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At the Optical Fiber Communication Conference and Exhibition (OFC 2025) in San Francisco (1-3 April), Keysight Technologies Inc of Santa Rosa, CA, USA, Japan-based NTT Innovative Devices Corp, and Lumentum Holdings Inc of San Jose, CA, USA (which designs and makes optical and photonic products for optical networks and lasers for industrial and consumer markets) have given joint demonstration of 448Gbps data transmission using 224GBaud PAM4 optical technology...

Fractal Antenna Systems has introduced Acoustic Resonance Mitigation (ARM), a technology that disables drones using directed acoustic energy. ARM emits sonic, ultrasonic, and subsonic waves to induce vibrations or Prandtl boundary layer instability, leading to flight failure. Propeller blades are especially vulnerable, as turbulence or vibrations can disrupt a drone’s inertial measurement unit (IMU).

Portions of an ARM button array (non-parametric) for a DRONE BLASTR airborne drone.

ARM technology, co-invented by Fractel CEO Nathan Cohen, is backed by U.S. patents and licensed to Fractal. The technology has been demonstrated by foreign groups, though U.S. patents predate these efforts, according to Cohen. Cost-effective and portable, ARM is specifically designed to disable drones, from microdrones to pizza box-sized devices.

In military applications, ARM can be deployed on attack drones to disable adversarial swarms. Known as the DRONE BLASTR, this patent-pending in situ device offers a new method for countering drone swarms. Beyond the battlefield, ARM offers a countermeasure against drones used in illegal surveillance and smuggling.

A timeline for commercialization was not available at the time of this announcement. Government, public safety agencies, and related enterprises can contact Fractal for more information.

Fractal Antenna Systems 

Find more datasheets on products like this one at Datasheets.com, searchable by category, part #, description, manufacturer, and more.

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Keysight and Coherent showcased 200G-per-lane VCSEL technology at OFC 2025, demonstrating characterization, tuning, and validation. The multimode VCSEL enables higher data transfer rates to meet growing data center bandwidth demands.

Keysight’s M8199B 256-Gsample/s AWG

The 200G multimode VCSEL enhances data transfer and network efficiency by doubling data throughput to 200 Gbps per lane, surpassing current multimode interconnects. It offers significant power savings per bit compared to single-mode alternatives, and its lower manufacturing costs make it a more economical choice for short-reach data links. Well-suited for AI pods and clusters, this VCSEL supports the high-speed, short-reach interconnects essential for GPU-driven data sharing.

The setup used at OFC featured Keysight’s DCA-M wideband multimode sampling oscilloscope, M8199B 256-Gsample/s arbitrary waveform generator (AWG), and Coherent’s 200G VCSEL. The AWG drives a 106.25-GBaud PAM4 signal into the VCSEL, with the optical output measured on the oscilloscope to display the eye diagram. This demonstrates the VCSEL’s feasibility and Keysight’s characterization and validation capabilities.

Keysight Technologies 

Coherent

Find more datasheets on products like this one at Datasheets.com, searchable by category, part #, description, manufacturer, and more.

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Vishay’s VEML6046X00 RGB IR sensor is AEC-Q100 qualified for use in vehicle displays and interior lighting. This compact device integrates a photodiode, low-noise amplifier, and 16-bit ADC in an opaque surface-mount package that is just 2.67×2.45×0.6 mm.

With three color channels and one infrared channel, the VEML6046X00 calculates color temperature to enable white point balancing for displays. Its green channel’s spectral sensitivity aligns with the human eye for accurate measurements, while the IR channel stabilizes output across various light sources.

The sensor performs consistently in daylight with an ambient light range of 0 to 176 klx, preventing saturation. A digital resolution of 0.0053 lx/count allows the VEML6046X00 to operate behind dark cover glass. It supports a supply range of 2.5 V to 3.6 V, an I2C bus voltage range of 1.7 V to 3.6 V, and an ambient temperature range of -40°C to +110°C. Typical shutdown current consumption is 0.5 µA.

The sensor is well-suited for automotive display backlight control, infotainment systems, rear-view mirror dimming, and heads-up displays.

Samples and production quantities of the VEML6046X00 RGB IR sensor are available now, with a lead time of 16 weeks.

VEML6046X00 product page

Vishay Intertechnology 

Find more datasheets on products like this one at Datasheets.com, searchable by category, part #, description, manufacturer, and more.

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ST’s four-channel high-side switches, the IPS4140HQ and IPS4140HQ-1, drive resistive, capacitive, and inductive loads with one side connected to ground. The IPS4140HQ handles up to 0.6 A per channel, while the IPS4140HQ-1 supports up to 1.0 A. Both have a maximum RDS(on) of 80 mΩ per channel and include extensive diagnostic and protection features.

