PCB News - Five challenges for IoT testing

In the next few years, advancements in AI, 5G, IoT, and industrial automation (IIoT) will accelerate the pace of industry change and innovation. Various IoT sensors across industries will be used for automatic data transmission and remote device control. In the era of the Internet of Everything, connectivity will become commonplace. By 2020, Gartner predicts that more than 20 billion IoT devices will be put into use.
2019 is a new starting point for 5G commercial use. Combined with IoT devices, the increased bandwidth, faster speed and lower latency of 5G will bring applications that were previously considered impossible. The Internet of Things will continue to penetrate into multiple industries, such as PCB manufacturing, transportation, medical, consumer, etc.
As the pace of innovation accelerates, engineers, designers, suppliers and manufacturers will face faster pressure to market. For IoT devices, each generation of products needs to be smaller, more powerful, easier to configure, and use less power than previous designs. Since many IoT devices are battery-powered, energy saving is essential. Low-power components must be used, and these components must be powered off when not in use. In order to optimize battery life, components must be tested under realistic scenarios and conditions to ensure that the correct components are selected to maximize the life of IoT devices.

IoT Challenge 1-Power Management
Since IoT devices are usually deployed remotely or in a mobile environment, most devices use batteries as their main power source. Understanding the power consumption curve of a device is the key to ensuring maximum reliability and performance during the life of the device.

In order to fully characterize the power consumption of IoT devices, it must be measured under all operating conditions commonly encountered. Since IoT devices are designed to minimize power consumption, they may only be active for a short period of time, and most of their lifespan is in "sleep" mode.

To accurately measure the power consumption curve of the device in all operating modes, you may encounter the challenge of how to use common current measurement techniques (such as shunts, digital multimeters, DMMs, or current probes). In the sleep mode, the current may be in the range of'nA' or'uA'; in the active mode, for example, when transmitting data, the current may suddenly change to the range of "mA" to "A". In addition, these large peaks in current demand usually occur within microseconds, and power conversion may be more challenging for some test instruments.

Although they can be very accurate when used in the right environment, due to the large dynamic range involved (multiple shunts may be required), using current shunts for this type of measurement may be problematic. Even if multiple shunts are used, it may be necessary to test the active mode and the sleep mode separately, which makes it difficult to obtain the true current loss. In addition, due to the inherent voltage drop, if an excessively large value is selected to maximize the dynamic range of the measurement, the shunt itself has the risk of impacting the test equipment.

IoT Challenge 2-Signal and Power Integrity

Mixed-signal integrated circuits are often used in the design of IoT devices, including sensors/MEMS, analog and digital signals that work with lower power consumption on the same integrated circuit, and they are very sensitive to crosstalk. Low-power distribution networks usually have very small operating tolerances, which increases the chance of ripple and noise interference on the power rail, which may adversely affect clocks and digital data. Many IoT devices require dense high-speed signal channels in a small physical structure, which increases the risk of crosstalk and coupling.

Use good signal integrity design principles (if possible, use point-to-point signal routing topology), control the trace impedance of the entire PDN and interconnection, keep the return path length short and maintain sufficient space between adjacent traces Reducing coupling will help alleviate signal integrity issues. Although adhering to good design principles such as this is essential to achieve a reliable design, it is also essential to have the ability to fully characterize the electrical performance of the structure that carries the signal throughout the device.

Vector network analyzer (VNA) is one of the most commonly used tools to characterize the electrical performance of any interconnection or transmission line. Important characteristics that affect signal integrity, such as insertion loss, attenuation, reflection, crosstalk, delay, and differential-to-common-mode conversion, can all be evaluated with a VNA that is properly configured for the application. In addition, some VNAs have the ability (usually through a software option) to perform a time domain conversion of the s-parameter measurement, which will display the impulse response of the channel.

Regarding power integrity, the recently developed power rail probe facilitates ultra-low noise measurements on the power rail and is used in conjunction with an oscilloscope. Depending on the manufacturer, the characteristics of these probes generally include:

Up to 60V offset to ensure that the power rail is completely shifted to the oscilloscope display.
The dynamic range is up to 1V.
Gigahertz operates bandwidth to ensure that high frequency noise will not be detected.
The 1:1 attenuation ratio can reduce the noise of the measurement system.
50kΩ impedance to reduce the load.
Choosing the right tools to detect signal and power integrity issues is very important for fully identifying and solving the causes of poor performance and verifying the true performance of the design. VNAs, power rail probes, and oscilloscopes are just some of the tools that help achieve this goal.

IoT Challenge 3-Wireless Standard Compatibility
Whether you are developing a device for short-distance connection via Zigbee or Wi-Fi, or a long-distance connection device via LoRa or LTE-M, the wireless protocol you choose will determine how your device connects and share data with the world The way.

