Patent Description:
A traditional array of radiating elements may comprise hundreds of radiating elements and corresponding circuitry, and consume a corresponding amount of power.

In one aspect, there is provided an electronically scanned array as defined by claim <NUM>.

In a further aspect, there is provided an electronically scanned radar array antenna as defined by claim <NUM>.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and should not restrict the scope of the claims. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments of the inventive concepts disclosed herein and together with the general description, serve to explain the principles.

The numerous advantages of the embodiments of the inventive concepts disclosed herein may be better understood by those skilled in the art by reference to the accompanying figures in which:.

Broadly, embodiments of the inventive concepts disclosed herein are directed to radiating horns embedded in a nose cone. The radiating horns are configured as an electronically scanned array; each radiating horn is embedded in the dielectric material of a nose cone. One or more of the radiating horns is driven by a phase shifter. The phase shifters are configured to produce a radiation pattern with attenuated side lobes.

Referring to <FIG>, a perspective view of a nose cone <NUM> suitable for use in exemplary embodiments is shown. The nose cone <NUM> may define a generally unused annular space <NUM> (which may be empty or filled with an inert material) and a central space <NUM> that may house certain electronic elements for the corresponding munition guidance system.

Referring to <FIG>, a side view of a nose cone and radar antenna system according to an exemplary embodiment is shown. Where the nose cone defines a generally unused annular space <NUM>, a plurality of actively driven radiating horns <NUM>, <NUM> (wave guides) are disposed in the annular space <NUM>. The radiating horns <NUM>, <NUM> may be angularly disposed about a central axis defined by the nose cone, including a central space <NUM> that may house electronics for navigational components such as a short-wave infrared location imaging system. In at least one embodiment, there are four radiating horns <NUM>, <NUM> with printed circuit board to waveguide transitions incorporated into the printed circuit board. The open, radiating portion of each radiating horn <NUM>, <NUM> in a short-wave infrared system may be disposed proximal to an exterior surface <NUM> of the nose cone such that the remaining material of the nose cone between the radiating horns <NUM>, <NUM> and open air (both its thickness and dielectric characteristics) is known and can be accounted for when sending and receiving signals. In at least one embodiment, the open, radiating portion of the radiating horns <NUM>, <NUM> may be generally rhombic or quadrilateral. Furthermore, when fabricating the nose cone with an embedded radar antenna system, nose cone material may be injection molded or otherwise additively manufactured or electroformed with the radiating horns <NUM>, <NUM> in place such that the nose cone material may be structural, and hold the radiating horns <NUM>, <NUM> in place. Additive manufacture may allow the nose cone with embedded radiating horns <NUM>, <NUM> to be proportioned according to aerodynamic / mechanical considerations. In at least one embodiment, the radiating horns <NUM>, <NUM> may be metallically additively manufactured with a PEEK nose cone injection molded around them. Alternatively, the radiating horns <NUM>, <NUM> may be molded interconnect devices or plated injection molded PEEK (or other dielectric material).

In a system where radiating horns <NUM>, <NUM> are disposed in a nose cone, and not coaxial with the fuselage, each beam is slightly offset. As the radiating horns <NUM>, <NUM> are activated with variable phase between the radiating horns <NUM>, <NUM>, signal strengths are dependent on the canceling of those beams relative to the excess of the fuselage and the aerodynamic maneuvering of the of the projectile. Where all phases and amplitudes are substantially identical, the target is in collinear line-of-sight with flight motion; otherwise there may be imbalances.

In at least one embodiment, a feed layer <NUM> is disposed at a bottom surface of the nose cone; for example, the feed layer <NUM> may comprise a metallized ground plane with multi-layered printed circuit boards. In at least one embodiment, the top surface of the feed layer <NUM> touching the radiating horns <NUM>, <NUM> is a ground plane while a bottom layer of the feed layer <NUM> is a millimeter wave printed circuit comprising active feed circuitry. The printed circuit board ground is in intimate contact with the ground that is contiguous with the exterior surface of the radiating horns <NUM>, <NUM>. The feed layer <NUM> may be configured such that certain radiating horns <NUM>, <NUM> are dedicated transmitters and other radiating horns <NUM>, <NUM> are dedicated receivers. Alternatively, the feed layer <NUM> may be configured to switch some or all of the radiating horns <NUM>, <NUM> between a transmit mode and receive mode.

