Investigating IoT Wireless Signals

Figure 1: Many IoT devices accept
wireless antennas using U.FL
connectors

Many IoT devices use wireless methods to communicate with other devices or with host systems. Just as with DC power-rail signals, probing of RF signals should be done with as little noise and as non-invasively as possible and with the best possible signal fidelity. Effective probing opens the door to Wi-Fi and Bluetooth signal analysis with RF demodulation, vector signal analysis, and spectrum analysis.

IoT Digital Power Management and Power Integrity

Figure 1: The half-bridge output
current from each DC-DC phase
is known as the inductor current

An Internet of Things (IoT) device derives its power either from a 12-V DC supply or from a battery. In either case, power is fed to one or more power rails that operate at different voltages. These rails power the CPU and other functional blocks on the PC board. In this post, we'll take a look at how to examine an IoT's power supply for proper digital power management implementation and for power integrity.

Anatomy of an IoT Device

Figure 1: IoTs include SOCs, DDR,
DPM ICs, wireless, and MCUs

There's already more Internet of Things (IoT) devices deployed than there are humans on Earth. That gap will increase radically in coming years, and the explosion in IoT devices means a commensurate explosion in the need for debugging tools. So what's in an IoT device to debug, anyway?

Debugging the IoT

Figure 1: Chances are you're already
using the IoT in various ways

By now, we're all familiar with the phrase "Internet of Things" (IoT); some of you may be directly involved with that concept on some level as a designer/technologist. Here, we'll begin a series of posts on the IoT with some broad discussion of what it's all about, and then segue into how oscilloscopes and related hardware/software are among the best tools available for design and debug of IoT-related devices.

An Example of Three-Phase Power Measurements

Figure 1: Screen capture of a 10-s acquisition of AC input
and PWM output of a 480-V motor drive

To follow up on our last post on three-phase power calculations, and to wrap up this series of posts on the fundamentals of power, we'll walk through an example of a set of three-phase power measurements. We'll base our discussion on a single screen capture of measurements taken on a 480-V motor drive with 480-V AC input and 480-V maximum drive output. For this example, we used a Teledyne LeCroy Motor Drive Analyzer.

Three-Phase Power Calculations

Figure 1: Three-phase power calculations
entail summing of the individual
phases's power calculations

Until now, our discussions of power calculations have encompassed only single-phase systems with one voltage and one current. Now we'll turn to three-phase systems, which can be thought of as a collection of three single-phase systems. In general, three-phase power calculations are a simple summing of the individual phase power calculations and should be balanced across all three phases.

Power Calculations for Distorted Waveforms

Figure 1: The sum of many sine waves, of varying
amplitudes and frequencies, comprises the rough-
looking square wave shown in red

Our last post covered basic power calculations for pure sine waves, which are useful only up to a point in that pure sine waves are rather rare in the real world. Almost any real-world waveform carries some amount of distortion. Because distorted voltage and current waveforms comprise multiple frequencies, the relatively simple techniques used to measure power for pure, single-frequency sine waves no longer apply.