PRECO’s PreView Sentry and Side Defender systems employ radar technology that detects both moving and stationary objects. These systems are based on Continuous Wave radar, a proven technology that has been around for decades. The earliest large-scale applications of continuous wave radar were for such things as weather radar and missile guidance. A newer variant of this technology, called Frequency Modulated Continuous Wave (FMCW), is now becoming a mainstay in the machinery and automotive industries.
A Quick Guide to FMCW Radar
FMCW is a hybrid radar technology that blends together two different radar technologies, Doppler radar and Pulsed radar, to maximize functionality and performance while minimizing limitations. One of the most important differences between FMCW and Doppler radar is FMCW’s ability to detect stationary objects.
In a nutshell, pulsed radars detect objects by transmitting a burst of energy and then listening for some of that energy to be returned back to the radar after bouncing off an object. Pulsed radars main limitation is its limited range, because of the low amount of power allowed to be transmitted. Doppler radars operate by transmitting a fixed frequency and looking for a change in that frequency caused by a moving object. If the object is not moving there will be no frequency change, and the object will not be detected.
FMCW radar, on the other hand, operates by varying the radar signal during transmission. FMCW radars transmit a constant radar signal or “pulse” that increases linearly in frequency while transmitting. The radar then analyzes the energy of the pulse that returns after bouncing off an object. Based on that analysis of the shift in frequency between the pulse it transmitted and pulse it receives, FMCW is able to detect that object—even if that object is stationary.
In the picture below the red is the transmitted energy of an FMCW radar and the green is the returned energy after bouncing off an object. The difference in the frequency, time, and phase are all processed to determine the speed, location, and distance to the detected object.
The Big Difference: Stationary Object Detection
To the casual person, the differences between how the many forms of radar detect objects may seem slight. But these differences are what allow FMCW to have greater range resolution, consistency and, most importantly, to be able to detect both stationary and moving objects. It is this combination of detection abilities that makes FMCW radar a major contributor to worksite safety.
Detecting Objects in Time and Space
Another feature that distinguishes FMCW from other radars is the ability of its transmit antenna to transmit pulses at the same time its receive antenna receives pulses. This combination provides virtually instantaneous range, velocity, and target angle data for multiple targets. This data can be used to locate these objects on a three dimensional map of the detection area, or to eliminate unwanted detections by ignoring objects that lie outside of the target area.
More Powerful Radar
The way FMCW operates allows it to legally transmit at a much higher power than other radar technologies, resulting in longer-range detection capabilities. This ability to detect far-away objects is particularly important when the radar is used on very large machines or vehicles traveling at higher speeds.
The Complete Radar Solution
With its ability to detect both stationary and moving objects, locate objects in all three dimensions, and detect far-away objects, Frequency Modulated Continuous Wave radar is rapidly becoming the preferred standard for improved vehicle safety. We have only begun to see how FMCW can be implemented to improve safety on work sites and roads.