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 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 Development of a Class-C Power Amplifier with Diode Expander Architecture for Point-of-Care Ultrasound Systems

Micromachines ◽  
2019 ◽  
Vol 10 (10) ◽  
pp. 697 ◽  
Author(s):  
Hojong Choi
Keyword(s):  
Power Amplifier ◽  
Power Amplifiers ◽  
Point Of Care ◽  
Ultrasonic Transducer ◽  
Input Pulse ◽  
Point Of Care Ultrasound ◽  
Potential Candidate ◽  
Excessive Heat ◽  
System Sensitivity ◽  
Class C

Point-of-care ultrasound systems are widely used in ambulances and emergency rooms. However, the excessive heat generated from ultrasound transmitters has an impact on the implementation of piezoelectric transducer elements and on battery consumption, thereby affecting the system’s sensitivity and resolution. Non-linear power amplifiers, such as class-C amplifiers, could substitute linear power amplifiers, such as class-A amplifiers, which are currently used in point-of-care ultrasound systems. However, class-C power amplifiers generate less output power, resulting in a reduction of system sensitivity. To overcome this issue, we propose a new diode expander architecture dedicated to power amplifiers to reduce the effects of sinusoidal pulses toward the power supply. Thus, the proposed architecture could increase the input pulse amplitudes applied to the main transistors in the power amplifiers, hence increasing the output voltage of such amplifiers. To verify the proposed concept, pulse-echo responses from an ultrasonic transducer were tested with the developed class-C power amplifier using a resistor divider and the designed diode expander architecture. The peak-to-peak amplitude of the echo signals of the ultrasonic transducers when using a class-C power amplifier with a diode expander architecture (2.98 Vp–p) was higher than that for the class-C power amplifier with a resistor divider architecture (2.51 Vp–p). Therefore, the proposed class-C power amplifier with diode expander architecture is a potential candidate for improving the sensitivity performance of piezoelectric transducers for point-of-care ultrasound systems.

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).

scholarly journals A Fluidics-Based Double Flexural Membrane Piezoelectric Micromachined Ultrasonic Transducer (PMUT) for Wide-Bandwidth Underwater Acoustic Applications

Sensors ◽  
2021 ◽  
Vol 21 (16) ◽  
pp. 5582
Author(s):  
Khairul Azman Ahmad ◽  
Mohamad Faizal Abd Rahman ◽  
Khairu Anuar Mohamed Zain ◽  
Muhammad Naim Haron ◽  
Asrulnizam Abd Manaf
Keyword(s):  
Wide Spectrum ◽  
Ultrasonic Transducer ◽  
Center Frequency ◽  
Receiver Design ◽  
Wide Bandwidth ◽  
Element Analysis ◽  
Underwater Acoustic ◽  
Novel Structure ◽  
Backing Layer ◽  
Pulse Echo

In acoustic receiver design, the receiving sensitivity and bandwidth are two primary parameters that determine the performance of a device. The trade-off between sensitivity and bandwidth makes the design very challenging, meaning it needs to be fine-tuned to suit specific applications. The ability to design a PMUT with high receiving sensitivity and a wide bandwidth is crucial to allow a wide spectrum of transmitted frequencies to be efficiently received. This paper presents a novel structure involving a double flexural membrane with a fluidic backing layer based on an in-plane polarization mode to optimize both the receiving sensitivity and frequency bandwidth for medium-range underwater acoustic applications. In this structure, the membrane material and electrode configuration are optimized to produce good receiving sensitivity. Simultaneously, a fluidic backing layer is introduced into the double flexural membrane to increase the bandwidth. Several piezoelectric membrane materials and various electrode dimensions were simulated using finite element analysis (FEA) techniques to study the receiving performance of the proposed structure. The final structure was then fabricated based on the findings from the simulation work. The pulse–echo experimental method was used to characterize and verify the performance of the proposed device. The proposed structure was found to have an improved bandwidth of 56.6% with a receiving sensitivity of −1.8864 dB rel 1 V µPa. For the proposed device, the resonance frequency and center frequency were 600 and 662.5 kHz, respectively, indicating its suitability for the targeted frequency range.

scholarly journals Design and Analysis of Super Wideband Antenna for Microwave Applications

Sensors ◽  
2021 ◽  
Vol 21 (2) ◽  
pp. 477
Author(s):  
Warsha Balani ◽  
Mrinal Sarvagya ◽  
Ajit Samasgikar ◽  
Tanweer Ali ◽  
Pradeep Kumar
Keyword(s):  
Communication Systems ◽  
Equivalent Circuit Model ◽  
Wireless Communication Systems ◽  
Impedance Bandwidth ◽  
Frequency Range ◽  
Fractional Bandwidth ◽  
Wide Bandwidth ◽  
Wireless Applications ◽  
Frequency Constraint ◽  
Time Domain Characterization

In this article, a compact concentric structured monopole patch antenna for super wideband (SWB) application is proposed and investigated. The essential characteristics of the designed antenna are: (i) to attain super-wide bandwidth characteristics, the proposed antenna is emerged from a traditional circular monopole antenna and has obtained an impedance bandwidth of 38.9:1 (ii) another important characteristic of the presented antenna is its larger bandwidth dimension ratio (BDR) value of 6596 that is accomplished by augmenting the electrical length of the patch. The electrical dimension of the proposed antenna is 0.18λ×0.16λ (λ corresponds to the lower end operating frequency). The designed antenna achieves a frequency range from 1.22 to 47.5 GHz with a fractional bandwidth of 190% and exhibiting S11 < −10 dB in simulation. For validating the simulated outcomes, the antenna model is fabricated and measured. Good conformity is established between measured and simulated results. Measured frequency ranges from 1.25 to 40 GHz with a fractional bandwidth of 188%, BDR of 6523 and S11 < −10 dB. Even though the presented antenna operates properly over the frequency range from 1.22 to 47.5 GHz, the results of the experiment are measured till 40 GHz because of the high-frequency constraint of the existing Vector Network Analyzer (VNA). The designed SWB antenna has the benefit of good gain, concise dimension, and wide bandwidth above the formerly reported antenna structures. Simulated gain varies from 0.5 to 10.3 dBi and measured gain varies from 0.2 to 9.7 dBi. Frequency domain, as well as time-domain characterization, has been realized to guide the relevance of the proposed antenna in SWB wireless applications. Furthermore, an equivalent circuit model of the proposed antenna is developed, and the response of the circuit is obtained. The presented antenna can be employed in L, S, C, X, Ka, K, Ku, and Q band wireless communication systems.

Installation for testing electronic voltmeters over a wide frequency range

1976 ◽  
Vol 19 (10) ◽  
pp. 1525-1526
Author(s):  
A. M. Fedorov ◽  
V. V. Krestovskii ◽  
V. S. Kiselev ◽  
S. A. Razumovskii ◽  
V. A. Shcheglov
Keyword(s):  
Wide Frequency Range ◽  
Frequency Range
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