Second, the type of waveform
There are many kinds of radar waveforms, which can be roughly divided into three types according to their fuzzy function forms:
1. Signals with knife-edge ambiguity function include constant carrier frequency pulse signal with positive knife-edge ambiguity function and LFM pulse signal with inclined knife-edge ambiguity function;
2. Pseudo-random coded signal with thumbtack ambiguity function:
3. Coherent pulse train signal with nail bed ambiguity function (see radar ambiguity). Except for the pulse signal with constant carrier frequency, the time-bandwidth wide product of other signals is greater than 1, which is collectively called the time-bandwidth wide product signal. Among them, the signals with oblique edge and thumbtack ambiguity functions are wide pulse coded signals.
Second, the research history is as follows:
1922, Taylor and Yang suggested that two warships should be equipped with high-frequency transmitters and receivers to search for enemy ships.
1924, appleton and barnett measured the height of the stage by radio waves reflected from the ionosphere. Blair and Duff in the United States use pulse waves to measure the Haveser layer.
193 1 year, the United States naval research laboratory developed a radar based on the beat frequency principle, and began to let the transmitter emit continuous waves, and switched to pulse waves three years later.
1935, a "learning cellar" with the wavelength of 16 cm was developed in Gudun, France. Other ships can be found in foggy days or at night. This is the beginning of the peaceful use of radar.
1936 65438+ 10 in October, W. Watt of Britain established the first radar station in Britain on the coast of Sofk. The British Air Force added five more aircraft, which played an important role in the Second World War.
1937 the radar XAF test of the first us warship was successful.
194 1 year, the Soviet union equipped early warning radar on the plane for the first time.
1943, MIT developed the plane position indicator of airborne radar, which can shoot moving aircraft. He invented the microwave early warning radar which can distinguish dozens of targets at the same time.
1947, American Bell Telephone Laboratory developed LFM pulse radar.
In the mid-1950s, the United States was equipped with a long-range early warning radar system to detect supersonic aircraft. Soon, pulse Doppler radar was developed.
1959, General Electric Company of the United States developed the ballistic missile early-warning radar system, which can launch and track missiles 3000 miles away and 600 miles high, with an early warning time of 20 minutes.
1964, the United States installed the first space orbit surveillance radar to monitor artificial earth satellites or spacecraft.
197 1 year, Iyuca, Canada and other three people invented the holographic matrix radar. At the same time, digital radar technology appeared in the United States.