December 2015
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Electric Vehicle Test Solutions The Problem of Short Battery Life
Bridging the Gap Crucial Test Probes from Picotest Bolster Innovations in Power Integrity
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CONTENTS
Modern Test & Measure
EDITORIAL STAFF Content Editor Alex Maddalena amaddalena@aspencore.com Digital Content Manager Heather Hamilton hhamilton@aspencore.com Tel | 208-639-6485 Global Creative Director Nicolas Perner nperner@aspencore.com Graphic Designer Carol Smiley csmiley@aspencore.com Audience Development Claire Hellar chellar@aspencore.com
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TECH SERIES Determining an RF Burst’s Envelope PRODUCT WATCH Electric Vehicle Test Solutions from Chroma TECH REPORT IoT Wireless Sensors and the Problem of Short Battery Life INDUSTRY INTERVIEW Bridging the Gap Interview with Steve Sandler of Picotest
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Victor Alejandro Gao General Manager Executive Publisher Cody Miller Global Media Director Group Publisher
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Modern Test & Measure
Determining
an RF Burst’s Envelope By David Maliniak, Teledyne LeCroy
There aren’t many wireless environments more complex than that of the electronic-warfare arena. Spread-spectrum clocking, frequency hopping, jamming, you name it: It’s an RF jungle out there, and signals intended for electronic-warfare applications demand precision instrumentation and skilled hands for test and measurement purposes.
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TECH SERIES
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et’s take a look at how some common, yet critical, measurements can be made for these types of signals. One often-required measurement is to determine the envelope of an RF burst; we’ll look at four approaches to this task. The first example concerns an RF burst with a mean frequency of 9.75 GHz (Figure 1). We can determine the envelope of the bursts by setting up a demodulate math operator on the RF pulse and setting the carrier frequency to 9.75 GHz to measure amplitude modulation. The red trace, F6, is the demodulated carrier.
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We can determine the envelope of the bursts by setting up a demodulate math operator on the RF pulse and setting the carrier frequency to 9.75 GHz to measure amplitude modulation.
Figure 1. Demodulation is one method of determining the envelope of an RF burst
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We can take this a step further to perform measurements on the demodulated waveform. Figure 2 shows the same pulse, but with a split grid to isolate the demodulated waveform from the RF pulses. Measuring the frequency (P7) of the zoomed area of the un-demodulated pulse confirms the frequency of 9.75 GHz. Measuring the width of the demodulated pulses using the width@lvl parameter (P3) yields a mean pulse-width value of some 998 ns, while the edge@lvl parameter (P4) gives us the number of RF pulses.
However, when we measure the frequency of the demodulated waveform (P6), we find a 500-kHz modulation, which tells us the pulse-repetition frequency (PRI), a common RF-burst measurement. We can also measure the PRI using the period parameter (P2), with which we find a PRI value of 1.999 Îźs. This also can be measured directly with an automatic parameter by first demodulating the RF carrier and using standard oscilloscope measurement parameters.
Figure 2. Various measurements may be made on demodulated RF pulses
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TECH SERIES
2 A second approach to determining the envelope of the same 9.75-GHz burst is to perform a Hilbert transform in Matlab. Rather than using demodulation as in the previous method, this approach uses in-line Matlab by applying the Matlab math operator directly to the RF carrier to produce the burst envelope. With Teledyne LeCroy’s LabMaster 10Zi-A oscilloscopes, you can apply this approach at frequencies from DC to 100 GHz in real time.
A second approach to determining the envelope of the same 9.75-GHz burst is to perform a Hilbert transform n Matlab. The actual code for the Hilbert transform is derived by performing the transform on the input waveform, extract the absolute value, and output that value back as a waveform for display on the oscilloscope. It can be done in four separate lines or in a single line of Matlab code (Figure 3). The Hilbert transform waveform updates live and in real time.
Figure 3. A Hilbert transform in Matlab reveals an RF burst envelope
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A third approach to determining an RF burst envelope is to use a combination of three math operators: sparse, absolute value, and ERES (enhanced resolution).
