CA1338629C - System for determining the angular spin position of an object spinning about an axis - Google Patents
System for determining the angular spin position of an object spinning about an axisInfo
- Publication number
- CA1338629C CA1338629C CA000598540A CA598540A CA1338629C CA 1338629 C CA1338629 C CA 1338629C CA 000598540 A CA000598540 A CA 000598540A CA 598540 A CA598540 A CA 598540A CA 1338629 C CA1338629 C CA 1338629C
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- Prior art keywords
- carrier wave
- antenna
- projectile
- unit
- antennas
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F41—WEAPONS
- F41G—WEAPON SIGHTS; AIMING
- F41G7/00—Direction control systems for self-propelled missiles
- F41G7/20—Direction control systems for self-propelled missiles based on continuous observation of target position
- F41G7/30—Command link guidance systems
- F41G7/301—Details
- F41G7/305—Details for spin-stabilized missiles
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- General Engineering & Computer Science (AREA)
- Radar Systems Or Details Thereof (AREA)
- Variable-Direction Aerials And Aerial Arrays (AREA)
- Aiming, Guidance, Guns With A Light Source, Armor, Camouflage, And Targets (AREA)
Abstract
A system for determining the angular spin position of a second object (1) spinning about an axis. A first object (7) emits electromagnetic waves. The second object (1) is provided with directional receiving antenna means (10) and with a receiving system (13) which, using the receiving antenna means (10), process in combination the carrier waves received to obtain said angular spin position. The received signals comprise at least one polarised first carrier wave and a second carrier wave which comprises phase information of the first carrier wave.
Description
System for dete_ inin~ the angular spin position of an object spinning about an axis.
The invention relates to a system for dete ining the angular spin position of a second object spinning about an axis, where a first object emits elec~L. aP~etic waves and where the system is provided with directional receiving antenna means fitted to the second object, and with a receiving system which, using the receiving antenna means, process in combination the carrier waves received to obtain said angular spin position.
Such an arrangement is known from EP-A 0,239,156. This patent particularly applies to a second object in the shape of a projectile. In case of fired projectiles, such as shells, it is often desirable to change the course during the flight. However, since a shell spins about its axis along the tra;ectory, correction of its course is effective only if at any random instant the associated spin or roll position ~m(t) is well-known. Suitable course correction means for this purpose are preferably based on principles of the aerodynamics, the chemistry, the gas theory and the dynamics. In this respect, considered are the bringing out of damping fins or surfaces on the projectile's circumferential surface, the detonation of small charges on the projectile, and the ejection of a small mass of gas from the projectile.
According to the EP pstent specification this problem is solved by transmitting signals consisting of at least two superimposed phase-locked and polarised carrier waves having different frequencies. These signals are transmitted by the first object.
Thus it is possible to obtain a reference signal by processing both carrier waves in combination. This reference signal comprises phase information of both carrier waves. By means of this reference signal, the 180 uncertainty can be eliminated. It is clear from Fig. 1 of the EP patent that also a third carrier wave is present for transmitting data to the projectile by means of the transmitter.
After this, for instance, the information on angle ~g is transmitted upon which a correction is to be carried out by the pro~ectile.
For this purpose, the projectile itself dete_ ~neS the instantaneous angular spin position ~m(t) and carries out a correction as soon as ~g ~ ~m(t) The present invention has for its object to simplify and ~ ~Lvve the above system and is characterised in that the received signals comprise at least one first polarised carrier wave and a second carrier wave, which comprises phase information of the first carrier wave.
Contrary to the EP patent, according to the present invention, the information for obtaining the reference signal is carried fully by the second carrier wave. As a result, the receiving system of the second object (the projectile) may be of a much simpler and thus more cost-effective construction. Another advantage is that the reference signal may be dete ~ned more accurately. Noreover, the second carrier wave can be used to transmit other information (such as ~g), resulting in a further cost reduction because there will be no need for a third carrier wave.
According to a special embodiment of the invention, it is even feasible to use the fins of a projectile as an antenna system. By means of these fins, the first as well as the second carrier wave can be received. This results in a further cost reduction, while ~ ".~ving the robustness of the system.
According to another advantageous embodiment of the invention, the orientation of the first object is lln~ ,_L~ant in the determination of the angular spin position of the second object with respect to, for instance, the earth surface. This is not possible in conventional systems as the angular spin position of the second object is determined with the first object as reference. In conventional systems this implies that the orientation of the second object with respect to the earth surface must be known and be kept constant. If the first object is, for instance, a ship, a transmitter and antenna unit of the first object, transmitting the at least one polarised carrier wave, will have to be fitted on a stabilised platform. Only then it is possible in conventional systems to keep the polarisation direction of the transmitted carrier waves with respect to space (the earth surface) constant.
The use of a stabilised platform however is rather expensive.
Moreover, the means must be available to measure and process the position and orientation of the platform in order to obtain an angular spin position of the second object with respect to space.
This renders the system inaccurate as well as more expensive.
In conventional systems, a polarised carrier wave around the second object is obtained by transmitting a polarised carrier wave. This has the disadvantage that a polarising transmitter and antenna unit needs to be used. Such transmitter and antenna units have the disadvantage that they are rather bulky and thus quite expensive.
According to an especially cost-effective embodiment of the inventionr however, a transmitter and antenna unit is used which transmits carrier waves re~ch~ng up to and around the second object but also up to and interfering with the earth surface. Moreover, the transmitter and antenna unit of the first object is thus arranged that the frequency of the first carrier wave to be transmitted is ` 1 338629 relatively low, i.e. around 50 kHz. These technical measures result in a carrier wave of which the electric field component is vertically disposed with respect to the earth surface. The latter is entirely independent of the orientation of the transmitter and antenna unit. Similarly, the magnetic field component of the first carrier wave is horizontally disposed with respect to the earth surface. This results in the enormous advantage of being able to measure the rotation of the angular spin position of the second object with respect to the earth surface. Moreover, there is no need to fit the transmitter and antenna unit, when used on a ship, on to a stabilised platform.
The above also results in much simpler and cheaper embodiment of the transmitter and antenna unit, because said system needs not be suitable for the generation of polarised carrier waves with an accurately defined polarisation direction.
Moreover, determination and calculation of the angular spin position are also simpler and cheaper as the orientation of the first object is of no importance.
The invention will now be described in more detail with reference to the accompanying drawings, of which:
Fig. la is a schematic representation of a first embodiment of a complete system for the control of a projectile functioning as the second object, taking into account an apparatus according to the invention;
Fig. lb is a schematic representation of a projectile controlled by the system of Fig. la;
Fig. 2 represents a special embodiment of the system where . , , ~
` -- ~
the system is arranged in such a way that the orientation and position of the antenna unit of the system may remain undetermined.