Housed in compact 8×6-mm QFN48 packages, the devices operate from a 10.5-V to 36-V supply and tolerate up to 41 V for enhanced system safety and reliability. Applications include programmable logic controllers, industrial PC I/O ports, and numerical control machines.

These intelligent power switches provide per-channel short-circuit protection, temperature monitoring, and independent restart to boost fault tolerance and simplify automated recovery. Additional safeguards include case-overtemperature shutdown with sequential restart, output current limiting, undervoltage lockout, and input overvoltage protection. With 5-V/3.3-V logic compatibility, EAS ratings up to 2.5 J per channel, and compliance with IEC 61000-4 and IEC 61131-2 standards, they ensure robust performance in industrial applications.

Prices for the IPS4140HQ and IPS4140HQ-1 high-side switches start at $2.59 in lots of 1000 units.

STMicroelectronics

Find more datasheets on products like this one at Datasheets.com, searchable by category, part #, description, manufacturer, and more.

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Infineon is developing TRENCHSTOP H7 IGBTs in a DTO247 package, which is twice the size of a standard TO247. A single high-current IGBT in a DTO247 can replace multiple lower-current TO247 IGBTs connected in parallel. Engineering samples of the 200-A and 350-A H7 IGBT variants are available now.

The DTO247 enables high power density and bridges the gap between TO247-based designs and module architectures. Additionally, its compatibility with both DTO247- and TO247-based architectures within the same system provides greater flexibility and customization. H7 IGBTs can be used in solar inverters, uninterruptible power supplies, and energy storage systems.

The DTO247-packaged portfolio will include 1200-V and 750-V H7 IGBTs with current ratings of 200 A, 250 A, 300 A, and 350 A. They feature 2-mm-wide leads for optimal conduction, a 7-mm pin-to-pin clearance, and a 10-mm creepage distance for enhanced safety and reliability. An integrated Kelvin emitter pin enables faster, more efficient switching.

Volume production of the TRENCHSTOP H7 IGBTs in DTO247 packages is scheduled for mid-2026. Datasheets were not available at the time of this announcement.

Infineon Technologies

Find more datasheets on products like this one at Datasheets.com, searchable by category, part #, description, manufacturer, and more.

The post Infineon prepares DTO247-packaged IGBTs appeared first on EDN.

Keysight Technologies Inc of Santa Rosa, CA, USA and materials, networking and laser technology firm Coherent Corp of Saxonburg, PA, USA have collaborated on a 200G multimode technology demonstration showcased for the first time at the Optical Fiber Communications Conference & Exposition (OFC 2025) in San Francisco (1–3 April). The 200G-per-lane vertical-cavity surface-emitting laser (VCSEL) technology provides higher data transfer rates and addresses industry demand for higher bandwidth in data centers. It should enable the industry to deliver AI/ML services while reducing power consumption and capital expense of short-reach data interconnects...

One of my jobs as an engineer was working in the engineering department of an electronic contract manufacturer. Our department designed test equipment for the manufacturing lines, but we also assisted customers with their products issues.

Do you have a memorable experience solving an engineering problem at work or in your spare time? Tell us your Tale

The product being built on the line was a PCB assembly for a coffee maker. One day, the boss came to me and said the customer is getting some complaints about the coffee maker display and controls locking up. He assured the customer we could fix their problem (even though no one knew what the issue was).

The first task was to reproduce the problem. With no clue as to how this problem happened, I started by just letting the coffee makers run. After a few days, nothing—so I tried other things like banging it and shaking it…nothing. I then pushed the buttons in every combination and cadence I could come up with – still no luck. Next ,I tried varying the line voltage slowly from the specified minimum to the specified maximum. The coffee maker still worked fine. I was running out of ideas. Finally, I tried one last thing: I plugged it into a controller that turns the line voltage on and off at varying rates. After a while it locked up.

This behavior hinted at the micro’s reset circuit so I dug into that. It wasn’t the typical design used in those days, a simple RC circuit. The resistor tied to Vcc and the capacitor tied to digital ground, then the other ends of the resistor and capacitor were tied together, and that tied to the micro’s reset.

After a little more testing I concluded that it was due to a fast interruption in the line voltage or a brownout. Either would cause the reset capacitor to discharge partway and then to reset back to Vcc. The micro wasn’t happy with this as it lost power but didn’t get a valid reset.

The boss was happy I found the root cause but now said “fix it” and the fix had to be something easy to tack on to the existing PCB. I spent a few days looking at things like changing the resistor or capacitor value or adding a 555 timer, comparator, or op-amp, but these either didn’t work or were too difficult or expensive to add to the PCB.

