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In this paper, a steerable isotropic circular array antenna is designed to reduce the side lobe level (SLL), using an evolutionary optimization technique. Particle swarm optimization and the firefly algorithm are used to reduce the SLL, as well as to steer the main beam in a specific direction. In this steerable circular array design, the amplitude...
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The pentagonal shaped UWB monopole antenna is presented in here. The proposed antenna structure consists of Pentagonal shape patch and meander fractal technique with two iterations at all the sides of the patch. The bandwidth is enhanced using meander fractal technique to all sides of a pentagonal patch which results in improved effective path leng...
The number of antennas mounted on vehicles keeps growing. Antennas in hidden modules will replace or supplement antennas in shark-fin modules. Chassis antenna cavities were recently proposed as large antenna modules, which can be built, and concealed, inside the vehicle chassis. Recent results of multiple antennas inside a chassis antenna cavity ar...
Citations
... The de-facto array configuration in numerous applications of array processing is the uniform linear array (ULA). In ad-dition to ULAs, many GNSS receivers implement Controlled Radiation Pattern Antenna (CRPA) arrays [14]. ULA and CRPA arrays have, respectively, uniform distance and uniform angular spacing between neighboring antennas. ...
This paper establishes the role of sparse arrays and sparse sampling in antijam global navigation satellite systems (GNSS). We show that both jammer direction of arrival estimation methods and mitigation techniques benefit from the design flexibility of sparse arrays and their extended virtual apertures or coarrays. Taking advantage of information redundancy, significant reduction in hardware and computational cost materializes when selecting a subset of array antennas without sacrificing jammer nulling or localization capabilities. In addition to the spatial array sparsity, antijam can utilize sparsity of jammers in the spatio–temporal frequency domains. By virtue of their finite number, jammers in the field of view are sparse in the azimuth and elevation directions. For the class of frequency modulated jammers, sparsity is also exhibited in the joint time-frequency signal representation. These spatial and signal characteristics have called for the development of sparsity-aware antijam techniques for the accurate estimation of jammer space-time-frequency signature, enabling its effective sensing and excision. Both theory and simulation examples demonstrate the utility of coarrays, sparse reconstructions, and antenna selection techniques for antijam GNSS.
... Interference from radar systems and other devices affects civilian use and intentionally used jammers affect military use. Many different anti-jamming techniques have been investigated [1] [2] [3] [4] [5] [6]. However, null steering has been a commonly applied technique used for effective interference rejection[7] [8] [9] [10] [11] [12]. ...
In this paper, the implementation of a null-steering antenna array using GPS patch antennas is suggested. The antenna array consists of five patch antenna elements fabricated on the ceramic substrate. The antenna element proposed here is a typical circular polarization patch and a prototype patch array antenna is manufactured on the PCB. The antenna has one reference element located at the center and other four elements are placed at the corners. A null in the direction of the jamming signal can be produced by changing the phases of 4-elements. Simulation results of the array antenna by CST MWS are presented and discussed. The basic performances are measured and the results are shown. The results show that the antenna presented here can be used to remove the signals from the directions of any jammers.
... The purposes of the Mini-Array technology are to reduce the footprint of the antenna array and at the same time to preserve the halfwavelength phase difference (e.g. at L1 frequency) between the antenna elements. [1] [2] [3] [4] [5] In NAVSYS's current implementation of the GPS dual-frequency (L1/L2) S- CRPA, a solid high dielectric hemispherical lens is used above the seven antenna elements to bend the incoming wave to provide the half-wavelength phase difference between the antenna elements. Each microstrip dualfrequency antenna element consists of stacked patches. ...
NAVSYS Corporation has developed a 7-element GPS L1/L2 Small Controlled Reception Pattern Antenna (SCRPA) packaged in a 7-inch form factor. In order to further reduce the footprint of the antenna array such the GPS technology can be more widely adopted, NAVSYS Corporation teamed up with SPAWAR Systems Center, Naval Research Laboratory, and EDO Corporation under ONR sponsorship to design and develop a 7-element dual-frequency L1/L2 S-CRPA in a 5.3-inch form factor. This paper will report the design and simulation of the 5.3-inch 7-element L1/L2 S-CRPA and present measurements of the antenna array prototype. Simulation and test results will be summarized including the input impedance of antenna elements, the mutual coupling between antenna elements, the radiation pattern of the antenna elements, and the antenna array performance when integrated with antenna electronics and used for GPS navigation.
