7,635 research outputs found
A novel design for an RF MEMS resistive switch on PCB substrate
No full textCopyright @ 2008 Stimulation Action on MEM
Misturador CMOS de 2,4GHz para conversão a baixas frequências operando em inversão moderada
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Elétrica, Florianópolis, 2009O objetivo deste trabalho é desenvolver um misturador ativo para conversão de um sinal de RF de 2,4GHz em um sinal de frequência intermediária 750kHz. A topologia escolhida foi a do misturador ativo de balanceamento simples uma vez que apresenta uma arquitetura simples, alto ganho de conversão e um bom isolamento entre as portas. A tecnologia CMOS utilizada foi o AMS 0,35?m que apresenta dispositivos de RF bem caracterizados e bem documentados e também oferece uma prototipagem de baixo custo. O estágio de entrada opera com o nível de inversão moderado e o transistor com uma fT de 16GHz. O misturador simulado apresenta impedância de saída de 403W, ganho de 11dB, figura de ruído em 16,3dB, ponto de compressão de 1dB em -8,76dBm e consumo de potência de 7,3mW
Automated detection of prostate cancer using wavelet transform features of ultrasound RF time series
No full textThe aim of this research was to investigate the performance of wavelet transform based features of ultrasound radiofrequency (RF) time series for automated detection of prostate cancer tumors in transrectal ultrasound images. Sequential frames of RF echo signals from 35 extracted prostate specimens were recorded in parallel planes, while the ultrasound probe and the tissue were fixed in position in each imaging plane. The sequence of RF echo signal samples corresponding to a particular spot in tissue imaging plane constitutes one RF time series. Each region of interest (ROI) of ultrasound image was represented by three groups of features of its time series, namely, wavelet, spectral and fractal features. Wavelet transform approximation and detail sequences of each ROI were averaged and used as wavelet features. The average value of the normalized spectrum in four quarters of the frequency range along with the intercept and slope of a regression line fitted to the values of the spectrum versus normalized frequency plot formed six spectral features. Fractal dimension (FD) of the RF time series were computed based on the Higuchi's approach. A support vector machine (SVM) classifier was used to classify the ROIs. The results indicate that combining wavelet coefficient based features with previously proposed spectral and fractal features of RF time series data would increase the area under ROC curve from 93.1% to 95.0%, respectively. Furthermore, the accuracy, sensitivity, and specificity increases to 91.7%, 86.6%, and 94.7%, from 85.7%, 85.2%, and 86.1%, respectively, using only spectral and fractal features. [ABSTRACT FROM AUTHOR]Peer reviewedFinal article publishe
An RF-Powered DLL-Based 2.4-GHz Transmitter for Autonomous Wireless Sensor Nodes
No full textThis paper presents the system and circuit design of a compact radio frequency (RF)-powered 2.4-GHz CMOS transmitter (TX) to be used for autonomous wireless sensor nodes (WSNs). The proposed TX utilizes the received dedicated RF signal for both energy harvesting as well as frequency synthesis. A TX RF carrier is derived from the received RF signal by means of a delay locked loop and XOR-based frequency multiplier. The 50-Ω load is subsequently driven by a tuned switching RF power amplifier (PA) with 25% duty cycle input for high global efficiency. The design is fabricated in 40-nm CMOS technology and occupies a die area of 0.16 mm2. Experimental results show a rectifier with 36.83% peak efficiency and power management circuit with 120-nA current consumption that enables a low start-up power of -18.4 dBm. The TX outputs a continuous 2.44-GHz RF signal at -2.57 dBm with 36.5% PA drain efficiency and 23.9% global efficiency from a 915-MHz RF input and supports ON-OFF keying modulation.Accepted Author ManuscriptBio-Electronic
A Wideband 2x13-bit All-Digital I/Q RF-DAC
