Process and amplitude or phase monopulse radar device for locating flying objects

• US 5,784,022 A
• Filed: 05/02/1997
• Issued: 07/21/1998
• Est. Priority Date: 12/19/1995
• Status: Expired due to Fees

• Current Assignee: Siemens Switzerland AG (Siemens AG)
• Original Assignee: Siemens Switzerland AG (Siemens AG)
• Inventors: Kupfer, Hanspeter
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US08/817,703
• Time in Patent Office: 445 Days
• Field of Search: 342/80, 342/90, 342/95, 342/96, 342/97, 342/148, 342/149, 342/152, 342/153, 342/154, 342/155, 342/157, 342/158, 342/194, 342/195, 342/203
• US Class Current: 342/80
• CPC Class Codes: G01S 13/4418 with means for eliminating radar-dependent errors in angle measurements, e.g. multipath effects
• CPC Class Codes: G01S 13/4445 amplitude comparisons monopulse, i.e. comparing the echo signals received by an antenna arrangement with overlapping squinted beams
• CPC Class Codes: G01S 13/4454 phase comparisons monopulse, i.e. comparing the echo signals received by an interferometric antenna arrangement
• CPC Class Codes: G01S 13/4463 using phased arrays
• CPC Class Codes: G01S 13/726 Multiple target tracking

Abstract

The process and the corresponding phase or amplitude-single pulse radar device are used to locate a first and possibly a second target (TT1, TT2) detected by the radar beam from the direction x1, y1; x2, y2. The extended single-pulse aerial of the radar device has at least three partial aerials for a first measuring axis x (e.g. azimuth) which are arranged in such a way, have such directional characteristics and the signals of which are combined together and weighted in such a way that two mutually linearly independent, purely real or purely imaginary aerial functions which are independent of target displacements perpendicular to the first measuring axis are formed. The function course of these aerial functions F1(x) and F2(x) is measured for the individual case and the functional values dependent upon the target displacement x are stored in the storage unit (MEM). Measurements are found for the targets of the position x1 and x2 detected by the radar beam according to the aerial functions F1 and F2.

Claims

1. A process for an amplitude or phase monopulse radar device for position measurement of a first target (TT1) and if need be, a second target (TT2) detected by the radar beam from the directions x1, y1;

x2, y2, whose echo signals overlap, having a horn or array antenna (HA;

PA), which, for one measurement axis x, has at least three subantennas (A, B, Ω

) that are embodied and disposed in such a way that with their output signals, two linear combinations FO1(x) and FO2(x) can be formed, by means of which, after normalization with a third linear combination Fs(x) of output signals, two antenna functions

space="preserve" listing-type="equation">F1(x)=FO1(x)/Fs(x)=F1p(x)+jF1q(x), with F1p(x) or F1q(x)=0

space="preserve" listing-type="equation">F2(x)=FO2(x)/Fs(x)=F2p(x)+jF2q(x), with F2p(x) or F2q(x)=0

are formed, which are linearly independent of each other, purely real or purely imaginary, and independent of target offset positions perpendicular to the measurement axis, that these antenna functions F1(x) and F2(x) are measured for the single-target case and the function values that are dependent upon the target offset position x are stored, that measurement values

space="preserve" listing-type="equation">F1.sub.ACT =F1p.sub.ACT +F1q.sub.ACT, in the two-target case with F1p.sub.ACT and F1q.sub.ACT ≠

0,

space="preserve" listing-type="equation">F2.sub.ACT =F2p.sub.ACT +F2q.sub.ACT, in the two-target case with F2p.sub.ACT and F2q.sub.ACT ≠

0

are determined according to the antenna functions F1(x) and F2(x) for the targets (TT1, TT2) detected by the radar beam, and the equation given below for the amplitude monopulse process (index A) or the phase monopulse process (index φ

) is solved for the target directions x1 and x2 by using the stored function values;

##EQU39##

2. A process according to claim 1, characterized in that one of the functions F1(x), F2(x) is even and the other is odd and/or that the main radiation directions of the three subantennas (A, B, Ω

) or the extreme values of all illumination functions jO1(lx, lsx), jO2(lx, lsx), js(lx, lsx) are disposed in one plane and/or that the radiated field patterns of the three subantennas (A, B, Ω

) or the illumination functions jO1(lx, lsx), jO2(lx, lsx), js(lx, lsx) have a straight symmetry course with regard to offset positions perpendicular to the measurement axis and/or that the functions f1(x, sx), f2(x, sx), fs(x, sx) have function courses perpendicular to the measurement axis, which differ from one another only by means of a proportionality factor.

