EP3896786A1

EP3896786A1 - Antenna array

Info

Publication number: EP3896786A1
Application number: EP20275076.6A
Authority: EP
Inventors: designation of the inventor has not yet been filed The
Original assignee: BAE Systems PLC
Current assignee: BAE Systems PLC
Priority date: 2020-04-16
Filing date: 2020-04-16
Publication date: 2021-10-20

Abstract

An antenna array for a High-Altitude Long Endurance aircraft, the antenna array comprising a plurality of antennas arranged to extend in different directions relative to each other such that a field of regard of the antenna array is greater than a field of regard of any individual antenna of the plurality of antennas.

Description

FIELD

The present disclosure relates to an antenna array, specifically an antenna array for a high altitude long endurance aircraft. The present disclosure also relates to a payload module having the same, along with a high altitude long endurance aircraft having the antenna array.

BACKGROUND

Antenna arrays are known in the art. An antenna array (or array antenna) is a set of multiple connected antennas, which work together as a single antenna, to transmit or receive radio waves. The individual antennas are usually connected to a single receiver or transmitter by feedlines that feed the power to the individual antennas (sometimes known as elements) in a specific phase relationship. The radio waves radiated by each individual antenna combine and superpose. The radio waves may interfere constructively to enhance the power radiated in desired directions, and/or interfere destructively to reduce the power radiated in other directions. Similarly, when used for receiving, the separate radio frequency currents from the individual antennas combine in the receiver with the correct phase relationship to enhance signals received from the desired directions and cancel signals from undesired directions. More sophisticated array antennas may have multiple transmitter or receiver modules, each connected to a separate antenna element or group of elements.
An antenna array can achieve higher gain (directivity), in other words a narrower beam of radio waves, than could be achieved by a single element. In general, the larger the number of individual antenna elements used, the higher the gain and the narrower the beam. Some antenna arrays (such as phased array radars) are composed of thousands of individual antennas. Arrays can be used to achieve higher gain, to give path diversity. Path diversity can increase communication reliability and cancel interference from specific directions. As such, the arrays can steer the radio beam electronically to point in different directions, and can be used for radio direction finding.
A phased array usually means an electronically scanned array; a driven array antenna in which each individual element is connected to the transmitter or receiver through a phase shifter controlled by a computer. The beam of radio waves can be steered electronically to point instantly in any direction over a wide angle, without moving the antennas.
High altitude long endurance (HALE) unmanned aircraft have been devised. These typically have long wingspans and low drag to improve their ability to operate efficiently for weeks, months or even years at altitudes in excess of 15km. In some examples, HALE aircraft include one or more payloads comprising electronic components, such as sensors.
Conventional antenna arrays are not suitable for some aircraft such as HALE aircraft because these aircraft have tight weight requirement and aerodynamic draft limits. There is a need for developing improved antenna systems for use with HALE aircraft.

