAX-3000 Test System automates VNA measurements of RF/microwave cable assemblies. Automation is so complete that unskilled operators may now perform accurate, complex measurements, with minimal training.
At the heart of the COAX-3000 system is DCM-developed software that turns a complicated, general-purpose VNA into an application-specific, plug-and-play measurement solution. The software provides complete system configuration, calibration management, test reporting and data base management, all with no user programming. The software can be used with most major VNAs and can be easily upgraded to include any VNA using the appropriate instrument drivers.
Unlike programming languages such as C++, VEE and LabVIEW, the COAX-3000 is a turnkey solution ready to perform RF measurements with no programming required. The COAX-3000 eliminates the extensive development time and costs associated with other methods by incorporating the company’s expertise in VNA measurements, de-embedding techniques and application program development. The result is a plug-and-play test solution that is flexible, user friendly and ready to use.
System setup is a simple, one-time process using graphic user interface (GUI) panels (see Figure 1). Enter a few key parameters such as frequency range, number of test points, type of test and specification limits, and the program automatically sets up the pass/fail limits, determines the type of calibration needed and configures the VNA for optimum performance. The user is guided through the entire measurement process without having to touch a VNA button.
For system control and security, a three level password-protected login is included. Only qualified top-level users have authority to generate and edit specification files and manage data. Password protected login means that the time-consuming configuration files are protected from unauthorized changes.
The COAX-3000 software contains a number of advanced measurement capabilities and can be customized by the user through use of the Screen Editor. Data entry fields can be defined for specific customer parameters such as part identification, operator ID, batch number, etc. The Screen Editor also provides an easy method of customizing measurement fields for special device characteristics. As a result, the program can easily be re-configured by the user to accommodate nearly all possible measurement parameters for any type of two-port device.
Complete Data File Management
The Data File Manager within the COAX-3000 software stores a complete history of device measurement data (see Figure 2) and provides extensive analytical tools including cable matching capabilities, data exporting and printout options. Cable matching functions include the ability to match cables with respect to phase, insertion loss and electrical length. After measurements, complete test reports with data summary and multiple graphs are available (examples of some of the test report graphs are shown in Figure 3). With powerful database tools already integrated into the measurement program, it is no longer necessary to export files to an external database program, or to an external computer, for data analysis — a savings of time and added security. However, if data export is required, a one-button conversion program is also provided.
Advanced Calibration and De-embedding
The COAX-3000 provides an automated calibration management system that guides the user to minimize the potential for operator errors. In addition, advanced calibration techniques solve the problem of adapters when measuring cable assemblies. Test engineers are well aware of the increase in measurement errors when adapters are used to measure non-insertable (male-to-male or female-to-female) devices. DCM has developed a system to easily remove adapter effects using mathematically compensated de-embedding techniques.
The COAX-3000 software extracts adapter errors by utilizing modeled adapters during the measurement process, as shown in Figure 4. After calibration, the appropriate adapter is attached, the characterization file is downloaded, and the effects are mathematically extracted. The COAX-3000 software does this transparently, and measurement data is presented with the effects of the adapters automatically removed. The benefits of this technique include improved accuracy, fewer calibrations, fewer calibration kits and reduced operating costs.
The DCM de-embedding technique provides the ability to accurately measure cables with a mix of different connector types (see Figure 5). This situation is often found in the aerospace industry where cables with different connector types are used. A common practice is to use error-prone adapters to facilitate the measurement, thereby increasing measurement uncertainty. Including the appropriate DCM-modeled adapter with the COAX-3000 system solves this problem.
A final significant benefit of the DCM calibration solution is elimination of the need for multiple calibration kits. After calibration, converting the test port to a different connector type is as simple as adding the appropriate DCM-modeled adapter. With a single calibration kit, the measurement port can be re-configured without re-calibrating the system or purchasing additional calibration kits. Total impact is a reduction in calibration time, fewer calibration kits and minimized calibration errors.
Fully Integrated Aerospace Production Line and Flight-line Test Solution
The aerospace version of the COAX-3000 is the HPCC-3000, as shown in Figure 5. With the introduction of the HPCC-3000, the aerospace industry now has a powerful solution for testing high performance coaxial cable (HPCC) assemblies on the flight-line, in the shipyard, or on the production line. The Model HPCC-3000 provides all required aerospace requirements including secure frequency operation, full data base functions, extensive cable matching capabilities, complete calibration management, and testing a wide range of cable assemblies with multiple connector configurations and supplies a comprehensive test report for each tested cable assembly. Because of the unique capabilities of the HPCC-3000 system, it has been chosen for use in the F-35 JSF Joint Strike Fighter program.
The COAX-3000 system is a complete test solution supporting the most demanding requirements for coaxial cables and cable assemblies used in the RF/microwave field. All RF measurement parameters are supported with full frequency range support. The COAX-3000 can act as a stand-alone software automation solution or can be combined with adapters and fixtures to facilitate cable testing. For cable assembly manufacturers, the COAX-3000 provides an automation solution easily useable by unskilled operators, both reducing testing costs and providing more accurate results and better data archiving. For the aerospace industry, the HPCC-3000 offers an automation solution for providing highly accurate HPCC testing, secure frequency testing and better data archiving. All DCM RF/microwave test solutions can be custom packaged to meet customer needs.
DCM Industries Inc.,
Union City, CA
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