DESC:FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)

Title: X-BAND TWO DIMENSIONAL ACTIVE ELECTRONIC SCANNED ANTENNA ARRAY WITH CALIBRATION LINES AND GUARD ANTENNA FOR AIRBORNE APPLICATION

APPLICANT DETAILS:
(a) NAME: BHARAT ELECTRONICS LIMITED
(b) NATIONALITY: Indian
(c) ADDRESS: OUTER RING ROAD, NAGAVARA, BANGALORE -560045,
KARNATAKA, INDIA

PREAMBLE TO THE DESCRIPTION:
The following specification (particularly) describes the nature of the invention (and the manner in which it is to be performed):

X-BAND TWO DIMENSIONAL ACTIVE ELECTRONIC SCANNED ANTENNA ARRAY WITH CALIBRATION LINES AND GUARD ANTENNA FOR AIRBORNE APPLICATION

FIELD OF INVENTION:
The present disclosure relates to communication technology. The disclosure, more particularly, relates to method and system for X-band two-dimensional active electronic scanned antenna array with calibration lines and guard antenna for airborne application.

BACKGROUND OF THE INVENTION:
The following background discussion includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication expressly or implicitly
In general, Microstrip Patch Antenna (MPA) is a suitable candidate for the realization of high gain and compact 64 element X-band array for airborne application. In general, two categories of feedings are used for the excitation of antenna array elements i.e. series feeding or corporate feeding, but these types of feedings are not suitable to achieve beam steering with side lobe level control (SLL). So, to achieve beam steering with controlled SLLs every element is excited individually by using separate Transmit Receive (Tx /Rx) modules.
Patch antenna performance greatly depends on height and, electrical characteristics of substrate as well as geometry of the patch. High permittivity substrate is required to make the design compact but it reduces the gain of the antenna while low permittivity substrate is preferred for enhancing the gain but it will increase the size of the antenna element as well as array. By increase the height of the substrate gain can be enhanced but it will make the design bulky as well as increase the cross polar level.
EP 3110048 A1 discloses A calibration network system for an array antenna and method for calibrating of the array antenna are descried. The system includes a pair of rectangular waveguides stacked in parallel relation to each other and spaced apart at a distance of a quarter of an operating wavelength. The rectangular waveguides includes through-holes extending through a side-wall of the stacked rectangular waveguides from a bottom of a lower waveguide to a top of an upper waveguide to accommodate coaxial transmission lines. The sidewall has openings between the through-holes and an interior region of the rectangular waveguides in order to provide coupling of the coaxial transmission lines into the pair of rectangular waveguides. The system includes 90 degree phase shifter coupled to the upper rectangular waveguide, and a power divider/combiner coupled to a reference T/R Module, to the 90 degree phase shifter and to the lower rectangular waveguide. Waveguides have been used as a calibration lines. This System will be complex and bulky. This type of phased array calibration network is not suitable at low frequency. So, in order to attain the desired bandwidth, and gain over the frequency band of operation an optimized height with medium permittivity substrate has to choose.
EP 3460907 B1 discloses an array antenna device is obtained which is capable of satisfactorily reducing mutual coupling between element antennas without inviting a significant increase in cost. A parallel line formed on the same plane as a patch element, close to the patch element, in a direction that is a magnetic field direction of a patch antenna and that is parallel to the polarization direction of the patch antenna, and a bent line shaped so as to be bent between adjacent patch elements and configured to connect their parallel lines to each other, form a coupling line, which couples part of an electromagnetic wave excited by one of the patch elements to its adjacent patch antenna, and, in the coupling line, a gap between the parallel line and the patch element and a length of the bent line are set so that an electromagnetic wave coupled from one patch antenna to its adjacent patch antenna via space and an electromagnetic wave coupled from the one patch antenna to the adjacent patch antenna via the coupling line cancel each other. Different shapes of coupling lines have been used between the adjacent elements of the antenna to improve the mutual coupling between the elements. It is improved ~ 5 dB over the frequency band of operation. Coupled lines will effect antenna array beam steering. Proposed coupling lines are used along both radiating and non-radiating edges. Coupling lines present along radiating edges will disturb the radiation pattern as well as reduce the gain of the antenna element and array due to high power coupling from the antenna.
WO 2013/045267 A1 discloses 2 D planar phase array antenna is proposed with inbuilt phase shifters for sub arrays realized by using variable dielectric material. Variable dielectric material used for the realization of phase shifter is voltage controlled liquid crystal. No discussion has happened on the Phase resolution limit of these type of phase shifters. As the number of elements are increasing in an array complex biasing network will be required. Liquid Crystal based phase shifters performance on movable platforms 5 is not discussed, that is very much required for defence applications. Dimensions of the Antenna w.r.t 10 GHz is ~ 200 mm x 200 mm with gain of 21 dBi.
Therefore, there is a need for an invention which provides a X-band two dimensional active electronic scanned antenna array with calibration lines and guard antenna for airborne application.

