15-11-2012, 01:47 PM
Adaptive Active Phased Array Radars
[attachment=39588]
ABSTRACT
Adaptive active phased array radars are seen as the vehicle to address the current requirements for true ‘multifunction’ radars systems. Their ability to adapt to the enviournment and schedule their tasks in real time allows them to operate with performance levels well above those that can be achieved from the conventional radars. Their ability to make effective use of all the available RF power and to minimize RF losses also makes them a good candidate for future very long range radars.
INTRODUCTION
Over the years radar systems have been changing on account of the requirements caused by
a) Increase in the number of wanted and unwanted targets
b) Reduction in target size either due to physical size reduction due to the adoption of stealth measures
c) The need to detect unwanted targets in even more sever levels of clutter and at longer ranges
d) The need to adapt to a greater number of and more sophisticated types of electronic counter measures
Radar designers addressed these needs by either designing radars to fulfill a specific role, or by providing user selectable roles within a single radar. This process culminated in the fully adaptive radar, which can automatically react to the operational environment to optimize performance.
CATEGORIES OF RADARS
Conventional radars fall into two categories independent of what functions they perform. The first category has fixed antenna with centralized transmitters which produces patterns by reflector or passive array antennas. The beaming being fixed, scanning can only be achieved by physically moving the antenna. Typically surveillance radar will produce a fan shaped beam with a fixed elevation illumination profile, the azimuth scanning being achieved by rotating the antenna. A tracking radar will have a pencil beam that is used to track targets by the use of a mechanical tracking mount. Because of the limitations imposed on such radars by their design such radars are "single-function radars".
ADAPTIVE ACTIVE PHASED-ARRAY RADAR
Adaptive active phased array radars are seen as the vehicle to address the current requirements for true ‘multifunction’ radars systems. Their ability to adapt to the environment and schedule their tasks in real time allows them to operate with performance levels well above those that can be achieved from the conventional radars.
Their ability to make effective use of all the available RF power and to minimize RF losses also makes them a good candidate for future very long range radars. The AAPAR can provide many benefits in meeting the performance that will be required by tomorrow’s radar systems. In some cases it will be the only possible solution.
It provides the radar system designer with an almost infinite range of possibilities. This flexibility, however, needs to be treated with caution: the complexity of the system must not be allowed to grow such that it becomes uncontrolled and unstable. The AAPAR breaks down the conventional walls between the traditional systems elements- antenna, transmitter, receiver etc-such that the AAPAR design must be treated holistically.Strict requirements on the integrity of the system must be enforced. Rigorous techniques must be used to ensure that the overall flow down of requirements from top level is achieved and that testability of the requirements can be demonstrated under both quiescent and adaptive condition.
VOLUME SURVEILLANCE
The AAPAR can provide a number of operating mode to tailor surveillance volumes to the system or mission requirements. Energy usage is optimizes and the probability of target determination is maximized by the management of radar waveforms and beams. Volume surveillance can be managed in order to cope with varying threats - lower priority surveillance tasks can be traded for higher priority tasks such as short range surveillance or target tracking as the threat scenario changes.
TARGET IDENTIFICATION
Co operative technique use an IFF (Identification: Friend or Foe) integrated system controlled by a radar. Defending on the role of the radar, integration of target is performed only when the demanded, or on a continuous 'Turn and Burn' basis. Selective integration is used to minimize transmission from the radar to reduce the probability of ESM (Electronic Surveillance Measures) intercepts and is merely always used when mode 4; the secure IFF mode, is being used . Non cooperative technique extract additional data from radar returns by extracting features and comparing them with information held on threat date bases. A correlation process is used that finds the best fit to the data. This method can provide good accuracy in recognizing a target from a class of targets, or a specific type of targets.
TARGET TRAJECTORY CALCULATION
Calculation of an impact point is one input to the threat assessment process and the radar can assist by adapting to a mode that fits the trajectory to a complex curve fitting law. This process is more effectively performed by the AAPAR since it can adapt its tracking priorities and parameters and form the date quickly to the required accuracy.
TRACKING OF ECM EMISSIONS
Receive-only beams can be formed with an active array, giving all the normal receive processes without the need for transmitted RF. Utilizing these beams, sources of in band radiation can be accurately tracked in two dimensions. The track data can be correlated with strobes from other sensors to enable the positions of the jamming sources to be determined and tracked in conditions in which the presence of jamming may prohibit the formation of tracks.