Fig. 3 is a schematic representation of two perpendicularly disposed loop antennas placed in an electromagnetic field;
Fig. 4 is a schematic representation of two perpendicularly disposed dipole antennas placed in an electromagnetic field;
Fig. 5 is a diagram of a magnetic field at the location of the loop antennas;
Fig. 6 shows a schematic representation of the receiving system included in a projectile to determine the angular spin position of the projectile;
Fig. 7 is a first embodiment of a unit from Fig. 6;
Fig. 8 is a second embodiment of a unit from Fig. 6;
Fig. 9 is a diagram of an electric field at the location of the dipole antennas;
Fig. 10 is an embodiment of the projectile with dipole antennas;
Fig. lla is a schematic representation of a second embodiment of a complete system for the control of a projectile functioning as the first object, taking into account an apparatus according to the invention; and Fig. llb is a schematic representation of a projectile controlled by the system of Fig. lla.
In Fig. 1 it is assumed that a projectile 1 functioning as second object has been fired to hit a target 2. The target trajectory is tracked from the ground with the aid of target ,- ~ 5 tracking means 3. For this purpose, use may be made of a monopulse radar tracking unit operable in the K-band or of pulsed laser tracking means operable in the far infrared region. The trajectory of projectile 1 is tracked with comparable target tracking means 4. From the information of supplied target positions determined by target tracking means 3 and from supplied projectile positions determined by target tracking means 4, computing means 5 determines whether any course corrections of the projectile are necessary. To make a course correction, the projectile is provided with gas discharge units 6. Since the projectile rotates about its axis, a course correction requires the activation of a gas discharge unit at the instant the projectile assumes the correct position. To determine the correct position, carrier waves sent out by a transmitter and antenna unit 7 functioning as first object are utilised. Computing means 5 determines the desired projectile angular spin position ~g at which a gas discharge should occur with respect to the electromagnetic field pattern of the carrier waves at the projectile position.
5a ., The position and attitude of the transmitter and antenna unit 7 serve as reference for this purpose. This is possible, because the field pattern and the pro~ectile position in this field are known.
Accorting to a special embodiment of the invention, use of the position and orientation of the transmitter and antenna unit 7 as a reference is obviated. This is especially advantageous when the orientation of transmitter and antenna unit 7 is sub~ect to v~- ^nt, for instance, when it is placed on a ship (see Fig. 2). Antenna unit 7 of Fig. 2 is arranged in such a way that the transmitted carrier wave reaches up to and around the projectile and that the carrier wave reaches down to the earth surface. Moreover, the frequency of the transmitted carrier wave is relatively low with respect to conventional systems. The result of the above is that the electric field component E of the carrier wave is vertically polarised and that the magnetic field component is horizontally polarised with respect to the earth surface. The polarisation reaches greater heights as the frequency ~O becomes lower and as the antenna unit is placed closer to the earth surface.
As a result of these technical measures, the earth surface behaves as a flat conducting metal plate. The advantage is that the polarisation is independent of the orientation of antenna unit 7.
Angles ~m(t) and ~g(t) can then be determined with the earth surface as a reference.
Antenna unit 7 is of an especially simple and cost-effective type, viz. a single wire. No use is made, as for conventional systems, of a stabilised platform onto which the antenna unit is fitted. Antenna unit 7 will therefore continuously change orientation as a result of the roll of the ship. Antenna unit 7 is also not suitable for transmitting polarised carrier waves, having as an advantage that the length of the antenna unit 7 can be limited. In this case, antenna unit 7 concerns a communication antenna already present on the ship.
1 33~`~2~
The calculated value ~g is transmitted by means of transmitter 8.
For this purpose, transmitter 8 may be provided with its own antenna, as shown in Fig. 1, but may also use the c- ~cation antenna of the transmitter and antenna unit as shown in Fig. 2.
A receiver g, accommodated in the pro~ectile, receives from receiving antenna means 10 the value of ~g transmitted by transmitter 8. The received value ~g is supplied to a comparator 12 via line 11.
A receiving system 13, fed with the antenna signals of two perpendi-cularly disposed directional antennas contained in receiving antennameans 10, dete ~neS the instan~neo~s pro~ectile position ~m(t) with respect to the elecLL~ a~etic field at the location of the directional loop antennas. The instantaneous value ~m(t) is supplied to comparator 12 via line 14. When the condition ~m(t)- ~g has been fulfilled, comparator 12 delivers a signal S to activate the gas tischarge unit 6. At this moment a course correction is made.
Thereafter this entire process can be repeated if a second course correction is required.
It should be noted that it is also possible to make the desired course corrections without the use of second target tracking means 4.
The target tracking means 3 thereto measures the target tra~ectory.
From the measuring data of the target tra~ectory the computing means 5 makes a prediction of the rest of the target tra~ectory.
Computing means 5 uses this predicted data to calculate the direction in which the pro~ectile must be fired. The pro~ectile tra~ectory is calculated by computing means 5 from the pro~ectile ballistic data.
The target tracking means 3 keeps tracking the target 2. If it is found that target 2 suddenly deviates from its predicted tra~ectory, computing means 5 calculates the pro~ectile course correction to be made. It is thereby assumed that the pro~ectile follows its calculated tra~ectory. If the pro~ectile in flight nears the target, this target will also get in the beam of the target tracking means 3.
From this moment onward it is possible to track both the target and the projectile trajectories, permitting computing means 5 to make some pro~ectile course corrections, if necessary. As a result, any deviations from the calculated projectile tra~ectory, for example due to wind, are corrected at the same time.
It is also possible to eliminate the second tracking means 4 with the application of a time-sharing system. In such a case, the target and the pro~ectile tra~ectories are tracked alternately by means of target tracking means 3. Any course corrections of the pro~ectile are made analogously, as described hereinbefore.
Fig. 3 and Fig. 4 show the two perpendicularly disposed directional antennas 15 and 16, forming part of the receiving antenna means 10.
The antennas may comprise a B field or an E field. If two B fielt antennas are applied (such as represented in Fig. 3), the magnetic field c o~e~ts B of an elec~l. apnetic field are detected.
If two E field antennas are applied (such as represented in Fig. 4), the electric field c _.onents E of an elec~,- Q~netic field are detected. If one B field and one E field antenna are used, one subc ,_ ^nt of field component E and one subc. .onent of field c ,~onPnt B are detected. Because field cs ,~.^nts E and B are connected to eachother via the so-called relation of Maxwell, measuLe --t of at least one of the components E or B, or of one s~bc~ , ^nt of the E c _, ent and one subcomponent of the B
will suffice.
For measuring the B component, a loop antenna can be used, while a dipole antenna may be used for measuring the E component.
An x,y,z coordinate system is coupled to one of the loop antennas.
