Estimation of Detection Performance for Vehicle FMCW Radars Using EM Simulations

This paper proposes a systematic method for estimating detection performances of a frequency-modulated continuous wave radar using electromagnetic simulations. The proposed systematic method includes a radar system simulator that can obtain range-Doppler images using the electromagnetic (EM) simulations in conjunction with a test setup employed for performance evaluation of multiple targets at different velocities in a traffic environment. This method is then applied for optimizing the half-power beamwidths of the antenna array using an evaluation metric defined to improve the detection strengths for the multiple targets. The optimized antenna has vertical and horizontal half-power beam widths of 10??? and 60???, respectively. The results confirm that that the proposed systematic method is suitable to improve the radar detection performance with the enhanced radar-Doppler images

A Suboptimal Approach to Antenna Design Problem With Kernel Regression

This paper proposes a novel iterative algorithm based on a Kernel regression as a suboptimal approach to reliable and efficient antenna optimization. In our approach, the complex and non-linear cost surface calculated from antenna characteristics is fitted into a simple linear model using Kernels, and an argument that minimizes this Kernel regression model is used as a new input to calculate its cost using numerical simulations. This process is repeated by updating coefficients of the Kernel regression model with new entries until meeting the stopping criteria. At every iteration, existing inputs are partitioned into a limited number of clusters to reduce the computational time and resources and to prevent unexpected over-weighted situations. The proposed approach is validated for the Rastrigins function as well as a real engineering problem using an antipodal Vivaldi antenna in comparison with a genetic algorithm. Furthermore, we explore the most appropriate Kernel that minimizes the least-square error when fitting the antenna cost surface. The results demonstrate that the proposed process is suitable to be used in antenna design problems as a reliable approach with a fast convergence time

Design of a Wideband Printed Patch Dipole Antenna with a Balanced On-Board Feeding Network

This paper proposes a wideband printed patch dipole antenna with a simple on-board feeding network. The proposed antenna is composed of two dipole radiators, a transmission line, and an on-board feeding network with a chip balun. The dipole radiators are printed on a substrate, and the edges of the radiators are truncated to create a hexagonal shape with wide impedance-matching characteristics. The chip balun is embedded in an RO4003C printed circuit board (PCB) to excite differential feeding to each radiator with a 180° phase difference. The proposed antenna is optimized using a CST Studio full electromagnetic software tool, and it is fabricated and measured in an anechoic chamber. The measured fractional bandwidth for the reflection coefficient below −10 dB is 79.5%, and the proposed antenna has a measured gain of 7.1 dBi at 3.5 GHz

Application of genetic algorithms to the design of microstrip antennas, wire antennas and microwave absorbers

textThis dissertation explores the general methodology for designing electromagnetic (EM) systems by combining genetic algorithms (GA) with computational electromagnetic (EM) simulations. The EM problems investigated are broadband and multi-band microstrip antennas, low-profile microwave absorbers and electrically small wire antennas. It is shown that optimized performance can be designed and realized using simple shape control. In addition, novel GA approaches are investigated for more challenging multi objective problems. The developed methodology is also used to explore performance bounds in complex EM systems. First, the use of GA to design microstrip antenna shapes for broadband and multi-band applications is investigated. A full-wave electromagnetic solver is employed to predict the performance of microstrip antennas with arbitrary patch shapes. A GA with two-point crossover and geometrical filtering is implemented to optimize the patch shape. For broadband application, the optimized patch antenna achieves a four-fold improvement in bandwidth when compared to a standard square microstrip. For multi-band application, the optimized patches show that arbitrary frequency spacing ranging from 1:1.1 to 1:2 can be achieved. Tri-band and quad-band microstrip shapes are also generated and the resulting designs show good operations at the designated frequencies. Second, the use of GA for designing optimal shapes for corrugated coatings under near-grazing incidence is examined. Optimized coating shapes depending on different polarizations are generated. Physical interpretations for the optimized structure are discussed, and the resulting shape is compared to conventional planar and triangular shaped designs. This problem is also extended from the single to multi-objective optimization using the Pareto GA. Optimization results using two different objectives, the height (or weight) of the coating versus absorbing performance, are presented. Finally, this dissertation reports on the use of GA in the design optimization of electrically small wire antennas, taking into account of bandwidth, efficiency and antenna size. To efficiently map out this multi-objective problem, the Pareto GA is implemented with the concept of divided range optimization. An optimal set of designs, trading off bandwidth, efficiency and antenna size, are generated. Several GA designs are built, measured and compared to the simulation. Physical interpretations of the GA-optimized structures are provided, and the results are compared against the well-known fundamental limit for small antennas. Further improvements using other geometrical design freedoms are also discussed.Electrical and Computer Engineerin

Antenna Design for Microwave and Millimeter Wave Applications II: Latest Advances and Prospects

In recent decades, novel and significant approaches to the design of antennas for various microwave and millimeter-wave applications have been attempted [...

