TECHNICAL FIELD
The present invention generally relates to a broadband antenna system, more particularly to a dual polarized antenna system for radars and satellite communication.
BACKGROUND
Modern Radars such as polarimetric synthetic aperture radar (SAR) have polarization agility as one of important requirement along with high resolution and high frequency operation. A Dual-polarization is a critical parameter required to achieve polarization agility. A Broadband feature is required to achieve high resolution.
Communication systems especially satellite communication on the other hand has high speed and high data rate as one of the requirements. The dual polarization is required for satellite reception as polarization depends on position of satellite and latitude and longitude of the receiver.
Full duplex communication systems will require the antenna system to cover both Tx and Rx frequency range. The solution for such applications could be an antenna which will have dual band response or a broadband antenna covering both Tx and Rx frequencies.
Many applications from the field of radar and communication will require mobility where the systems are placed on vehicles, tanks etc. For such applications low profile and compactness is essential. And many applications from

the field of radar and communication will be for mass consumer market where ease of fabrication is one of the critical requirements.
[0006] Antenna being critical component of such systems, features like dual
polarization, broadband width, high efficiency, low profile, high frequency operation and ease of fabrication will be required.
[0007] There are several research works focusing on various antenna
technologies with the above discussed features.
[0008] One of the prior arts discloses a printed technologies like micro-strip
antenna with dual polarized feature. This prior art has ease of routing of feeding network along with low profile makes such antenna technologies attractive. But limited power handling, low efficiency due to dielectric loss at high frequency operation and excitation of surface waves limits their capacities.
[0009] Another prior art discloses a waveguide slot antenna technology with
dual polarization features. This prior art provide high efficiency and high gain. But limited bandwidth due to slot element and adoption of series type feeding limits their capabilities. Moreover, fabrication tolerances of such antenna technologies become very high at high frequency of operation.
[0010] Further prior art discloses an open ended waveguide and Horns for
dual polarization. This prior art provide broader bandwidth compared to slot antenna due to corporate type of feeding arrangement and high efficiency. But bandwidth achieved by such technologies is limited due to cavity coupling which is used to simplify corporate feed network.

[0011] Further prior art discloses a waveguide architecture which uses
horns along with septum polarizer for low profile and dual polarization capability.
[0012] Therefore, there is a need in the art with a dual polarized antenna
system for radars and satellite communication and to solve the above mentioned limitations.
SUMMARY OF THE INVENTION
[0013] An aspect of the present invention is to address at least the above-
mentioned problems and/or disadvantages and to provide at least the advantages described below.
[0014] Accordingly, in one aspect of the present invention relates to a dual
polarized antenna for radar and communication system, the antenna comprising: a radiating unit (100) configured to transmit/receive an electromagnetic energy of two orthogonal polarizations, a polarization discriminating unit (200) coupled to the radiating unit (100) to receive/transmit the electromagnetic energy of two orthogonal polarizations and configured to separate the two polarizations with a high level of isolation over a broad band of frequencies at two separate inlets/outlets and a feed network unit (300) coupled to the polarization discriminating unit (200) and configured to combine/split the electromagnetic energy of two orthogonal polarization from/to the polarization discriminating unit 200, said feed network unit (300) houses two separate feed network modules, where one feed network module (300A) with inlet/outlet processes first state of polarization i.e. vertical polarization (V) and second feed network module (300B) with inlet/outlet processes the second state of polarization i.e. horizontal polarization (H).

[0015] Other aspects, advantages, and salient features of the invention will
become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
[0016] The detailed description is described with reference to the
accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and modules.
[0017] Figure 1 shows major functional units of an antenna system
according to an exemplary implementation of the present disclosure/invention.
[0018] Figure 2 shows a radiating unit 100 and polarization discriminating
unit 200 of an antenna system according to an exemplary implementation of the present disclosure/invention.
[0019] Figure 3 shows an example element of an array according to an
exemplary implementation of the present disclosure/invention.
[0020] Figure 4 shows a feed network unit 300 which will process the two
polarizations separately according to an exemplary implementation of the present disclosure/invention.
[0021] Figure 5 shows an example current flow in a rectangular waveguide
according to an exemplary implementation of the present disclosure/invention.

