What is in this article?:
- Radar Systems Scan The Skies
- Driving Growth
Radar systems have been adapted to a wide range of applications since their development during World War II.
In spite of their traditional association with military applications, radar systems are steadily finding their ways into commercial applications. Even though collision-avoidance radar systems operate at millimeter-wave frequencies at 77 GHz, an increasing number of integrated-circuit (IC) suppliers are finding ways to design and fabricate practical 77-GHz radar transceivers for this fast-growing application. A number of different frequency bands have been explored for this use of radar, including at 24 GHz. Some of the world’s leading suppliers of ICs are developing transceiver chipsets, including Analog Devices, Freescale Semiconductor, Infineon Technologies, and TriQuint Semiconductor.
These devices support a number of different grades of vehicular collision-avoidance radar systems, including for unmanned ground vehicle (UGV) systems. Some of these collision-avoidance systems incorporate frequency-modulated-continuous-wave (FMCW) technology, with velocity of a target measured by distance over time. Others use pulsed Doppler techniques, with velocity and distance to a target measured instantaneously.
Automotive radar is a market and technology that is experiencing a great deal of development, as these systems expand from just high-end automobiles to lower-priced vehicles as the radar electronics becomes more affordable. Because of the lack of established standards for the technology, it is not yet a commodity application, but is available in a number of different formats; these include narrowband and ultrawideband (UWB) systems. In addition, radar system (and automotive) manufacturers are not always familiar with the component-level specifications and how they relate to radar systems. This communication must improve for automotive radar systems to become more widely spread.
Current automotive radar systems include the electronically scanned radar (ESR) system from Delphi, a multimode system that provides wide coverage at midrange distances and high resolution at long distances using a single radar beam. This type of coverage and its associated processing can identify both vehicles and pedestrians across the width of the equipped vehicle and can detect as many as 64 targets in the path of an equipped vehicle. The data from the ESR system can be applied to a number of functions, including adaptive cruise control and forward collision-warning capability. Delphi’s 77-GHz ESR system is powered by a number of gallium-arsenide (GaAs) ICs from TriQuint Semiconductor.
Freescale has been active in the development of chipsets for Advanced-Driver-Assistance-Systems (ADAS) applications, including for implementation and control of the 77-GHz collision-avoidance radar system and the front- and rear-view cameras in each vehicle. The 77-GHz radar chips support a number of applications, including adaptive cruise control (ACC), blind-spot detection (BSD), emergency braking, forward-collision warning (FCW), and rear-collision protection (RCP). For reliability and safety, its semiconductor solutions are based on system-in-package (SiP) technology. These use widely accepted communications protocols—such as PS15 and DSI—for interaction with other vehicular electronic systems, like the airbag systems.
In addition to making traffic safer, commercial radar systems are also helping to predict coming weather patterns and track storm systems. Weather radar systems use radar returns to help determine the intensity and relative speed of a storm system. These radar systems typically operate at a wavelength of 10 cm, which is a frequency of about 3000 MHz, using very short pulses at about 1000 pulses/s. Weather radar systems employ one of two scanning techniques. In the plan-position-indication (PPI) approach, the radar holds its elevation angle constant but varies its azimuth angle. A 360-deg. scan is called a surveillance scan, while a scan of less than 360 deg. is a sector scan.
In the range-height-indication (RHI) approach, the radar holds its azimuth angle constant but varies the elevation angle. The elevation angle is typically rotated from the horizon to the zenith, or a point in the sky directly overhead. A Weather Service radar usually requires a series of surveillance scans at increasing elevation angles to collect adequate data for analysis.
The Next Generation Weather Radar, NEXRAD, can detect air motion through the use of Doppler measurements and analysis. Hundreds of NEXRAD sites have been constructed across the United States to aid with weather analysis and predictions, since the systems have the capability to detect cold fronts and thunderstorm fronts.
One of the more intriguing uses of radar technology has been for planetary exploration. Using either an Earth- or space-based radar antenna and system, a narrow beam is transmitted into space to illuminate a distant target. Doppler measurements can provide information about the relative speed of the target, whether a planet, comet, asteroid, or even a wayward satellite. Such planetary radar was first applied in 1946 when a radar system illuminated the moon and provided some insight into its sand-like structures. In many ways, radar technology is only beginning, with many more applications still to be found for this particular use of EM energy.