EP1564843A1

EP1564843A1 - Circular polarised array antenna

Info

Publication number: EP1564843A1
Application number: EP04003076A
Authority: EP
Inventors: Kao-Cheng Huang; Stefan Koch
Original assignee: Sony International Europe GmbH
Current assignee: Sony Deutschland GmbH
Priority date: 2004-02-11
Filing date: 2004-02-11
Publication date: 2005-08-17

Abstract

The invention relates to a circular polarised array antenna comprising groups (6) of at least one patch (2) for radiating and/or receiving a circular polarised electromagnetic wave, a network of feeding lines (3), each feeding line (3) being coupled to and extending longitudinally or vertically to one of the patches (2) for transferring signal energy to and/or from the patch (2), whereby each group of feeding lines (3) being coupled to a group (6) of patches is pointing into a direction different from the pointing direction of the other groups of feeding lines (3) in order to achieve a circular orientation of the network of feeding lines (3) and respectively two adjacent groups of feeding lines (3) include the same angle.

The invention further relates to a method for executing the steps on the array antenna.

Description

The invention relates to a circular polarised array antenna according to claim 1, to a method for an array antenna according to claim 8 and to an array antenna according to claim 9.
In the recent past, the requirements for an antenna have significantly increased. Modern antennas must be more sophisticated to amplify signals of interest while nullifying noise and signals from other areas. Additionally, it is advantageous to send signals to points of interest without wasting power by radiating the signals towards regions where there are no points of interest.
CA 2 063 914 discloses a multibeam antenna and a beam forming network comprising a multiple beam or phased array antenna, antenna feeds and electronically beam steering networks. Horn antennas together with multiple dielectric resonators are added to form a radiator. The disadvantage of this antenna is its complexity as it requires two feeding lines for each radiator. Further, it does not provide manufacturing easiness for its horn installation.
The document "Aperture Coupled Microstrip Antenna With Quasi-Planner Surface Mounted Horn" by Abdel-Rahman et al, European Microwave Conference 2003, discloses a combination of aperture coupled microstrip antenna and a quasi-planner surface mounted short horn to increase the gain of a patch antenna. The disadvantage is that it does not work for circular polarisation as it can only be used for linear polarisation. It only provides medium gain and its side-lobe suppression is rather low.
It is therefore an object of the present invention to provide an array antenna for circular polarisation being easy to manufacture and having a high gain and a superior performance for circular polarisation.
It is a further object of the present invention to change the beaming direction of the array antenna without having high losses or noise.
This object is achieved by means of the feature of the independent claims.
According to the present invention, a circular polarised array antenna is proposed comprising groups of at least one patch for radiating and/or receiving a circular polarised electromagnetic wave, a network of feeding lines, each feeding line being coupled to and extending longitudinally or vertically to one of the patches for transferring signal energy to and/or from the patch, whereby each group of feeding lines being coupled to a group of patches is pointing into a direction different from the pointing direction of the other groups of feedings lines in order to achieve a circular orientation of the network of feeding lines and respectively to adjacent groups of feeding lines include the same angle.
Further, according to the present invention, a method for an array antenna is proposed, comprising the steps of radiating and/or receiving a circular polarised electromagnetic wave by groups of at least one patch, providing a network of feeding lines, each feeding line being coupled to and extending longitudinally or vertically to one of the patches for transferring signal energy to and/or from the patch, arranging each group of feeding lines being coupled to a group of patches in a way that each group of feeding lines has a pointing direction different from the pointing direction of the other groups of feeding lines in order to achieve a circular orientation of the network of feeding lines and arranging respectively to adjacent groups of feeding lines in a way that they include the same angle.
Further, according to another aspect of the present invention, an array antenna is proposed comprising patches for radiating and/or receiving a circular polarised electromagnetic wave and horn antennas, each horn antenna added to one of the patches in order to keep the same circular polarisation and increase gain, whereby the horn antennas are arranged in groups of at least one horn antenna and each group of horn antennas has a beaming direction different from the beaming direction of the other groups of horn antennas.
By providing patches for radiating and/or receiving a circular polarised electromagnetic wave in combination with a circular oriented feeding network a high performance of circular polarisation can be achieved including high gain and low noise.
Further, by providing horns having different beaming directions, a wide area of the hemisphere can be covered without sacrificing the radiation characteristics of the signal.
Advantageously, the angle between the pointing directions of two adjacent groups of feeding lines is equal to 360 degrees divided by the number of groups of feeding lines.
Further, advantageously, the phase between two adjacent groups of feeding lines is equal to 360 degrees divided by the number of groups of feeding lines.
In a preferred embodiment the array antenna consists of at least four patches (2) arranged in an quadratic 2x2 array.
Further, in the preferred embodiment the angle between the pointing directions of two adjacent feeding lines is equal to 90 degrees for improving circular polarisation.
Further, advantageously, the phase between two adjacent feeding lines is equal to 90 degrees.
Preferably a horn antenna is added to each of the patches in order to improve gain.
Advantageously, slots are provided respectively between two horns for suppressing surface waves.
Further, preferably the axis of the central horns is vertical and the axis of the other horns is tilted, whereby the more the horns are offset from the central horns the more the axis of the respective horns is tilted.
Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:
Fig. 1 shows an array antenna according to the present invention,
Fig. 2 is a plan view of an array antenna showing the different pointing directions of the feeding lines,
Figs. 3a to 3d are block diagrams showing the different pointing directions of the groups of feeding lines associated to groups of patches,
Fig. 4 shows an array antenna having groups of horn antennas with different beaming directions,
Fig. 5 is a cross section of Fig. 4,
Fig. 6 is a first embodiment of a horn antenna, and
Fig. 7 is a second embodiment of a horn antenna.
