WO2015001425A2

WO2015001425A2 - Airborne antenna system with controllable null pattern

Info

Publication number: WO2015001425A2
Application number: PCT/IB2014/001945
Authority: WO
Inventors: Kevin Le
Original assignee: Powerwave Technologies S.A.R.I.
Priority date: 2013-07-01
Filing date: 2014-07-01
Publication date: 2015-01-08
Also published as: EP3017502A2; EP3017502B1; WO2015001425A8; CN105264712A; WO2015001425A3

Abstract

A system configured to provide airborne antenna functionality through the application of a controllable null pattern. Coupled to a transceiver, the antenna of the invention is operable in the same frequency band with other transmit and receive antennas mounted in near proximity on an aircraft body. The antenna radiation pattern is varied so that the antenna radiation main beam direction can be controlled over a defined range. The antenna system addresses problems associated with proximate antenna interference by forming the transmit (or receive) antenna- radiation beam shape away from other antennas so as to mitigate nearby transmitter interference, while improving receive system performance without having power reduction requirement from nearby co- located, co-band operating transmitters. This is accomplished through electrical and mechanical tilt of the antenna.

Description

AIRBORNE ANTENNA SYSTEM WITH CONTROLLABLE NULL PATTER

BACKGROUND OF THE INVENTION L Field of the Invention.

[00011 The present application, generally relates to a system for adjusting antenna pattern having a vertical poIari¾aiiom omni -directional radiation pattern.

2, Description of the Prior Art

[0002] Existing antenna systems located on aircraft to enable wireless communications are difficult to implement to full effect as a esu of their operating environment When operated in receive mode, the antenna is configured for receiving signals in the line of sight either from ground or other aircraft- However, reception of signals from other aircraft mounted transmit antennas is highly undesirable. Filtering or notching of these nearby transmitted signals Is not possible due to a number of operational factors. Output pow r reduction of offending

transmitters renders communication links inoperable since these nearby antennas cannot provide adequate coverage area on the ground and air to air. Implementation of conventional large metallic structures to reduce inter antenna interference on the aircraft body is not readily possible due to a number of factors such as aerodynamic constraints, visual appearance, and regulatory requirements.

[0003] What is needed is an airborne antenna system that resolves the problems providing sufficient signal strength while addressing interference considerations experienced on aircraft

SUMMARY OF T HE INVENTION

[0004] The present invention Is a system configured, to provide airborne antenna functionality through the application of a controllable null pattern, Coupled to a transceiver, the antenna of the Invention is operable In the same frequency hand -with other transmit and receive antennas mounted in. near proximity on the aircraft body. In a particular operational configuration the antenna radiation pattern is varied so that the antenna radiation main beam direction can be controlled over a defined range. The present antenna system addresses the aforementioned problems of interference, signal strength and structural limitations by forming the transmit (or receive) antenna radiation, beam shape away from the transmitter antenna so as to mitigate

I nearby ransmitter interference, while Improving receive system performance without having power reduction .requirement from nearby co-located, co-band operating transmitters,

[0005] The invention provides an omnidirectional coverage antenna having a controlled elevation radiation pattern so as provide signal reduction .from co-located, co-band operating transmitters mounted on an airborne platform, in an embodiment, the receive antenna is adapted to reduce the interference by combining electrical down ii.lt with a reverse mechanical up hit by creating an augmented elevation, plane downward pointing pattern with a deep null oriented toward nearby transmit antennas.

[0006] Advantages of the invention can further be found in the following description, the accompanying drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Fig, I shows an airborne platform (fixed wing, hut can he rotor as well) used with the present antenna.

[0008] Fi g. 2 is a side view of ao airborne platform showing detail of the placement of the composite Transmit (TX Receive (RX) antenna relative to other dedicated transmit antennas mounted on the airframe.

[0009] Fig, 3 is a block diagram representing functional blocks of TX^'-RX antenna and dedicated TX antennas mourned on the aircraft.

[00101 Fig. 4 is a diagrammatic .representat on of the TX-RX antenna combining mechanical and electrical tilt, to achieve radiation pattern null relativ to dedicated TX antennas mounted on the aircraft,

[001 1 ] Fig. 5 shows an antenna 3-D radiation pattern with, a center donut representing the main lobe of the anten pattern,

[001.2] Fig. 6 shows an antenna 3-D radiation pattern tilted down slightly to the left due to mechanical tilt of the antenna center axis with the center donut representing the main lobe of the antenna pattern..

