In today’s multitrillion-dollar IoT market, establishing a test-oriented environment for RF is a critical investment in the success of a product
Without a doubt, the “internet of things” is going to be huge. A 2015 McKinsey Global Institute report states the economic impact for IoT devices could reach between $3.9 trillion and $11.1 trillion by 2025. The report cites industrial and commercial applications as the biggest users of IoT technologies, followed by cities (improving public safety, outdoor streetlight control, etc.), and personal use (health improvement and monitoring, managing illnesses, etc.). As the market further materializes, what will be the key factors to ensure device success when millions of products enter the marketplace?
Of course, wireless is the key enabling technology for IoT devices. Wireless connectivity adds value for which customers will pay a premium, so it is critical that IoT vendors deliver great wireless functionality to fulfill the promise of added value within their IoT products. In addition, because product lifecycles are shorter and IoT concepts are copied more easily, it is essential to get an IoT product design correct from the start.
Important parameters for wireless connectivity within IoT products
The four parameters most important for an IoT device are:
Range
Range is the distance from the IoT device to a connected wireless router, hand-held device or computer. IoT devices must reliably connect when placed within the specified range, which is of course, dependent on the wireless technology that the device uses. Devices that use Bluetooth technology, for example, will have shorter ranges than those that use Wi-Fi technology.
Battery life
Not all IoT devices are battery powered – some are plugged in – but for those that are battery life is critical. To ensure IoT devices have sufficient battery life it’s necessary to measure the power consumption of the device in realistic scenarios.
Response time
Consumers hate devices that are slow. In an IoT-led world fast response times are crucial as an increasing number of products compete for limited spectrum. Wireless throughput defines the maximum data rate that can be achieved in a wireless connection. Changeover time defines how quickly a wireless channel can be handed off from one wireless user to another. Both of these parameters affect the real-world application response time experienced by the user.
Interoperability
As the wireless spectrum gets more crowded, interoperability in an environment with many wireless devices is critical. Efficient use of wireless capacity is key to enabling more and more devices to share the available radio frequency spectrum.
What is design verification testing?
To find design problems, rigorous design verification testing is required. Design verification testing differs quite a lot from production tests, which are designed to detect manufacturing defects rather than design flaws.
A good production test provides comprehensive test coverage to ensure all electronics are manufactured correctly and the device is assembled properly. The production test often performs system-level calibration and a minimum of high-level functional verification tests. One of the biggest misconceptions in the wireless world is that production testing alone ensures a quality product, but this is only true if you’re starting with a quality design.
Due to the ever-increasing complexity of wireless hardware and software, this often is not the case. Test time restrictions in mass production do not allow all functionality to be comprehensively tested over the range of real-world operating conditions. That’s the job of the design verification testing, which verifies that the design is robust and the product will work as expected when it gets into consumers’ hands. Getting the design correct first will ensure that the mass production test phase can be focused on finding manufacturing defects.
With so many things that can go wrong, it is critical for companies to incorporate DVT into their overall product development plan before releasing a device to production. It is during the DVT phase that errors, bugs and incompatibilities can be identified and corrected. It is especially important when relying on a chipset manufacturer’s reference design. The key is to make sure the reference design works reliably within the finished IoT product. DVT ensures the product meets all of the design specifications before it costs money and time to fix. Design verification testing is worth the investment as it ensures the product will work reliably in the real world.
Creating a modern DVT plan
Comprehensive DVT will find problems within a design early in the product lifecycle and allow time to make design changes before the exposure gets really expensive. An effective design verification testing program will actually help bring the product to market faster, with fewer hiccups, and yield greater customer satisfaction and higher profitability.
Here is an example of comprehensive DVT of a wireless radio. To thoroughly vet a product design, DVT should be performed as the following operating conditions and parameters are swept:
• RF power setpoint;
• RF frequency;
• RF duty cycle;
• RF pulse width;
• Modulation order (bit rate);
• Modulation bandwidth;
• Standard (e.g. 802.11a/b/g/n/ac);
• DC supply voltage(s);
• Operating temperature;
• Transmitter loading (VSWR); and
• Chipset register settings (e.g. operating mode).
As the above operating conditions are swept, you should make transmit quality measurements, such as:
• RF power output;
• Error vector magnitude;
• Adjacent channel leakage ratio or spectral mask;
• RF frequency error;
• DC current draw;
• DC to RF efficiency; and
• Harmonic and spurious emissions.
And, of course, you’ll want to make some receiver measurements, such as:
• Minimum input level sensitivity;
• Maximum input level; and
• De-sense levels, or adjacent channel rejection.
Making choices: test for success
Companies making wireless devices such as phones, radios and access points have sufficient volume and revenue to justify large RF engineering teams to design and validate RF-enabled products. With wireless technologies becoming pervasive in millions of mid- to-small-volume IoT products, the RF test burden may often shift to multidiscipline engineers with less RF experience. This requires test solutions be easier to configure and use as multidisciplined engineers step in as the de facto test engineer. The test equipment must be flexible and sophisticated to support a variety of new and traditional technologies and standards, such as Wi-Fi, ZigBee, LTE, connectivity and emerging chipsets.
Look for test equipment with many standard test operations, test sequences and measurements. In addition to the hardware test capabilities, check out the software tools that come with the test equipment. A good test hardware/software package should be easy to use, so that design verification testing can be started immediately.
Chris Ziomek is the VP and GM of LitePoint Design Test Solutions. This division is focused on wireless design verification and RFIC testing, helping customers bring their wireless electronic products to the market. Ziomek has 30 years of experience in the test-equipment industry as an instrument designer, engineering manager, entrepreneur and business unit manager.
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