309 research outputs found

    Horn feed having overlapping apertures Patent

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    Characteristics of antenna horn feeds consisting of central horn with overlapping peripheral horn

    Angle estimation using adaptive monopulse MUSIC

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    Investigation of L-band shipboard antennas for maritime satellite applications

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    A basic conceptual investigation of low cost L-band antenna subsystems for shipboard use was conducted by identifying the various pertinent design trade-offs and related performance characteristics peculiar to the civilian maritime application, and by comparing alternate approaches for their simplicity and general suitability. The study was not directed at a single specific proposal, but was intended to be parametric in nature. Antenna system concepts were to be investigated for a range of gain of 3 to 18 dB, with a value of about 10 dB considered as a baseline reference. As the primary source of potential complexity in shipboard antennas, which have beamwidths less than hemispherical as the beam pointing or selecting mechanism, major emphasis was directed at this aspect. Three categories of antenna system concepts were identified: (1) mechanically pointed, single-beam antennas; (2) fixed antennas with switched-beams; and (3) electronically-steered phased arrays. It is recommended that an L-band short backfire antenna subsystem, including a two-axis motor driven gimbal mount, and necessary single channel monopulse tracking receiver portions be developed for demonstration of performance and subsystem simplicity

    Study of lunar landing sensor performance final report

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    Lunar landing sensor performance - extended range altimeter, short range velocity sensor, and beacon tracking rada

    Hybrid analog-digital processing system for amplitude-monopulse RSSI-based MiMo wifi direction-of-arrival estimation

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    We present a cost-effective hybrid analog digital system to estimate the Direction of Arrival (DoA) of WiFi signals. The processing in the analog domain is based on simple wellknown RADAR amplitude monopulse antenna techniques. Then, using the RSSI (Received Signal Strength Indicator) delivered by commercial MiMo WiFi cards, the DoA is estimated using the socalled digital monopulse function. Due to the hybrid analog digital architecture, the digital processing is extremely simple, so that DoA estimation is performed without using IQ data from specific hardware. The simplicity and robustness of the proposed hybrid analog digital MiMo architecture is demonstrated for the ISM 2.45GHz WiFi band. Also, the limitations with respect to multipath effects are studied in detail. As a proof of concept, an array of two MiMo WiFi DoA monopulse readers are distributed to localize the two-dimensional position of WiFi devices. This costeffective hybrid solution can be applied to all WiFi standards and other IoT narrowband radio protocols, such us Bluetooth Low Energy or Zigbee.This work was supported in part by the Spanish National Projects TEC2016-75934-C4-4-R, TEC2016-76465-C2-1-R and in part by Regional Seneca Project 19494/PI/14

    Antenna Design and Signal Processing for Mechanical FMCW Coastal Surveillance Radar Systems