[0022] Figure 6 shows an assembly of dual polarized antenna system 400
using four layers according to an exemplary implementation of the present disclosure/invention.
[0023] Figure 7-10 illustrates an example results of the electromagnetic
performances of an example antenna system according to an exemplary implementation of the present disclosure/invention.
[0024] Figure 7 illustrates an example of return loss and isolation for the
antenna array according to an exemplary implementation of the present disclosure/invention.
[0025] Figure 8 illustrates an example patterns at frequency F1 which may
be the lowest frequency of operation according to an exemplary implementation of the present disclosure/invention.
[0026] Figure 9 illustrates an example patterns at frequency F2 which may
be the middle frequency of operation according to an exemplary implementation of the present disclosure/invention.
[0027] Figure 10 illustrates an example patterns at frequency F3 which may
be the highest frequency of operation according to an exemplary implementation of the present disclosure/invention.
[0028] It should be appreciated by those skilled in the art that any block
diagrams herein represent conceptual views of illustrative methods embodying the principles of the present disclosure. Similarly, it will be appreciated that any flow charts, flow diagrams, and the like represent various processes which may be substantially represented in computer readable medium and so executed by a

computer or processor, whether or not such computer or processor is explicitly shown.
DETAILED DESCRIPTION
[0029] The following description with reference to the accompanying
drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
[0030] The terms and words used in the following description and claims are
not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
[0031] It is to be understood that the singular forms “a,” “an,” and “the” include
plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” includes reference to one or more of such surfaces.

[0032] By the term “substantially” it is meant that the recited characteristic,
parameter, or value need not be achieved exactly, but that deviations or variations,
including for example, tolerances, measurement error, measurement accuracy
limitations and other factors known to those of skill in the art, may occur in amounts
that do not preclude the effect the characteristic was intended to provide.
[0033] Figures discussed below, and the various embodiments used to
describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way that would limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged communications system. The terms used to describe various embodiments are exemplary. It should be understood that these are provided to merely aid the understanding of the description, and that their use and definitions in no way limit the scope of the invention. Terms first, second, and the like are used to differentiate between objects having the same terminology and are in no way intended to represent a chronological order, unless where explicitly stated otherwise. A set is defined as a non-empty set including at least one element.
[0034] In the following description, for purpose of explanation, specific
details are set forth in order to provide an understanding of the present disclosure. It will be apparent, however, to one skilled in the art that the present disclosure may be practiced without these details. One skilled in the art will recognize that embodiments of the present disclosure, some of which are described below, may be incorporated into a number of systems.
[0035] However, the systems and methods are not limited to the specific
embodiments described herein. Further, structures and devices shown in the

figures are illustrative of exemplary embodiments of the presently disclosure and are meant to avoid obscuring of the presently disclosure.
[0036] The various embodiments of the present invention describe about
dual polarized antenna system for radars and satellite communication. The present invention proposed an antenna system with dual polarization, high efficiency, low profile, low cost manufacturing and high frequency of operation capability.
[0037] In one embodiment, the present invention discloses an antenna
system with a broad bandwidth (> 30 %). Such a bandwidth will be required for full duplex communication system. One example could be Ku band SATCOM which has Rx band from 10.9GHz-12.75GHz and Tx band from 13.75GHz-14.5GHz. So, for full duplex communication in the above band close to 30% bandwidth is expected from the antenna system. For application such as radars bandwidth requirement may go close the 20-30% in the future. Apart from bandwidth the present invention proposed an antenna system with dual polarization, high efficiency, low profile, low cost manufacturing and high frequency of operation capability.
[0038] In one embodiment, the present invention provides an antenna
system which is capable of broadband operation with dual polarization, high efficiency, high gain and low profile.
[0039] In one embodiment, broadband capability stems from the novel
polarization discriminating structure, use of E plane feed network and also use of stepped waveguide radiating element.

