JPS6246277A - Negative range finding method of aerial emitter by single non-steering of fixing sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the measurement of the distance of a moving target, and more particularly to the passive measurement of the distance of a moving target from a single test platform 7 ohms that is either fixed or moving at a constant speed along a straight trajectory. Regarding the method.

Various passive ranging devices and methods have been developed in the past. In passive ranging systems, the position of a target, such as an aircraft or ship, is typically determined by a radiated signal emitted from the target itself, rather than an acoustic signal generated by radiated energy transmitted toward the target, as in active ranging systems. is measured. Generally, these conventional devices and methods employ a variety of optical, electromagnetic, and acoustic sensors along with the use of cooperative ground-based transmitting and receiving stations. Many such devices require multiple cooperative sensor units and cross-correlation equipment. Such equipment is generally complex and has operational limitations, such as the ability to detect only continuous radiation signals, or the ineffectiveness of M-effects on targets moving at a speed faster than the observation vehicle's own speed. Often includes abilities, etc.

Many of the problems with conventional passive ranging devices and methods include:
1979 by the inventor Martin Bolinski
U.S. Patent No. 1,179,6, issued December 18,
No. 97 ('697 Patent) and U.S. Patent Application No. 'a 24.827 ('827 Application), filed November 25, 1981, also in the name of the inventor. be done. '697 Patent and '8
Both applications disclose passive ranging methods in which the distance to an emitter target is measured from a single moving vehicle, commonly referred to as a test platform.

'697#! In the method disclosed in F, a single measurement aircraft is flown at constant speed on a curved trajectory while simultaneously making a series of passive orientations of the target aircraft with respect to itself. A geometric pattern of intersecting rays is produced which provides data for mathematical calculations useful in determining the distance of the target.

The method disclosed in the '827 application uses a single measuring aircraft that is moved along a straight trajectory at variable speeds (i.e., accelerating and decelerating) while simultaneously making a series of negative azimuth measurements of the target aircraft relative to itself. is forced to fly along the This, too, upon measurement, yields a shape pattern of difference rays which provides data for a mathematical answer to the distance of the target.

While both these methods are valid and useful for some applications, there are other applications where it is desirable to passively measure the distance of a target without a test platform that must meet the movement constraints imposed by these conventional methods. There is an example. For example, for an aircraft traveling in a normal manner, i.e., along a straight trajectory at constant speed, it may be possible to easily measure distances to other aircraft without deviating from its designated course or changing its normal airspeed. desirable. Similarly, the ability to measure distance to other aircraft is desirable for fixed test platforms, such as air traffic control towers and hovering helicopters, which cannot meet the movement constraints of conventional methods.

A ranging method that utilizes a series of directional and frequency measurements taken at different times from the radiant energy emitted by the target vehicle overcomes this problem and provides other benefits. According to the invention, only a single measurement carrier or test platform is required to carry out the distance measurement. The test platform is equipped with a radiation cell emitted by the target vehicle. This emitted radiation may be pulsed or continuous.

A sensor containing array beamforming circuitry provides azimuth and frequency information about the radiation source used to measure range to the target aircraft. Also from this information the speed and direction of movement of the emitter is calculated.

The method of the invention provides linear movement of the radiant energy sensor at a constant speed. At other times during its travel, an electrical circuit connected to the sensor collects the radiant energy signal sent by the emitter target. The combined movement of the target and sensor creates a geometric pattern of the received radiation. The azimuthal angle and frequency of these radiations are measured and then mathematically combined to yield the distance to the target vehicle relative to the sensor.

Here, although the present invention describes aircraft tracking,
The method is equally applicable to ships employing acoustic sensors and satellites employing optical sensors. Also, certain assumptions set forth in the aforementioned Bolinski patents and applications are valid herein. In particular, it is assumed that the target whose distance is to be measured is not maneuvered and that the test aircraft is at a long distance from the target and therefore in the same horizontal plane.

The present invention will be explained below with reference to the drawings.

FIG. 1 shows a typical proposal encompassing the method of the invention.

