Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
PLANAR ARRAY ANTENNA
Document Type and Number:
WIPO Patent Application WO/2018/095541
Kind Code:
A1
Abstract:
The invention relates to a planar and layered array antenna structure. The antenna structure comprises a first metal or metalized substrate extending in a first plane extending in the width direction and the length direction. The structure comprises a second metal or metalized substrate extending in a second plane coinciding with the first plane, the substrate being positioned in connection with the first substrate via a choke flange arrangement. The second substrate has at least double the number of waveguide slots compared to the first substrate and the first substrate has a corresponding number of choke arrangements as the number of waveguide slots in the second substrate. Should the first substrate be the first substrate in the arrangement and a feeding platform for the arrangement, then the arrangement comprises a feed horn arrangement in connection to the first or second substrate.

Inventors:
YANG JIAN (SE)
Application Number:
PCT/EP2016/078884
Publication Date:
May 31, 2018
Filing Date:
November 25, 2016
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
JIANYANG ANTENNA&MICROWAVES (SE)
International Classes:
H01P5/12; H01Q21/00; H01Q21/06; H01Q3/12; H01Q3/18; H01Q5/25; H01Q13/04; H01Q25/00; H01Q25/02
Domestic Patent References:
WO2014090290A12014-06-19
Foreign References:
US20020101386A12002-08-01
US20120092224A12012-04-19
US20160056541A12016-02-25
US20160028164A12016-01-28
Other References:
T. TOMURA: "A 45 linearly polarized hollow-waveguide corporate-feed slot array antenna in the 60-GHz band", IEEE TRANS. ON AP, vol. 60, no. 8, 2012, pages 3640 - 3646, XP011455296, DOI: doi:10.1109/TAP.2012.2201094
W. W. MILROY: "The continuous transverse stub (CTS) array: Basic theory, experiment and application", PROC. ANTENNA APPLICATIONS SYMP., 25 September 1991 (1991-09-25)
M. OHIRA: "60-GHz wideband substrate integrated-waveguide slot array using closely spaced elements for planar multisector antenna", IEEE TRANS. ON AP, vol. 58, no. 3, 2010, pages 993 - 998
M. BOZZI: "Review of substrate integrated waveguide circuits and antennas", IET MICROWAVES, ANTENNAS & PROPAGATION, vol. 5, no. 8, 2011, pages 909 - 920, XP006038772, DOI: doi:10.1049/IET-MAP:20100463
A. VOSOOGH: "Corporate-fed planar 60 GHz slot array made of three unconnected metal layers using AMC pin surface for the gap waveguide", IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, 2015, pages 1536 - 1225
Attorney, Agent or Firm:
ZACCO SWEDEN AB (SE)
Download PDF:
Claims:
CLAIMS

1. A planar and layered array antenna structure (100) extending, with reference to orthogonal coordinates, in a width direction (X), a length direction (Y) and a thickness direction (Z), the antenna structure (100) comprising a first metal or metalized substrate (1; 101) extending in a first plane extending in the width direction (X) and the length direction (Y), the structure comprising a second metal or metalized substrate (2; 102) extending in a second plane coinciding with the first plane, the second substrate (2; 102) being positioned in connection with the first substrate (1; 101) via a choke flange arrangement (21), characterized in that the second substrate (2; 102) has at least double the number of waveguide slots (24, 26) compared to the first substrate (1; 101) and that the first substrate (1; 101) has a corresponding number of choke arrangements (21; 108A) as the number of waveguide slots (34, 26) in the second substrate, and should the first substrate (1; 101) be a feeding platform for the arrangement, then the arrangement comprises a feed horn arrangement (102E; 110A) in connection to the first substrate (1; 101) and the second substrate (2; 102) comprises at least two waveguide slots (24, 26) and the first substrate (1; 101) has a corresponding number of choke arrangements (21; 108A) as the number of waveguide slots (24, 26) in the second substrate (2; 102).

2. A planar and layered array antenna structure (100) according to claim 1, , wherein the first substrate (1; 130) and second substrates (2; 132) are the first and second substrates in an antenna stack, wherein the substrates are halved along the width direction (X) compared to following substrates in the stack, wherein the second substrate (2; 132) has at least one waveguide slot (24) and the first substrate (1; 130) has a corresponding number of choke arrangements (21) as the number of wave guide slots (24) in the second substrate (2; 132).

