A band notch rectangular patch UWB antenna with time domain analysis

Design and construction of band notch microstrip Ultra-wideband (UWB) antenna is proposed. As the WLAN 802.11a operates ranging from 5.15GHz to 5.35GHz and 5.725GHz to 5.825GHz. In contrast, HIPERLAN/2 operates ranging from 5.15GHz to 5.35GHz and 5.47GHz to 5.725GHz. Therefore, a band notched filter is required in order to reduce potential interferences between the UWB antenna and WLAN or HIPERLAN/2 bands. The proposed UWB antenna has capability of notching these operating frequencies approximately around 5GHz to 6GHz. The antenna parameters in frequency domain analysis have been investigated to show its capability as an effective radiating element. Furthermore, time domain Gaussian pulse excitation analysis in UWB systems is also demonstrated in this paper. As a result, the simulation results demonstrated reasonable agreement with the measurement results and good band notched ultra-wideband linear transmission performance has also been achieved in time domain

Mutual Coupling Compensated Multiband Linear Antenna Arrays for Radio Frequency Energy Harvesting/Transmitting

RF energy transmitting is an approach to deliver charging energy wirelessly, while RF energy harvesting is an approach to re-charge battery by capturing ambient RF energy. A multiband system composed of mutual coupling compensated linear antenna arrays and output LC matched RF-DC rectifier is proposed for RF energy harvesting and transmitting. The designed system operates in standard communication bands such as GSM850, GSM900, GSM1800, GSM1900, WiFi, Bluetooth, and LTE since ample RF ambient signals are present and numerous IoT sensors operates in these frequency bands. The design starts from a highly efficient double-ring monopole antenna. The proposed antenna has both wideband and multiband features to cover the target operating frequencies. According to Friis transmission equation, the captured/radiated RF power is proportional to the antenna gain, thus antenna array composed of double-ring monopoles is investigated to increase antenna gain. In the proposed four-element antenna array, a four-way RF energy combiner with optimum power combining efficiency is implemented to connect four antennas. Triple-band radiation patterns are synthesized by by mutual coupling compensation structure. The proposed output LC matched RF-DC rectifier is connected to antenna array to convert RF power to DC energy. The rectifier sensitivity and power conversion efficiency is boosted with dual frequency tones. System measurement results state that not only the antenna gain but also the radiation pattern of antenna array affects the total captured RF power. Antenna array is preferable to be installed at the transmitting side for RF energy transfer, while the single antenna is preferable to be installed at the receiving side for RF energy harvesting. If the receiving area is not limited, then the rectenna array composed of antenna arrays and RF-DC rectifiers can be applied for RF energy harvesting

Mutual Coupling Compensated Multiband Linear Antenna Arrays for Radio Frequency Energy Harvesting/Transmitting

RF energy transmitting is an approach to deliver charging energy wirelessly, while RF energy harvesting is an approach to re-charge battery by capturing ambient RF energy. A multiband system composed of mutual coupling compensated linear antenna arrays and output LC matched RF-DC rectifier is proposed for RF energy harvesting and transmitting. The designed system operates in standard communication bands such as GSM850, GSM900, GSM1800, GSM1900, WiFi, Bluetooth, and LTE since ample RF ambient signals are present and numerous IoT sensors operates in these frequency bands. The design starts from a highly efficient double-ring monopole antenna. The proposed antenna has both wideband and multiband features to cover the target operating frequencies. According to Friis transmission equation, the captured/radiated RF power is proportional to the antenna gain, thus antenna array composed of double-ring monopoles is investigated to increase antenna gain. In the proposed four-element antenna array, a four-way RF energy combiner with optimum power combining efficiency is implemented to connect four antennas. Triple-band radiation patterns are synthesized by by mutual coupling compensation structure. The proposed output LC matched RF-DC rectifier is connected to antenna array to convert RF power to DC energy. The rectifier sensitivity and power conversion efficiency is boosted with dual frequency tones. System measurement results state that not only the antenna gain but also the radiation pattern of antenna array affects the total captured RF power. Antenna array is preferable to be installed at the transmitting side for RF energy transfer, while the single antenna is preferable to be installed at the receiving side for RF energy harvesting. If the receiving area is not limited, then the rectenna array composed of antenna arrays and RF-DC rectifiers can be applied for RF energy harvesting

Wideband and wide beam polyvinylidene difluoride (PVDF) acoustic transducer for broadband underwater communications

