2009

The traditional engineering re sponse to testing a new wireless standard often involves selecting a box instrument with the closest specifications. For automated test systems with multiple test requirements, this approach usually results in a different box for each measurement requirement in the system. When the test requirements are uniform and non-changing, this method may be sufficient, but it becomes cumbersome, slow, and ultimately more expensive for testing today’s complex radio frequency (RF) devices, which often use multiple wireless standards. A software-defined approach is ideal for automating RF verification, validation, and production tests, while traditional RF box instruments continue to play an important role on the design bench.

Inside the Instrument

Figure 1. Comparison of EVM measurement times of competitive instruments.
Today’s engineers must think beyond the box for their RF test needs. However, to think beyond the box, they first have to know what is inside a typical RF box instrument. Inside each approximately 38,000 cubic centimeters of sheet metal and plastic enclosure is a vendor-defined world of components that constitute an RF box instrument: typically there is a power supply, processor, PC motherboard or backplane, embedded operating system, measurement libraries, and a software display. The traditional appeal of a box instrument is the combination of these matched components applied to a specific set of measurement requirements.

This approach worked when testing RF devices with common test requirements. In recent years, however, the efficiency of a box instrument for automated RF testing has significantly diminished amidst the constant changes in features in wireless devices. The production volume of wireless devices is also exceeding the typical test throughput of traditional RF box instruments due to the slower processors and data buses that are often generations older than current PC technology. A clear understanding of the traditional RF instrument makeup and the challenges of working with fixedmeasurement functionality and suboptimal I/O processing is helping engineers think beyond the box for their automated RF measurement needs.

Software-Defined Approach

The transition to software-defined instrumentation for all types of automated measurement systems, including RF, is growing rapidly with an expected deployment of 100,000 PXI-based systems by the end of 2009, including more than 600,000 software-defined instrument modules. The open, userdefined software and modular, PCbased hardware are ideal for automated RF test applications because they provide the highest-performance processors and data buses, flexible peripheral I/O, compact modular design, smart power distribution and monitoring, and precise timing and synchronization throughout the system.

In other words, the software-defined approach to automated RF test uses similar types of components as a traditional RF box instrument, but applies them in a modular, user-defined architecture. This provides engineers with the highest-performance components, user-programmable I/O and analysis, and a compact form factor with proven reliability in the most demanding RF test environments. The end reward for engineers thinking beyond the box is an RF test solution that is faster, more flexible, and equally accurate – all at a fraction of the cost of stacking traditional RF boxes within a system. To further understand the benefits of software- defined instrumentation for RF, take a look at the following examples that describe how the speed, flexibility, and accuracy of this approach yields significant improvements in meeting today’s RF test needs.

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