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Rohde & Schwarz India extended a warm welcome to His Excellency Dr. Philipp Ackermann, Ambassador of the Federal Republic of Germany to India, during his visit to the corporate facility located in New Delhi. This significant event signifies a notable advancement in the mutually beneficial relationship between Germany and India. The visit is anticipated to foster increased collaboration in the spheres of advanced technology and innovation, further enhancing the partnership between the two nations.

The Ambassador’s visit aimed to throw light on Rohde & Schwarz’s growing presence over the last three decades, along with highlighting the company’s expanding research and development (R&D) capabilities, planned investments in infrastructure, and enhanced technological competencies, which are also in line with the ‘Make in India’ initiative.

Dr Ackermann was given an overview of the company’s state-of-the-art R&D test laboratories, its work in niche electronics technology areas, and its plans for future innovation and growth during his visit, where he also interacted with the engineering and leadership teams to understand their technical capabilities and long-term vision.

His Excellency Dr Philipp Ackermann remarked:

“It is encouraging to see German technology companies like Rohde & Schwarz making long-term commitments in India. The company’s focus on R&D, local competence development, and high-quality engineering reflects the strong foundation of Indo-German cooperation in technology and innovation.”

Speaking on the occasion, Yatish Mohan, Managing Director, Rohde & Schwarz India, stated: “We are deeply honoured to host His Excellency Dr Ackermann at our facility. This visit underscores our commitment to advancing technological excellence in India and reflects the shared vision of fostering stronger economic and innovation ties between our two nations.”

Rohde & Schwarz India is committed to deepening Indo-German industrial collaboration, driving innovation through local R&D initiatives, and contributing to the nation’s self-reliant manufacturing ecosystem.

The post Indo-German Tech Cooperation Strengthens with German Ambassador’s visit to R&S India appeared first on ELE Times.

Stephen Woodward’s “Ignoring the regulator’s reference” Design Ideas (DI) (see Figure 1) is an excellent, working example of how to include a circuit in the feedback loop of an op amp to support the stabilization of the circuit’s operating point. This is also previously seen in “Improve the accuracy of programmable LM317 and LM337-based power sources” and numerous other places[1][2][3]). I’ll refer to his DI as “the DI” in subsequent text.

Figure 1 The DI’s Figure 1 schematic has been redrawn to emphasize the positioning of the U1 regulator in the A1 op amp’s feedback loop. The Vdac signal controls U1 while ignoring its internal reference voltage.

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

A few minor tweaks optimize this circuit’s dynamic performance and leave the design equations and comments in the DI unchanged. Let’s consider the case in which U1’s reference voltage is 0.6 V, Vdac varies from 0 to 3 V, and Vo varies from 5 to 0 V.

The DI tells us that in this case, R1a is not populated and that R1b is 150k. It also mentions driving Figure 1’s Vdac from the DACout signal of Figure 2, also found in “A nice, simple, and reasonably accurate PWM-driven 16-bit DAC.”

Figure 2 Each PWM input is an 8-bit DAC. VREF should be at least 3.0 V to support the SN74AC04 output resistances calculable from its datasheet. Ca and C1 – C3 are COG/NPO.

The Figure 2 PWMs could produce a large step change, causing DACout and therefore Vdac to quickly change from 0 to 3 V.

Figure 3 shows how Vo and the output of A1 react to this while driving a hypothetical U1, which is capable of producing an anomaly-free [4] 0-volt output.

Figure 3 Vo and A1’s output from Figure 1 react to a step change in Vdac.

Even though Vo eventually does what it is supposed to, there are several things not to like about these waveforms. Vo exhibits an overshoot and would manifest an undershoot if it didn’t clip at the negative rail (ground). The output of A1 also exhibits clipping and overshooting. Why are these things happening?

