Comprehensive instrumentation approach solves challenging system-level tests

Today's electronic devices and products are developing at a faster pace than ever before, with the lifecycle from design to production shortened to as little as six months in many commercial applications. In addition, device content and topology are shifting from single to multi-function devices involving entire subsystems and systems, often as a single solution (such as devices like smartphones and iPhones).

Furthermore, direct software control and device configuration is commonplace for multi-carrier power amplifiers (MCPA) and software-defined radios (SDR). And devices like RFICs can only be operated and tested in mixed-signal environments, often in real time.

When all these factors are considered, the ideal design for testability and manufacturability (DFT&M) characteristics and requirements quickly emerge. These characteristics and requirements can be easily provided and met by "integrated" instruments. Unlike static rack-and-stack test systems, integrated instruments can be systematically coordinated with the device under test (DUT) quite simply.

What is comprehensive testing?

Traditional test system vendors embed various benchtop test instruments or dedicated instrument modules into a framework through appropriate interconnect cables, and then connect these instruments to the product under test with connectors. Then, they add software that calls the functions built into these instruments. For test system development, "stack-and-place" is a more common name for this approach. The traditional instruments currently used include: oscilloscopes, digital multimeters, spectrum analyzers, and frequency counters, which are either single stand-alone systems or as part of the entire test system.

Integrated instruments "integrate" the stimulus and measurement capabilities found in traditional instruments by combining software application programming interfaces (APIs) and test algorithms, hardware modules, and system-level calibration software based on core instrumentation functional building blocks. The concept of integrated instruments has its roots in the ubiquitous supporting technologies behind radar and EW transmitters and receivers, SDRs, mobile/handheld devices and phones, wireless infrastructure, devices and subsystems, and other communications systems designed and installed today.

The integrated architecture also enhances the ability to upgrade the test system and systematically handle obsolescence. When an upgrade is required or an obsolescence problem needs to be handled, only the functional blocks involved need to be added or replaced directly, rather than the entire set of instruments or the corresponding measurement and test applications. It reduces the cost of handling obsolete instruments and reduces the technical risks associated with the equipment update.

With the integrated system, an organization can generate a variety of signal types, including: digital, analog, RF and microwave. It is achieved using modular hardware, system software and modular measurement and application software. The integrated system architecture has the unique ability to explore hardware, measurement and application performance separately and as a whole. The hardware-independent software measurement library also avoids the risk of duplication of development as hardware performance evolves.

The integrated system solves multi-industry test problems. It is achieved by combining modular hardware and software components to generate a powerful new test instrument family, which has obvious advantages over traditional stand-alone single-measurement function stacked test instruments. With the integrated system architecture, it is possible to reduce/increase test time/throughput by 4~10 times respectively compared to traditional stacked solutions by utilizing multiple parallel paths.

The key advantages of the integrated test system include:

1. Reduced unit test cost;
2. Shortened test time and improved efficiency;
3. Reduced test equipment requirements and test configuration;
4. Faster measurements and more accurate results;
5. Simplified system-level calibration;
6. Reduced capital investment, maintenance and ownership costs;
7. Reduced upgrade and obsolescence issues;
8. Possessing a platform that meets the needs of next-generation measurement algorithm development;
9. A reuse model that is independent of the platform and system;
10. Extracting test applications and measurement software from system hardware and software configuration.

The integrated system reduces upgrade and product obsolescence issues. Hardware, system software, applications, and measurement architecture modules can be replaced completely or individually as needed. This reduces upgrade costs and system integration risks, both of which can negatively impact test application deployments.

The integrated system solves the recalibration problem that arises when calibration and functional test cycles are programmed directly into the system functional blocks. It allows the calibration routine to run continuously in real time. Therefore, it eliminates the pre-planned downtime that is often required to recalibrate a given system. In addition, the continuous embedded calibration capability also enhances the overall integrity of the test system.

The integrated architecture also enhances the ability to upgrade test systems and handle system obsolescence. When upgrades or obsolescence occur, only the directly affected modules need to be added or replaced, rather than the entire instrument group or the corresponding measurement and test applications. In addition to reducing the technical risks associated with this process, it also reduces the cost of handling obsolete instruments.

The concept of integrated instrumentation treats hardware in the same way that object-oriented programming treats software "modules". Therefore, object-oriented software matches the integrated instrumentation approach very well. Advanced integrated instrumentation implementations utilize software targets that correspond one-to-one to functional hardware modules. In addition, they implement stimulus and measurement algorithms as software targets.

Containing all the information needed to function a hardware module allows intelligent software to easily combine modules in different configurations and determine the final stimulus or measurement capability. In short, if you know the transfer function of each module, you can combine them to generate complex stimulus or measurement. Because the module is treated as a target, one or more calibration coefficients can also be located within the target. Therefore, modules can be combined in many different ways while maintaining a continuous flow of high-quality and sensitive system-level calibration to the unit under test.