In at least one embodiment, the disposition and simultaneous, coherent operation of the radiating horns <NUM>, <NUM> enable low aiming for the radar on a very limited volumetric platform. Embedding the radiating horns <NUM>, <NUM> in the plastic dielectric material of the nose cone integrates and minimizes the parasitic effect of the plastic. It may be appreciated that completely embedding the radiating horns <NUM>, <NUM> in the dielectric material of the nose cone provides structural stability and resistance to forces from acceleration. The radiating horns <NUM>, <NUM> are driven simultaneously with phase shifted signals to produce desirable side lobe levels within the constraints of the annular space <NUM>. In at least one embodiment, half of the radiating horns <NUM>, <NUM> comprise a receive array while the other half comprise a transmit array. Pulsed system can be configured to operate as a single array the uses all the radiating horns <NUM>, <NUM> in receive mode or a transmit mode at a given time.

Referring to <FIG>-4B, a side view and unfurled view of a nose cone and radar antenna system according to an exemplary embodiment are shown. Where the nose cone defines a generally unused annular space <NUM>, a plurality of generally ovoid radiating horns <NUM>, <NUM> are angularly disposed in the annular space <NUM> about a central axis defined by the nose cone, including a central space <NUM> that may house electronics for navigational components such as a short-wave infrared system. The ovoid, open, radiating portion of each radiating horn <NUM>, <NUM> may be disposed proximal to an exterior surface <NUM> of the nose cone such that the remaining material of the nose cone between the radiating horns <NUM>, <NUM> and open air (both its thickness and electromagnetic insulating characteristics) is known and can be accounted for when sending and receiving signals. Radiating horns <NUM>, <NUM> are disposed to maximize surface area for element gain. A radiating horn array may enable a degree of freedom to set radiating horn gain and beam width without changing the limited scan beam former circuit architecture. In one exemplary embodiment, where a short-wave infrared system is located is located in the central space <NUM>, a mmWave aperture and radar system may be disposed in the annular space <NUM> coaxial to the fuselage's axis.

In at least one embodiment, a feed layer <NUM> is disposed at a bottom surface of the nose cone. The feed layer <NUM> may be configured such that certain radiating horns <NUM>, <NUM> are dedicated transmitters and other radiating horns <NUM>, <NUM> are dedicated receivers. Alternatively, the feed layer <NUM> may be configured to switch some or all of the radiating horns <NUM>, <NUM> between a transmit mode and receive mode.

In at least one exemplary embodiment, for a conical frustum having a height of approximately <NUM> inches (<NUM>), a top radius of approximately <NUM> inches (<NUM>), and a bottom radius of approximately <NUM> inches (<NUM>), a nose cone would have a lateral surface area of approximately <NUM> inches<NUM> (<NUM><NUM>). Where such a nose cone included an array of four radiating horns <NUM>, <NUM> (or quadrilateral radiating horns <NUM>, <NUM> as in <FIG>), the nose cone embedded array may have maximum free space directivity of approximately <NUM> dB, bandwidth for maximum directivity of <NUM>° to <NUM>°, minimum free space directivity of approximately <NUM> dB, and bandwidth for minimum directivity of <NUM>° to <NUM>°. Metrics are similar for an eight-element array except that the maximum directivity may be approximately <NUM> dB and bandwidth for maximum directivity may be approximately <NUM>° to <NUM>°.

In at least one embodiment, radiating horns <NUM>, <NUM> may be axially forward pointing; alternatively, they may be deliberately canted off the fuselage axis for uncongenial beam pattern synthesis. Furthermore, radiating horns apertures may be arbitrarily contoured. Perpendicular a transition from the radiating horns <NUM>, <NUM> to a PCB feed layer <NUM> is integrated into the PCB feed layer <NUM> containing the RF circuits, etc..