That’s when I remembered an obscure device I had read about, a programmable unijunction transistor, or PUT. This has some properties like an SCR. The PUT has 3 pins: anode, cathode, and gate. So, the circuit I came up with was this:

The schematic of the coffee maker fix, introducing the PUT to successfully manage failures due to interruptions in the line voltage or brownouts.

When Vcc is good, the anode to cathode is not conducting, but when the Vcc drops the capacitor stays up for a while, but the PUT triggers if the gate drops below the anode by 0.7v or more. This trigger turns on the anode to cathode path and the capacitor is quickly discharged. This fixed the problem and the PUT and resistor were easily tacked onto the existing PCB.

Damian Bonicatto is a consulting engineer with decades of experience in embedded hardware, firmware, and system design. He holds over 30 patents.

Phoenix Bonicatto is a freelance writer.

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Milestone Systems, a leading provider of open platform video management software announced the release of XProtect 2025 R1, featuring expanded cloud integration capabilities and advanced vehicle identification video analytics. This release demonstrates Milestone’s commitment to platform accessibility and enhanced security features across its XProtect product line.

Extended Arcules Plugin Support Broadens Cloud Integration Options

The XProtect 2025 R1 release, available from March 18 marks a significant expansion in platform accessibility, with the Arcules Plugin now supporting XProtect Professional+, Expert, and Corporate editions. This enhanced integration enables seamless video and alarm flow from the Arcules Video Surveillance as a Service (VSaaS/cloud solution) to XProtect across a broader range of deployments, opening new possibilities for system integrators and end users.

Previously available only for XProtect Corporate users, the Arcules Plugin has been redesigned as a standalone device solution, eliminating the requirement for interconnect licensing. This strategic enhancement allows organizations using XProtect Professional+, Expert, and Corporate to leverage Arcules’ capabilities, significantly expanding market accessibility and integration options.

Advanced Analytics Transform Vehicle Identification and Tracking

The XProtect License Plate Recognition extension in XProtect 2025 R1 introduces comprehensive enhancements that elevate vehicle identification to new levels of sophistication. These updates enable more precise and efficient vehicle analytics, including:

• Vehicle Classification: Enables differential processing based on vehicle type, from motorcycles to buses
• Color Recognition: Facilitates rapid vehicle identification for security and law enforcement
• Make/Model Detection: Enhances vehicle identification accuracy for investigative purposes
• Vehicle Angle Detection: Determines vehicle orientation relative to camera position

These advanced capabilities within the XProtect LPR extension accelerate vehicle identification processes, allowing security personnel and law enforcement to quickly locate and identify vehicles of interest. The system’s enhanced capabilities support rapid filtering of video data based on specific vehicle characteristics, speeding up investigation processes and improving response times.

Transformative Impact on City Operations

Beyond security applications, the enhanced vehicle analytics provide valuable insights for urban planning and traffic management. The system’s ability to analyze various vehicle types and their movement patterns enables:

• Data-driven traffic flow optimization
• Strategic congestion management
• Environmental impact assessment through traffic pattern analysis
• Informed infrastructure development planning

This latest release continues Milestone’s tradition of innovation in video management technology, providing partners and customers with advanced tools to enhance security operations and leverage video data for broader operational insights.

The post Milestone Systems Expands XProtect with Enhanced CLOUD Integration, Advanced Vehicle Analytics appeared first on ELE Times.

Automotive Grade Device Allows for the Calculation of Color Temperature, Light Source Differentiation, and Placement behind Dark Cover Glass

The Optoelectronics group of Vishay Intertechnology, Inc. introduced the industry’s first AEC-Q100 qualified RGBIR color sensor. The Vishay Semiconductors VEML6046X00 features a highly sensitive photodiode, low noise amplifier, and 16-bit ADC in a miniature, opaque 2.67 mm by 2.45 mm surface-mount package with a low 0.6 mm profile.

With separate red, green, blue, and infrared channels, the Automotive Grade device released today allows for the calculation of the color temperature to enable white point balancing for displays. The spectral sensitivity of the VEML6046X00’s green channel matches that of the human eye to ensure highly accurate measurements, while IR channel facilitates a stable output over a wide range of light sources. With an ambient light range from 0 lx to 176 klx, the sensor will not saturate in daylight, while its high sensitivity of 0.0053 lx/ct allows the device to be placed behind dark cover glass.

Offering a high operating temperature range to +110 °C, the VEML6046X00 will be used for automotive display backlight controls, infotainment systems, rear view mirror dimming, interior lighting control systems, heads-up displays, color recognition, CCT measurement, mood lighting, and laser front light monitoring. The sensor supports the easy to use I²C bus communication interface for these applications and offers an interrupt function.