A third approach to determining an RF burst envelope is to use a combination of three math operators: sparse, absolute value, and ERES (enhanced resolution). As shown in Figure 4, with our 9.75-GHz RF burst as the input signal, F7 is set up as the sparse of the absolute value of the RF burst, and F8 is the ERES of that output, chaining three math operators together. The ERES in this example is set at 2 bits, so it’s an FIR filter (Gaussian low pass). The sparse operator decimates the waveform at 500:1 to remove extra samples before filtering. This approach can also be applied at signal inputs of up to 100 GHz on an appropriate oscilloscope.
Figure 4. Determining an RF burst envelope with three chained math operators
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TECH SERIES The fourth method is to use the oscilloscope’s Parameter Track operator. This extremely useful analysis tool plots the results of any given measurement against time, giving you a very clear view of how a parameter changes when measured for a relatively long period. The example shown in Figure 5 is a track plot of the period of a waveform over nine cycles. The Track waveform has all of the properties of an acquired waveform; it can be saved, measured, and analyzed just as acquired waveforms.
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The fourth method is to use the oscilloscope’s Parameter Track operator.
Figure 5. The Parameter Track operator shows how a measurement changes over time
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Modern Test & Measure
In Figure 6, we see an example of applying the Parameter Track operator to a frequency@level measurement on an RF burst. In the image, F7 is the Track plot of P2, which in turn is the frequency measurement of the RF signal. As the frequency drops in value during the electrical idle time between pulses, we see that the Track plot drops concurrently. Again, measurements may be taken on the Track plot. This approach, as with others, can be applied from DC up to 100 GHz in the case of the LabMaster 10Zi-A oscilloscope.
Figure 6. A Track plot of an RF burst’s frequency@level measurement
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PRODUCT WATCH
Chroma
Electric Vehicle
Chroma 8000 Series
Test Solutions As test applications increase within the EV/PHEV market, Chroma has developed a line of Automated Test Systems for Electric and Hybrid Electric Vehicle power components. Unlike specialized equipment that limits test to a single EV model, Chroma’s test systems are based on a standard test platform that seamless integrate a wide range of commercialoff-the-shelf equipment. Its broad range of use combined with PowerPro III, an open architecture software platform, the C8000 platform provides users a flexible, expandable, and cost-effective test system for engineering R&D, design validation and verification, production testing, quality assurance, and incoming inspection for most EV power components.
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This combination of configurable hardware and software enables manufacturers to reduce cost and ensure consistency through all phases of the product lifecycle.
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he Chroma 8000 Automated Test System meets the requirements of SAE J1772 for full function testing of AC level 1 and level 2 electric vehicle supply equipment and is built to address the testing needs of EVs and PHEVs from R&D to QA, production, and field service. The system relies on Chroma’s extensive expertise in power electronics and enables seamless testing of EV supply equipment, on-board chargers, DC-toDC converters, and motor drivers, and other power electronics. The Chroma 8000 test system can be configured with AC and DC power supplies, electronic loads, power analyzers, oscilloscopes, DMMs, as well as digital and analog I/O cards to address the requirements of multiple power electronic systems. In addition to hardware flexibility, Chroma’s Automated Test System software includes a range of prewritten tests and the ability to create custom tests, allowing users unlimited freedom in how their products are tested. The system also provides automatic data recording and statistical report creation, giving insight into opportunities for product improvement. This combination of configurable hardware and software enables manufacturers to reduce cost and ensure consistency through all phases of the product lifecycle.
