112
5 Performance Characteristics of Radar Location …
Listed requirements in some cases are contradict one another. At instantaneous
scanning, the indicated contradictions are removed, but great difficulties arise in
satisfaction of the last requirement—equipment becomes a multichannel and more
sophisticated.
5.4 Resolution Capability of Radar Location and Radio
Navigation Systems
One of the main radar and RNS characteristics is its resolution capability, i.e., a
possibility of separate detection, coordinates measuring or movement parameters
of several objects located in surveillance zone. In some cases, it differs a target
resolution in range, velocity (in Doppler frequency) or in angular coordinates.
It is admitted to evaluate a resolution capability in minimum interval value between
two targets by corresponding coordinate or targets movement parameter. It is assumed
that resolution value by one or another coordinate is defined at equal values of other
coordinates or targets movement parameters.
Targets resolution means a possibility at radar surveillance to answer the following
questions: What is the relative position of targets in space, what are its relative
velocities, how much targets are observed and what its specific features (e.g., RCS)?
Radar resolution capability at the most defines a possibility of detection and
target coordinates measuring at the background of returns (clutters), passive and
active jamming of different origins. Consequently, a resolution capability is important enough at evaluation of radar interference immunity and at development of
countermeasures systems. Particularly, passive jamming and different interfering
reflecting surfaces can be examined as aggregate of targets which are of no interest
at observing of some assigned target, but using resolution capabilities, it is possible
to select this assigned target, provide its detection and determine its coordinates and
moving velocity.
As it mentioned before, a resolution standard in the examined case can be such
interval between input signals for two targets, at which it is possible to observe
independently the separate maximums, and a “gap” (“null”) between them does not
exceed some specified value relatively to a maximum value of output signal.
According to Rayleigh criterion (introduced for the first time in optics), output
responses in a form of function (sinx)/x are examined. As defined in this criterion,
two equal output signals are differ, if a maximum of one signal coincides with a
minimum (zero) value of another (Fig. 5.23).
Herewith, a null is originated of not more than 20% from a maximum (peak) value.
In this case, an interval between maximums numerically equals to response width of
output signal (for a point object of observing). Hence, according to Rayleigh criteria,
two targets are resolved (in corresponding coordinate), if an interval between them
δα is not less than response width of output signal α out
5 Performance Characteristics of Radar Location …
Listed requirements in some cases are contradict one another. At instantaneous
scanning, the indicated contradictions are removed, but great difficulties arise in
satisfaction of the last requirement—equipment becomes a multichannel and more
sophisticated.
5.4 Resolution Capability of Radar Location and Radio
Navigation Systems
One of the main radar and RNS characteristics is its resolution capability, i.e., a
possibility of separate detection, coordinates measuring or movement parameters
of several objects located in surveillance zone. In some cases, it differs a target
resolution in range, velocity (in Doppler frequency) or in angular coordinates.
It is admitted to evaluate a resolution capability in minimum interval value between
two targets by corresponding coordinate or targets movement parameter. It is assumed
that resolution value by one or another coordinate is defined at equal values of other
coordinates or targets movement parameters.
Targets resolution means a possibility at radar surveillance to answer the following
questions: What is the relative position of targets in space, what are its relative
velocities, how much targets are observed and what its specific features (e.g., RCS)?
Radar resolution capability at the most defines a possibility of detection and
target coordinates measuring at the background of returns (clutters), passive and
active jamming of different origins. Consequently, a resolution capability is important enough at evaluation of radar interference immunity and at development of
countermeasures systems. Particularly, passive jamming and different interfering
reflecting surfaces can be examined as aggregate of targets which are of no interest
at observing of some assigned target, but using resolution capabilities, it is possible
to select this assigned target, provide its detection and determine its coordinates and
moving velocity.
As it mentioned before, a resolution standard in the examined case can be such
interval between input signals for two targets, at which it is possible to observe
independently the separate maximums, and a “gap” (“null”) between them does not
exceed some specified value relatively to a maximum value of output signal.
According to Rayleigh criterion (introduced for the first time in optics), output
responses in a form of function (sinx)/x are examined. As defined in this criterion,
two equal output signals are differ, if a maximum of one signal coincides with a
minimum (zero) value of another (Fig. 5.23).
Herewith, a null is originated of not more than 20% from a maximum (peak) value.
In this case, an interval between maximums numerically equals to response width of
output signal (for a point object of observing). Hence, according to Rayleigh criteria,
two targets are resolved (in corresponding coordinate), if an interval between them
δα is not less than response width of output signal α out