Communications: directive radio wave systems and devices (e.g. – Return signal controls radar system – Antenna control
Patent
1997-05-02
1998-07-21
Sotomayor, John B.
Communications: directive radio wave systems and devices (e.g.,
Return signal controls radar system
Antenna control
342 96, 342 97, 342149, 342154, 342153, 342194, 342195, G01S 1344, G01S 1372
Patent
active
057840229
DESCRIPTION:
BRIEF SUMMARY
The current invention relates to a process according to the preamble to claim 1 or 8.
Today, monopulse radar devices are normally used for the locating and if need be, tracking flying objects; among other places, these radar devices are described in M. Skolnic, Radar-Handbook, McGraw Hill 1970, chapter 21, or E. Brookner (editor), ASPECTS OF MODERN RADAR, Artech House, Inc. 1988, chapter 5 (S. M. Sherman, Monopulse Principles and Techniques). With monopulse radar devices, with each pulse received, angular error signals in azimuth and elevation are generated, which approach zero when the antenna or bore sight axis is aimed precisely at the target. The aligning and if need be, guidance of the bore sight axis is executed mechanically or, in the case of a phased array antenna, electronically. With a phased array antenna, often the measurement range in elevation is electronically scanned and the measurement range in azimuth is mechanically scanned (A. E. Acker, HOW TO SPEAK RADAR, BASIC FUNDAMENTALS AND APPLICATIONS OF RADAR, Varian Associates, Palo Alto 1988, pp. 30 and 31).
Known amplitude or phase monopulse radar devices supply precise angular measurement data with regard to a flying object, provided that in addition to the signals received directly from the flying object monitored, no signals from other objects or signals reflected once or multiply by the first or the other objects are received.
FIG. 1 shows two flying objects TT1 and TT2 in an antenna beam B, of which the first is disposed above the bore sight axis bx and the second is disposed below it. According to E. Brookner, loc. cit., chapter 5, pp. 323-330, with a conventional monopulse radar device, the spatial position of a flying object can no longer be precisely determined as soon as a second flying object is disposed in the same radar beam. In comparison to the single-target case, the phase of the resultant difference signal changes in relation to the composite signal. Moreover, conventional monopulse radar devices supply incorrect angular measurement data if the targets cannot be separated by distance as well. A particular instance of the double-target case is the mirroring of the radar echo from a flying object, reflected on the surface of water, for example.
If for example, an object that is flying over water is tracked using a tracking radar device, usually an elevation angular error signal occurs, which is not zero, even if the bore sight axis is aimed precisely at the flying object. In addition to the echo signal of the flying object monitored, a second target echo signal is received, which is reflected off the surface of the water. Then the resultant signal cannot be resolved with regard to these two signals either in distance or in angle. The overlapping of these two echo signals thus produces incorrect data with regard to the elevation of the target object. As a result, during the guidance phase, the elevation servo circuit guides the bore sight axis in an incorrect direction offset from the target. It is further known that for the simultaneous measurement of n.sub.t different coherent targets in 2 dimensions, theoretically at least m.sub.a =2*n.sub.t different subantennas are required (independent receiving points within an antenna system), which transmit complex signals that have to be processed in exactly calibrated, stable in-phase and quadrature channels. To ascertain target data, ma complex equations are required, which have to be solved for the unknown quantities by the computer of the radar system (see A. I. Leonov, K. I. Formichev, Monopulse Radar, 1986 Artech House, Inc., chapter 5.4.4 (Functional Signal Processing)). Due to the difficulties to be expected, up to this point, these theoretical considerations have not yet been converted into the proposed form in actual practice (see E. Brookner, loc. cit., chapter 5.7, pp. 323 and 324). They form the basis for the embodiment explained below, in which, by means of concerted simplifications, a process was successfully arrived at for measuring two simultaneously occurring targets,
REFERENCES:
patent: 4084160 (1978-04-01), Lenenberger et al.
patent: 4219816 (1980-08-01), Schenkel et al.
M. Skolnic, Radar-Handbook, McGraw Hill, Chapter 21 (1970).
S. Sherman, "Monopulse Principles and Techniques," Aspects of Modern Radar, E. Brookner (ed.), Artech House, Inc., Chapter 5 (1988).
Acker, How to Speak Radar, Basic Fundamentals and Applications of Radar, Varian Assoc., pp. 30-31 (1988).
Leonov et al., Monopulse Radar, Artech House, Inc., chapter S.4.4 ("Functional Signal Processing").
Schenkel, Cross-Feed Monopulse-A Specific Method to Eliminate Mistracking Over Sea, Presented at International Conference "Radar-87", London (Oct. 19-21, 1987).
Sherman, Monopulse Principles and Techniques, Artech House, pp. 73-75 and 339-343 (1984).
Antenna Engineering Handbook, Third Edition, R. Johnson (ed.), McGraw-Hill, Inc., chapter 33, pp. 33-36-33-38 (1993).
Onsy A. Abd El-Alim et al., "Second-Order Discriminant Function for Amplitude Comparison Monopulse Antenna Systems," IEEE Transactions on Instrumentation Measurement, Bd. 40, No. 3, pp. 596-600 (Jun. 1991).
Siemens Switzerland AG
Sotomayor John B.
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