DESC:ELECTROMAGNETIC BEAM MODULATION AND ENCODING SYSTEM FOR GUIDANCE OF GUIDED WEAPON
TECHNICAL FIELD
[0001] The present disclosure described herein, in general, relates to the guidance of guided weapons like anti-tank guided missiles (ATGM), guided bombs, etc. In particular, the present disclosure relates to an electromagnetic beam modulation and encoding system for the guidance of a guided weapon.
BACKGROUND
[0002] The background description includes information that may be useful in understanding the present disclosure. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed subject matter, or that any publication specifically or implicitly referenced is prior art.
[0003] A typical electromagnetic beam guidance system of a guided weapon comprises an electromagnetic beam source as a radiation source for generating a controlled field around the line of sight, an electromagnetic beam modulation and encoding system for receiving and spatially encoding the electromagnetic beam and a beam shaping and projection system to project the encoded electromagnetic beam towards a target that leads to the guidance of the guided weapon. The key element of such a guidance system is the electromagnetic beam modulation and encoding system wherein spatially encoding the electromagnetic beam involves the generation of guidance signals in the form of frequencies. The guided weapon automatically responds to these guidance signals or frequencies with the help of a receiver in seeking the center of the electromagnetic beam pre-fired by a gunner to maintain a line of sight till the guided weapon impacts or hits a target. The receiver computes a deviation of the guided weapon with respect to the electromagnetic beam or a target based on the received frequencies, if any, and corrects the deviation on its own to bring the guided weapon in the line of sight. A typical electromagnetic beam modulation and encoding system comprise a disc-shaped reticle or optical chopper for spatially encoding the electromagnetic beam that rotates about its axis. However, all the existing electromagnetic beam modulation and encoding system have certain drawbacks in the form of
• Nutation: Complex off-centered circular motion of the optical chopper
• Usage of double or plural discs of the optical chopper: two-disc or more than the two-discs system needs synchronizations that are complex in nature, and requires high torque motors to drive,
• Non-Linear encoding of space around the line of sight causing more computational load on the receiver of the guided weapon
[0004] The above-mentioned drawbacks make the whole system expensive and complex. Further, the system forces the usage of a plurality of receivers in the guided weapon.
[0005] In view of the above-mentioned issues, there is a need to provide a solution that overcomes the drawbacks of the existing electromagnetic beam modulation and encoding system.
OBJECTS OF THE DISCLOSURE
[0006] Some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed hereinbelow.
[0007] It is a general or primary object of the present disclosure to provide an electromagnetic beam modulation and encoding system for the guidance of a guided weapon that doesn’t involve nutation, double or a plurality of optical chopper discs and provides a linear encoding of the space around the line of sight for the guided weapon.
[0008] It is another object of the present disclosure to provide an electromagnetic beam modulation and encoding system for the guidance of a guided weapon that is of low cost and simple in construction.
[0009] It is yet another object of the present disclosure to provide a single onboard receiver of a guided weapon to receive guidance signals from a guidance unit.
[0010] These and other objects and advantages will become more apparent when reference is made to the following description and accompanying drawings.
SUMMARY
[0011] This summary is provided to introduce concepts primarily related to an electromagnetic beam modulation and encoding system for the guidance of a guided weapon. The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[0012] The subject matter disclosed herein relates to an electromagnetic beam modulation and encoding system for the guidance of a guided weapon. The system comprises a disc-shaped optical chopper to receive and encode an electromagnetic beam, the optical chopper having embossed portions for generating spatial frequencies for spatial encoding and un-embossed portions formed by two transparent portions wherein the embossed portion is formed by two patterns, the first pattern is formed at the outer circumference between two radii R1 and R2 of the optical chopper and the second pattern is formed at the inner circumference between two radii R3 and R4 of the optical chopper. The first pattern and the first transparent portion forms an outer track and the second pattern and the second transparent portion forms an inner track. The outer track is bigger than the inner track. The system further comprises a dove prism communicatively coupled with the optical chopper. As the disclosed electromagnetic beam modulation and encoding system comprise only a single optical chopper there is no requirement of any synchronization and high torque to rotate it. The optical chopper is rotatable at a constant speed about a central axis with the help of a motor drive.