3. The process according to claim 1, carried out with a horn antenna or an array antenna (HA;

PA), which has a first group of three subantennas or a first group of three illumination functions JO1(lx), JO2(lx), Js(lx) for the first measurement axis x (e.g. azimuth) and has a second group of three subantennas (Ω

, C, D) or a second group of three illumination functions JO1(ly), JO2(ly), Js(ly) for a second measurement axis y (e.g. elevation), and that preferably, one subantenna (Ω

) or one illumination function js(lx, ly) with js(lx,O)=Js(lx);

js(O, ly)=Js(ly) is common to both groups.

4. The process according to claim 1, characterized in that the target offset positions (x1, x2 or y1, y2) are approximately calculated by the function F2(x) or F2(y) being replaced by F2(O).

5. The process according to claim 1, characterized in that the course of the even illumination functions JO2(x) or JO2(y) provided for the curvature measurement corresponds at least approximately to the course of the function:

##EQU40## and/or that the illumination function JO2(lx) provided for measuring the field curvature corresponds to the second derivation of the illumination function Js(lx) provided for measuring the field intensity, and/or that the established course of the illumination function JO2(x) or JO2(y) is approximated to the course of the function ##EQU41## until the side lobes reach the permissible dimension.

6. The process according to claim 1, characterized in that the ratio of the antenna functions FO2(x)/Fs(x) in the single-target case is at least approximately proportional to the square of the angular offset position and/or is equal to zero on the bore sight axis (no angular offset).

7. The process according to claim 1, characterized in that the control, SLS, or omnidirectional beam function of a corresponding antenna system is used as the antenna function FO2(x).

8. The process according to claim 1, characterized in that the signals F1_ACT, F2_ACT produced in the input steps (AF, NM) of the radar device are divided into in-phase components F1p_ACT, F2p_ACT and quadrature components F1q_ACT, F2q_ACT in another step (QG) and are scanned at the same time.

9. The process in particular according to claim 1, characterized in that the phase difference φ

between signals coming in from two directions is measured and it is determined whether an actual double-target case or a reflection case is detected and/or whether phase positions that are unfavorable for the measurement are detected, in which the angle φ

approaches zero or π and

which can be prevented for example by changing the transmission frequency.

10. The process in particular according to claim 1, characterized in that the ratios L1, L2 of the powers of the signals from two targets from the directions x1, y1 and x2, y2 are determined in proportion to the power of the composite signal, that in the reflection case, the reflection factor is determined in conjunction with the ascertained power ratios L1, L2 and/or that in the event that the quotient L1/L2 produced by means of the power ratios L1, L2 lies sufficiently close to zero or ∞

, the calculation of the target data is carried out for the single-target case and/or that the localized targets are labeled with the associated power ratios L1, L2, which are checked with each measurement interval when tracking a target so that the appropriate target can be distinguished from other targets or interference sources and/or that with target measurement in two dimensions, the power ratios L_A 1, L_A 2 are associated with the target offset positions x1, x2, y1, and y2 and then it is determined which pair of target offset positions x1, y1;

x1, y2 or x2, y1;

x2, y2 belongs to the first target and which belongs to the second target.

11. The process according to claim 1, characterized in that an antenna is used that can be electronically controlled, whose transmission pattern is preferably set in such a way that if possible, no signal is transmitted or received with regard to the direction of an interference signal or a target to be blanked out.

12. The process according to claim 1, characterized in that the signals of the subantennas (A, B, Ω

, or Ω

, C, D) provided for each measurement direction are preferably weighted by the factors R, S, T;

E, G, and H in a weighting network provided in the antenna unit, the weighting being carried out in such a way that an odd inclination function FO1(x);

FO1(y), an even curvature function FO2(x);

FO2(y), and a sum function Fs(x);

Fs(y) is produced for each measurement direction x;

y.