[0040] In one embodiment, reduced height waveguides were used in
routing the feeding layers which eased the fabrication complexity.
[0041] In one embodiment, composite radiation mechanism ensures
grating lobe free operation along with ease in routing feeding guides.
[0042] In one embodiment, disclosed antenna can be formed in a four layer
assembly avoiding the stringent requirement of bonding.
[0043] In one embodiment, the Broadband Antenna with Dual polarization
capability for communication and radar system is disclosed. The Antenna system consists of Dual Polarization Radiating unit, Polarization discriminating unit and the Feed Network unit. The Radiating unit is a composite structure with grid array fed by a broadband stepped waveguide. Signals received from the radiation unit are dual polarized in nature which is passed through the broadband polarization discriminating unit to generate two separate polarizations. The first polarization is fed to a first polarization feeding network. The second polarization which is orthogonal to the first polarization is fed to a second polarization feeding network.
[0044] The whole antenna apparatus of the present invention can be
formed by four layer assembly without any stringent requirement of bonding between them.
[0045] In one embodiment, the present invention relates to a Broadband
antenna system for modern radar and communication system comprising of three functional units - Dual Polarization Radiating unit, Polarization discriminating unit and Feed network unit.

[0046] In one embodiment, the dual polarization radiating unit is composed
of a grid array fed by stepped waveguide structure.
[0047] In one embodiment, the polarization discriminating unit
receives/transmits dual polarized electromagnetic energy and separates the two polarizations with a high level of isolation over a broad band of frequencies at two separate inlets/outlets.
[0048] In one embodiment, one sub-array unit is formed by integrating the
said dual polarization radiating unit and the said polarization discriminating unit.
[0049] In one embodiment, plurality of the said sub-array unit is used to
form the antenna array system which has two inlets/outlets i.e. of the polarization discriminating units. One inlet/outlet provides for first state of polarization whereas the second inlet/outlet provide for the second state of polarization which is orthogonal to the first state of polarization.
[0050] In one embodiment, plurality of the said inlets/outlets for each
polarization are combined/split by the Feed network unit.
[0051] In one embodiment, the Feed network unit houses two separate feed
network units. One feed network unit processes first state of polarization whereas second feed network unit processed the second state of polarization.
[0052] In one embodiment, the grid array consists of four radiating elements
along with matching elements and the stepped waveguide structure consists of an optimum number of steps.
[0053] In one embodiment, the polarization discriminating unit consists of
three inlets/outlets-first one for transmit/receive the dual polarized electromagnetic

energy, second one for isolated first state of polarization and third one for isolated second state of polarization which is orthogonal to the first state of polarization.
[0054] In one embodiment, the polarization discriminating unit is an
asymmetric structure with a scheme of reducing dimensions in a plane opposite to the inlet/outlet for one polarization and increasing dimension post that ensuring a broadband impedance match.
[0055] In one embodiment, the polarization discriminating unit has an
optimum distance between the two inlets/outlets for ensuring better electromagnetic performances.
[0056] In one embodiment, the feed network units combine/split in E plane
with reduced height waveguides.
[0057] In one embodiment, the antenna may be formed in a four layer
assembly wherein first layer houses the grid array, second layer houses the stepped waveguide and upper half of plurality of polarization discriminating unit and the first feed network unit i.e. from the dual polarized inlet/outlets to upper section of the inlet/outlet of one polarization along with upper section of first feed network, third layer houses middle half of plurality of polarization discriminating unit and the first feed network unit and second feed network unit i.e. from lower section of the inlet/outlet of one polarization along with lower section of first feed network to the upper section of the inlet/outlet of second polarization along with upper section of second feed network and fourth layer houses lower half of plurality of polarization discriminating unit and the second feed network unit i.e. from lower section of the inlet/outlet of second polarization along with lower section of second feed network.

[0058] Figure 1 shows major functional units of an antenna system
according to an exemplary implementation of the present disclosure/invention.
[0059] The figure shows a major functional unit of an antenna system. The
antenna system comprises of three major functional units i.e. radiating unit 100, polarization discriminating unit 200 and Feed network unit 300.
[0060] In one embodiment, the present invention discloses a dual polarized
antenna for radar and communication system, the antenna comprising: a radiating unit (100) configured to transmit/receive an electromagnetic energy of two orthogonal polarizations, a polarization discriminating unit (200) coupled to the radiating unit (100) to receive/transmit the electromagnetic energy of two orthogonal polarizations and configured to separate the two polarizations with a high level of isolation over a broad band of frequencies at two separate inlets/outlets and a feed network unit (300) coupled to the polarization discriminating unit (200) and configured to combine/split the electromagnetic energy of two orthogonal polarization from/to the polarization discriminating unit 200, said feed network unit (300) houses two separate feed network modules, where one feed network module (300A) with inlet/outlet processes first state of polarization i.e. vertical polarization (V) and second feed network module (300B) with inlet/outlet processes the second state of polarization i.e. horizontal polarization (H).
[0061] The radiating unit is a composed of a grid array which in turn is fed
by a stepped waveguide structure. The radiating unit can transmit or receive electromagnetic energy of two orthogonal polarizations. In receive mode, the polarization discriminating unit 200 receives dual orthogonal polarization and

