Amplifiers in Biomedical Engineering: A Review from Application Perspectives

Continuous monitoring and treatment of various diseases with biomedical technologies and wearable electronics has become significantly important. The healthcare area is an important, evolving field that, among other things, requires electronic and micro-electromechanical technologies. Designed circuits and smart devices can lead to reduced hospitalization time and hospitals equipped with high-quality equipment. Some of these devices can also be implanted inside the body. Recently, various implanted electronic devices for monitoring and diagnosing diseases have been presented. These instruments require communication links through wireless technologies. In the transmitters of these devices, power amplifiers are the most important components and their performance plays important roles. This paper is devoted to collecting and providing a comprehensive review on the various designed implanted amplifiers for advanced biomedical applications. The reported amplifiers vary with respect to the class/type of amplifier, implemented CMOS technology, frequency band, output power, and the overall efficiency of the designs. The purpose of the authors is to provide a general view of the available solutions, and any researcher can obtain suitable circuit designs that can be selected for their problem by reading this survey

Techniques for high-efficiency outphasing power amplifiers

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 171-177).A trade-off between linearity and efficiency exists in conventional power amplifiers (PAs). The outphase amplifying concept overcomes this trade-off by enabling the use of high efficiency, non-linear power amplifiers for linear amplification. However, the efficiency improvement is limited by the efficiency of the output power combiner. This thesis investigates techniques to overcome this efficiency limit while maintaining sufficient linearity. Two techniques are proposed. The first technique is called the outphasing energy recovery amplifier (OPERA), which recovers the normally wasted power back to the power supply and utilizes a resistance compression network for improved linearity. A 48-MHz, 20-W prototype OPERA system was built which demonstrates more than 2x higher efficiency than the standard outphasing system for a 16-QAM signal. The second technique to improve the efficiency of the outphasing system is asymmetric multilevel outphasing (AMO) modulation. In the AMO system, the amplitude for each of the two outphased PAs can switch independently among multiple discrete levels, significantly reducing the energy lost in the power combiner. Three different AMO prototypes were built, each of which demonstrate between 2x-3x efficiency improvement compared to the standard outphasing system. A 2.4-GHz, 500- mW prototype made in a 65-nm CMOS process achieves an average system efficiency of 28.7% for a 20-MHz 64-QAM signal. To the author's best knowledge, this is the highest reported efficiency for a CMOS PA in the 2-2.7 GHz range for signal bandwidths greater than 10 MHz.by Philip Andrew Godoy.Ph.D

Integrated Circuits for Medical Ultrasound Applications: Imaging and Beyond

Medical ultrasound has become a crucial part of modern society and continues to play a vital role in the diagnosis and treatment of illnesses. Over the past decades, the develop- ment of medical ultrasound has seen extraordinary progress as a result of the tremendous research advances in microelectronics, transducer technology and signal processing algorithms. How- ever, medical ultrasound still faces many challenges including power-efficient driving of transducers, low-noise recording of ultrasound echoes, effective beamforming in a non-linear, high- attenuation medium (human tissues) and reduced overall form factor. This paper provides a comprehensive review of the design of integrated circuits for medical ultrasound applications. The most important and ubiquitous modules in a medical ultrasound system are addressed, i) transducer driving circuit, ii) low- noise amplifier, iii) beamforming circuit and iv) analog-digital converter. Within each ultrasound module, some representative research highlights are described followed by a comparison of the state-of-the-art. This paper concludes with a discussion and recommendations for future research directions

Design and implementation of intravascular hifu catheter ablation system

High-intensity focused ultrasound is an energy-based thermal therapy for noninvasive or minimally invasive treatment of wide range of medical disorders including solid cancer tumors, brain surgery, atrial fibrillation (AF) and other cardiac arrhythmias. Conventional HIFU is extracorporeally administered but in applications where a small lesion or more precise energy localization in shorter time is required, catheter-based HIFU devices which are positioned directly within or adjacent to the target may be the best solution. Available HIFU catheters use array of piezoelectric transducers with complex external high-voltage (HV) and high-frequency amplifiers, a cooling system and several coaxial cables within the catheter. In this study, a HV transmitter IC has been designed, manufactured and integrated with an 8-element capacitive micromachined ultrasound transducer (CMUT) on a prototype HIFU probe appropriate for a 6-Fr catheter. The transmitter IC fabricated in 0.35 μm HV CMOS process and comprises eight continuouswave HV buffers (10.9 ns and 9.4 ns rise and fall times at 20 Vpp output into a 15 pF), an eight-channel transmit beamformer (8-12 MHz output frequency with 11.25 º phase accuracy) and a phase locked loop with an integrated VCO as a tunable clock source (128–192 MHz). The chip occupies 1.85×1.8 mm2 area including input and output (I/O) pads. Electrical measurements, IR thermography and Ex-vivo experiment results reveal that the presented HIFU system can elevate the temperature of the target region of tissue around 19 ºC by delivering 600 CEM43 equivalent thermal dose while surface temperature of the probe rises less than 5 º

Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance

Design and analysis of wideband passive microwave devices using planar structures

A selected volume of work consisting of 84 published journal papers is presented to demonstrate the contributions made by the author in the last seven years of his work at the University of Queensland in the area of Microwave Engineering. The over-arching theme in the author’s works included in this volume is the engineering of novel passive microwave devices that are key components in the building of any microwave system. The author’s contribution covers innovative designs, design methods and analyses for the following key devices and associated systems: Wideband antennas and associated systems Band-notched and multiband antennas Directional couplers and associated systems Power dividers and associated systems Microwave filters Phase shifters Much of the motivation for the work arose from the desire to contribute to the engineering o

GSI Scientific Report 2016

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Performance Analysis For Wireless G (IEEE 802.11 G) And Wireless N (IEEE 802.11 N) In Outdoor Environment

This paper described an analysis the different capabilities and limitation of both IEEE technologies that has been utilized for data transmission directed to mobile device. In this work, we have compared an IEEE 802.11/g/n outdoor environment to know what technology is better. the comparison consider on coverage area (mobility), through put and measuring the interferences. The work presented here is to help the researchers to select the best technology depending of their deploying case, and investigate the best variant for outdoor. The tool used is Iperf software which is to measure the data transmission performance of IEEE 802.11n and IEEE 802.11g

Performance analysis for wireless G (IEEE 802.11G) and wireless N (IEEE 802.11N) in outdoor environment

This paper described an analysis the different capabilities and limitation of both IEEE technologies that has been utilized for data transmission directed to mobile device. In this work, we have compared an IEEE 802.11/g/n outdoor environment to know what technology is better. The comparison consider on coverage area (mobility), throughput and measuring the interferences. The work presented here is to help the researchers to select the best technology depending of their deploying case, and investigate the best variant for outdoor. The tool used is Iperf software which is to measure the data transmission performance of IEEE 802.11n and IEEE 802.11g