The answer is that the current flowing through R5 also flows through R3, causing an immediate change in the output voltage of A1. That change causes a proportional current to flow through R4. However, the presence of C2 prevents an immediate change in Vo and delays compensatory feedback from arriving at A1’s non-inverting input. How can this delay be avoided?

Shorting out R3 makes matters worse. The solution is to remove C2, speeding up the ameliorative feedback. Figure 4 shows the results.

Figure 4 With C2 eliminated, so are the clipping and the over- and undershoots. The A1 output moves only a few millivolts because of the large DC gain of the regulator, and because it is no longer necessary to charge C2 through R4 in response to an input change.

Vo now settles to ½ LSbit of a 16-bit source in 2.5 ms. Changing C3 to 510 pF (10% COG/NPO) reduces that time to 1.4 ms. Smaller values of C3 provide little further advantage.

The Vo-to-VSENSE feedback becomes mostly resistive above 0.159 / (R · C3) Hz, where:

R = R3 + R5 · R1a / (R5 + R1a)

In this case, that’s 1600 Hz, well below the unity gain frequency of pretty much any regulator, and so there should be no stability issues for the overall circuit. Note that A1’s output remains almost exactly equal to the regulator’s reference voltage. This, and the freedom to choose the R5/R1a and R2/R1b ratios, leaves open the option of using an op amp whose inputs and output needn’t approach its positive supply rail.

The (original) DI is a solid design that obtains some dynamic performance benefits from reducing the value of one capacitor and eliminating another.

Related Content

• Ignoring the regulator’s reference
• Improve the accuracy of programmable LM317 and LM337-based power sources
• A nice, simple, and reasonably accurate PWM-driven 16-bit DAC
• Enabling a variable output regulator to produce 0 volts? Caveat, designer!

References

1. https://en.wikipedia.org/wiki/Current_mirror#Feedback-assisted_current_mirror
2. https://www.onsemi.com/pdf/datasheet/sa571-d.pdf see section on compandor
3. https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/14/CircuitCookbook_2D00_OpAmps.pdf see triangle wave generator, page 90
4. Enabling a variable output regulator to produce 0 volts? Caveat, designer!

The post Ignoring the regulator’s reference redux appeared first on EDN.

EDN Design Ideas (DI) published a design of mine in May of 2025 for a passive two-way current mirror topology that, in analogy to optical two-way mirrors, can reflect or transmit. 

That design comprises just two BJTs and one diode. But while its simplicity is nice, its symmetry might not be. That is to say, not precise enough for some applications.

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

Fortunately, as often happens when the precision of an analog circuit falls short, and the required performance can’t suffer compromise, a fix can consist of adding an RRIO op amp. Then, if we substitute two accurately matched current-sensing resistors and a single MOSFET for the BJTs, the result is the active two-way current mirror (ATWCM) as shown in Figure 1.

Figure 1 The active two-way current sink/source mirror. The input current source is mirrored as a sink current when D1 is forward biased, and transmitted as a source current when D1 is reverse biased.

Figure 2 shows how the ATWCM operates when D1 is forward-biased, placing it in mirror mode.

Figure 2 ATWCM in mirror mode, I1 sink current generates Vr, forcing A1 to coax Q1 to mirror I2 = I1.

The operation of the ATWCM in mirror mode couldn’t be more straightforward. Vr = I1R wired to A1’s noninverting input forces it to drive Q1 to conduct I2 such that I2R = I1R. 

Therefore, if the resistors are equal, A1’s accuracy-limiting parameters (offset voltage, gain-bandwidth, bias and offset currents, etc.) are adequately small, and Q1 does not saturate, I1 = I2 just as precisely as you like.

Okay, so I lied.  Actually, the operation of the ATWCM in transmission mode is even simpler, as Figure 3 shows.

Figure 3 ATWCM in transmission mode. A reverse-biased D1 means I1 has nowhere to go except through the resistors and (saturated and inverted) Q1, where it is transmitted back out as I2.