The VEML6046X00 features a supply voltage range of 2.5 V to 3.6 V, I²C bus voltage range of 1.7 V to 3.6 V, and low shut down current consumption of 0.5 μA typical. RoHS-compliant, halogen-free, and Vishay Green, the device offers a Moisture Sensitivity Level of 2a and a floor life of four weeks in accordance with J-STD-020E.

The post Vishay Intertechnology Releases AEC-Q100 Qualified RGBIR Color Sensor in Compact 2.67 mm x 2.45 mm x 0.6 mm Package appeared first on ELE Times.

• Validates the performance of AI infrastructure by emulating real-world workloads
• Evaluates how new algorithms, components, and protocols improve the performance of
  AI training
• Adjusts and optimizes the parameters of both AI workloads and system infrastructure without investing in expensive large-scale deployments

Keysight Technologies, Inc. introduces Keysight AI Data Center Builder, an advanced software suite that emulates real-world workloads to evaluate how new algorithms, components, and protocols impact the performance of AI training.KAI Data Center Builder’s workload emulation capability integrates large language model and other artificial intelligence model training workloads into the design and validation of AI infrastructure components – networks, hosts, and accelerators. This solution enables tighter synergy between hardware design, protocols, architectures, and AI training algorithms, boosting system performance.

AI operators use various parallel processing strategies, also known as model partitioning, to accelerate AI model training. Aligning model partitioning with AI cluster topology and configuration enhances training performance. During the AI cluster design phase, critical questions are best answered through experimentation. Many of the questions focus on data movement efficiency between the graphics processing units. Key considerations include:

• Scale-up design of GPU interconnects inside an AI host or rack
• Scale-out network design, including bandwidth per GPU and topology
• Configuration of network load balancing and congestion control
• Tuning of the training framework parameters

The KAI Data Center Builder workload emulation solution reproduces network communication patterns of real-world AI training jobs to accelerate experimentation, reduce the learning curve necessary for proficiency, and provide deeper insights into the cause of performance degradation, which is challenging to achieve through real AI training jobs alone. Keysight customers can access a library of LLM workloads like GPT and Llama, with a selection of popular model partitioning schemas like Data Parallel, Fully Sharded Data Parallel, and three-dimensional parallelism.

Using the workload emulation application in the KAI Data Center Builder enables AI operators to:

• Experiment with parallelism parameters, including partition sizes and their distribution over the available AI infrastructure
• Understand the impact of communications within and among partitions on overall job completion time Identify low-performing collective operations and drill down to identify bottlenecks
• Analyze network utilization, tail latency, and congestion to understand the impact they have on JCT

The KAI Data Center Builder’s new workload emulation capabilities enable AI operators, GPU cloud providers, and infrastructure vendors to bring realistic AI workloads into their lab setups to validate the evolving designs of AI clusters and new components. They can also experiment to fine-tune model partitioning schemas, parameters, and algorithms to optimize the infrastructure and improve AI workload performance.

Ram Periakaruppan, Vice President and General Manager, Network Test & Security Solutions, Keysight, said: “As AI infrastructure grows in scale and complexity, the need for full-stack validation and optimization becomes crucial. To avoid costly delays and rework, it’s essential to shift validation to earlier phases of the design and manufacturing cycle. KAI Data Center Builder’s workload emulation brings a new level of realism to AI component and system design, optimizing workloads for peak performance.”

KAI Data Center Builder is the foundation of the Keysight Artificial Intelligence architecture, a portfolio of end-to-end solutions designed to help customers scale artificial intelligence processing capacity in data centers by validating AI cluster components using real-world AI workload emulation.

Keysight will showcase KAI Data Center Builder and its workload emulation capabilities in booth 1301 at the OFC 2025 conference, April 1-3, at the Moscone Center, San Francisco, California.

The post Keysight Introduces AI Data Center Builder to Validate and Optimize Network Architecture and Host Design appeared first on ELE Times.

18 x 2n2222 transistors submitted by /u/Careful-Rich9823 [link] [comments]

Device Offers Wide Power Supply Range from 1.65V to 3.6V and
Fast Access Time Down to 10 ns

To meet the demand for high-density fast CMOS SRAMs, Alliance Memory today introduced a new 32Mb device in the 6 mm by 8 mm 48-ball FBGA package. Configured as 2M x 16, the AS7CW2M16-10BIN offers a wide power supply range from 1.65V to 3.6V.

