Claims:
1. A trans-receive antenna for a radar system, the trans-receive antenna comprising of:
at least one transmit antenna (10) configured to transmit electromagnetic signals, wherein the transmit antenna (10) comprises at least one transmit beam constraining layer (11), at least one radiating aperture layer (12) and at least one feed layer type 1 (13), wherein the radiating aperture layer (12) is configured in conjunction with the transmit beam constraining layer (11) and feed layer type 1 (13) to form the transmit antenna;
at least one receive antenna (20) configured to receive electromagnetic signals, wherein the receive antenna (20) comprises at least one radiating aperture layer (12), at least one feed layer type 1 (13), at least one feed layer type 2 (23) and at least one Interface layer (24), wherein the radiating aperture layer (12) is configured in conjunction with the feed layer type 1 (13), feed layer type 2 (23) along with the interface layer (24) to form the receive antenna; and
at least one isolation structure (30) configured in-between the at least one transmit antenna (10) and at least one receive antenna (20) to achieve high isolation between the two antennas for facilitating simultaneous transmission and reception.

2. The antenna as claimed in claim 1, wherein the radiating aperture layer (12) of the transmit antenna (10) and the receive antenna (20) comprises a plurality of couplets (60) to form the radiating aperture layer (12), where each couplet (60) comprises a feeding chamber (9), a radiation chamber (6), a plurality of symmetric steps (5), asymmetric steps (4) and a partition wall (7).
3. The antenna as claimed in claim 1, wherein the couplet (60) is a three port device comprises at least one inlet (1) and at least two outlets (2 and 3) in case where the couplet (60) is used as a radiator for transmission of electromagnetic signals and the couplet (60) comprises at least two inlets and at least one outlet in case where the couplet (60) is used as a radiator for reception of electromagnetic signals.

4. The antenna as claimed in claim 1, wherein during transmission, the electromagnetic signals are fed from inlet (1) of the couplet (60) and the electromagnetic energy travels through a window W to enter the radiation chamber (6).

5. The antenna as claimed in claim 1, wherein a broad wall dimension ‘G’ of the couplet (60) is selected based on mode of the electromagnetic signal propagating over the desired frequency of operation, a narrow wall height ‘H’ is determined based on the aperture impedance match and the window ‘W’ is configured to control the amount of electromagnetic signal energy flow to/from feeding chamber (9) from/to radiation chamber (6).

6. The antenna as claimed in claim 1, wherein the groove (4) (the asymmetric step) and the groove (5) (the symmetric step) are configured to ensure smooth transition of the electromagnetic energy/signal from/to inlet/outlet to/from outlet/inlet of the couplet.

7. The antenna as claimed in claim 1, wherein the partition wall (7) is configured in the radiation chamber for isolation and guidance of the electromagnetic energy entering/leaving through the window W towards the outlet pairs (2) and (3)/inlet (1), wherein a length of the partition wall (7) provide a means to reduce the mutual impedance among the outlet pairs (2) and (3) of the radiated/transmitted wave thereby ensuring a broad band of operation.

8. The antenna as claimed in claim 1, wherein polarization of an electromagnetic energy/signal depends on the orientation of an electric field, the inlet 1 has the direction of the electric field perpendicular to the broad-wall of the couplet (60), where the orientation of the electric field does not change as its travels from the inlet 1 to the outlet pairs 2 and 3, therefore the radiated electromagnetic energy has the same orientation of the electric field in a direction perpendicular to the broad-wall of the couplet (60).

9. The antenna as claimed in claim 1, wherein the feeding chamber further comprises a provision (42) to reduce the broad-wall which provides a facility to control the phase of the electromagnetic signal fed to the couplets (60).

10. The antenna as claimed in claim 1, wherein the feeding chamber further comprises a groove (43) and (44) configured inside the feeding chamber (41) to provide a facility to control the amplitude of the electromagnetic signal fed to the couplets (60).

