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In this paper, we propose a 915 MHz RF power emitter integrated with a 2×2 patch antenna array and four switchable reflection-type phase shifters with nominal phase delay of −90°, 0°, or +90°. For achieving the object detection function, a centered harmonic antenna at 1830 MHz is also integrated to identify the location of sensor by receiving the harmonic wave reflected from the sensor. In our experiment,...
In this paper, the characteristics of Reflectarray Antennas printed on convex curved surfaces are analyzed. In particular, results on the radiation performances of different Reflectarrays designed to be mounted on cylinders with different radii of curvature are presented and discussed.
The design of an X-band circularly polarized reconfigurable reflectarray antenna is presented. Elements with concentric dual split rings are mechanically rotated by micromotors to achieve phase reconfigurability with low cross-polarization and low element loss. Simulation results show that a maximum gain of 26.43 dB with aperture efficiency of 62.9% is achieved by a reflectarray with 15×15 elements...
Near-field focusing characteristics of transmitarray antennas are investigated. The design procedure is summarized and a Ku-band focused transmitarray antenna is presented where the elements are aperture-coupled patches interconnected with stripline delays. The focusing performance of the transmitarray is compared with classic far-field designs. It is shown that a near-field focused reflectarray can...
A novel architecture of high frequency resolution LC-tank based digitally controlled oscillator (DCO) is presented in this paper. The proposed architecture utilizes a differential tapped inductor and a capacitor array within the taps for fine frequency tuning. A prototype of 1.6 GHz DCO integrated in 0.18-μm CMOS technology exhibits a tuning range of 40.2% and a phase noise of −123.6 dBc/Hz@1MHz....
A wide band radio frequency (RF) root-mean-square (RMS) power detector (PD) is presented in this paper. A CMOS rectifier with unbalanced source-coupled pairs and auxiliary capacitors is utilized to constitute the reverse received signal strength indicator (reverse-RSSI) architecture as proposed power detector with operating frequency from 300 MHz to 10 GHz. The auxiliary capacitors are introduced...
In this paper, a 915-MHz RF-power emitter with an antenna array controlled by phase shifters is proposed to make directional energy beam point to the energy harvesting (EH) receiver. For the beamforming request, a 2×2 patch antenna array and tunable 360° reflection-type phase shifters are designed. Measurement results show the energy transmission efficiency can be improved by 3.9 times higher than...
The parabolic cylindrical antenna and its reflectarray counterpart are well known for enhanced beam steering capability in the focal plane. However, the radiation performance degrades significantly for wide scan angles, for instance gain dropping and beam broadening, due to increased phase errors. In this paper, by exploiting the phase controlling capabilities in reflectarrays, an improved reflectarray...
The feasibility of designing single-feed transmitarray antennas with simultaneous multiple beams is investigated in this paper. Different far-field pattern masks and fitness functions are studied for multi-beam designs, and phase synthesis is achieved using the particle swarm optimization technique. A quad-layer configuration using double-square rings is selected for the transmitarray elements, and...
Beam scanning performance of planar multifocal transmitarray antennas are investigated in this paper. The advantages of the proposed structure over conventional designs are first delineated, and then a Ku-band transmitarray antenna with quadrufocal phase distribution is designed using the particle swarm optimization technique for 60° scan coverage, which shows a good performance. The results presented...
Many transmitarray antennas are designed with multilayer frequency selective surface type elements. The goal of this paper is to present a multiple conductor layers transmitarray antenna using slot-type element with no substrate material. A quaternary-layer transmitarray antenna using cross-slot elements has been designed, fabricated, and tested for 11.3 GHz operating frequency. The measured gain...
In this paper, the advantages and recent developments of reflectarray antennas for space applications are reviewed. Basic requirements for space antennas, and the limitations and challenges of conventional designs are discussed. Various advantages of reflectarray antennas over reflectors and phased array antennas are reviewed and it is shown that reflectarray antennas can be a suitable low-cost choice...
The radar based UWB microwave imaging techniques have shown great potential for the localization of embedded dielectric targets in breast phantoms [1], [2]. In practical UWB microwave imaging systems, antennas play a key role in determining the characteristics of the received signals. The antennas behave as spatial-temporal filters as they have to radiate narrow pulses and thus the radiated signal...
This paper investigates the feasibility of designing conformal reflectarrays on cylindrical surfaces, which provides insight into many radiation characteristics of conformal reflectarrays. A general array theory formulation is described that can be applied to any conformal reflectarray geometry. Convex and concave surfaces are studied and the radiation patterns, directivity, and bandwidth of these...
We use time reversal microwave imaging to detect and classify benign and malignant breast cancer lesions in numerical phantoms. We employed Time Reversal MUSIC (TR MUSIC) method to detect breast tumors in the presence of adipose and fibroglandular breast tissues. The classification of tumors is made based on the analysis of singular values of the multistatic matrix. We consider two different bands...
Minimum spanning tree is a classical problem in graph theory that plays a key role in a broad domain of applications.This paper proposes a minimum spanning tree algorithm using Prim's approach on Nvidia GPU under CUDA architecture. By using new developed GPU-based Min-Reduction data parallel primitive in the key step of the algorithm, higher efficiency is achieved. Experimental results show that we...
Latch based arrays are commonly used as small embedded memories. There are often a large number of such memories in a design. Due to the large area overhead of memory BISTs, scan is often used to test such memories. In this paper we show that with a minor modification of a marching sequence targeting only the transition delay faults at the latch boundaries, a comprehensive set of faults can be detected...
In this paper we investigate single-feed multi-beam reflectarray antenna designs. The direct method of superposition of beams is compared with the alternating projection method. The implementation of the alternating projection method for multi-beam performance is discussed. Also the effects of limited phase range and quantized phase values are integrated into the alternating projection method to minimize...
Reflectarray antennas are composed of phased elements to mimic conventional curved reflectors. An important step of the reflectarray antenna design is the selection of array elements, whose performance strongly determines the system behavior. This paper compares the bandwidth, fabrication tolerance, and design flexibility characteristics of several types of elements for Ka-band operation. Based on...
In this paper, we propose an UWB based multi static imaging technique which seeks to produce images and localize malignant breast tissues by processing the backscattered ultra-wideband (UWB) signals from numerical models of both tumor and normal breast tissues. We demonstrate that standard capon beamforming (SCB) combined with time-of-arrival (TOA) could give some reasonable results for imaging and...
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