Abstract
Wide bandwidth ultrasonic devices are a necessity in high-resolution ultrasonic systems. Therefore, constant output voltages need to be produced across the wide bandwidths of a power amplifier. We present the first design of a wide bandwidth class-S power amplifier for ultrasonic devices. The −6 dB bandwidth of the developed class-S power amplifier was measured at 125.07% at 20 MHz, thus, offering a wide bandwidth for ultrasonic devices. Pulse-echo measurement is a performance measurement method used to evaluate the performance of ultrasonic transducers, components, or systems. The pulse-echo signals were obtained using an ultrasonic transducer with designed power amplifiers. In the pulse-echo measurements, time and frequency analyses were conducted to evaluate the bandwidth flatness of the power amplifiers. The frequency range of the ultrasonic transducer was measured and compared when using the developed class-S and commercial class-A power amplifiers with the same output voltages. The class-S power amplifiers had a relatively flat bandwidth (109.7 mV at 17 MHz, 112.0 mV at 20 MHz, and 109.5 mV at 23 MHz). When the commercial class-A power amplifier was evaluated under the same conditions, an uneven bandwidth was recorded (110.6 mV at 17 MHz, 111.5 mV at 20 MHz, and 85.0 mV at 23 MHz). Thus, we demonstrated that the designed class-S power amplifiers could prove useful for ultrasonic devices with a wide frequency range.
Highlights
An increasing number of industrial fields are currently employing ultrasonic devices [1]
The input signals of the class–S power amplifiers are used in combination with the modulated signals and adjacent narrow band frequency amplifiers are used in combination with the modulated signals and adjacent narrow band frequency signals to cover relatively wide bandwidths, which are generally
The power gain was obtained by measuring the output voltage of the power amplifier using an oscilloscope
Summary
An increasing number of industrial fields are currently employing ultrasonic devices [1]. These devices are used for underwater explorations, non-destructive testing, glass processing, in humidifiers, ultrasonic cleaners, and cell phones [1,6]. The ultrasonic signals from small-sized devices are very low, requiring a high voltage signal from the power amplifiers to properly trigger such devices [7,8]. The analog signal processing components (expander/limiter, power amplifier, and pre-amplifier) play a key role in determining the overall system performance [11]. The expander and limiter can reduce signal ring-down and block high voltage pulses, respectively [12]. The echo signals generated from the transducer are sent via the ADC to the display [11,14]
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