Referring to <FIG>, a bottom, block representation of a nose cone according to an exemplary embodiment is shown. In at least one embodiment, the nose cone is divided a transmit antenna portion <NUM> and a receive antenna portion <NUM>, each using approximately half of the available annular space in a nose cone.

Referring to <FIG>, partial views of a radar aperture in a nose cone according to an exemplary embodiment are shown. In simulated geometries, a conical radiating horn <NUM> is shows disposed on an aperture without a PEEK material nose cone (<FIG>) and with a PEEK material nose cone <NUM> (<FIG>). The radiating horn <NUM> is embedded a half wavelength (approximately <NUM> assuming <NUM> and <NUM> Dk of PEEK) from the exterior surface of the PEEK material nose cone <NUM>. The dielectric is in contact with the aperture <NUM> that may induce a small dielectric perturbation to the antenna aperture which may be adjusted as a tuning parameter to optimize radiation performance; lensing due to the dielectric material may be tuned out or exploited. While <FIG> show a radiating horn <NUM> centered in the PEEK material nose cone <NUM>, in actual implementation, the radiating horns <NUM> would be offset to accommodate a central short-wave infrared imaging lens system.

Referring to <FIG>, a block diagram of a circuit useful for implementing exemplary embodiments is shown operating in the transmit mode. A similar circuit block diagram may be configured for the receive signal, where the signal flow is in the reversed direction; from each of the radiating horns <NUM>, <NUM>, <NUM>, <NUM>, through low nose amplifiers and phase shifters, into a <NUM>-way combiner. The circuit is configured to excite radiating horns <NUM>, <NUM>, <NUM>, <NUM> embedded in a nose cone. A splitter <NUM> may transmit a signal and feed the signal to phase shifters <NUM>, each corresponding to one of the radiating horns <NUM>, <NUM>, <NUM>, <NUM>. In at least one embodiment, each phase shifter <NUM> may comprise a two-bit phase shifter required for left / center / right limited beam scan. The beam forming network, including the phase shifters, as shown, is designed for optimal simplicity, low cost, and ease of manufacture. A hybrid coupler phase shifter may require two diodes per bit, but it may be appreciated that other phase shifter technologies such as RFIC-based phase shifters are envisioned. At least one reference channel corresponding to one of the radiating horns <NUM>, <NUM> may be unshifted; a 1D linear array requires one fewer phase shifted channel than the number of radiating horns <NUM>, <NUM>, <NUM>, <NUM>. In one exemplary embodiment, the circuit may be configured to minimize adjustable phase shifter count and shifter circuit complexity; with sufficient radiating horn directivity, as little as two radiating horns <NUM>, <NUM>, <NUM>, <NUM> and one phase shifter <NUM> may suffice. More complex limited scan arrays may be implemented with additional active RF circuitry. Active radiating horns <NUM>, <NUM>, <NUM>, <NUM> may offset phase shifter loss for optimal effective isotropic radiated power (EIRP) and noise figures, with full EIRP radiated at any time instant.

In at least one embodiment, a 2D active electronically scanned array requires one fewer phase shifter than the total number of array elements. Arrays may be active electronically scanned arrays or passive electronically scanned arrays. The active electronically scanned array architecture requires fewer T/R module RFICs and it may be easier to raise EIRP while maintaining noise figures.

In at least one embodiment, a limited scan array as in <FIG> may be configured to operate in a transmit mode (as shown); an analogous circuit enables a similar configuration to work in a receive mode. Transmit / receive module circuits that include power amplifiers, low noise amplifiers, phase shifters and sets of switching circuits may enable an array configuration utilizing a ½ duplex pulsed transmit / receive radar mode.