3. The antenna structure (100) according to any one of claims 1 or 2, wherein the structure (100) comprises additional substrates (103; 104; 105; 106; 107; 108) wherein the following substrate in the structure has at least double the number of waveguide slots compared to the foregoing substrate and that the foregoing substrate has a corresponding number of choke arrangements (21; 108A) as the number of waveguide slots in the following substrate.

4. The antenna structure (100) according to claim 3, wherein each choke arrangement (21; 108A) comprises a ditch arrangement (21; 108A) in the metal or metalized substrate with a depth dependent on the operational frequency, wherein the ditch arrangement comprises a ditch portion arranged with relation to each waveguide slot.

5. The antenna structure (100) according to claim 4, wherein the depth is approximately one quarter of a wavelength of the operational frequency.

6. The antenna structure (100) according to any one of claims 4 or 5, wherein the ditch arrangement (21; 108A) comprises a continuous ditch portion around the metal or metalized substrate.

7. The antenna structure (100) according to any one of claims 4 or 5, wherein the ditch arrangement (21; 108A) comprises a number of ditch portions.

8. The antenna structure (100) according to any one of the preceding claims 4-7, wherein the flange surrounds the ditch arrangement and the waveguide slots.

9. The antenna structure (100) according to any one of claims 1-6, wherein the flange comprises a number of flange portions (21; 21B).

10. The antenna structure (100) according to any one of the preceding claims, wherein the choke arrangement (21; 108A) in the first substrate (1; 101) comprises a curved portion, and wherein the corresponding waveguide slots (24, 26) in the second substrate (2; 102) are curved in a similar manner.

11. The antenna structure (100) according to any one of the previous claims, wherein the feed horn arrangement (102E; 110A) is arranged symmetrically in relation to the waveguide slots in the second metal or metalized substrate.

12. The antenna structure (100) according to any one of the previous claims, wherein the feed horn arrangement (102E; 110A) comprises a number of feed horn portions in an array for controlling a beam radiated from the antenna structure.

13. The antenna structure (100) according to any one of the previous claims 1-11, wherein the feed horn arrangement (102E; 110A) is mounted on a movable and controllable unit for controlling a beam radiated from the antenna structure.

14. The antenna structure (100) according to any one of the previous claims 1-11, wherein all plates are dis-attached to each other and arranged to be controlled and moved with relation to each other, in the X-Y plane, via a mechanical arrangement for controlling a beam radiated from the antenna structure due to the inter-relative movement of the substrates.

Description:
PLANAR ARRAY ANTENNA TECHNICAL FIELD

The invention relates to a planar and layered array antenna structure extending, with reference to orthogonal coordinates, in a width direction X, a length direction Y and a thickness direction Z. The antenna structure comprises a first metal or metalized substrate (numbered from the bottom of the structure) extending in a first plane extending in the width direction X and the length direction Y. The structure comprises a second metal or metalized substrate extending in a second plane coinciding with the first plane, the second substrate being positioned in connection with the first substrate via a choke flange arrangement.

BACKGROUND ART

When a high-gain antenna is needed, a large aperture antenna (reflector, lens or array) must be employed. However, thin planar array antennas are much preferred due to their aesthetics, light weight, easy installation, integrability, beam forming and steerability, and low fabrication cost. Therefore, planar array antennas have a lot of applications in wireless communication systems, radars and sensors, satellite antennas and radio telescopes.

Microstrip patch array with microstrip line feeding network can provide an array antenna with a low fabrication cost. However, the high transmission losses due to finite conductivity and radiation leakage of strip lines prevent its use in large arrays above 60 GHz, though new substrates, such as Liquid Crystal Polymer (LCP) and Low Temperature Co-fired Ceramic (LTCC), can have a low dielectric loss up to 110 GHz but it is the conductive loss and leakage loss that are the main factors for high loss at high frequencies. The transmission-line loss will eventually eat up the antenna gain increase by increasing the aperture size, which poses a gain limitation on this type of antennas at millimetre waves (mmW). Waveguide array architecture use conventional hollow waveguide to make slot or horn array antennas. Linearly polarized hollow waveguide corporate-feed slot antennas at 60 GHz (see for example "A 45 linearly polarized hollow-waveguide corporate-feed slot array antenna in the 60-GHz band," by T. Tomura, et.al, IEEE Trans, on AP, vol. 60, no. 8, pp. 3640-3646, 2012.), and linearly polarized CTS (Continuous Transverse Stub) antennas (see an example of "The continuous transverse stub (CTS) array: Basic theory, experiment and application" by W. W. Milroy in Proc. Antenna Applications Symp., Allerton Park, ILy, Sept. 25-27, 1991.) at 30 GHz are the typical examples. These types of antennas are very complicated and expensive to fabricate by the existing manufacture methods, such as soldering, wielding or diffusion bonding.