No full textThis paper presents a wideband 2 13-bit in-phase/quadrature-phase (I/Q) RF digital-to-analog converter-based all-digital modulator realized in 65-nm CMOS. The isolation between I and Q paths is guaranteed employing 25% duty-cycle differential quadrature clocks. With a 1.3-V supply and an on-chip power combiner, the digital I/Q transmitter provides more than 21-dBm RF output power within a frequency range of 1.36–2.51 GHz. The peak RF output power, overall system, and drain efficiencies of the modulator are 22.8 dBm, 34%, and 42%, respectively. The measured static noise floor is below 160 dBc/Hz. The digital I/Q RF modulator demonstrates an IQ image rejection and local oscillator leakage of 65 and 68 dBc, respectively. It could be linearized using either of the two digital predistortion (DPD) approaches: a memoryless polynomial or a lookup table. Its linearity is examined using single-carrier 4/16/64/256/1024 quadrature amplitude modulation (QAM), as well as multi-carrier 256-QAM orthogonal frequency-division multiplexing baseband signals while their related modulation bandwidth can be as high as 154 MHz. Employing DPD improves the third-order intermodulation product (IM3) by more than 25 dB, while the measured error vector magnitude for a “single-carrier 22-MHz 64-QAM” signal is better than 28 dB.Microelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
Bracelet+: Harvesting the Leaked RF Energy in VLC with Wearable Bracelet Antenna
No full textVisible Light Communication (VLC) is widely considered a promising technology for the coming 6G networks. Recent studies show that a VLC transmitter not only emits visible light signals but also leaks RF signals during the transmission. In this work, we devote effort to harvesting the free leaked RF energy from VLC transmissions. We observe that the surrounding objects could help a coil antenna harvest significantly more RF energy. Based on this observation, we propose our system Bracelet+, which involves the human body in the harvesting system to increase the harvested power. After careful analysis of the influence of the human body on the harvested power, we prototype the coil antenna as a bracelet that achieves both high harvested power and convenience for wearing. The average power of the RF energy harvested by our design is 10 larger than that of the conventional coil antenna, without causing any interference to the communication of VLC systems. The harvested power can reach up to micro-watts in our tested scenarios. Such a micro-watt level of harvested energy has the potential to power up ultra-low-power sensors such as temperature sensors and glucose sensors.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Embedded System
Single Channel RF Signal Recovery for Nyquist Folding Receiver
No full textThis paper presents a method for exploiting wideband spectral information of real-valued radio frequency (RF) signals using the Nyquist Folding Receiver architecture. A new system model based on a symmetric modulation matrix is introduced so that the frequency band of the real input signals can be estimated without in-phase and quadrature reception and processing. To recover the original frequency of the input RF signal, we use the parameter-free sparse learning via iterative minimization (SLIM) method. Finally, the proposed model and the success of the recovery algorithm are demonstrated with data collected from an experimental testbed.Accepted Author ManuscriptMicrowave Sensing, Signals & System
Diminazene Protects Corpus Cavernosum Against Hypercholesterolemia-Induced Injury
No full textIntroductionAngiotensin-converting enzyme 2 (ACE2) is a key enzyme of the renin angiotensin system, which breaks down angiotensin II and forms angiotensin-(1-7). In erectile tissues, it has been documented that angiotensin II contributes to the development of erectile dysfunction (ED), while treatment with angiotensin-(1-7) improves penile erection. However, the expression and function of ACE2 in erectile tissues have never been investigated. AimHere, we examined the expression of ACE2 in erectile tissues and its actions against hypercholesterolemia-induced corpus cavernosum (CC) injury. MethodsHypercholesterolemic apolipoprotein E knockout (ApoE(-/-)) mice, a well-known model of ED, were treated with diminazene aceturate (DIZE), an ACE2 activator compound, or vehicle for 3 weeks. Reactive oxygen species (ROS), collagen content, and protein expression of ACE2, neuronal nitric oxide synthase (nNOS), endothelial nitric oxide synthase (eNOS), nicotinamide adenine dinucleotide phosphate-oxidase (NADPH) subunits were evaluated