Retroreflector and Multibeam Antenna for a Millimeter Wave Collision Avoidance System

RÉSUMÉ La section efficace du radar (SER) pour des cibles automobiles a une réponse angulaire étroite. Une variation de plusieurs décibels par mètre carré (dBsm) peut également être observée avec un léger changement de l’orientation de la cible. La localisation de telles cibles est difficile pour un radar automobile. En outre, un matériel complexe est généralement nécessaire pour mettre en oeuvre un radar efficace, ce qui se traduit par des systèmes coûteux qui ne sont abordables que dans les véhicules haut de gamme. Cela défie l’objet d’un système de sécurité pour éviter les accidents de la route à grande échelle. Cette thèse présente une nouvelle balise d’amélioration de SER et une antenne multifaisceaux pour des applications de radar automobile. Ces composants peuvent éventuellement améliorer les performances d’un algorithme de super-résolution, et permettre le développement d’un radar d’évitement de collision automobile simple et peu coûteux. Une architecture de système simple et rentable est particulièrement importante dans la gamme de fréquences d’ondes millimétriques, allouée pour cette application, où les atténuations du signal et les coûts de dispositif sont significativement élevés. Les structures proposées dans cette thèse peuvent également trouver des applications dans d’autres applications en ondes millimétriques. Un système radar est analysé en étudiant les propriétés de l’algorithme de super-résolution bien connu ESPRIT. Sur la base d’une simulation numérique MATLAB de cet algorithme, il est établi qu’une SER stable est importante pour l’utilisation de cet algorithme dans des applications automobiles. Ceci peut être réalisé en équipant la cible d’un marqueur d’amélioration de la SER. Deuxièmement, dans cet algorithme, la taille du réseau de récepteurs détermine le nombre de cibles détectables. En sectorisant le CdV du radar en utilisant une antenne multifaisceaux, l’erreur de localisation angulaire peut être réduite pour un plus grand nombre de cibles. La balise proposée est conçue à 77 GHz, fonctionnant dans la bande attribuée au radar automobile (76 GHz à 81 GHz). Les caractéristiques des radars automobiles dans la littérature suggèrent un CdV en forme de faisceau en éventail pour la balise avec un CdV plus large dans le plan azimutal. De CdV de 120o et 9o dans les plans d’azimut et d’élévation sont respectivement choisis comme critères de conception pour la balise proposée. La propriété de rétroréflexion dans le plan d’azimut aide à améliorer la SER de la balise. La balise proposée reflète le signal incident avec une rotation de polarisation linéaire de 90o. Cette modulation de polarisation permet d’améliorer la visibilité de la cible par rapport au bruit de fond. De plus, une modulation d’amplitude est également implémentée dans la balise.----------Rear radar cross section (RCS) of automotive targets has a narrow angular response. A variation of several decibel per square meter (dBsm) can also be observed with slight change in the target orientation. Localization of such targets is challenging for an automotive radar. Furthermore, complex hardware is typically required to implement an effective radar resulting in high-cost systems that are affordable only in high-end vehicles. This defies the object of a safety system to avoid roadside accidents at large scale. This dissertation présents novel RCS enhancing tag and multibeam antenna for automotive radar applications. These components can possibly improve the performance of a super-resolution algorithm, and enable the development of a simple, low-cost automotive collision avoidance radar. Simple and costeffective system architecture is particularly important in millimeter wave frequency range, allocated for this application, where the material losses and device costs are significantly high. The proposed structures in this thesis can also find applications in other millimeter wave applications. A radar system is analyzed by studying the properties of Estimation of Signal Parameters via Rotational Invariance Technique (ESPRIT), a well know super-resolution algorithm. Based on a MATLAB numerical simulation of this algorithm, it is established that a stable target RCS is important for employing this algorithm in automotive applications. This can be achieved by equipping the target with a RCS enhancing tag. Secondly, in this algorithm, the size of the receiver array determines the number of detectable targets. By sectoring the radar field of view (FoV) using a multibeam antenna, the localization error can be reduced for higher number of targets. The proposed tag is designed at 77 GHz, operating in the band allocated for automotive radar (76 GHz to 81 GHz). Automotive radar characteristics in the literature suggest a fan-beam shaped FoV for the tag with wider FoV in azimuth plane. Azimuth and elevation plane FoV of 120o and 9o are selected as design criteria for the proposed tag. Retroreflection property in the azimuth plane helps to improve the tag RCS. The proposed tag reflects the incident signal with 90o linear polarization rotation. This polarization modulation can enhance the target visibility against the background clutter. Additionally, an amplitude modulation is also implemented in the tag. This modulation can help to communicate additional information. It can also facilitate the target detection by improving the signal to noise ratio of the processed received signal