A moving target 20, an aircraft emitting electromagnetic radiation, is shown moving along a flight path 22 in the drawing. Here, it is assumed that the flight path 22 is a straight line and the speed of the target object is constant. Test platform 24U, which is also an aircraft,
Sensor 2 for electromagnetic radiation emitted by a target object 20
It is equipped with 6. The test platform, shown moving along a straight path 28, is constrained to operate at a constant speed.

FIG. 2 illustrates the apparatus used in carrying out the invention and shows how the apparatus is connected.

When a target, such as an aircraft 20, emits an energetic signal, such as a radar pulse, the test aircraft 24 receives the signal via an antenna 30 and is then directed to a passive detection system 32 that measures the bearing and acceptance frequency of the emitted signal. . This type of system is available from manufacturers such as the Amecom Division of Kifton Interseries. Lit/・Model 1f6ALR-
73 is an example of such a passive detection system.

Test platform 24 also includes a navigation system 34;
Includes a tracking system 36 and a display 38. Navigation system 34 and tracking/stem 36 employ well-known circuitry and are available from manufacturers such as Litton Industries.

Examples of these systems include the stem AS
N-92 and Lytton's tracking computer 0L-77/A
Including SQ. The tracking system is capable of performing the mathematical calculation steps necessary to carry out the method of the invention as described below. In the preferred embodiment of the invention, this system is used, but dedicated systems can also be used.Thus, if the calculations are made by the tracking system, the invention only requires systems that are already on board a number of test aircraft. It is clear that there are advantages over systems that require bulky and expensive equipment.

FIG. 3 illustrates the basic concept of the invention. The illustrated vector ACd indicates the trajectory of the test platform 24, and the vector DF indicates the trajectory of the target object 20. The test platform moves at a constant speed as vector ACKI+9, each time T.
, , T, and T3 intersect at points A%B and C. Similarly, target object 20 is assumed to be moving along vector DF at a constant speed and intersect at points D, E, and F at times TI%T and Ts, respectively.

In the diagram shown in Figure 3, T, and T1, T2 and T1
The time intervals between them are equal. Therefore, the distances AB and EC traveled by the test platform during these time periods are equal, and the distances DB and EF traveled by the target during the same time periods are also equal. The assumption of equal time intervals and therefore equal distances is made solely for the convenience of the detailed description of the invention. However, in reality, the times between T and T7 and T2 and 18 need not be approximately equal, nor do the distances traveled by the platform and target during this period need to be equal.

Referring to FIG. 3 in conjunction with FIG. 2, sensors 26 of test platform 24 indicate that the test platform is at point A.
A radiation signal emitted by the target object 20 when it crosses points 1B and 1C is collected. At each of these points, a passive detection system 32 on the platform utilizes the samples to determine the bearing relative to the target aircraft and the frequency of the emitted signal upon arrival at the platform. Once these samples are obtained and their bearings and frequencies determined, tracking system 36 uses this data to mathematically calculate the distance to target 20, as described below.

In contrast to the passive ranging method described in the above-mentioned Bolinski patent/application, which requires six (6) measurements at four points along the trajectory of the test platform, the method of the present invention requires six points along the trajectory of the test platform. However, since the present invention requires frequency measurements in addition to the directional measurements used in the previous method, it is possible to measure the distance of the target in contrast to the previous method. A total of six 5T viewing objects are used.

For a detailed explanation of the invention, the times TI sTt and T.

θ as the direction and frequency measurements for
8, fI; θ! , ft and θ3,f. Generally, the values of the three measured azimuth angles are different due to the shape of the flight path between the test platform and the target object. Similarly, the measurement frequency also changes because the Doppler shift changes even though the frequency that the target transmits is constant.

At point A, the measurement frequency LVi is defined as follows.

m=fo+'d CVtcosr+FF 8%nθ,]
(1) Here, fo is equal due to the transmission wave of the emitter (currently unknown),
λ is equal to the transmission wavelength, τ is the direction line to the emitter, AD and the target velocity vector OF
is equal to the angle between, θ1 is equal to the measurement bearing, V is equal to the platform velocity (which is known by the onboard navigation system 34), and V is equal to the target aircraft velocity (currently unknown).