The propagation direction v of the projectile is parallel to the z-axis. The magnetic field c ,~.^nt B, transmitted by transmitter 8 has the magnitude and direction B(rO) at the location of the loop antennas. Here rO is the vector with the transmitter ant the antenna unit 7 as origin and the origin of the x,y,z coordinate system as end point. The magnetic field c ,~.^nt B(rO) can be resolved into a component B(rO)// (parallel to the z-axis) and the component B(rO)l (perpendicular to the z-axis). Only the components B(rO)l can generate an induction voltage in the two loop antennas. Therefore, as reference for the determination of ~m(t) use is made of B(rO)l. In this case, ~m(t) is the angle between the x-axis and B(rO)l, see Fig. 5. Since the computing means is capable of calculating v from the supplied pro~ectile positions r, computing means 5 can also calculate B(rO)l from B(rO) and define ~g with respect to this c ~o~^nt.
Fig. 6 is a schematic representation of the receiving system 13.
In the embodiment of system 13 in Fig. 6 it is assumed that the transmitter sends out an elecL~ .^etic field consisting of a polarised carrier wave with frequency ~O. The magnetic field cc ,_ ^nt Bl(rO) can be defined as ~
Bl(rO) ~ (a sin ~Ot)e, where _ _ ~ e (1) The magnetic flux ~15 through the loop antenna 15 can be defined as:
~15 = (a sin ~ot).S.cos ~m(t) (2) In this formula, S is equal to the area of the loop antenna 15.
The magnetic flux ~16 through loop antenna 16 can be tefined as:
~16 ~ (a sin ~Ot).S.sin ~m(t) (3) The induction voltage in loop antenna 15 is now equal to:
indl5 -e dt ~ -e(a wO cos ~ot).S.cos ~ (t) +
d~m + -e(a sin ~Ot).S.sin ~m(t)- dt (4) Here ~ is a constant which is dependent upon the used loop antennas d~
15, 16. Since the projectile speed of rotation dt is much smaller than the angular frequency ~O, it can be approximated that:
indl5 -~(a ~O cos ~Ot)~o(t).s.cos ~ (t) -e (A cos ~ot).cos ~m(t) (5) Similarly, for loop antenna 16:
Vind ~ (A cos ~ot).sin ~m( ) (6) Transmitter 8 also transmits an elecLL. ag~etic wave E where:
E(t) ~ G(t) cos ~lt with G(t) - D.(l - ~ wot).
In this formula, D is a constant and ~ the modulation depth, so < ~ < 1. Also, ~1 ~0- According to this embodiment, frequency ~1 is FM- -d~ ted to comprise the information concerning ~g.
The elec~,. a~etic wave is therefore modulated with cos ~ot and thus comprises phase information of the signal transmitted by antenna unit 7. Receiving antenna means lO is provided with an antenna 17 for the reception of signal E(t). Antenna 17 is linked with a reference unit 18, which generates a reference signal Uref from the received signal E(t), with U - C cos ~ t . (7) ref o Here C is a constant which is dependent upon the specific embodiment of reference unit 18. The Uref signal is supplied to mixers 20 and 21 via line 19.
Signal Vind (t) is also applied to mixer 20 via line 22.
The output signal of mixer 20 is applied to low-pass filter 24 via line 23. The output signal U24(t) of the low-pass filter 24 (the t~
c~ Eone~t of frequency dt ) is equal to:
U (t) = AC cos ~ (t) (8) In a fully analogous way, signal Vind (t) is fed to mixer 21 via line 25. The output signal of mixer 21 is fed to a low-pass filter 27 via line 26. Output signal U27(t) of the low-pass filter 27 is equal to:
U27(t) e 2 sin ~m(t) (9) From formula (8) and (9) and for a given U24(t) and U27(t), it is simple to determine ~m(t)~ To this effect, signals U24(t) and U27(t) are sent to a trigonometric unit 30 via lines 28 and 29. In response to these signals, trigonometric unit 30 generates ~m(t)~
Trigonometric unit 30 may, for instance, function as a table look-up unit. It is also possible to have the trigonometric unit functioning as a computer to generate ~m(t) via a certain algorithm.
Fig. 7 represents an embodiment of reference unit 18. Antenna signal E(t) is supplied to a b~ndpass filter 32 via line 31. B~ndpflss filter 32 only passes signals with a frequency of arount ~1 Signal B(t) will therefore not be passed. Signal E(t) is subsequently supplied to an AM demodulator 34 via line 33 to obtain Uref on line 19. The reference unit may be additionally provided with an FN demodulator 35 and a bit demodulator 36. In that case, signal E(t) is also used as an information rh~nnel. The information is FM modulated and transmitted with signal E(t). This enables the required angle ~g to which the correction of the pro~ectile is to be carried out to be received, FM demodulated and bit demodulated from signal E(t). In this case, receiver 9 of Fig. 1 is not required because reference unit 18 determines ~g by itself.
Fig. 8 represents a special embodiment of reference unit 18.
According to this embodiment, the task of antenna 17 is replaced by both antennas 15 and 16. For this purpose, reference unit 18 is provided with two b~ndp~ss filters 32A and 32B having the same function as the bandp~ss filter of Fig. 7. The output signal of b~ndp~ss filter 32B is supplied to a 90 phase shifter 37. The output signal of the phase shifter is supplied via line 38 to ~j in~ unit 40. Owing to the 90 phase shifter 37, the signals when summed will supplement each other and an output signal will be obtained having a constant amplitude. The output signal of s~ ~ng unit 40 is equal to the signal on line 33 as described in Fig. 7.
The output signal of &- ~ng unit 40 is processed by means of an AM demodulator 34, FM demodulator 35 and bit demodulator 36 in the same way as described for Fig. 7.
In Fig. 3 the directional antennas are represented as two loop antennas. However, it is also possible to use two perpendicularly disposed dipole antennes. In that case, the E field instead of the B field of the electromagnetic field is measured. Because the E
field and the B field are connected via the well-known relation of Naxwell, the principle of the invention remains the same. The dipole antennas are preferably positioned perpendicularly to the surface of the former loop antennas (see Fig. 4).
Fig. 4 represents, besides the B field, also the E field. In this case, the E field instead of the B field as represented in Fig. 3 now functions as reference for measuLc - t of the instantaneous angular position ~'m(t) of the projectile. A first dipole antenna is for this purpose positionet parallel with the x axis, while a second dipole antenna is positioned parallel with the y axis.
The E field at the dipole antennas is described by E(rO). The E field can be disintegrated into two components E(rO)// and E(rO) _ _ as represented in Fig. 9. Only the E(rO)l component will generate a voltage in the dipole antennas.
The E(rO)l field component can be expressed by:
E(rO)l - a' cos ~ot e (10) _ _ with e e _ _ (11) IE(rO)ll Voltage V'15 in the dipole antenna parallel with the x axis is equal to:
E(rO)l cos ~'m(t).h (12) where hs is the length of the dipole antenna. In a fully analogous way, voltage V'16 in the dipole antenna along the y asis is equal to 15 _ _ 16 E(rO)l sin ~'m(t).h (13) where hy is the length of the dipole antenna along the y axis.