11. The antenna as claimed in claim 1, wherein the antenna further comprises a surface wave suppressor (45) is configured to operate along with the beam constraining layer to get a predetermined elevation beam-width and the surface wave suppressor is further configured to operate with the radiator, thereby reducing a lateral radiation which improves the isolation among the antenna arrays.
12. The antenna as claimed in claim 1, wherein the antenna further comprises a calibration channel configured to perform the calibration of the receive antenna, wherein the calibration is to provide a feedback by tapping the amplitude and phase of the electromagnetic signal that is fed to a row of receive antennas, where the feedback is provided on the amount of variation in amplitude and phase from the pre-determined values, thereby the values of amplitude and phase are corrected.

13. The antenna as claimed in claim 1, wherein the calibration channel comprises a plurality of primary waveguide channels (51) that feed the couplet or array of couplets, a slot (52) configured in a narrow wall of the primary waveguide channels to tap a portion of the electromagnetic energy and a secondary waveguide channels (53) configured to receive the tapped electromagnetic energy for calibration, where the amount of energy to be tapped is decided by the slot orientation angle β.

14. The antenna as claimed in claim 1, wherein the isolation structure is a metallic plate made up of an array of blind longitudinal slots (Index) with a predetermined Length Ls, width Ws, pitch Ps and depth Ds parameters to improve the isolation between the transmit antenna (10) and the receive antenna (20).
, Description:FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
(See section 10, rule 13)

“A trans-receive antenna for a radar system”
By
BHARAT ELECTRONICS LIMITED
WHOSE ADDRESS IS
OUTER RING ROAD, NAGAVARA, BANGALORE – 560045, KARNATAKA, INDIA

The following specification particularly describes the invention and the manner in which it is to be performed.

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention generally relates to an antenna system and more particularly to a Trans-receive antenna system suited specifically for radars.

BACKGROUND OF THE INVENTION

[0002] A Trans-receive antenna systems are well known in the art which facilitates simultaneous transmission and reception of signals. In general, Radars are broadly categorized as Pulsed Radars and FMCW (Frequency Modulated Continuous Wave) Radars. In pulsed radars transmitter and receiver are switched alternatively where as in FMCW radars transmitters and receivers operate simultaneously.
[0003] Long range FMCW Radars usually pose a challenging task as the receive signal may be masked under the strong coupled signal between transmit and receive antenna. To alleviate this problem, the Trans-receive antenna system with high degree of isolation is essential. A Phased array antenna system require radiating elements in the array to be placed at a spacing of 0.5λ0 to 0.6λ0 to avoid grating lobes while scanning the beam electronically over a wide scanning angle. The antennas in a phased array system are fed by a Transmit-Receive (T/R) module which controls the amplitude and phased of the driven antenna element. Such antenna systems should have a method of calibrating the amplitude and phases of each antenna element to ensure proper beams forming in space.
[0004] Polarization of the electromagnetic wave radiated from antenna is of critical importance for radar systems. For short range radar systems there is no specific preferred polarization, but long range ground based radars prefer to use vertical polarization for better performance.
[0005] Fully electronic scanning long range CW radar with 3D scanning and 360ºcoverage will require four radiating apertures each scanning over a 90o sector. Each such aperture will have huge number of T/R modules based on the number of elements in the antenna array resulting in a high cost system. A hybrid approach i.e. a semi active aperture is suitable in such cases where electronic scanning is performed in one plane (for example in Azimuth) with mechanical scan in another plane (say in Elevation).
[0006] For antennas with high efficiency conventional slotted waveguide antennas are the prime choice for radars. Various types of slotted waveguide antennas are reported in one of the prior art.
[0007] In another prior art, for phased array applications, narrow wall slots are generally preferred as the spacing can be maintained typically at 0.5λ0 but such narrow wall slots can generate horizontal polarized waves. To generate vertical polarization from waveguide there is a need to have longitudinal slots in the broad wall of waveguide. To use such waveguide antenna in a phased array ridges were used to reduce the broad-wall width and thereby spacing can be maintained in the order of 0.5 λ0. However, such type of structures will have high tolerance for fabrication along with the requirement of vacuum brazing to reduce gaps between layers. Therefore, realization of such structure is complex and costly.
[0008] Modern radars also have requirements of wide band of operation. In such cases conventional waveguide slot antennas which are resonant in nature reduces the band of operation. A high gain antenna will have large number of elements and the conventional series feeding will suffer from reduced bandwidth.
[0009] Therefore, there is a need in the art with Trans-receive antenna systems to solve the above mentioned limitations.