I1 flowing through the 2R net resistance forces A1 to rail positive, saturating Q1 and providing a path back to the I2 pin. Since Q1 is biased inverted, its body diode will close the circuit from I1 to I2 until A1 takes over. A1 has nothing to do but act as a comparator.

Flip D1 and substitute a PFET for Q1, and of course, a source/sink will result, shown in Figure 4.

Figure 4 Source/sink two-way mirror with a D1 flipped the opposite direction, and Q1 replaced with a PFET. 

Figure 5 shows the circuit in Figure 4 running a symmetrical rail-to-rail tri-wave and square-wave output multivibrator.

Figure 5 Accurately symmetrical tri-wave and square-wave result from inherent A1Q2 two-way mirror symmetry.

Stephen Woodward’s relationship with EDN’s DI column goes back quite a long way. Over 100 submissions have been accepted since his first contribution back in 1974.

 Related Content

• A two-way mirror—current mirror that is
• Active current mirror
• A current mirror reduces Early effect
• A two-way Wilson current mirror

The post Active two-way current mirror appeared first on EDN.

Designers are looking to reduce the cost of drone systems for a wide range of applications but still need to provide accurate positioning data. This however is not as easy is it might appear.

There are several satellite positioning systems, from the U.S.-backed GPS and European Galileo to NavIC in India and Beidou in China, providing data down to the meter. However, these need to be augmented by an inertial measurement unit (IMU) that provides more accurate positioning data that is vital.

Figure 1 An IMU is vital for the precision control of the drone and peripherals like gimbal that keeps the camera steady. Source: Epson

An IMU is typically a sensor that can measure movement in six directions, along with an accelerometer to detect the amount of movement. The data is then used by the developer of an inertial measurement system (IMS) with custom algorithms, often with machine learning, combined with the satellite data and other data from the drone system.

The IMU is vital for the precision control of the drone and peripherals such as the gimbal that keeps the camera steady, providing accurate positioning data and compensating for the vibration of the drone. This stability can be implemented in a number of ways with a variety of sensors, but providing accurate information with low noise and high stability for as long as possible has often meant the sensor is expensive with high power consumption.

This is increasingly important for medium altitude long endurance (MALE) drones. These aircraft are designed for long flights at altitudes of between 10,000 and 30,000 feet, and can stay airborne for extended periods, sometimes over 24 hours. They are commonly used for military surveillance, intelligence gathering, and reconnaissance missions through wide coverage.

These MALE drones need a stable camera system that is reliable and stable in operation and a wide range of temperatures, providing accurate tagging of the position of any data captured.

One way to deliver a highly accurate IMU with lower cost is to use a piezoelectric quartz crystal. This is well established technology where an oscillating field is applied across the crystal and changes in motion are picked up with differential contacts across the crystal.

For a highly stable IMU for a MALE drone, three crystals are used, one for each axis, stimulated at different frequencies in the kilohertz range to avoid crosstalk. The differential output cancels out noise in the crystal and the effect of vibrations.

Precision engineering of piezoelectric crystals for high-stability IMUs

Using a crystal method provides data with low noise, high stability, and low variability. The highly linear response of the piezoelectric crystal enables high-precision measurement of various kinds of movement over a wide range from slow to fast, allowing the IMU to be used in a broad array of applications.

An end-to-end development process allows the design of each crystal to be optimized for the frequencies used for the navigation application along with the differential contacts. These are all optimized with the packaging and assembly to provide the highly linear performance that remains stable over the lifetime of the sensor.

It uses 25 years of experience with wet etch lithography for the sensors across dozens of patents. That produces yields in the high nineties with average bias variations, down to 0.5% variant from unit to unit.

An initial cut angle on the quartz crystal achieves the frequency balance for the wafer, then the wet etch lithography is applied to the wafer to create a four-point suspended cantilever structure that is 2-mm long. Indentations are etched into the structure for the wire bonds to the outside world.

