Naruto Yonemoto

Performance of obstacle detection and collision warning system for civil helicopters

Some helicopters strike the power lines under the good weather conditions. Helicopter pilots sometimes have some difficulties to find such long and thin obstacles. We are developing an obstacle detection and collision warning system for civil helicopters in order to solve such problems. A color camera, an Infrared (IR) camera and a Millimeter Wave (MMW) radar are employed as sensors. This paper describes the results of different flight tests that show good enhancement of radar detection over 800m range for power lines. Additionally, we exhibit the processed fusion images that can assist the pilots in order to recognize the danger of the power lines.

W-Band Fresnel Zone Plate Reflector for Helicopter Collision Avoidance Radar

A high gain Fresnel zone plate reflector is presented for helicopter collision avoidance radar at 94 GHz. The antenna system consists of a compact, airtightness and low return loss primary source illuminating a printed reflector with Fresnel plate zone phase correction. In order to increase the overall efficiency, the reflector combines 8 correcting zones in its center and 4 on the border. Reflected phase of over 360deg is achieved by means of circular ring or combined circular and ring patches. The reflector is fabricated using standard photolithographic techniques. The primary source consists of a small FSS made by a double slot array antenna pasted on the aperture of a standard WR-10 waveguide. Antenna measurements were conducted using a compact base arrangement. The antenna performs 37.8 dBi at the center frequency of 94 GHz with a maximum value of the return loss value not exceeding -25 dB. The frequency bandwidth at -3 dB in gain and return loss is of 9%

Millimeter wave radar for the obstacle detection and warning system for helicopters

An obstacle detection and warning system for civil helicopters is now being developed. An infrared camera and a 94 GHz millimeter wave (MMW) radar have been used as its sensor. Experimental MMW radars have been built to examine their propagation properties and obstacle detection performance. A 94 GHz Vivaldi antenna has been fabricated for a compact radar antenna. Measured results demonstrated that the experimental FMCW radar has a satisfactory range and accuracy. It was also shown that the Vivaldi antenna worked well at A 90 to 100 GHz frequency range.

Millimeter-Wave Radar for Rescue Helicopters

A collision avoidance and warning system for civil helicopters in Japan has been developed. A real-time warning method was applied using an image fused from a coloured video, an IR sensor data and mm-wave radar measurements. This paper focuses on the FM-CW mm-wave radar sensor and the associated antennas, working at 94 GHz. Flight tests were conducted in order to detect power lines. Thanks to two different antennas, power line response was measured in vertical and horizontal polarizations. Maximum detection ranges are of 800 and 600m respectively. This variation comes from the antenna gain difference. Radar resolution is limited by the allocated bandwidth at 94 GHz which is 200 MHz. Comparisons were conducted on the ground with an integrated FM-CW radar working at 77 GHz and achieving 500 MHz bandwidth

76.5 GHz millimeter-wave radar for foreign objects debris detection on airport runways

The paper is a joint work between the LEAT (France) and the ENRI (Japan) in the framework of a Sakura project supported by the JSPS and the French Ministry of Foreign Affairs. The purpose is the study of a FOD (Foreign Object Debris) detection system on airport runways. A FM-CW mm-Wave radar working between 76.25 and 76.75 GHz is used together with a high directivity printed reflectarray. Measurement results show detection capabilities of a -20 tlBsm cylinder up to 35 m which is 10 m less than the FAA recommendations. Antenna improvements are discussed for reaching the requirements and system performance as well as the use of calibration objects.

Design and Field Feasibility Evaluation of Distributed-Type 96 GHz FMCW Millimeter-Wave Radar Based on Radio-Over-Fiber and Optical Frequency Multiplier

Foreign object debris (FOD) on airport runways must be removed immediately. To detect small debris, we proposed and developed an optically-connected distributed-type 96 GHz millimeter-wave radar system based on radio-over-fiber (RoF) technology and an optical fiber network. The proposed distributed-type radar system offers both improved FOD detection characteristics and cost performance. This paper details the design and field feasibility evaluation of the 96 GHz frequency-modulated continuous wave radar system that uses RoF and an optical frequency multiplier. Firstly, the problem of long distance RoF transmission, which limits the practical use of the RoF networked radar system in the airport environment, is discussed. Secondly, the concept and architecture of the millimeter-wave radar system are discussed and demonstrated focusing on its use in actual airports. Then, the results of a field experiment are shown to confirm the feasibility of the radar system. Finally, the effectiveness of the high-speed signal processing and generation circuits inside the central unit is evaluated at an actual airport based on the results of non-coherent and coherent signal integration.

Reflectarray Element Using Cut-Ring Patch Coupled to Delay Line

In this letter, new phase-shifter cells for reflectarray applications using the cut-ring patch coupled to the delay line through an annular slot are presented. The new configuration allows the phase shift to be obtained by adjusting the length of a single or two different delay lines. Various prototypes of the elements have been fabricated and measured in X-band using the waveguide simulator technique. A good agreement between the measurement and simulation for both reflection phase and magnitude is achieved. Experimental results indicate good characteristics of the reflectarray element with a wide range of reflection phase and good linearity of the phase curve.

Microwave shielding and polarization characteristics of carbon fiber reinforced plastic laminates with unidirectional materials

The electromagnetic shielding and polarization characteristics of carbon fiber reinforce plastics (CFRP) based on unidirectional (UD) materials are determined by experiments. The UD CFRP laminates have single direction carbon fibers, which behave the same as wire-grid structures. The measured transmission coefficient for the 1 ply UD CFRP laminate is about -2dB, when the direction of the carbon fiber is perpendicular to the incident wave. The polarization ratio is more than 20dB for most frequency points. In addition, it is confirmed that the transmission coefficient can be controlled by rotating the UD CFRP laminates.

Design and construction methodology of 96 GHz FMCW millimeter-wave radar based on radio-over-fiber and optical frequency doubler

To detect small debris on the airport surface, the optically-connected distributed-type 96 GHz millimeter-wave radar system, which is based on radio-over-fiber (RoF) technology and an optical fiber network, has been proposed and developed. Such foreign object debris (FOD) is required to be removed immediately. The distributed-type radar system enables the improvement of both the FOD detection and cost performance. In this paper, design and construction methodology of the 96 GHz frequency-modulated continuous wave radar system based on the RoF and optical frequency doubler is discussed. The architecture of the millimeter-wave radar system, which is designed to enable a long distance RoF transmission, is demonstrated. In addition, the effectiveness of the high-speed signal processing circuit inside the central unit is evaluated at an actual airport.

Experimental feasibility study of 96 GHz FMCW millimeter-wave radar based upon radio-over-fiber technology-fundamental radar reflector detection test on the Sendai airport surface-

Based on radio-over-fiber (RoF) technology, we have proposed a novel architecture foreign object debris (FOD) detection system. The FODs on the airport surface may cause damage to aircraft and must be immediately removed. The optically-connected millimeter-wave radar with separated front-ends enables both low-cost and high-detection performance. In this paper, the feasibility and effectiveness of the 96 GHz optically-connected millimeter-wave radar is experimentally confirmed through the target detection test on the airport surface. The distributed millimeter-wave radar system, which is connected by the RoF converter, is fabricated. In addition, the radar reflectors, which are located on the apron of the Sendai airport, are successfully detected by the radar system.