SIW (Substrate Integrated Waveguide) array architecture (See "60-GHz wideband substrate integrated-waveguide slot array using closely spaced elements for planar multisector antenna" by M. Ohira, et.al, IEEE Trans, on AP, vol. 58, no. 3, pp. 993-998, 2010) makes use of metal vias in a dielectric substrate, electrically connecting two parallel metal plates, to make a waveguide. The major advantages of SIW type are integrability and low cost. However, it has quite large ohmic loss even though it is smaller than the microstrip type, and the issue of large transmission loss due to radiation leakage arises above 100 GHz, since the spacing between metallized vias cannot be small enough for high frequency to avoid radiation leakage due to fabrication constraints (see "Review of substrate integrated waveguide circuits and antennas" by M. Bozzi et.al, IET Microwaves, Antennas & Propagation, vol. 5, no. 8, pp. 909-920, 2011). This limits the applications of SIW array architecture above 100 GHz. Another constrain for SIW antennas is that they are not suitable for large planar array with wideband performance due to its geometry nature.

Ridge Gap waveguide slot array has achieved a 25 dBi gain with a 14% relative bandwidth (see "Corporate-fed planar 60 GHz slot array made of three unconnected metal layers using AMC pin surface for the gap waveguide" by A. Vosoogh et.al, IEEE Antennas and Wireless Propagation Letters, pp.1536-1225, 2015). However, the manufacture cost of this type of antennas is high, due to the many detailed geometrical shapes for feeding network. The manufacture cost becomes significantly higher if a large aperture is required for high gain (>38 dBi).

There is thus a need for an improved high gain antenna. SUMMARY OF THE INVENTION

The object of the present invention is to provide an improved planar and layered array antenna structure removing at least part of the above mentioned problems. This object is achieved by the features of the characterizing portion of claim 1. Additional features of the invention are set out in the dependent claims.

The invention relates to a planar and layered array antenna structure comprising a long-slot choke-flange power divider. The structure extends, with reference to orthogonal coordinates, in a width direction X, a length direction Y and a thickness direction Z. The thickness direction is also the stacking direction of the structure. The antenna structure comprises a first metal or metalized substrate extending in a first plane extending in the width direction X and the length direction Y. The structure comprises a second metal or metalized substrate extending in a second plane coinciding with the first plane. The second substrate is positioned in connection with the first substrate via a choke flange arrangement. The second substrate is layered in the thickness direction Z onto the first substrate. The second substrate has at least double the number of waveguide slots, also called ports hereinafter, compared to the first substrate and the first substrate has a corresponding number of choke arrangements as the number of waveguide slots in the second substrate. In the description, the denotation first and second with relation to the substrates is only to more easily separate two platforms when describing the structure. The first and second substrate could be any two plates in an antenna structure having more than two substrates. The pair of two adjacent substrates forms the choke flange power divider. This means that from the bottom of the stack, i.e. from an antenna feeding unit, the signal is divided at least two fold with each choke flange power divider. According to one example the choke flange power divider can divide the signal into more than two signals by the second substrate having more than double the waveguide slots than the substrate before and the first substrate having a corresponding number of choke arrangements as waveguide slots in the second substrate.

