Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 18 of 18 for “"frequency agile"”.
-
Threat and Application of Frequency-Agile Radio Systems
… wireless systems that only operate on fixed frequency bands are reaching their capacity limits, advanced frequency-agile radio systems are developed for more efficient spectrum utilization. For example, white space radios dynamically leverage locally unused TV channels to provide high-speed …
-
Cross-Layer Optimization and Distributed Algorithm Design for Frequency-Agile Radio Networks
Recent advancements in frequency-agile radio technology and dynamic spectrum access network have created a huge space for improving the utilization efficiency of wireless spectrum. Existing algorithms and protocols, however, have not taken full advantage of the new technologies due to obsolete …
-
Photorefractives for fast optics
… been developed that are<br/>suitable for use as frequency agile optical filters and exhibit greater contrast ratios<br/>than previous passive photorefractive materials. Small signal gain co-efficients of up<br/>to 1600cm-1 are demonstrated in these hybrid devices, compared to less than …
-
Measuring Noise in the VHF Band and Its Effect on Low SNR Signal Detection
… demand for access to the crowded radio frequency spectrum, cognitive radios have been suggested as one solution. Cognitive radios would be frequency agile and able to sense their radio environment and opportunistically use empty spectrum. Spectrum sensing, monitoring a given band of …
-
Tunable microwave filters using ferroelectric thin films
Frequency agile microwave devices based on Barium Strontium Titanate (BST) thin films have gained a lot of interest in recent years. The frequency agility of the ferroelectric devices is based on the external DC electric field controlled permittivity of BST thin film. In this research work, several …
-
Low-cost electromagnetic tagging : design and implementation
Several implementations of chipless RFID (Radio Frequency Identification) tags are presented and discussed as low-cost alternatives to chip-based RFID tags and sensors. An overview of present-day near-field electromagnetic tagging is presented, including both chip-based and chipless technologies …
-
Monolithic RF frontends for ubiquitous wireless connectivity
… implications for the energy efficiency, frequency range and sensitivity of the radio. Ubiquitous connectivity requires bringing online previously unconnected, closed-circuit systems. Case in point, the recently ratified 802.11p standard targets wireless access in vehicular environments. …
-
A wireless sensor network for smart roadbeds and intelligent transportation systems
… sensor. The radio transmitters in the sensor are frequency-agile, and the sensors use a randomized sparse TDMA protocol, which allows several transmit-only devices to share a channel. The sensor package includes a custom-designed, compact, broadband, inexpensive printed circuit microstrip antenna …
-
New Concepts in Front End Design for Receivers with Large, Multiband Tuning Ranges
… very large tuning ranges, which is important for frequency-agile cognitive radio, surveillance, and other applications requiring wideband or multiband monitoring. Direct conversion architecture is gaining popularity due to the recent advancements in CMOS--based RFIC technology. The possibility of …
-
Design and Implementation of An Emulation Testbed for Optimal Spectrum Sharing in Multi-hop Cognitive Radio Networks
… of reconfiguring RF and switching to desired frequency bands. It is a frequency-agile data communication device that is vastly more powerful than existing multi-channel multi-radio (MC-MR) technology. In this thesis, we investigate the important problem of multi-hop networking with CR nodes. …
-
Embedded Software-Defined Radio Architectures for 6G Cellular Networks
… multi-GHz instantaneous signal bandwidths, frequency agile radio architectures covering multi-octave frequency ranges, and highly sensitive receivers. To support these requirements, software-defined radios (SDR) are becoming an essential building block of next-generation radio networks. This …
-
The design and realisation of electronically tunable dielectric resonator microstrip filters
… particularly those operating in the microwave frequency range, have a growing demand for highly selective and frequency agile filters with fast tuning rates. At microwave frequencies above 2GHz, filters that combine both tuning speed and high selectivity are difficult to realise. Unloaded Q …
-
Planar groove gap waveguides
… to an SIW resonator on the same substrate and frequency band. This work further explores the DC isolation property of the PGGWG by presenting electrically tunable PGGWG resonant cavities. It is found that a simple biasing network can be applied to the cavity using a varactor diode to vary the …
-
Design and analysis of an electrically small inductively loaded sector antenna for frequency reconfiguration using varactor diodes
… an inductively loaded, electrically small, frequency reconfigurable, sector antenna that covers most consumer frequency bands has been developed. This thesis details the design and characterization of the antenna element, which tunes the GSM 900, GSM 1800, 3G, WiFi, and WiMAX bands. The …
-
Wide Bandwidth Control Electronics For Gan-Based Pebbs
… and low-power applications. The lack of high-frequency drivers is one of the factors preventing their application to power converters. In order to make GaN devices applicable in power electronics and best exploit the capabilities and advantages of these devices, this dissertation presents a …
-
Construction of FASR subsystem testbed and application for solar burst trajectories and RFI study
The construction of the Frequency Agile Solar Radiotelescope (FASR) Subsystem Testbed (FST) and observational results are described. Three antennas of Owens Valley Solar Array (OVSA) have been upgraded with newly designed, state of art technology. The 1-9 GHz RF signal from the antenna feed is …
-
From high power terahertz quantum cascade lasers to terahertz light amplifiers
The terahertz (THz) frequency range (300 GHz to 10 THz, wavelength 30-1000 [mu]m), despite having many potential applications, is technologically relatively underdeveloped mainly because of the lack of suitable coherent radiation sources when compared with nearby electromagnetic radiation spectrum. …