The four-point structure is a double tuning fork with detection tines and two larger drive tines in the centre. The differential output cancels out spurious noise or other signals.

This is simpler to make than micromachined MEMS structures and provides more long-term stability and less variability across the devices.

The differential structure and low crosstalk allow three devices to be mounted closely together without interfering with each other, which helps to reduce the size of the IMU. A low pass filter helps to reduce any risk of crosstalk.

The six-axis crystal sensor is then combined with an accelerometer for the IMU. For the MALE drone gimbal applications, this accelerometer must have a high dynamic range to handle the speed and vibration effects of operation in the air. The linearity advantage of using a piezoelectric crystal provides accuracy for sensing the rotation of the sensor and does not degrade with higher speeds.

Figure 2 Piezoelectric crystals bolster precision and stability in IMUs. Source: Epson

This commercial accelerometer is optimized to provide the higher dynamic range and sits alongside a low power microcontroller and temperature sensors, which are not common in low-cost IMUs currently used by drone makers.

The microcontroller technology has been developed for industrial sensors over many years and reduces the power consumption of peripherals while maintaining high performance.

The microcontroller is used to provide several types of compensation, including temperature and aging, and so provides a simple, stable, and high-quality output for the IMU maker. Quartz also provides very predictable operation across a wide temperature range from -40 ⁰C to +85 ⁰C, so the compensation on the microcontroller is sufficient and more compensation is not required in the IMU, reducing the compute requirements.

All of this is also vital for the calibration procedure. Ensuring that the IMU can be easily calibrated is key to keeping the cost down and comes from the inherent stability of the crystal.

Calibration-safe mounting

The mounting technology is also key for the calibration and stability of the sensor. A part that uses surface mount technology (SMT), such as a reflow oven, for mounting to a board, which is exposed to high temperatures that can disrupt the calibration and alter the lifetime of the part in unexpected ways.

Instead, a module with a connector is used, so the 1-in (25 x 25 x 12 mm) part can be soldered to the printed circuit board (PCB). This avoids the need to use the reflow assembly for surface mount devices where the PCB passes through an oven, which can upset the calibration of the sensor.

Space-grade IMU design

A higher performance variant of the IMU has been developed for space applications. Alongside the quartz crystal sensor, a higher performance accelerometer developed in-house is used in the IMU. The quartz sensor is inherently impervious to radiation in low and medium earth orbits and is coupled with a microcontroller that handles the temperature compensation, a key factor for operating in orbits that vary between the cold of the night and the heat of the sun.

The sensor is mounted in a hermetically sealed ceramic package that is backfilled with helium to provide higher levels of sensitivity and reliability than the earth-bound version. This makes the quartz-based sensor suitable for a wide range of space applications.

Next-generation IMU development

The next generation of etch technology being explored now promises to enable a noise level 10 times lower than today with improved temperature stability. These process improvements enable cleaner edges on the cantilever structure to enhance the overall stability of the sensor.

Achieving precise and reliable drone positioning requires the integration of advanced IMUs with satellite data. The use of piezoelectric quartz crystals in IMUs for drone systems offers significant benefits, including low noise, high stability, and reduced costs, while commercial accelerometers and optimized microcontrollers further enhance performance and minimize power consumption.

Mounting and calibration procedures ensure long-term accuracy and reliability to provide stable and power-efficient control for a broad range of systems. All of this is possible through the end-to-end expertise in developing quartz crystals, and designing and implementing the sensor devices, from the etch technology to the mounting capabilities.

David Gaber is group product manager at Epson.

Related Content

• Exploring ceramic resonators and filters
• Drone design: An electronics designer’s point of view
• How to design an ESC module for drone motor control
• Keep your drone flying high with the right circuit protection design
• ST Launches AI-Enabled IMU for Activity Tracking and High-Impact Sensing

The post Aiding drone navigation with crystal sensing appeared first on EDN.