Luneberg lenses are common in X or K band applications such as radar reflectors or multi beam antennas for satellite communications. However, for conventional electromagnetic waves lenses, there is serious loss over 20GHz. In automobile applications, millimeter wave radar is now spreading all over the world for use in collision avoidance systems. The placement of radar reflectors with obstacles at the sides of roads is also one solution to avoiding collisions using radar.

This paper describes a new concept for a dielectric lens which could be made available in millimeter wave range and light range. It contains a spherical shell and a spherical lens.

As an example of its application, we propose a lens reflector with the aluminum film on the inside wall of the outer shell. Its Radar Cross Section (RCS) is evaluated in W band. It performs at 5dBsm (dB square meter) RCS at 76GHz and 94GHz maximum. Its reflection is observed in the 90 degree angle range corresponding to the angle covered with the metal reflector. The reflection deviation is below 2dB in wide frequency band. It reflects not only millimeter wave but also light and near infrared wave.

Helicopters mainly fly at low altitude under visual flight rules and many accidents occurred when helicopters have struck power lines in good weather conditions. Pilots sometimes have difficulty to see long thin objects such as power lines even with good visibility.

In order to enhance detection ability, many kinds of obstacle detection and collision warning systems are now under development. ENRI is also trying to find a solution to reduce these kinds of accidents for civil helicopters. Such a system requires detection ability for obstacles at 800m with visibility enhancement under all bad weather conditions. It must also perform all of the process in real time within 1 second.

This paper describes the results of feasibility flight tests of a system developed by ENRI. The paper is divided into five parts, according to research topic, as follows;

(1) Section 2 describes ground tests of an IR camera capable to detecting power lines, with built-in image processing. IR imager provides a shape of obstacles such as power lines, locate as far as 1,000m away. Image processing enhances the shape of objects such as power lines within 100msec.

(2) Section 3 describes millimeter wave radar hardware and software. The radar emits 20.17dBm and the maximum range achieved is more than 800m. Nearest target extraction is installed in radar signal processing.

(3) Section 4 describes the development of a radar antenna, because there are few choices for this application. A primary source using slot array performs with -20dB reflection losses. A number of Fresnel reflector antennas are also manufactured. Folded reflector antennas provide 36 dBi of gain with back side feed.

(4) Section 5 describes the concept of a total system using a CCD camera, an infrared camera, and a millimeter wave radar. We present a solution to show color fusion images plus an IR images with distance information from the radar.

(5) Section 6 describes the results of feasibility test. The system detects obstacles such as power lines located at 800m range with image enhancement. Its refresh rate exceeds 8 frames per second with smooth flow of the processed movie.

We conclude that the proto-type system indicates the feasibility of power line detection using millimeter wave radar and an IR camera.

In order to meet the demand and keep the safety of air traffic, ENRI (Electronic Navigation Research Institute) studies on leveraging data-link function of SSR (Secondary Surveillance Radar) mode S and tries to apply it to the improvements of CA (Conflict Alert) which supports air traffic controller to keep safe separations between aircraft. Our purpose is to develop new DAP-CDM (Downlink Aircraft Parameters-Conflict Detection Method) and evaluate the impacts of its introduction by computer simulations.

First, for considering DAP-CDM, we calculated horizontal and vertical prediction errors of aircraft position estimated by the conventional CDM. As a result, both prediction errors were reduced by using flight data instead of radar data. We also found that it was better to smooth vertical speed for prediction and to utilize selected altitude in DAP-CDM. Then, occurrences of CA were analyzed to understand the effects of prediction error reduction. Currently, a large number of CAs were displayed for less than 20 seconds and often intermittently. When CA happened with a large altitude difference more than 10,000 ft, vertical flight phases of aircraft were the combination of climbing and descending. Under that condition, the changes of flight phase into level flight were rarely observed by judging from their later tracks. Therefore, smoothing vertical speed and utilizing selected altitude in DAP-CDM were considered to be necessary.

For the purpose of comparing DAP-CDM with the conventional CDM, ENRI developed CDES (Conflict Detection Evaluation System). It can simulate both the new and conventional CDMs under air traffic situations and system parameters as almost same as the conventional ones. Finally, the characteristics of DAP-CDM were studied and its advantages were demonstrated. DAP-CDM has the function of predicting aircraft positions by using smoothed aircraft horizontal velocity and vertical speed, and judging aircraft flight phases by using roll angle and selected altitude. As a result of evaluating DAP-CDM by the simulation with CDES, the judgment of vertical flight phases by selected altitude was most effective to reduce the number of unnecessary CA.