[attachment=39588]
ABSTRACT
Adaptive active phased array radars are seen as the vehicle to address the current requirements for true ‘multifunction’ radars systems. Their ability to adapt to the enviournment and schedule their tasks in real time allows them to operate with performance levels well above those that can be achieved from the conventional radars. Their ability to make effective use of all the available RF power and to minimize RF losses also makes them a good candidate for future very long range radars.
INTRODUCTION
Over the years radar systems have been changing on account of the requirements caused by
a) Increase in the number of wanted and unwanted targets
b) Reduction in target size either due to physical size reduction due to the adoption of stealth measures
c) The need to detect unwanted targets in even more sever levels of clutter and at longer ranges
d) The need to adapt to a greater number of and more sophisticated types of electronic counter measures
Radar designers addressed these needs by either designing radars to fulfill a specific role, or by providing user selectable roles within a single radar. This process culminated in the fully adaptive radar, which can automatically react to the operational environment to optimize performance.
CATEGORIES OF RADARS
Conventional radars fall into two categories independent of what functions they perform. The first category has fixed antenna with centralized transmitters which produces patterns by reflector or passive array antennas. The beaming being fixed, scanning can only be achieved by physically moving the antenna. Typically surveillance radar will produce a fan shaped beam with a fixed elevation illumination profile, the azimuth scanning being achieved by rotating the antenna. A tracking radar will have a pencil beam that is used to track targets by the use of a mechanical tracking mount. Because of the limitations imposed on such radars by their design such radars are "single-function radars".
ADAPTIVE ACTIVE PHASED-ARRAY RADAR
Adaptive active phased array radars are seen as the vehicle to address the current requirements for true ‘multifunction’ radars systems. Their ability to adapt to the environment and schedule their tasks in real time allows them to operate with performance levels well above those that can be achieved from the conventional radars.
Their ability to make effective use of all the available RF power and to minimize RF losses also makes them a good candidate for future very long range radars. The AAPAR can provide many benefits in meeting the performance that will be required by tomorrow’s radar systems. In some cases it will be the only possible solution.
It provides the radar system designer with an almost infinite range of possibilities. This flexibility, however, needs to be treated with caution: the complexity of the system must not be allowed to grow such that it becomes uncontrolled and unstable. The AAPAR breaks down the conventional walls between the traditional systems elements- antenna, transmitter, receiver etc-such that the AAPAR design must be treated holistically.Strict requirements on the integrity of the system must be enforced. Rigorous techniques must be used to ensure that the overall flow down of requirements from top level is achieved and that testability of the requirements can be demonstrated under both quiescent and adaptive condition.
VOLUME SURVEILLANCE
The AAPAR can provide a number of operating mode to tailor surveillance volumes to the system or mission requirements. Energy usage is optimizes and the probability of target determination is maximized by the management of radar waveforms and beams. Volume surveillance can be managed in order to cope with varying threats - lower priority surveillance tasks can be traded for higher priority tasks such as short range surveillance or target tracking as the threat scenario changes.
TARGET IDENTIFICATION
Co operative technique use an IFF (Identification: Friend or Foe) integrated system controlled by a radar. Defending on the role of the radar, integration of target is performed only when the demanded, or on a continuous 'Turn and Burn' basis. Selective integration is used to minimize transmission from the radar to reduce the probability of ESM (Electronic Surveillance Measures) intercepts and is merely always used when mode 4; the secure IFF mode, is being used . Non cooperative technique extract additional data from radar returns by extracting features and comparing them with information held on threat date bases. A correlation process is used that finds the best fit to the data. This method can provide good accuracy in recognizing a target from a class of targets, or a specific type of targets.
TARGET TRAJECTORY CALCULATION
Calculation of an impact point is one input to the threat assessment process and the radar can assist by adapting to a mode that fits the trajectory to a complex curve fitting law. This process is more effectively performed by the AAPAR since it can adapt its tracking priorities and parameters and form the date quickly to the required accuracy.
TRACKING OF ECM EMISSIONS
Receive-only beams can be formed with an active array, giving all the normal receive processes without the need for transmitted RF. Utilizing these beams, sources of in band radiation can be accurately tracked in two dimensions. The track data can be correlated with strobes from other sensors to enable the positions of the jamming sources to be determined and tracked in conditions in which the presence of jamming may prohibit the formation of tracks.