6,448 research outputs found
A novel design for an RF MEMS resistive switch on PCB substrate
No full textCopyright @ 2008 Stimulation Action on MEM
Dwight D. Eisenhower to Dillon Anderson, January 9, 1954
No full textEisenhower invites Anderson to an informal dinnerc|--
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TH r vvHrrk; h^>^ '^¦
January 9, 1954.
Dear Dillon:
This seems to be the day I am carrying on an extensive correspondence with you, but this letter has been planned for several weeks!
ome
informal stag dinner on the evening of Thursday, January twenty-first. I hope to gather together a small group.
mu
to attend if it is
possible for you to do so.
Because of the infornaality of the occasion, I suggest that
me
reasonably early dinner, and devote the evening to a general chat. While I am hopeful that you can attend, realize that you already naay have engagements which would interfere. If so, I .'assure you of my complete under standing.
I shall probably wear a black tie, but business suit will be entirely appropriate.
With warm personal regard,
Sincerely,
Mr. Dillon Anderson,
Esperson Building,
Houston, Texas
Radio Frequency (RF) Time-of-Flight Ranging for Wireless Sensor Networks
No full textPosition information of nodes within Wireless Sensor Networks (WSNs) is often a requirement in order to make use of the data recorded by the sensors themselves. On deployment the nodes normally have no prior knowledge of their position and thus a locationing mechanism is required to determine their positions. In this paper, we describe a method to determine the point-to-point range between sensor nodes as part of the locationing process. A two-way Time-of-Flight (TOF) ranging scheme is presented using narrow-band RF. The frequency difference between the transceivers involved with the point-to-point measurement is used to obtain a sub-clock TOF phase offset measurement in order to achieve high resolution TOF measurements. The ranging algorithm has been developed and prototyped on a TI CC2430 development kit with no additional hardware being required. Performance results have been obtained for the line-of-sight (LOS), non-line-of-sight (NLOS) and indoor condition. Accuracy is typically better than 7.0m RMS for the LOS condition over 250.0m and 15.8m RMS for the NLOS condition over 120.0m using a one-hundred sample average. Indoor accuracy is measured to 1.7m RMS using a 1000 sample average over 8.0m. Ranging error is linear and does not increase with increased transmitter-receiver distance. Our TOA ranging scheme demonstrates a novel system where resolution and accuracy are time dependent in comparison to alternative frequency dependent methods using narrowband RF
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
A comparative study of two blind FIR equalizers
No full textThe paper investigates blind finite-impulse-response (FIR) equalization schemes for quadrature amplitude modulation (QAM) signalling. We compare a bootstrap maximum a posteriori probability (MAP) equalizer with a recently introduced concurrent constant modulus algorithm (CMA) and decision directed (DD) equalizer (CMA+DD). Both equalizers are known to outperform the CMA considerably. The concurrent CMA+DD equalizer has a complexity that is slightly more than twice of the CMA, and the bootstrap MAP equalizer has computational requirements that are only slightly more complex than the CMA. Simulation results indicate that the bootstrap MAP blind FIR equalizer has a faster convergence rate than the concurrent CMA+DD blind FIR equalizer, but tuning of the former is more complicated than the latter
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
RF plasma polymerised thin films from natural resources
No full textPlasma polymerisation is an effective tool for fabrication of thin films from volatile organic monomers. RF plasma assisted deposition is used for one-step, chemical-free polymerisation of nonsynthetic materials derived directly from agricultural produces. By varying the deposition parameters, especially the input RF power, the film properties can be tailored for a range of uses, including electronics or biomedical applications. The fabricated thin films are optically transparent with refractive index close to that of glass. Given the diversity of essential oils, this paper compares the chemical and physical properties of thin films fabricated from several commercially exploited essential oils and their components. It is interesting to note that some of the properties can be tailored for various applications even though the chemical structure of the derived polymer is very similar. The obtained material properties also show that the synthesised materials are suitable as encapsulating layers for biodegradable implantable metals
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