Communication devices need to undergo considerable testing to ensure interoperability and compliance. Some test instruments are designed to be tested to specific standards (such as WiMAX, Bluetooth, CDMA, GSM, and LTE), which greatly accelerate the development and production of communications equipment manufacturers. PXI can play an important role in this type of standards-based testing, but the approach to technology adoption may be surprising.
The standards that wireless communication devices must meet are both complex and evolving. Over the past decade, technological advances have led to major changes in modulation methods, operating frequencies and standards related to information protocols, and some advances have led to the introduction of new standards. Test equipment used by communication equipment developers and manufacturers must be flexible enough to accommodate such changes.
At the same time, developers and manufacturers can get a lot of benefits from test equipment built specifically for specific standards of testing. According to TIm Carey, product manager for automated test systems at Aeroflex, although the tests for various wireless standards may require the same basic RF measurements, the interpretation of the test data may vary significantly. Carey said: "The definition of output power is different for each standard. The characteristics of modulation quality are different between different standards, and some standards have multiple modulation methods, depending on the quality of service provided. â€
Of course, the design choices made by the developer may result in standards-based testing requirements that vary internally and may vary from product to product. For example, a CDMA dedicated fixed-function tester may require minor changes to handle chips from two different manufacturers. Carey said: "The method depends on the choice of the chipset vendor and also on the relevant standards. The communication (setting and control signaling) for configuring each device is related to the specific chip."
The above changes put a heavy burden on test engineers who use common equipment at work, and they need to develop complex test procedures to measure compliance. The specially constructed communication test equipment provides pre-configured settings and data analysis for relevant standards, thus alleviating this burden. However, the rapid evolution of wireless communications has made flexibility a key requirement. This is where PXI's configurability shines.
Flexible test instrumentDavid Hall, RF Product Marketing Manager at NaTIonal Instruments, said: "With the promotion of industry standards and individual standards, engineers need to be able to customize their test equipment as quickly as possible. Bench-top instruments require vendors to participate in updates even when there are subtle changes in standard tests. With PXI, users can take advantage of the source code and make changes as needed."
Hall also pointed out that PXI-based devices are very easy to improve performance. “With PXI, data processing can be done on Windows CPU modules, and the module can be replaced as technology advances. In traditional chassis, processing is built-in.†As a result, PXI-based devices can easily keep up with standard changes.
The flexibility of PXI also makes it easy to adapt to emerging standards changes. Hall said: "Many wireless standards are changes to a basic solution. For example, ZigBee is a superset of IEEE 802.15 (wireless personal area network), and other similar changes to the standard have emerged."
Using PXI to test these new changes becomes a simple task—reprogramming existing hardware. Similarly, PXI supports testing products that must meet several criteria, such as netbooks, which include both WiFi and cellular communication capabilities in their designs.
For designers, PXI enables them to take advantage of the information hidden in traditional benchtop instruments, allowing them to develop more tests beyond the standard. Hall said: "Tools such as LabView allow you to do things that can't be done with traditional instruments. For example, you can use I/Q data, which is hard to reach in desktop instruments."
Traditional pre-configured instruments do offer some advantages. One of them is the highest RF performance. Hall said: "The traditional instrument design can reach 40GHz to 60GHz. The current PXI technology is about 26.5GHz." Traditional instruments can also provide battery-powered portability, which is unmatched by PXI. He said: "Handheld spectrum analyzers are sometimes very useful."
PXI system shortageBut overall, PXI offers more compelling benefits than traditional instruments in testing for evolving standards. However, there appears to be a shortage of PXI products for standard testing. NaTIonal Instruments offers several RF test benchmark platforms, including a WLAN toolkit and a test platform for wireless sensor networks. Aeroflex has created the 3000 Series Communications Test Sets, which handle a variety of standards including Bluetooth, WiMAX, CDMA, GSM. However, most other PXI vendors only provide components and do not provide complete packages.
One of the reasons for this shortage may be the inertia of test engineers who resist the transition from benchtop instruments to modular instruments, thus limiting the market. Hall said: "There is a generation gap between test engineers, making many potential users feel uncomfortable when using modular methods. PXI is different from the methods they are familiar with."
Hall takes spectrum analysis as an example. He pointed out that the traditional RF spectrum analyzer is equipped with an analog display dedicated video bandwidth filter, but as the analysis moves from analog sweep to digital sampling, PXI and other digital systems have stopped providing this setting. Hall said: "It only affects the display and does not affect the data. But it makes PXI look different, so we need to educate users about this kind of difference."
Another reason for the shortage is the hesitation of the manufacturers. I wonder if it will take the necessary effort to develop software to handle complex communication protocols.
Don't consider that you don't always need protocol testing capabilities. Aeroflex's Carey said: "The protocol processing constitutes the most important part of the test development work. These tests may take many years to develop and maintain."
Moreover, it may not be necessary to equip the instrument with standards-based testing capabilities. Carey said: "Pre-compliance testing in the design phase may require protocol testing capabilities, but manufacturing may not be required. If customers only perform parametric testing on the relevant standard limits to evaluate the manufacturing quality of the boards, then they are unlikely to be willing to pay. Protocol test development costs."
These factors seem to limit the products that PXI vendors offer for the standard test market, but this does not mean that PXI itself has been limited. Quite the contrary, PXI is finding its way into the standard test areas that are inherently hidden within the product that test equipment OEMs are offering to the market. For example, Aeroflex has developed the 7100 Series Communication Test Set for use by LTE cellular handset developers. The core of the 7100 series is PXI, but this is not reflected in advertising. Carey said: "We just use it as a digital radio test group to sell."
Other test equipment manufacturers also use it as a basis without mentioning PXI. The SP6010 TD-SCDMA terminal comprehensive test basic system of Beijing Xinghe Highlight Communication Software Co., Ltd. is another example of a desktop instrument that hides the PXI system. Carey said: PXI is also quietly adopted by manufacturers of tested equipment, such as OEMs in Korea, first-line manufacturers in the United States, and so on.
PXI offers these manufacturers the benefits of flexibility, but it is the hidden benefit of PXI being used in benchtop instrument design. One of these benefits is faster time to market.
Carey said: "For many OEMs, they need faster time to market than design flexibility. PXI enables these companies to make COTS choices and customize them without having to develop the technology themselves. About PXI One thing makes it easy to integrate with anything else."
PXI also enables test equipment manufacturers to leverage their communications protocol expertise without the need for RF technology expertise. Carey said: "If the company can focus on its core capabilities and make full use of COTS products to fill the gap, then this is an attractive thing." He said that typically, companies will develop a customization The real-time baseband processing card runs the respective protocol test software and connects it to PXI to complete the RF field.
Therefore, the role that PXI found for itself in standards-based testing is not as a configurable instrument, but as a hidden basis. This role is not achieved through the flexibility of widespread publicity, but through its incomprehensible capabilities – accelerating product development and complementing OEM core expertise with off-the-shelf solutions for non-core technologies. Some manufacturers will adopt PXI when developing dedicated standard test equipment, and they will still benefit from the flexibility of PXI. Carey said: "These designs are only dedicated for a while, and people can always retrofit them later."
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