Should the first substrate be a feeding platform for the arrangement, then, according to one example, the arrangement comprises a feed horn arrangement in connection to the first substrate and the second substrate comprises at least two waveguide slots and the first substrate has a corresponding number of choke arrangements as the number of waveguide slots in the second substrate. Waveguide slots will be described in various examples below and are also referred to as waveguide ports. According to another example, the feed horn arrangement is positioned in the second substrate and the following substrate has at least two waveguide slots. The feeding horn can be positioned in the front surface of the first plate or the rear surface of the second plate

According to one example, the first substrate and the second substrate form a feeding platform for the arrangement and are the first and second substrates in the antenna stack. According to the example, the first and second substrates are halved along the width direction X compared to the following substrates. One advantage of having a halve structure for the first two substrates is that the other half space can be used for complicated circuitry. Furthermore, the manufacturing cost and the weight will be a bit lower. The feeding horn can be positioned in the front surface of the first plate or the rear surface of the second plate. Hence according to the example, the second plate has at least one waveguide slot and the first plate has a corresponding number of ditch arrangements as the number of wave guide slots in the second plate.

As mentioned above, the antenna structure comprises more than two substrates wherein the following substrate in the structure has at least double the number of waveguide slots compared to the foregoing substrate and that the foregoing substrate has a corresponding number of choke arrangements as the number of waveguide slots in the following substrate.

It should be noted that the choke arrangement may be in the form of a unit that comprises choke portions that correspond to the waveguide slots. Hence, should the second substrate have a number of waveguide slots, then the first substrate comprise a matching choke arrangement that is either the same in number or comprises the same number of portions.

Each choke arrangement comprises a ditch arrangement in the substrate with a depth dependent on the operational frequency, wherein the ditch arrangement comprises a ditch portion arranged with relation to each waveguide slot.

The depth of the ditch is approximately one quarter of a wavelength of the operational frequency so the low impedance, ideally zero, at the bottom of the ditch is transferred to high impedance, ideally infinite, at the ditch port, and then transferred to low impedance, ideally zero, at the waveguide sidewall, which means that the two waveguides are electrically connected, with zero impedance between the two waveguides, even if there is a small gap in between. According to one example, the ditch arrangement comprises a continuous ditch portion around the substrate. Here, continuous ditch refers to that the ditch is a part of the substrate and that it encompasses an item/structure positioned on the substrate or being part of the substrate. The item/structure can be a waveguide slot, a number of waveguide slots or a feed horn arrangement.

As an alternative, the ditch arrangement comprises a number of ditch portions, i.e. a non- continuous ditch arrangement. The ditch portions are preferably arranged symmetrically about an item/structure positioned on the substrate or being part of the substrate but it can also be unsymmetrically arranged about the item/structure. According to one example, the ditch and/or the ditch portion(s) can be in the form of an indentation in the substrate. According to another example, the ditch and/or the ditch portion(s) are one or more passages between elevated parts being elongated elevations or elevated stubs. The elevated parts are elevated in the thickness direction and have an extension in the X- and Y-dimensions. The elevated parts are arranged to lie in contact with two adjacent substrates to form part of the choke arrangement. Hence the elevated parts may connect two adjacent substrates, but may also be attached to one or both of the substrates so that the substrates can move with relation to each other. The elevated parts may be part of any of or both substrates. In the latter example some elevations can be positioned on one substrate and some in substrate in the next coming layer. The elevated parts may form a seal in the X-and Y-direction but may also be open ended. The distance between the elevated portions is adapted to the wavelength to hinder electromagnetic leakage. According to one example, the ditch arrangement comprises both indentation(s) and elevated portion(s).

According to one example, the flange arrangement comprises a continuous ditch encompassing the item/structure positioned on the substrate or being part of the substrate and a number of ditch portions positioned outside the continuous ditch with reference to the item/structure or one or more continuous ditches positioned outside the continuous ditch with reference to the item/structure.

According to one example, the flange arrangement comprises a non-continuous ditch encompassing the item/structure positioned on the substrate or being part of the substrate and a number of ditch portions positioned outside the dis-continuous ditch with reference to the item/structure or one or more continuous ditches positioned outside the dis-continuous ditch with reference to the item/structure.

According to one example, the outer part of the flange surrounds the ditch arrangement and the waveguide slots. The outer part of the flange is arranged to form a seal between the substrates to eliminate leakage of the electromagnetic waves guided in the waveguide. The choke arrangements are arranged to add to the elimination of the leakage. The function of the choke arrangement with regard to elimination of leakage is known per se in the art.