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Other EV solutions from Chroma include battery and electrical safety testing. Chroma’s battery testers are regenerative, high precision systems specifically designed for cell, module and pack level battery testing. From Charge/Discharge to Drive Cycle Simulation, Chroma’s accuracy in measurement ensures exact and reliable testing for battery incoming or outgoing inspections, as well as capacity, performance, production, and qualification testing. The cost effective regenerative feature recycles energy sourced by the battery module either back to the channels in the system or back to the grid and systems are flexible making field upgrades possible. As always, electrical vehicle safety is of the utmost importance and compliance to several regulation standards is required. Chroma has developed many benchtop and automated test systems to test AC and DC dielectric withstand, isolation resistance, leakage current, and ground bond as well as wound component analyzers. Safety test applications include the power system, motors, batteries, charging system, wiring, charging lines and connectors, and the charging station . For more information, ChromaUSA.com . visit ChromaUSA.com
PRODUCT WATCH
Chroma’s accuracy in measurement ensures exact and reliable testing for battery incoming or outgoing inspections, as well as capacity, performance, production, and qualification testing. Chroma 17030 Series
Chroma 17020 Series
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MYLINK
MYLINK
Modern Test & Measure
IoT Wireless Sensors and the Problem of
Short Battery Life
By Carlo Canziani, Keysight Technologies, Inc.
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TECH REPORT
Wireless sensors provide great insight in applications like monitoring environmental conditions or industrial plants and machinery. Because they are simple to install, they can be deployed in a multitude of situations. In coming years, we will see an explosion of new uses for wireless sensors as the “Internet of Things,” or “IoT,” is widely deployed. But one of the factors that most limits the use of wireless sensors is their limited ability to do the job for a reasonable amount of time. When a wireless sensor’s operation is fully dependent on a battery, and the battery is depleted, it becomes just a piece of junk.
WHEN A WIRELESS SENSOR’S OPERATION IS FULLY DEPENDENT ON A BATTERY, AND THE BATTERY IS DEPLETED, IT BECOMES JUST A PIECE OF JUNK.
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If you are designing battery-operated wireless sensors, you face numerous challenges in ensuring your devices operate for a reasonable amount of time. The typical approach is to use energy for just the required activity, then put the device in low-power-use mode. The operation of a wireless sensor can be segmented in a series of activities, each one requiring a certain level of power for a certain amount of time. The most common activities: •
Waking up, taking a measurement and processing data into a message
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Powering up the RF power amplifier, transmitting the message, and powering the RF PA down again
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In bidirectional sensors (transmit and receive): waking up, powering up the receiver, receiving, processing data, acting on a message, and powering back down
It is easy to see that multiple actions play a role in discharging the battery. The simplest way to increase the battery life is to use a bigger battery, a battery with higher capacity. Nevertheless, your customers are likely to expect their sensors to be small and to offer high performance (so they can send lots of data and have local intelligence/ data crunching capability). Clearly, your customer expectations are diametrically opposed to the easiest way to solve the issue of short battery life.
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How Do Engineers Estimate Battery Life? As a design engineer, you need to start making compromises and find the balance between battery size and the wireless sensor’s functionality to get the best performance from a small battery with a sufficiently long time interval between battery replacements. The optimization process starts by understanding the energy requirements. Gathering data about energy usage is the first step to characterizing device performance. A battery has a defined amount of energy, specified in Watt hours (Wh) and capacity, specified in amp hours (Ah). If you know how much power is required to operate your device, you can calculate the battery life.
Battery life (hours) = Battery capacity (Wh) / Average power drain (W) The battery’s energy is also the product of its voltage rating (V) and capacity (Ah). The voltage rating is a midpoint value on the battery’s discharge curve empirically determined to correctly relate the battery’s energy and capacity. Based on this, battery life can also be determined by the formula:
Battery life (hours) = Battery capacity (Ah) / Average current drain (A)
TECH REPORT However, when the device is in real operation, the battery life is typically shorter than the number you calculated. The most common comment is: “the battery quality is bad.” Representatives for big battery brands will offer detailed specifications and explain that among batteries of the same type, it is common to have capacity variations of 5 to 10 percent. But even using conservative battery capacity estimates, battery life typically falls short. The device dies before it is expected to. Why does this happen? Did we correctly estimate energy usage? Probably not. Let’s explore the problem.
The different operating modes result in a current drain that spans a wide dynamic range from sub-µA to 100 mA, which is a ratio on the order of 1:1,000,000.