The right side of equation (1) is the transmission frequency f. On the other hand, it shows a totsbar shift. A similar equation can be expanded to define the frequency f, 13. Therefore, test platform 2
4 at points B and C, the measured frequencies f and f, respectively, are given by the following equations.

fx =fo +'A (Vtcos (τ1011.
Soup S', sinθ2) (2) Mu = fo +'/
2 CV(cos(r+θ1.s)+Vp ssnθ
3) (3) Here, θ is equal to the measurement direction at point B, and θS is equal to the measurement direction at point C.
equal to the measurement direction at θ1. is equal to θ1−θ, θ0. is equal to θ1−θ.

Other parameters are defined above. All angles are measured counterclockwise and positive. Therefore, in FIG. 3, θ has a negative value.

Equation (1)@3) has three unknowns τ, yt, and fo. Therefore, these equations are solved for these unknowns, yielding:

sin θ2 sin θ, s ten sin DH sin θ, 3) where θ21. -02-〇8, C is equal to the propagation speed of electromagnetic waves.

Since fo is calculated by equation (4), each variable on the right side of equation (5) is known, so the value of τ can be easily solved.

Note that by preserving the sign of the numerator and denominator of the argument, the usual angular ambiguity associated with arc tangents is resolved.

The last unknown quantity vl is determined by the following equation.

Calculate the values of the unknowns y and τ, and calculate the interval T(ko!') between measurements.
(equal to the time interval between L1, T, and T7, and T, and T1)
Knowing that, the target aircraft 2 from the test platform 24
0 (unknown distance at 7, i.e. AD, B shown in Figure 3)
E and CF can be solved. Therefore, DH:=EF=V,T [7
1 On the other hand, AB=sc=VpT (81) The distance to the target 20 at point A is AD expressed by the following formula.
It is.

AD=AG0GD-(AEcosθ1+DEsin(r
10r, x)] sin θ1,2 Here, all the values on the right side of equation (11) are known. Similarly, the distances to the target 20 at points B and C are BE and CF, respectively, as shown in the following equations.

BE=EG+GE=-=--[AE cosθ, +DE
sinτ] (2) 8Znθ1,2 CF=CJ+JF=-CAB cosθ, -4-DB
Sin τ) Q3) sin θ1. It Therefore, solving Equation 11.12.13, if the test platform is traversing a straight course at constant speed, the distances at Renhui sample points A, B, and C from the test platform to the $6 emitter are can get. Once this range information is calculated, the platform's standard mounting system can be used to measure the speed and direction of movement of the emitter target.

FIG. 1 shows the basic concept of the invention in the case where the test plan form is fixed. Applications of this type include air traffic control towers, hovering helicopters or towing vessels. Here, since the velocity of the test platform is zero, V, is set to zero in equation 1.2.3. In this case, the method of measuring the distance to the emitter target at point DSE,F is still the same. So A.D.
, BE, CF indicate the distance from the common point A to the moving emitter, since points B and C are co-located with point A.

To improve the accuracy of the calculated distance in the presence of measurement errors, the measurement made at time T1, T, is used together with the first measurement to update the distance calculation. This modern method can be continued for an extended period of time if desired.

The invention has many military uses. However, in addition to such military applications, the present invention can also be used for commercial applications, such as air traffic control. In such applications, the transmission frequency 10 is known. Thus, only two sample points, eg A and B, are required rather than three, reducing the time required to measure the coverage distance to the target emitter.

If each measurement string is defined by a passive detection system generated by a distinct emitter, the calculations used to implement the invention can be performed essentially in real time for three different measurement strings. Therefore, the number of emitters that can be positioned by the present technique is limited only by the number of distributed tracking files in the tracking system.

