Systems and Communications Commons^™

Pre-Amplifiers For A 15-Tesla Magnetic Resonance Imager, Chin-Leong Lim, Peter Serano, Jerome L. Ackerman

Chin-Leong Lim

High-field magnetic resonance imagers (MRI) give better signal-to-noise ratio (SNR) and image contrast. However clinical MRIs are currently limited to 3 Tesla (T) magnetic field strength. To create an uncommon 15 T scanner for research use, we evaluated several low-cost, intended for wireless communication, GaAs enhancement-mode pseudomorphic high electron mobility transistors (ePHEMT) in the critical preamplifier slot. This paper reports the experimental results that were obtained at both module and system levels. When evaluated in our prototype 15 T scanner front-end’s preamplifier slot, the candidate devices’ sub 1dB noise figures enabled image SNR ~ 110 in a water phantom (test …

Limiting And Transient Performances Of A Low Loss Pin-Schottky Limiter, Chin-Leong Lim

Chin-Leong Lim

The main cause of loss in the PIN-Schottky limiter is the diodes’ parasitic capacitances. Techniques to counter the parasitic capacitances include using bare chip, air cavity packaging, diode stacking, mesa construction, isolating the Schottky diode from the signal path and connecting the diodes to a low impedance node. But the aforementioned techniques either sacrifice cost, manufacturability, size, performances or thermal ruggedness. To reduce loss in the PIN-Schottky limiter, we re-configured its parasitics into a low pass ladder network. This paper reports on the new configuration’s changed large signal and transient performances. We observed improved isolation at 0.9 and 2.4 GHz, …

Efficient Superposition Of Communication And Radar Waveforms (Raytheon), Anton Frolenkov, Vidie Pong, Sasha Sproch, Amy Whitcombe

Sasha A Sproch

The goal of the Raytheon-Olin SCOPE team was to identify pairs of communication and radar waveforms that could be superimposed through a single nonlinear amplifier while still fulfilling primary communications and radar functions. The team investigated candidate performance using hardware experimentation and industry-standard simulation. The results of this study begin to define the conditions for successful simultaneous communications and radar transmission through a single non-linear amplifier.

Balanced Uhf Lna Simplifies Cell Towers, Chin-Leong Lim

Chin-Leong Lim

Cellular basestations' low noise amplifiers (LNA) must have input impedances that are closely matched to the antennas. Unfortunately, the amplifier devices cannot be conjugate matched without sacrificing their noise performances. Current solutions such as the isolator and the balanced LNA can satisfactorily solve the matching problem but at the expense of increased cost, weight and size. On the other hand, the confined space atop cellular towers makes the current solutions unattractive. To shrink the balanced LNA for cellular infrastructure service, we pair a highly integrated dual-amplifier MMIC with miniature multilayer couplers. This MMIC also achieves the distinction of being the …

Brief Comparison Between 8051 And Avr, Ata Jahangir Moshayedi

Ata Jahangir Moshayedi

Brief comparison between 8051 and AVR

Innovation, Proximity, And Knowledge Gatekeepers –Is Proximity A Necessity For Learning And Innovation?, Deogratias Harorimana Dr

Dr Deogratias Harorimana

Organisational desire for innovation and growth can be best achieved when they are in proximity. Geographical or technological proximity represent network structure in which a focal organisation is embedded, which has structural, cognitive and relational dimensions. Proximity influences innovation indirectly by its influence on agents’ ability to exchange and combine knowledge in four related ways: by giving access to exchange partners that provide opportunities for learning, increasing the anticipation of value, increasing the motivation to exchange, and by giving access to resources necessary for committing exchanges.

National Infrastructure Protection Priorities For Nuclear Electromagnetic Pulse (Emp) And Solar Storm Geomagnetic Disturbance Catastrophes, George H. Baker Iii

George H Baker

The Commission to Assess the Threat to the United States from Electromagnetic Pulse Attack has provided a compelling case for protecting civilian infrastructure against the effects of EMP and geomagnetic disturbances (GMD) caused by severe solar storms. Similar to protecting critical infrastructure against any hazard, it will be important to take a risk-based priority approach for these two electromagnetic threats, recognizing that it will be fiscally impracticable to protect everything. In this regard, EMP and GMD are particularly challenging in that they interfere with electrical and electronic data, control, transmission, and communication systems organic to nearly all critical infrastructures, simultaneously, …

Adaptive Control Of Apache Web Server, Erik Reed, Abe Ishihara, Ole J. Mengshoel

Ole J Mengshoel

Wireless Transmission Network : A Imagine, Radhey Shyam Meena Engineer, Neeraj Kumar Garg Asst.Prof

Radhey Shyam Meena

World cannot be imagined without electrical power. Generally the power is transmitted through transmission networks. This paper describes an original idea to eradicate the hazardous usage of electrical wires which involve lot of confusion in particularly organizing them. Imagine a future in which wireless power transfer is feasible: cell phones, household robots, mp3 players, laptop computers and other portable electronic devices capable of charging themselves without ever being plugged in freeing us from that final ubiquitous power wire. This paper includes the techniques of transmitting power without using wires with an efficiency of about 95% with non-radioactivemethods. In this paper …

