Ieee transactions on antennas and propagation

An efficient, low-loss, low sidelobe, high dynamic range phased-array radar antenna system is disclosed that uses metamaterials, which are manmade composite materials having a negative index of refraction, to create a biconcave lens architecture (instead of the aforementioned biconvex lens) for focusing the microwaves transmitted by the antenna. Accordingly, the sidelobes of the antenna are reduced. Attenuation across microstrip transmission lines may be reduced by using low loss transmission lines that are suspended above a ground plane a predetermined distance in a way such they are not in contact with a solid substrate. By suspending the microstrip transmission lines in this manner, dielectric signal loss is reduced significantly, thus resulting in a less-attenuated signal at its destination.

Phased array metamaterial antenna system

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Advanced Digital Signal Processing And Noise Reduction

Estimation theory with applications to communications and control

Detection of road boundaries and obstacles is essential for autonomous vehicle navigation. In this paper, we propose a road boundary and obstacle detection method using a downward-looking light detection and ranging sensor. This method extracts line segments from the raw data of the sensor in polar coordinates. After that, the line segments are classified into road and obstacle segments. To enhance the classification performance, the estimated roll and pitch angles of the sensor relative to the scanning road surface in the previous time step are then used. The classified road line segments are applied to track the road boundaries, roll, and pitch angles by using an integrated probabilistic data association filter. The proposed method was evaluated with the autonomous vehicle A1, which was the winner of the 2010 Autonomous Vehicle Competition in Korea organized by the Hyundai-Kia automotive group. The proposed method using the estimated roll and pitch angles can detect road boundaries and roadside, as well as road obstacles under various road conditions, including paved and unpaved roads and intersections.

Enhanced Road Boundary and Obstacle Detection Using a Downward-Looking LIDAR Sensor

Wave attenuation through rain with different rainfall rates at millimeter wave ( $f = 77$ GHz) and low-terahertz (Low-THz) ( $f = 300$ GHz) frequencies is studied in this article. Rain has pronounced impacts on electromagnetic wave propagation and one of the well-known effects is attenuation of the transmitted wave. Attenuation at both frequencies and hydrometeor properties [rainfall rate and drop size distribution (DSD)] are measured simultaneously. The measured DSD is fit with gamma and Weibull distributions and is also compared to the frequently used distribution Marshall and Palmer (MP) model; Weibull is shown to be a better fit to the measured DSDs. Theoretical prediction of attenuation as a function of rainfall rate (up to about 20 mm/h) is determined using Mie scattering theory, and the fit gamma and Weibull, and MP distribution models; as well as using the International Telecommunications Union Radiocommunication Sector (ITU-R) recommendation. The calculations are evaluated by comparing them to the experiment. The measured results at 77 GHz best agree with the ITU-R recommendation whereas at 300 GHz, the calculation based on Mie scattering and the Weibull distribution exhibits the best fit to the measured data. The measured data that exceed the theoretical prediction are analyzed and interpreted based on their corresponding observed drop size properties, for the first time.

Rain Attenuation at Millimeter Wave and Low-THz Frequencies

In this letter, we report initial experimental results which provide the foundation for low-terahertz (low-THz) radar imagery for outdoor unstructured scenarios as expected in automotive sensing. The requirements and specifications for a low-THz single imaging radar sensor are briefly outlined. The imaging capabilities of frequency-modulated continuous-wave (FMCW) radar operating at 150 GHz are discussed. A comparison of experimental images of on-road and off- road scenarios made by a 150-GHz FMCW radar and a reference 30-GHz stepped-frequency radar is implemented, and their performance is analyzed.

Experimental Low-Terahertz Radar Image Analysis for Automotive Terrain Sensing

In this study, the forward scatter Doppler phase signature formation is analysed to show the rationale for the forward scatter radar in the true sense of the meaning, where a target actually crosses the baseline; so the advantage of the main shadow lobe is taken and, therefore a forward scatter effect occurs to enhance signal to clutter ratio. The modelling approach suggested is based on the consideration of the Doppler phase signature as a result of superposition of the direct path signal and the shadow radiation signal. It is shown that the target signature may be represented as a Doppler signature of a point-like target specified by its trajectory and speed, which is modulated according to forward scatter cross-section of an actual extended target specified by its silhouette at each moment of motion. The proposed model may be recommended to provide matched filtering in coherent processing. Finally, the approach is verified experimentally using calibrated targets with conductive and absorbing coating in the controlled environment and maritime targets in the real sea conditions.

/pdf/phenomenology-of-doppler-forward-scatter-radar-for-surface-4hyooq6ctj.pdf

Phenomenology of Doppler forward scatter radar for surface targets observation

A novel dielectric lens antenna with a broadband integrated waveguide-based feed and an optimized tapered extension is presented for low terahertz frequencies. The antenna consists of an extended hemispherical lens fed by a standard WR-3 rectangular waveguide fitted directly at the bottom of the lens. The antenna has been designed for high-resolution imaging radar systems requiring very wide bandwidth performance and highly directive beams. A novel matching technique based on an air pocket etched off the lens dielectric is employed to obtain broadband antenna operation covering the entire dominant-mode bandwidth of the waveguide. In addition, a new taper shaped lens extension is proposed for the first time and optimized to achieve improved sidelobe level and gain performance. The antenna is compatible with newly developed waveguide-based automotive radar and communications systems. The operating 3 dB gain bandwidth is 30% (230–310 GHz) achieving a maximum of 30 dB measured gain. The measured S 11 is well below –14 dB across the WR-3 band.

/pdf/low-thz-dielectric-lens-antenna-with-integrated-waveguide-31q6s770fj.pdf

Edward Hoare

Papers

Rain Attenuation at Millimeter Wave and Low-THz Frequencies

Experimental Low-Terahertz Radar Image Analysis for Automotive Terrain Sensing

Phenomenology of Doppler forward scatter radar for surface targets observation

Low-THz Dielectric Lens Antenna With Integrated Waveguide Feed

Low-THz Radar, Lidar and Optical Imaging through Artificially Generated Fog