The Complexity of Measuring Dynamic Current Drain In battery-powered devices like wireless sensors, to save energy the device sub-circuits are active only when required. Engineers design the device to spend most of its time in a sleep mode with minimum current drain. During sleep mode, only the real-time clock operates. The unit then wakes up periodically to perform measurements. The acquired data is then transmitted to a receiving node.
The DMM is connected in series between battery and device to measure the current. From time to time we see some reading instabilities due to the sensor’s active cycle or even the transmit mode. We know that DMMs have multiple ranges, and with auto range it should be able to select the most appropriate range and give the best accuracy. However, DMMs aren’t ideal. The auto range takes time to change range and settle the measurement results. Time to auto-range is often 10 to 100 ms, longer than transmission or
Traditional Measurement Techniques and Their Limitations A well-known method for measuring current is to use the ammeter function of a DMM. The accuracy of current measurements made with modern digital DMMs looks good, but specifications are defined for fixed ranges and relatively static signal levels, which isn’t exactly the situation on a wireless sensor due to its dynamic current drain.
GATHERING DATA ABOUT ENERGY USAGE IS THE FIRST STEP TO CHARACTERIZING DEVICE PERFORMANCE.
Typical current levels and timing TX Sleep Figure 1. Current levels during the three main states of a wireless sensor
20 - 100 mA
1 - 100 ms
100 µA - 10 mA
10 - 100 ms
500 nA - 50 µA
100 ms - minutes
Table 1.
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active modes times. For this reason, the auto-range function needs to be disabled and the user needs to manually choose the most appropriate range. The DMM makes measurements by inserting a shunt in the circuit and measuring the voltage drop across it. Normally to measure low current, you choose a low range based on a shunt with high resistance; to measure high current you choose a high range based on a lowresistance shunt. The voltage drop is also called burden voltage. Due to this voltage drop, not all the battery voltage reaches the wireless sensor. Most accurate low ranges for sleep current measurements have burden voltage during current peaks that may even cause the device to reset. Practically, we end up compromising and using a high current range that keeps the device operating during current peaks. This compromise enables us to handle peak current and measure the sleep current, but at a high price. As the offset error is specified on range full scale, it heavily impacts measurements on low current levels. Its error contribution can be 0.005% error on 100 mA range = 5 µA, which is a 50% error on 10 µA or 500% error on a 1-µA current level. This current level is where the device spends most of its time, so this error has a huge impact on the battery life estimation. After measuring the sensor’s low current level during sleep mode, we have to measure the active and transmission pulses. Measurements need to include
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both the current level and the time the sensor spends at that level. Oscilloscopes are excellent tools for measuring signals changing over time. However, we need to measure current in the 10’s of mA level, and current probes do not do a good job there due to their limited sensitivity and their drift. Good clamp probes have 2.5-mArms noise, and the zero compensation procedure needs to be repeated often. Current probes measure the electric field over a wire, so the trick to increase sensitivity is to pass the same wire multiple times so we multiply the magnetic field— this multiplies the current readout, enabling us to measure the current a bit better. With this approach, we can capture the current pulse of the activity and the transmission time. Even within the activity and transmission, the current changes levels: it looks like a train of high and low levels. To properly calculate the average current the waveform needs to be exported and all the measured points need to be integrated to get the average value. Oscilloscopes do a good job of capturing a single burst. However, the measurements are more complex if we want to verify how many times the sensor activates in a timeframe and how often it sends out a TX burst. Oscilloscopes can easily do a good job with measurements taken over the short term, but sensors may have operational cycles of minutes or hours, which can be complex to capture and measure.
TECH REPORT Measurement Innovations The Keysight N6781A source/ measure unit (SMU) for battery drain analysis overcomes the limitations of traditional measurements with two innovations: seamless current ranging and long-term gap-free data logging. The SMU is a module that can be used with the Keysight N6700 low-profile modular power system or N6705 DC power analyzer. The seamless current ranging is a patented technology that enables the SMU to change the measurement range while keeping the output voltage stable without any dropout due to ranging. This feature enables you to measure the peaks with high current ranges and measure the sleep current with the 1-mA FS range, which has 100 nA of offset error. This low offset error (100-nA offset error is 10% at 1 µA or 1% at 10 µA), orders of magnitude better than a traditional DMM.
