Acoustic-electric Channels Research Articles

An Optimal Design Method for Improving the Efficiency of Ultrasonic Wireless Power Transmission during Communication.

Due to the excellent directivity, strong penetrability, and no electromagnetic shielding effect, ultrasonic waves have good potential for wireless energy transmission and information transfer inside and outside of sealed metal devices. However, traditional ultrasonic based energy transmission methods usually result in considerable energy consumption because of the impedance mismatch during the impedance modulation of the communication. This paper presents an optimal design method for efficient energy transfer during ultrasonic communication. The channel equivalent circuit model is established by only using the acoustic-electric channel scattering parameters. According to the equivalent circuit model, the channel impedance matches with a weak mismatch state is performed during the communication. In this way, the impedance modulation effect is ensured with a lower decrease in the energy transmission efficiency. Finally, the simultaneous energy transmission and impedance modulation are carried out through the 11 mm thick 304 stainless steel plate. The transmission power is 37.86 W with a transmission efficiency of 45.75%, and the modulation rate is 10 Kbps. Compared with the traditional methods, our proposed energy transmission efficiency is increased by 17.62%. The results verify the proposed method’s effectiveness and the high accuracy of the model. The proposed method has great engineering applications and broad prospects in condition monitoring of metallic environments.

The Modeling Framework for Through-Metal-Wall Ultrasonic Power Transmission Channels Based on Piezoelectric Transducers

The investigation of the wireless ultrasonic energy and signal transmission through metal barrier into hermitical metallic structures has become an interesting field of research. The most often constructed acoustic-electric ultrasonic power transmission channels are based on piezoelectric transducers. Effective modeling methods with accuracy are essential to the performance prediction and optimal design of such channels. Up to now, there exists a variety of modeling methods including theoretical analytical method, equivalent circuit method, two-port network method, and finite element modeling method. However there is a little chaos about how to choose an appropriate modeling method among them. There is also a lack of a systematic modeling framework presented involving principles, advantages, disadvantages, and constraint conditions of these methods. In this review, a common modeling framework for through-metal-wall acoustic-electric channels based on piezoelectric transducers is presented. The principles of the major modeling methods are introduced and the adoptability and constraints of each method are discussed. For each modeling method, simulation and or experimental results are also presented to validate the accuracy of the corresponding modeling method.

High-Rate Ultrasonic Through-Wall Communications Using MIMO-OFDM

This paper investigates methods to achieve high-rate data transmission through metallic barriers using ultrasound. Multiple-input-multiple-output-orthogonal frequency division multiplexing (MIMO-OFDM) is employed in conjunction with interference mitigation techniques to reduce throughput-limiting crosstalk. Several crosstalk mitigation strategies are investigated and their theoretical and practical bit-loaded data rates are determined for the general case of A transmitters and A receivers (A×A MIMO). A physical MIMO acoustic-electric channel array is formed using a 40 mm (1.575 in) thick steel barrier with seven pairs of 4 MHz nominal resonant frequency piezoelectric disk transducers, each with 10 mm (0.394 in) diameter. To investigate the effects of crosstalk, the transducers are closely spaced, and each transmitter-receiver pair is coaxially aligned on opposing sides of the metallic barrier. It is shown that, with the use of crosstalk mitigation techniques, the aggregate multichannel theoretical capacity performance scales linearly with the number of channels. This paper also investigates the use of novel power allocation techniques in a MIMO-OFDM acoustic-electric channel, which show significant throughput performance gains over conventional bit-loading and greedy bit-filling techniques. Finally, this paper presents a study on the effects of transducer misalignment on the multichannel theoretical capacity and achievable data transmission rates using bit-loading techniques.

Low-power, low-rate ultrasonic communications system transmitting axially along a cylindrical pipe using transverse waves.

Acoustic-electric channels have been used in the recent past to send power and data through thin metallic barriers. Acoustic-electric channels formed along a structure which are highly attenuative and nonreverberant could have potential applications in aerospace, nuclear, and oil industries, among others. This work considers data transmission along the length of a cylindrical pipe both when in air and when filled and immersed in water using shear waves of transverse polarity. To combat the effects of frequency selectivity and to address the available power constraints, a simple modulation scheme using noncoherent demodulation is employed for data transmission: chirp-on-off keying (Chirp-OOK). The wideband nature of the chirp waveform provides resilience against nulls in the channel response while making it possible to implement a simple noncoherent energy detector. Monte Carlo simulation results using measured channel responses suggest that the bit error rate performance of the scheme matches quite closely with the theoretical results. The energy detector performance is independent of the type of the channel used as long as intersymbol-interference is negligible and same received Eb/N0 is maintained. A low-power prototype hardware system was implemented using microcontrollers, commercial ICs, and custom circuits. Successful data transmission was achieved across the 4.8 m length of pipe (in air and water) for a data rate of 100 bps using approximately 5 mW of transmit power.

A full-duplex ultrasonic through-wall communication and power delivery system

This paper presents a method for two-way ultrasonic communication and power delivery through thick metallic enclosures without physical penetration. Acoustic-electric channels are implemented using a pair of coaxially aligned piezoelectric transducers having 25.4 mm diameters and 1 MHz nominal resonant frequencies, mounted on steel walls having lengths in the range of 57.15 to 304.8 mm. A protocol is described which uses ultrasonic waves to achieve simultaneous bidirectional communication through the metallic enclosures. It is shown that such channels are very frequency selective, and a carrier frequency selection and tracking algorithm is presented to choose a frequency of operation at which both adequate power delivery and reliable full-duplex communication are achieved. Using this algorithm, sufficient power is harvested to allow for the continuous operation of internal electronics which require an aggregate of less than 100 mW. Reliable communication of sensor data is achieved at rates in excess of 30 kbps.