“As other manufacturers continue to phase out their SRAM offerings, Alliance Memory remains committed to supporting the market with a wide range of fast memory solutions,” said David Bagby, president and CEO of Alliance Memory. “Our latest device not only provides our customers with a higher density option but also offers increased flexibility by supporting both 1.8V and 3.3V operating voltages in a single part.”

Operating from a single 1.8V, 2.5V, or 3.3V power supply, the device released today is optimized for consumer TVs and digital cameras, industrial robotics, networking routers, medical equipment, and high-speed automotive systems. For these applications, the AS7CW2M16-10BIN provides fast access times down to 10 ns minimum, data retention voltages down to 1.5V minimum, and low power consumption with operating currents down to 43mA typical and standby current of 10mA typical.

The SRAM features TTL-compatible inputs and outputs, tri-state output, easy memory expansion with chip select (CS) and output enable (OE) functionality, and data control for upper and lower bytes. The RoHS-compliant device operates over a -40°C to +85°C temperature range.

The AS7CW2M16-10BIN is the latest addition to Alliance Memory’s full range of fast SRAMs, which include devices with densities from 64Kb to 16Mb. Fabricated using high-performance, high-reliability CMOS technology, the ICs provide reliable drop-in, pin-for-pin-compatible replacements for a number of similar solutions.

Device Specification Table:

Part	Density	VCC (V)	tAA (ns)	VDR (V)	ICC (mA)	ISB1 (mA)	Package	Temp. (°C)
AS7CW2M16-10BIN	32Mb	3.3	10	2.0	45	10	48-ball FBGA	-40 to +85
		2.5	10	2.0	45	10
		1.8	12	1.5	43	10

Samples and production quantities of the new fast SRAM are available now, with lead times of eight to 10 weeks. The AS7CW2M16 32Mb fast SRAM part will also be available in a TSOP package later in Q2 2025.

The post Alliance Memory Launches New 32Mb Fast SRAM in 48-ball FBGA Package appeared first on ELE Times.

submitted by /u/irf3205 [link] [comments]

Works with basically everything, the sound card is from a usb-c headset submitted by /u/The-Devil-Itself [link] [comments]

Industrial gas company Taiyo Nippon Sanso Corp (TNSC) of Tokyo, Japan (part of Nippon Sanso Holdings Group) says that a TNSC SR4000HT metal-organic chemical vapor deposition (MOCVD) reactor is being purchased by the University of South Carolina for R&D of advanced ultrawide-bandgap nitride materials and device technology...

POET Technologies Inc of Toronto, Ontario, Canada — designer and developer of the POET Optical Interposer, photonic integrated circuits (PICs) and light sources for the hyperscale data-center, telecom and artificial intelligence (AI) markets — has partnered with Lessengers Inc of Seoul, South Korea — which provides optical components based on its patented direct optical wiring (DOW) technology — to offer a differentiated 800G DR8 transceiver. The transceiver will include POET’s transmit and receive optical engines and Lessenger’s Direct Optical Wiring (DOW) technology for a cost-effective solution for AI and hyperscale data center applications...

Sivers Semiconductors AB of Kista, Sweden (which supplies RF beam-former ICs for SATCOMs and photonic lasers for AI data centers) has announced a strategic partnership with optical communications device maker O-Net Technologies (Group) Co Ltd of Shenzhen, China to produce high-performance external laser sources, a critical component enabling next-generation AI data center architectures...

Editor’s note:

In this DI, high school student Tommy Liu modifies a popular low-cost DIY oscilloscope to enhance its input noise rejection and ADC noise with anti-aliasing filtering and IIR filtering.

Part 1 introduces the oscilloscope design and simulation.

Part 2 will show the experimental results of this oscilloscope.

Introduction

A digital oscilloscope is one of the most essential pieces of equipment for high school electrical and electronic labs. As useful and popular as it is for high schoolers, the cost of an oscilloscope can often be prohibitive. Professional digital oscilloscopes are generally expensive, with the entry cost of a basic model ranging from several hundred dollars to over a thousand dollars. One can argue that the advanced specifications and functionalities of these oscilloscopes often exceed most high school needs.

Wow the engineering world with your unique design: Design Ideas Submission Guide

Low-cost DIY digital oscilloscopes provide another option for high schools—these oscilloscopes are inexpensive and typically cost less than a hundred dollars. The problem with DIY oscilloscopes is their performance—they lack measurement precision and the capability of noise immunization. Most DIY oscilloscopes only reach an effective resolution of 6 to 8 bits—even for those with a 12-bit ADC—due to poor noise isolation and rejection. These drawbacks limit DIY digital oscilloscopes from precision measurement and other more demanding applications in high school labs and clubs.

