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LitePoint Testing Solutions and UWB Modulation Techniques

By Adam Smith

October 20, 2020

UWB modulation Techniques

In my previous blog posts, I explored the history of Ultra Wideband (UWB) and the basics of how the technology works, as well as which applications UWB is best suited. Today, I’ll walk you through the testing solutions LitePoint has available for UWB and UWB modulation techniques. I will conclude with a brief summary of how the company is working with the FiRa Consortium to accelerate the adoption of UWB.

First, a little background on LitePoint. LitePoint is a member of the Teradyne family. Teradyne has test solutions for semiconductors from the time they are born on the wafer until the time they ship and arrive to the end customer. LitePoint fits into the Teradyne organization as the wireless test systems arm.

LitePoint is focused more on the printed circuit board level and final product level of calibration and testing of devices, the last manufacturing stage before the user gets to experience and interact with the products. The applications LitePoint typically deals with are grouped in three different areas. First, mobile consumer devices, whether we’re talking about smartphones, tablets, laptops, gaming devices, really any consumer device that has a wireless interface. Next, wireless infrastructure, meaning access points, small cells, gateways, CPE devices. This group involves things that take a broadband signal and converts it to a local area network data packet. And lastly, internet of things (IoT) products, both consumer and industrial.

If a product has an air interface on it, LitePoint is testing it in some way today.

LitePoint IQgig-UWB Validates and Calibrates UWB Devices

At LitePoint, we’re focused on calibration and making sure that the first device off the line works very much like the millionth device off the line. Our IQgig-UWB is a fully integrated test solution for calibrating and validating UWB devices, both on the transmitter side and on the receiver side. The test solution covers a frequency range from 5 GHz to 19 GHz, with a 2 GHz single-shot bandwidth.

So, whether the UWB signal is transmitting at 500 MHz or some future UWB signal transmits at 1 GHz, or maybe 1.2 GHz or 1.3 GHz, this instrument has the forward-looking capability to address that.

What’s unique about the IQgig-UWB is that it can make some of the measurements that are specific to UWB. First is measuring distance to determine time-of-flight (ToF). The test system has a precision trigger and response mechanism, where the instrument can receive a polling request and deliver a response in less than 20 microseconds, with picosecond level jitter. So again, the timing of UWB is the key parameter. It’s not necessarily the demodulation accuracy. We’re really concerned about timing.

UWB is transmitted in very low signal power. And so, the sensitivity of the receivers is very low. The instrument has an ability to generate signals very accurately below -100 dBm. So it’s very low power, very accurate timing. And that’s really what we are mostly concerned about in UWB testing.

This is a screenshot of the graphical user interface in the product. Here you can see some of the measurements that are happening on the upper right portion of the screen.

The upper left is the time domain. You can see these are a series of short pulses, and you can see that the timescale is on microseconds. The LitePoint instrument is looking at bursts of pulses that are significantly less than a microsecond. And the types of measurements that the test system is looking at are mostly in frequency and in timing. There is chip clocking error, frequency error and then power measurements.

In the bottom left drawing is what is called the eye diagram, which is really trying to overlay the reference pulse’s jitter. If there’s a lot of jitter, you’ll see that as being a very fuzzy signal. And if there’s a little jitter, which is the key measurement for the timing accuracy required for UWB, you’ll see those almost lay right on top of each other.

And lastly is a power mask in the bottom right.

This is a comprehensive list of the type of measurements the IQgig-UWB is making. One to note is symbol modulation accuracy. In Wi-Fi or 5G or some other OFDM type of technology, the key spec in those technologies is error vector magnitude (EVM). In UWB there’s no direct correlation to how accurately the signal is modulated. But what is compared in UWB is the reference signal versus the measured signal in a correlation function. A correlation of 100 percent would be a perfectly transmitted signal. And then as the signal is distorted, the correlation gets worse. And so that 100 percent goes down. With a correlation factor of 90 percent, there’s some distortion in that signal. As engineers characterize their devices, they can use this capability to put some sort of qualitative metric around modulation accuracy. But again, that’s not really the key spec that is part of UWB. UWB is much more focused on frequency errors, chip clock errors and the jitter in the pulses, as well as things like time-of-flight (ToF) and angle of arrival (AoA).

IQ5631 Power and Delay Control Module

In order to provide some of the advanced capabilities for UWB from a calibration measurement point of view, LitePoint offers an additional accessory product called the IQ5631 Power and Delay Control Module (PDCM). It enables very low RX sensitivity measurements. The industry is seeing a variety of reference designs developed by chipset vendors for their customers. These come with support for a single antenna device as well as multi-antenna devices. This product enables the ability to test multi antenna devices. Additionally, this product has an integrated ability to control the delay between the different signals, so it allows the ability to do angle of arrival (AoA) testing.

Total Solutions for Design Validation and Production

LitePoint is helping to make the complexity of testing UWB devices simple through automated test solutions. IQfact+ delivers pre-configured software that is designed for leading UWB chip designs. LitePoint also has a data visualization tool called IQramp. With IQramp, the IQfact+ collects data and then the user can drag and drop those files into IQramp to do data visualization as part of the characterization of the product. When the user is dialed in and ready to go, they can move the IQfact+ into manufacturing, enabling a seamless transition from product development to production.

Work with FiRa Consortium

To close out this blog series, I wanted to quickly highlight the FiRa Consortium. The FiRa Consortium was developed in 2019 as a member-driven organization focused on the secure fine-ranging and positioning capabilities of UWB technologies. LitePoint was the first test vendor to join the consortium. LitePoint joined the FiRa Consortium to help create and roll out a certification program for UWB devices. This upcoming certification program will ensure that UWB devices are interoperable and can harmonize the way testing will be done for different UWB use cases.

I hope you’ve enjoyed this UWB blog series and I invite you to visit the full replay of my webinar on this topic. Look for more blog posts on UWB and other topics from myself and the LitePoint team in the weeks to come.

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