SUMMARY OF THE INVENTION

[0010] 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.
[0011] Accordingly, in one aspect of the present invention relates to a trans-receive antenna for a radar system, the trans-receive antenna comprising of: at least one transmit antenna (10) configured to transmit electromagnetic signals, wherein the transmit antenna (10) comprises at least one transmit beam constraining layer (11), at least one radiating aperture layer (12) and at least one feed layer type 1 (13), wherein the radiating aperture layer (12) is configured in conjunction with the transmit beam constraining layer (11) and feed layer type 1 (13) to form the transmit antenna, at least one receive antenna (20) configured to receive electromagnetic signals, wherein the receive antenna (20) comprises at least one radiating aperture layer (12), at least one feed layer type 1 (13), at least one feed layer type 2 (23) and at least one Interface layer (24), wherein the radiating aperture layer (12) is configured in conjunction with the feed layer type 1 (13), feed layer type 2 (23) along with the interface layer (24) to form the receive antenna and at least one isolation structure (30) configured in-between the at least one transmit antenna (10) and at least one receive antenna (20) to achieve high isolation between the two antennas for facilitating simultaneous transmission and reception.
[0012] 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
[0013] 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.
[0014] Figure 1 shows a schematic of a preferred example embodiment of a Trans-receive antenna system according to an exemplary implementation of the present invention.
[0015] Figure 2 shows the novel couplet (60) of the antennas according to an exemplary implementation of the present invention.
[0016] Figure 3 to 5 shows various embodiments through which the disclosed couplets may be used to form linear antenna arrays according to an exemplary implementation of the present invention.
[0017] Figure 3 shows a scheme of the antenna arrays which provides a wider bandwidth according to an exemplary implementation of the present invention.
[0018] Figure 4 shows a scheme of the antenna arrays which provides a compact structure according to an exemplary implementation of the present invention.
[0019] Figure 5 shows another scheme of the antenna arrays according to an exemplary implementation of the present invention.
[0020] Figure 6 and 7 shows first embodiment of an array antenna formed based on the disclosed couplets and utilizing one of the feeding schemes according to an exemplary implementation of the present invention.
[0021] Figure 8 and 9 shows second embodiment of an array antenna formed based on the disclosed couplets and utilizing one of the feeding schemes according to an exemplary implementation of the present invention.
[0022] Figure 10 shows the details of the calibration structure for use in with the stacked row of receive antennas (20) according to an exemplary implementation of the present invention
[0023] Figure 11 shows an isolation structure (30) which may be used in conjunction with the antenna arrays according to an exemplary implementation of the present invention.
[0024] Figure 12 shows the third embodiment where the disclosed antenna system is used as per the schematic of Figure 1 according to an exemplary implementation of the present invention.
[0025] 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 OF THE INVENTION
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] The various embodiments of the present invention describe about a vertically polarized collocated Trans-receive antenna system suited specifically for radars with following features, i.e. High gain and High efficiency, High Isolation between transmit and receive. (For short range CW radar applications), ability to be used in a phased array system, integrated calibration provisions, vertical polarization (for long range radar applications), wide band of operation, simple and low cost realization methods.
[0034] The present invention provides a Transmit-Receive Antenna with high isolation and wide-bandwidth. The antenna system of the present invention consists of Transmit Antenna, Receive Antenna and an Isolation Provision. The Transmit Antenna may include radiating aperture or an array of radiating apertures or a beam controlling structure. The Transmit antenna may also include waveguide feed to direct electromagnetic energy from/to the radiating apertures to/from the input. The Receive Antenna may include radiating aperture or an array of radiating apertures. The Receive antenna may also include waveguide feed to direct electromagnetic energy from/to the radiating apertures to/from the input. A plurality of such receive antennas may be formed to control the beam electronically in receive mode for phased array application. An integrated calibration provision is also disclosed. Further, an integrated isolation scheme for FMCW radar system is also disclosed.
[0035] In one embodiment, radiation aperture layer may be used in conjunction with feed layer type1, feed layer type 2 or a hybrid of both to form a linear array.
[0036] In one embodiment, the linear array thus formed may be used in conjunction with a beam constraining layer and a surface wave suppressor to form a transmit antenna with a fixed beam.
[0037] In one embodiment, the linear array thus formed may be used as a stacked array and a calibration channel to form a receive antenna with a phased array provision.
[0038] In one embodiment, the isolation structure may be formed by array of long slots.
[0039] In one embodiment, the present invention discloses a novel couplet comprising of feeding chamber, radiation chamber, symmetric steps, asymmetric steps and a partition wall. The said couplet may be used as a radiator.
[0040] The antenna system formed from the novel couplets may be used in phased array applications with vertical polarization due to use of hollow conductors. Further, the antenna system formed from the novel couplets may be used for fixed beam requirements.
[0041] In one embodiment, a calibration provision is integrated within the antenna system.
[0042] In one embodiment, a wideband performance is achieved by removal of resonant and series feeding elements. An isolation scheme is disclosed for use of the antenna system in a CW environment.
[0043] In one embodiment, a calibration channel may be formed from a slot with a certain angle to tap the electromagnetic energy from the said linear array to a waveguide for the purpose of calibration.