It should be understood that many modifications may be made to the present invention without departing from its spirit and scope. The terms and expressions used herein are for purposes of illustration and not limitation, and are not intended to exclude equivalents of the invention described and claimed herein.

[Brief explanation of drawings]

FIG. 1 shows a mobile vehicle, shown as a test aircraft, supporting a sensor for receiving radiant energy signals emitted by the target vehicle, and shown as a removed aircraft. FIG. 2 is a block diagram of a passive ranging system used in the passive ranging method of the present invention. FIG. 3 is a geometric diagram showing the relationship between the target aircraft and the mobile test aircraft at the attitude detection point. FIG. 1 is a geometric diagram showing the relationship between a target aircraft and a fixed test platform at a single detection point. 20...Target, 22...Flight path, 24...Test plan form, 26...Sensor, 28...Straight path,
30... Antenna, 32... Passive detection system, 3
4... Navigation system, 36... Tracking system, 38
···display. % Ganto Noyama Geraman Aerospace Corporation, ′,,+゛,. Substitute Patent Attorney Takehiko Saito 115. ．． ．． ．．
．． ．． ．． ．． ．． I>6FIG, 1 FIG, 3 Procedural amendment (method) % formula % 1 Display of case 1985 Patent Application No. 18436 Signal 2, Title of invention 3, Person making the amendment Relationship with the case Patent applicant name Clamant Aero space corporation 4,
Agent name: Patent attorney (7175) Takehiko Saito,
, -ゝ'~-7 5. Contents of the 6th amendment to the handwritten specification attached to the application subject to amendment As shown in the attached sheet, however, there is no amendment to the content.

Claims (1)

[Claims] 1. In a method of passively measuring the distance from a test platform to a target, the test platform moves at a constant speed along a straight course; detecting the presence and sampling of said energy signal at three separate times; for each sample of said energy signal sample, a first detection signal responsive to an angle of arrival at the platform; and a first detection signal responsive to a frequency upon arrival at the platform; a second detection signal representing the target; storing the detection signal; and measuring a distance to the target using the stored detection signal, the platform velocity and position; and a target indication signal representative of the distance of the target. A method characterized by: 2. The step of measuring the distance to the target includes calculating the transmission frequency of the energy signal; using the transmission frequency to determine the direction to the target and the course of the target at the first time of the separate sample time. calculating an angle between; calculating the speed of the target using the calculated angle; and measuring the distance to the target using the calculated angle and the target speed. The method described in Scope No. 1. 3. A method according to claim 1 or 2, wherein the test platform is fixed such that its speed is equal to zero. 4. A method according to any one of claims 1 to 3, wherein the transmission frequency of the energy signal is known, so that the energy signal is sampled only at two separate times. 5. The method of claim 1 or 2, wherein the test platform and the target are at essentially the same altitude and are both flying horizontally. 6. The method according to any one of claims 1 to 5, wherein the step of acquiring the energy signal comprises receiving a continuously occurring energy signal. 7. The method according to any one of claims 1 to 5, wherein the step of collecting the energy signal is receiving a pulsed energy signal. 8. The method according to any one of claims 1 to 5, wherein the step of collecting the energy signal is receiving a continuously occurring radar signal. 9. The method according to any one of claims 1 to 5, wherein the step of collecting the energy signal is receiving a pulsed radar signal. 10. The method of claim 6, wherein the step of acquiring the continuously occurring energy signal is acquiring a signal class consisting of optical frequency signals and acoustic signals. 11. The step of collecting the energy signal includes receiving a pulse energy signal of an energy signal class;
A method according to claim 7. 12. The test platform is a test aircraft, which crosses the straight path of the test aircraft at a constant speed; the test aircraft collects the radio signals emitted by the target at three different times; for each sample, the test generating the first detection signal responsive to an angle of arrival at the aircraft and the second detection signal responsive to a frequency of arrival at the test aircraft; the first and second detection signals and the test aircraft speed; measuring the distance to an airborne target using the; generating said target indicating signal representative of the distance to the target;
A method according to any one of claims 1 to 11.