[0013] In an aspect, the first pattern is formed at a 90-degree to the second pattern.
[0014] In yet another aspect, the radius R1 is greater than the radius R2 and the radius R3 is greater than the radius R4. The radius (R2) is greater than the radius (R3). The difference between the radius (R1) and the radius (R2) is equal to the difference between the radius (R3) and the radius (R4).
[0015] In another aspect, the first pattern and the second pattern are of semi-circular shape. Further, the un-embossed transparent portions are also of semi-circular shape.
[0016] In yet another aspect, the optical chopper is made of glass or quartz and the optical chopper is rotatable at a constant speed about a central axis with the help of a motor drive. This helps in obviating nutation.
[0017] In another aspect, the first embossed pattern generates guidance signals or frequencies related to the pitch channel and the second embossed pattern generates frequencies or guidance signals related to the yaw channel. The pitch channel and the yaw channel are generated alternatively.
[0018] In an aspect, the patterns are so arranged that while in operation, pitch channel and yaw channel do not overlap. In an aspect, the optical chopper generates the frequencies for the duration which also linearly encodes the spatial deviation of the guided weapon to the line of sight.
[0019] Since the disclosed electromagnetic beam modulation and encoding system obviates nutation, usage of double or a plurality of optical chopper discs, and non-linear encoding the said disclosed system becomes simpler and economical.
[0020] To further understand the characteristics and technical contents of the present subject matter, a description relating thereto will be made with reference to the accompanying drawings. However, the drawings are illustrative only but not used to limit the scope of the present subject matter.
[0021] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and methods that are consistent with the subject matter as claimed herein, wherein:
[0023] FIG. 1A illustrates an optical chopper of an electromagnetic beam modulation and encoding system in accordance with the present disclosure;
[0024] FIG. 1B illustrates other components of the electromagnetic beam modulation and encoding system connected with the optical chopper in accordance with the present disclosure;
[0025] FIG. 2A illustrates projection of generated frequencies by the optical chopper of the electromagnetic beam modulation and encoding system in accordance with the present disclosure;
[0026] FIG. 2B illustrates a projection of generated frequencies in different quadrants in accordance with the present disclosure; and
[0027] FIG. 3 illustrates a block diagram 100 of an onboard receiver of a guided weapon in accordance with the present disclosure.
[0028] The figures depict embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION
[0029] The detailed description of various exemplary embodiments of the disclosure is described herein with reference to the accompanying drawings. It should be noted that the embodiments are described herein in such details as to communicate the disclosure. However, the amount of details provided herein is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0030] It is also to be understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and embodiments of the present disclosure, as well as specific examples, are intended to encompass equivalents thereof.
[0031] The terminology used herein is to describe particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “includes” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.
[0032] It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
[0033] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
[0034] The present disclosure provides an electromagnetic beam modulation and encoding system for the guidance of a guided weapon. The guided weapon can be but not limited to antitank and assault, air-to-surface, air-to-air, anti-ship, and surface-to-air missiles, ballistic missiles, guided bombs, etc. designed for any particular range. In a preferred embodiment, the guided weapon is essentially an anti-tank guided missile (ATGM) or guided bombs operated with a beam rider guidance system. The electromagnetic beam modulation and encoding system is located between a source of the electromagnetic beam and a system for beam shaping and projection. The electromagnetic beam modulation and encoding system comprise an optical chopper 100 as shown in FIG. 1A to receive and spatially encode an electromagnetic beam from the radiation source. In a preferred aspect, the electromagnetic beam is a laser beam. The optical chopper 100 is in the shape of a disc and has embossed portions 102 forming patterns or tracks for the generation of spatial frequencies for spatial encoding the electromagnetic beam and un-embossed portions formed by two transparent portions 104a, 104b. The embossed portions 102 are formed by two patterns 102a, 102b, the first pattern 102a is formed between a radius R1 and a radius R2 of the optical chopper 100 and the second pattern 102b is formed between a radius R3 and a radius R4 of the optical chopper 100. In an aspect, the patterns 102a, 102b, and the transparent portions 104a, 104b