Fig. 1 shows an array antenna comprising patches 2 for radiating and/or receiving a circular polarised electromagnetic wave, which can be right hand or left hand circular polarised depending on the configuration of the patch and the feeding line 3. Each patch 2 has an associated feeding line 3, which is extending longitudinally to the patch 2. The feeding line 3 is coupled to the patch 2 and is able to transfer signal energy to and/or from the patch 2. Feeding can be done not only by feeding lines which are extended longitudinally or vertically. Feeding can also be done e.g. via a hole in the middle of the patch which connects to a different layer in a multilayer substrate. The most important is, that the relative phase angels at the patches are created correctly.
As can be seen from Fig. 2 the pointing direction, that is the orientation, of each feeding line 3 is different from the pointing directions of the other feeding lines 3. Thereby, a circular orientated feeding network of feeding lines 3 is achieved, which provides additional advantages to the performance of circular polarisation. In addition, the polarisation direction can be amplified, e.g. a right hand circular polarisation patch together with circular oriented feeding network will result in a radiation more on right hand direction than on left hand. The main beam of undesired polarisation is therefore small, and far away from the desired one.
This assembly can be used on both single layer and multi-layer array antennas.
According to Fig. 1 and 2 a circular horn or waveguide antenna 4 can be added to each patch 2 in order to keep the circular polarisation performance and to also improve the gain of the whole antenna. Hereby, a horn antenna 4 having a cylindrical or conical shape is placed on every patch 2 of the array antenna. By integrating the proposed multi-horn antenna in one piece, a design cheap in cost is realised and the advantage of easy installation can be achieved.
In order to remove unwanted electromagnetic influence from one element to the other when combining the antenna, slots 5 are provided respectively between two horns 4 in order to avoid cross-coupling or surface-waves which would result in an impact on the antenna performance.
The array antenna according to Fig. 1 and 2 consists of four patches 2 with feeding lines 3, whereby the pointing directions of two adjacent feeding lines 3 include an angle of 90 degrees. Also the phase between two adjacent feeding lines 3, that means the phase between two signals fed by two adjacent feeding lines 3, include angle of 90 degrees. It is also possible to use a higher number of patches with respective feeding lines 3 having different pointing directions, whereby the angle between the pointing directions of two adjacent feeding 3 lines or the phase between two adjacent feeding lines 3 is equal to 360 degrees divided by the number of feeding lines 3. If e.g. eight patches 2 are provided, then the angle and the phase between two feeding lines 3 will be set to 45 degrees.
According to Figs. 3a to 3d it is also possible to use groups 6 of patches 2, whereby each group of feeding lines 3 being coupled to a group 6 of patches 2 is pointing into a direction different from the pointing direction of the other groups of feeding lines 3. E.g. in Fig. 3a each group 6 of patches consists of 4 patches 2, whereby the whole array antenna consists of four groups 6 of patches 2 having angles between the pointing directions of the groups of feeding lines 3 of 90 degrees.
It is further possible to arrange the patches 2 or the groups 6 of patches 2 in a way that the decoupling for two polarisation states, that is left hand and right hand, is best. This can be achieved by rotating the pointing directions of the groups of feeding liens 3 either clockwise as shown in Fig. 3a and 3c or counter-clockwise as shown in Fig. 3b and 3d.
It is to be noted that the present invention is not limited to patches arranged in a two-dimensional array but may also include a three-dimensional array of patches 2, where the pointing direction of feeding lines 3 put on top of each other are changed.
In general, every radiating/receiving element has a main beaming direction. In order to properly describe such direction, a sphere coordinate system is introduced. Hereby, the z-axis designates the direction vertically extending from the plane of the antenna. Further, the  and  angles denote the elevation and azimuth angle in the sphere coordinate system.
Standard multi-array antennas are designed to have their zero looking angle, that is their main beam direction into the direction of z-axis. In order to cover a wider area of the hemisphere the looking angle of the beam is changed to different  and  angles by use phase-shifting for changing the beam direction. This yields to the problem that the control of unwanted signals such as side-lobe suppressions becomes very difficult for all states of the beam steering.
In the present invention according to Fig. 4, horns having different beam directions are therefore integrated in the antenna array. Hereby, the central axis of the horn is tilt depending on the position of the horn 4. Fig. 5 shows a cross section along the line A to A' in Fig. 4. It can be seen that in the example as shown in Fig. 4 and 5 at a time two horns 4 have the same beam direction 7a, 7b or 7c. Hereby the two horns 4 in the middle have a vertical beam direction 7b along the z-axis of a sphere coordinate system. The more the horns 4 are away from the two horns 4 in the middle the more the beam direction is tilted, that is the angle between the axis 8 of the lateral horns 4 and the axis 8 of the middle horns 4 is increased. Depending on the desired beaming direction the signal energy transferred to and/or from the horns 4 is switched between the horns 4 having different beaming directions by a switch integrated in the control circuit of the array antenna. This way, a wide coverage of the hemisphere can be achieved without sacrificing the suppression of unwanted noise or side-lobe signals.
It is to be noted, that a group of horn antennas 4 having the same beaming direction may consist of one or more horn antennas 4 arranged either in row, rectangular, circular or otherwise, in a two- or three-dimensional array.
Figs. 6 and 7 show horns 4 having different shapes which can improve the electrical performance of the antenna. Principally a horn antenna 4 serves as a waveguide and is able to radiate and/or receive the signal energy transferred to/or from the waveguide at the open end of line. An open waveguide as shown in Figure 7 having a rectangular or circular cross-section can be used as a simple antenna. Further, it is possible to use a waveguide widened at one end in order to improve the radiation characteristics and to improve the side-lobe performance as shown in Fig. 6.
It is to be noted that the present invention is not limited to the shapes of horns shown in the figures but includes every waveguide having the horn functionality.
As the array antenna according to the present invention is of a simple construction and low height, it can be manufactured with low effort and costs and it can be implemented in consumer products of small and compact size, such as mobile devices or consumer products.

