ប្រព័ន្ធការពារអាកាស

The Air Defense System (ប្រព័ន្ធការពារអាកាស)

A simple air defense system model includes a track radar server, a command center, and a weapon. In this paper, the​ tracking radar is emphasized with the command center and the weapon system adding additional context. The tracking operation involved in air defense systems refers to the continuous measurement, estimation and maintenance of data about the kinematic state (position and velocity) of one or more targets. A single target tracking radar (STTR) implies a dedicated radar used to track a single target. Typically, a command issued from a Command Center to the radar gives the general

coordinates of the object to be tracked in the form of azimuth (rotation angle), elevation, and range of the desired target. The STTR then slews to the designated angles, performs a local volumetric search, and then detects and acquires the target.

Using the Shlaer/Mellor model as described in [56], the block diagram in Figure 4 illustrates the relationship between the Command Center, the Radar, and the Weapon system. A one-to-many (single arrow to double arrow in Figure 4) relationship exists between the Command Center and the Track Radar, and the Command Center and the Weapon. It is shown that there is a one-to-one (single bi-directional arrow in Figure 4) relationship between a Track Radar and a Weapon. This situation is generally true and indicates that while the Command Center has to typically handle (selective) broadcast communications ( both Track Radar and Weapons), while the Track Radar and the Weapon system have a dedicated communication structure (point-to-point).The various processes involved between these subsystems are illustrated in Figure 5.

The radar consists of a transmitter-receiver pair, a pulse generator, an antenna, and a signal processing unit (SPU). The information from the radar is sent to a display at a command/monitoring center. The radar has several attributes, contained within the information model, that are pertinent to this paper. Some key attributes include: (i) power, (ii) antenna gain and bandwidth, (iii) position (iv) pulse width, and (v) pulse repetition frequency (PRF). The weapon agent5 has the following significant attributes: (i) weapon type, (ii) amount of ammunition remaining, and, (iii) position. Typical STTR pulse modulates with a RF carrier frequency of 5000 to 14000 MHz with a pulse width of .2 to 1.0 micro-seconds. After amplification, the radar transmits the pulse in the direction of the antenna bore sight axis. If the transmitted pulse encounters a target, a fraction of the signal is reflected back to the radar and a fraction of this reflected signal is intercepted by the antenna aperture. The signal arriving at the antenna is amplified, processed, and displayed at the command/monitoring center. Typically, the pulse train consists of equally spaced pulses. The pulse repetition frequency (PRF) is the number of pulses transmitted per unit time. The pulse repetition interval (PRI) represents the time between pulses and is equal to the reciprocal of the PRF. Let d be the maximum round trip travel time of a pulse (from the radar off the target and back to the radar). In practice, d < PRI. Otherwise, there will be range measurement ambiguity among the transmitted pulses. Typical PRF values may range from 500 to 1500.

The range gate is defined as the time when the STTR is expecting a pulse from the desired target. The radar “slews” to the appropriate coordinates and then positions a range gate. This process usually takes less than a second. During the range search, the time when the gate turns on and the duration of the gate are varied according to a pre-programmed pattern until a pulse arrives at the gate. Angle search occurs concurrently, but it is not directly considered here. This pattern generally differs between different radars. After the target is acquired, the radar begins to track the target, that is, the radar

A dedicated weapon system works in conjunction with most STTR used in real-world applications. Similar to the radar, the weapon system will “slew” to desired coordinates when instructed to track a target by the command center. If the target is evaluated as hostile, an engagement decision may be made and the command center will issue an engage order to the weapon system. Figure 6 is the object model of a STTR using the Rumbaugh model [52]. The model contains the constituent parts and attributes of the STTR as described above. Note that the TrackRadar inherits all the information from the basic Radar system. The next section describes the behavioral model of the air defense system