OBJECTIVES OF THE INVENTION:
The primary object of the present invention is to overcome the problem stated in the prior art.
Another object of the present invention is to provide a X-band two dimensional active electronic scanned antenna array with calibration lines and guard antenna for airborne application.

SUMMARY OF THE INVENTION:
The present invention provides a X-band two-dimensional active electronic scanned antenna array system comprising:
a) a guard antenna where the guard antenna received signal strength is greater than the side lobe level of array to quantify whether the received signal lies in the main beam or from side beams;
b) at least four calibration lines are combined by at least three numbers of 1:2 chip Wilkinson power divider; and
c) a patch antenna has rectangular shape is configured to work as a reference antenna to enhance the gain of the element;
wherein the impedance of calibration line is matched with power divider impedance by using section of a quarter wave transformers, where at least three numbers 1:2 wilkinson power divider chip is configured to perform as power divider for easy realization of phase matching between spatially separated calibration lines.
In an embodiment, the system for X-band antenna array having two-dimensional scanning capability with high impedance calibration lines, 1:2 power dividers and guard antenna with wide beam width radiating elements.
In an embodiment, the circuit of four high impedance calibration lines with one output port are used for the calibration of 64 antenna elements.
In an embodiment, the only one embedded calibration line checks all radiating elements of two columns and Tx / Rx modules health, where amount of power coupled from antenna to calibration lines or vice versa is controlled by impedance of calibration line and its separation from antenna.
In an embodiment, the high impedance micro strip line is configured to provide minimum required power coupling from the patches for calibration as well as it will also provide minimum distortion in pattern while steering.
In an embodiment, the high gain with pattern symmetry is achieved by a rectangular micro strip patch as a radiating element.
In an embodiment, the calibration line is implemented along the non-radiating edge of the patch to achieve minimum distortion in radiation pattern.
In an embodiment, the X-band antenna comprises (8 x 8) array with the guard antennas is made on 60 mil 6.15 dielectric permittivity substrate, where each antenna of the array is fed by coaxially, where the antenna array is supported by the back plate to give the strength to the structure with improved thermal stability.
In an embodiment, the X-band antenna array is comprised of 66 patches where 64 radiating patches are used to form a square patch array, and 2 patch radiators present in the design are used as a guard antenna.

DETAILED DESCRIPTION OF DRAWINGS:
To further clarify advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of their scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings in which:
Fig. 1: illustrates a top view of simulation model of patch antenna array.
Fig. 2: illustrates a back plate of the antenna array.
Fig. 3: illustrates VSWR vs. Frequency graph of the antenna array.
Fig. 4(a): illustrates 3D Radiation pattern of the antenna array.
Fig. 4(b): illustrates 2D polar plot for phi=0 plane of pattern @ f1 GHz of the antenna array.
Fig. 4(c): illustrates 2D polar plot for phi =90 plane of pattern @ f1 GHz of the antenna array.
Fig. 5(a): illustrates 3D Radiation pattern @ f0 GHz of the antenna array.
Fig. 5(b): illustrates 2D polar plot for phi =0 plane of pattern @ f0 GHz of the antenna array.
Fig. 5(c): illustrates 2D polar plot for phi =90 plate of pattern @ f0 GHz of the antenna array.
Fig. 6(a): illustrates 3D Radiation pattern @ f2 GHz of the antenna array.
Fig. 6(b): illustrates 2D polar plot for phi =0 plate of pattern @ f2 GHz of the antenna array.
Fig. 6(c): illustrates 2D polar plot for phi =90 plate of pattern @ f2 GHz of the antenna array,