Battery Energy Storage System In Solar Power Generation, Radhey Shyam Meena Er., Deepa Sharma

Radhey Shyam Meena

Grid-connected solar PV dramatically changes the load profile of an electric utility customer. The expected widespread adoption of solar generation by customers on the distribution system poses significant challenges to system operators both in transient and steady state operation, from issues including voltage swings, sudden weather-induced changes in generation, and legacy protective devices designed with one-way power flow in mind

Balanced Amplifier Aims For Low Noise, Chin-Leong Lim

Chin-Leong Lim

Cellular basestations' low noise amplifiers (LNA) must have input impedances that are closely matched to the antennas. Unfortunately, the amplifier devices cannot be conjugate matched without sacrificing their noise performances. Current solutions such as the isolator and the balanced LNA can satisfactorily solve the matching problem but at the expense of increased cost, weight and size. On the other hand, the confined space atop cellular towers makes the current solutions unattractive. To shrink the balanced LNA for cellular infrastructure service, we pair a highly integrated dual-amplifier MMIC with miniature multilayer couplers. This MMIC also has the distinction of being the …

Low Mismatch Uhf Lna For Cellular Infrastructure, Chin-Leong Lim

Chin-Leong Lim

Cellular basestations' low noise amplifiers (LNA) must have input impedances that are closely matched to the antennas. Unfortunately, the amplifier devices cannot be conjugate matched without sacrificing their noise performances. Current solutions such as the isolator and the balanced LNA can satisfactorily solve the matching problem but at the expense of increased cost, weight and size. On the other hand, the confined space atop cellular towers makes the current solutions unattractive. To shrink the balanced LNA for cellular infrastructure service, we pair a highly integrated dual-amplifier MMIC with miniature multilayer couplers. This MMIC also achieves the distinction of being the …

Super-High-Frequency Two-Port Aln Contour-Mode Resonators For Rf Applications, Matteo Rinaldi, Chiara Zuniga, Chengjie Zuo, Gianluca Piazza

Matteo Rinaldi

This paper reports on the design and experimental verification of a new class of thin-film (250 nm) superhigh- frequency laterally-vibrating piezoelectric microelectromechanical (MEMS) resonators suitable for the fabrication of narrow-band MEMS filters operating at frequencies above 3 GHz. The device dimensions have been opportunely scaled both in the lateral and vertical dimensions to excite a contourextensional mode of vibration in nanofeatures of an ultra-thin (250 nm) AlN film. In this first demonstration, 2-port resonators vibrating up to 4.5 GHz have been fabricated on the same die and attained electromechanical coupling, kt^2, in excess of 1.5%. These devices are employed to …

On Spectrum Probing In Cognitive Radio Networks: Does Randomization Matter, Chao Chen, Zesheng Chen, Todor Cooklev, Carlos Pomalaza-Ráez

Todor Cooklev

In cognitive radio networks, dynamic spectrumaccess is achieved by allowing secondary users (SUs) to probethe spectrum and utilize available channels opportunistically.Spectrum probing mechanisms should be efficient and fast toavoid harmful interference with primary users (PUs). Periodicprobing has been commonly adopted as a default spectrumprobing mechanism. In this paper, we attempt to study differentspectrum probing mechanisms and evaluate a performance metriccalled the probing delay, i.e., how quickly a probing mechanismcan detect a channel change. We find that randomization in theprobing strategy does affect the probing delay. Specifically, in theindependent sensing scenario, periodic probing indeed achievesthe smallest probing delay. In the cooperative …

Uwb-Fsk: Performance Tradeoffs For High And Low Complexity Receivers, Todor Cooklev, Fernando Ramirez-Mireles, G. A. Paredes-Orozco

Todor Cooklev

In this work we explore flexible modulations toallow demodulation using receivers with different complexityand cost. More specifically, we study pulse-based ultrawideband (UWB) communications over channels with densemultipath effects using frequency shift keying (FSK) datamodulation. Our aim is to explore the performance tradeoffsbetween high and low complexity receivers. For this purposewe determine the performance of coherent, non-coherent andmismatched (e.g., non-coherent detection using templatesconsisting of a single path) demodulators. We take intoaccount the influence of the frequency response of the antennasystem and the effects of the frequency selectivity of themultipath channel. Given a specific channel condition, wederive expressions for the bit error …

Describing Radio Hardware And Software Using Owl For Over-The-Air Software Download, Todor Cooklev, Stanchev, David Clendenen

Todor Cooklev

Recently, several researchers have discovered the need for radios to use description techniques. Previous research describes information such as the current frequency band, waveform, and so on. However, this information is presented at a level that is not sufficient to determine software/hardware compatibility for over-the-air software download. For example, a device should not attempt to download a wideband waveform if its radio front-end is only narrowband, or if its baseband hardware cannot provide the required MIPS for the new waveform. Over-the-air software download is one of the most interesting features of software-defined radios. The compatibility between software and hardware prior …

Battery Energy Storage System In Solar Power Generation, Radhey Shyam Meena Er.

