Primary radar
Primary radar refers to radar systems that implement the radar principle exclusively and directly, i.e. H. analyze the immediate (passive) echoes of previously emitted high-frequency pulses .
The term is used to distinguish it from secondary radar , a technology in which actively generated echoes are used by detected objects.
In practice, a combination of both methods is often used (e.g. in air traffic control with ground penetrating radar ). A pure primary radar application is, for example, the systems used for speed measurement in road traffic (“radar trap ”).
advantages
Primary radar systems do not depend on an object actively generating signals in order to be able to detect it. This is e.g. B. in the area of air traffic control , since aircraft must be detectable even if the radio transponder has failed .
In the event of interference with the frequency used, primary radar systems can easily switch to other frequencies. With secondary radar systems, such a change can only be carried out successfully if it is also carried out by the objects to be detected.
disadvantage
Primary radar can only determine the variables that can be determined from the reflected echo (e.g. direction, distance and speed), while with secondary radar the receiver can integrate further information into its response (e.g. an identifier).
Primary radar systems require a significantly higher transmission power than comparable secondary radar systems in order to be able to achieve the same range.