HORIZONTALLY POLARIZED BROADBAND ANTENNA

Abstract

The invention relates to an antenna arrangement (1), comprising an antenna mounted within a radome (3). The antenna arrangement (1) further comprises a mounting arrangement for mounting the antenna arrangement (1) on an antenna platform (7a, 7b, 7c). The antenna is a tapered slot antenna (2), the radome (3) has an aerodynamic shape, and the mounting arrangement comprises two antenna clamping means (5) and an antenna radio frequency connector (6) arranged to interface with corresponding antenna platform clamping means (7a, 7b, 7c) and an antenna platform radio frequency connector disposed on the antenna platform (7a, 7b, 7c).

Description

HORIZONTALLY POLARIZED BROADBAND ANTENNA TECHNICAL FIELD The invention relates to an antenna arrangement comprising an antenna mounted within a radome. The antenna arrangement further comprises a mounting arrangement attached to the dome, designed to mount the antenna arrangement on an antenna platform. The invention also relates to a method for receiving and transmitting horizontally polarized radio frequency signals propagating perpendicular to the direction in which an antenna platform is moving. PREVIOUS TECHNIQUE Vehicle-mounted radio frequency (RF) antennas can be used for a variety of applications. One area of ​​application is radar, such as air and ground traffic control, marine radar for locating landmarks and other ships, radar astronomy, and various defense applications. Another application is electronic warfare (EW), where RF antennas use the electromagnetic (EM) spectrum to control the spectrum, attack an enemy, or prevent enemy attacks. The purpose of electronic warfare is to deny the opponent the advantage and ensure friendly and unhindered access to the EM spectrum. EW can be deployed from air, sea, land, and / or space platforms, whether manned or unmanned, and can target humans, communications, radar, or other assets. The most common vehicle-mounted antenna for very high frequency (VHF) and ultra high frequency (UHF) radio frequencies is the leaf antenna. A monopole antenna, such as a leaf antenna, is housed within a radome. It is well known that the monopole antenna has a doughnut-shaped radiation pattern around the z-axis, such that there is complete coverage in the xy-plane but no coverage in the ±z direction; see, for example, C.A. Balanis, Antenna Theory, Analysis and Design, ISBN 9781118642061. The leaf antenna is polarized in the z-direction. Therefore, vehicle-mounted blade antennas can be used to achieve vertical polarization with full 360° coverage in a horizontal plane relative to a vehicle, such as an airplane. Horizontal polarization, on the other hand, can primarily be used in the forward or rearward directions when using conventional blade antennas, but not to the sides of the vehicle. In the example of an aircraft, one method for achieving horizontal polarization with respect to the aircraft's horizontal plane is to mount a horizontally polarized dipole at a certain distance above the aircraft's metal fuselage. This approach has two challenges. First, it requires a distance of a quarter of a wavelength from the metal ground plane, which is challenging due to the long wavelength at VHF frequencies. Another challenge is the low radiation efficiency in the horizontal plane, due to image current in the ground plane. In Daniel Sievenpiper et al., High-Impedance Electromagnetic Surfaces with a Forbidden Frequency Band, IEEE Transactions on Antennas and Propagation, Volume 47, Number 11, November 1999, a method for reducing the distance over the ground plane was presented; to the applicant's knowledge, this configuration has not achieved commercial use for aeronautical applications due to the narrow bandwidth and size requirements for the high-impedance ground plane. Another solution was presented in Lúea Scorrano et al., Dual-polarization DF Array for airborne SIGINT in VHF / UHF bands, Proceedings of the 44th European Microwave Conference, 8-10 October 2014. Similar to the leaf antenna, this antenna is narrowband, resulting in insufficient radiation efficiency at lower frequencies for certain applications, and performance is limited by the distance from the ground plane. Another method for achieving horizontal polarization towards the side of the aircraft would be to place patch antennas on the side of the aircraft structure. However, patch antennas require a relatively large area on the side of the aircraft, even though they are narrowband. WO 2019 / 143275 A1 discloses an antenna installation with log-periodic antennas. With this configuration, horizontal polarization can be achieved, but only in the forward or rearward directions relative to the aircraft. Therefore, there is a need for an improved antenna arrangement intended to provide reception and transmission of horizontally polarized RF waves, with high radiation efficiency over a wide bandwidth. BRIEF DESCRIPTION An objective of this invention is to provide an antenna arrangement that addresses the problems described above. This objective is achieved through the technical features contained in the characterizing portion of independent claims 1 and 9. The dependent claims contain beneficial embodiments, further developments, and variants of the antenna arrangement. For reference, a local x, y, z (lowercase) coordinate system is used