Introduction

Introduction

DOI: 10.4018/978-1-5225-5436-3.ch001

Abstract

Although the airborne radar introduced many advantages over other radars, such as ground radars, in detecting high speed air targets, it suffers from many problems. These problems can be concluded as, first, the range migration problem that happens due to the high relative speed between the airborne radar and the high speed air targets and the Doppler ambiguity estimation problem; second, the limited input dynamic power range of the radar receiver and the power loss due to targets range; third, the effects of jamming and clutter which are more effective than ground radars; and finally, the airborne system is a perfect target for enemy threats such as jamming and spoofing.
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Radar Basics

Radar is an acronym for Radio Detection and Ranging (Skolnik, 1980; Leydorf, 1971). Radar is often used to detect objects that are not visible to our naked eyes. In a commercial context it is widely used in safety applications, such as in air traffic control or speed cameras. Radar can be used as an offensive or defensive tool in a military context. Controlling the air space is the key element in modern warfare.

Figure 1 shows the general radar system block diagram, it shows the contents of the radar system.

Figure 1.

General radar block diagram

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The start of any modern arms conflict is usually marked with the destruction of the enemy radar system. Having a modern and reliable radar system plays a significant part in determining the outcome of the conflict. With the help of airborne and space borne radar, intelligence about the enemy units can be readily available before the battle even begins. Besides being able to look further into the enemy territory and detect low flying aircraft and vehicles in a hilly landscape, airborne bistatic radar survivability is greatly increased by positioning the transmitter in a “safe” location while the receiver is in the enemy airspace operating in the passive mode. The greatest advantage of airborne bistatic radar is its ability to possibility detects targets which employ stealth technology. Using stealth technology, the radar cross section (RCS) of target is reduced in the forward scattering direction, making target returns harder to separate from the noise.

Some objects can be detected and located at far greater distances than a naked eye can see, using the applications of electromagnetic waves. This sensing is not affected by most obstacles to ordinary vision like night, cloud, fog and smoke. In addition, radar permits the accurate measurement of the range and velocity of what it senses with a precision cannot be obtainable by a human operator. Some other aspects of radar performance are poorer than that of the eye (Frieden, 1985).

In Figure 2 the different available types of radar systems has been presented.

Figure 2.

Different types of radar systems

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Monostatic radar refers to a radar system which has the transmitter and receiver located at the same site. It has been the most widely used radar since it was developed in the late 1930s, primarily because it is easier to operate and usually - but not always - performs better than bistatic radar.

Although monostatic means stationary, in airborne radar engineering it is used to address an individual radar system. By having radar on an aircraft, it enables the radar to look from above and further into the enemy territory. Looking from above, detection of low flying aircraft and vehicles in a hilly landscape is improved. However, by doing so, two serious problems are encountered.

Radar systems currently in operation can generally be divided into airborne and space borne systems, depending on whether the platform carrying the radar is an aircraft or a satellite. The main differences between both systems arise from the different viewing geometry and swath coverage, caused by the difference in flight or respectively orbit altitude, and their operational flexibility.

Radar uses electromagnetic (EM) waves for detection and ranging. Typical Radar system consists of transmitter, receiver, processor, antenna, and display sub system. Radar when used in airborne platform has more design and operation challenges with distinct applications. In 1936 the first Airborne Radar was introduced by radio detection and ranging with transmitter valve 316A operated on 200 MHz frequency with receiver IF of 45 MHz and the range was 10 Km. Airborne radar has stringent restriction of size, weight and demands high reliability and airworthiness. The airborne radar is subject to more stress and requirements like high temperature fluctuations, atmospheric and mechanical stresses as compared to ground Radar. There are various types of classifications for types and applications it depends upon waveform, platform, usage, power etc.

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