Radhey Shyam Meena

As solar photovoltaic power generation becomes more commonplace, the inherent intermittency of the solar resource poses one of the great challenges to those who would design and implement the next generation smart grid. Specifically, grid-tied solar power generation is a distributed resource whose output can change extremely rapidly, resulting in many issues for the distribution system operator with a large quantity of installed photovoltaic devices. Battery energy storage systems are increasingly being used to help integrate solar power into the grid. These systems are capable of absorbing and delivering both real and reactive power with sub-second response times. With these …

Connectivity Of Wireless Ad Hoc Networks: Impacts Of Antenna Models, Qiu Wang, Hong-Ning Dai, Qinglin Zhao

Hong-Ning Dai

This paper concerns the impact of various antenna models on the network connectivity of wireless ad hoc networks. Existing antenna models have their pros and cons in the accuracy reflecting realistic antennas and the computational complexity. We therefore propose a new directional antenna model called Approx-real to balance the accuracy against the complexity. We then run extensive simulations to compare the existing models and the Approx-real model in terms of the network connectivity. The study results show that the Approx-real model can better approximate the best accurate existing antenna models than other simplified antenna models, while introducing no high computational …

On Busy-Tone Based Mac Protocol For Wireless Networks With Directional Antennas, Hong-Ning Dai, Kam-Wing Ng, Min-You Wu

Hong-Ning Dai

The application of directional antennas in wireless ad hoc networks offers numerous benefits, such as the extended communication range, the increased spatial reuse, the improved capacity and the suppressed interference. However, directional antennas can cause new location-dependent carrier sensing problems, such as new hidden terminal and deafness problems, which can severely degrade the network performance. Recently, a few schemes have been proposed to address these problems. However, most of these existing methods can only partially solve the hidden terminal and deafness problems. Some of them even bring significant performance overhead. In this paper, we propose a novel MAC protocol, in …

Eavesdropping Security In Wireless Ad Hoc Networks With Directional Antennas, Qiu Wang, Hong-Ning Dai, Qinglin Zhao

Hong-Ning Dai

The eavesdropping security of wireless ad hoc networks has attracted considerable attention recently. However, most of current studies only consider OMN networks, where each node is mounted with a single omni-directional antenna, which radiates radio signals in all directions and consequently leads to the high eavesdropping possibility. Compared with an omnidirectional antenna, a directional antenna can concentrate the radio signals on some desired directions so that it can potentially reduce the eavesdropping possibility. This paper investigates the eavesdropping security of wireless ad hoc networks equipped with directional antennas. In particular, we study the eavesdropping possibility of OMN networks, SDA networks …

An Overview Of Using Directional Antennas In Wireless Networks, Hong-Ning Dai, Kam-Wing Ng, Min-You Wu

Hong-Ning Dai

Compared with omni-directional antennas, directional antennas have many merits, such as lower interference, better spatial reuse, longer transmission range and the improved network capacity. Directional antennas enable numerous emerging outdoor and indoor applications, which have been addressed in many recent studies. Despite the advances in wireless networks with directional antennas (DAWNs), there are many research challenges in all layers of DAWNs. This paper presents a detailed study on recent advances and open research issues on DAWNs. Firstly, we briefly introduce the classification of directional antennas, antenna radiation patterns, antenna modes as well as the challenges in the physical layer of …

Channel Allocation In Wireless Networks With Directional Antennas, Hong-Ning Dai, Kam-Wing Ng, Min-You Wu

Hong-Ning Dai

In this paper, we study the channel allocation in multi-channel wireless ad hoc networks with directional antennas. In particular, we investigate the problem: given a set of wireless nodes equipped with directional antennas, how many channels are needed to ensure collision-free communications? We derive the upper bounds on the number of channels, which heavily depend on the node density and the interference ratio (i.e., the ratio of the interference range to the transmission range). We construct several scenarios to examine the tightness of the derived bounds. We also take the side-lobes and back-lobes as well as the signal path loss …

On Eavesdropping Attacks In Wireless Sensor Networks With Directional Antennas, Hong-Ning Dai, Qiu Wang, Dong Li, Raymond Chi-Wing Wong

Hong-Ning Dai

The eavesdropping attack is a serious security threat to a wireless sensor network (WSN) since the eavesdropping attack is a prerequisite for other attacks. Conventional WSNs consist of wireless nodes equipped with omnidirectional antennas, which broadcast radio signals in all directions and are consequently prone to the eavesdropping attacks. Different from omnidirectional antennas, directional antennas radiate radio signals on desired directions and potentially reduce the possibility of the eavesdropping attacks. In this paper, we propose a model to analyze the eavesdropping probability in both single-hop WSNs and multihop WSNs with omnidirectional antennas and directional antennas. We verify the correctness of …