[0044] Figure 1 shows a schematic of a preferred example embodiment of a Trans-receive antenna system according to an exemplary implementation of the present invention.
[0045] The figure shows a schematic of a preferred example embodiment of a Trans-receive antenna system. In one embodiment, the trans-receive antenna comprising of: at least one transmit antenna (10) configured to transmit electromagnetic signals, wherein the transmit antenna (10) comprises at least one transmit beam constraining layer (11), at least one radiating aperture layer (12) and at least one feed layer type 1 (13), wherein the radiating aperture layer (12) is configured in conjunction with the transmit beam constraining layer (11) and feed layer type 1 (13) to form the transmit antenna, at least one receive antenna (20) configured to receive electromagnetic signals, wherein the receive antenna (20) comprises at least one radiating aperture layer (12), at least one feed layer type 1 (13), at least one feed layer type 2 (23) and at least one Interface layer (24), wherein the radiating aperture layer (12) is configured in conjunction with the feed layer type 1 (13), feed layer type 2 (23) along with the interface layer (24) to form the receive antenna and at least one isolation structure (30) configured in-between the at least one transmit antenna (10) and at least one receive antenna (20) to achieve high isolation between the two antennas for facilitating simultaneous transmission and reception.
[0046] In an embodiment, the novel couplets (60) may be used to form Radiating aperture layer (12). Such Radiating aperture layer (12) may be used in conjunction with a Transmit beam constraining layer (11) and Feed layer type 1 (13) to form a fixed beam antenna system which may be used as transmit antenna system 10 in the current example embodiment. Further, the radiating aperture layer (12) may also be used in conjunction with a Feed layer type 1 (13), Feed layer Type 2 (23) along with an Interface layer (24) to form an antenna system which may be used as a phased array antenna system. Such an antenna system may be used as receive antenna (20) in the current example embodiment.
[0047] The antenna systems (10) and (20) as formed may be used with an isolation layer to achieve high degree of isolation between the two antenna systems for facilitating simultaneous communication.
[0048] The above example embodiment is one of ways to utilize the present invention. However, it is to be noted that the example embodiment in no way binds the invention not to be used in certain other ways. Another example embodiment could be a system where the antenna system (10) or (20) is used both as transmit and receive antenna.
[0049] Figure 2 shows the novel couplet (60) of the antennas according to an exemplary implementation of the present invention.
[0050] The figure shows the novel couplet (60) of the antennas. The radiating aperture layer (12) of the transmit antenna (10) and the receive antenna (20) comprises a plurality of couplets (60) to form the radiating aperture layer (12), where each couplet (60) comprises a feeding chamber (9), a radiation chamber (6), a plurality of symmetric steps (5), asymmetric steps (4) and a partition wall (7).
[0051] The couplet (60) is basically a three port device comprises at least one inlet (1) and at least two outlets (2 and 3) in case where the couplet (60) is used as a radiator for transmission of electromagnetic signals/energy and the couplet (60) comprises at least two inlets and at least one outlet in case where the couplet (60) is used as a radiator for reception of electromagnetic signals/energy. The couplet (60) may consist of a feeding chamber (9) and a radiation chamber (6). A window may be present to control the degree of energy flow to/from feeding chamber (9) from/to radiation chamber. The couplet (60) may house grooves and partition wall for smooth transfer of electromagnetic energy from/to inlet/outlet to/from outlet/inlet.
[0052] During transmission, the electromagnetic signals/energy are fed from inlet (1) of the couplet (60) and the electromagnetic energy travels through a window W to enter the radiation chamber (6). The couplet (60) is a waveguide made up of metal forming the outer boundary and hollow inside. The broad wall dimension ‘G’ of the couplet (60) may be selected based on mode of the electromagnetic signal propagating over the desired frequency of operation, a narrow wall height ‘H’ is determined based on the aperture impedance match and the window ‘W’ is configured to control the amount of electromagnetic signal/energy flow to/from feeding chamber (9) from/to radiation chamber (6). The window W plays a critical role in the energy transfer from the inlet feed (1) towards the radiation chamber (6). Window W provides a mechanism of controlling the power entering the radiation chamber of the couplet (60). Such a facility may be useful while using the disclosed couplet in an array formation.