THE SEAMLESS CURRENT RANGING IS A PATENTED TECHNOLOGY THAT ENABLES THE SMU TO CHANGE THE MEASUREMENT RANGE WHILE KEEPING THE OUTPUT VOLTAGE STABLE WITHOUT ANY DROPOUT DUE TO RANGING.
Figure 2. The Keysight N6781A SMU allows accurate measurements across dynamic current levels.
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The seamless current ranging is combined with two digitizers to measure voltage and current with simultaneous sampling at 200 kSa/s (5-µs time resolution). Digitized measurements can be captured over 2 seconds and displayed with full time resolution and proportionally longer time with lower resolution. However, for long-term measurements, the internal data logger in the Keysight N6705B modular DC
power analyzer integrates the 200-kSa/s measurements over a user-specified integration period (20 µs to 60 seconds) without losing any samples between the integration periods. As the data logger is gap-free, all the samples fall in one integration period or in the next one—no samples are lost. With the data logger, engineers can now measure the current and energy drain performance of a wireless sensor for up to 1000 hours of operation.
WITH THE DATA LOGGER, ENGINEERS CAN NOW MEASURE THE CURRENT AND ENERGY DRAIN PERFORMANCE OF A WIRELESS SENSOR FOR UP TO 1000 HOURS OF OPERATION. Figure 3. Data logger: all the samples are integrated in consecutive sample periods. No samples are lost. For every sample period, min and max values are also available.
Figure 4. Recorded current drain over 200 seconds of operation provides new insight into a device’s dynamic current drain.
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TECH REPORT Measuring the sleep current is just a matter of placing the markers and directly reading out the values provided. The measurement in Figure 4 is made with a single acquisition over a long period of time; we get the complete picture of the current drain as well as an accurate measurement of the sleep current at 599 nA.
packet of information is very important when balancing user experience against battery drain and answering questions such as “should I send information once every second, every 5 seconds or every 10 seconds?” Engineers can accurately estimate the battery drain impact of any firmware change and validate it in a reasonable time with real measurements.
With pan and zoom capability, it’s possible to look at the current level and time spent at every power level. Details that traditional measurement tools do not see can now be identified and measured. A clear example is the trailing pulses identified by “???” in Figure 4. The software revealed this surprise: the device drain pulsed energy at ~90 µA peaks for 500 ms for an average current of 3.3 µA. When we add this current drain to the 599 nA sleep current, it moves to 730 nA, 22% higher current than we expected. This type of surprise can be one of the reasons for underestimating energy requirements and delivering a shorter battery life than anticipated.
Joule Measurements Made Easy Joules are useful in battery life estimation, as every activity has a defined amount of energy. We can also compare device performance using Joules/transmitted bits. But engineers rarely use Joules because they need to be calculated from voltage, current and time. With the Keysight 14585A control and analysis software, energy in Joules can be measured directly. For example, you might measure the energy consumed by transmitting a packet (see Fig. 5) captured with a triggered measurement. This is one benefit of having two digitizers for
WITH THE KEYSIGHT 14585A CONTROL AND ANALYSIS SOFTWARE, ENERGY IN JOULES CAN BE MEASURED DIRECTLY.
In wireless sensor power optimization, engineers get great value by understanding the details. Knowing how much energy it takes to send out a single
Figure 5. Using Keysight 14585A software, you can measure energy directly in Joules.
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voltage and current with simultaneous sampling that enable point-by-point power measurements. Joules can be easily read out as a value between the markers, and designers can go a step further by defining Joules/transmitted bit.
Summary Engineers who design IoT batterypowered devices use advanced power management techniques to conserve battery life. Traditional measurement techniques are complex, time consuming and don’t deliver the measurement accuracy required to optimize and validate battery drain, and often this causes engineers to underestimate the power required to operate the device.
