scholarly journals Prelinearized Class-B Power Amplifier for Piezoelectric Transducers and Portable Ultrasound Systems

Sensors ◽  
2019 ◽  
Vol 19 (2) ◽  
pp. 287 ◽  
Author(s):  
Hojong Choi
Keyword(s):  
Power Amplifier ◽  
Power Amplifiers ◽  
Heat Dissipation ◽  
Piezoelectric Transducers ◽  
Battery Life ◽  
Portable Ultrasound ◽  
Class A ◽  
Class B ◽  
Cooling Fans ◽  
Pulse Echo

Portable ultrasound systems typically suffer from unwanted heat and limited battery life, resulting in reduced system performance or the applicable number of piezoelectric transducer elements. This can be a bottleneck in widely used portable ultrasound systems. Class-A power amplifiers are typically used in portable ultrasound systems. However, unwanted heat dissipation needs to be reduced by using large cooling fans and heat pipe structures. To reduce unwanted heat, class-B power amplifiers may be a possible solution. However, the non-linearity of class-B power amplifiers could limit their integration with piezoelectric transducers because non-linearity in the high-voltage output of the power amplifiers deteriorates the sensitivity of portable ultrasound systems. To improve the linearity of the power amplifier, we developed prelinearized class-B power amplifiers for piezoelectric transducers and portable ultrasound systems. To verify our proposed method, we compared the performances of class-B and prelinearized class-B power amplifiers in their pulse-echo responses. Therefore, prelinearized class-B power amplifiers are a possible solution to produce better echo signal performance in piezoelectric transducers and portable ultrasound systems.

scholarly journals Wide Bandwidth Class-S Power Amplifiers for Ultrasonic Devices

Sensors ◽  
2020 ◽  
Vol 20 (1) ◽  
pp. 290 ◽  
Author(s):  
Kiheum You ◽  
Hojong Choi
Keyword(s):  
Power Amplifier ◽  
Power Amplifiers ◽  
Ultrasonic Transducer ◽  
Wide Frequency Range ◽  
Frequency Range ◽  
Wide Bandwidth ◽  
Class A ◽  
Ultrasonic Devices ◽  
Constant Output ◽  
Pulse Echo

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.

scholarly journals Class-C Linearized Amplifier for Portable Ultrasound Instruments

Sensors ◽  
2019 ◽  
Vol 19 (4) ◽  
pp. 898 ◽  
Author(s):  
Hojong Choi
Keyword(s):  
Power Consumption ◽  
Output Voltage ◽  
Signal Amplitude ◽  
Piezoelectric Transducers ◽  
Battery Life ◽  
Potential Candidate ◽  
Portable Ultrasound ◽  
Dc Power ◽  
Class C ◽  
Main Components

Transistor linearizer networks are proposed to increase the transmitted output voltage amplitudes of class-C amplifiers, thus, increasing the sensitivity of the echo signals of piezoelectric transducers, which are the main components in portable ultrasound instruments. For such instruments, class-C amplifiers could be among the most efficient amplifier schemes because, compared with a linear amplifier such as a class-A amplifier, they could critically reduce direct current (DC) power consumption, thus, increasing the battery life of the instruments. However, the reduced output voltage amplitudes of class-C amplifiers could deteriorate the sensitivity of the echo signals, thereby affecting the instrument performance. Therefore, a class-C linearized amplifier was developed. To verify the capability of the class-C linearized amplifier, typical pulse-echo responses using the focused piezoelectric transducers were tested. The echo signal amplitude generated by the piezoelectric transducers when using the class-C linearized amplifier was improved (1.29 Vp-p) compared with that when using the class-C amplifier alone (0.56 Vp-p). Therefore, the class-C linearized amplifier could be a potential candidate to increase the sensitivity of echo signals while reducing the DC power consumption for portable ultrasound instruments.

scholarly journals Post-Voltage-Boost Circuit-Supported Single-Ended Class-B Amplifier for Piezoelectric Transducer Applications

Sensors ◽  
2020 ◽  
Vol 20 (18) ◽  
pp. 5412
Author(s):  
Jungsuk Kim ◽  
Kiheum You ◽  
Hojong Choi
Keyword(s):  
Piezoelectric Transducer ◽  
Maximum Output Power ◽  
Piezoelectric Transducers ◽  
Maximum Output ◽  
Good Efficiency ◽  
Acoustic Performance ◽  
Current Consumption ◽  
Class B ◽  
Ultrasound Applications ◽  
Pulse Echo