[0053] The groove (4) (the asymmetric step) and the groove (5) (the symmetric step) are configured to ensure smooth transition of the electromagnetic energy/signal from/to inlet/outlet to/from outlet/inlet of the couplet (60). The groove (4) (the asymmetric step) may be used to ensure smooth transition of the electromagnetic energy/signal from the inlet (1) towards the radiation chamber (6). The electromagnetic energy after entering the radiation chamber flows towards the outlet pair (2) and (3). The outlet pairs (2) and (3) radiates the electromagnetic energy from the radiation chamber (6) to free space. The groove (5) (symmetric step) may be utilized for smooth transfer of the electromagnetic energy from the radiation chamber (6) towards the outlet pairs (2) and (3) over a broad range of frequency.
[0054] The partition wall (7) is configured in the radiation chamber for isolation and guidance of the electromagnetic energy entering/leaving through the window W towards the outlet pairs (2) and (3)/inlet (1), wherein a length of the partition wall (7) provide a means to reduce the mutual impedance among the outlet pairs (2) and (3) of the radiated/transmitted wave thereby ensuring a broad band of operation.
[0055] The polarization of an electromagnetic energy/signal depends on the orientation of an electric field, the inlet (1) has the direction of the electric field perpendicular to the broad-wall of the couplet (60), where the orientation of the electric field does not change as its travels from the inlet (1) to the outlet pairs (2) and (3), therefore the radiated electromagnetic energy has the same orientation of the electric field in a direction perpendicular to the broad-wall of the couplet (60). Therefore, the disclosed couplets as per the embodiment in figure 2 will be vertically polarized.
[0056] The bandwidth of the couplet (60) will decide the final bandwidth of the overall antenna system. Waveguides typically have mono mode bandwidth of 40 %. As the disclosed couplet (60) is not having any bandwidth constraining structure like resonant elements, coupling cavities, the disclosed couplet (60) can easily achieve the bandwidth of the waveguide by careful choice of partition wall (7), groove (4) and (5).
[0057] Figure 3 to 5 shows various embodiments through which the disclosed couplets may be used to form linear antenna arrays according to an exemplary implementation of the present invention. The plurality of couplets may be used to form the radiation aperture layer (12).
[0058] Figure 3 shows a scheme of the antenna arrays which provides a wider bandwidth according to an exemplary implementation of the present invention.
[0059] The figures show a scheme of the antenna arrays which provides a wider bandwidth. The inlet (8) feeds the electromagnetic signal/energy into the feed layer type 1 (13).The electromagnetic signal/energy flows from the inlet to the feeding chamber (33).The electromagnetic signal/energy similarly passes through the feeding chambers (32) and (31) before entering into the radiation chamber (6) or the radiation aperture layer (12).This scheme which uses feed layer type 1 to feed the aperture layers is of corporate nature thereby keeping the bandwidth of the couplet intact.
[0060] Figure 4 shows a scheme of the antenna arrays which provides a compact structure according to an exemplary implementation of the present invention.
[0061] The figure shows a scheme which provides a compact structure. The inlet 8 feeds the electromagnetic energy into the feed layer type 2 (23). The electromagnetic energy flows from the inlet (8) to the feeding chamber (41) and then enters the radiation chamber (6). It may be noted here that from the inlet (8) to the radiation chamber (6) the electromagnetic energy has to traverse only one feeding chamber (41) unlike the above scheme in Figure 3 where it traverses multiple chambers before entering radiation chamber (6). The feeding chamber (41) may have a provision (42) to reduce the broad-wall which provides a facility to control the phase of the electromagnetic signal that is fed to the couplets (60). The feeding chamber further comprises a groove (43) and (44) may be introduced inside the feeding chamber (41) to provide a facility to control the amplitude of the electromagnetic signal that is fed to the couplets (60). This scheme provides compactness, but the bandwidth may get reduced and this scheme which uses feed layer type 2 to feed the aperture layers is of series nature thereby reducing the bandwidth as achieved by the couplet. The above mentioned schemes provide two extremes of operation using the couplets-one provides wider bandwidth whereas another provides compactness. A middle approach may be taken to form the antenna array as shown in Figure 5.