provides two separate outputs which are fed to the feeding unit. The device i.e. polarization discriminating unit 200 also provides a high level of isolation between the two polarizations.
[0062] In transmit mode, the polarization discriminating unit 200 takes two
polarizations from the two separate feed network units 300 and provide a dual polarized output to the radiating unit 100. The radiating unit 100 and the polarization discriminating unit 200 forms one sub-array unit as shown in figure 2. One sub-array unit houses radiating aperture on one side and two separate orthogonal polarizations on the other side. Plurality of such sub-arrays can be formed which is passed to the next functional unit i.e. Feed Network unit 300. This network unit 300 houses two levels of feed network for carrying orthogonal polarizations.
[0063] One of the purposes of the present invention is to broaden the
bandwidth of the antenna system which in essence means that each of the functional units 100, 200 and 300 as discussed above should be able to operate on the broad bandwidth that is targeted.
[0064] Another purpose of the present invention is to provide a high
efficiency which was achieved by using a full metal structure i.e. by using waveguides which has the lowest loss among the known transmission mediums.
[0065] The figure 2-4 elaborates in detail about the working of the major
functional units i.e. radiating unit 100, polarization discriminating unit 200 and feed network unit 300.

[0066] Figure 2 shows a radiating unit 100 and polarization discriminating
unit 200 of an antenna system according to an exemplary implementation of the present disclosure/invention.
[0067] The figure shows a radiating unit 100 and polarization discriminating
unit 200 of an antenna system. In one embodiment, the radiating unit (100) is a dual polarization radiating unit composed of a grid array unit 110 and a stepped waveguide structure 120 to transmit and receive electromagnetic energy of two orthogonal polarizations. The grid array unit 110 of the radiating unit 100 comprises atleast four identical radiating elements 111 and atleast one matching elements 112 and 113. The grid array elements form the interface between the stepped waveguide structure 120 and free space. The stepped waveguide 120 of the radiating unit 100 has two opening faces 121 and 122, where the first face 121 is wider one which acts as a feed for the grid array unit 110 and the second face 122 acts as a feed for the polarization discriminating unit 200. The radiating unit 100 and the polarization discriminating unit 200 forms one sub-array unit, where the face 122 of the radiating unit 100 is coupled with the face 210 of the polarization discriminating unit 200. The polarization discriminating unit 200, in receive mode, receives two orthogonal polarization from the radiating unit 100 and provides two separate outputs which are fed to the feed network unit (300) and in transmit mode, the polarization discriminating unit takes two polarizations from the two separate feed network modules (300A and 300B) and provide the two polarized output to the radiating unit 100.
[0068] The polarization discriminating unit 200 is a four port device
comprising atleast three sections, said three sections being a square waveguide

section 210, a first section 220 and a second section 230, where the square waveguide section 210 forms the inlet/outlet to transmit/ receive the dual polarized electromagnetic energy, the first section 220 forms the inlet/outlet for first polarization and the second section 230 forms the inlet/outlet for the second polarization which is orthogonal to the first polarization. The first and second section 220 and 230 is to guide the isolated orthogonal polarizations with high efficiency to the feed network unit 300.
[0069] The polarization discriminating unit 200 is an asymmetric structure
and further comprises a stepped structure 240 which is provided on the opposite face of the section 220 in order to get sufficient gain and bandwidth from the radiating unit and also provides broad band and smooth transition. The stepped structure 240 reduces the dimensions of the waveguide in one plane and section 250 increases the dimensions via steps in another plane.
[0070] The polarization discriminating unit 200 further comprises a physical
separation (D1) between the two sections which is an optimum distance between the two inlets/outlets of 220 and 230 leading to broader bandwidth along with high isolation.
[0071] The figure 2 shows a radiating unit 100 and polarization
discriminating unit 200 of an antenna system. The Radiating unit is composed of two sub-units-Grid array 110 and stepped waveguide 120. The grid array consists of four identical radiating elements 111. These radiating elements are square hollow metal structures with dual polarization capability. The grid arrays form the interface between the stepped waveguide structure 120 and free space. To