SUMMARY

According to a first aspect of the present disclosure, there is provided an antenna array for a High-Altitude Long Endurance aircraft, the antenna array comprising: a plurality of antennas arranged to extend in different directions relative to each other such that a field of regard of the antenna array is greater than a field of regard of any individual antenna of the plurality of antennas.
The provision of an antenna array with this arrangement allows high gain radio transmitting and receiving while maintaining a low weight. Further, the antenna array may be designed to be highly aerodynamic, i.e. not create significant drag on the aircraft when it is in flight.
In one example, one or more of the plurality of antennas comprise a blade antenna. The blade antenna are lightweight and are shaped to provide very little aerodynamic drag on the aircraft.
In one example, the antenna array comprises a base plate to which the antennas are coupled. The base plate may be substantially non-planar. In one example, the contour of the base plate is arranged to match the contour of the part of the aircraft to which it is attached such that the base plate may be coupled to the part in a flush arrangement. The curved base plate also enables the blade antennas to project perpendicularly from the base plate at different angles, which widens the field of regard the antenna array. The antenna field of higher gain will be in slightly different planes to the horizontal axis as they are all offset by the angle of the curvature of base plate.
According to a second aspect of the present disclosure, there is provided a payload module for a High-Altitude Long Endurance aircraft, the payload module comprising: a housing; and an antenna array according to the first aspect coupled to or disposed inside the housing.
In one example, the payload module comprises a sensor for gathering data and a radio, wherein the radio is configured to transmit the data using the antenna array.
In one example, one or more of the plurality of antennas comprise a conformal antenna arranged to conform to a surface of the housing. Conforming the antenna to the surface (i.e. shape) of the housing means that there is very little drag created by the antenna on the aircraft (to which the payload module is coupled) when it is in flight. In one example, the plurality of antennas comprise a combination of blade antennas and conformal antennas.
The conformal antennas may be printed on a surface of the housing.
In one example, the housing comprises at least one region of radio frequency transparent material. Providing a region of radio frequency transparent material means that the one or more antennas may be located within the housing or embedded within the surface of the housing. This means that there may be no additional drag created by the antenna array.
In one example, the one or more conformal antennas are embedded within the region of radio frequency transparent material of the housing. Embedding the one or more conformal antennas within the region of radio frequency transparent material of the housing means that the conformal antennas do not create any additional drag on the aircraft. Alternatively, the one or more conformal antennas may be coupled to an inside surface of the housing, facing through the region of radio frequency transparent material.
In one example, the payload module comprises a mount disposed inside the housing, wherein at least one of the plurality of antennas are coupled to the mount.
In one example, the conformal antenna comprises a patch antenna. Patch antennas are relatively light and so tend not add significant weight to the aircraft.
According to a third aspect of the present disclosure, there is provided a High-Altitude Long Endurance aircraft comprising the antenna array according to the first aspect.
The High-Altitude Long Endurance aircraft may comprise a fuselage, wherein the antenna array is coupled to the fuselage and wherein the shape of the base plate matches the shape of the fuselage. Alternatively, the antenna array may be coupled to a wing or other part of the aircraft, and the shape of the base plate may match the shape of that part instead.
One or more of the plurality of antennas may comprise a conformal antenna arranged to conform to a surface of the fuselage. The one or more conformal antennas may be printed on the surface of the fuselage.
The fuselage may comprise at least one region of radio frequency transparent material. The one or more conformal antennas may be embedded within the region of radio frequency transparent material of the fuselage. Alternatively, the one or more conformal antennas may be coupled to an inside surface of the fuselage, facing through the region of radio frequency transparent material.
The High-Altitude Long Endurance aircraft may comprise a mount disposed inside the fuselage, wherein at least one of the plurality of antennas is coupled to the mount.
According to a fourth aspect of the present disclosure, there is provided a High-Altitude Long Endurance aircraft comprising the payload module according to the second aspect.
According to a fifth aspect of the present disclosure, there is provided an antenna array for an aircraft, the antenna array comprising: a plurality of antennas configured to be coupled to the aircraft, wherein the antennas comprise a combination of conformal antenna and blade antenna.
It will be appreciated that features described in relation to one aspect of the present disclosure can be incorporated into other aspects of the present disclosure. For example, an apparatus of the disclosure can incorporate any of the features described in this disclosure with reference to a method, and vice versa. Moreover, additional embodiments and aspects will be apparent from the following description, drawings, and claims. As can be appreciated from the foregoing and following description, each and every feature described herein, and each and every combination of two or more of such features, and each and every combination of one or more values defining a range, are included within the present disclosure provided that the features included in such a combination are not mutually inconsistent. In addition, any feature or combination of features or any value(s) defining a range may be specifically excluded from any embodiment of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the disclosure will now be described by way of example only and with reference to the accompanying drawings.

Figure 1 is a perspective view of a HALE aircraft;
Figure 2 is a plan view of a HALE aircraft;
Figure 3A is a side view of an example of a blade antenna coupled to a base plate;
Figure 3B is a side view of a patch antenna coupled to a base plate;
Figure 4A is an example of the field of regard of a patch antenna;
Figure 4B is an example of the field of regard of a blade antenna;
Figure 5 is an example of antenna array;
Figure 6 is an example of a side view of payload module and an antenna array;
Figure 7A is an example of a side view of a payload module and an antenna array;
Figure 7B is an example of a front view of a payload module including a plurality of antenna; and
Figure 7C is an example of a side view of a payload module and an antenna array.