The outer part of the flange and the ditch arrangement of one substrate forms together with the layered next substrate a waveguide space that is in electromagnetic fluid communication with the waveguide slots for allowing an electromagnetic wave to propagate from waveguide slot arrangement in one substrate to another waveguide slot arrangement in the next substrate.

According to one example, the flange comprises a number of flange portions. Hence, there may be an open corridor to the outside of the layered array antenna structure should the corridor have a dimension that together with the ditch arrangement hinders leakage of the electromagnetic energy.

According to one example, the choke arrangement in the first substrate comprises a curved portion, and the corresponding waveguide slots in the second substrate are curved in a similar manner. The curved geometry gives the benefit of a constant phase. According to one example, the following substrate comprises waveguide portions of different shape than curved, for example straight. This arrangement also gives the benefit of a constant phase.

According to one example, the feed horn arrangement is arranged symmetrically in relation to the waveguide slots in the second metal or metalized substrate. According to one example, the feed horn arrangement comprises a number of feed horn portions in an array for controlling a beam radiated from the antenna structure. Feed horns with different locations will create a main beam in different directions so multiple beams can be created by multiple feed horns. By controlling the exciting amplitude and phase of each feed horn, the beams for the feed horn array can be controlled and steered and therefore the beams of the whole planar array can be steered in the H-plane, i.e. the Y-Z plane.

The feed horn arrangement may be mounted on a movable and controllable unit for controlling a beam radiated from the antenna structure. According to one example, the plates are dis-attached to each other and arranged to be controlled and moved with relation to each other via, in the X-Y plane, a mechanical arrangement for controlling a beam radiated from the antenna structure due to the inter-relative movement of the substrates. This could be explained by offsetting a certain different length for each plate/substrate. In the end, the final radiating slots will have different phases which will make the main beam radiate in another direction in the E-plane, i.e. the X-Z plane, instead of in the normal direction to the aperture.

According to one example, the feed horn arrangement as such is mounted on a movable and controllable unit for controlling the direction of a beam radiated from the antenna structure. This would also change the beam after having passed the slots.

The antenna structure according to the invention offers an optimal solution to both the performance and cost. Several unique features are enabled by the antenna structure:

• Low cost - The antenna is constructed of several substrates/plates with only rectangular openings employed with the choke flange technology and therefore conductive contact between plates is not needed. This leads to a low-cost manufacture for mass production.

• High Gain Integrable with a thin profile - The antenna structure according to the invention offers a high gain integrable antenna with a low profile. The antenna according to the invention has more advantages over other types of antennas, especially when the demand for higher gain is required.

• Ultra-wideband with high performance - The antenna structure according to the invention provides high performance, high gain and low side lobes, with ultra- wideband due to its configuration nature. It can cover 3:1 multiple bandwidth, such as multiple frequency bands over 20 - 60 GHz. • Low ohmic loss - The antenna structure according to the invention has low ohmic loss due to the extreme wide plate waveguide, and therefore has a big advantage over other planar array architectures for high gain antennas.

• High power capacity - The antenna structure according to the invention has the extreme wide plate waveguide and therefore a high power capacity.

• Multiple steerable beams with a simple configuration - Due to its configuration nature, the antenna structure according to the invention offers electronically steerable multi- beams with a simple system. This function is very useful for car radars, radio telescopes and wireless communications.

• Tracking function with a simple geometry - The antenna structure according to the invention offers a unique simple geometry for beam tracking function.

• Since all plates in the arrangement need not be contacted with each other, the plates can move horizontally, i.e. in the X-Y plane, with relation to each other. According to one example the antenna arrangement comprises a mechanical mechanism arranged to control and move plates either individually or arranged to be connected to a guiding arrangement that connects the plates to each other. The guiding arrangement comprises connecting means connecting the plates. The connecting means is connected to the plates in a manner that allows for the plates to move with relation to each other. According to one example the connecting means comprises one rigid arm connected to all plates. The arm comprises attachment means for attaching the arm to each plate. By pushing the arm about one of the outermost attachments, i.e. the top plate or bottom plate, then the rest of the plates will move with relation to each other. For example, starting with a cuboid box shape and engaging the guiding arrangement will move the plates individually such that the shape of the structure will be altered into a parallelepiped/rhomboid. This alteration of the shape will make the beam generated from the antenna structure to change direction with relation to a different shape of the antenna structure. Hence, the mechanical mechanism, either directly or indirectly, controls or steers the beam in the E-plane. Therefore, the planar antenna can offer a 3D multi-beam scanning without steering the entire antenna as one unit mechanically. It should be noted that the connecting means could comprise a number of arms or similar devices that connects the plates to each other.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a view of a standard choke flange with the upper plate opened, according to prior art.