for the antenna array, where the x-axis is the longitudinal axis, the y-axis is the transverse axis, and the z-axis is the vertical axis. An X, Y, Z (uppercase) coordinate system is used for the antenna platform on which the antenna array is installed, where the x-axis is the vertical axis, the y-axis is the transverse axis, and the z-axis is the longitudinal axis. The invention relates to an antenna arrangement comprising an antenna mounted within a radome. The antenna arrangement further comprises a mounting arrangement for mounting the antenna arrangement on an antenna platform. The antenna arrangement is characterized in that the antenna is a tapered slot antenna, the radome has an aerodynamic shape, and the mounting arrangement comprises two antenna clamping means and an antenna radio frequency connector arranged to interface with the corresponding antenna platform clamping means and an antenna platform radio frequency connector disposed on the antenna platform. The most common installation configuration for blade antennas is vertical mounting, either on the upper or lower surface of an aircraft, with the antenna's z-axis aligned with the antenna's x-axis. This configuration achieves complete RF coverage in the horizontal YZ plane with vertical polarization. This is a common type of installation for radio communication antennas. When blade antennas are installed with the z-axis in the horizontal YZ plane, aligned with the Y-axis of the antenna pad, horizontal polarization is achieved. However, due to the doughnut-shaped radiation pattern, this will only result in coverage in the directions forward and aft of the aircraft. Coverage to the sides of the antenna pad, such as an aircraft, cannot be achieved with this antenna configuration. This configuration can be used for Instrument Landing Systems (ILS), where horizontal polarization in the forward direction is required. However, for electronic warfare applications, it would be highly beneficial to have horizontal polarization and radiation along the positive and negative Y axes, or propagation perpendicular to the direction in which an antenna platform to which the antenna array is attached is moving. An example application for the antenna array is for an airborne electronic warfare platform (κη Lrnn / eznz / B / YiAi) traveling in a racetrack flight pattern, where the antenna array can be used for both jamming and surveillance of potential threats. The antenna arrangement used in this invention is a tapered slot antenna mounted in a radome, such that its mechanical and aerodynamic design resembles a previously known leaf antenna. Therefore, the external appearance of the antenna arrangement will be similar to a leaf antenna. Since the tapered slot antenna is an end-firing antenna, the radiation pattern will have a maximum in the y-direction and will be polarized along the y-axis. The bandwidth and gain of the tapered slot antenna are greater than the bandwidth and gain of the leaf antenna. The antenna arrangement according to the invention meets the following specification: 1. Horizontal polarization, with coverage in the z direction of the antenna arrangement, so that coverage of the side of an antenna platform such as an aerial vehicle, a ground vehicle or a surface vehicle can be achieved. 2. An antenna with a large bandwidth 3. The antenna arrangement provided is easy to install. 4. The provided antenna arrangement has an aerodynamic profile 5. The provided antenna arrangement has high radiation efficiency and low return loss. Any reduction function can be used for the conical slot antenna, such as for example a conical exponential slot antenna, a conical linear slot antenna, a continuous width slot antenna, a conical exponentially conical double slot antenna, a stepped slot antenna, a stepped constant conical slot antenna, a tangential conical slot antenna, a parabolic conical slot antenna, a linear constant conical slot antenna, an exponential constant conical slot antenna, or a broken line conical slot antenna. Depending on the desired antenna characteristics in the antenna arrangement, a variety of tapered slot configurations can be selected. The radome material can be, for example, plastic, composite glass, fiberglass, or quartz. The radome material can become part of the antenna array. Depending on the desired characteristics of the antenna array, the permittivity of the material can be matched to the material chosen for the radome. The antenna size can be adjusted, for example, by adjusting the permittivity of the radome. The antenna platform can be an airborne vehicle, for example, an airplane or an unmanned aerial vehicle, wherein the antenna arrangement is disposed on an essentially vertical surface of the airborne vehicle, such that the antenna arrangement is arranged to receive and transmit radio frequency signals that are horizontally polarized and propagate perpendicular to the direction in which the antenna platform is moving. As previously stated, an antenna arrangement according to the invention is beneficial for electronic warfare platforms such as an aircraft flying in a racetrack flight pattern, where it can be used for both range-locking and surveillance of potential threats. The unmanned aerial vehicle can be an unmanned combat aerial vehicle. The antenna platform can also be a manned or unmanned ground vehicle. The antenna