For convenience and economy, the same reference numerals are used in different figures to label identical or similar elements.

DETAILED DESCRIPTION

Generally, embodiments herein relate to antenna arrays for use with a vehicle.
Current antenna array systems are relatively heavy and would be unsuitable for use with HALE aircraft due to the strict weight requirements. A lightweight antenna array has been developed that is suitable for use with HALE aircraft. The antenna array allows high gain radio transmitting and receiving while maintaining a low weight. Further, the antenna array may be designed to be highly aerodynamic, i.e. not create significant drag on the vehicle.
Figure 1 shows an illustrative example of an aircraft 100, specifically a HALE unmanned aeroplane. The present invention is particularly applicable to aircraft that operate with low weight restrictions as the antenna array apparatus described herein is relatively light weight. Other examples include rotorcraft, balloons and airships, specifically those designed for long endurance flight.
The aircraft 100 includes a wing member 106. In one example, the wingspan of the wing member 106 is approximately 35 metres and has a relatively narrow chord (i.e. of the order 1 metre). The wing member 106 is coupled to a fuselage 104. To aerodynamically balance the aircraft 100, a horizontal tail plane 108 and a vertical tail fin (or vertical stabilizer) 110 are coupled to the rear of the fuselage 104. A payload module 102 may be coupled to the front of the fuselage 104, i.e. the nose of the aircraft 100. In one example, the payload module 102 may be detachable from the fuselage 104. The payload module 102 may include the control avionics for controlling the aircraft 100, and/or mission-specific equipment such as explosives, projectiles, sensor equipment, imaging equipment or the like. In one example, the payload module 102 comprises a sensor for gathering data and a radio, wherein the radio is configured to transmit the data using the antenna array 116 described in more detail with reference to later Figures.
An engine having a propeller may be mounted to the wing member 106 on both sides of the fuselage 104. The engines may be powered by a combination of solar panels mounted to the upper surfaces of the wing member 106 and batteries disposed inside the fuselage 104 and/or wing member 106.
HALE aircraft are specifically designed for continuous operations (i.e. about 1 week or more, typically of the order of about 90 days or more, preferably about 1 year or more) at more than 50,000 feet (typically about 60,000 feet). To that end, HALE aircraft are extremely lightweight, typically of the order of less than 200kg. HALE aircraft have very little air resistance in order to maximise energy efficiency. However, HALE aircraft have a large upper surface area, covered substantially in solar panels, to maximise the amount of sunlight captured for powering the engines or charging the batteries. For example, a HALE might have a wingspan of about 35 metres, and a chord of about 1 metre, the cord remaining relatively constant along the whole span. They operate without a pilot, and their functions are typically autonomous or controlled from a ground station. HALE aircraft are also sometimes referred to as High-Altitude Pseudo-Satellites (or HAPS).
Therefore, the aircraft 100 is of lightweight construction. For example, the fuselage 104, wing member 106, payload module 102, tailplane 108 and tail fin 110 may be made of a monocoque carbon fibre laminate skin structure. In other words, the skin forms the aircraft's body. In other embodiments, the body is substantially made of a lightweight metal, such as titanium, titanium alloy, aluminium, aluminium alloy. In one example, the body is made substantially of fiberglass.
In some embodiments, the purpose of the payload module 102 is to capture data through means such as a camera or other sensor. This data needs to be transmitted to a base station, or to another aircraft 100 for relay to a base station, for processing. Therefore, a radio coupled to an antenna array 116, explained in more detail with reference to the following Figures, is used to transmit the data. In further embodiments, for example aircraft 100 that do not include payload modules 102, it can be advantageous to communicate with other aircraft 100. Here, control signals may be relayed from a ground station to the second aircraft 100 by the first aircraft 100 using the radio and antenna array 116 (where the radio and antenna array are distributed throughout the first and second aircraft 100). The antenna array 116 described below is suitable for use with a lightweight aircraft 100 as it enables a relatively high field of regard (i.e. field of view, or antenna coverage) with relatively high gain.
Figure 2 shows an example of an aircraft 100, such as a HALE aircraft including an antenna array 116. In examples, the antenna array 116 is coupled to the payload module 102 of the aircraft 100, but in other examples, the antenna array 116 may be coupled with the fuselage 104 or other components of the aircraft 100. In one example, the antenna array 116 comprises a beamformer 118 for controlling the phase and relative amplitude of the signal at each antenna 112.
Figure 3A shows an example of an antenna 112 in the form of a blade antenna 112a for use in the antenna array 116. In Figure 3A, the blade antenna 112a is coupled to a base plate 114. In one example, the blade antenna 112a is coupled to the base plate 114 via one or more fixtures, such as screws (not shown). Each blade antenna 112a may comprise a SMA or TNC antenna interface for coupling to the base plate 114 and/or one or more other components.