are of semi-circular shape. In an aspect, the radius R1 is greater than the radius R2 and the radius R3 is greater than the radius R4. In another aspect, the radius (R2) is greater than the radius (R3). The difference between the radius R1 and the radius R2 is equal to the difference between the radius R3 and the radius R4 and the difference between the radii is equal to the diameter of an illuminating spot of the electromagnetic beam. The transparent portions 104 can also be considered to be formed by two transparent portions 104a and 104b depicted by the dotted line. The dotted lines are just for the purpose of illustration and clarity and help in understanding the invention in a better way. Although a person skilled in the art would not be able to differentiate the transparent portions 104a and 104b the first transparent portion 104a and the second transparent portion 104b can be viewed and considered to correspond with the first pattern 102a and the second pattern 102b respectively. In summary, the optical chopper 100 can be considered to comprise two circular tracks, an outer track, and an inner track. The outer track is formed by an embossed portion 102a and a un-embossed transparent portion 104a. Similarly, the inner track is formed by an embossed portion 102b and a un-embossed transparent portion 104b. The outer track is formed at outer circumference whereas the inner track is formed at the inner circumference. The outer track is bigger than the inner track i.e. the boundaries of the outer track are formed at larger radii than the boundaries of the inner track. Also, the ratio of the area of the embossed portion to the un-embossed transparent portion in each track may or may not be equal. It is to be noted that the values of the radii although not been provided but can possess any value. The optical chopper 100 is made up of quartz or glass. The optical chopper 100 is rotatable at a constant speed about a central axis 1-1 with the help of a motor drive 108 shown in FIG. 1B. As the optical chopper 100 rotates about the central axis only and not on an off-centered axis nutation is avoided. Further, since the disclosed electromagnetic beam modulation and encoding system comprise only a single optical chopper 100 there is no requirement of any synchronization and high torque to rotate it. The first pattern 102a is formed at a 90-degree to the second pattern 102b. The electromagnetic beam modulation and encoding system further comprise a dove prism 108 communicatively coupled with the optical chopper 100 as shown in FIG.1B.
[0035] The first pattern 102a generates frequencies or guidance signals related to pitch channel i.e. y-plane and the second pattern 102b generates frequencies or guidance signals related to yaw channel i.e. x-plane. The patterns 102a, 102b are designed such that the duration of the frequencies linearly encodes the space with respect to the deviation of the guided weapon to the line of sight. When the optical chopper 100 rotates about the central axis 1-1 at a specified constant rate say 100 Hz (10 msec. per rotation), four different frequencies and a common frequency or a center frequency namely yaw-right f1, yaw-left f2, pitch-up f3, yaw-left f4, and f5 are generated in space as shown in FIG. 2A. The frequency f5 represents the center of the line of sight. The frequencies related to the pitch channel and the frequencies related to the yaw channel are generated alternatively. Therefore, the time for the pitch and yaw channel frequencies being projected in the space would be 5 msec. each. In operation, the optical chopper 100 when illuminated by the electromagnetic beam (essentially a laser beam with less atmospheric attenuation), the electromagnetic beam gets chopped and generates the guidance signals or frequencies corresponding to the first pattern 102a or the second pattern 102b from which is it getting chopped. Essentially it generates the plurality (pair) of frequencies as shown in FIG. 2B for the guidance of the guided weapon in different quadrants. For instance, if the electromagnetic beam is being chopped from the first pattern 102a embossed for pitch channel, the electromagnetic beam falls on the dove prism 108 and is reflected back passing through the transparent portion 104b formed on inner track of the optical chopper 100 and thus carry the information of pitch channel (up and down) only. While the optical chopper 100 is in operation and rotates by 180-degree the electromagnetic beam from the outer pattern 102a goes un-chopped or un-modulated through un-embossed transparent portion 104a of the outer track of the optical chopper 100 and it starts getting chopped from the second pattern 102b of the optical chopper 100 and hence it carries the information of yaw channel (left or right) only. This way guidance signals or frequencies in both pitch and yaw channel are generated which in turn passes from the beam shaping projection system to get projected in the space for guiding the guided weapon. Depending upon the relative position of the guided weapon within the field of view, a receiver (not shown) of the guided weapon acquires the frequencies, being projected from the beam shaping and projection system. The receiver filters two frequencies, one for each channel (pitch or yaw). Accordingly, it