achieve broad band operation, the grid array is embedded with matching elements 112 and 113.
[0072] The stepped waveguide 120 forms the next sub-unit. It has two
opening faces 121 and 122. The face 121 is wider one which acts as a feed for the grid array unit 110. The face 122 acts as a feed for the polarization discriminating unit 200. The face 122 can be one end of a square waveguide. The dimensions of the square waveguide may be selected based on the desired frequency of operation. The dimensions are being selected in a way that ensures propagation of only two orthogonal modes in the targeted frequency range. These two modes are aligned with the two polarizations states of the inventive antenna. To get sufficient gain and bandwidth from the radiating unit, steps are introduced to provide a broad band and smooth transition. As can be seen from figure 2 there are three steps from 122 to 121. It is to be noted that increasing the number of steps will further improve the bandwidth of operating but will lead to a higher profile. In a similar fashion to get a low profile structure fewer steps may be used but with compromised bandwidth. Therefore, an optimum number of steps (three) were used in this present invention to achieve a broad bandwidth close to 30%.
[0073] The stepped waveguide 120 may also be used as the sole radiating
unit without the grid array 110. Such a radiating unit may be used as a feeder for a reflector antenna. But when the same is used as an element of an array as shown in figure 3 for achieving desired high gain the spacing between these elements (S1) becomes greater than the free-space wavelength. This will lead to generation of grating lobes which will reduce the efficiency of the antenna system. Here the utility of the grid array 110 may be understood. The spacing between

elements of the grid array (S2) will be in order of sub-wavelength. Hence one of the purposes i.e. grating lobe free operation is achieved by the composite radiating unit 100.
[0074] The Grid array 110 with some modification can also be used as the
sole radiator without the stepped waveguide 120. Grating lobe free operation can be achieved by such a scheme. In order to have feed the radiating elements 111, four polarization discriminating units are required. The routing in the feed network unit will be difficult in waveguide or full metal solution in such a scenario. There is a need to resort to printed feed network like micro-strip, strip-line etc. for routing. The purpose of providing high efficiency will be compromised in such a scheme as printed medium will introduce dielectric losses among other losses. Therefore, the radiation unit 100 in the current inventive antenna can serve the purpose of grating lobe free operation along with high efficiency and broad-bandwidth.
[0075] The purpose of Polarization discriminating unit 200 in receive mode
is to separate the two polarizations with high isolation from the dual polarized electromagnetic energy captured by the radiating unit. The purpose of this unit in transmit mode is to combine the two polarization and generate a dual polarized electromagnetic signal. The polarization discriminating unit 200 is a four port device with three sections 210, 220 and 230. The two polarizations will be present at the square waveguide section 210. First polarization will be considered as first port and the second polarization will be considered as the second port. Therefore, both the orthogonal polarizations will be present at the square waveguide section 210. The section 220 forms the inlet/outlet of first polarization. Similarly, section 230 forms the inlet/outlet of the second polarization which is orthogonal to the first

polarization. Metal rectangular waveguides forms the section 220 and 230. Dimensions of such rectangular waveguides may be selected based on the mono-mode operation in the desired frequency range. Reduced height waveguide is used here which are known to have less susceptibility to higher order mode generation.
[0076] The purpose of the sections 220 and 230 is to guide the isolated
orthogonal polarizations (ensured by the polarization discriminating unit 200) with high efficiency to the next functional unit 300. Efficiency may get compromised by presence of undesired modes in the section 220 and 230. Reduced height waveguide and proper dimension selection of section 220 and 230 will ensure mono-mode operation and thereby high efficiency transmission.
[0077] The polarization discriminating unit 200 should be having broad
bandwidth of operation, high isolation between the orthogonal polarizations and compact enough to ensure use in array formation. It should have the above mentioned electromagnetic features along with a low profile. To achieve broadband of operation (>30 %) and high isolation symmetrical structures were generally preferred. Asymmetric structures are low in bandwidth due to generation of higher order modes. Symmetric structure requires mirror sections like 220 which will be further recombined using a power combiner to provide a single output. Such structures will lead to non-compactness and fabrication complexity. Therefore, keeping in mind, the purpose of use of polarization discriminating structure 200 in an array, an asymmetric structure is used for the current invention antenna. To reduce the generation of higher order mode and bandwidth improvement a stepped structure 240 is used on the opposite face of the section 220. The stepped