in the penis of DIZE-treated and untreated ApoE(-/-) mice. Functional studies were performed in CC strips. Main Outcome MeasuresACE2 expression and its role in modulating nitric oxide (NO)/ROS production and fibrosis within the CC of hypercholesterolemic mice were the main outcome measures. ResultsACE2 was expressed in smooth muscle and endothelial cells of mouse CC. Interestingly, ACE2 was downregulated in penis of hypercholesterolemic mice with ED, suggesting a protective role of ACE2 on the CC homeostasis. In accordance with that, pharmacological ACE2 activation by DIZE treatment reduced ROS production and NADPH oxidase expression, and elevated nNOS and eNOS expression and NO bioavailability in the penis of ApoE(-/-) mice. Additionally, DIZE decreased collagen content within the CC. These beneficial actions of DIZE on the CC were not accompanied by improvements in atherosclerotic plaque size or serum lipid profile. ConclusionACE2 is expressed in erectile tissue and its reduction is associated with hypercholesterolemia-induced ED. Additionally, treatment with DIZE improved hypercholesterolemia-induced CC injury, suggesting ACE2 as a potential target for treating ED. Fraga-Silva RA, Costa-Fraga FP, Montecucco F, Sturny M, Faye Y, Mach F, Pelli G, Shenoy V, da Silva RF, Raizada MK, Santos RAS, and Stergiopulos N. Diminazene protects corpus cavernosum against hypercholesterolemia-induced injury. J Sex Med 2015;12:289-302.LHT
Caracterização em frequência de relés RF com uma bobina
No full textMestrado em Engenharia Electrónica e TelecomunicaçõesShort-Open-Load-Thru (SOLT) e Thru-Re
ect-Line (TRL) são as duas
técnicas de calibração mais utilizadas na correcção de erros aplicada em
Vector Network Analyzers (VNA). No entanto, alguns requisitos têm
que ser cumpridos, de modo a permitir a aplicação destas técnicas de
calibração em medições realizadas em placas de teste. Esta dissertação
destina-se a caracterização em frequência de dispositivos inseridos em
placas de teste, mais especificamente de relés electromecânicos de
bobina única para aplicações em frequências rádio (RF) e microondas.
As técnicas de calibração SOLT e TRL são inicialmente estudadas
de modo a perceber os seus requisitos e limitações. De seguida,
desenvolve-se e apresenta-se o desenho de standards de calibração personalizados
em placas de teste. Por fim, para cada técnica de calibração, procede-se a caracterização em frequência de relés RF de
bobina única e comparam-se os resultados obtidos com as curvas de
desempenho típicas apresentadas pelo fabricante.Short-Open-Load-Thru (SOLT) and Thru-Re
ect-Line (TRL) are the
two most common calibration techniques for the error correction applied
on Vector Network Analyzers (VNA). These techniques however
are not so straight forward when it comes to in- xture measurements.
This dissertation is aimed at the frequency characterization of in- xture
devices, speci cally single coil electromechanical relays for radio frequency
(RF) and microwave applications. The SOLT and TRL calibration
techniques are rst studied to understand the limitations and
requirements each technique. Then the design of custom in- xture
calibration standards is developed and presented for each technique.
Finally, the single coil RF relays are characterized for each calibration
technique and the results are compared with the typical performance
presented on the datasheet
Indoor RF positioning system
No full textThe purpose of this project is to develop an indoor radio frequency (RF) positioning system to track the position of a device within centimeters accuracy.
Unlike the Global Positioning System (GPS), the RF positioning system does not communicate with satellites in order to determine a specific location.
Instead, the RF positioning system utilizes tracking tags and anchors to track devices in indoor spaces. The ultra-wideband (UWB) technology enables the
DMW1000 transceiver chip to calculate the precise real-time indoor location within 10 cm of accuracy. The accurate position of a device containing the tracking tag will be calculated by measuring the distance between the anchors and the tracking tags. Overall, implementing this positioning system in a device will resolve the issue of precise, real-time tracking being inaccessible in indoor spaces
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