The Keysight SMUs for battery drain analysis enable accurate current drain analysis with one picture that provides a complete and detailed current and energy drain analysis. Postanalysis software simplifies the engineer’s job by offering visibility into details never seen before. With Keysight’s latest introduction of the N6785A SMUs for battery drain, these capabilities are now available up to 80 W and from nA to 8 A. The new SMUs are used in multiple applications from smartphone and tablet testing to automotive ECU and IoT wireless sensors and chipsets. www.keysight.com/find/N6781A-EU
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Modern Test & Measure
Bridging the Gap Crucial Test Probes from Picotest Bolster Innovations in Power Integrity Interview with Steve Sandler, CEO – Picotest
“We don’t make instruments per se; we make the probes, interface accessories, and training tools that make these instruments better and more useful.” 28
INDUSTRY INTERVIEW
PICOTEST is a relatively new test equipment provider. Founded in 2010 by Steve Sandler, Picotest aims to provide the test tools needed to conduct accurate power integrity measurements—from signal injectors to PDN probes. Sandler found that most popular measurement instruments provided lower functionality than they were actually capable of, allowing Picotest to serve a market niche that enables engineers to get more out of their test equipment. This unique focus caught the eye of Keysight—one of the largest test equipment providers in the world—who recently named Picotest a “Keysight Solutions Partner,” which broadened the company’s reach tenfold. EEWeb recently spoke with Steve Sandler about the new opportunities from the Keysight partnership, some of the biggest challenges facing the test industry, and how the power market benefits from Picotest solutions.
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What led you to start Picotest? I started my first real company, AEi Systems, in 1995 and the company is currently the largest analysis and simulation company for the satellite market. The very first project we won was for the worst-case analysis of the International Space Station (ISS) power bus. It was huge for us and it really launched the business. While we were doing the large-scale circuit modeling for this project, we noticed that the majority of the data that we got was bad, which was true whether it came from manufacturers of the components or from the space company’s lab— around 50-percent of it was invalid. We also noticed that the SPICE models themselves were generally inaccurate, so we went off on this quest to try to figure out why the measurements were so bad and whether or not there was a way to make measurements in a simpler format that provides high resolution. The quest worked for us, and AEi Systems has used these measurement techniques since the late ‘90s. In 2010, I founded Picotest because we had built what amounted to a product line of signal injectors, probes, and accessories that we were using for
various projects, and people started asking if they could buy them. We discovered a company in Taiwan that was willing to manufacture them and from there, things took off. Since 2010, we have currently sold product in 35 countries and to nearly every Fortune 500 electronics company. We don’t make instruments per se; we make the probes, interface accessories, and training tools that make these instruments better and more useful. We work closely with all of the major instrument companies. Just this year, we became a Keysight Solutions Partner, which was a big deal for us. This was real recognition from the largest test equipment company in the world, saying that we have something that a lot of companies need. Since becoming a Keysight Solutions Partner, we have really broadened our reach .
How does Picotest fit in to the test and measurement landscape? Let’s say you are an engineer and you understand the measurements you need to make, so you buy a vector network analyzer (VNA). However, when you go to make a Bode plot, you realize that most large test instrument manufacturers do not make the signal injection transformer accessory needed for the test; this is
“They are not coming to us because we only make a probe, they are coming to us because together we can help them with a particular measurement and we have the hardware solutions.”
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INDUSTRY INTERVIEW one of the first ways we got noticed by Keysight, because they did not make the signal injection transformer that they required for their frequency response analyzer, so they started recommending ours. If you want to make a two-port impedance measurement with a VNA for power integrity, you need a commonmode coaxial transformer, which is also not offered. If you want to make PSRR measurements, and the analyzer is very capable of that, you will need a power supply modulator for the test. Picotest makes these essential devices that connect the instrument to the board you want to measure.