The use of the miniature controlled reception pattern antennas (CRPAs) in GNSS equipment is one of the trends in GPS, Baidow, GLONASS development. A miniaturized GPS antenna array technology reduces the size of the antenna elements and the array dimensions. Miniature CRPAs are in demand not only with mass consumer of GPS/GLONASS house-hold equipment, but with expert users of complex hardware as well, where high-tech multi-sensor miniature antenna systems (AC) can be applied. Such types of AC used for intelligent control of spatial selectivity are considered as antenna arrays. The advantages of miniature CRPAs with anti-jamming capability include possibility to be installed on vehicles where it used to be impossible due to their size. The negative effect of miniaturization is in degradation of some antennas characteristics, such as gain, suppression of the reverse lobe of radiation pattern (RP), a heterogeneity of RP. In miniature antennas, the resonator interinfluence increases, that leads to distortion of individual emitters RP and to the in-crease of the total RP lobe of the antenna array irregularity, as well as the width of RP lobe. Designers take special measures to reduce the interinfluence of the resonators. However, they are not fully described in the available literature. Therefore, the achieved performance of miniature CRPAs is in great interest. The final criterion (from a consumer point of view) is in effective functional of a device containing a miniature CRPA, the degradation of its parameters in compare with traditional CRPA equipment of expert users. The authors focus on property investigation of miniature CRPAs manufactured primarily by US industry. Specifications of two antennas and some expected details of the miniaturized antenna array technology are described along with the test results of their ability to perform the objective function jammer suppression. The article contains the results obtained from independent testing of electrodynamics parameters of miniature L1/L2 frequency CRPA and its design analysis. The experimental data of sensor interinfluence are outlined. The measures to reduce the sensor interinfluence are take into account. The efficiency of the miniature antenna is estimated in the process of interference suppression by means of computer simulation. The Monte-Carlo method is applied. For the sake of generality, two types of algorithm for interference suppression are used.
Direction of Arrival (DOA) estimation algorithms specifically Multiple SIgnal Classification (MUSIC) and Minimum Variance Distortionless Response (MVDR) are used in a planar array - shaped dielectric lens combination to locate a desired user. However, refractive effect of the lens has to be compensated for in these algorithms, rapidly in real time to extract the true arrival angles. Geometrical optics is employed to trace the rays from an aperture in front of the lens, through the shaped lens boundaries to the individual antenna elements to determine the DOA of the user signal. Angle dependent modifications for the DOA of the signal in both elevation and azimuth planes have been introduced to correct for the refractive effects of the lens and extract the correct angle of arrival using a new mapped column peak search technique.
In this study, a novel compact controlled reception pattern antenna for global navigation satellite system (GNSS) applications is presented. Details of the design and the fabrication are given together with measurement results. The miniaturisation has been achieved by employing a five-element polarimetric array approach, resulting in anti-jamming capabilities for many applications where the antenna size is a major constraint. The antenna has a relatively wide bandwidth around the GNSS L1 band which contains many different GNSS signals. The anti-jamming performance of the antenna with respect to differently polarised jammers as well as its positioning capability are investigated.
This paper presents an anti-jam GPS array. The antenna is comprised of 4 small size radiating cavities filled with two stacked patches and a series of dielectric substrates and a foam layer. The main features of the antenna are low profile shape and low inter-element coupling. The antenna design is compatible with high impedance surface (HIS) insertion, which can potentially improve the anti-jam capabilities of the array by providing further inter-element coupling reduction.
In the Global Position System (GPS), receivers spend a long time to acquire the signals required for position. A study to determine the factors affecting time to first fix (TTFF) and methods to improve it is being conducted. This paper addresses two key aspects, which are the acquisition process and antenna design. Studies on advance correlation techniques such as FFT, XMC and Sqaured-D are being done over the conventional sliding serial/parallel correlator. At the same time, we also investigate the advantages of CRPA antenna over FRPA antenna as well as other new antenna designs. Simulation and actual data logging of the satellite view at a specific location is being done to study the possibility and feasibility of implementing a look up table for improving cold start. An actual field-test on three different types of receivers coupled with three different antennas with different LNA gain is being done at two different location to simulate clear sky and actual operating conditions, to address the validity of TTFF specifications provided by the manufacturer.
Smart antenna involves array processing to manipulate the signals induced on various antenna elements to accomplish beam steering and improve interference rejection. To improve directivity a shaped dielectric lens is used to further collimate the rays in a specified direction and help reduce interference. Direction Of Arrival (DOA) estimation algorithms specifically Multiple SIgnal Classification (MUSIC) and Minimum Variance Distortionless Response (MVDR) are employed for a planar array - shaped dielectric lens combination to locate a desired user. Refractive effect of the lens has to be compensated for in these algorithms rapidly in real time to extract the true arrival angles. Geometrical optics is employed to trace the rays from an aperture in front of the lens through the shaped lens boundaries to the individual antenna elements to determine the DOA of the user signal. Angle dependent modifications for the DOA of the signal in both elevation and azimuth planes have been introduced to correct for the refractive effects of the lens and extract the correct angle of arrival using a new mapped column peak search technique.