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    The demand for highly sophisticated radar systems to be implemented along the coastal waters of the Strait of Malacca for the surveillance and tracking of vessels that travels through this narrow Strait has risen rapidly over the last few decades. Along with the technological advancements in radar systems, the increased demand is in response to the success that radars have introduced in significantly reducing some of the biggest problems contributed from security and weather condition perspectives. The existing radars implemented by Indonesian authorities to fulfil the surveillance requirements of the Strait mainly comprises of electronic scanning systems. Nonetheless, several allocated radar sites along the Strait inevitably lacks the basic infrastructure and accessibility required to install more complex systems (i.e. electronic scanning radars) that are prone to higher maintenance. This have favoured authorities to opt for the use of mechanical scanning radars, which, unlike phased array systems, are simpler, less complex, and significantly more affordable systems. The resolution performance alongside the accuracy of the positional information of a detected target provided by the radar is highly dependent on the angular resolution of the antenna. For mechanically scanning radars, a highly directional beam is commonly produced by employing conventional parabolic reflector antennas. Reflector antennas are a popular choice for surveillance and tracking applications as it is known for producing beams with very high gain and narrow beamwidths in both planes. However, this is usually achieved by employing an undesirably large reflector, which tends to significantly increase the cost of the radar system, and most importantly its size and weight, which is critical especially for applications that highly values compact and mobile systems. To overcome this issue faced in many similar situations, several angle measurement techniques have been introduced to improve the detection performance of radars without increasing the physical size of the antenna, with the most notable and highly successful one being monopulse technique. This research project proposes a model of a reflector antenna design for a mechanical scanning radar that is suitable to provide coastal surveillance and monitoring of vessels and low flying objects. The objective of the antenna design is to significantly improve the resolution and accuracy for target detection without utilizing a larger dish, but instead through the implementation of amplitude monopulse and a novel post-detection processing technique that allows for the design of a more compact and cost-effective antenna system. The proposed reflector antenna system that achieves these objectives comprises of a dual-horn feed and a vertically truncated reflector of an optimal aperture shape and dimension to create a pair of simultaneous overlapping fan-shaped beams that is narrow in azimuth and several times wider in elevation. The design of the monopulse feed is modelled and simulated on a CEM tool (CST) to evaluate the monopulse patterns produced in the horizontal plane of the radar, which are optimized towards the requirements of the application. In addition, this thesis introduces a novel post-detection signal processing technique that uses priori information of the antenna response pattern to offer a substantial enhancement on the resolution and clutter resilience of any new or existing radar antenna system at a very low cost, which is especially likely to make a significant contribution to the safety at sea. In addition to limiting the size of the antenna as much as possible while fulfilling the requirements of the application in hand, employing the proposed antenna system along the coastal shores of the Strait of Malacca would largely prioritize on keeping the effective weight and cost of the antenna to a minimum. This is achieved by manufacturing the reflector through 3D printing technology and coating its surface with a copper compound spray to achieve the properties of a metal. A prototype of the reflector antenna is manufactured accordingly using the proposed method of fabrication in order to provide an assessment of the practical antenna performance. The radiation properties of the antenna pattern are measured in an outdoor range test facility, and the measurement results allows for an accurate validation of the electromagnetic (EM) simulations of the corresponding antenna design obtained on CST. Finally, in order to assess the enhancing effect of the proposed signal processing technique on the resolution performance of an existing antenna, MATLAB based codes have been developed to demonstrate the technique on several simulated far-field patterns of antennas with common line source distributions before it is applied on the sum pattern output of the monopulse antenna designed in this project

    Radial Line Slot Antenna Design with Groove Gap Waveguide Feed for Monopulse Radar Systems

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    Radial line slot arrays (RLSAs) are well suited to be used in monopulse radar systems. The excitation of the sum and difference patterns can be achieved by the design of simple feeds as shown in this paper. In this work, a feed system based on the use of a cavity made in groove gap waveguide technology (GGW) is presented. The design is made at 24 GHz but can be easily scaled to higher frequencies as the technology is contact-less and fully made in metal. A good isolation between the sum and difference ports together with a good matching of the two of them is obtained. The radiation patterns of the manufactured antenna are also in good agreement with the simulated ones.This work was supported in part by the Spanish Government, Ministry of Economy, National Program of Research, Development and Innovation under the projects TEC2016-79700-C2-2-R and TEC2017-85529-C3-1-R and by the Madrid Regional Government under the project SPADERADAR “Space Debris Radar” (S2013/ICE-3000) and the FPI grant with reference BES-2015-07523

    A comprehensive investigation of retrodirective cross-eye jamming

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    Cross-eye jamming is an Electronic Attack (EA) technique that induces an angular error in the radar being jammed. The main benefit of cross-eye jamming is that it is effective against monopulse tracking radars, which are largely immune to other forms of jamming. The objective of this research is to gain a complete understanding of cross-eye jamming so that systems that might be developed in future can be properly specied. The main contribution of this work is a comprehensive mathematical and experimental study of retrodirective cross-eye jamming. The mathematical analysis considers all aspects of an isolated, single-loop, retrodirective cross-eye jamming engagement, thereby avoiding the approximations inherent in other cross-eye jamming analyses. Laboratory experiments that accurately represent reality by using the radar for both transmission and reception, and simulating a true retrodirective cross-eye jammer were performed to validate the theoretical analysis. Lastly, the relationship between the angular error induced in the radar being jammed and the matching required from a cross-eye jammer system is explored. The most important conclusion of this work is that the traditional analyses of cross- eye jamming are inaccurate for the conditions under which cross-eye jammers operate. These inaccuracies mean that the traditional analyses are overly conservative, particularly at short ranges and for high cross-eye gains, suggesting that practical cross-eye jammers can be realised more easily than is generally believed.Thesis (PhD)--University of Pretoria, 2010.Electrical, Electronic and Computer Engineeringunrestricte