Claims

Circular polarised array antenna comprising
groups (6) of at least one patch (2) for radiating and/or receiving a circular polarised electromagnetic wave,
a network of feeding lines (3), each feeding line (3) being coupled to and extending longitudinally or vertically to one of the patches (2) for transferring signal energy to and/or from the patch (2),
whereby each group of feeding lines (3) being coupled to a group (6) of patches is pointing into a direction different from the pointing direction of the other groups of feeding lines (3) in order to achieve a circular orientation of the network of feeding lines (3) and
respectively two adjacent groups of feeding lines (3) include the same angle.
Array antenna according to claim 1,
characterised in that the angle between the pointing directions of two adjacent groups of feeding lines (3) is equal to 360 degrees divided by the number of groups of feeding lines (3).
Array antenna according to claim 1 or 2,
characterised in that the phase between two adjacent groups of feeding lines (3) is equal to 360 degrees divided by the number of groups of feeding lines (3).
Array antenna according to any of the claims 1 to 3,
characterised in that is consists of at least four patches (2) arranged in an quadratic 2x2 array.
Array antenna according to claim 4,
characterised in that the angle between the pointing directions of two adjacent feeding lines (3) is equal to 90 degrees.
Array antenna according to claim 4 or 5,
characterised in that the phase between two adjacent feeding lines (3) is equal to 90 degrees.
Array antenna according to any of the claims 1 to 6,
characterised in that a horn antenna (4) is added to each of the patches (2) in order to improve gain.
Array antenna according to claim 7,
characterised by
slots (5) provided respectively between two horns (4) for suppressing surface waves.
Mobile terminal comprising a circular polarised array antenna according to any of the preceding claims.
Method for an array antenna comprising the steps of
radiating and/or receiving a circular polarised electromagnetic wave by groups (6) of at least one patch (2),
providing a network of feeding lines (3), each feeding line (3) being coupled to and
extending longitudinally or vertically to one of the patches (2) for transferring signal energy to and/or from the patch (2),
arranging each group of feeding lines (3) being coupled to a group (6) of patches in a way, that each group of feeding lines (3) has a pointing direction different from the pointing direction of the other groups of feeding lines (3) in order to achieve a circular orientation of the network of feeding lines (3), and
arranging respectively two adjacent groups of feeding lines (3) in a way, that they include the same angle.
Array antenna comprising
patches (2) for radiating and/or receiving a circular polarised electromagnetic wave and
horn antennas (4), each horn antenna (4) added to one of the patches (2) in order to keep the same circular polarisation and increase gain,
whereby the horn antennas (4) are arranged in groups of at least one horn antenna (4) and each group of horn antennas (4) has a beaming direction different from the beaming direction of the other groups of horn antennas (4).
Array antenna according to claim 11,
characterised in that the axis (8) of the central horns (4) is vertical and the axis (8) of the other horns (4) is tilted, whereby the more the horns (4) are offset from the central horns (4) the more the axis (8) of the respective horns (4) is tilted.