In this lecture, we are going to learn about the Target Resolution of Radar, also we will discuss the types of Target Resolution of Radar in every detail. So let’s start with the definition of the Target Resolution of Radar.
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Target Resolution of Radar
The Target Resolution of a Radar is its ability to disinguish bwtween the tragets that are very close together in either range or bearing.
- Weapons-control radar, which requires great precision, should be able to distinguish between targets that are only yards apart.
- Search radar is usually less precise and only distinguishes between targets that are hundreds of yards or even miles apart.
- Resolution is usually divided into two categories:
| 1. | Range Resolution in radar |
| 2. | Azimuth Resolution Or Bearing Resolution |
1. Range Resolution in radar
Range Resolution is the ability of a radar system to distinguish between two or more targets on the same bearing but at different ranges.
- The degree of range resolution depends on the width of the transmitted pulse, the types and sizes of targets, and the efficiency of the receiver and indicator.
- Pulse width is the primary factor in range resolution.
- A well-designed radar system, with all other factors at maximum efficiency, should be able to distinguish targets separated by one-half pulse width time.
- Therefore, the theoretical resolution of a radar system can be calculated from the following formula:
\boxed{\mathbf{R_{RES} = c \times PW/2}}
- The above formula is often written as:
\boxed{\mathbf{R_{RES} = c /2 \beta}} ; \mathbf{because ( PW= 1/ \beta)}
where \beta is the bandwidth of transmitter pulse.
- For example, if a radar system has a pulse1 width of 5 microseconds, the range resolution is calculated as follows:
R_{RES} = c \times PW/2
R_{RES} = 3 \times 10^8 \times 5 \times 10^{-6} /2
R_{RES} = 3 \times 5 \times 10^{2} /2 = 7.5 \times 100
R_{RES} =750 \;m
- In the above example, targets on the same bearing would have to be separated by more than 750m to show up as two targets on your indicator.
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2. Azimuth Resolution | Bearing Resolution
Bearing Resolution or Azimuth Resolution is the ability of a radar system to separate objects at the same range but at different bearings.
- The degree of bearing resolution depends on the radar beam width and the range of the targets.
- The range is a factor in bearing resolution because the radar beam spreads out as the range increases.
- A Radar beam is defined in width in terms of Half-power points. All the points off the centerline of the beam that is at one-half the power level at the center are plotted to define beam width.
- When the half power points are connected to the antenna by a curve, such as that shown in the figure below, the resulting angular width of the curve is called the Antenna Beam Width.
- The physical size and shape of the antenna determined beam width. The beam width can vary from about 1 degree up to 60 degrees. In the below figure, only the target within the half power points will reflect a useful echo.
- Two targets at the same range must be separated by at least one beam width to be distinguished as two objects.