In use, the blade antennas 112a may be coupled to a base plate 114 or may be coupled directly to part of the aircraft 100, such as the payload module 102 of the aircraft 100.
An individual blade antenna 112a is omni-directional in the azimuth plane. That is to say, it radiates equal radio power in all directions perpendicular to an axis, with power varying with angle to the axis, declining to zero on the axis. When graphed in three dimensions this radiation pattern is often described as doughnut-shaped. As such, in the example shown in Figure 3A, the field of the regard is higher in a substantially horizontal direction from the blade antenna 112a compared with a substantially vertical direction. In other words, in operation, the blade antenna 112a would have a higher gain in a substantially horizontal direction compared with a substantially vertical direction.
The blade antennas 112a are substantially aerodynamic such that they do not create significant drag on the aircraft 100, in use.
Other examples of omni-directional antennas include a whip antenna and horizontal loop antenna.
Figure 3B shows an example of a conformal antenna 112b, such as a patch antenna. In Figure 3B, the conformal antenna 112b is coupled to a base plate 114. In use, the conformal antenna 112b may be coupled to a base plate 114 or may be coupled directly to the aircraft 100.
The conformal antenna 112b is configured to conform to the shape of the part to which it is coupled. For example, the conformal antenna 112b in Figure 3B conforms to the shape of the base plate 114. In other words, the shape of the conformal antenna 112b matches the contour of the upper surface of the base plate 114. In other examples, the conformal antenna 112b may conform to the shape of the housing of the payload module 102. In other words, the conformal antenna 112b may be coupled to the outer surface of the housing of the payload module 102 in a substantially flush arrangement.
The conformal antenna 112b may be a patch antenna or a 3D printed antenna. A patch antenna is a type of radio antenna with a low profile, which can be mounted on a flat surface. It may comprise a flat rectangular sheet or "patch" of metal, mounted over a larger sheet of metal called a ground plane. As the patch antenna has a low profile, it creates relatively little drag when coupled or mounted to an aircraft 100.
In one example, the base plate 114 is comprised of a durable metal suitable for conduction, such as aluminium or copper. The base plate 114 may have a substantially non-planar profile in cross section. That is to say, the base plate 114 may be substantially curved across a width of the base plate 114. The base plate 114 influences the broadcast characteristics of the signals transmitted by the antenna array 116. In one example, the antennas 112 are spaced apart at a distance of between approximately 0.05m to 0.3m, more particularly 0.2m. In one example, the baseplate 114 may have a length of between approximately 0.2m to 2m. In one example, the antenna array 116 comprises between four and sixteen blade antennas 112a coupled to the base plate 114.
Figure 4A shows an example of the field of regard of a conformal antenna 112b. The field of regard is approximately between lines A and B, which is approximately hemispherical coverage or approximately 180 degrees. Figure 4B shows an example of the field of regard of a blade antenna 112a. The first field of regard is approximately between lines A1 and B1 and the second field of regard is approximately between lines A2 and B2. In one example, the angle between A1 and B1 is approximately 110 degrees. In one example, the angle between A2 and B2 is approximately 110 degrees. The angle may change depending on the power supplied to the antenna 112a.
Figure 5 shows a front view of an antenna array 116, i.e. this is the profile that would be impinged upon by on-coming air if the antenna array 116 were affixed to the underside of an aircraft 100. In this example, the antenna array 116 comprises a plurality of blade antennas 112a coupled to part of the aircraft 100, for example, the payload module 102 of the aircraft 100. In the example shown in Figure 5, the plurality of blade antennas 112a are coupled to the base plate 114, which in turn may be coupled to the aircraft 100. That is to say that the plurality of blade antennas 112a may be indirectly coupled to the aircraft 100 via a base plate 114. In Figure 5, the base plate 114 is substantially non-planar such that each of the antennas 112 extend in a substantially different direction. The shape of the base plate 114 may match part of the aircraft 100 to which it is coupled. For example, the base plate 114 may be co-planar (or conformal with) a curved underside of the fuselage 104 of the aircraft 100.
As described above, each of the individual blade antennas 112a has a field of regard that is higher in a substantially lateral direction (azimuth plane) from the blade antenna 112a compared with a substantially longitudinal direction (zenith plane) from the blade antenna 112a. Forming an antenna array 116 such that each of the blade antennas 112a extend in different directions means that the field of regard of the antenna array 116 is greater compared with the field of regard of any individual one of the blade antennas 112a. In the example shown in Figure 5, the two blade antennas 112a that are shown at the ends of the antenna array 116 are arranged at an angle of approximately 30 degrees relative to the central blade antenna 112a, which is shown as extending in a substantially vertical direction. The arrangement of the blade antennas 112a that extend at different angles means that the combined field of regard of the antenna array 116 is greater than a field of regard of any individual antenna 112a of the plurality of antennas 112a. In one example, each of the blade antennas 112a extend in a different direction as they project at a substantially perpendicular direction from a non-planar, i.e. curved, base plate 114. This arrangement allows the antennas 112a to be easily arranged together in a manner to create a relatively high gain.