[0062] Figure 5 shows another scheme of the antenna arrays according to an exemplary implementation of the present invention.
[0063] The figure shows another scheme of the antenna arrays. In this method the inlet (8) feeds the electromagnetic energy to feed type 1 which may have a single feeding chamber (31) or multiple feeding chambers (not shown).The electromagnetic energy from the feed type 1 (13) flows to feed type 2 (23) which has a single feeding chamber (41). The electromagnetic energy then enters the radiation chamber (6).
[0064] Figure 6 and 7 shows first embodiment of an array antenna formed based on the disclosed couplets and utilizing one of the feeding schemes according to an exemplary implementation of the present invention.
[0065] The figure shows the first embodiment of an array antenna formed based on the disclosed couplets and utilizing one of the above mentioned feeding schemes. In this embodiment a fixed beam antenna array is formed. A fixed beam antenna array may have a predetermined azimuth and elevation beam-widths. The azimuth beam-width will be decided by the number of couplets used to form the row antenna. There is no restriction on the number of couplets to be used in a row antenna which may be decided based on its azimuth beam-width requirement. The elevation beam-width will be based on the number of stacked rows antennas in the vertical direction or a beam constraining structure. The beam constraining layer (11) may be used along with a surface wave suppressor (45). The beam constraining layer (11) is used to get a predetermined elevation beam-width. However, mounting of the antenna (10) on some metallic plates will have impact on the elevation beam-width. Therefore, the surface wave suppressor (45) makes the impact of mounting structures negligible by reducing lateral radiation from the antenna. When such an antenna array (10) is used in conjunction with another antenna array the reduced lateral radiation improves the isolation among the antenna arrays. Stacking arrays to reduce the beam with may lead to cost and weight. Following the above method this invention generated a low cost, broad bandwidth, high efficiency vertically polarized fixed beam antenna array (10).
[0066] In one embodiment, the antenna further comprises a surface wave suppressor (45) is configured to operate along with the beam constraining layer to get a predetermined elevation beam-width and the surface wave suppressor is further configured to operate with the radiator, thereby reducing a lateral radiation which improves the isolation among the antenna arrays.
[0067] Figure 8 and 9 shows second embodiment of an array antenna formed based on the disclosed couplets and utilizing one of the feeding schemes according to an exemplary implementation of the present invention.
[0068] The figure shows second embodiment of an array antenna formed based on the disclosed couplets and utilizing one of the above mentioned feeding schemes. In this embodiment, a phased antenna array is formed. A phased array antenna scans the beam electronically by controlling the amplitude and phase of individual radiating elements or a group of radiating elements. For the present invention to be used as a phased array antenna the amplitude and phases of the disclosed couplets may be controlled. However, for high gain antennas a large number of couplets will lead to a huge number of modules for controlling the inputs. Therefore, a middle path may be followed where the plurality of couplets is used to form antenna array in one plane (azimuth plane) as per Figure 3 to 5. After the array is formed they may be stacked in another plane (elevation plane) maintaining a spacing S as shown in figure 8 between 0.5λ0 to 0.6λ0. The inlets (46) of the stacked array as per figure 9 may be connected to modules for controlling the phase and amplitude of the antenna thus formed. Applying correct phases and amplitude is essential for proper working of the Phased array antenna. To verify the applied phases and amplitude phased array antennas use calibration methods. The present invention provides a simple calibration channel (47) which is basically a coupler to perform the calibration for the inventive antenna.
[0069] In one embodiment, the antenna further comprises a calibration channel configured to perform the calibration of the receive antenna, wherein the calibration is to provide a feedback by tapping the amplitude and phase of the electromagnetic signal that is fed to a row of receive antennas, where the feedback is provided on the amount of variation in amplitude and phase from the pre-determined values, thereby the values of amplitude and phase are corrected.