Recommendations and comments concerning documentation on the microwave active spectrometer systems

There are no author-identified significant results in this report

Calibration and Signal Processing of Airborne Stand Profile Radar used in forest inventory

TomoRadar is a helicopter/UAV (Unmanned Aerial Vehicle) based FM-CW microwave ranging radar designed for the forest inventory. Developed by FGI (Finnish Geospatial Research Institute), TomoRadar can scan forest with Ku-band signals and then receive the backscatter signal from targets. The target distance can be figured out from the backscattered signal. Furthermore, various information around forest can be evaluated. As a ranging scatterometer the system calibration and signal processing are necessary and critical tasks. In This thesis, these two major problems are researched and solved. The system calibration is limited to complete on ground and restricted in a particular range despite TomoRadar works on helicopter. Thus the range calibration experiment is conducted on the ground test field with a Luneburg lens. Besides, power calibration of system backscatter signal is researched through electrical component tests. The linearity of the radar system frequency sweep is critical in FM-CW radars. Hence, it is studied in this thesis. When TomoRadar works, the output of the whole system is analog signal in intimidate frequency (IF) band. A digitizer samples and records the output analog signal. With these signal, the information around forest cannot be obtained. To draw stand profile of forest and research forest information, the IF band signals need to be further processed. This is signal processing part of the thesis work. As a result of this thesis work, TomoRadar range calibration was achieved. The calibration results were verified by the helicopter based flying tests. The results present that the calibration completed on ground test field applied with the situation that TomoRadar works in air and scans targets in long distance. The linearity of system frequency sweep generated by DDS (Direct Digital Synthesizer) is verified. Finally, the test forest backscattered data was processed and the ranges were evaluated. Some targets stand profiles are generated and presented in this thesi

Doctor of Philosophy

dissertationMicrowave/millimeter-wave imaging systems have become ubiquitous and have found applications in areas like astronomy, bio-medical diagnostics, remote sensing, and security surveillance. These areas have so far relied on conventional imaging devices (empl

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance

Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

Enabling Ridge Waveguide Technology for Wideband Millimeter-Wave Decoys

Emerging high power millimeter wave applications such as RF decoy repeaters require transmission line technologies operating over a wide bandwidth with the ability to carry hundreds of watts of continuous wave (CW) power. To develop such repeaters an enabling technology for integration of components such as dual-polarized antennas, filters, couplers, bends, and twists is needed. This thesis presents the analysis, design, and measurements of novel passive components for such repeaters in V- and W- bands. At these high frequencies, traditional techniques of design and fabrication are challenging due to small size, losses, and wide bandwidth.A high-power capable wideband 45 ‒ 110 GHz double-ridge waveguide (WRD45110) transmission line with low loss, low dispersion, and high theoretical power-handling is demonstrated first. Then, utilizing the designed cross-section a suite of passive waveguide components required for a typical decoy repeater system such as straight transmission lines, E- and H- plane bends, 90&deg; twists, and termination loads are developed. A quad-ridge horn antenna with consistent broadside gain and stable E- and H- plane radiation patterns over the desired frequency band is also demonstrated. All components are carefully designed across different physics-based domains (RF, thermal, air-breakdown, etc.) and fabricated with either a direct metal laser sintering (DMLS) 3D printing or a conventional CNC machining with special care taken to allow for easy interconnecting.The design of a dual polarized high power capable system over 45 ‒ 110 GHz band is also presented. To combine two polarizations into the same radiating aperture, an Orthomode Transducer (OMT) based upon WRD45110 is developed. In order to fabricate this prototype through DMLS process, this OMT is devised with all the guidelines of 3D metal printing.Also, in system level, a preliminary system integration of a decoy repeater is discussed. To enhance the isolation between the TX and RX antennas in a decoy repeater, reactive impedance surfaces (RIS) with 1D RIS (corrugations), and 2D RIS (mushroom structure) are designed and built. In addition, a switched-beam phased array system that uses a perforated gradient index flat lens for beam scanning in &plusmn;30&deg; elevation and 0&deg; ‒ 360&deg; azimuth is demonstrated over the entire 45 ‒ 110 GHz frequency range.</p