In one example, the base plate 114 may comprise an opening (not shown) to enable it to be coupled to the aircraft 100 by a fixture that extends through the opening. In one example, the base plate 114 is coupled to an underside of the payload module 102 of the aircraft 100.
In the example shown in Figure 5, the antennas 112 comprise blade antennas 112a, but in other examples, they may comprise conformal antenna 112b or a combination of blade antennas 112a and conformal antennas 112b.
The shape of a curved base plate 114 may be arranged to match the curved shape of the payload module 102 fairing such that they couple in a flush arrangement. The curved base plate 114 enables the blade antennas 112a to project from the base plate 114 at different angles, which widens the field of regard of the antenna array 116. In other words, the base plate 114 is non-planar. The provision of an antenna array 116 shown in Figure 5 significantly improves the overall gain compared to the use of a single antenna 112.
The antenna array 116 may be used in two ways to increase the gain and field of regard of the aircraft 100. This can be either by diversity or by beamforming. Antenna diversity means that the plurality of antennas 112 receive a transmission and the different signals can be processed to remove any error or interference in the signals to create a more reliable signal. Error is caused in transmission signals from interference in the atmosphere, weather conditions or objects in the signal path. Antenna diversity allows this error to be overcome. In some examples, the signals from each antenna are analysed and compared with each other to see where there are errors or gaps in the received signal. The data from the other antennas is then used to fill these gaps or estimate what the missing data was. Diversity is important as it increases the quality and reliability of the wireless link.
Beamforming would allow the gain of the antenna array 116 to be focused in the area of interest. The preferred spacing of the antennas 112 to achieve diversity would be a wavelength or a multiple of the wavelength apart. The preferred spacing for a beamforming antenna array 116 would be half a wavelength apart. For the example of a frequency of 1.5 GHz, the wavelength would be approximately 0.2m.
In one example, the antenna array 116 comprises a beamformer 118 for controlling the phase and relative amplitude of the signal at each antenna 112. The beamformer 118 is configured to combine signals from individual antennas 112 in an antenna array 116 in such a way that signals at particular angles experience constructive interference while others experience destructive interference. Beamforming can be used at both the transmitting and receiving ends in order to achieve spatial selectivity.
To change the directionality of the antenna array 116 when transmitting, the beamformer 118 controls the phase and relative amplitude of the signal at each antenna 112, in order to create a pattern of constructive and destructive interference in the wavefront. When the antenna array 116 is receiving data, information from different antennas 112 is combined to form a combined signal. By using a number of different antennas 112, arranged in an array 116, noise can be blocked out and the antenna array 116 may focus specifically on a desired frequency (i.e. a known transmission frequency).
The beamforming technique may involve sending a pulse from each antenna 112 at slightly different times (the antenna 112 closest to the intended direction last), so that every pulse hits the intended object at approximately the same time, producing the effect of a single strong pulse from a single powerful antenna 112.
In passive techniques, and in reception in active signals, the beamforming technique may include combining delayed signals from each antenna 112 at slightly different times so that every signal reaches the output at a similar time.
With narrow-band systems, the time delay is equivalent to a "phase shift". The beamformer 118 may also amplify signals from each antenna 112 by a different "weight" or gain.
The beamformer 118 may use a fixed set of weightings and time-delays (or phasings) to combine the signals from the antenna 112 in the antenna array 116, primarily using only information about the location of the antenna 112 in space and the wave directions of interest. Adaptive beamforming techniques (e.g., MUSIC, SAMV) generally combine this information with properties of the signals actually received by the antenna array 116, typically to improve rejection of unwanted signals from other directions. This process may be carried out in either the time or the frequency domain.
Figure 6 shows an example of an antenna array 116 coupled to the payload module 102. Figure 6 shows a side view of a payload module 102. In Figure 6, the arrows indicate a direction of airflow over the payload module 102. The front of the payload module 102 is the region over which the air initially flows over the payload module 102 (i.e. the left hand side of the payload module 102 in Figure 6) when the aircraft 100 having the payload module 102 is in flight. The rear of the payload module 102 may be considered to be the opposite end of the payload module 102 to the front (i.e. the region toward the right hand side of the payload module 102 in Figure 6).
