Choi Hojong, Park Chulwoo, Kim Jungsuk, Jung Hayong
Department of Medical IT Convergence Engineering, Kumho National Institute of Technology, Gumi 39253, Korea.
Department of Biomedical Engineering, Gachon University, In-cheon 21936, Korea.
Sensors (Basel). 2017 Oct 23;17(10):2425. doi: 10.3390/s17102425.
The impact of high-voltage-high-frequency (HVHF) amplifiers on echo-signal quality is greater with very-high-frequency (VHF, ≥100 MHz) ultrasound transducers than with low-frequency (LF, ≤15 MHz) ultrasound transducers. Hence, the bias voltage of an HVHF amplifier must be stabilized to ensure stable echo-signal amplitudes. We propose a bias-voltage stabilizer circuit to maintain stable DC voltages over a wide input range, thus reducing the harmonic-distortion components of the echo signals in VHF pulse-echo measurement systems. To confirm the feasibility of the bias-voltage stabilizer, we measured and compared the deviations in the gain of the HVHF amplifier with and without a bias-voltage stabilizer. Between -13 and 26 dBm, the measured gain deviations of a HVHF amplifier with a bias-voltage stabilizer are less than that of an amplifier without a bias-voltage stabilizer. In order to confirm the feasibility of the bias-voltage stabilizer, we compared the pulse-echo responses of the amplifiers, which are typically used for the evaluation of transducers or electronic components used in pulse-echo measurement systems. From the responses, we observed that the amplitudes of the echo signals of a VHF transducer triggered by the HVHF amplifier with a bias-voltage stabilizer were higher than those of the transducer triggered by the HVHF amplifier alone. The second, third, and fourth harmonic-distortion components of the HVHF amplifier with the bias-voltage stabilizer were also lower than those of the HVHF amplifier alone. Hence, the proposed scheme is a promising method for stabilizing the bias voltage of an HVHF amplifier, and improving the echo-signal quality of VHF transducers.
与低频（LF，≤15MHz）超声换能器相比，高压高频（HVHF）放大器对甚高频（VHF，≥100MHz）超声换能器的回波信号质量影响更大。因此，必须稳定HVHF放大器的偏置电压，以确保回波信号幅度稳定。我们提出一种偏置电压稳定器电路，以在宽输入范围内维持稳定的直流电压，从而减少VHF脉冲回波测量系统中回波信号的谐波失真分量。为了确认偏置电压稳定器的可行性，我们测量并比较了有和没有偏置电压稳定器时HVHF放大器增益的偏差。在-13至26dBm之间，带有偏置电压稳定器的HVHF放大器的测量增益偏差小于没有偏置电压稳定器的放大器。为了确认偏置电压稳定器的可行性，我们比较了放大器的脉冲回波响应，这些响应通常用于评估脉冲回波测量系统中使用的换能器或电子元件。从响应中我们观察到，由带有偏置电压稳定器的HVHF放大器触发的VHF换能器的回波信号幅度高于仅由HVHF放大器触发的换能器。带有偏置电压稳定器的HVHF放大器的二次、三次和四次谐波失真分量也低于仅HVHF放大器的分量。因此，所提出的方案是一种稳定HVHF放大器偏置电压并提高VHF换能器回波信号质量的有前景的方法。
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