13. The process according to claim 1, characterized in that illumination functions jO1(lx, lsx);

jO1(ly, lsy), jO2(lx, lsx);

jO2(ly, lsy), js(lx, lsx) js(ly, lsy) and/or antenna functions fO1(x, sx);

fO1(y, sy), fO2(x, sx);

fO2(y, sy), fs(x, sx) fs(y, sy) are selected, which can be represented as the product of a component JO1(lx);

JO1(ly), JO2(lx);

JO2(ly), Js(lx) Js(ly) or FO1(x);

FO1(y), FO2(x);

FO2(y), Fs(x) Fs(y) in the measurement direction x, y and a component JO1(lsx);

JO1(lsy), JO2(lsx);

JO2(lsy), Js(lsx) Js(lsy) in the direction of the perpendiculars lsx, lsy to lx, ly and the perpendiculars sx, sy to the measurement direction x, y.

14. The process according to claim 1, characterized in that the determination of target data is carried out based on the amplitude and/or phase monopulse process.

15. The process according to claim 1, characterized in that for the determination of target data in the single-target case, at least one of the equations below is used:

for the amplitude monopulse process, x=F1_A^-1 (F1_A p_ACT) and/or x=F2_A^-1 (F2_A p_ACT)

and for the phase monopulse process, x=F1.sub.φ

^-1 (j*F1.sub.φ

q_ACT) and/or x=F2.sub.φ

^-1 (F2.sub.φ

p_ACT).

16. The process according to claim 1, characterized in that the measurement is preferably carried out using a honeycomb antenna with seven subarrays for three measurement dimensions x, y, and z disposed in one plane, and it is determined which target directions can be correspondingly determined based on measurements in the three measurement directions x, y, and z.

17. A process for a monopulse radar device for position measurement of a first target (TT1) and if need be, a second target (TT2) detected by the radar beam from the directions x1, y1;

x2, y2, whose echo signals overlap, having an antenna whose signals are produced by three illumination functions transformed into antenna functions FO1(x), FO2(x), Fs(x), of which the first JO1(lx) is provided for measuring the field inclination, the second JO2(lx) is provided for measuring the field curvature, and the third Js(lx) is provided for measuring the field intensity, which illumination functions are selected in such a way that after normalization of the antenna functions FO1(x), FO2(x) with the antenna function Fs(x), two antenna functions

space="preserve" listing-type="equation">F1(x)=FO1(x)/Fs(x)=F1p(x)+jF1q(x), with F1p(x) or F1q(x)=0

space="preserve" listing-type="equation">F2(x)=FO2(x)/Fs(x)=F2p(x)+jF2q(x), with F2p(x) or F2q(x)=0

are formed that are linearly independent of each other, purely real or purely imaginary, and independent of target offset positions perpendicular to the measurement axis, that these antenna functions F1(x) and F2(x) are measured for the single-target case and the function values that are dependent upon the target offset position x are stored, that measurement values

space="preserve" listing-type="equation">F1.sub.ACT =F1p.sub.ACT +F1q.sub.ACT, in the two-target case with F1p.sub.ACT and F1q.sub.ACT ≠

0,

space="preserve" listing-type="equation">F2.sub.ACT =F2p.sub.ACT +F2q.sub.ACT, in the two-target case with F2p.sub.ACT and F2q.sub.ACT ≠

0

are determined according to the antenna functions F1(x) and F2(x) for the targets (TT1, TT2) detected by the radar beam, and the equation given below for the amplitude monopulse process (index A) or the phase monopulse process (index φ

) is solved for the target directions x1 and x2 by using the stored function values;

##EQU42##

18. An amplitude or phase monopulse radar device for position measurement of a first target (TT1) and if need be, a second target (TT2) detected by the radar beam from the directions x1, y1;

x2, y2, whose echo signals overlap, having a horn antenna or an array antenna (HA;

PA), which, for a first measurement axis x, has at least three subantennas (A, B, Ω