In this example, the antenna array 116 comprises one or more blade antennas 112a and one or more conformal antennas 112b in the form of a patch antenna. The combination of one or more conformal antennas 112b and one or more blade antennas 112a increases side gain of radio transmissions but also cover the forwards and rearwards areas of the antenna array 116. Conformal antennas 112b may be attached directly to the body (i.e. housing or fairing) of the payload module 102 so they do not interrupt the aerodynamic qualities of the payload module 102.
In Figure 6, four conformal antennas 112b are shown together with a blade antenna 112a. However, in other examples there may be a different number of conformal antennas 112b, for example, there may be between four and sixteen conformal antennas 112b provided. As the payload module 102a has a substantially non-planar surface, each of the conformal antenna 112b will extend in a different direction relative to each other (i.e. oriented differently, therefore having different individual fields of regard).
In Figure 6, the blade antenna 112a is shown at the bottom of the payload module 102 and extends in a direction relatively perpendicular to the surface of the housing of the payload module 102. However, in practice, the blade antenna 112a may be arranged in any position in relation to the payload module 102. In this example, there may be more than one blade antenna 112a provided. In addition, in the example shown in Figure 6, the blade antenna 112a is coupled directly to a base plate 114 that is coupled to the payload module 102, but in other example, the blade antenna 112a may be coupled directly to the payload module 102 or other part of the aircraft 100.
As with the example of Figure 5, each of the antennas 112 are configured to extend in different directions relative to each other such that a field of regard of the antenna array 116 is greater than a field of regard of any individual antenna 112 of the plurality of antennas 112. Arranging one or more of the conformal antennas 112b on the side of the payload module 102 as shown in Figure 6 is good for HAPS-HAPS communications. In one example, one or more conformal antenna 112b may be arranged towards the bottom of the payload module 102 such that the field of regard of the antenna array 116 also extends below the antenna array 116 such that the antenna array 116 can be in communication with ground stations.
The provision of a blade antenna 112a in addition to the conformal antenna 112b means that the field of regard of the antenna array 116 is increased as the blade antenna 112a may cover any regions in front or behind the payload module 102 in the example shown in Figure 6.
A beamformer 118 may be used to focus gain of a plurality of antennas 112 (i.e. conformal antennas 112b and blade antenna 112a) as required. As conformal antennas 112b provide substantially frontal coverage, one or more blade antennas 112a may be used to cover any gaps (directly in front and behind) in conformal antenna 112b coverage.
The provision of an antenna array 116 comprising conformal antennas 112b and/or blade antennas 112a means that the antenna array is substantially lightweight compared with traditional antenna arrays and so can be utilised on HALE vehicles, which have strict weight restrictions. For example, a single conformal antenna 112b may weigh less than 10g, for example 6g. Further, the antenna array 116 would have good aerodynamic qualities and so its presence would not induce significant drag on the aircraft 100 as both blade antennas 112a and conformal antennas 112b have good aerodynamic characteristics.
Figure 7A shows an alternative example of a side view of a payload module 102 comprising an antenna array 116.
In this example, at least one region of the payload module 102 may be formed of an RF transparent material, such as fiberglass or Quartz Fibre skins. For clarity, the housing in Figure 7A is shown as transparent to illustrate the position of antennas 112 and mounts 122, 123 within the payload module 102. The front of the payload module 102 is the region over which the air initially flows over the payload module 102 (i.e. the left hand side of the payload module 102 in Figure 7A). The rear of the payload module 102 may be considered to be the opposite end of the payload module 102 to the front (i.e. the region toward the right hand side of the payload module 102 in Figure 7A).
In one example, one or more conformal antennas 112b are embedded within the region of RF transparent material of the payload module 102 may be formed of an RF transparent material. That is to say that they do not protrude or project from the surface of the payload module 102 but are rather within the skin of the payload module 102. Conformal antennas 112b would be particularly suited to being embedded with the RF transparent material of the payload module 102 as they have a relatively small thickness. Alternatively, instead of being embedded in the skin of the housing, the conformal antennas 112b may be coupled to an inside surface of the housing of the payload module 102. Here, the conformal antennas 112b are disposed beneath the RF transparent material.
