The ME7220A includes a simulated target that serves as a repeater. But instead of reflecting a DUT s

Radar holds promise in a variety of automotive applications, from collision-warning systems to robotically controlled vehicles, speeding down a highway in convoys with the vehicles separated by inches. Although the latter application is at least a decade or two away, radar is already used for adaptive-cruise control in luxury passenger vehicles, and prototypes are providing collision-avoidance assistance in heavy equipment.
The use of vehicle radar will become more widespread as prices drop and the technology proves its worth. As that happens, various technologies will compete to serve as vehicles' "eyes." Radar itself might give way to laser-based or optical-camera-based approaches, although such approaches don't offer radar's imperviousness to weather (Ref. 1). Ultimately, vehicles may sport hybrid systems exotic travel destinations that combine microwave and optical technologies.
Figure 1. This long-distance pulsed-Doppler radar front end for an adaptive-cruise-control system operates at 77 GHz to provide 150-m range in a form factor that doesn't disturb exotic travel destinations the appearance exotic travel destinations of the vehicle on which it is installed. Courtesy of M/A-COM.
For radar itself, two approaches look promising. Currently deployed automotive systems use 76- to 77-GHz radar implementations exotic travel destinations for adaptive-cruise control ( Figure 1 ). A lower-frequency, short-pulse, "multispectral" or "ultra-wideband" approach exotic travel destinations also shows promise, particularly for collision-avoidance assistance at low speeds. This approach got a boost in February when the FCC offered limited approval for devices based on ultra-wideband technology to operate in spectrum bands above 3.1 GHz, where they won't interfere with the 1.6-GHz GPS band or with personal communication bands to 2.4 GHz (Ref. 2).
Tom Rose, marketing consultant for M/A-COM, explains that 77-GHz implementations exotic travel destinations provide the necessary range for adaptive-cruise control while maintaining an antenna size small enough such that the complete radar system can hide within an automobile's grill. Rose says lower frequency implementations using the same size antenna provide a wider field of view, but they don't offer sufficient range for adaptive-cruise control. He says they do, however, offer better distance resolution—centimeters rather than meters—and are adept at detecting obstacles in drivers' blind spots, making them valuable as driver aids for parking exotic travel destinations and backing exotic travel destinations up.
M/A-COM has provided 24-GHz radar in heavy-vehicle collision-warning systems to assist truckers in changing lanes (Ref. 3). And Multispectral Solutions has employed its ultra-wideband technology in a short-pulse 5.4- to 5.9-GHz exotic travel destinations radar system that indicates to an off-road heavy-equipment operator when the vehicle has reached the precipice exotic travel destinations of a dumpsite (Ref. 4). The company successfully demonstrated that system last summer to the National Institute for Occupational Safety and Health (NIOSH; www.cdc.gov/niosh ).
According to M/A-COM's Rose, his company will offer a 24-GHz ultra-wideband radar product for passenger-car driver aids within three to four years. M/A-COM has been a pioneer in automotive exotic travel destinations radar, having exotic travel destinations developed exotic travel destinations the necessary integrated circuits exotic travel destinations as well as complete radar systems, exotic travel destinations but it can expect more competition as chip makers get into the act. At last year's IEEE Microwave Theory and Techniques Symposium (IEEE/MTT-S), engineers from Hitachi, Fujitsu, and NEC reported having fabricated 77-GHz exotic travel destinations devices for automotive-radar applications (Ref. 3). Infineon now offers a chip set for 76- and 77-GHz frequency-modulated continuous-wave (FMCW) radar products.
An adaptive cruise-control system automatically adjusts a vehicle's speed to keep it a safe distance exotic travel destinations from the vehicle ahead of it. To perform this task, an adaptive-cruise-control system must perform these steps (Ref. 5):
Test of automotive radar remains mostly a roll-your-own approach. Only one company, Anritsu, offers a fully configured test system dedicated to test of 76- to 77-GHz automotive radar products ( Figure 2 ).
