Bias-Voltage Stabilizer for HVHF Amplifiers in VHF Pulse-Echo Measurement Systems
- Authors
- Choi, Hojong; Park, Chulwoo; Kim, Jungsuk; Jung, Hayong
- Issue Date
- Oct-2017
- Publisher
- MDPI
- Keywords
- bias-voltage stabilizer; high-voltage-high-frequency amplifier; VHF ultrasound transducers; pulse-echo measurement systems
- Citation
- SENSORS, v.17, no.10
- Journal Title
- SENSORS
- Volume
- 17
- Number
- 10
- URI
- https://scholarworks.bwise.kr/gachon/handle/2020.sw.gachon/5677
- DOI
- 10.3390/s17102425
- ISSN
- 1424-8220
- Abstract
- 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.
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