[0013] Fig. 7 shows an antenna 3-D radiation pattern tilted down slightly to the left due to mechanical tilt and combined with the effect of the electrical tilt (bottom most side lobes are attenuated) with the center donut representing the main lobe of the antenna pattern. [001.4] Figs.. 8A and SB provide comparisons of elevation radiation patterns (2D) due to electrical and mechanical, tilts (not combined.).

[001 S] Fig, 9 is a representation of radiation elevation patterns (2D) due to a resulting combination of electrical and mechanical tilts at -90 deg with the deep null that provides receiver overload, protection from nearby transmit antennas.

[0016] Figs. 10Λ- IOC provide comparisons of the antenna's azimuth radiation patterns (2D) due to electrical, mechanical and combined tilts.

DETAILED DESCRIPTION OF THE INVENTION

[001 ?] A system of the pres nt invention for providing an airborne antenna with a controllable null pattern is shown in. FIGS. 1-3, The system is embodied in tillable antenna 14, which is affixed to underside 16 of the fuselage of aircraft 10. The antenna 14 is a transmit and receive antenna, and it may be a tri-band antenna as shown, it is spaced from an existing dedicated transmit antenna 12 of the aircraft 10 by distance S, The antenna 14 is coupled to a transceiver configured to generate and receive signals in a frequency range of interest. The antenna may be shielded f om impingement such as with cowl 17. An example of a suitable transceiver is represented in PIG. 3 as transceiver 1 H. The transceiver IS includes an S-hand receiver filter circuit, a C-hand receiver filter circuit and an S-band transmit fil er circuit.. The dedicated transmit antenna 12 may he a combination of two or more antennas, such as antennas 12-1 and 12-2, each, of which is separately coupled to an S-band transmit filter circuit, either o.r both of which may be co-banded with the transmit and/or receive hands of the antenna 14.

[00 I S] As show in FIG. 4, the antenna 1.4 can be configured with, an electrical tilt, a mechanical tilt or a combination of the two. The antenna 14 is adapted to reduce from, relatively closely located, transmit antennas such a¾ antenna 1.2 Interference by combining electrical down tilt with a reverse mechanical up tilt. That configuration creates an augmented elevation plane downward pointing pattern with a deep null oriented, toward nearby transmit antennas. That is, through selection of the configuration, of the signal transmitted by the transceiver 18, electrical tilt resulting in the radiation patterns shown in FIGS, 5, 8A and IDA, That, adjusts the lobe positioning in the way shown., Through, mechanical movement of the antenna 1 , mechanical til t of the antenna 1.4 is achieved, such, as through joining the antenna 14 to a controllable motor. That mechanical tilt also changes the lobe positioning to generate the radiation patterns shown in FIGS. 6, 8B and 10B. The combination of both electrical down tilt and reverse mechanical up till produces the radiation patterns represented in FI^'GS. 7, 9 and I OC. It can be seen in FIGS. 9 and I C that the combination of mechanical and electrical tilt generate a null pattern substantially aligned with the direction of antenna 12. As a resu interference is minimized without excessive signal boost or additional structural elements.

OOi 9} While the present invention has been described with respect to a specific embodiment, it is to be understood that variants may be included as aspects of the invention described by the following claims.

Claims

1. An airborne antenna system comprising;

an omm directional coverage antenna attachable to an aircraft fuselage: and

a transceiver coupled to the antenna,

wherein the antenna is arranged for one or both, of electrical, tilt and mechanical tilt.

2. The antenna system of Claim I, wherein the antenna is arranged for one or both of electrical down tilt and mechanical up tilt,

3. The antenna system of C aim 2, wherein the antenna is eonfignred to create an augmen ed elevation plane downward pointing pattern with a deep nuli set oriented toward a nearby second antenna also attachable to the aircraft fuselage spaced trom the coverage antenna.

4. The antenna system of Claim 3, wherein the second antenna is a dedicated transmit antenna.

5. lite antenna system of Claim X wherein the second antenna comprises a plurality of dedicated transmit antennas.