Referring to <FIG>-7I, graphs of a radiation patterns according to an exemplary embodiment are shown. For a four-element system operating at <NUM> with at least one λ element spacing and at least one λ circular horn aperture, and phase shift at the horn aperture of <NUM>° (<FIG>), <NUM>° (<FIG>) and <NUM>° (<FIG>), the radiating patterns may exhibit a gentle <NUM> dB Taylor taper. The highest side lobe is a strong function of the aperture element directivity and aperture directivity per number of radiating horns, and is an attenuated grating lobe. Array spacing and array amplitude taper also impact the highest side lobe. In at least one embodiment, <NUM> dB beam slope discrimination from Left-to-Center-to-Right beam positions is demonstrated with -<NUM> dB side lobe levels. Parasitic beam squint-free performance is possible across at least ten percent of the instantaneous bandwidth (IBW); squint-free IBW is a function of the number of radiating horns, spacing, and aperture directivity.

Referring to <FIG>-8I, graphs of a radiation patterns according to an exemplary embodiment are shown. For a four-element system operating at <NUM> with at least one λ element spacing and at least one λ circular horn aperture, and phase shift at the horn aperture of <NUM>° (<FIG>), <NUM>° (<FIG>) and <NUM>° (<FIG>), the radiating patterns may exhibit a gentle <NUM> dB Taylor taper. The highest side lobe is a strong function of the aperture element directivity and is an attenuated grating lobe, and aperture directivity per number of radiating horns. Array spacing and array amplitude taper also impact the highest side lobe. In at least one embodiment, <NUM> dB beam slope discrimination from Left-to-Center-to-Right beam positions is demonstrated with -<NUM> dB side lobe levels. Parasitic beam squint-free performance is possible across at least ten percent of the instantaneous bandwidth (IBW); squint-free IBW is a function of the number of radiating horns, spacing, and aperture directivity.

Referring to <FIG>-9I, graphs of a radiation patterns according to an exemplary embodiment are shown. For a four-element system operating at <NUM> with at least one λ element spacing and at least one λ circular horn aperture, and phase shift at the horn aperture of <NUM>° (<FIG>), <NUM>° (<FIG>) and <NUM>° (<FIG>), the radiating patterns may exhibit a gentle <NUM> dB Taylor taper. The highest side lobe is a strong function of the aperture element directivity and is an attenuated grating lobe, and aperture directivity per number of radiating horns. Array spacing and array amplitude taper also impact the highest side lobe. In at least one embodiment, <NUM> dB beam slope discrimination from Left-to-Center-to-Right beam positions is demonstrated with -<NUM> dB side lobe levels. Parasitic beam squint-free performance is possible across at least ten percent of the instantaneous bandwidth (IBW); squint-free IBW is a function of the number of radiating horns, spacing, and aperture directivity. <FIG> demonstrate invariant parasitic beam squint-free performance across at least a <NUM>% instantaneous bandwidth (<NUM>-<NUM>). Squint-free instantaneous bandwidth is a function of radiating element count, array factor, and radiating horn aperture directivity.

Referring to <FIG>, graphs of a radiation patterns according to an exemplary embodiment are shown. For a two-element system (as in <FIG>), a three-element system (as In <FIG>), or a five-element system (as in <FIG>) operating at <NUM> with at least one λ element spacing and at least one λ circular horn aperture, the radiating patterns may exhibit a gentle <NUM> dB Taylor taper. The highest side lobe is a strong function of the multi-horn array factor pattern of the radiating horn location multiplied by the aperture element directivity. The horns are spaced at greater that ½ wavelength, so grating lobes (aka false main beams) exist. The grating lobe of the radiating horn array pattern is attenuated by the aperture directivity of each radiating horn and is therefore manifested as a higher side lobe as shown in the figures. Array spacing and array amplitude taper also impact the highest side lobe. Beam slope discrimination is a function of element count for a given aperture element directivity and array spacing. For example, a two-element system may exhibit 2dB discrimination; a three-element system may exhibit <NUM> dB discrimination; and a five-element system may exhibit <NUM> dB discrimination.