Further benefits of this goal-oriented approach include integrated diagnostics and fault warning capabilities for the test system and DUT. Integrated diagnostics are difficult to achieve for traditional test systems that use sequential programming techniques. With a comprehensive goal-oriented system approach, intelligent software can easily monitor the operating status and conditions of hardware and software targets to provide real-time diagnostics. Adding trending to the system can also provide fault warning capabilities.

The integrated system environment is independent of the choice of hardware platform and interface. Because the interfaces between hardware and software modules are also treated as plug-in targets, solution providers can combine PXI, LXI, PCI, PCI-X, VXI, GPIB, Ethernet, USB or other communication buses including switched fiber architectures.

Hardware configuration is abstracted from software components and modules, thus having the ability to be reconfigured at will. The integrated system approach provides an extremely powerful system architecture that makes reuse and expansion possible.

The path to an integrated test system

An ideal DFT&M solution provides all the required data and control interfaces, as well as the simulation, computational, and emulation features (i.e., the test environment) required for the DUT to function and communicate while being tested, just as if it were embedded in the actual system environment (Figure 1).

As DUT integration and complexity increase, the operating behavior, communication mode, functional performance, and the type of data processed by the test environment (TE) must be able to adapt to requirements through software reconfiguration and dynamic reallocation of test resources.

Considering the simultaneous occurrence of multiple internal and external I/O (interface) processes within the DUT, the TE must be able to perform multiple precisely controlled and carefully synchronized complex measurements. This often occurs in real-time conditions and in the same module as the sampling and processing of data, without losing the continuity of the entire stimulus, response and data group flow processing.

This simultaneous and precisely synchronized process ensures that the cause/effect relationship of the results and the behavior of the controlled and analyzed parameters are maintained consistently. Synchronization also provides DFT&M engineers with accurate, low uncertainty and highly correlated data/information.

Time-to-market pressure continues to squeeze the DUT development cycle, and the test system should provide full test environment capabilities for each stage of DUT feasibility assessment, development, integration, verification, production and maintenance. It is not practical to prepare multiple/independent test equipment and test teams for each stage of the modern DUT life cycle from both economic and available test resources (i.e., equipment and manpower accumulation). Therefore, it is necessary to design a test environment with testability and manufacturability, which includes comprehensive solutions and resources that can dynamically, seamlessly and cost-effectively adapt to different situations at each stage of the DUT (Figure 2).

The increase in DUT integration and complexity coupled with the shortening of development cycles makes it difficult for traditional test instruments to provide highly professional, useful and complete modern test functions, routines and corresponding results (for example, the types of buttons and data displays on traditional instruments). The replacement test solution will include a software-configurable measurement platform (Figure 3).

This platform utilizes a basic measurement library that DFT&M engineers can modify, integrate, sequence and supplement with simple scripting, graphics and other human-machine interface technologies to best match the latest test requirements of new DUTs. Following the above logic, it is most likely that an increasing level of functionality and control/data I/O interaction will occur between DUTs and TEs. This will require a more common and integrated roadmap and a higher level of cooperation between DUT developers and TE suppliers.

It is important to realize that even though we don’t usually state it publicly, DUT developers have been embedding IP Test Cores (IPTCs) within their devices for many years. These IPTCs can be very simple in nature when supporting low-level built-in test (BIT) functionality. They can also be quite complex when supporting boundary test functionality that is externally stimulated and controlled, where multiple vectors and combinations can be used to verify the full functionality of the DUT by limiting interactions to the I/O level.

These situations become even more prevalent in software-defined devices where the test interface is primarily agreed upon through intelligent software interaction between the DUT and the TE. Here, the DUT built-in test capabilities can only be fully utilized if the TE can "look out" and effectively communicate with the DUT/TE interface. Once again, it means close cooperation between the DUT developer and the TE supplier, with harmonious roadmaps and development activities.

Based on these considerations, one could argue that in this rapidly changing environment, traditional test solutions based on multiple, individually tailored instruments for a particular application will not be able to keep up with the demands of design, test, and maintenance, nor will they be able to adapt to the complexity of the test ensemble. In fact, engineering roles are rapidly converging.

There is an urgent need for a DFT&M solution that can quickly adapt to new device performance requirements. The new test system will also allow customized measurements that are not strictly constrained by the specific functions and human-machine interface characteristics of traditional test instruments.

In this case, a truly integrated approach allows DFT&M engineers to work seamlessly from product advent to maintenance. This highly integrated, modular, software-driven, integrated architecture also supports proactive and cost-effective management of obsolescence issues by limiting the impact of obsolescence issues to a single integrated module rather than the entire test system.

As integrated test solutions gain acceptance and rapidly expand their coverage, it is imperative that DFT&M engineers select truly integrated systems with hybrid integration capabilities to encompass a variety of standards.

In general, companies that provide proven integrated test system solutions also develop and integrate system components. These companies have the experience and expertise to integrate all system components under a fully calibrated, synchronized, and standard-traceable test. Only under these conditions will a truly integrated (i.e., measurement-based) system perform tasks accurately, reliably, and consistently, providing a truly superior DFT&M solution. A fully integrated, measurement-based, highly integrated, software-configurable, and adaptive test environment is the way to the future.