structure reduces one side of the square waveguide and gradually comes to the dimensions of rectangular waveguide 230. The stepped structure on the opposite face ensures delinking of the two polarization discriminating function. As can be seen from figure 4 section 240 reduces the dimensions of the waveguide in one plane and section 250 increases the dimensions via steps in another plane. This scheme of reducing and increasing dimensions facilitates broader impedance match without generation of higher order mode. The physical separation between the two sections 220 and 230 i.e. D1 is an important parameter which need to be carefully chosen. Increasing of D1 leads to broader bandwidth along with high isolation but with increased profile. Decreasing D1 leads to narrow bandwidth along with less isolation but with a low profile. Therefore, an optimum D1 is chosen which ensures meeting the desired bandwidth requirement. Section 260 performs the job of broadband bending of the second polarization. This will help routing the network unit 300 on the same layers as that of section 230 thereby low profile is ensured.
[0078] Sub-array unit is formed by integrating radiating unit 100 with
polarization discriminating unit 200. The face 122 of the radiating unit 100 (Figure 2) is attached with the face 210 of the polarization discriminating unit 200. During the design process of the functional unit 100 and 200 broadband operating of each unit was verified. There may a need of an integrated optimization to further improve the electromagnetic performances. Plurality of such sub-array unit is used to form the array. Each such unit housed four radiating apertures. An array of M x N element can be formed where M is the number of elements in one plane and N is the number of elements in the orthogonal plane. M and N are decided based on

the gain, beam-width and the mechanical profile required from the antenna. A typical example could be Satellite communication on moving vehicle where vertical plane should house fewer elements as more elements will increase the height of antenna and thereby compromising low profile feature. For M x N array there should be M/2 x N/2 sub-array units in the respective planes. For example, to get 16 x 8 antenna array one needs 8 x 4 sub-array units. Each sub-array unit houses two outlets/inlets which receive/transmit the two polarizations. Plurality of sub-array units will therefore house plurality of outlets/inlets which receives/transmits the two polarizations i.e. the dual polarization. The next job is to process these two separate highly isolated orthogonal polarizations from the plurality of inlets/ outlets. There will be two layers of inlets/outlets. First layer will be containing plurality of 220 sections which will process one polarization. Second layer will be containing plurality 230 sections which will process second polarization.
[0079] Figure 4 shows a feed network unit 300 which will process the two
polarizations separately according to an exemplary implementation of the present disclosure/invention.
[0080] The figure shows the feed network unit 300 which will process the
two polarizations separately. Plurality of 220 sections will be combining / splitting as per the scheme 300A. Plurality of 230 sections will be combining / splitting as per the scheme 300B. It is to be noted that for combining /splitting, a corporate feeding scheme is adapted which provides a broad band of operation. There are two ways in which power can be combined in a waveguide medium – H plane and E plane. In case of H plane, routing will be done along the broadside of rectangular waveguide whereas in case of E plane routing will be done along the narrow side

of rectangular waveguide. Therefore, E plane power combining/splitting will lead to a more compact and simpler corporate feeding network scheme. Another advantage of use of E plane guide is ease of fabrication. For Fabrication using CNC process split parts are used which are later joined by some bonding process like bolts, epoxy or brazing.
[0081] Figure 5 shows an example current flow in a rectangular waveguide
according to an exemplary implementation of the present disclosure/invention.
[0082] The figure shows an example current flow in a rectangular
waveguide. As seen from figure, the current flow in a rectangular waveguide are disturbed minimally, only if the guide is split along C1 i.e. in E plane which means stringent requirement of connectivity (bonding) will not be there. E plane waveguide corporate feeding network is therefore chosen which provides ease of routing the feed network and ease of fabrication. The feed network unit 300 therefore will combine/split the two polarizations from/to the polarization discriminating unit 200 as per 300A and 300B and provide one inlet/outlet for one polarization i.e. Vertical polarization (V) and another inlet/outlet for the orthogonal polarization i.e. Horizontal polarization (H).
[0083] Figure 6 shows an assembly of dual polarized antenna system 400
using four layers according to an exemplary implementation of the present disclosure/invention.
[0084] The figure shows the assembly of dual polarized antenna system
400 using four layers. The four layers 410, 420, 430 and 440 are separately manufactured using any conductive material like Aluminum. Post manufacturing of the plates they may undergo high conductive plating like silver to improve the