) that are embodied and disposed in such a way that with their output signals, two linear combinations FO1(x) and FO2(x) can be formed, by means of which, after normalization with a third linear combination Fs(x) of output signals, two antenna functions

space="preserve" listing-type="equation">F1(x)=FO1(x)/Fs(x)=F1p(x)+jF1q(x), with F1p(x) or F1q(x)=0

space="preserve" listing-type="equation">F2(x)=FO2(x)/Fs(x)=F2p(x)+jF2q(x), with F2p(x) or F2q(x)=0

are formed, which are linearly independent of each other, purely real or purely imaginary, and independent of target offset positions perpendicular to the measurement axis, that a memory unit (MEM) is provided in which the function values of the antenna functions F1(x) and F2(x) measured for the single-target case are stored, that measurement values

space="preserve" listing-type="equation">F1.sub.ACT =F1p.sub.ACT +F1q.sub.ACT, in the two-target case with F1p.sub.ACT and F1q.sub.ACT ≠

0,

space="preserve" listing-type="equation">F2.sub.ACT =F2p.sub.ACT +F2q.sub.ACT, in the two-target case with F2p.sub.ACT and F2q.sub.ACT ≠

0,

can be determined for the targets (TT1, TT2) detected by the radar beam, in accordance with antenna functions F1 and F2, and that a processor (PROC) is provided to take the equation given below for the amplitude monopulse process (index A) or the phase monopulse process (index φ

) and solve it for x1 and x2;

##EQU43##

19. The monopulse radar device according to claim 18, characterized in that one of the functions F1(x), F2(x) is even and the other is odd and/or that the main radiation directions of the three antennas (A, B, Ω

) or the extreme values of all illumination functions jO1(lx, lsx), jO2(1x, lsx), js(lx, lsx) are disposed in one plane and/or that the radiated field patterns of the three subantennas (A, B, Ω

) or the illumination functions jO1(lx, lsx), jO2(lx, lsx), js(lx, lsx) have a straight symmetry course with regard to offset positions perpendicular to the measurement axis and/or that the functions f1(x, sx), f2(x, sx), fs(x, sx) have function courses perpendicular to the measurement axis, which differ from one another only by means of a proportionality factor.

20. The monopulse radar device according to claim 18, characterized in that a horn antenna or an array antenna (HA;

PA) is provided, which has a first group of three subantennas or a first group of three illumination functions JO1(lx), JO2(lx), Js(lx) for the first measurement axis x (e.g. azimuth) and has a second group of three subantennas (Ω

, C, D) or a second group of three illumination functions JO1(ly), JO2(ly), Js(ly) for a second measurement axis y (e.g. elevation), and that preferably, a subantenna (Ω

) or an illumination function js(lx, ly) with js(lx,O)=Js(lx);

js(O, ly)=Js(ly) is common to both groups.

21. The monopulse radar device according to claim 18, characterized in that the antenna has a control, SLS, or omnidirectional beam function, which is used as a curvature function FO2(x) or FO2(y).

22. The monopulse radar device according to claim 18, characterized in that the phase difference φ

between signals coming from two directions and/or the ratios L1, L2 of the powers of the signals from two targets from the directions x1, y1 and x2, y2 can be measured and evaluated in proportion to the power of the composite signal.

23. The monopulse radar device according to claim 18, characterized in that the antenna (PA) can be electronically controlled in such a way and its transmission pattern can be set in such a way that if possible, no signal is transmitted or received with regard to the direction of an interference signal or a target to be blanked out.

24. The monopulse radar device according to claim 18, characterized in that a network (AF) and a division step (NM) are provided, which produce the signals F1_ACT, F2_ACT from the output signals of the subantennas (A, B, Ω

or Ω

, C, D), and that are divided into in-phase components F1p_ACT, F2p_ACT and quadrature components F1q_ACT, F2q_ACT in another step (QG).

25. The monopulse radar device according to claim 18, characterized in that for each measurement axis x;

y, the amplitude monopulse antenna has three subantennas (A, B, Ω

or Ω

, C, D), which each have a common phase center and whose radiation axes for each measurement axis are disposed in one plane, or that for each measurement axis x;

y, the phase monopulse antenna has three subantennas (A, B, Ω

or Ω

, C, D), whose phase centers for each measurement axis are disposed on a common line and whose radiation axes run parallel to one another.