platform can also be a manned or unmanned surface vehicle, for example, a manned or unmanned warship or vessel. Other types of electronic warfare platforms, such as armored vehicles and surface vehicles like ships and boats, can also utilize an antenna platform according to the invention. Antenna platforms can be manned or unmanned, i.e., an unmanned ground vehicle or an unmanned surface vehicle. The antenna and platform radio frequency connectors can be SubMiniature version A coaxial connectors. To facilitate installation, the antenna array and antenna platform include matching RF connectors. One example of an RF connector is a SubMiniature Coaxial Connector (SMA), which offers ease of use and good characteristics for the RF used. Alternatives to SMA connectors include SubMiniature Coaxial Connectors (SMC), Bayonet Neill-Concelman (BNC) connectors, Threaded Neill-Concelman (TNG) connectors, and N-type connectors. The invention also relates to an antenna assembly, comprising a multitude of antenna arrangements as described above. The antenna assembly is formed because the antenna arrangements are arranged essentially along the same linear extent of an antenna platform, or in a pattern where at least some of the antenna arrangements are separated along the Z-axis of the antenna platform. Multiple antenna arrays can be mounted, for example, along an aircraft to form an antenna array. An antenna array can be used for direction finding (DF) in electronic surveillance (ES) and / or to achieve high gain for electronic attack (EI). The invention also relates to a method for receiving and transmitting horizontally polarized signals radiating along the positive and negative Y axes, wherein the method comprises: - providing an antenna arrangement by mounting a tapered slot antenna inside an aerodynamically shaped radome, - further provide the antenna arrangement with a mounting arrangement comprising two antenna fixing means and an antenna radio frequency connector, - to arrange, on a vertical surface of an antenna platform, antenna platform clamping means and antenna platform radio frequency connector arranged to interact with the antenna clamping means and antenna radio frequency connector, κη Lrnn / eznz / B / YiAi - Attach the antenna array to the antenna platform and connect the antenna array to a control system via the antenna radio frequency connector and the antenna platform radio frequency connector. The method provides the advantages described above. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 schematically shows an antenna arrangement of the prior art. Figure 2 schematically shows an antenna arrangement according to the invention. Figure 3a schematically shows an airplane-shaped antenna platform with an antenna arrangement according to the invention. Figure 3b schematically shows an airplane-shaped antenna platform with an array of antennas according to the invention. Figure 4 schematically shows an antenna platform in the shape of an airplane traveling in a racetrack flight pattern. Figure 5 schematically shows a land vehicle-shaped antenna platform with an antenna arrangement according to the invention. Figure 6 schematically shows a surface vehicle-shaped antenna platform κη Lrnn / eznz / B / YiAi with an antenna arrangement according to the invention. κη Lrnn / eznz / B / YiAi DETAILED DESCRIPTION In the figures, an antenna is defined by a coordinate system x, y, z (lowercase), where the x-axis is the longitudinal axis, the y-axis is the transverse axis, and the z-axis is the vertical axis. An antenna platform is defined by a coordinate system X, Y, Z (uppercase), where the x-axis is the vertical axis, the y-axis is the transverse axis, and the z-axis is the longitudinal axis. Figure 1 schematically shows a prior art blade antenna arrangement 101. The prior art antenna arrangement 101 comprises a shaped monopole antenna 102 housed within a radome 103. The radome is normally opaque to optical frequencies but not to RF frequencies, and its edges are therefore delineated with dash-dot lines. The blade antenna 102 is mounted on a ground plane 104 and is arranged for mechanical connection by means of two antenna clamping means 105 and for electronic connection by means of an antenna RF connector 106 to an antenna platform such as an aircraft (not shown). The prior art antenna arrangement 101 is a common aircraft-mounted antenna for VHF and UHF radio frequencies and is described in the background. The advantages of a leaf antenna 102 are its ease of installation, exemplified by the two screws acting as antenna fastening means 105 shown in Figure 1, and the aerodynamic profile of the radome 103. However, the leaf antenna 102 does not provide horizontal polarization or propagation perpendicular to the direction in which an antenna platform to which the antenna arrangement is attached is moving. For simplicity, the antenna feed and other known details necessary for the antenna's operation are not shown. Figure 2 schematically shows an antenna arrangement 1 according to the invention. In the antenna arrangement 1 of Figure 2, the leaf antenna 102 of Figure 1 has been replaced by a tapered slot antenna 2 mounted on a ground plane 4. Furthermore, a radome 3 has an aerodynamic shape. A mounting arrangement comprises two antenna clamping means 5 and an antenna radio frequency connector 6 arranged to