Combination for fo- 1~s (11), (12) and (13) results in:
V'15 ~ a' hs cos ~ot-cos ~m(t) (14) 16 b hy cos ~Ot.sin ~' (t) (15) Fully analogous to the description to fo_ 1~s (5) and (6), angle ~'m(t) can be determined from formulas (14) and (15) by means of the reference signal of formula (7). Thus the instantaneous position of the pro~ectile is determined, as the E field is known.
A special s ho~ ~ t of the dipole antennas is represented in Fig. 10. Pro~ectile 41 in Fig. 10 is provided with two pairs of fins 42A, 42B, 43A and 43B. Fins 42A, 42B, like fins 43A, 43B, are positioned at opposite angles, while fins 42A and 43A on the one hand and 42B and 43B on the other hand are perpendicularly disposed.
Fins 42A and 42B together form a first dipole antenna 15 and fins 43A and 43B form a second dipole antenna 16 perpendicularly positioned to dipole antenna 15. In this case, the fins also function, like antenna 18, for reception of the data signal.
ignals V 15~ V 16~ ~ m(t)~ Uref and ~g can be dete_ ~ned by means of the fins as described above for Fig. 8.
It will be clear that it is not necessary to perpendicularly dispose the dipole antennas, loop antennas and/or fins. Moreover, for the sake of redun~ncy more than two antennas may be used. Thus for instance six fins may be fitted at a 60 angle.
If one dipole antenna and one loop antenna are used which are not perpendicularly disposed, the instantaneous angular spin position of the ob~ect can also be dete_ ned. If one dipole antenna 15 is parallel with a loop antenna 16 (parallel with the x axis), in a fully analogous way as described above:
V'15 ~ a' hx cos ~ot.cos ~'m(t) (16) 20 Vind - A cos ~ot cos ~m( ) (17) Because E and B are perpendicularly disposed:
~'m~t) ~ go _ ~m(t) (18) Substitution of (18) in (16) will result in:
V~ e a' hx cos ~o(t) sin ~m( ) (19) It will be clear that on the basis of fo l~s (19) and (17) the value of ~m(t) can be dete ~ned as described above because a', hx and A are also known.
It will be clear that the method for deteL ~n~n~ the angular spin position of an object with the aid of an receiving system according to Fig. 6 can also be used if the projectile now functioning as the first object is equipped with the transmitter ant antenna unit 7, while the receiving system 13 now functioning as the second ob~ect is installed, ~ointly with the loop or dipole antennas, on the ground (see Fig. 11).
Fully analogous to Fig. 1, the first target tracking means 3, the second target tracking means 4, and computing means 5 are used to determine the angular spin position ~g of the projectile; this requires a course correction of the projectile 1 to hit the target 2. To dete_ ~ne the angular spin position of the projectile, the transmitter and antenna unit 7 is contained in the projectile 1.
With the use of the loop or dipole antennas located on the ground and the receiving system 13, to which these antennas are mounted, it is possible to dete_ ~ne ~m(t) in the same way as in Fig. 1, as here a relative angular spin position of the projectile with respect to the system 13 is concerned. The output signal ~m~t) of the system 13 is applied to comparator 12. If the condition ~m(t) - ~g is fulfilled, the comparator delivers a control signal to transmitter unit 8. This control signal is sent out for reception by the receiver 9 in the projectile. In response to this, receiver 9 activates the gas discharge units 6. If a second course correction is found to be necessary, this entire process can repeat itself.
The invention relates to a system for dete ining the angular spin position of a second object spinning about an axis, where a first object emits elec~L. aP~etic waves and where the system is provided with directional receiving antenna means fitted to the second object, and with a receiving system which, using the receiving antenna means, process in combination the carrier waves received to obtain said angular spin position.
Such an arrangement is known from EP-A 0,239,156. This patent particularly applies to a second object in the shape of a projectile. In case of fired projectiles, such as shells, it is often desirable to change the course during the flight. However, since a shell spins about its axis along the tra;ectory, correction of its course is effective only if at any random instant the associated spin or roll position ~m(t) is well-known. Suitable course correction means for this purpose are preferably based on principles of the aerodynamics, the chemistry, the gas theory and the dynamics. In this respect, considered are the bringing out of damping fins or surfaces on the projectile's circumferential surface, the detonation of small charges on the projectile, and the ejection of a small mass of gas from the projectile.
According to the EP pstent specification this problem is solved by transmitting signals consisting of at least two superimposed phase-locked and polarised carrier waves having different frequencies. These signals are transmitted by the first object.
Thus it is possible to obtain a reference signal by processing both carrier waves in combination. This reference signal comprises phase information of both carrier waves. By means of this reference signal, the 180 uncertainty can be eliminated. It is clear from Fig. 1 of the EP patent that also a third carrier wave is present for transmitting data to the projectile by means of the transmitter.
After this, for instance, the information on angle ~g is transmitted upon which a correction is to be carried out by the pro~ectile.
For this purpose, the projectile itself dete_ ~neS the instantaneous angular spin position ~m(t) and carries out a correction as soon as ~g ~ ~m(t) The present invention has for its object to simplify and ~ ~Lvve the above system and is characterised in that the received signals comprise at least one first polarised carrier wave and a second carrier wave, which comprises phase information of the first carrier wave.
Contrary to the EP patent, according to the present invention, the information for obtaining the reference signal is carried fully by the second carrier wave. As a result, the receiving system of the second object (the projectile) may be of a much simpler and thus more cost-effective construction. Another advantage is that the reference signal may be dete ~ned more accurately. Noreover, the second carrier wave can be used to transmit other information (such as ~g), resulting in a further cost reduction because there will be no need for a third carrier wave.
According to a special embodiment of the invention, it is even feasible to use the fins of a projectile as an antenna system. By means of these fins, the first as well as the second carrier wave can be received. This results in a further cost reduction, while ~ ".~ving the robustness of the system.
According to another advantageous embodiment of the invention, the orientation of the first object is lln~ ,_L~ant in the determination of the angular spin position of the second object with respect to, for instance, the earth surface. This is not possible in conventional systems as the angular spin position of the second object is determined with the first object as reference. In conventional systems this implies that the orientation of the second object with respect to the earth surface must be known and be kept constant. If the first object is, for instance, a ship, a transmitter and antenna unit of the first object, transmitting the at least one polarised carrier wave, will have to be fitted on a stabilised platform. Only then it is possible in conventional systems to keep the polarisation direction of the transmitted carrier waves with respect to space (the earth surface) constant.
The use of a stabilised platform however is rather expensive.
Moreover, the means must be available to measure and process the position and orientation of the platform in order to obtain an angular spin position of the second object with respect to space.
This renders the system inaccurate as well as more expensive.
In conventional systems, a polarised carrier wave around the second object is obtained by transmitting a polarised carrier wave. This has the disadvantage that a polarising transmitter and antenna unit needs to be used. Such transmitter and antenna units have the disadvantage that they are rather bulky and thus quite expensive.