estimates its location in the quadrant and passes a control signal to a control and actuation system (not shown) of the guided weapon to correct its trajectory by bringing it to the line of sight which is essentially the center of the electromagnetic beam pre-fired by a gunner (not shown). At the center, the receiver only receives f5 frequency. For instance, if the guided weapon is in the first quadrant of the electromagnetic beam, the receiver will receive only two frequencies, say f1 and f3, and accordingly, a control signal will be generated to correct the deviation of the guided weapon. It should be understood that the described example is essential for describing the present disclosure only and not in any way for restriction or limit the scope of the invention. Since the disclosed electromagnetic beam modulation and encoding system obviates nutation, usage of double or a plurality of optical chopper discs, and non-linear encoding the electromagnetic beam modulation and encoding system becomes simpler and economical.
[0036] FIG. 3 shows a block diagram 300 of an onboard receiver of a guided weapon. Only a single receiver is used that comprises a silicon photodiode 302 that is sensitive towards a spatially modulated electromagnetic beam (usually at 1064 nm) and a signal conditioning element or bandpass filter 304 to filter the frequencies or guidance signal of the spatially modulated electromagnetic beam. In an aspect, the onboard receiver is equipped with five bandpass filters (centered at the frequencies f1, f2, f3, f4, and f5) as shown in the FIG. 3. As already discussed, the receiver will receive a set of frequency (one after another) comprising of pitch channel (y-plane) and yaw channel (x-plane). Upon receiving these frequencies, the output from corresponding filter 304 will go high. These outputs are then taken to a microcontroller 306, preferably an Arduino for converting analog output signals to digital signals and deciding on which two frequencies are being received by the on-board receiver to estimate the quadrant in which the guided weapon is present. This information will be forwarded to an on-board processor 308 that commands a control and actuation system 310 for taking necessary correction for guiding the weapon by generating and sending a control signal.
TECHNICAL ADVANTAGES
[0037] The present disclosure provides an electromagnetic beam modulation and encoding system for the guidance of a guided weapon that doesn’t involve nutation, double or a plurality of optical chopper discs and provides a linear encoding of the space around the line of sight for the guided weapon.
[0038] The present disclosure provides an electromagnetic beam modulation and encoding system for the guidance of a guided weapon that is of low cost and simple in construction.
[0039] The present disclosure also provides a single onboard receiver of a guided weapon to receive guidance signals from a guidance unit.
[0040] While the foregoing describes various embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The present disclosure is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the present disclosure when combined with information and knowledge available to the person having ordinary skill in the art.
,CLAIMS:We claim:
1. An electromagnetic beam modulation and encoding system for guidance of a guided weapon, the electromagnetic beam modulation and encoding system comprising:
a disc-shaped optical chopper (100) to receive and encode an electromagnetic beam, the optical chopper (100) having embossed portions (102) for generating spatial frequencies for spatial encoding and un-embossed portions (104) formed by two transparent portions (104a, 104b) wherein the embossed portions (102) are formed by two patterns (102a, 102b), the first pattern (102a) is formed between a radius (R1) and a radius (R2) of the optical chopper (100) and the second pattern (102b) is formed between a radius (R3) and a radius (R4) of the optical chopper (100).

2. The system as claimed in claim 1, wherein the first pattern (102a) is formed at a 90-degree to the second pattern (102b).

3. The system as claimed in claim 1, wherein the patterns (102a, 102b) and the transparent portions (104a, 104b) are of semi-circular shape.

4. The system as claimed in claim 1, wherein the radius R1 is greater than the radius R2 and the radius R3 is greater than the radius R4.

5. The system as claimed in claim 1, wherein the radius (R2) is greater than the radius (R3).

6. The system as claimed in claim 1, wherein the difference between the radius (R1) and the radius (R2) is equal to the difference between the radius (R3) and the radius (R4).

7. The system as claimed in claim 1, wherein the optical chopper (100) is rotatable at a constant speed about a central axis (1-1) with the help of a motor drive (106).

8. The system as claimed in claim 1, comprises a dove prism (108) communicatively coupled with the optical chopper (100).

9. The system as claimed in claim 1, wherein the first pattern (102a) generates frequencies related to pitch channel and the second pattern (102b) generates frequencies related to yaw channel.

10. The system as claimed in claim 8, wherein the frequencies related to the pitch channel and the frequencies related to the yaw channel are generated alternatively.