Piezoelectric transducers are important devices that are triggered by amplifier circuits in mobile ultrasound systems. Therefore, amplifier performance is vital because it determines the acoustic piezoelectric transducer performances. Particularly, mobile ultrasound applications have strict battery performance and current consumption requirements; hence, amplifier devices should exhibit good efficiency because the direct current (DC) voltage in the battery are provided to the supply voltages of the amplifier, thus limiting the maximum DC drain voltages of the main transistors in the amplifier. The maximum DC drain voltages are related with maximum output power if the choke inductor in the amplifier is used. Therefore, a need to improve the amplifier performance of piezoelectric transducers exists for mobile ultrasound applications. In this study, a post-voltage-boost circuit-supported class-B amplifier used for mobile ultrasound applications was developed to increase the acoustic performance of piezoelectric transducers. The measured voltage of the post-voltage-boost circuit-supported class-B amplifier (62 VP-P) is higher than that of only a class-B amplifier (50 VP-P) at 15 MHz and 100 mVP-P input. By performing the pulse-echo measurement test, the echo signal with the post-voltage-boost circuit-supported class-B amplifier (10.39 mVP-P) was also noted to be higher than that with only a class-B amplifier (6.15 mVP-P). Therefore, this designed post-voltage-boost circuit can help improve the acoustic amplitude of piezoelectric transducers used for mobile ultrasound applications.

Generalized Hybrid Continuous Mode for Designing Broadband Power Amplifiers

2020 ◽  
Vol 29 (15) ◽  
pp. 2050236
Author(s):  
Decheng Gan ◽  
Weimin Shi ◽  
Muhammad Furqan Haider
Keyword(s):  
Power Amplifier ◽  
Power Amplifiers ◽  
Drain Current ◽  
Experimental Results ◽  
Continuous Mode ◽  
Current Waveform ◽  
Class Ab ◽  
Saturation Power ◽  
Class B ◽  
Continuous Working

It has been widely validated that continuous working modes are powerful theories for designing broadband power amplifier (BPA). Theoretically, the conduction angle of all continuous-mode power amplifiers (PAs) is 180∘ (class-B-biased). However, in practice, these PAs are always biased in class-AB condition. Thus, continuous-mode PAs biased in class-AB condition should be researched. This paper generalizes the theory of hybrid continuous mode (HCM) for implementing broadband power amplifiers. The intrinsic drain current waveform of HCM biased above the pinch-off point (conduction angle is larger than 180∘) is first derived. Then, the impedance space of the generalized HCM (class-AB-biased) is explored and analyzed. The conclusion is that the generalized HCM possesses a shifted fundamental impedance space along with the enlargement of conduction angle. For validating the proposed theory, a broadband PA working over 1.6–3.0[Formula: see text]GHz is implemented. Experimental results indicate that the designed BPA achieves a saturation power of 40.3–42.7[Formula: see text]dBm and a drain efficiency of 64.3–74.4%.

scholarly journals Fundamental limits of high-efficiency silicon and compound semiconductor power amplifiers in 100-300 GHz bands

2021 ◽  
Vol 2 (7) ◽  
pp. 39-50
Author(s):  
James F. Buckwalter ◽  
Mark J. W. Rodwell ◽  
Kang Ning ◽  
Ahmed Ahmed ◽  
Andrea Arias-Purdue ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
Power Amplifier ◽  
High Efficiency ◽  
Fundamental Limits ◽  
Class A ◽  
Energy Efficient Communication ◽  
Efficient Communication ◽  
Class B ◽  
Matching Element ◽  
Circuit Techniques

This paper reviews the requirements for future digital arrays in terms of power amplifier requirements for output power and efficiency and the device technologies that will realize future energy-efficient communication and sensing electronics for the upper millimeter-wave bands (100-300 GHz). Fundamental device technologies are reviewed to compare the needs for compound semiconductors and silicon processes. Power amplifier circuit design above 100 GHz is reviewed based on load line and matching element losses. We present recently presented class-A and class-B PAs based on a InP HBT process that have demonstrated record efficiency and power around 140 GHz while discussing circuit techniques that can be applied in a variety of integrated circuits.

Enhanced performance of a 60-GHz power amplifier by using slow-wave transmission lines in 40 nm CMOS technology

2011 ◽  
Vol 4 (1) ◽  
pp. 93-100 ◽  
Author(s):  
Xiao-Lan Tang ◽  
Emmanuel Pistono ◽  
Philippe Ferrari ◽  
Jean-Michel Fournier
Keyword(s):  
Millimeter Wave ◽  
Power Amplifier ◽  
Slow Wave ◽  
Transmission Lines ◽  
Power Amplifiers ◽  
Cmos Technology ◽  
Wave Transmission ◽  
60 Ghz ◽  
Microstrip Lines ◽  
Class A