Figure 1A is a cross section view of a standard choke flange for the rectangular waveguide in figure 1.

Figure 2 is a view of a choke-flange power divider.

Figure 2A is a cross section view of the choke-flange power divider of figure 2. Figure 2B is a view of the choke-flange power divider of figure 2 with the upper flange opened.

Figure 3 is a view of l-to-4 choke-flange power divider with the upper flange opened.

Figure 3A is a cross section view of l-to-4 choke-flange power divider with the upper flange mounted on the lower flange.

Figure 4 is a view of a choke-flange power divider of long slots with the upper plate opened. Figure 4A is a first cross section view in an X-Z plane of a long-slot choke-flange power divider with the upper plate (flange) mounted on the lower plate (flange).

Figure 4B is a second cross section view in a Y-Z plane of a long-slot choke-flange power divider with the upper plate (flange) mounted on the lower plate (flange).

Figure 5 is a view of a first example embodiment of a long-slot choke-flange power divider with the upper plate opened.

Figure 6 is a view of a second example embodiment of a long-slot choke-flange power divider with posts/stubs.

Figure 6B is a view of a curved long-slot choke-flange power divider with the upper plate opened. Figure 7 is a view of the planar array antenna structure according to the invention with eight plates.

Figure 7A is a cross section view (Y-Z plane) of the planar array antenna structure of figure 7.

Figure 7B is a cross section zoom view of the cross section view of the planar array antenna structure in figure 7A.

Figure 7C is an exploded view of the planar array antenna structure of figure 7.

Figure 8 is a view of the front surface of the eighth plate of the planar array antenna structure in figure 7.

Figure 8A is a zoom view of the front surface of the eighth plate in figure 8. Figure 9 is a view of the rear surface of the eighth plate of the planar array antenna structure in figure 7.

Figure 9A is a zoom view of the rear surface of the eighth plate in figure 9.

Figure 10 is a view of the front surface of the seventh plate of the planar array antenna structure in figure 7. Figure 10A is a zoom view of the front surface of the seventh plate in figure 10.

Figure 11 is a view of the rear surface of the seventh plate of the planar array antenna structure in figure 7.

Figure 11A is a zoom view of the rear surface of the seventh plate in figure 11.

Figure 12 is a view of the front surface of the sixth plate of the planar array antenna structure in figure 7.

Figure 12A is a zoom view of the front surface of the sixth plate in figure 12.

Figure 13 is a view of the rear surface of the sixth plate of the planar array antenna structure in figure 7.

Figure 13A is a zoom view of the rear surface of the sixth plate in figure 13. Figure 14 is a view of the front surface of the fifth plate of the planar array antenna structure in figure 7.

Figure 14A is a zoom view of the front surface of the fifth plate in figure 14.

Figure 15 is a view of the rear surface of the fifth plate of the planar array antenna structure in figure 7.

Figure 15A is a zoom view of the rear surface of the fifth plate in figure 15.

Figure 16 is a view of the front surface of the fourth plate of the planar array antenna structure in figure 7.

Figure 16A is a zoom view of the front surface of the fourth plate in figure 16. Figure 17 is a view of the rear surface of the fourth plate of the planar array antenna structure in figure 7.

Figure 17A is a zoom view of the rear surface of the fourth plate in figure 17.

Figure 18 is a view of the front surface of the third plate of the planar array antenna structure in figure 7. Figure 18A is a zoom view of the front surface of the third plate in figure 18.

Figure 19 is a view of the rear surface of the third plate of the planar array antenna structure in figure 7.

Figure 20 is a view of the front surface of the second plate of the planar array antenna structure in figure 7. Figure 20A is a part zoom view of the front surface of the second plate in figure 20.

Figure 20B is a part zoom view of the front surface of the second plate in figure 20.

Figure 21 is a view of the rear surface the second plate of the planar array antenna structure in figure 7.