The first part of this design idea (DI) describes a practical, low-cost, and high-performance digital oscilloscope solution suitable for professional high school use, including precision signal measurement and analysis. The second part of this DI describes the experimental results obtained after building it.

The oscilloscope is based on a popular low-cost DIY platform. Analog and digital signal processing techniques, namely anti-aliasing filtering, and infinite impulse response (IIR) digital filtering, respectively, are implemented on the platform, significantly improving the noise rejection and measurement precision of the oscilloscope, with only a minor increase in cost.

Specifications ENOB

In many high school applications of oscilloscopes, an effective resolution of 6 bits to 8 bits is usually sufficient. However, for the most demanding professional high school STEM projects, sometimes a measurement precision within a few mV is required. As the full-scale range of these signals are typically within 3.3 V or 5 V, this requires a measurement precision of about one in a thousand (1/1000), or an effective number of bits (ENOB) of around 10 bits. Since the ENOB of ADCs is lower than their resolution, to achieve 10 bits of effective resolution, the scope’s ADC usually needs to be 12-bit or higher.

Signal bandwidth

Most high-school electronic projects deal with signals from DC to audio frequency (20 Hz to 20 kHz). An analog bandwidth (-3 dB) of 100 kHz is chosen, and the oscilloscope needs to maintain an effective resolution of 10 bits with an input frequency up to 20 kHz.

Table 1 summarizes the major specifications of the oscilloscope, including the precision requirement, input bandwidth, and necessary functions for various high-school users on electrical and electronic projects. As a low-cost solution for high schools, we determined the build of materials (BOM) cost should be less than fifty dollars.

Analog bandwidth (-3dB)	100 kHz
Resolution of ADC	12-bit
Maximum real-time sampling rate	1 MSPS
Effective resolution (ENOB)	10 bits (input from DC to 20 kHz)
Maximum input voltage	50 V (peak-peak)
Voltage division range	10 mV/div – 5 V/div
Time division range	5 s/div – 10 µs/div
Trigger sources	Internal/External
BOM cost	$50 max

Table 1 the major specifications of the oscilloscope, including the precision requirement, input bandwidth, and necessary functions for various high-school users on electrical and electronic projects.

Pros and cons of common DIY scope

The DSO138-mini, a popular type of DIY oscilloscope on the market, was chosen as the base platform for our oscilloscope. DSO138-mini uses STM32F103C8 MCU as its main processing unit, which offers built-in 12-bit, 1 MSPS ADCs [1]. It also has all the essential functions, such as input range and DC/AC selection, voltage division and time division control, along with trigger source control. Besides an LCD display, the DSO138-mini also supports an UART/USB link so that captured waveforms can be sent to a PC for higher resolution display, data measurement, and data storage. Priced at under $40, the DSO138-mini includes a standard oscilloscope probe, which gives value among DIY oscilloscopes with its functionalities and features.

The major issues with DSO138-mini, like many other DIY types of oscilloscopes, are inadequate measurement precision and noise rejection. As will be discussed in the next few sections, DSO138-mini lacks adequate anti-aliasing filtering capability, making it susceptible to input high-frequency noises. It also has large ADC noises, possibly coupled from noisy power rails of digital circuitry inside the microcontroller, making the effective resolution less than 9 bits even in its own self-test mode when there is no external input signal. These two problems of inadequate anti-aliasing filtering capability and large ADC noises make the DSO138-mini unsuitable as a precision signal measurement device in high school labs.

The new oscilloscope

To fix these issues, a new anti-aliasing filter and a digital filter (1st-order IIR) are implemented on the DSO138-mini platform. The experiment results (Part 2 of this DI) show that the new oscilloscope has a significant improvement over the original DSO138-mini in terms of input noise rejection and ADC noise reduction and is capable of precision signal measurement up to 10 bits (or 1/1000).

The block diagram of the oscilloscope is illustrated in Figure 1. The analog input is first processed by the signal conditioning circuit for input range setup and voltage division selection. The ADC in the MCU converts the analog input signal into digital code. The scope control program of MCU processes and formats the digital data, and sends it over to LCD display, and/or to PC via UART/USB link. Note that the blocks in the blue color, namely the anti-aliasing filter, and the digital post-processing, are the new functions that were added to the DSO138-mini, to bring up its measurement precision to above 10 bits.   

Figure 1 Block diagram of the modified DSO138-mini DIY oscilloscope platform where the blue blocks are the new functioned added.