conductivity and thereby increasing efficiency. The first plate 410 houses the grid array 110.The second plate 420 houses the stepped waveguide 120 and upper half of 220. The third plate 430 houses of the lower half of 220 and upper half of 230. The fourth plate houses the lower half of 230. The plates 420, 430 and 440 are split as per the principle enumerated in Figure 5. Therefore, there will be no requirement of strict bonding among them. The plate 410 may need proper connectivity with plate 420 which can be ensured by bolts. It must be noted that bonding between inner layer like 420 and 430 will lead to fabrication complexity. The present antenna system therefore has an advantage in terms of ease of fabrication as it relaxed the bonding criteria between inner layers. The orthogonal dual polarized inlet/outlet can be accessed by standard waveguide adapters based on the frequency of operation at the V and H section. V section will provide one polarization whereas the H section will provide the second polarization.
[0085] In one embodiment, the present invention relates to dual polarized
antenna comprises four layer assembly wherein: a first layer 410 houses the grid array (110), a second layer 420 houses the stepped waveguide (120) and upper half of polarization discriminating unit (200) and the first feed network unit (300A), i.e. from the dual polarized inlet/outlets to upper section of the inlet/outlet of one polarization (220) along with upper section of first feed network module (300A), a third layer 430 houses middle half of polarization discriminating unit (200) and the first feed network module (300A) and second feed network module (300B) i.e. from lower section of the inlet/outlet of one polarization (220) along with lower section of first feed network module (300A) to the upper section of the inlet/outlet of second polarization (230) along with upper section of second feed network

module (300B) and a fourth layer 440 houses lower half of plurality of polarization discriminating unit (200) and the second feed network unit (300B) i.e. from lower section of the inlet/outlet of second polarization (230) along with lower section of second feed network (300B).
[0086] Figure 7-10 illustrates the results of the electromagnetic
performances of an example antenna system. A 16x 8 antenna array is used to evaluate the performance features.
[0087] Figure 7 illustrates an example of return loss and isolation for the
antenna array according to an exemplary implementation of the present disclosure/invention.
[0088] The figure illustrates the return loss and isolation for the antenna
array. The return loss basically shows how much energy is reflected back at the orthogonal dual polarized inlet/outlet V and H. The graph also shows the isolation figures for the antenna array. This isolation is among the two polarizations i.e. V and H. In this example return loss for the two orthogonal ports are below -10 dB from 10.75GHz to 14.66 GHz covering a bandwidth greater than 30%. The isolation figure shows a worst case isolation of -55.32 dB which ensures that the antenna system provides a highly isolated dual polarized signal over a broad bandwidth.
[0089] Figure 8 illustrates an example patterns at frequency F1 which may
be the lowest frequency of operation according to an exemplary implementation of the present disclosure/invention.

[0090] Figure 9 illustrates an example patterns at frequency F2 which may
be the middle frequency of operation according to an exemplary implementation of the present disclosure/invention.
[0091] Figure 10 illustrates an example patterns at frequency F3 which may
be the highest frequency of operation according to an exemplary implementation of the present disclosure/invention.
[0092] The figures 8-10 illustrates the gain pattern at three frequencies-F1,
F2 and F3. The gain pattern shows both co and cross polarizations at two planes Phi=0º and Phi=90º. Figure 8 illustrates the patterns at frequency F1 which may be the lowest frequency of operation. In this example case it is at 10.75GHz. Figure 9 illustrates the patterns at frequency F2 which may be the middle frequency of operation. In this example case it is at 12.7GHz. Figure 10 illustrates the patterns at frequency F3 which may be the highest frequency of operation. In this example case it is at 14.66 GHz. As can be seen from the graphs the gain pattern is quite stable throughout the frequency range of operation. It may be noticed that the beam-width in one plane is more than the other as more elements are present in that plane. The cross polarization levels are quite low which could explain the high isolation figures.
[0093] Figures are merely representational and are not drawn to scale.
Certain portions thereof may be exaggerated, while others may be minimized. Figures illustrate various embodiments of the invention that can be understood and appropriately carried out by those of ordinary skill in the art.
[0094] In the foregoing detailed description of embodiments of the invention,
various features are grouped together in a single embodiment for the purpose of

streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments of the invention require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus, the following claims are hereby incorporated into the detailed description of embodiments of the invention, with each claim standing on its own as a separate embodiment.
[0095] It is understood that the above description is intended to be illustrative,
and not restrictive. It is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined in the appended claims. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein,” respectively.

