Page 17 - EE Times Europe Magazine | June2020

EE|Times EUROPE 17

The Growing Importance of Innovative MEMS Microphones

AOP is key for undistorted concert music recordings
and echo cancellation when a microphone is placed
close to a speaker. Good phase matching is important
for microphone arrays and improving the performance
of beamforming algorithms. In other words, if you are
building a system that has to perform beamforming,
pick up audio from a distance, and cancel echoes,
you need an array of microphones with all of the
above-mentioned features.
In addition to providing all of the audio parame-
ters for the use cases mentioned above, microphones
should be robust against water and dust. They must
also work within their specifications under variations
in temperature, humidity, pressure, and other environ-
mental factors. In an ideal world, microphones would
not generate any self-noise at all but would emulate the
human ear, which has an extremely low noise floor. In
reality, however, there are technical limitations defined
by physics. There are typically four noise contributors
in MEMS microphone systems: the MEMS itself, the
Figure 3: FluSense is an innovative concept for monitoring influenza trends. It ASIC, the package, and its sound port. The highest noise
combines a microphone array with a camera to analyze coughing and patient contributor for state-of-the-art microphones used in
counts. (Image: University of Massachusetts) smartphones is the MEMS component. Infineon has
improved the MEMS component, pushing the boundar-
ies of MEMS microphone performance beyond even the
microphones contains more information and less self-noise, which current best-in-class dual-backplate technology. The company’s efforts
makes the subsequent processing on the edge processor and in the here culminated in the development of Infineon’s innovative, patented
cloud more efficient. Better raw audio data input results in a higher sealed dual-membrane (SDM) MEMS technology.
hit rate, lower false acceptance instances, and, subsequently, a lower
error rate for system wakeup. In short, having better microphones in A LOOK INSIDE A MEMS MICROPHONE
your smart speaker means that the next time you ask it a question, you Before explaining how the new SDM works, it makes sense to take a
won’t have to repeat yourself. quick look at the inside of a MEMS microphone and see what challenges
In general, each acoustic parameter has its own importance and the different components have to overcome to deliver the best perfor-
enables certain specific use cases (Figure 4). High SNR, for example, is mance. A typical design combines a MEMS sensor and an ASIC. MEMS
important for picking up distant and whispered voices in smart speak- microphones extract audio pressure changes as electrical signals. The
ers, video conferencing devices, and similar far-field applications. A ASIC then processes these signals either in differential analog or in
study conducted by Infineon showed that higher-SNR microphones can digital format at the output. The first challenge is handling the pressure
capture whisper audio 40% better than standard microphones. High levels of loud sounds, as they produce large mechanical movements in

Figure 4: High-performance microphones are characterized by a number of different parameters.

www.eetimes.eu | JUNE 2020