The advances in wireless communications are still very limited when intended to be used on Underwater Communication Systems mainly due to the adverse proprieties of the submarine channel to the acoustic and radio frequency (RF) waves propagation. This work describes the development and characterization of a polyvinylidene difluoride ultrasound transducer to be used as an emitter in underwater wireless communications. The transducer has a beam up to 10° × 70° degrees and a usable frequency band up to 1 MHz. The transducer was designed using Finite Elements Methods and compared with real measurements. Pool trials show a transmitting voltage response (TVR) of approximately 150 dB re µPa/V@1 m from 750 kHz to 1 MHz. Sea trials were carried in Ria Formosa, Faro (Portugal) over a 15 m source-receiver communication link. All the signals were successfully detected by cross-correlation using 10 chirp signals between 10 to 900 kHz.Agência financiadora Programa Operacional Regional do Norte (NORTE2020), through Fundo Europeu de Desenvolvimento Regional (FEDER) NORTE-01-0145-FEDER-000032-NextSea Fundacao para a Ciencia e a Tecnologia (FCT) UID/EEA/04436/2019 SFRH/BPD/107826/2015 MIT-EXPL/IRA/0070/2017info:eu-repo/semantics/publishedVersio

Adaptive windowing in contrast-enhanced intravascular ultrasound imaging

Intravascular ultrasound (IVUS) is one of the most commonly-used interventional imaging techniques and has seen recent innovations which attempt to characterize the risk posed by atherosclerotic plaques. One such development is the use of microbubble contrast agents to image vasa vasorum, fine vessels which supply oxygen and nutrients to the walls of coronary arteries and typically have diameters less than 200 µm. The degree of vasa vasorum neovascularization within plaques is positively correlated with plaque vulnerability. Having recently presented a prototype dual-frequency transducer for contrast agent-specific intravascular imaging, here we describe signal processing approaches based on minimum variance (MV) beamforming and the phase coherence factor (PCF) for improving the spatial resolution and contrast-to-tissue ratio (CTR) in IVUS imaging. These approaches are examined through simulations, phantom studies, ex vivo studies in porcine arteries, and in vivo studies in chicken embryos. In phantom studies, PCF processing improved CTR by a mean of 4.2 dB, while combined MV and PCF processing improved spatial resolution by 41.7%. Improvements of 2.2 dB in CTR and 37.2% in resolution were observed in vivo. Applying these processing strategies can enhance image quality in conventional B-mode IVUS or in contrast-enhanced IVUS, where signal-to-noise ratio is relatively low and resolution is at a premium

Some studies on designs of planar antennas for UWB applications

In Ultra-Wideband (UWB) wireless system, considerable research efforts have been put into the design of UWB antennas and communication systems. These UWB antennas are essential for providing wireless wideband communications based on the use of very narrow pulses on the order of nanoseconds, covering a very wide bandwidth in the frequency domain and over very short distance at very low power densities. Also it is well known that, in traditional narrow-band communications, multiple antenna systems offer attractive aspects in wireless communication by means of Multiple-Input Multiple-Output (MIMO) techniques. These techniques either give out high channel capacities through spatial multiplexing, or offer an increase of link robustness. The present work deals with four new compact broadband antennas, suitable for portable applications are designed and characterized, namely-octagon shaped monopole, semicircular disk monopole, semi-octagon shaped diversity, semi-circular diversity. The performances of these designs have been studied using standard simulation tools used in industry or academy and experimentally verified. One of the major contributions of the thesis lies in the analysis of the frequency and time-domain response of the designed UWB antennas to confirm their suitability for portable pulsed-UWB system. A technique to avoid narrow band interference by etching narrow slot resonators on the antenna is also proposed and their effects on a nano-second pulse have been investigated

COMPARISON OF A SIERPINSKI GASKET MONOPOLE ANTENNA TO BOW-TIE ANTENNAS BASED OFF THE FRACTAL ITERATIVE SHAPES

Antennas are an integral part of mobile devices. Recently, the demand for smaller phones has increased requiring smaller components within the device. This leads to problems with performance and limitations of RF systems within mobile devices including antennas which have been affected by the size thus affected frequency output. In this thesis, fractal theory will be utilized to compare the performance of the Sierpinski Gasket Monopole antenna to single band antennas to see if this is a viable substitute in mobile applications. By utilizing simulations and physical antennas, the performance will be observed at each frequency band and compared

High-resolution sub-millimetre diameter side-viewing all-optical ultrasound transducer based on a single dual-clad optical fibre

All-optical ultrasound (OpUS), where ultrasound is both generated and received using light, has emerged as a modality well-suited to highly miniaturised applications. In this work we present a proof-of-concept OpUS transducer built onto a single optical fibre with a highly miniaturised lateral dimension (0.4 MPa and a corresponding bandwidth >27 MHz. Concurrent ultrasound generation and reception from the transducer enabled imaging via motorised pull-back allowing image acquisition times of 4 s for an aperture of 20 mm. Image resolution was as low as ~50 µm and 190 µm in the axial and lateral extents, respectively, without the need for image reconstruction. Porcine aorta was imaged ex vivo demonstrating detailed ultrasound images. The unprecedented level of miniaturisation along with the high image quality produced by this device represents a radical new paradigm for minimally invasive imaging