How does your new partnership with Keysight broaden your business and your reach? Obviously, the difficulty of a small business like Picotest is that we do not currently have a large sales staff. For us to build a sales channel from the ground up is challenging especially given the price point of the add-on accessory market. A company like Keysight provides us with opportunities that we normally wouldn’t get by allowing us to be part of the initial sale as well as having access to a huge existing customer base. The reason I became an engineer was to try and help change the world and the way that engineers make products. Our relationship with Keysight gives us access to tens of thousands of engineers who just want to make good measurements and can use our expertise and products. More specifically, every test and instrument company we have worked
with, and that includes all of the major oscilloscope manufacturers, has said that they want to “own the power market”, yet they really didn’t know quite what that means. We do. Keysight is the only test equipment company that makes instruments in every measurement domain (time, frequency, spectrum)— no matter what kind of measurement I want to make, Keysight has an instrument for it. We offer Keysight an in-depth knowledge of the power integrity marketplace and measurement needs. They even have great simulation technology that can be easily adapted to serve power supply engineers. These are the kinds of avenues that this relationship now opens for us— we get things from them, like sales channels and access to instruments, while we fill the need that they have for useful accessories that give their instruments a competitive edge and a power integrity marketplace expert. It’s a mutually beneficial relationship.
What do you see in the next two to five years in the power market?
“Our relationship with Keysight gives us access to tens of thousands of engineers who just want to make good measurements and can use our expertise and products.”
The power market is changing so much. There are companies that are doing a lot of work with gallium nitride (GaN) working towards wireless power. That in itself will cause a major change in the way power systems are designed and measured. We are not only talking about near-field power communication like the pad you put your phone on to charge it, but far-field power, where you can drive your car into the garage and it will charge itself. In that sense, power becomes much broader.
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Switching frequencies are also getting much higher. All of a sudden, power engineers are dealing with RF and microwave issues, which will only get more challenging. Back in the 1980s, bipolar transistors were the popular switches of the day and MOSFETs were coming into being; it was a very difficult transition. All of a sudden, we had very fast devices and we couldn’t quite figure out how to harness them. The inductors in our wiring and our traces were not compatible with the high speeds of the MOSFET. We are back to where we were in the 1980s; now we have GaN coming into play, which is a breakthrough technology. The average power engineer needs to have basic RF and microwave skills. Everything is also much more integrated now.
systems. Bode plots will be a thing of the past for most power supplies and we will have more methods of measurement.
If you take a look at a smartwatch and how many power related components are included, in terms of making measurements, there is almost no access in the traditional sense. The big question is how will we measure stability if we can’t even measure Bode plots? With most of these new devices we can’t see anything aside from an output capacitor. The average PMIC in a smartphone has more than 20 power supply rails within a quarter of a square inch. Picotest plays a role in this market through our unique non-invasive stability measurement software solution. We can tell you the phase margin of a circuit from an impedance measurement. I don’t believe there is another company in the world that can do that today. That is going to be a major change in the way we evaluate electronics and control
What do you see as the biggest challenge in getting the power and RF fields working together to overcome these issues?
One of the things I remind engineers of all the time is that power integrity and signal integrity are two different things, but not entirely. Signal integrity is the transmission of high-frequency signals. Power integrity is the transmission of power, but power is actually a signal. What the world is coming to realize is that power is still a signal at 70 GHz, with signal integrity properties. There is going to have to be a translator between the power guys and the digital and RF guys because a lot of the time, they don’t speak the same technical language when it comes to power integrity figures of merit.