Figure 21A is a zoom view of the rear surface of the second plate in figure 21. Figure 21B is a part zoom view of the rear surface of the second plate in figure 21.

Figure 22 is a view of the front surface of the first plate of the planar array antenna structure in figure 7.

Figure 22A is a part zoom view of the front surface of the first plate in figure 22. Figure 23 is a view of the rear surface of the first plate of the planar array antenna structure in figure 7.

Figure 24 is a view of a simple difference patterns configuration for tracking.

Figure 24A is a detailed view of a simple difference patterns configuration for tracking.

Figure 25 is a view of an array feed for multiple beams and MIMO (multiple-input and multiple-output), and integration with MMIC (Monolithic Microwave Integrated Circuit).

Figure 25A is a zoom view of an array feed for multiple beams and MIMO, and integration with MMIC.

Figure 26 is a view of a planar array antenna structure with unsymmetrical (half) parabolic reflector. Figure 26A is a cross section view of a planar array antenna structure with unsymmetrical (half) parabolic reflector.

Figure 27 is a view of the planar array antenna structure with ultra-wideband (UWB) feed horn for UWB performance.

Figure 27A is a zoom view of the cross section of ultra-wideband (UWB) feed horn for UWB performance.

DETAILED DESCRIPTION

In the figures, like items are denoted with the same numbers. In the description plate and flange may be used to describe the same feature depending on the embodiment.

Figure 1 shows a prior art choke flange 1 for a rectangular waveguide. The choke flange 1 is mated with a cover flange 2 in order to form a choke connection. In figure 1 the choke connection is shown in exploded view. The choke flange 1 comprises a choke ditch 3 and a waveguide 4.

The working principle of the prior art choke flange can be described as follows: "At the operational frequency of the choke flange, the depth of the ditch is approximately one quarter of a wavelength. This is somewhat longer than a quarter of the free-space wavelength, since the electric field also varies in going around the ditch, having two changes of polarity, or one complete wave in the circumference. The ditch thus constitutes a quarter-wave resonant short-circuit stub, and has a high (ideally infinite) input impedance at its mouth. This high impedance is in series with the metal-to-metal connection between the flanges, and minimizes the current across it. The distance from the main waveguide through the gap to the ditch is likewise one quarter of a wavelength in the E-plane. The gap thus forms a quarter- wave transformer, transforming the high impedance at the top of the ditch to a low (ideally zero) impedance at the broad wall of the waveguide."

The cross section of a choke flange is shown in figure 1A. In figure 1A the choke flange 1 and the cover flange 2 are mated to form the choke connection. A waveguide gap 5 separates the choke flange 1 and the cover flange 2. The cross section view also shows the choke ditch 3, waveguide 4 and the mouth 6 of the choke ditch 3. A mechanical support 7 is present between the choke flange 1 and cover flange 2 at the outer part of the flange arrangement with reference to the ditch arrangement 3. The mechanical support 7 is for creating the waveguide gap 5, which is not required to have a good conductive contact between the two flanges. The choke is built up by ditches 3 and the gap 5 between two flanges 1, 2 to stop the wave leakage through a small gap when the two flanges are connected.

In practice, multiple ditches can be used for better stopping leakage of waves from the waveguide connection. In figures 2-27, the antenna structure 100 comprises at least one long-slot choke-flange power divider 10 comprising two substrates 1, 2, also called plates 1, 2 in the description. The antenna structure 100 extends with reference to orthogonal coordinates, in a width direction X, a length direction Y and a thickness direction Z. In the figures, the length direction Y is along the slots and the width X direction is orthogonal to the slot extension, and the thickness direction Z is the stacking direction of the plates/substrates. In the figures, the antenna structure 100 comprises a first metal or metalized substrate 1 extending in a first plane extending in the width direction X and the length direction Y. The structure comprises a second metal or metalized substrate 2 extending in a second plane coinciding with the first plane. The second substrate 2 is positioned in connection with the first substrate 1 via a choke flange arrangement 10. The second substrate 2 has at least double the number of waveguide slots 24, 26 compared to the first substrate 1 and the first substrate 1 has a corresponding number of choke arrangements 21 as the number of waveguide slots in the second substrate 2. Should the first substrate be the first substrate in the arrangement and a feeding platform for the arrangement, then the arrangement could comprise a feed horn arrangement 102E, see for example figure 21. Also here the second substrate comprises at least two waveguide slots and the first substrate has a corresponding number of choke arrangements as the number of waveguide slots in the second substrate.

