The radar has the meaning of "detecting with radio signals and measuring the distance" in English. The first name is "radiolocation". After World War II, the radar took the name and the word radar is formed by the combination of the capital letters of the words "Radio Detection and Ranging".
The bat, which, despite not seeing the eye, flew in the dark with mastery and caught his prey, played a great role in the discovery of radar. The bat publishing the ultrasonic frequency that the human ear cannot hear. The radar is basically sends and reflects electromagnetic waves.
Some air events can create or absorb electromagnetic field, some electronic warfare systems and various causal events have a negative effect on the operation of radar. Radar information uses to distance and direction detection.
Many scientists have contributed to the development of radar. In 1865, the British physicist James Clerk Maxwell introduced the electromagnetic wave theory and the theory of electromagnetic light which explains their spread. Maxwell's equations are the basis for radar and electromagnetic radiation. In 1886, German physicist Heinrich Rudolf Hertz discovered the electromagnetic waves and proved Maxwell's theory.
1904 German high frequency technician Christian Hülsmeyer invented the first example of radar ‘telemobiloscope’. The range is calculated by measuring the duration of the electromagnetic waves that multiply by a metal object with the telemobiloscope.
1921 Albert Wallace Hull invented a magnetron that produces a strong electromagnetic signal. The longer range and higher altitude come to radar by magnetron.
In 1936, Metcalf and Hahn signal generator (oscillator) and amplifier (amplifier) klystron were found.
1939 Two physicists from Birmingham University, John Randall and Henry Boot, developed a lightweight and powerful microwave radar. Since it is light, it has been attached to B-17 aircraft from military bomber aircraft. Research facilities have been established in many countries since radar began to be used more and more in military fields in the 1940s.
MDS (minimum detectable signal)
The use of radar has increased in many sectors especially military field from the 2nd World War. We can give example fields such as military radars, traffic radars, and social community security radars i.e.
Working system of the radar can explain like that the electromagnetic signal sends the pulses and only a small part of the high-energy pulse is reflected and this reflected signal named echo. The direction of the intensity of the echo and the time of return are very important for the radar. It is expected that the reflected echo from the electromagnetic signal transmitted by the radar should be above a certain level.
This level is called the ‘threshold value’ and the signal reflection on the threshold value is expected. The lowest echo power that can be defined as MDS (minimum detectable signal).
Radars have many units. As a control and timer (microcontroller), a fast-performing FPGA control unit is usually used in parallel operation. Oscillator and RF generate the signal and amplify this. The antenna is responsible for signaling and collecting signals. The duplexer unit which is behind the antenna, transmits the signal to the antenna and collects the signal from antenna.
The incoming signal is amplified with very low noise in the LNA unit. Special transistors are used in the LNA. LNA considered to be most important units of the radar because of the incoming signal can be distorted without being detected. Apart from these, the RF mixer unit changes the frequency according to the control unit. The AGF unit filtering the noise signals. All previous units are processing and preparing the signal and the finally the radar screen displays the signal.
Radars are separated air and sea radars according to their usage areas. Weather radars are used in military, meteorological, astronomical, airports and airplanes. Sea radars are used in military and commercial ships. Radars are also classified according to the frequency band they are working on.
Radar is used commonly in military field. Political relations and diplomatic work of the countries are the cause of this. For military purposes, many military radars are used in the electronic warfare, such as friendly-enemy recognition radars and enemy deception radars.
Various radar examples are given below.
