A New Approach to Power Efficiency Improvement of Ultrasonic Transmitters via a Dynamic Bias Technique

To achieve optimal mobility, visually impaired people have to deal with obstacle detection and avoidance challenges. Aside from the broadly adopted white cane, electronic aids have been developed. However, available electronic devices are not extensively used due to their complexity and price. As an effort to improve the existing ones, this work presents the design of a low-cost aid for blind people. A standard low-cost HC-SRF04 ultrasonic range is modified by adding phase modulation in the ultrasonic pulses, allowing it to detect the origin of emission, thus discriminating if the echo pulses come from the same device and avoiding false echoes due to interference from other sources. This improves accuracy and security in areas where different ultrasonic sensors are working simultaneously. The final device, based on users and trainers feedback for the design, works with the user’s own mobile phone, easing utilization and lowering manufacturing costs. The device was tested with a set of twenty blind persons carrying out a travel experiment and satisfaction survey. The main results showed a change in total involuntary contacts with unknown obstacles and high user satisfaction. Hence, we conclude that the device can fill a gap in the mobility aids and reduce feelings of insecurity amongst the blind.

Section: Methodsmentioning

confidence: 99%

Low-Cost Ultrasonic Range Improvements for an Assistive Device

Abreu

Toledo

Codina

et al. 2021

“…In the proposed harmonic-reduced bias circuit, it is possible to reduce certain harmonic distortion components such as second, third, and fourth harmonic distortion components simultaneously. The ultrasound transducer is a kind of capacitive load with resistance, capacitance, and inductance [63][64][65]. Therefore, the operating frequency in the second, third, and fourth harmonic distortion components of the power amplifier is not exactly two, three, and four times the operating frequency of the ultrasound transducer, respectively [66][67][68].…”

Section: The Class-c Power Amplifier Fabricationmentioning

confidence: 99%

Harmonic-Reduced Bias Circuit for Ultrasound Transducers

Choi

2023

Self Cite

The gain of class-C power amplifiers is generally lower than that of class-A power amplifiers. Thus, higher-amplitude input voltage signals for class-C power amplifiers are required. However, high-amplitude input signals generate unwanted harmonic signals. Therefore, a novel bias circuit was proposed to suppress the harmonic signals generated by class-C power amplifiers, which improves the output voltage amplitudes. To verify the proposed idea, the input harmonic signals when using a harmonic-reduced bias circuit (−61.31 dB, −89.092 dB, −90.53 dB, and −90.32 dB) were measured and were found to be much lower than those when using the voltage divider bias circuit (−57.19 dB, −73.49 dB, −70.97 dB, and −73.61 dB) at 25 MHz, 50 MHz, 75 MHz, and 100 MHz, respectively. To further validate the proposed idea, the pulse-echo measurements were compared using the bias circuits. The peak-to-peak echo amplitude and bandwidth of the piezoelectric transducer, measured when using a harmonic-reduced bias circuit (27.07 mV and 37.19%), were higher than those achieved with a voltage divider circuit (18.55 mV and 22.71%). Therefore, the proposed scheme may be useful for ultrasound instruments with low sensitivity.

“…Typical performance parameters of power amplifiers are gain, bandwidth, and linearity [ 13 , 14 , 15 , 16 ]. However, the best values for all parameters cannot be simultaneously achieved because the main electronic component is the transistor, which has unwanted parasitic resistance, capacitance, and inductance [ 17 , 18 , 19 ]. Therefore, a power amplifier must be specifically designed for various ultrasound applications.…”

Section: Introductionmentioning

confidence: 99%

An Inverse Class-E Power Amplifier for Ultrasound Transducer

Choi

2023

Self Cite

An inverse Class-E power amplifier was designed for an ultrasound transducer. The proposed inverse Class-E power amplifier can be useful because of the low series inductance values used in the output matching network that helps to reduce signal distortions. Therefore, a newly designed Class-E power amplifier can obtain a proper echo signal quality. The measured output voltage, voltage gain, voltage gain difference, and power efficiency were 50.1 V, 22.871 dB, 0.932 dB, and 55.342%, respectively. This low voltage difference and relatively high efficiency could verify the capability of the ultrasound transducer. The pulse-echo response experiment using an ultrasound transducer was performed to verify the capability of the proposed inverse Class-E power amplifier. The obtained echo signal amplitude and pulse width were 6.01 mVp-p and 0.81 μs, respectively. The −6 dB bandwidth and center frequencies of the echo signal were 27.25 and 9.82 MHz, respectively. Consequently, the designed Class-E power amplifier did not significantly alter the performance of the center frequency of the ultrasound transducer; therefore, it could be employed particularly in certain ultrasound applications that require high linearity and reasonable power efficiency.