Referring to <FIG>, an equivalent representation of the radiating horns is a subarray <NUM> and corresponding radiation pattern according to an exemplary embodiment are shown. The radiating horn and subarray may have identical directivity, so subarray theory can be applied to the concepts as described herein. A subarray radiation pattern <NUM> (one of the radiating horns) is produced with low side lobes, similar to the case of a λ / <NUM> spaced subarray. The grating lobe series <NUM> are due to the radiating horn array's array factor being spaced greater than ½ wavelength. These grating lobes are attenuated by the radiating horn's (aka subarray) radiating pattern as shown in <FIG> as small side lobe <NUM>. These attenuated grating lobe/sidelobes result in higher side lobes, as shown in <FIG>. This is in accordance with array pattern multiplication theory. Grating lobes <NUM> grow and shrink with scan due to the pattern multiplications with the radiating horns (the array element) radiation pattern. and appear as modulating side lobes as shown in <FIG>. This effect may be minimized for limited scan arrays.

In at least one embodiment, the subarrays <NUM> produce the subarray radiation pattern <NUM>. The array of subarrays produce secondary radiation patterns <NUM>, <NUM>, which are part of the grating lobe series. An aggregate radiation pattern is produced by multiplying the subarray radiation pattern and the secondary array factor radiation patterns which create patterns <NUM>, <NUM>, which may comprise grating lobes. The aggregate radiation pattern attenuates the side lobes of the grating lobe patterns <NUM>, <NUM>, etc. Radiating horns have a narrower beam with a greater gain than individual radiating elements in a conventional face array. Each radiating horn may operate as a subarray <NUM> that has a directive radiation pattern. Each radiating horn "subarray equivalent" attenuate the main beam of the neighboring radiating horns. Gain and the beam width of the radiating horns may be directive enough to squelch main beams of those neighboring radiating horns. Main beams move with the false main beams, but are attenuated and manifest at a level modulated in amplitude, low enough that they do not interfere. Embodiments may enable radiating horns that are equivalent to a ½ spaced subarray, and an array of subarrays equivalents (the radiating thorns). The feed network of the array may be simpler than existing systems and the required phase shift count may be optimally minimized.

Embodiments of the present disclosure enable a small environmentally robust, nose cone compatible 1D or 2D limited scan horn radiating element-based millimeter wave limited scan array antenna system collated with, and complementary to, a short-wave infrared target location imaging system for munitions or other projectile platforms. Radiating horn elements are minimally perturbed by the short-wave infrared housing and cone dielectric loading. The dielectric cone only acts as a protective superstrate or lens to the aperture antennas. A PEEK cone provides a built-in radome. The nose cone dielectric can be used to tune match and optimize the beam. Post-processing of multiple radar return pulses can be post processed for monopulse-like synthetic beam sharpening. Radiating horn structures can be formed by metallic additive manufacture, electro-forming, or plating of plastic. The nose cone may be injection molded about radiating horn array. Radiating horns may be dielectric loaded if required. The nose cone may be injection molded about a metallic radiating horn array, potentially an aperture matching / lens device. In at least one embodiment, waveguide transition is embedded in RF PCB, and connected to the radiating horns by metallic ground bonding.

Embodiments of the present disclosure offer minimal platform perturbations. Embedding the radiating horns in the nose cone preclude the severe dielectric lensing associated with patch-type radiators. Metallic loading of fuselage housing is minimal because radiating horns / waveguides are not driven against RF ground like patch type radiators.

Embodiments of the present disclosure may be integrated with microwave / mmWave dichroic surface-based C-Band height-of-burst altimeter antenna. Limited scan array offers beam deflection target discrimination with a very small, conformal form factor. Embodiments may enable a mmWave aperture and radar system compatible with a short-wave infrared system that is coaxial to a fuselage's axis.

Claim 1:
An electronically scanned array comprising:
an injection molded nose cone formed of a dielectric material and defining an axis;
a plurality of radiating horns (<NUM>, <NUM>), each disposed around the axis defined by the nose cone; and
a feed layer (<NUM>) connected to each of the radiating horns,
wherein:
the plurality of radiating horns is embedded in the dielectric material of the nose cone; and
the feed layer is configured to simultaneously activate each of the plurality of radiating horns to produce a limited scan steerable radiation pattern.