interface with corresponding antenna platform clamping means (not shown) and an antenna platform radio frequency connector (not shown) arranged on an antenna platform (not shown). Since the conical slot antenna 2 is an end-firing κη Lrnn / eznz / B / YiAi antenna, the radiation pattern will have a maximum in the z-direction and will be polarized along the y-axis. The bandwidth and gain obtained, or radiation efficiency, of the conical slot antenna 2 are greater than those of the leaf antenna, which gives rise to several advantages over the antenna arrangement 1 of the prior art in Figure 1. Several variations of tapered slot antennas 2 with antenna arrangement 1 according to the invention can be used, depending on the desired characteristics. For simplicity, the antenna feed and other known details necessary for the antenna's operation are not shown. Figure 3a schematically shows an airplane-shaped antenna platform 7a with an antenna arrangement 1 according to the invention. Figure 3a shows an example of the location of an antenna arrangement 1 on an airplane to utilize the advantages provided by the antenna arrangement 1, namely, a radiation pattern in the z-direction from the tapered slot antenna 2 with polarization along the y-axis. Figure 3b schematically shows an aircraft-shaped antenna platform 7a with an antenna array 8 according to the invention. Several antenna arrays 1 can be installed along an aircraft to form an antenna array 8 according to Figure 3b. An antenna array 8 can be used for direction finding (DF) in electronic surveillance (ES) and for achieving high gain for electronic attack (EA). Figure 4 schematically shows an antenna platform 7a in the form of an aircraft flying in a racetrack flight pattern. The antenna arrangement 1 and / or antenna array 8 is beneficial for electronic warfare (EW) and signals intelligence aircraft. Antenna arrangements 1 that meet criteria 1 through 5 above are of interest for racetrack flying, as they are used for both jamming and surveillance. In Figure 4, a number of threats 9 are shown within range of the antenna arrangement 1 and / or antenna array 8, and independent jamming and / or surveillance can be carried out on the threats 9, as indicated by the arrow. The arrow symbolizes signal reception and transmission. Figure 5 schematically shows a ground vehicle-shaped antenna platform 7b with an antenna arrangement 1 according to the invention. Similar to the airborne antenna platform 7a of Figure 4, a ground antenna platform 7b can benefit from having one or more antenna arrangements 1 installed as described above. Although only one antenna arrangement is shown, it should be understood that the antenna platform 7b can alternatively comprise a linear antenna array 8 according to Figure 3b. Figure 6 schematically shows a surface vehicle-shaped antenna platform 7c with an antenna arrangement 1 according to the invention. Similar to the airborne antenna platform 7a of Figure 4 and the ground antenna platform 7b of Figure 5, a surface vehicle may benefit from having one or more antenna arrangements 1 installed as described above. Although only one antenna arrangement is shown, it should be understood that the antenna platform 7c may alternatively comprise a linear antenna array 8 according to Figure 3b. In other words, antenna platforms 7a, 7b, and 7c are suitable for implementing a method for receiving and transmitting radio frequency signals with horizontal polarization and propagation perpendicular to the direction in which an antenna platform (7a, 7b, 7c) is moving. The method comprises: - provide an antenna arrangement 1 by mounting a tapered slot antenna 2 inside an aerodynamically shaped radome 3, - further provide to antenna arrangement 1 a mounting arrangement comprising two antenna clamping means 5 and an antenna radio frequency connector 6, - to have, on a vertical surface of an antenna platform 7a, 7b, 7c, antenna platform fastening means 7a, 7b, 7c and antenna platform radio frequency connector arranged to interact with the antenna fastening means 5 and the antenna radio frequency connector 6, - attach antenna arrangement 1 to antenna platform 7a, 7b, 7c and connect antenna arrangement 1 to a control system via antenna radio frequency connector 6 and antenna platform radio frequency connector. The control system is an RE system, for example, an electronic warfare system and / or a radar system. In the context of the invention, aerodynamic shape means that the shape of the radome 3 reduces drag as it passes through the air compared to a non-aerodynamic shape. Examples of radomes 3 with aerodynamic shapes can be seen in US patent 4,072,952 A and are available from various blade antenna manufacturers. The tapered slot antenna 2 can be printed or etched onto a microstrip-fed substrate, or printed or etched onto a dielectric substrate with Rn Lrnn / eznz / B / YiAi strip line feed, made of a metal layer with microstrip feed, printed or engraved on a substrate with differential feed, made of a metal layer with differential feed. The stepped slot antenna is also known as a notched element. As will be understood, the invention is subject to modification in several obvious respects, all without departing from the scope of the appended claims. Consequently, the drawings and the invention should be considered illustrative and not restrictive in nature.