DETAILED DESCRIPTION:
For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof.
The terms “comprises”, “comprising”, “includes”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, device or method that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or device or method. In other words, one or more elements in a system or apparatus proceeded by “comprises... a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or method.
In this design a separate guard antenna is also used. The gain of this guard antenna must be greater than the side lobe level of array to quantify whether the received signal lies in the main beam or from side beams.
In this design four calibration lines are used, these are commonly known as Cal lines. These lines are combined together by using three numbers of 1:2 chip Wilkinson power divider. These lines are used to test whether all the Transmit modules and antenna elements are working or not.
A square patch antenna is a suitable choice for achieving required symmetric beam pattern but here a rectangular shape patch antenna is taken as a reference antenna to enhance the gain of the element. The symmetry in the pattern is achieved due to the effect of array.
The impedance of calibration line is matched with power divider impedance by using section of quarter wave transformers. Three numbers of 1:2 Wilkinson Power Divider chip are used in place of one number of 1:4 Wilkinson Power Divider for easy realization of phase matching between spatially separated calibration lines. Direction of calibration line is selected along the non-radiating edge of the patch so that it will not affect the radiation pattern of the antenna.
Moderate Permittivity substrate (er = 6.15) with 60 mil thickness have been used to make the design compact and achieve the required BW, gain and isolation requirements. Mutual coupling between antenna elements is reduced by using optimized element size for a fixed spacing between the elements. Maximum coupling from antenna to coupled line is in the range of 40 dB and minimum coupling is in the range of 50 dB.
In one embodiment, a system for X-band antenna array having two dimensional scanning capability with high impedance calibration lines, 1:2 power dividers and guard antenna with wide beam width radiating elements.
In another embodiment, circuit of four high impedance calibration lines with one output port are used for the calibration of 64 antenna elements. Same technique can be extended for any number of antenna elements.
In another embodiment, three chip power dividers are used in place of PCB based planar circuit designs to make the compact phase matched calibration network circuitry for the implementation.
In an embodiment, only one embedded calibration line checks all radiating elements of two columns and Tx / Rx modules health. Amount of power coupled from antenna to calibration lines or vice versa is controlled by impedance of calibration line and its separation from antenna. A high impedance micro strip line is used for minimum required power coupling from the patches for calibration as well as it will also provide minimum distortion in pattern while steering. Line is terminated to 50 Ohm resistive load with quarter wave transformer.
In another embodiment, High gain with pattern beam symmetry is achieved by using rectangular micro strip patch as a radiating element in place of square patch to enhance the array gain and beam symmetry is achieved with the help of broad array effect. Achieved gain is higher than 22.5 dB over the frequency band of operation.
In another embodiment, two guard antennas were implemented to maintaining the symmetry of the pattern.
In another embodiment, calibration line is implemented along the Non-radiating edge of the patch to achieve minimum distortion in radiation pattern.
In another embodiment, scanning capability of proposed design is ± 40° in 2dimensional plane.
In an advantageous embodiment, Guided arrangements for blind mate engagement of multiple RF connector in array antenna system.
A compact X-band antenna (8 x 8) array with guard antennas is designed on 60 mil 6.15 dielectric permittivity substrate. Every antenna of the array is fed by coaxially. Antenna array is supported by the back plate to give the strength to the structure with improved thermal stability.
An X-band antenna array is comprised of 66 patches. 64 radiating patches are used to form a square patch array. 2 patch radiator present in the design are used as a guard antenna. To fulfil the impedance BW, gain, and beam width requirement in a compact size an optimized height and permittivity substrate is selected. To accommodate different type of tolerances i.e. variation in dielectric constant, fabrication tolerances etc. proposed design done for higher electrical specifications than the required value.
Antenna VSWR is < 1.4 over f1 - f2 i.e. ~ 500 MHz.
An innovative GNSS antenna is designed and developed for worldwide available GNSS frequency bands. Multiple techniques are used to realize broadband circular polarization with higher beam widths. Effects of radome and their position is optimized for required antenna performance over broadband. As a result, the proposed antenna finds use in any harsh environmental condition and fulfil requirement of different platforms.
Proposed antenna shows the following results-
VSWR Bandwidth – Result shows the achieved 1.4:1 VSWR bandwidth is 5 % of f0 shown Figure 3(a).
Peak gain of the antenna is > 22.5 dBi over the frequency band of operation.
Beam symmetry of the pattern in azimuth and elevation plane is within ± 0.15° over the desired frequency band of operation.
Figure 1 shows the antenna PCB top view and figure 2 shows the top view of bottom metallic plate. Complete structure is simulated using CST microwave studio. Antenna normalized frequency VSWR and 5 radiation pattern results.
Figure 3 shows VSWR vs. Frequency graph of the antenna array.
Figure 4 shows the 3 D radiation pattern and 2D polar plot at centre frequency f0 GHz. 0.3 ° beam width difference is observed due to patch shape asymmetry.
Figure 5 shows the 3 D radiation pattern and 2D polar plot at centre frequency f0 GHz. 0.1 ° beam width difference is observed due to patch shape asymmetry.
Figure 6 shows the 3 D radiation pattern and 2D polar plot at centre frequency f2 GHz. 0.1 ° beam width difference is observed due to patch shape asymmetry.
The foregoing description of the invention has been set merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the substance of the invention may occur to person skilled in the art, the invention should be construed to include everything within the scope of the invention.
,CLAIMS:We Claim:

1. A X-band two-dimensional active electronic scanned antenna array system comprising:
a) a guard antenna where the guard antenna received signal strength is greater than the side lobe level of array to quantify whether the received signal lies in the main beam or from side beams;
b) at least four calibration lines are combined by at least three numbers of 1:2 chip Wilkinson power divider; and
c) a patch antenna has rectangular shape is configured to work as a reference antenna to enhance the gain of the element;
wherein the impedance of calibration line is matched with power divider impedance by using section of a quarter wave transformers, where at least three numbers 1:2 wilkinson power divider chip is configured to perform as power divider for easy realization of phase matching between spatially separated calibration lines.
2. The X-band two-dimensional active electronic scanned antenna array as claimed in claim 1, wherein the system for X-band antenna array having two-dimensional scanning capability with high impedance calibration lines, 1:2 power dividers and guard antenna with wide beam width radiating elements.
3. The X-band two-dimensional active electronic scanned antenna array as claimed in claim 1, wherein circuit of four high impedance calibration lines with one output port are used for the calibration of 64 antenna elements.
4. The X-band two-dimensional active electronic scanned antenna array as claimed in claim 1, wherein only one embedded calibration line checks all radiating elements of two columns and Tx / Rx modules health, where amount of power coupled from antenna to calibration lines or vice versa is controlled by impedance of calibration line and its separation from antenna.
5. The X-band two-dimensional active electronic scanned antenna array as claimed in claim 1, wherein a high impedance micro strip line is configured to provide minimum required power coupling from the patches for calibration as well as it will also provide minimum distortion in pattern while steering.
6. The X-band two-dimensional active electronic scanned antenna array as claimed in claim 1, wherein a high gain with pattern beam symmetry is achieved by a rectangular micro strip patch as a radiating element.
7. The X-band two-dimensional active electronic scanned antenna array as claimed in claim 1, wherein the calibration line is implemented along the non-radiating edge of the patch to achieve minimum distortion in radiation pattern.
8. The X-band two-dimensional active electronic scanned antenna array as claimed in claim 1, wherein X-band antenna comprises (8 x 8) array with the guard antennas is made on 60 mil 6.15 dielectric permittivity substrate, where each antenna of the array is fed by coaxially, where the antenna array is supported by the back plate to give the strength to the structure with improved thermal stability.
9. The X-band two-dimensional active electronic scanned antenna array as claimed in claim 1, wherein the X-band antenna array is comprised of 66 patches where 64 radiating patches are used to form a square patch array, and 2 patch radiators present in the design are used as a guard antenna.