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A microwave cavity is proposed for hyperthermia treatment investigations. The cavity comprises a printed monopole antenna radiating inside a copper-shielded culture dish. The temperature of the enclosed medium can be controlled through the intensity and duration of the antenna's microwave radiation. A heating experiment is carried out, showing a temperature increase of 34°C (from 16°C to 50°C) within...
Reconfigurability is a vital feature of future RF, millimeter Wave and terahertz systems for sensing, imaging, wireless, and satellite communications. Indeed significant efforts have been devoted to develop tunable systems in the past among them are RF MEMS switches. But, in practice, these solutions have not been widely implemented due to a need for high voltage actuation, lack of flexibility for...
We present a tuning strategy for electrically small antennas that have high reactive parts and are suitable for small PDA devices. Our approach is to first bring the small antenna to resonance by minimizing the reactive part of the impedance prior to matching. To verify this concept, a spiral antenna is used for operation in the 800–1200MHz frequency range. The matching network is a reconfigurable...
A Medical Sensing Body Area Network (MS-BAN) is designed and tested to connect with a lung-imaging sensor. The proposed MS-BAN can add wireless connectivity to a variety of other sensors. It is demonstrated that a wireless connection platform along with a RF power detector circuit can be used in conjunction with a lung-imaging sensor to provide deep tissue sensing and communication.
Past efforts on reconfiguration focused on modifying the antenna bandwidth by shifting the aperture's frequency response using switches or piezoelectric materials. By contrast, this paper proposes bandwidth reconfiguration by starting with a wideband aperture and limiting its original bandwidth by modifying the array feed. The initial un-configured design provides 9.25∶1 bandwidth for a VSWR 3∶1 or...
We propose a reconfigurable terahertz (THz) filter using frequency selective surfaces (FSS) combined with vanadium dioxide (VO2) phase change materials (PCMs) integrated with micro-heater for THz applications. The integration of novel material and micro-heater with our FSS design enables simultaneous control of temperature and conductivity of the PCM film leading to transmittance profile control of...
We present a dual polarized Tightly Coupled Dipole Array (TCDA), representing the first practical realization of dual polarizations using a TCDA topology. This is accomplished through a dual-offset, split unit cell with minimized inter-feed coupling. The array achieves a minimum 6.1∶1 bandwidth for VSWR<2.25, 2.5, and 3.9 for 0°, 30°, and 60° scans, respectively. To our knowledge, this implies...
We present a low-profile ultra wideband slot spiral antenna on a hybrid EBG-based reflecting cavity. A unique aspect of the proposed hybrid EBG impedance surfaces is its wide bandwidth performance via constructive interference of the ground plane with the antenna. This characteristic leads to highly improved axial ratio performance as compared to spirals on a metallic ground plane cavity. The proposed...
Characteristic modes are used to design a multi-antenna NVIS system on-board an electrically small UAV. By analyzing the radiation eigenmodes of the UAV platform, optimal NVIS patterns are constructed, and mounting locations which maximize desirable antenna-platform coupling are identified. The optimal NVIS pattern is then approximated using discrete monopole antennas as feeding elements. The excitation...
Wideband dual polarized omni-directional antenna is proposed. The design includes concentric ring and monopole antennas, placed over a square ground plane. Both of the antennas retain 10dB return loss across the 1.65 – 2.7 GHz range. Of importance is that port isolation is 70dB across the frequency band of interest in spite of collocation of antennas. The overall antenna dimensions are 4cm × 18cm...
Generation of terahertz signals using solid-state devices has yet to be demonstrated above 1 THz. This paper presents modeling and optimization of a plasma mode High Electron Mobility Transistor (HEMT) for operation beyond 3 THz. In designing this structure, we examine geometrical and electrical parameters and their impact on the resonance frequency. Preliminary results show that as much as 20% of...
Recently, a novel receiver architecture with on-site coding was proposed to reduce the number of analog-to-digital converters behind antenna array elements. To realize digital beamforming using this receiver, it is important to faithfully recover the phase difference between adjacent signal paths at the digital baseband. In this paper, the impact of on-site coding on the phase error is examined for...
Highly coupled antennas are difficult to match due to their large reactive loading. In this paper, the input impedance of a two port highly coupled antenna is matched to develop a miniature antenna pair. This work is particularly useful for biomimetic antenna arrays that are highly coupled, and experience tradeoffs in available output power and isolation. The matching technique entails use of an adjustable...
A design approach is presented for UHF RFID tag antennas operating in the vicinity of dielectric media using the layered Green's function and the effective permittivity of a material with finite thickness. It is noted that materials detune the antenna and alter the gain pattern. In this work we propose a broadband tag antenna design that functions on materials across various permittivity and thicknesses...
Tuning circuits are often used for electrically small antennas. However, the nearby environment can detune the matching calling for adaptive tuning. In this paper we present a new concept to adaptively tune matching circuits using a near-field probe that samples the instantaneous radiated power. For an electrically small VHF/UHF antenna, it is shown that a properly designed near-field probe is capable...
Recent efforts on tightly-coupled dipole arrays (TCDA) have yielded conformal, low profile designs that demonstrate remarkable bandwidths. In [1], a TCDA with integrated balun (TCDA-IB) and substrate loading was presented. In the current paper, we extend this work to a dual-polarization TCDA that scans up to 45°. It exhibits an infinite array bandwidth of 13.5∶1 (290MHz–3.9GHz) with an active VSWR<3...
There has been growing interest in all-electronic sources in the terahertz frequencies. A compact THz source is obtainable, if plasma-oscillations in the 2DEG of a high electron mobility transistor (HEMT) are utilized. With this goal in mind, we develop a numerical tool which models such oscillations. We use hydrodynamic equations to model drifting plasma in the 2DEG, whereas the surrounding environment...
We propose phase-change materials (PCMs) to demonstrate the reconfigurablility of THz filter. Here vanadium dioxide (VO2) is studied since it shows insulator-to-metal transition properties at temperature of 70 °C. A broadband ON/OFF filter using frequency selective surfaces (FSS) integrated with VO2 is designed to improve selectivity of THz sensing devices. Simulation and measurement results show...
Millimeter wave and terahertz band antennas are of growing interest due to applications in radar, imaging and communications. Specifically, circularly polarized (CP) antennas find special interest in satellite communications and applications involving mobile transceivers. For mm-Wave and THz band, gain characterization for CP antennas is a difficult task due to phase errors in alignment. To avoid...
A new concept of using near-field probes to detected radiated power for feedback in adaptive tuning systems is presented. As the probe is in the near field, it samples both stored reactive energy, as well as far field radiated energy. As such, specific principals must be considered for proper design. It is shown that for an electrically small VHF/UHF antenna a properly designed near-field probe is...
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