According to an especially cost-effective embodiment of the inventionr however, a transmitter and antenna unit is used which transmits carrier waves re~ch~ng up to and around the second object but also up to and interfering with the earth surface. Moreover, the transmitter and antenna unit of the first object is thus arranged that the frequency of the first carrier wave to be transmitted is ` 1 338629 relatively low, i.e. around 50 kHz. These technical measures result in a carrier wave of which the electric field component is vertically disposed with respect to the earth surface. The latter is entirely independent of the orientation of the transmitter and antenna unit. Similarly, the magnetic field component of the first carrier wave is horizontally disposed with respect to the earth surface. This results in the enormous advantage of being able to measure the rotation of the angular spin position of the second object with respect to the earth surface. Moreover, there is no need to fit the transmitter and antenna unit, when used on a ship, on to a stabilised platform.
The above also results in much simpler and cheaper embodiment of the transmitter and antenna unit, because said system needs not be suitable for the generation of polarised carrier waves with an accurately defined polarisation direction.
Moreover, determination and calculation of the angular spin position are also simpler and cheaper as the orientation of the first object is of no importance.
The invention will now be described in more detail with reference to the accompanying drawings, of which:
Fig. la is a schematic representation of a first embodiment of a complete system for the control of a projectile functioning as the second object, taking into account an apparatus according to the invention;
Fig. lb is a schematic representation of a projectile controlled by the system of Fig. la;
Fig. 2 represents a special embodiment of the system where . , , ~
` -- ~
the system is arranged in such a way that the orientation and position of the antenna unit of the system may remain undetermined.
Fig. 3 is a schematic representation of two perpendicularly disposed loop antennas placed in an electromagnetic field;
Fig. 4 is a schematic representation of two perpendicularly disposed dipole antennas placed in an electromagnetic field;
Fig. 5 is a diagram of a magnetic field at the location of the loop antennas;
Fig. 6 shows a schematic representation of the receiving system included in a projectile to determine the angular spin position of the projectile;
Fig. 7 is a first embodiment of a unit from Fig. 6;
Fig. 8 is a second embodiment of a unit from Fig. 6;
Fig. 9 is a diagram of an electric field at the location of the dipole antennas;
Fig. 10 is an embodiment of the projectile with dipole antennas;
Fig. lla is a schematic representation of a second embodiment of a complete system for the control of a projectile functioning as the first object, taking into account an apparatus according to the invention; and Fig. llb is a schematic representation of a projectile controlled by the system of Fig. lla.
In Fig. 1 it is assumed that a projectile 1 functioning as second object has been fired to hit a target 2. The target trajectory is tracked from the ground with the aid of target ,- ~ 5 tracking means 3. For this purpose, use may be made of a monopulse radar tracking unit operable in the K-band or of pulsed laser tracking means operable in the far infrared region. The trajectory of projectile 1 is tracked with comparable target tracking means 4. From the information of supplied target positions determined by target tracking means 3 and from supplied projectile positions determined by target tracking means 4, computing means 5 determines whether any course corrections of the projectile are necessary. To make a course correction, the projectile is provided with gas discharge units 6. Since the projectile rotates about its axis, a course correction requires the activation of a gas discharge unit at the instant the projectile assumes the correct position. To determine the correct position, carrier waves sent out by a transmitter and antenna unit 7 functioning as first object are utilised. Computing means 5 determines the desired projectile angular spin position ~g at which a gas discharge should occur with respect to the electromagnetic field pattern of the carrier waves at the projectile position.
5a ., The position and attitude of the transmitter and antenna unit 7 serve as reference for this purpose. This is possible, because the field pattern and the pro~ectile position in this field are known.
Accorting to a special embodiment of the invention, use of the position and orientation of the transmitter and antenna unit 7 as a reference is obviated. This is especially advantageous when the orientation of transmitter and antenna unit 7 is sub~ect to v~- ^nt, for instance, when it is placed on a ship (see Fig. 2). Antenna unit 7 of Fig. 2 is arranged in such a way that the transmitted carrier wave reaches up to and around the projectile and that the carrier wave reaches down to the earth surface. Moreover, the frequency of the transmitted carrier wave is relatively low with respect to conventional systems. The result of the above is that the electric field component E of the carrier wave is vertically polarised and that the magnetic field component is horizontally polarised with respect to the earth surface. The polarisation reaches greater heights as the frequency ~O becomes lower and as the antenna unit is placed closer to the earth surface.
As a result of these technical measures, the earth surface behaves as a flat conducting metal plate. The advantage is that the polarisation is independent of the orientation of antenna unit 7.
Angles ~m(t) and ~g(t) can then be determined with the earth surface as a reference.
Antenna unit 7 is of an especially simple and cost-effective type, viz. a single wire. No use is made, as for conventional systems, of a stabilised platform onto which the antenna unit is fitted. Antenna unit 7 will therefore continuously change orientation as a result of the roll of the ship. Antenna unit 7 is also not suitable for transmitting polarised carrier waves, having as an advantage that the length of the antenna unit 7 can be limited. In this case, antenna unit 7 concerns a communication antenna already present on the ship.
1 33~`~2~
The calculated value ~g is transmitted by means of transmitter 8.
For this purpose, transmitter 8 may be provided with its own antenna, as shown in Fig. 1, but may also use the c- ~cation antenna of the transmitter and antenna unit as shown in Fig. 2.
A receiver g, accommodated in the pro~ectile, receives from receiving antenna means 10 the value of ~g transmitted by transmitter 8. The received value ~g is supplied to a comparator 12 via line 11.
A receiving system 13, fed with the antenna signals of two perpendi-cularly disposed directional antennas contained in receiving antennameans 10, dete ~neS the instan~neo~s pro~ectile position ~m(t) with respect to the elecLL~ a~etic field at the location of the directional loop antennas. The instantaneous value ~m(t) is supplied to comparator 12 via line 14. When the condition ~m(t)- ~g has been fulfilled, comparator 12 delivers a signal S to activate the gas tischarge unit 6. At this moment a course correction is made.
Thereafter this entire process can be repeated if a second course correction is required.
It should be noted that it is also possible to make the desired course corrections without the use of second target tracking means 4.
The target tracking means 3 thereto measures the target tra~ectory.
From the measuring data of the target tra~ectory the computing means 5 makes a prediction of the rest of the target tra~ectory.
Computing means 5 uses this predicted data to calculate the direction in which the pro~ectile must be fired. The pro~ectile tra~ectory is calculated by computing means 5 from the pro~ectile ballistic data.
The target tracking means 3 keeps tracking the target 2. If it is found that target 2 suddenly deviates from its predicted tra~ectory, computing means 5 calculates the pro~ectile course correction to be made. It is thereby assumed that the pro~ectile follows its calculated tra~ectory. If the pro~ectile in flight nears the target, this target will also get in the beam of the target tracking means 3.
