SAE J3088:2017 pdf free

SAE J3088:2017 pdf free.Active Safety System Sensors
There are two general methods of measuring distance using radar, described in 6.1 The first is known as the direct propagation method and measures the delay associated with reception of the reflected signal which can be correlated to the distance of the reflecting object as a function of the speed of light and the period, or rather, the time delay in the transmission and receiving of the reflected waves. The second group of methods, known as indirect propagation, are methods where a modulated frequency is sent and received. The difference in the frequency can be used to directly determine the distance as well as the relative speed of the object.
Radar signals are very good at detecting objects that strongly reflect electromagnetic radiation (e.g., metal objects). Because they operate at wavelengths on the order of a few millimeters, automotive radar systems are pretty good at detecting objects that are several centimeters or larger. They are also good at looking through objects that are small relative to the sensor wavelength (e.g., the water droplets in fog)5.
Radars determine the angular position of an object using multiple overlapped antenna beams (or similar technology), digital beam forming, or mechanical steering of the beam to scan the space.
Pulsed radars typically suffer from blind speed and ambiguous range issues. In addition, transmitting a narrow pulse in the time domain means that a large amount of power must be transmitted in a short period of time. In order to avoid this issue, spread spectrum techniques may be used.
In continuous-wave (CW) radars, a high-frequency signal is transmitted and by measuring the frequency difference between the transmitted and the received signal (Doppler frequency), the speed of the reflector object can be estimated. These systems are incapable of detecting the target range and they cannot distinguish between objects moving toward or away from the transmitter. The direction ambiguity can be eliminated by extracting the sign of the Doppler frequency using quadrature architecture.SAE J3088 pdf free.