radar determination of air targets
optimization of alphabet classes
repeated modulation of echo signals
continuous coherent signal processing
O.V. Vasiljev, V.A. Abaturov, A.S. Sytnikov, S.S. Korotkov, R.A. Potapov
In many applied problems of the RADAR is the core, and sometimes and a single radiant of a supply with information of a decision making. Special demands in this sense are shown to airborne radars at an estimate of air conditions owing to its high dynamism. Informational capabilities of the airborne radar at the solution of similar problems are to a great extent determined by efficiency of operation of the channel of a radar discernment and quality of algorithms of a radar discernment of the air targets implemented in the given channel.
System of a radar discernment, being the RADAR unit, should be under construction taking into account security most an effective utilization of system, singularities of its operation and technical feasibilities. It demands the registration of some factors known in the theory of a discernment which can be formulated as follows. At the preset character space and other equal requirements the diminution of number of class-rooms leads to reduction of recognition errors and, on the contrary, at magnification of number of class-rooms of system of a discernment for maintenance of the preset factors of merit it is necessary to dilate the dictionary of tags. In too time dilation of character space is interfaced to magnification expended temporary and power resources on which enough stringent restrictions are in actual practice superimposed.
Proceeding from told, design of algorithms of a radar discernment is interfaced to the solution of variety of the optimization problems linked directly with a discernment and the registration of particular requirements of its implementation.
Spent theoretical and experimental researches have shown that trajectory and tactical indications at their self-maintained usage do not supply comprehensible detail and reliability of a discernment at problem solving of an estimate of air conditions.
To number of signal tags attribute: the polarization, amplitude, modulation, and also directly radar portraits of the purpose in a radial and tangential direction.
The information on the polarization properties of the purposes is contained in the polarization array of a secondary radiation. Such purposes as airplanes in a centimetric wavelength range can be presented in the form of assemblage is polarization-not selective (a fuselage, suspension canisters) and is polarization-selective units (an edge of a wing, air intakes), superposition of reflexions from which shapes a total reflected signal. Sum signal interpreting in interests of a discernment calls serious difficulties.
Usage of an amplitude indication at known range allows to size up an effective surface of dispersion of the purpose approximately. The given indication supplies with low reliability a discernment only by a principle «large - mean - small». Fluctuations of an effective surface of dispersion of a reflected signal at a fixed frequency of a sounding signal in an essential level depend on an aspect angle of supervision, a flight path of the purpose and effect on it of destabilizing factors (turbulence of an aerosphere, a flight control system error, etc.), presence of exterior suspensions. All it leads to essential difficulties at allotment of unique features in a reflected signal.
The great attention is given recently to the methods of a discernment grounded on the analysis of radar portraits of air targets. At large frequency band of sounding signals with continuous spectrum it is possible to allow units of the purposes along a line-of-sight. If inverse synthesizing of the aperture at the expense of the long-term coherent signal processing is thus implemented, passage to two-dimensional portraits of the purposes which in the course of a discernment are compared to appropriate measurement standards is possible. Essential disadvantages of the given methods are: sensitivity to presence and character of exterior suspensions, and also increased requirements to frequency band of used signals and capabilities of the computer system implementing algorithms of a signal processing.
According to domestic and foreign specialists for a discernment the modulation indications of a secondary radiation arising in the course of cross moving of configuration items of a flight vehicle are rather perspective: blades of propellers, propellers, blades of compressors and turbines etc. the Given indications are informative enough and inconvertible at a discernment not only class-rooms, but also types of air targets. Singularities of secondary modulation of reflected signals are determined by an odds in geometry of spun structure (radius, number and sizes of blades or blades, angles of adjustment and twist of blades, character of a modification of a breadth of the blade on its length, presence or lack of configuration items screening spun structure, etc.), and also rotational speed and an aspect angle of supervision of an air target.
Thus, priority directions of a raise of efficiency of problem solving of a radar discernment in the airborne radar are:
Optimization of the working alphabet of class-rooms;
Sharing of various tags of a discernment;
Registration of the aprioristic information on structure of reflected signals;
Magnification of intervals of the coherent handling of reflected signals;
Design of control algorithms by discernment system operation.