New perspective on single-radiator multiple-port antennas for adaptive beamforming applications

One of the most challenging problems in recent antenna engineering fields is to achieve highly reliable beamforming capabilities in an extremely restricted space of small handheld devices. In this paper, we introduce a new perspective on single-radiator multiple-port (SRMP) antenna to alter the traditional approach of multiple-antenna arrays for improving beamforming performances with reduced aperture sizes. The major contribution of this paper is to demonstrate the beamforming capability of the SRMP antenna for use as an extremely miniaturized front-end component in more sophisticated beamforming applications. To examine the beamforming capability, the radiation properties and the array factor of the SRMP antenna are theoretically formulated for electromagnetic characterization and are used as complex weights to form adaptive array patterns. Then, its fundamental performance limits are rigorously explored through enumerative studies by varying the dielectric constant of the substrate, and field tests are conducted using a beamforming hardware to confirm the feasibility. The results demonstrate that the new perspective of the SRMP antenna allows for improved beamforming performances with the ability of maintaining consistently smaller aperture sizes compared to the traditional multiple-antenna arrays

A Novel Approach to Array Manifold Calibration Using Single-Direction Information for Accurate Direction-of-Arrival Estimation

A method of array manifold calibration using one steering vector measured in a single direction is proposed. The phase information of the measured steering vector is used to derive a novel calibration matrix that is proposed to compensate for the relative phase distortion (RPD) at each antenna port. We also present a metric function defined as a standard deviation of the RPD to determine the optimum calibration angle, which provides intuition for the cause of the accuracy degradation in the direction-of-arrival estimation. To verify the feasibility, a seven-element circular array with identical microstrip patch antennas is fabricated for calibrating its array manifold using a single steering vector measured in a full anechoic chamber. The calibrated array manifold is then used to estimate the direction of arrival, and its accuracy is compared to the calibrated result obtained from the traditional least-squares method. The results demonstrate that the estimation error can be improved by 54.9 degrees compared to the traditional least-squares method, when the number of measured steering vectors is extremely limited

Prediction of Target Detection Probability Based on Air-to-Air Long-Range Scenarios in Anomalous Atmospheric Environments

We investigate a target detection probability (TDP) using path loss of an airborne radar based on air-to-air scenarios in anomalous atmospheric and weather environments. In the process of calculating the TDP, it is necessary to obtain the overall path loss including the anomalous atmospheric environment, gas attenuation, rainfall attenuation, and beam scanning loss. The path loss including the quad-linear refractivity model and other radar input parameters is simulated using the Advanced Refractive Effects Prediction System (AREPS) software along the range and the altitude. For the gas and rainfall attenuations, ITU-R models are used to consider the weather environment. In addition, the radar beam scan loss and a radar cross section (RCS) of the target are considered to estimate the TDP of the airborne long-range radar. The TDP performance is examined by employing the threshold evaluations of the total path loss derived from the detectability factor and the free-space radar range equation. Finally, the TDPs are obtained by assuming various air-to-air scenarios for the airborne radar in anomalous atmospheric and weather environments

Design of a Small Controlled Reception Pattern Antenna Array With a Single-Layer Coupled Feed Structure for Enhanced Bore-Sight Gain and a Matching Bandwidth

This article proposes the design of a controlled reception pattern antenna (CRPA) array with a single-layer coupled feed structure to improve the radiation gain and a matching bandwidth. Each array element consists of a feeding patch and an outer radiating loop printed on a thick ceramic substrate with a high dielectric constant. The loop is capacitively coupled to the patch and the coupling strength is adjusted by varying the gap distance. Antenna characteristics are measured in a full anechoic chamber, and an equivalent circuit is built to verify the operating principle. The results demonstrate that the proposed structure is more suitable to enhance the gain and bandwidth compared to a conventional patch antenna in small CRPA arrays