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In this work, a chipless tag antenna employing retro-reflective array for ultrawideband radio-frequency identification (UWB-RFID) application is demonstrated. Different from conventional RFID tags, by using retro-reflective antenna, the proposed antenna is not sensitive to its relative direction to the reader, leading to longer reading range in practice. Folded slots are etched in the transmission...
Reflectarray antennas have been widely used in communications and national defense because of their remarkable advantages such as high gain, low loss, low profile, and etc. In the design of reflectarray antennas, the relation between the reflection phase of every element and its dimensions is usually computed through element simulation with infinite periodic boundary conditions. However, this assumption...
Ill-posedness poses serious challenge to the community of inverse problems. Attention is focused on ill-posedness in electromagnetic inverse problems in this talk.
In millimeter wave imaging systems, a slight displacement in the system may cause great phase error because of its short wavelength. In addition, different working conditions and aging rate may also bring deviation of phase and amplitude in each channel. In this regard, channel calibration, especially phase calibration is critical for millimeter wave imaging system.
In this paper, a V-band low sidelobe and wideband series fed linear dielectric resonator antenna (DRA) array is proposed. Among many kinds of DRAs, the perforated rectangular dielectric resonator antenna (RDRA) is chosen as the antenna element in our design, which can enhance the impedance bandwidth by lowering down the quality factor. By optimizing the size of the slots and distance between adjacent...
A dual bands three elements printed sleeve dipole antenna array with beam direction at boresight direction has been developed for the application of IEEE 802.11 a/b/g. The size of sleeve dipole antenna array is 220mm in length, 8mm in width, and 0.4mm in thickness The beam direction always points at the boresight direction even if for various frequency operation.
Nowadays, the microwave technology offers the possibility to produce the cophasal pulses emitted from magnetrons. This technique allows to obtain the summation of the energy emitted from each radiating element of the antenna. Nevertheless, the geometry of antennas should be designed to reach the desirable characteristic of radiation and antenna gain of the antenna system. In the work the antenna system...
In this paper, two types of microstrip array antenna for radars operating at 77 GHz are presented. The first type of array antenna is 10×4 elements rectangular patch array antenna with overall size of 20.43mm×7.83 mm. Unit element of this antenna type is a rectangular patch. Series-fed column of 10 unit elements are arranged into 10 × 4 arrays by implementing simple power divider structure. The second...
In this letter, we proposed a new method to reduce mutual coupling of antenna array without adding additional space for the added structures, such as modified ground structure, metamaterial, and parasitic elements on the surface of antenna substrate. As an example, a compact two-element antenna array working at 5 GHz is designed. Two closed chip loop structures (CCLSs) around the two radiation patches...
Interest in Passive Radar has grown significantly over the last decade. However, most Passive Radar systems have been experimental set-ups tailored to a signal frequency band or a single illuminator. In this paper, the design considerations and the resulting Multiband Bistatic Passive Radar (MBPR) structure are described and the evaluations of various measurement campaigns with multioctaves array...
Low-profile, high-gain circularly polarized antennas are highly desired in modern space and communication systems because they not only reduce the size, weight, and cost of the communication system but also reduce polarization mismatch resulting from the multipath interference of wave propagation. Because of their low cost, simple structure, and good integration capability, microstrip patch antennas...
Inspired by the development of electromagnetic band-gap (EBG) structures and metamaterials, Fabry-Perot resonator antennas (FPRAs) have been well studied in the recent decade. Such antennas are mainly composed of a Fabry-Perot resonant cavity and excited by a normal small antenna or an antenna array. A ground plane and a partially reflective surface (PRS) form the Fabry-Perot cavity. The advantages...
A shaped power pattern synthesis with reduction of dynamic range ratio (DRR) is presented in this paper. Controlling the DRR of the excitations for the shaped power pattern synthesis is very useful since it can reduce the output power loss and also simplifies the complexity of the feeding network design. The synthesis of shaped pattern is typically a nonconvex optimization problem. To solve this problem...
Planar quasi-periodic arrays are widely used in many electromagnetic devices, such as reflectarray antennas, metasurfaces, nano particle arrays, and etc‥ They can be modeled as elements with geometrical control parameters located at periodic locations. Modeling quasi-periodic arrays are more challenging compared with periodic arrays. The entire array is required during the modeling process due to...
In this paper, to detect and manage Unmanned Aerial Vehicles (UAVs), a passive radar array system is discussed to receive and process the Orthogonal Frequency Division Multiplexing (OFDM) echoes of UAV, which are originally transmitted by the nearby base stations. A uniform circular array is employed to receive the echoes whose model is introduced. To handle the echoes, a signal processing subsystem...
There could be all kinds of errors in the space-borne active array antenna because of its features such as highly integrated, complex configuration, strong mutual coupling and other factors. Obviously, these errors will affect the performances of array antenna. To address this issue, various methods have been proposed to calibrate these errors to guarantee the performance of the entire array.
Radial Line Slot Antennas (RLSAs) are well known as a high gain, high efficiency planar slotted array antennas. Due to its high gain characteristic, low losses, high efficiency and compact structure, RLSA has been proposed for satellite communications to substitute the conventional parabolic antennas. Several structures where studied previously, mainly operating in C-band with a huge number of slots...
In this paper, a new method of designing dual frequency beam reconfiguration reflectarray antenna is proposed. The dual resonant reflection unit cell which is composed of double dipole patch printed on grounded dielectric substrate is implemented to construct the reflectarray. And a slotted waveguide arrays is utilized to be the feed of the antenna, it provides an approximate cylindrical wave in its...
Millimeter wave Near-field 3-D imaging has great importance on security applications for its penetrating characteristics and the 3-D information of the target. To obtain accurate and high resolution images, we propose a direct 3-D integral method to reconstruct the 3-D images. The algorithm directly processes the scattered data without any interpolation or approximation, making it more accurate than...
In this paper, we propose the design of in-plane focus reflector antennas (IFRA) based on phase gradient metasurface (PGM). The in-plane focus is achieved by using PGM with large in-plane phase gradient, which can couple normally incident waves efficiently into surface waves along the surface. This is different from conventional reflector antennas and reflectarray antennas, where the focus lies above...
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