This paper shows the contribution of slow-wave coplanar waveguides on the performance of power amplifiers operating at millimeter-wave frequencies in CMOS-integrated technologies. These transmission lines present a quality factor Q two to three times higher than that of the conventional microstrip lines at the same characteristic impedance. To demonstrate the contribution of the slow-wave transmission lines on integrated millimeter-wave amplifiers performance, two Class-A single-stage power amplifiers (PA) operating at 60 GHz were designed in standard 40 nm CMOS technology. One of the power amplifiers incorporates only the microstrip lines, whereas slow-wave coplanar transmission lines are considered in the other one. Both amplifiers are biased in Class-A operation, drawing, respectively, 22 and 23 mA from 1.2 V supply. Compared to the power amplifier using conventional microstrip transmission lines, the one implemented with slow-wave transmission lines shows improved performances in terms of gain (5.6 dB against 3.3 dB), 1 dB output compression point (OCP1dB: 7 dBm against 5 dBm), saturated output power (Psat: >10 and 8 dBm, respectively), power-added efficiency (PAE: 16% instead of 6%), and die area without pads (Sdie: 0.059 mm2 against 0.069 mm2).

Оценка реальной чувствительности приемочного ультразвукового контроля рельсов

2020 ◽  
pp. 17-27
Author(s):  
А.А. Шелухин
Keyword(s):  
Ultrasonic Pulse ◽  
Piezoelectric Transducers ◽  
Acoustic Path ◽  
Metallic Inclusion ◽  
Inclusion Type ◽  
The Real ◽  
Rail Head ◽  
Pulse Echo

In this article, the analysis of the acoustic path during the ultrasonic pulse echo testing of the rail head in production is carried out. The influence of the parameters of the applied piezoelectric transducers on the distribution of sensitivity for the sounding scheme used in the existing installations is estimated and the real sensitivity of detecting defects of the «non-metallic inclusion» type is estimated.

مهارة الكلام منظور من عملية التعلم والتعليم في جامعة باتوسنجكر الاسلامية الحكومية سومطرى الغربية

2019 ◽  
Vol 1 (1) ◽  
Author(s):  
Suharmon Suharmon
Keyword(s):  
Teaching Strategies ◽  
Language Education ◽  
Arabic Language ◽  
Descriptive Statistics ◽  
Quantitative Approach ◽  
Motivation To Learn ◽  
Education Department ◽  
Class A ◽  
Class B ◽  
Speaking Skill

This research aims to obtain infomation about Arabic learning especially speaking skill in Arabic Language Education Department at IAIN Batusangkar. The research uses a quantitative approach. The instruments to collect the data are test and questionnaire. The data were analyzed using descriptive statistics. The results of the research state that the students’ speaking ability at class “ A “ are 28% low, 36% moderate, and 36% high. While, at class “B”, students’ speaking abilities are 36.4% low, 40,9% moderate, and 22.7% high. The cause of students’ low ability is the unappropriateness of teachers’ strategy in teaching speaking. There are about 96% students at class “A” agreed and 86.4% students at class “B” had similar answer. Another cause is students’ low motivation in learning. Class “A” students agreed for about 76% of them and 77% of class “B” students answered the same. From the finding, it can be concluded that the inability of students to speak Arabic can be overcomed by improving teaching strategies and encouraging maximum motivation  to learn Arabic.

scholarly journals Some kinematics of halo coronal mass ejections

2020 ◽  
Vol 29 (1) ◽  
pp. 81-88
Author(s):  
Virendra Kumar Verma ◽  
Nishant Mittal ◽  
Ramesh Chandra
Keyword(s):  
Coronal Mass Ejections ◽  
Solar Flares ◽  
Coronal Holes ◽  
Geomagnetic Disturbances ◽  
Class A ◽  
Heliospheric Physics ◽  
Class B ◽  
The Mean ◽  
Class C

AbstractWe present an investigation of halo coronal mass ejections (HCMEs) kinematics and other facts about the HCMEs. The study of HCMEs is very important because HCMEs are regarded as the main causes of heliospheric and geomagnetic disturbances. In this study, we have investigated 313 HCMEs observed during 1996-2012 by LASCO, coronal holes, and solar flares. We find that HCMEs are of two types: accelerated HCMEs and decelerated HCMEs. The mean space speed of HCMEs is 1283 km/s while the mean speed of decelerated HCMEs and accelerated HCMEs is 1349 km/s and 1174 km/s, respectively. The investigation shows that 1 (0.3%) HCME was associated with class A SXR, 14 (4.7%) HCMEs were associated with class B SXR-flares, 87 (29.4%) HCMEs were associated with class C SXR-flares, 125 (42.2%) HCMEs were associated with class M SXR-flares and 69 (23.3%) HCMEs were associated with class X SXR-flares. The speed of HCMEs increases with the importance of solar SXR-flares. The various results obtained in the present analysis are discussed in the light of the existing scenario of heliospheric physics.

Sign in / Sign up

Export Citation Format

Share Document