Sensing the Environment as with Human Senses

High-performance sensors are the drivers of smart devices

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Author: Rosina Kreutzer, Director Business Development, Infineon Technologies AG

What had long been considered as a vision of the future is now a reality – devices can detect their surroundings as if they were human senses and interact with them. Sensors close the gap to the digital world. Combined with appropriate software, smart devices and robots, for example, can see, hear, smell or feel and above all “intuitively understand” their environment, thereby simplifying our lives. The decisive factor here is the interpretation and linking of information from different sensors.

Inspired by human nature, Infineon takes a holistic approach and combines a variety of sensors. This results in smart systems that make interaction between man and machine or device much easier, but also which reliably process the situation information obtained. The Infineon XENSIVTM sensor portfolio includes 3D/ToF image sensors, radar chips, MEMS microphones, pressure and gas sensors. These smart sensors benefit a wide range of applications – from voice recognition, smart homes and smart cities, augmented reality, gesture recognition, biometrics, robotics, automated/autonomous driving, drones/multicopters, lighting controls to smart home appliances and alarm systems.

Figure 1: Smart sensors detect the environment as with human senses and connect the real world with the digital world.

Seeing in 3D

Whether augmented reality, facial recognition or complex image effects, the mobile device market in particular has massively increased the demand for “seeing in 3D” in various fields of application. A special and at the same time efficient technology for this is the runtime technology Time-of-Flight (ToF). It measures the time of a beam of light, similar to a bat’s system for sound measurement, and enables highly accurate 3D reproductions of an image. Infineon has developed a REAL3 image sensor in the form of a miniaturised 3D single chip specifically for the requirements of the mobile device market. The ToF sensor enables augmented reality applications, secure user authentication via face and hand recognition, password-free confirmation of payments, optimised morphing and photo effects or scanning of rooms. Compared to other 3D sensor principles, such as the stereoscopic or structured light technology, ToF delivers convincing performance, miniaturisation and power consumption for battery-powered devices.

The 4.6 mm x 5 mm image sensor delivers approximately 150,000 pixels (HVGA, half variable gain amplifier). The high-performance pixel array is tuned to infrared light with a wavelength of 940 nm and achieves excellent outdoor performance, especially in strong sunlight. This is made possible by the patented SBI circuit in each individual pixel (SBI = suppression of background illumination).

3400Figure 2: The Real 3 3D image sensor measuring only 4.6 mm x 5 mm is virtually a miniature camera.

Precise view with radar

Radar has evolved from a complex cutting-edge technology to a solution that is becoming more and more important in industry and the consumer market. It is increasingly being used in robotics, cars and smart homes and supports new technologies that work with an intuitive human-machine interface. Radar sensors make it easier to locate targets in three-dimensional space and can be used to detect vital functions, classify materials or movements, or for gesture control. Compared to passive IR technologies, radar offers many advantages in “seeing” and motion detection. This includes higher accuracy and the precise detection of the smallest movements, so-called micromotions. The Infineon radar sensor portfolio of the XENSIVTM family ranges from the world’s smallest 24 GHz MMIC (monolithic microwave integrated circuit) to the highly integrated 60 GHz transceiver. This chip features an integrated antenna and allows “seeing” at the highest level, both under normal conditions, but more specifically under extreme conditions such as darkness, fog and dust, or through materials.

Robust motion detection

Smartwatches, wearables or smartphones use air pressure sensors to accurately detect differences in altitude, vertical speeds and movements. In addition, these sensors can monitor air flows in vacuum cleaners, air conditioners and extractor hoods. Applications that benefit from these exact and robust pressure sensors are also increasingly found in medicine, for example in smart inhalation devices, breathing masks, fall detection or non-invasive blood pressure measurement.

The Infineon DPS368 pressure sensor is ideal for these applications because it saves up to 80 % space compared to other waterproof pressure sensors, offers an accuracy of ± 2 cm and requires up to 50 % less energy than piezoresistive technology. The digital sensor, which measures atmospheric air pressure, is resistant to water, humidity and dust (IP57). A gel protects the contact points and membranes so that they can withstand the pressure at a water depth of 50 m for one hour.

Figure 3: The robust DPS368 air pressure sensor precisely detects minimal differences in altitude, vertical speeds and movements.

The pressure sensor element of the DPS368 operates with a capacitive measuring principle that guarantees high accuracy even with temperature changes. The sensor integrates both air pressure and temperature measurement in an extremely compact 8-pin land grid array (LGA) package measuring only 2.0 mm × 2.5 mm × 1.1 mm. The device has an accuracy of up to ± 0.002 hPa (± 2 cm), can measure air pressures between 300 hPa and 1200 hPa at temperatures from -40 to 85 °C, and has a pressure-temperature sensitivity of less than 0.5 Pa/K. The sensor is also able to detect individual steps, body movements or gestures. The high measuring frequency (up to 200 Hz) and the fast readout enable rapid feedback from the sensor.

Hearing and understanding without background noise

Whether for telephone calls or web conferences, for active noise cancellation (ANC) in headphones when travelling or for operating a device with your voice, the “artificial sense of hearing” with microphones has become an integral part of everyday life.

First-class MEMS microphones and state-of-the-art audio processing are key elements in meeting consumers’ growing demands on these devices. Voice recognition systems that also understand us in the next room or audio recordings that sound as if you had been there. This is made possible by MEMS microphones with the lowest signal to noise ratio (SNR) and a wide dynamic range.

Infineon has already set new standards for digital MEMS microphones with its XENSIVTM MEMS microphone IM69D130. Together with its partners in the field of audio signal processing and software, Infineon offers high-end reference solutions that can be quickly deployed in a wide variety of applications.

The latest generation of MEMS microphones features a specially encapsulated dual backplate technology and offers enhanced features with even greater performance and robustness. The “encapsulation” of the condenser enables virtually noise-free recording of audio signals. The microphone also offers low self-noise (high signal-to-noise ratio, SNR), wide dynamic range, low distortion, and a high acoustic overload point (AOP). It is precisely these specifications that enable extremely precise voice recognition and an increase in SNR to 75 dB for an AOP of up to 140 dBSPL.

Figure 4: Infineon’s new generation of MEMS microphones with “encapsulation” of the condenser enables virtually noise-free recording of audio signals.

Transparent air quality

One indicator of poor air quality is the concentration of CO2. Current solutions for monitoring this odourless and colourless gas are bulky and pricey or not accurate enough for broad application. Infineon has developed a disruptive CO2 sensor technology based on photoacoustic spectroscopy (PAS). The XENSIVTM PAS CO2 uses a MEMS microphone with a high SNR as a detector, thus enabling the implementation of an extremely compact CO2 sensor with unprecedented small dimensions. It is therefore ideal for use in smart home applications and building automation, such as on-demand ventilation, as well as for various IoT devices for controlling indoor air quality, air purifiers, thermostats, weather stations and personal assistants.