Analog signal processing Anti-aliasing filter introduction

Digital oscilloscopes rely on ADCs to convert the analog input into digital code for further signal processing and storage, one important phenomenon that could damage the conversion precision is called aliasing. Shannon theorem states that if the highest input frequency exceeds one-half of the ADC sampling frequency, or Nyquist frequency, aliasing will happen; meaning that the high frequency components will fold back to the signal bandwidth and contaminate the input signal, Figure 2

Figure 2 When the highest input frequency exceeds the ADC sampling frequency (fs), aliasing will occur, and the sampled frequency will not represent the original input signal.

In theory, ADC sampling frequency should be set two times above the input signal bandwidth to avoid aliasing. In practice, this is usually not sufficient since analog input signals often contain high frequency noises coupled from noisy parts of the system, e.g., the power supply, and high frequency harmonic tones generated by the signal sources.

In high precision applications, anti-aliasing filters of low-pass type are used to filter away these high frequency components. Ideally, a high-order low-pass filter (LPF) with a sharp roll off is preferred and the cut-off frequency of the filter should be placed near the Nyquist frequency, or one half of the sampling frequency. Due to the slow roll off rate (-20 dB/dec) of low-cost 1st order LPFs, the -3dB cut-off frequency often needs to be set significantly lower than the ADC sampling frequency to be effective.

Anti-aliasing filter design

While many DIY oscilloscopes less than fifty dollars do not have any anti-aliasing filters at all, the DSO138-mini does provide limited LPF functions in its input signal conditioning circuits. Figure 3 illustrates the conceptual schematic of the analog front-end signal path of the DSO138-mini.

Figure 3 Conceptual schematic of the analog front-end signal path of DSO138-mini.

The first amplifier stage consists of input voltage division selection, LPF/frequency compensation, and a unity gain amplifier. The second stage is a non-inverting amplifier serving as a gain stage and a buffer to drive the ADC, with some attenuation adjustment capability at its input. The overall cut-off frequencies of the signal path are inadequate to effectively remove high frequency noises away from the input signal to avoid aliasing.

Table 2 summarizes the SPICE simulation results of the -3-dB cut-off frequencies at the oscilloscope’s different voltage division and attenuation configurations.

Voltage Division	Attenuation	Cut-off Frequency (-3dB)
10 mV	x1	599 kHz
	x2	598 kHz
	x5	593 kHz
0.1 V	x1	488 kHz
	x2	487 kHz
	x5	483 kHz
1 V	x1	813 kHz
	x2	805 kHz
	x5	798 kHz

Table 2 Cut-off frequencies (-3 dB) at different voltage division / attenuation configurations.

The -3dB cut-off frequencies range from about 500 kHz to 800 kHz, depending on the input range and attenuation settings. The built-in ADC of the MCU of DSO0138-mini has the highest sampling rate of 1 MSPS, and 500 KSPS or below is frequently used as the highest sampling frequency in many applications.

Apparently, these cut-off frequencies are too high for 500KSPS or even 1MSPS—they are all close to or higher than Nyquist frequency at 1MSPS. Severe aliasing and subsequent degradation in measurement precision would happen if the analog input contained high frequency noises. To resolve this problem, we need to introduce an LPF with lower cut-off frequencies.  

The right value of the cut-off frequency depends on the sampling rate or time division setup and the analog input bandwidth of the oscilloscope. Ideally, a customized anti-aliasing filter is implemented for each sampling rate/time division configuration. However, customized anti-aliasing filters will add hardware complexity and cost. In most high-school projects, we are mainly interested in the frequency from DC to audio frequency (20 kHz), with the highest sampling frequency of 500 KSPS to 1 MSPS. A cut-off (-3dB) frequency of around 100kHz is chosen for these applications.

Although the new anti-aliasing filter could be implemented at various locations in the input signal conditioning circuits, the best place is at the second amplifier stage, i.e., the ADC driver stage, so that the cut-off frequency is not affected by the input range and voltage division selections.

Figure 4 illustrates the conceptual schematic of the new anti-aliasing filter [2]. The capacitor, C_Filter, is added to the original second amplifier stage and put in parallel with the resistor, R6, forming a first-order LPF in an inverting amplifier configuration.

Figure 4 Conceptual schematic of the new first-order anti-aliasing LPF in an inverting amplifier configuration.

The -3 dB cut-off frequency is determined by the value of the C_Filter and R2 and given by the Equation 1.

Figure 5 shows the SPICE simulation results of the frequency response of the input conditioning circuits, including the newly added anti-aliasing filter, at Voltage Division of 0.1 V, Voltage Attenuation of 0 dB, and the C_Filter value of 1nF (R6 is 1.1 kΩ). The -3 dB cut-off is at 100 kHz. The filter cut-off frequency was found to be centered well around 100 kHz among all other voltage division and attenuation setups.