From this moment onward it is possible to track both the target and the projectile trajectories, permitting computing means 5 to make some pro~ectile course corrections, if necessary. As a result, any deviations from the calculated projectile tra~ectory, for example due to wind, are corrected at the same time.
It is also possible to eliminate the second tracking means 4 with the application of a time-sharing system. In such a case, the target and the pro~ectile tra~ectories are tracked alternately by means of target tracking means 3. Any course corrections of the pro~ectile are made analogously, as described hereinbefore.
Fig. 3 and Fig. 4 show the two perpendicularly disposed directional antennas 15 and 16, forming part of the receiving antenna means 10.
The antennas may comprise a B field or an E field. If two B fielt antennas are applied (such as represented in Fig. 3), the magnetic field c o~e~ts B of an elec~l. apnetic field are detected.
If two E field antennas are applied (such as represented in Fig. 4), the electric field c _.onents E of an elec~,- Q~netic field are detected. If one B field and one E field antenna are used, one subc ,_ ^nt of field component E and one subc. .onent of field c ,~onPnt B are detected. Because field cs ,~.^nts E and B are connected to eachother via the so-called relation of Maxwell, measuLe --t of at least one of the components E or B, or of one s~bc~ , ^nt of the E c _, ent and one subcomponent of the B
will suffice.
For measuring the B component, a loop antenna can be used, while a dipole antenna may be used for measuring the E component.
An x,y,z coordinate system is coupled to one of the loop antennas.
The propagation direction v of the projectile is parallel to the z-axis. The magnetic field c ,~.^nt B, transmitted by transmitter 8 has the magnitude and direction B(rO) at the location of the loop antennas. Here rO is the vector with the transmitter ant the antenna unit 7 as origin and the origin of the x,y,z coordinate system as end point. The magnetic field c ,~.^nt B(rO) can be resolved into a component B(rO)// (parallel to the z-axis) and the component B(rO)l (perpendicular to the z-axis). Only the components B(rO)l can generate an induction voltage in the two loop antennas. Therefore, as reference for the determination of ~m(t) use is made of B(rO)l. In this case, ~m(t) is the angle between the x-axis and B(rO)l, see Fig. 5. Since the computing means is capable of calculating v from the supplied pro~ectile positions r, computing means 5 can also calculate B(rO)l from B(rO) and define ~g with respect to this c ~o~^nt.
Fig. 6 is a schematic representation of the receiving system 13.
In the embodiment of system 13 in Fig. 6 it is assumed that the transmitter sends out an elecL~ .^etic field consisting of a polarised carrier wave with frequency ~O. The magnetic field cc ,_ ^nt Bl(rO) can be defined as ~
Bl(rO) ~ (a sin ~Ot)e, where _ _ ~ e (1) The magnetic flux ~15 through the loop antenna 15 can be defined as:
~15 = (a sin ~ot).S.cos ~m(t) (2) In this formula, S is equal to the area of the loop antenna 15.
The magnetic flux ~16 through loop antenna 16 can be tefined as:
~16 ~ (a sin ~Ot).S.sin ~m(t) (3) The induction voltage in loop antenna 15 is now equal to:
indl5 -e dt ~ -e(a wO cos ~ot).S.cos ~ (t) +
d~m + -e(a sin ~Ot).S.sin ~m(t)- dt (4) Here ~ is a constant which is dependent upon the used loop antennas d~
15, 16. Since the projectile speed of rotation dt is much smaller than the angular frequency ~O, it can be approximated that:
indl5 -~(a ~O cos ~Ot)~o(t).s.cos ~ (t) -e (A cos ~ot).cos ~m(t) (5) Similarly, for loop antenna 16:
Vind ~ (A cos ~ot).sin ~m( ) (6) Transmitter 8 also transmits an elecLL. ag~etic wave E where:
E(t) ~ G(t) cos ~lt with G(t) - D.(l - ~ wot).
In this formula, D is a constant and ~ the modulation depth, so < ~ < 1. Also, ~1 ~0- According to this embodiment, frequency ~1 is FM- -d~ ted to comprise the information concerning ~g.
The elec~,. a~etic wave is therefore modulated with cos ~ot and thus comprises phase information of the signal transmitted by antenna unit 7. Receiving antenna means lO is provided with an antenna 17 for the reception of signal E(t). Antenna 17 is linked with a reference unit 18, which generates a reference signal Uref from the received signal E(t), with U - C cos ~ t . (7) ref o Here C is a constant which is dependent upon the specific embodiment of reference unit 18. The Uref signal is supplied to mixers 20 and 21 via line 19.
Signal Vind (t) is also applied to mixer 20 via line 22.
The output signal of mixer 20 is applied to low-pass filter 24 via line 23. The output signal U24(t) of the low-pass filter 24 (the t~
c~ Eone~t of frequency dt ) is equal to:
U (t) = AC cos ~ (t) (8) In a fully analogous way, signal Vind (t) is fed to mixer 21 via line 25. The output signal of mixer 21 is fed to a low-pass filter 27 via line 26. Output signal U27(t) of the low-pass filter 27 is equal to:
U27(t) e 2 sin ~m(t) (9) From formula (8) and (9) and for a given U24(t) and U27(t), it is simple to determine ~m(t)~ To this effect, signals U24(t) and U27(t) are sent to a trigonometric unit 30 via lines 28 and 29. In response to these signals, trigonometric unit 30 generates ~m(t)~
Trigonometric unit 30 may, for instance, function as a table look-up unit. It is also possible to have the trigonometric unit functioning as a computer to generate ~m(t) via a certain algorithm.
Fig. 7 represents an embodiment of reference unit 18. Antenna signal E(t) is supplied to a b~ndpass filter 32 via line 31. B~ndpflss filter 32 only passes signals with a frequency of arount ~1 Signal B(t) will therefore not be passed. Signal E(t) is subsequently supplied to an AM demodulator 34 via line 33 to obtain Uref on line 19. The reference unit may be additionally provided with an FN demodulator 35 and a bit demodulator 36. In that case, signal E(t) is also used as an information rh~nnel. The information is FM modulated and transmitted with signal E(t). This enables the required angle ~g to which the correction of the pro~ectile is to be carried out to be received, FM demodulated and bit demodulated from signal E(t). In this case, receiver 9 of Fig. 1 is not required because reference unit 18 determines ~g by itself.
Fig. 8 represents a special embodiment of reference unit 18.
According to this embodiment, the task of antenna 17 is replaced by both antennas 15 and 16. For this purpose, reference unit 18 is provided with two b~ndp~ss filters 32A and 32B having the same function as the bandp~ss filter of Fig. 7. The output signal of b~ndp~ss filter 32B is supplied to a 90 phase shifter 37. The output signal of the phase shifter is supplied via line 38 to ~j in~ unit 40. Owing to the 90 phase shifter 37, the signals when summed will supplement each other and an output signal will be obtained having a constant amplitude. The output signal of s~ ~ng unit 40 is equal to the signal on line 33 as described in Fig. 7.