We Claim:
1. A dual polarized antenna for radar and communication system, the antenna
comprising:
a radiating unit (100) configured to transmit/receive an electromagnetic energy of two orthogonal polarizations;
a polarization discriminating unit (200) coupled to the radiating unit (100) to receive/transmit the electromagnetic energy of two orthogonal polarizations and configured to separate the two polarizations with a high level of isolation over a broad band of frequencies at two separate inlets/outlets; and
a feed network unit (300) coupled to the polarization discriminating unit (200) and configured to combine/split the electromagnetic energy of two orthogonal polarization from/to the polarization discriminating unit 200, said feed network unit (300) houses two separate feed network modules, where one feed network module (300A) with inlet/outlet processes first state of polarization i.e. vertical polarization (V) and second feed network module (300B) with inlet/outlet processes the second state of polarization i.e. horizontal polarization (H).
2. The antenna as claimed in claim 1, wherein the radiating unit (100) is a dual polarization radiating unit composed of a grid array unit 110 having atleast four identical radiating elements with at least one matching elements 112, 113 and a stepped waveguide structure 120 consisting of optimum number of steps to transmit and receive electromagnetic energy of two orthogonal polarizations.
3. The antenna as claimed in claim 1, wherein the radiating unit 100 and the polarization discriminating unit 200 forms one sub-array unit, where the face 122 of the radiating unit 100 is coupled with the face 210 of the polarization discriminating unit 200.

4. The antenna as claimed in claim 1, wherein the polarization discriminating unit 200, in receive mode, receives two orthogonal polarization from the radiating unit 100 and provides two separate outputs which are fed to the feed network unit (300) and in transmit mode, the polarization discriminating unit takes two polarizations from the two separate feed network modules (300A and 300B) and provide the two polarized outputs to the radiating unit 100.
5. The antenna as claimed in claim 1, wherein the polarization discriminating unit 200 is a four port device comprising atleast three sections, said three sections being a square waveguide section 210, a first section 220 and a second section 230, where the square waveguide section 210 forms the inlet/outlet to transmit/ receive the dual polarized electromagnetic energy, the first section 220 forms the inlet/outlet for first polarization and the second section 230 forms the inlet/outlet for the second polarization which is orthogonal to the first polarization, where the first and second section 220 and 230 is to guide the isolated orthogonal polarizations with high efficiency to the feed network unit 300.
6. The antenna as claimed in claim 1 and 5, wherein the polarization discriminating unit 200 is an asymmetric structure and further comprises a stepped structure 240 which is provided on the opposite face of the section 220 in order to get sufficient gain and bandwidth from the radiating unit and also provides broad band and smooth transition.
7. The antenna as claimed in claim 6, wherein the stepped structure 240 reduces the dimensions of the waveguide in one plane and section 250 increases the dimensions via steps in another plane.
8. The antenna as claimed in claim 1, wherein the polarization discriminating unit 200 further comprises a physical separation (D1) between the two sections

which is an optimum distance between the two inlets/outlets of 220 and 230 leading to broader bandwidth along with high isolation.
9. The antenna as claimed in claim 1 to 8, wherein the dual polarized antenna comprises four layer assembly wherein:
a first layer 410 houses the grid array (110);
a second layer 420 houses the stepped waveguide (120) and upper half of polarization discriminating unit (200) and the first feed network unit (300A), i.e. from the dual polarized inlet/outlets to upper section of the inlet/outlet of one polarization (220) along with upper section of first feed network module (300A);
a third layer 430 houses middle half of polarization discriminating unit (200) and the first feed network module (300A) and second feed network module (300B) i.e. from lower section of the inlet/outlet of one polarization (220) along with lower section of first feed network module (300A) to the upper section of the inlet/outlet of second polarization (230) along with upper section of second feed network module (300B); and
a fourth layer 440 houses lower half of plurality of polarization discriminating unit (200) and the second feed network unit (300B) i.e. from lower section of the inlet/outlet of second polarization (230) along with lower section of second feed network (300B).