[0070] Figure 10 shows the details of the calibration structure for use in with the stacked row of receive antennas (20) according to an exemplary implementation of the present invention.
[0071] The figure shows the details of the calibration structure (47) for use in with the stacked row of receive antennas (20). The purpose of calibration is to provide a feedback by tapping the amplitude and phase that is fed to the row of receive antennas. Feedback is provided on the amount of variation in amplitude and phase from the pre-determined values. Based on the feedback, using the calibration provision the values of amplitude and phase are corrected. The calibration provision may be designed in a way that the calibration structure will not load and disturb the antenna radiation. The inlets (51) are primary waveguide channels that feed the couplet or array of couplets. A portion of the electromagnetic energy is being tapped by the slot (52) present the narrow wall of the primary waveguide channels. The tapped electromagnetic energy flows into the secondary waveguide channels (53) used as calibration channel. The amount of energy to be tapped is decided by the slot orientation angle β. This angle β may be in the range from 5º to 25º. The higher the angle the amount of energy tapped will be more but it will also load the primary waveguide channels. The lower the angle the amount of energy tapped will be less but may be below the sensitivity of modules for evaluation phases and amplitudes. Therefore, the angle β may be chosen carefully based on requirement.
[0072] In one embodiment, the calibration channel comprises a plurality of primary waveguide channels (51) that feed the couplet or array of couplets, a slot (52) configured in a narrow wall of the primary waveguide channels to tap a portion of the electromagnetic energy and a secondary waveguide channels (53) configured to receive the tapped electromagnetic energy for calibration, where the amount of energy to be tapped is decided by the slot orientation angle β.
[0073] Figure 11 shows an isolation structure (30) which may be used in conjunction with the antenna arrays according to an exemplary implementation of the present invention.
[0074] The figure shows an isolation structure (30) which may be used in conjunction with the antenna arrays as disclosed. The isolation structure is a metallic plate made up of an array of blind longitudinal slots (Index) with a predetermined Length Ls, width Ws, pitch Ps and depth Ds parameters to improve the isolation between the transmit antenna (10) and the receive antenna (20). Based on the frequency of operation the parameters of the isolator plate are decided. The purpose of the isolator plate is to attenuate the incident surface wave as it progresses through the array of blind long slots. It is to be noted that based on the range of frequencies the radiator may operate, a variable parameter isolator plate may be formed to reduce the incident surface wave for that predetermined range of frequencies.
[0075] Figure 12 shows the third embodiment where the disclosed antenna system is used as per the schematic of Figure 1 according to an exemplary implementation of the present invention.
[0076] The figure shows the third embodiment where the disclosed antenna system is used as per the schematic of Figure 1. The fixed beam antenna array (10) as per first embodiment may be used as a transmit antenna for CW radars. The phased array antenna (20) as per second embodiment may be used as a receive antenna for CW radars. For CW radars the isolation is an important parameter which decides the overall performance of the CW radar. The isolation will depend on the transmit array beam-width and the attenuation of the surface wave generated by the radiator (10). The beam-width of the transmit antenna therefore may be chosen carefully to ensure that the radar will be able to illuminate the target and at the same time not broad enough to degrade the isolation. The beam constraining layer (11) plays a critical role in this endeavour. The surface wave generated by the transmit antenna will flow towards the receive antenna and therefore will degrade the isolation. The surface wave suppressor (45) attached to the radiator performs the preliminary job of reducing the surface waves flowing towards the receive antenna (20). The isolator plate (30) may further reduce the surface wave flowing towards the receive antenna (20). Therefore, a Trans-receive antenna may be formed with broad bandwidth, phased array provision and high degrees of isolation.
[0077] 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.
[0078] 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.
[0079] 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.