The 76-GHz millimeter-wave band has come into widespread use for things like motor vehicle radar, although the 79-GHz band is also expected to become popular for its higher resolution. But as radar systems become more widespread and more modulation types are used, there is a growing need to study in detail whether or not interference occurs. Because millimeter-wave radar uses a wide bandwidth, it has been difficult to perform analyses of interference from different modulation types with general purpose PCs using conventional approaches because of their limitations in processing performance.
This technology can be used in simulations when developing and testing interference-avoidance algorithms as a way of preventing object-recognition oversights and mistaken detections and developing more reliable automotive radar systems. This research was conducted through R&D to "
Millimeter-wave radar works by emitting radio waves in the millimeter band toward an object and using the reflected waves to measure the distance and speed of the object. In recent years, millimeter-wave radar in the 76-GHz band has become increasingly popular as automotive radar for detecting nearby obstacles and for implementing adaptive cruise control that responds to traffic conditions. It is also placed at crossings and along streets to detect hazards. Radar for monitoring infrastructure systems, such as traffic conditions, has also been commercialized.
To detect pedestrians and other small targets, however, there is a need to improve resolution. For this reason the 79-GHz band, which can achieve higher resolutions with a broader range of frequencies, is expected to become increasingly popular. In the 76-GHz band, continuous-wave modulation techniques, such as FM-CW radar(3), have been most commonly used, as they allow for simpler transceiver circuit designs. With the 79-GHz band, improvements in circuit technology and a wider frequency-band allocation lead to an expectation that spread-spectrum radar(4) will come into use. Because these various techniques for millimeter-wave radar are going to be used at the same time, there is a need for simulation technologies in order to study in detail whether or not interference will occur.
Millimeter-wave radar covers an extremely broad spectrum, from hundreds of megahertz to four gigahertz. The existing method for calculating interference between different radar techniques has required calculations across a wide band in minute frequency steps, which in turn requires that the computer running the calculations have considerable memory and processor resources-more than can typically be found on a desktop computer. An alternative method is to build test radars and discover the effects of interference experimentally, but because of the difficulty of performing tests that can accurately capture frequencies between radars and synchronize them in time, such experimental methods can only be used under limited conditions.
About the New Technology
Now, by creating a mathematical model of interference in FM-CW radars and spread-spectrum radars that simplifies analysis without sacrificing precision,
The existing method for calculating interference between different radar techniques has required calculations across a wide band in fine frequency increments, which makes analysis very time consuming. The frequency and time increments can be made coarser, but this results in less-precise analysis. In calculating based on a mathematical model,
This technology makes it possible to quantitatively calculate to what extent and under what conditions interference occurs between different types of radar. Also, because it can be used in simulations when developing and testing interference-avoidance algorithms, highly reliable automotive radar systems can be expected to be developed to prevent object-recognition oversights and detection errors.
Practical testing of a recently developed interference-avoidance algorithm is on track for the end of fiscal 2013. Products incorporating this interference-avoidance algorithm will follow.
(1) Millimeter wave:Electromagnetic waves with a wavelength of 1-10 mm (frequency of 30-300 GHz).
(2) Automotive radar:A device that detects obstacles near vehicles by emitting radio waves and detecting their reflections.
(3) FM-CW radar:A type of radar that emits a frequency-modulated continuous wave and uses the difference between the emitted frequency and the frequency that is reflected back to determine distance and relative speed.
(4) Spread-spectrum radar:A type of radar that emits a signal spread over a wide band using spread modulation and uses the delay time between highly correlated outgoing and incoming waves to determine the distance to obstacles.
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