Claims

1. An antenna arrangement (1), comprising an antenna mounted within a radome (3), the antenna arrangement (1) further comprising a mounting arrangement attached to the radome (3) arranged for mounting the antenna arrangement (1) on an antenna platform (7a, 7b, 7c), characterized in that: - the antenna is a tapered slot antenna (2), - the radome (3) has an aerodynamic shape, and - the mounting arrangement comprises two antenna clamping means (5) and an antenna radio frequency connector (6) arranged to interface with the corresponding antenna platform (7a, 7b, 7c), clamping means and an antenna platform radio frequency connector arranged on the antenna platform (7a, 7b, 7c).

2. The antenna arrangement (1) according to claim 1, wherein the tapered slot antenna (2) is an exponential tapered slot antenna, a linear tapered slot antenna, a continuous width slot antenna, a dual exponential tapered slot antenna, a stepped slot antenna, a stepped constant tapered slot antenna, a tangential tapered slot antenna, a parabolic tapered slot antenna, a linear constant tapered slot antenna, an exponential constant tapered slot antenna, or a broken line tapered slot antenna.

3. The antenna arrangement (1) according to claim 1 or 2, wherein the radome material (3) is, for example, plastic, composite glass, fiberglass, or quartz.

4. The antenna arrangement (1) according to any of the preceding claims, wherein the antenna platform (7a) is an aerial vehicle, for example an airplane or an unmanned aerial vehicle, wherein the antenna arrangement (1) is arranged on an essentially vertical surface of the airborne vehicle such that the antenna arrangement (1) is arranged to receive and transmit radio frequency signals that are horizontally polarized and propagate perpendicular to the direction in which the antenna platform (7a) is moving.

5. The antenna arrangement (1) according to any of claims 1-3, wherein the antenna platform (7b) is a manned or unmanned ground vehicle, wherein the antenna arrangement (1) is arranged on an essentially vertical surface of the manned or unmanned ground vehicle such that the antenna arrangement (1) is arranged to receive and transmit radio frequency signals that are horizontally polarized and propagate perpendicular to the direction in which the antenna platform (7b) is moving.

6. The antenna arrangement (1) according to any of claims 1-3, wherein the antenna platform (7c) is a manned or unmanned surface vehicle, for example, a manned or unmanned boat, wherein the antenna arrangement (1) is arranged on an essentially vertical surface of the manned or unmanned surface vehicle such that the antenna arrangement (1) is arranged to receive and transmit radio frequency signals that are horizontally polarized and propagate perpendicular to the direction in which the antenna platform (7c) is moving.

7. The antenna arrangement (1) according to any of claims 4-6, wherein the antenna radio frequency connectors (6) and the platform radio frequency connectors are SubMiniature version A coaxial connectors.

8. An antenna assembly (8), comprising a multitude of antenna arrangements (1) according to any of the preceding claims, wherein the antenna arrangements (1) are arranged essentially along the same linear extent of an antenna platform (7a, 7b, 7c).

9. A method for receiving and transmitting horizontally polarized radio frequency signals propagating perpendicular to a direction in which an antenna platform (7a, 7b, 7c) is moving, wherein the method comprises: providing an antenna arrangement (1) by mounting a tapered slot antenna (2) within an aerodynamically shaped radome (3), further providing the antenna arrangement (1) with a mounting arrangement comprising two antenna fixing means (5) and an antenna radio frequency connector (6), arranging antenna platform fixing means (7a, 7b, 7c) and an antenna platform radio frequency connector on a vertical surface of an antenna platform (7a, 7b, 7c) arranged to interact with the antenna fixing means (5) and the antenna radio frequency connector (6), and fixing the antenna arrangement (1) to the antenna platform (7a, 7b, 7c).7c) and connect the antenna arrangement (1) to a control system via the antenna radio frequency connector (6) and the antenna platform radio frequency connector.

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