Application of radar for automotive collision avoidance. Volume 1: Technical report

The purpose of this project was research and development of an automobile collision avoidance radar system. The major finding was that the application of radar to the automobile collision avoidance problem deserves continued research even though the specific approach investigated in this effort did not perform adequately in its angle measurement capability. Additional findings were that: (1) preliminary performance requirements of a candidate radar system are not unreasonable; (2) the number and severity of traffic accidents could be reduced by using a collision avoidance radar system which observes a fairly wide (at least + or - 10 deg) field of view ahead of the vehicle; (3) the health radiation hazards of a probable radar design are not significant even when a large number of radar-equipped vehicles are considered; (4) effects of inclement weather on radar operation can be accommodated in most cases; (5) the phase monopulse radar technique as implemented demonstrated inferior angle measurement performance which warrants the recommendation of investigating alternative radar techniques; and (6) extended target and multipath effects, which presumably distort the amplitude and phase distribution across the antenna aperture, are responsible for the observed inadequate phase monopulse radar performance

Wideband Antennas of Passive Seekers for Anti Radiation Missiles

Suppression of Enemy Air Defence (SEAD) is a fundamental element of Air Power application by means of in protecting friendly air attackers and destroying the enemy’s ability to defend against air attack. Most of the SEAD&nbsp;operation even today relies on Anti-radiation missile (ARM) which is an air-to-surface tactical missile designed to&nbsp;detect, seek, attack and destroy opponent’s radar. Passive seeker of ARM is a miniaturized ESM receiver which&nbsp;is capable of extracting the necessary angular data from the enemy radar emissions. Single head passive seeker&nbsp;covering wide frequency range from L to Ku band is the preferred choice. Wideband antennas have been designed&nbsp;and utilized for Direction Finding applications of ESM/ELINT receivers for ground, air and ship borne platforms.&nbsp;Unlike these platforms, there are several restrictions for passive seeker based compact ESM receiver for missile&nbsp;borne platform specially air to surface missile where lesser diameter is one of the preferred design parameter. This&nbsp;review paper mainly discusses the existing wideband antennas such as spiral, log-periodic, printed circuit vivaldi and all-metal vivaldi antennas and the comparison of their various parameters for passive seeker. The paper also&nbsp;suggests their suitability with respect to their placement on the missile for three configurations: concealed inside the&nbsp;radome, flush-mounted and conformal antenna based. The paper also brought about the specific test facility required&nbsp;for testing and evaluation of passive seeker to characterize it with missile radome which is the most challenging&nbsp;and time consuming task. Among the three passive seeker configuration discussed, conformal antenna based passive&nbsp;seeker using all-metal Vivaldi is the best option avoiding radome aberration correction which is being utilized in the&nbsp;present third generations of ARM. The second commonly and established passive seeker configuration is concealed&nbsp;inside the radome using spiral antennas where handling radome aberration correction is a limitation.&nbsp

Traceable Radiometric Calibration of Synthetic Aperture Radars

Synthetic aperture radar (SAR) systems allow to quantitatively measure the radar backscatter of an imaged terrain region. In order to achieve comparability between measurement results, traceable radiometric calibration is indispensable. The central claim of the work is that nowadays, however, radiometric SAR measurements are not traceably calibrated. In order to resolve this problem, five contributions are made: (a) The new measurement quantity “equivalent radar cross section” (ERCS) is defined. (b) A numerical approach for linking the known quantity “radar cross section” (RCS) with the novel ERCS is introduced. (c) The effect of the chosen apodization functions on radiometric measurements is analytically investigated. (d) The novel three-transponder method is developed which allows accurate RCS calibrations of SAR transponders. (e) The method of hierarchical Bayesian data analysis is introduced to the field of radiometric SAR calibration. The achieved traceability for radiometric SAR measurements allows more accurate radiometric measurement results especially for modern, high-resolution SAR systems. Furthermore, data exchange and cooperation is facilitated