Generating Airborne Ultrasonic Amplitude Patterns Using an Open Hardware Phased Array

Holographic methods from optics can be adapted to acoustics for enabling novel applications in particle manipulation or patterning by generating dynamic custom-tailored acoustic fields. Here, we present three contributions towards making the field of acoustic holography more widespread. Firstly, we introduce an iterative algorithm that accurately calculates the amplitudes and phases of an array of ultrasound emitters in order to create a target amplitude field in mid-air. Secondly, we use the algorithm to analyse the impact of spatial, amplitude and phase emission resolution on the resulting acoustic field, thus providing engineering insights towards array design. For example, we show an onset of diminishing returns for smaller than a quarter-wavelength sized emitters and a phase and amplitude resolution of eight and four divisions per period, respectively. Lastly, we present a hardware platform for the generation of acoustic holograms. The array is integrated in a single board composed of 256 emitters operating at 40 kHz. We hope that the results and procedures described within this paper enable researchers to build their own ultrasonic arrays and explore novel applications of ultrasonic holograms.

Coping with Motion Artifacts by Analog Front-End ECG Microchips under Variable Digital Resolution and Gain

The development of portable ECG technology has found growing markets, from wearable ECG sensors to ambulatory ECG recorders, encountering challenges of moderately complex to tightly regulated devices. This study investigated how a typical 0.5–40 Hz bandwidth ECG is affected by motion artifact when using analog front-end (AFE) integrated circuits such as the AD823X family. It is known that the typical amplitude resolution of current mobile health ECG devices is 10–12 bits, and sometimes 16-bits, which is enough for monitoring but might be insufficient to identify the small potential amplitudes useful in diagnoses. The interest now is on the interplay of how a digital resolution choice and variable gain can cope with motion artifacts inherent in mobile health devices. With our methodology for a rapid prototyping of an ECG device, and using the AFE AD8232 and Bluetooth communication, a specific cardiac monitor ECG configuration was evaluated under two microcontroller systems of different resolution: a generic Arduino Nano board which featured a 10-bit analog-to-digital converter (ADC) and the 24-bit ADC of Silicon Labs C8051F350 board. The ECG cardiac monitor setup, recommended by Analog Devices, featuring two gain values under these two different microcontroller systems, was explored as to its ability to solve motion artifact problems.

Measurement system and dataset for in-depth analysis of appliance energy consumption in industrial environment

To support a rational and efficient use of electrical energy in residential and industrial environments, Non-Intrusive Load Monitoring (NILM) provides several techniques to identify state and power consumption profiles of connected appliances. Design requirements for such systems include a low hardware and installations costs for residential, reliability and high-availability for industrial purposes, while keeping invasive interventions into the electrical infrastructure to a minimum. This work introduces a reference hardware setup that allows an in depth analysis of electrical energy consumption in industrial environments. To identify appliances and their consumption profile, appropriate identification algorithms are developed by the NILM community. To enable an evaluation of these algorithms on industrial appliances, we introduce the Laboratory-measured IndustriaL Appliance Characteristics (LILAC) dataset: 1302 measurements from one, two, and three concurrently running appliances of 15 appliance types, measured with the introduced testbed. To allow in-depth appliance consumption analysis, measurements were carried out with a sampling rate of 50 kHz and 16-bit amplitude resolution for voltage and current signals. We show in experiments that signal signatures, contained in the measurement data, allows one to distinguish the single measured electrical appliances with a baseline machine learning approach of nearly 100 % accuracy.

Bitstream radar waveforms for generic single-chip radar

Bitstreams, square wave digital signals, enable flexible radar implementations in modern digital technology. By using bitstreams in place of analog sinusoidal waveforms, we can realize continuous-wave (CW), stepped-frequency CW, frequency-modulated CW, or even pseudo random noise-sequence and pulsed radars, all with a single bit of amplitude resolution. The building blocks are a programable waveform generator, a sweep threshold quantizer, digital delay, and a digital XOR gate as a mixer. This gives us a novel, almost fully digital (requiring only a comparator) system, as previously proposed and which is extended here. The flexibility of the transmitter allows for easy switching between waveforms and the bitstream signal can be processed with single-bit digital gates. Single-bit signals allows for exploration of novel continuous time non-clocked digital implementations to maximize speed and energy efficiency. Mixing frequencies with a digital XOR gate creates harmonics, which are explored for multiple solutions utilizing digital delay. Analytical as well as simulation results are presented. Initial measurements from a 90 nm CMOS chip is provided for the transmitter and the full system, proving the feasibility of a digital future in radar.

A programmable compact wide-band RF feed network

The design and fabrication of a wide-band programmable radio frequency (RF) feed network is proposed. It is designed to cover a wide band from 2.5 to 6 GHz over two separate branches. The feed network is simulated and fabricated on an FR-4 substrate with 0.8 mm thickness. Good matching between simulation and measurement results is achieved. The measured amplitude resolution was 0.5 dB with a maximum error of 0.22 dB. The measured phase resolution was approximately 5.6° with 1° maximum error. This design is a generic one that can be used in any kind of RF or antenna systems.