In one example, substantially all of the payload module 102 fairing (i.e. housing) comprises an RF transparent material. In the illustrated embodiment, substantially all of the payload module 102 comprises the RF transparent material. However, it would be appreciated that in other embodiments the RF transparent material may be disposed one at the front and/or rear of the payload module 102, or in a region on the ventral side.
In effect, the RF transparent material allows antennas 112 to be disposed inside the payload module 102, while maintaining uninterrupted transmission and reception of signals. Meanwhile, the antennas 112 mounted inside the payload module 102 do not induce drag on the payload module 102 while it is in use.
In the example shown in Figure 7A, the payload module 102 comprises an internal structure, such as mountings 122, 123 to which one or more antennas 112 may be coupled. The antennas 112 located within the payload module 102 are able to transmit and/or receive signals through the RF transparent surface of the payload module 102 with substantially no loss.
In one example, the payload module 102 comprises a front facing mounting 122 and a rear facing mounting 123. One or more front-facing antennas 112b can be coupled to the front facing mounting 122 and one or more rearward facing antennas 112b can be coupled to the rearward-facing mounting 123. This arrangement enables the antenna array 116 to have a substantially full field of operation.
In the example of Figure 7A, the payload module 102 is a podded module. The payload module 102 may be coupled to the underside of a wing 106 of the aircraft 100, for example, instead of the front of the fuselage 104 as illustrated in Figures 1 and 2. In other embodiments, the payload module 102 is coupled to the underside or top side of the fuselage 104 of the aircraft, and may be conformal with the skin of the aircraft 100. Alternatively, the payload module 102 may be coupled to the aircraft 100 by way of a pylon or bracket.
One or more blade antennas 112a may be coupled to the payload module 102. In some examples, the one or more blade antennas 112a are coupled to the payload module 102 via a base plate 114, for example as shown in Figure 5. In one example, the payload module 102 may be conformal with an underside or side of the fuselage 104 of the aircraft 100.
Figure 7B shows one example of a front-on view of the payload module 102 comprising a plurality of conformal antennas 112b. The front of the payload module 102 is substantially curved and so each of the conformal antennas 112b coupled to the front of the payload module 102 extends in a substantially different direction. Each of the individual conformal antennas 112b has an individual field of regard and so arranging them to point in different directions as shown in Figure 7B means that the overall field of regard of the antenna array 116 is substantially greater than a field of regard of any one of the individual conformal antennas 112b.
This arrangement of conformal antennas 112b as shown in Figure 7B may be used in combination with the antenna arrangement as shown in Figure 6 to provide an antenna array 116 with a wide field of regard.
In the example shown in Figure 7B, there are 17 conformal antennas 112b shown at the front of the payload module 102, but, in other examples, there may be between 1 to 20 conformal antennas used at the front of the payload module 102. Figure 7C shows a side view of a payload module 102 with an antenna array 116 in which the rear side of the payload module 102 is substantially flat. In this example, one or more antennas 112b may be located on the surface of the rear face of the payload module 102. In other words, Figure 7C is substantially similar to the payload module 102 shown in Figure 7A, but with a substantially flat rear face. The payload module 102 comprises a mechanical interface for coupling to the front of an aircraft 100.
The location of the antennas 112 on the payload module 102 is dependent on the required direction of coverage (i.e. field of regard). For communication between a plurality of aircraft 100, i.e. HALE-to-HALE communication and data transfer, the ideal location of the antennas 112 would be on the side of the payload module 102 facing horizontal towards the horizon. The ideal location for the antennas 112 for ground communication would be on the underside of the payload module 102.
In one example, one or more conformal antennas 112b are printed on the surface of the payload module 102 or printed within the surface of the payload module 102, for example, embedded within the structure of the payload module 102 (i.e. disposed inside the fairing). For example, the one or more conformal antennas 112b comprises printed antennas that are coupled with the surface or embedded within the surface of the payload module 102.
In the example of the one or more conformal antennas 112b printed on the surface of the payload module 102, the payload module 102 material may be made of fiberglass, which is not conductive. Printing of the one or more conformal antennas 112b would increase weight savings on the aircraft as well as gain without compromising the aircraft aerodynamics.
In one example, frequency ranges that the antenna array 116 would be likely to operate in are about 1.4-1.5 GHz and about 47-48 GHz.
Where, in the foregoing description, integers or elements are mentioned that have known, obvious, or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present disclosure, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the disclosure that are described as optional do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, while of possible benefit in some embodiments of the disclosure, may not be desirable, and can therefore be absent, in other embodiments.