Figure 5 SPICE simulation results with frequency response of the input conditioning circuits, including the new anti-aliasing filter.

There is one additional benefit of C_Filter; it also lowers the output impedance of the amplifier which interfaces and drives the ADC. A lower output impedance can reduce the kick-back noise coming from the switch capacitor operation of the ADC [3].

Finally, when choosing the filter capacitor value in this type of topology, we also need to make sure that it does not cause issues of op-amp output slew rate and/or stability.

Digital signal post-processing Digital filter introduction

There are other noise sources in oscilloscopes that can damage measurement precision. Among them, noises on the ADC inside the MCU are of particular concern. This is because ADCs are sensitive to noises on their power supply rails and references. MCUs are known for their large digital switching noises and as a result, the signal-to-noise ratio (SNR) of their embedded ADCs are limited by these digital noises. The situation worsens in DIY oscilloscopes as little resources are available to be spent on reducing these digital noises.

The DSO138-mini, for example, has high frequency noises and ripples on its captured data even when the input analog signal is clean (with well-designed anti-aliasing filters). These ripples make precision measurement difficult.

Digital post-processing can be used to reduce these power supply and reference-induced noises. The ADC output digital code, or the raw data, goes through a digital LPF, with some of its high-frequency components (often noise) removed, before presenting to the display or other format of data output. The digital filter algorithms can be implemented either in MCU firmware or in PC programs when a PC is used for final display and data measurement. 

Digital filter design

DSO138-mini has two “terminals” for displaying waveforms. One is through an LCD for real-time waveform display. Because of its low resolution (320 x 240), the LCD is mainly used for bench waveform observation and monitoring. The oscilloscope also supports a UART/USB interface to transmit captured waveform data to a PC, where most precision measurements and signal analysis are performed. We therefore implement the digital post-processing program on the PC.

A first-order IIR filter is adopted for the digital signal post-processing [4]. The output and input relationship of a first order IIR filter is as follows:

The flow chart of the first-order IIR filter is shown in Figure 6.

Figure 6 Flow chart of the first-order IIR filter. IIR filters are widely used in various applications thanks to their simplicity and effectiveness.

The frequency response of the first-order IIR filter is shown in Figure 7. The pass-band width is decided by the coefficient, α. The smaller the α, the more attenuation to high frequency noises, with the cost of a smaller passband. Three different α values (0.5, 0.25, and 0.125) were plotted to compare their performances.

Figure 7 The frequency response of the IIR filter with three different α values: 0.5, 0.25, and 0.125.

The trade-off is between noise attenuation and useful signal bandwidth. Smaller α values can reject a wider band of noises but result in a smaller analog bandwidth.

For most high school projects, the input signal is from DC up to audio frequency (20 kHz). Therefore, we choose the value of α to be 0.25 as our default value for these purposes, with a -3 dB bandwidth of 23 kHz when ADC samples at 500 KSPS. The value of α is made programmable so that users can easily tune it for different applications.

Digital signal post-processing, if used properly, can significantly reduce the noises and ripples on oscilloscopes and improve measurement accuracy. We will demonstrate the effect of digital post-processing in Part 2.

Tommy Liu is currently a junior at Monta Vista High School (MVHS) with a passion for electronics. A dedicated hobbyist since middle school, Tommy has designed and built various projects ranging from FM radios to simple oscilloscopes and signal generators for school use. He aims to pursue Electrical Engineering in college and aspires to become a professional engineer, continuing his exploration in the field of electronics.

Related Content

• Designing antialias filters for ADCs
• Delta-sigma antialiasing filter with a mode-rejection circuit
• Three alternatives to your aliasing problems
• FIR and IIR digital filter design guide
• Fixed-point-IIR-filter challenges
• How to create fixed- and floating-point IIR filters for FPGAs

References

1. ST Microelectronics. (n.d.). Datasheet of STM32F103x8, Medium-density performance line Arm®-based 32-bit MCU with 64 or 128 KB Flash, USB, CAN, 7 timers, 2 ADCs, 9 com. interfaces. https://www.st.com/resource/en/datasheet/stm32f103c8.pdf
2. Franco, S. (1998). Design with operational amplifiers and Analog Integrated Circuits. McGraw Hill.
3. Reeder, R. (2011, June 20). Kicking back at high-speed, unbuffered adcs. Electronic Design. https://www.electronicdesign.com/technologies/analog/article/21798279/kicking-back-at- high-speed-unbuffered-adcs
4. of EECS, University of Michigan, Ann Arbor. (2002, August 2). IIR Filters IV: Case Study of IIR Filters, https://www.eecs.umich.edu/courses/eecs206/archive/spring02/notes.dir/iir4.pdf

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