    3D conformal antennas for radar applications

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    Embedded below the radome of a missile, existing RF-seekers use a mechanical rotating antenna to steer the radiating beam in the direction of a target. Latest research is looking at replacing the mechanical antenna components of the RF seeker with a novel 3D conformal antenna array that can steer the beam electronically. 3D antennas may oer signicant advantages, such as faster beamsteering and better coverage but, at the same time, introduce new challenges resulting from a much more complex radiation pattern than that of 2D antennas. Thanks to the mechanical system removal, the new RF-seeker has a wider available space for the design of a new 3D conformal antenna. To take best benets of this space, dierent array shapes are studied, hence the impact of the position, orientation and conformation of the elements is assessed on the antenna performance in terms of directivity, ellipticity and polarisation. To facilitate this study of 3D conformal arrays, a Matlab program has been developed to compute the polarisation pattern of a given array in all directions. One of the task of the RF-seeker consists in estimating the position of a given target to correct the missile trajectory accordingly. Thus, the impact of the array shape on the error between the measured direction of arrival of the target echo and its true value is addressed. The Cramer-Rao lower bound is used to evaluate the theoretical minimum error. The model assumes that each element receives independently and allows therefore to analyse the potential of active 3D conformal arrays. Finally, the phase monopulse estimator is studied for 3D conformal arrays whose quadrants do not have the same characteristics. A new estimator more adapted to non-identical quadrants is also proposed

    Wideband two-dimensional and multiple beam phased arrays and microwave applications using piezoelectric transducers

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    Modern satellite, wireless communication, and radar systems often demand wideband performance for multi-channel operation and the ability to steer multiple beams for multiple moving targets. This dissertation covers a variety of topics to design low-cost and wideband antenna systems. The main areas of study are microwave devices controlled piezoelectric transducers (PETs) and wideband baluns and balanced microwave circuits using parallel-strip lines. Some focus has also been given to the design of Rotman lens for multiple beam generation and Vivaldi antenna arrays for wideband two-dimensional scanning. The dielectric perturbation technique controlled by PET is introduced to design a wideband phase shifter and a QPSK modulator, and to tune the resonant frequency of a slot dipole. The designed PET-controlled phase shifters are used for beam steering in a dual beam phased array using a bidirectional feeding scheme and a five-beam phased array using a microstrip Rotman lens. Vivaldi-type antennas are commonly used to achieve wideband performance. Very wideband performance can be achieved using an antipodal tapered slot antenna because of its inherent simple wideband transition from microstrip line to parallel-strip line. An antipodal tapered slot antenna and a phased array are designed to span 10 to 35 GHz. In addition, a 4??4 two-dimensional antenna array is designed using wideband antipodal tapered slot antennas, and two sets of PET-controlled phase shifters for E- and H-plane scanning are fabricated to steer the beam. As a microwave system using wideband antenna array, a new low-cost and wideband phased array radar is developed using a modulated pulse over 8 to 20 GHz band. The double-sided parallel-strip line as a balanced line is presented. The parallelstrip line offers much flexibility for microwave circuit designs. This transmission line makes it possible to realize a low impedance line and allows the design of a compact wideband balun and junction. Wideband transitions (or baluns) from parallel-strip line to microstrip line, a typical unbalanced transmission line, are realized to cover several octave bandwidth. Balanced microwave filters and a hybrid coupler are developed using the parallel-strip line
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