Claims

An antenna array for a High-Altitude Long Endurance aircraft, the antenna array comprising:
a plurality of antennas arranged to extend in different directions relative to each other such that a field of regard of the antenna array is greater than a field of regard of any individual antenna of the plurality of antenna.
The antenna array according to claim 1, wherein one or more of the plurality of antennas comprise a blade antenna.
The antenna array according to claims 1 or 2, wherein the antenna array comprises a base plate to which the antennas are coupled.
The antenna array according to claim 3, wherein the base plate is substantially non-planar.
A payload module for a High-Altitude Long Endurance aircraft, the payload module comprising:
a housing; and

an antenna array according to any one of the preceding claims coupled to or disposed inside the housing.
The payload module according to claim 5, comprising a sensor for gathering data and a radio, wherein the radio is configured to transmit the data using the antenna array.
The payload module according to claim 5 or claim 6, wherein one or more of the plurality of antennas comprises a conformal antenna arranged to conform to a surface of the housing.
The payload module according to claim 7, wherein the one or more conformal antennas are printed on the surface of the housing.
The payload module according to any one of claims 5 to 8, wherein the housing comprises at least one region of radio frequency transparent material.
The payload module according to claim 9 when dependent on claim 7, wherein the one or more conformal antennas are embedded within the region of radio frequency transparent material of the housing.
The payload module according to claim 9 or claim 10, comprising a mount disposed inside the housing, wherein at least one of the plurality of antennas is coupled to the mount.
The payload module according to any one of claims 7 to 11, wherein the conformal antenna comprises a patch antenna.
A High-Altitude Long Endurance aircraft comprising the antenna array according to any one of claims 1 to 4.
The High-Altitude Long Endurance aircraft according to claim 13 when dependent on claim 3 or claim 4, comprising a fuselage, wherein the antenna array is coupled to the fuselage and wherein the shape of the base plate matches the shape of the fuselage.
A High-Altitude Long Endurance aircraft, comprising the payload module according to any one of claims 5 to 12.