The output signal of &- ~ng unit 40 is processed by means of an AM demodulator 34, FM demodulator 35 and bit demodulator 36 in the same way as described for Fig. 7.
In Fig. 3 the directional antennas are represented as two loop antennas. However, it is also possible to use two perpendicularly disposed dipole antennes. In that case, the E field instead of the B field of the electromagnetic field is measured. Because the E
field and the B field are connected via the well-known relation of Naxwell, the principle of the invention remains the same. The dipole antennas are preferably positioned perpendicularly to the surface of the former loop antennas (see Fig. 4).
Fig. 4 represents, besides the B field, also the E field. In this case, the E field instead of the B field as represented in Fig. 3 now functions as reference for measuLc - t of the instantaneous angular position ~'m(t) of the projectile. A first dipole antenna is for this purpose positionet parallel with the x axis, while a second dipole antenna is positioned parallel with the y axis.
The E field at the dipole antennas is described by E(rO). The E field can be disintegrated into two components E(rO)// and E(rO) _ _ as represented in Fig. 9. Only the E(rO)l component will generate a voltage in the dipole antennas.
The E(rO)l field component can be expressed by:
E(rO)l - a' cos ~ot e (10) _ _ with e e _ _ (11) IE(rO)ll Voltage V'15 in the dipole antenna parallel with the x axis is equal to:
E(rO)l cos ~'m(t).h (12) where hs is the length of the dipole antenna. In a fully analogous way, voltage V'16 in the dipole antenna along the y asis is equal to 15 _ _ 16 E(rO)l sin ~'m(t).h (13) where hy is the length of the dipole antenna along the y axis.
Combination for fo- 1~s (11), (12) and (13) results in:
V'15 ~ a' hs cos ~ot-cos ~m(t) (14) 16 b hy cos ~Ot.sin ~' (t) (15) Fully analogous to the description to fo_ 1~s (5) and (6), angle ~'m(t) can be determined from formulas (14) and (15) by means of the reference signal of formula (7). Thus the instantaneous position of the pro~ectile is determined, as the E field is known.
A special s ho~ ~ t of the dipole antennas is represented in Fig. 10. Pro~ectile 41 in Fig. 10 is provided with two pairs of fins 42A, 42B, 43A and 43B. Fins 42A, 42B, like fins 43A, 43B, are positioned at opposite angles, while fins 42A and 43A on the one hand and 42B and 43B on the other hand are perpendicularly disposed.
Fins 42A and 42B together form a first dipole antenna 15 and fins 43A and 43B form a second dipole antenna 16 perpendicularly positioned to dipole antenna 15. In this case, the fins also function, like antenna 18, for reception of the data signal.
ignals V 15~ V 16~ ~ m(t)~ Uref and ~g can be dete_ ~ned by means of the fins as described above for Fig. 8.
It will be clear that it is not necessary to perpendicularly dispose the dipole antennas, loop antennas and/or fins. Moreover, for the sake of redun~ncy more than two antennas may be used. Thus for instance six fins may be fitted at a 60 angle.
If one dipole antenna and one loop antenna are used which are not perpendicularly disposed, the instantaneous angular spin position of the ob~ect can also be dete_ ned. If one dipole antenna 15 is parallel with a loop antenna 16 (parallel with the x axis), in a fully analogous way as described above:
V'15 ~ a' hx cos ~ot.cos ~'m(t) (16) 20 Vind - A cos ~ot cos ~m( ) (17) Because E and B are perpendicularly disposed:
~'m~t) ~ go _ ~m(t) (18) Substitution of (18) in (16) will result in:
V~ e a' hx cos ~o(t) sin ~m( ) (19) It will be clear that on the basis of fo l~s (19) and (17) the value of ~m(t) can be dete ~ned as described above because a', hx and A are also known.
It will be clear that the method for deteL ~n~n~ the angular spin position of an object with the aid of an receiving system according to Fig. 6 can also be used if the projectile now functioning as the first object is equipped with the transmitter ant antenna unit 7, while the receiving system 13 now functioning as the second ob~ect is installed, ~ointly with the loop or dipole antennas, on the ground (see Fig. 11).
Fully analogous to Fig. 1, the first target tracking means 3, the second target tracking means 4, and computing means 5 are used to determine the angular spin position ~g of the projectile; this requires a course correction of the projectile 1 to hit the target 2. To dete_ ~ne the angular spin position of the projectile, the transmitter and antenna unit 7 is contained in the projectile 1.
With the use of the loop or dipole antennas located on the ground and the receiving system 13, to which these antennas are mounted, it is possible to dete_ ~ne ~m(t) in the same way as in Fig. 1, as here a relative angular spin position of the projectile with respect to the system 13 is concerned. The output signal ~m~t) of the system 13 is applied to comparator 12. If the condition ~m(t) - ~g is fulfilled, the comparator delivers a control signal to transmitter unit 8. This control signal is sent out for reception by the receiver 9 in the projectile. In response to this, receiver 9 activates the gas discharge units 6. If a second course correction is found to be necessary, this entire process can repeat itself.
Claims (39)
1. A system comprising a first and a second object, for determining the angular spin position of the second object spinning about an axis, in which the first object emits electromagnetic carrier waves and the system is provided with directional receiving antenna means fitted to the second object, and with receiving means which, using the receiving antenna means, process in combination the carrier waves received to obtain said angular spin position, characterised in that the carrier waves comprise at least one first polarised carrier wave and a second carrier wave which comprises phase information of the first carrier wave.
2. A system as claimed in claim 1, characterised in that the receiving antenna means is provided with a loop antenna and a dipole antenna which are disposed other than perpendicularly.
3. A system as claimed in claim 1 in which the second object consists of a projectile, characterised in that the receiving antenna means comprise first and second antennas which are connected to the projectile on the side turned away from the direction of flight.
4. A system as claimed in claim 1, in which the second object comprises a missile having fins, characterised in that the fins of the missile serve as first and second antenna means.
5. A system as claimed in claim 4, characterised in that the missile is provided with four fins where adjacent fins are positioned at 90° angles.
6. A system as claimed in claim 1, characterised in that the second carrier wave has a modulation comprising a predetermined phase relation with the phase of the frequency of the first carrier wave.
7. A system as claimed in claim 6, characterised in that the modulation involves an amplitude modulation.
8. A system as claimed in claim 7, characterised in that the phase of the amplitude modulation equals the phase of the frequency of the first carrier wave.
9. A system as claimed in one of the claims 1-7, characterised in that the second carrier wave has a frequency which is not the same as the frequency of the first carrier wave.
10. A system as claimed in claim 9, characterised in that the frequency of the first carrier wave is lower than the frequency of the second carrier wave.
11. A system as claimed in claim 1, characterised in that the second carrier wave also sends information.
12. A system as claimed in claim 1, characterised in that the receiving antenna means is at least provided with a first and a second directional antenna having a different orientation with respect to each other.