Ensuring interoperability by following the specifications of wireless standards is the key to achieving maximum market influence. As with EMI/EMC, testing early in the design cycle can help you identify issues that may cause delays and increase the cost of developing the design before the qualification phase.

Vector signal generators that can generate standard-compliant signals and spectrum/signal analyzers that can demodulate these signals are ideal tools for evaluating device performance based on the selected wireless standard.

IoT Challenge 4-EMI/EMC and Coexistence Testing
We can define EMC as a measure of whether a product performs as expected, and it will not hinder the ability of other products to perform as expected in a shared operating environment. EMI can also be defined as any electromagnetic energy that prevents the device from performing as expected. As the number of wireless communication devices continues to grow exponentially, electromagnetic noise in the operating environment increases accordingly, and the risk of performance degradation due to interference also increases.

Although the use of pre-certified RF modules helps to reduce the possibility of completed equipment failing the regulatory EMC compliance test, it does not guarantee that the final product meets the relevant requirements.

Using good EMI engineering countermeasures from the beginning of the design and evaluating the actual electromagnetic compatibility performance of the equipment before the conformance test phase (pre-compliance test) helps avoid costly redesigns and delays that affect the time to market.

In the IoT device market, the medical device market has grown rapidly in recent years. Devices capable of transmitting real-time vital signs, whether fixed, wearable or implantable, are becoming more and more common in hospitals and home care environments. Like other IoT devices, medical devices may also become sources and receivers of interference in the operating environment. However, given their use in providing medical services, if they fail to operate as expected, they may cause life-threatening consequences.

Due to the key functions of these wireless devices, coexistence testing has become an important part of the IoT medical device design process. IEEE/ANSI C63.27 is one of these standards, which outlines test procedures and methods to verify the ability of wireless devices to coexist with other wireless services operating in the same RF frequency band. AAMI TIR69 is another standard that provides guidance for medical devices and how to evaluate wireless technology based on potential hazards in the operating environment (including external hazards that the manufacturer may not control).

Like EMC testing, the finished product may be sent to a conformance testing agency for final testing. However, preliminary coexistence testing during the design process can be used to determine the tolerance of the device to other radio signals and ensure that acceptable levels of operation can be achieved. If performance issues are discovered early, mitigation techniques can be used and performance can be reassessed before the final design is established.

The spectrum/signal analyzer is the key test equipment for EMC pre-compliance testing and coexistence testing. Although complete EMC testing requires a fully compatible EMI receiver, many modern analyzers can be equipped with software packages to help facilitate pre-compatibility testing of radiated and conducted emissions, including bandwidth, detectors, and CISPR and MIL-STD-compliant bandwidths. Frequency band presets, as well as the limit line of the internationally recognized EMC standard limits, and the option to create user-selectable limits.

The coexistence test uses a real-time spectrum analyzer and uses a high-speed analog-to-digital converter (ADC) to continuously sample the spectrum, and then uses a real-time fast Fourier transform (FFT) to display a spectrum view of the RF environment where the test equipment is located. The vector signal generator is also used to generate the types of signals encountered in the expected analog operating environment, such as WiFi and Bluetooth.

IoT Challenge 5-RF performance of wireless connections
Although some IoT devices will use wired communications, most will rely on some form of wireless technology to gain access to the network. When deciding how to best implement wireless communication, designers of IoT devices face many decisions. The most important of these is to determine which wireless communication technology and protocol to use (WiMax, Wi-Fi, Zigbee, BLE, LoRa, Z-Wave and NB-IoT, etc.)-and whether to use prefabricated RF wireless modules or PCB internal designs.

No matter how to solve these design problems, the performance of RF communication must be tested under real conditions using equipment suitable for the task. Some common tests include:

Spectrum analyzer/signal analyzer is usually the tool of choice for transmitter measurement, while signal generator is usually used to generate the signal measured by receiver, and network analyzer is usually used for antenna measurement.

Many modern signal generators and signal analyzers provide software application support for most common wireless communication standards implemented in IoT devices. It can generate standards-based waveforms, and can use measurement applications running on the test equipment itself or on a PC with remote control to analyze test signals. If your wireless connection uses a custom design, there are some applications that may help you.

in conclusion
With the development of new technologies and the evolution of testing standards, innovations in the Internet of Things, cloud robotics and automation continue to develop, and the demand for testing and verification will also increase, especially the existing ones that need to be faced in order to support power management. And future challenges. All these new technologies require power and verification. Managing the power of IoT devices is a challenging task, because even in the most challenging environments, these devices must always be powered on and run at full capacity.