There are two major challenges here. The first is that most companies are not investing in their engineers. Average engineers do not have the opportunity to get the continuing education that they need—they are not going to the conferences and they are not reading the books. Part of the blame falls on the semiconductor industry, which really wants to make all of this design stuff seem easy, and which generally doesn’t work. We find a lot of problems at the semiconductor and reference circuit level and we go back to the manufacturers and confront them about bad advice they give to customers. They tell us that they do
INDUSTRY INTERVIEW it because it simplifies the adoption of the part, which is what their customers want. While customers do want simple solutions, they also need viable solutions. There is also the issue of momentum, which is huge. You cannot make Bode plots anymore on an increasing proportion of power ICs—the control loop just isn’t exposed. For example, if I buy a voltage reference and I connect it to my ADC, the ADC performance is directly tied to the quality of the voltage reference output. If I put the ceramic output capacitor that the semiconductor company tells me to add, the output suddenly has very poor stability resulting in a poorly performing ADC. There is no way to know that using
traditional methods because there is no way to measure a Bode plot, which is how we generally assess stability. Picotest offers customers a solution for this problem. You can use our noninvasive probe on the output capacitor and it will tell you, with a simple cursor measurement, the phase margin of that reference or regulator. But, you are fighting 50-years of momentum because people trust Bode plots for stability—they don’t recognize noninvasive impedance based methods. It is going to take time for that measurement to evolve to the point where it becomes trusted and people feel confident with it and realize the difference that good stability makes in the performance, costs, and optimization of their products.
“The average PMIC in a smartphone has more than 20 power supply rails within a quarter of a square inch. Picotest plays a role in this market through our unique non-invasive stability measurement software solution.”
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Picotest is addressing this problem by presenting a lot of webinars and teaching about what we do in this low-frequency range in power and how it affects the RF and microwave areas. This is another place where our relationship with Keysight is a really big deal. For example, at the DesignCon conference in January, we are providing a 6-hour boot camp on power integrity. They call it “boot camp” because it is very in-depth. It is an interesting collaboration that will help engineers solve unique and current problems. Picotest is delivering the first three-hour session and Keysight is delivering the second three-hour session. Picotest is delivering all of that training on the low-frequency end—the power supplies, VRMs, and decoupling—and
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Keysight is focusing on what happens with the power the VRM provides when they look at data channels and clock jitter and other high-frequency issues. We are bridging this gap in the power integrity boot camp to demonstrate that what is happening at these low frequencies is hurting the design efforts at high frequencies. The stuff you learn from manufacturers is counter-intuitive, which is actually another challenge in this area. For example, one of the things we teach in our lectures is that one of the biggest challenges in power integrity today is that the voltage regulation has gotten much too good. People always claim that tighter voltage regulation is a really good thing. In fact, it usually
INDUSTRY INTERVIEW isn’t. If you look at your printed circuit boards as transmission-line planes and you make your power supply have zero impedance, you essentially just built a resonant plane that has infinite Q. But what does a power guy know about transmission-line Q? Usually, not much. Picotest demonstration and training test boards and the Power Integrity boot camp show engineers the impact the power supply has when it powers a lowjitter clock. We are showing them that the better they make the regulation of that power supply, the worse the clock-jitter is getting. That is a tough problem to bridge because it is counterintuitive and it is at a frequency range that power engineers aren’t always familiar with using instruments that they don’t usually own.
“Picotest is addressing this problem by presenting a lot of webinars and teaching about what we do in this low-frequency range in power and how it affects the RF and microwave areas. “
Assuming that one day these challenges are overcome, what do you think the benefit will be to the industry and the consumer? There are a lot of benefits. First, we can optimize the performance of circuits, meaning performance will go up considerably. Second, we are going to deal with fewer parts, which means costs will go down and product sizes will keep shrinking. Third, we are going to develop products a lot faster. Translated to the consumer, products will be smaller, lighter, and cheaper.
What excites you about going into work each day? I really like the challenges that I face in preparing the younger generation for what is next. I have been in the industry for over 40 years, and my major motivation now is still to try and improve the world. I can provide experience and mentoring to young students and contribute to endeavors that move technology forward. Anything that I can do to help move technology forward is exciting to me. Most of those result in new Picotest products, and every time we launch a product, I get excited about seeing the first customer take advantage of what we have created. It is also always exciting to work with our customers in the trenches. They are not coming to us because we only make a probe, they are coming to us because together we can help them with a particular measurement and we have the hardware solutions. I love the fact that our job is to do our best to overcome those challenges and in general, we can.
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