13. A system as claimed in claim 12, characterised in that both antennas are perpendicularly disposed.
14. A system as claimed in one of the claims 12 or 13, characterised in that the first and the second antenna are both provided with a loop antenna.
15. A system as claimed in one of the above claims 12 or 13, characterised in that the first and the second antenna are both provided with a dipole antenna.
16. A system as claimed in one of the claims 11-13, characterised in that the first and the second antenna are arranged to receive said carrier waves.
17. A system as claimed in one of the claims 11-13, characterised in that the receiving antenna means is provided with a third antenna for the reception of the second carrier wave while the first and the second antenna are arranged to receive the first carrier wave.
18 18. A system as claimed in claim 12, characterised in that the receiving means comprises: a. a reference unit for obtaining a reference signal from the second carrier wave re-ceived by the receiving antenna means, the phase of said re-ference signal having a predetermined relation with the phase of the carrier wave frequency of said first carrier wave; b. a first and a second mixer for mixing with said reference signal the first carrier wave received by means of the first or the second directional antenna; c. a first and a second filter unit for filtering the output signals of said first and second mixers, said filters passing only frequency components equal or substantially equal to zero; and d. a trigonometric unit controlled by the output signals of the first and second filters, which trigonometric unit generates a signal repre-senting the instantaneous angle between one of the antennas and the polarisation direction of the carrier wave.
19. A system as claimed in claim 18, characterised in that the reference unit comprises a phase-shifter for shifting the components of the first and second carrier wave, received by the receiving antenna means, 90° with respect to each other, a summing unit for summing the components shifted in phase with respect to each other, and a demodulator for demod-ulating the summing signal of the summing unit where the demodulated signal serves as reference signal.
20. A system as claimed in claim 18, characterised in that the reference unit is provided with a demodulator for obtaining a reference signal from the second carrier wave received by means of a third antenna.
21. A system as claimed in claim 18, characterised in that the second carrier wave includes data information and the reference unit is provided with a filter for filtering out the data information.
22. A system as claimed in claim 18, characterised in that the trigonometric unit consists of a table-look-up generator generating ? from two input signals A cos ? and A sin ?.
23. A system as claimed in claim 18, characterised in that the trigonometric unit consists of a computer calculating ? from two input signals A cos ? and A sin ?.
24. A system as claimed in claim 1, where the first object is provided with a transmitter and antenna unit having such a range that the at least one carrier wave reaches up to and around the second object as well as down to the earth surface.
25. A system as claimed in claim 24, where the at least one carrier wave has an electric field component having an orientation which is independent of the orientation of the transmitter and antenna unit.
26. A system as claimed in one of the above claims 24 or 25, where the angular spin position is measured of the second object with respect to the earth surface.
27. A system as claimed in one of the above claims 24 or 25, where the frequency of the first carrier wave is around 50 kHz.
28. A system as claimed in one of the above claims 24 or 25, where the first object comprises a vehicle and where the transmitter and antenna unit is rigidly or almost rigidly connected to the vehicle.
29. A system as claimed in claim 28, where the vehicle is a skip.
30. A projectile including means for determining an angular spin position of the projectile relative to a first object from electromagnetic carrier waves received from the first object, said carrier waves comprising a first polarized carrier wave and a second carrier wave including phase information of the first carrier wave, said projectile including directional receiving antenna means for receiving the carrier waves and receiving means coupled to the antenna means for processing said carrier waves to obtain said angular spin position.
31. A projectile as in claim 30 where the antenna means comprises first and second antennas for receiving the first carrier wave and a third antenna for receiving the second carrier wave.
32. A projectile as in claim 31 where the receiving means comprises: a. a reference unit for obtaining a reference signal from the second carrier wave received by the receiving antenna means, the phase of said reference siganl having a predetermined relation with the phase of the carrier wave frequency of said first carrier wave; b. a first and a second mixer for mixing with said reference signal the first carrier wave received by means of the first or the second directional antenna; c. a first and a second filter unit or filtering the output signals of said first and second mixers, said filters passing only frequency components equal or substantially equal to zero; and d. a trigonometric unit controlled by the output signals of the first and second filters, which trigonometric unit generates a signal representing the instantaneous angle between one of the antennas and the polarisation direction of the carrier wave.
33. A projectile as in claim 32 where the reference unit comprises a phase-shifter for shifting the components of the first and second carrier wave, received by the receiving antennas means, 90° with respect to each other, a summing unit for summing the components shifted in phase with respect to each other, a demodulator for demodulating the summing signal of the summing unit where the demodulated signal serves as reference signal.
34. A projectile as in claim 32 where the reference unit includes a demodulator for obtaining a reference signal from the second carrier wave.
35. A projectile as in claim 32 where the second carrier wave includes data information and the reference unit includes a filter for filtering out said data information.
36. A projectile as in claim 30 where the antenna means comprises first and second directional antennas having different orientations with respect to each other.
37. A projectile as in claim 36 where the first and second directional antennas are perpendicularly disposed with respect to each other.
38. A projectile as in claim 36 or 37 where first and second directional antennas comprise loop antennas.
39. A projectile as in claim 36 or 37 where first and second directional antennas comprise dipole antennas.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL8801203A NL8801203A (en) | 1988-05-09 | 1988-05-09 | Determining system for angular position of spinning projectile - uses low frequency carrier wave horizontally polarised w.r.t. each surface independently on transmitting aerial orientation |
| NL8801203 | 1989-01-19 | ||
| NL8900117A NL8900117A (en) | 1988-05-09 | 1989-01-19 | SYSTEM FOR DETERMINING THE ROTATION POSITION OF AN ARTICLE ROTATABLE ON AN AXLE. |
| NL8900117 | 1989-01-19 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1338629C true CA1338629C (en) | 1996-10-01 |
Family
ID=26646381
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000598540A Expired - Fee Related CA1338629C (en) | 1988-05-09 | 1989-05-03 | System for determining the angular spin position of an object spinning about an axis |
Country Status (4)
| Country | Link |
|---|---|
| KR (1) | KR890017825A (en) |
| CA (1) | CA1338629C (en) |
| DK (1) | DK172493B1 (en) |
| TR (1) | TR24195A (en) |
-
1989
- 1989-05-03 CA CA000598540A patent/CA1338629C/en not_active Expired - Fee Related
- 1989-05-05 TR TR89/0379A patent/TR24195A/en unknown
- 1989-05-08 DK DK198902249A patent/DK172493B1/en not_active IP Right Cessation
- 1989-05-08 KR KR1019890006108A patent/KR890017825A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| DK224989D0 (en) | 1989-05-08 |
| DK172493B1 (en) | 1998-10-12 |
| KR890017825A (en) | 1989-12-18 |
| TR24195A (en) | 1991-07-01 |
| DK224989A (en) | 1989-11-10 |
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