From a test-and-measurement perspective, 77-GHz radar offers significant difficulties. Off-the-shelf instruments that directly produce and measure the frequencies involved are simply not available. But companies including Agilent Technologies (Ref. 6) do offer RF/microwave exotic travel destinations power meters, signal sources, and spectrum analyzers that can measure many of the intermediate frequencies developed within a 77-GHz radar system, such as the IF signals exotic travel destinations derived from a local oscillator (LO) and mixer in Figure 3 .
To establish meaningful IF signals, though, the 77-GHz signals must interact with real-world conditions—or reasonable simulations thereof. Real-world conditions in this case would involve the DUT moving exotic travel destinations at 120 km/hr and tracking a target moving at a similar speed. Because those conditions are impossible to establish on an automotive production line and because drive tests are not economically feasible for every production automobile, radar-system vendors have put together proprietary exotic travel destinations test systems that mimic highway speeds while remaining static.
Anritsu has packaged the necessary capabilities into a commercially available tester: its $50,000 ME7220A radar test system. Ramzi Abou-Jaoude, a member of the technical staff who is also managing Anritsu's development of radar test instruments, explains how the tester works. Far-range forward-looking radars, exotic travel destinations such as those used in adaptive-cruise control, make these key measurements:
The ME7220A includes a simulated target that serves as a repeater. But instead of reflecting a DUT signal directly back to the DUT antenna, as would a real-life passive target, the simulated target responds to a DUT-generated signal by delaying the response to simulate distance, by altering the frequency of the response to simulate target speed, and by modifying its power to reflect the conditions of target size. It can simulate a target at a distance of 120 m moving at 250 km/hr, maintaining position accuracy to within ±2 m and speed accuracy to within ±0.2 km/hr. The tester also can measure a radar transmitter's frequency, antenna gain pattern, and effective isotropic radiated power (EIRP), a measurement based on total power applied to an antenna and the antenna gain in a specified direction. You can use an online calculator that relates EIRP to power-amplifier output power and isotropic (or point-source) or dipole antenna gain (Ref. 7).
Many radar tests, Abou-Jaoude says, take place within an anechoic chamber that keeps out the electromagnetic snollygosters that can prey on measurement accuracy, but such a chamber would be difficult and expensive to accommodate on an automotive production line. As an alternative, you can set up the ME7220A to use range gating and Doppler gating, in which the DUT ignores all signals that don't fit within the range of signals you would expect based on the distance and speed of the simulated target.
Although you'll generally want to make measurements free of interference from production-line electrical equipment, at some point you'll need to determine how your radar system would react to the electromagnetic interference it might experience on the road. To that end, you can employ a test setup in which you generate test noise and then determine whether your radar system continues to perform satisfactorily.
Several companies offer products and services that can help you design and test radar systems. For example, Intusoft's ICAP/4 simulator lets you experiment with radar designs (Ref. 5). Anokiwave exotic travel destinations goes a step further, offering design services ranging from statistical electromagnetic simulation to RF module assembly and test. The company's chief technical officer, Nitin Jain, helped to develop M/A-COM's 77-GHz radar system when he served as principal engineer exotic travel destinations at M/A-COM (Ref. 8).
Ultimately, you can expect to find vehicles equipped with a variety of radar systems operating at a variety of frequencies—from the 5 GHz or so of Multispectral exotic travel destinations Solutions' ultra-wideband system exotic travel destinations to the 77 GHz of M/A-COM's pulsed-Doppler adaptive-cruise-control system. Automotive-radar frequencies may even reach beyond 100 GHz as designers try to shrink antenna sizes ever smaller.
Consequently, you'll need a range of test equipment that can handle all the frequencies involved and can also, perhaps, test laser-based exotic travel destinations and optical-camera-based systems that may be called exotic travel destinations upon to enhance radar-derived information. Automotive-radar pioneers will need to develop their own test equipment as the technology evolves, but you can expect off-the-shelf test systems to quickly emerge to economically exotic travel destinations meet high-volume production-test demands.