26. The monopulse radar device according to claim 18, characterized in that the amplitude monopulse antenna or the phase monopulse antenna is an array antenna with a number of antenna elements (AE), which are provided singly or combined in groups to constitute subantennas (A, B, Ω

or Ω

, C, D).

27. The monopulse radar device according to claim 18, characterized in that the phase centers of the subantennas (A, B, and Ω

or Ω

, C, and D) are disposed in such a way that the phase center of subantenna (Ω

) is enclosed with equal spacing between the phase centers of subantennas (A and B and/or C and D) and/or that the radiation axes of subantennas (A and Ω

or C and Ω

) enclose the same angle as the axes of subantennas (Ω and

B or Ω and

D) and/or that the patterns of subantennas (A and B or C and D) have an at least approximately equal amplitude course and/or that the patterns of subantennas (A and B or C and D) have a straight symmetry to the bore sight axis and that the pattern of subantenna (Ω

) contains the bore sight axis bx of the extended monopulse antenna (HA, PA) as the axis for a straight symmetry.

28. The monopulse radar device according to claim 18 for measuring targets in three angular dimensions, characterized in that the antenna (WA) has the shape of a honeycomb with preferably seven subarrays through whose phase centers pz5, pzΩ

, pz6;

pz3, pzΩ

, pz4, or pz1, pzΩ

, pz2 three measurement axes x, y, z run, which intersect in the phase center pzΩ

of the central subarray.

29. The monopulse radar device according to claim 18, characterized in that a processor (PROC) is provided, which operates in accordance with the pipeline process and/or which approximates the stored functions F1, F2 in a first step by means of polynomials of the third order and analytically solves the equations and/or which uses the solutions arrived at in this manner, preferably as the first approximation for an iterative process.

30. An amplitude or phase monopulse radar device for position measurement of a first target (TT1) and if need be, a second target (TT2) detected by the radar beam from the directions x1, y1;

x2, y2, whose echo signals overlap, having an antenna whose signals are produced by three illumination functions transformed into antenna functions FO1(x), FO2(x), Fs(x), of which the first JO1(lx) is provided for measuring the field inclination, the second JO2(lx) is provided for measuring the field curvature, and the third Js(lx) is provided for measuring the field intensity, that after normalization of the antenna functions FO1(x), FO2(x) with the antenna function Fs(x), two antenna functions are formed that are linearly independent of each other, purely real or purely imaginary and independent of target offset positions perpendicular to the measurement axis

space="preserve" listing-type="equation">F1(x)=FO1(x)/Fs(x)=F1p(x)+jF1q(x), with F1p(x) or F1q(x)=0,

space="preserve" listing-type="equation">F2(x)=FO2(x)/Fs(x)=F2p(x)+jF2q(x), with F2p(x) or F2q(x)=0

are formed that are linearly independent of each other, purely real or purely imaginary and independent of target offset positions perpendicular to the measurement axis, that a memory unit (MEM) is provided in which the function values of the antenna functions F1(x) and F2(x) measured for the single-target case are stored, that measurement values

space="preserve" listing-type="equation">F1.sub.ACT =F1p.sub.ACT +F1q.sub.ACT, in the two-target case with F1p.sub.ACT and F1q.sub.ACT ≠

0,

space="preserve" listing-type="equation">F2.sub.ACT =F2p.sub.ACT +F2q.sub.ACT, in the two-target case with F2p.sub.ACT and F2q.sub.ACT ≠

0,

can be determined according to the antenna functions F1(x) and F2(x) for the targets (TT1, TT2) detected by the radar beam, and that a processor (PROC) is provided for taking the equation given below for the amplitude monopulse process (index A) or the phase monopulse process (index φ

) and solving for the target directions x1 and x2 by using the stored function values;

##EQU44##

31. The monopulse radar device according to claim 30, characterized in that the course of the even illumination functions JO2(x) or JO2(y) provided for the curvature measurement corresponds at least approximately to the course of the function:

##EQU45## and/or that the illumination function JO2(lx) provided for measuring the field curvature corresponds to the second derivation of the illumination function Js(lx) provided for measuring the field intensity, and/or that the established course of the illumination function JO2(x) or JO2(y) is approximated to the course of the function ##EQU46## taking into account the side lobes permissible.