It should be noted that the antenna structure can comprise more than two substrates and that each new substrate form a long-slot choke-flange power divider 10 arrangement with the substrate before and the substrate after. The choke-flange power divider 10 comprises elevated parts between the two substrates that creates a waveguide space 5 that is in electromagnetic fluid communication with the waveguide slots for allowing an electromagnetic wave to propagate from one waveguide slot arrangement in one substrate to another waveguide slot arrangement in the next substrate. The elevated portions can be positioned on either of the plates or both the plates. In the figures, the ditch arrangement 21 is positioned in the first substrate 1 and the waveguide slots 24, 26 are positioned in the second substrate 2. However, according to another example, parts of the ditch arrangement 21 could be positioned in the same substrate as the waveguide slots. These parts of the ditch arrangement 21 could be a ditch per se or be part of the elevations or be in the form of additional elevations or a combination thereof.

Figure 2 shows the principle for the planar array antenna structure according to one example of the invention comprising the choke-flange power divider 10. The choke-flange power divider 10 makes use of the working principle of the choke flange to have a power split from one port into two ports with chokes 21 around it. Therefore, no conductive contact is needed for the two larger flanges, and the leakage from large flange connection is stopped. In figure 2 the choke flange 1 and the cover flange 2 are shown to be mated to form a choke connection. The choke flange 1, i.e. the first substrate 1, comprises a first waveguide 4, while the cover flange 2, i.e. the second substrate 2, comprises a second waveguide 12 and a third waveguide 14. I n figure 2, the first waveguide 4 has a waveguide slot 44 in the first substrate 1, while the second substrate 2 comprises waveguide slots 24, 26 in connection to the second waveguide 12 and the third waveguide 14 respectively.

Figure 2A is a cross section view of the choke-flange power divider of figure 2. I n figure 2A, the choke principle is applied to the power divider. The choke flange 2 comprises a choke ditch 21 and a waveguide gap 5, i.e. the waveguide space 5, separates the choke flange 1 and the cover flange 2. The power divider 10 may have one ditch 21 or multiple ditches 21 around the board so no wave can leak through the gap 5 between the two flanges 1, 2 and the wave is divided into two waveguides 12 and 14.

Figure 2B shows the choke-flange power divider with the cover flange 2 opened.

Figure 3 shows a second example of the principle of the planar array antenna : a l-to-4 choke- flange power divider 10 with the cover flange 2, i.e. the second substrate 2, opened. It ca n be seen that the wave power is split from one port 4,or waveguide 4, into four ports 12, 14, 16, 18 or waveguides 12, 14, 16, 18 by using the choke principle. As in figure 2, the waveguide 4 in connection to the first substrate 1, has a corresponding waveguide slot 44 in the first substrate 2 and the waveguides 12, 14, 16, 18 connected to the second substrate 2 have corresponding waveguide slots 24, 26. As in figure 2, the choke flange 1, i.e. the first substrate 1, comprises a choke ditch 21. Figure 3A is a cross section view of l-to-4 choke-flange power divider 10 with the cover flange 2 mounted on the choke flange 1.

Figure 4 shows a third exam ple of the principle of the planar array antenna : a long-slot choke- flange power divider 10. The choke-flange power divider 10 comprises two substrates 1, 2 hereinafter called plates. I n figure 4 the first substrate is a choke plate 1 and the second substrate is a cover plate 2, and the cover plate 2 is stacked onto the choke plate 1. On the choke plate 1 a rectangular choke arrangement 21 in the form of choke ditches 21 are employed around the flange rim. The flange rim refers to the outer part of the flange that is arranged to form a seal between the substrates to eliminate leakage of the electromagnetic waves guided in the waveguide. A long-slot waveguide port 22 is at the choke plate 1. The cover/upper plate 2 is a flat plate with two long-slot waveguide ports 24 and 26. When the cover plate 2 is mounted on the choke plate 1, figure 4 shows a 3-dB power divider by the choke to stop leakage. The space between the two plates 1, 2 creates a waveguide. It should be noted that the choke arrangement could comprise elevated parts such that the ditch is created as a channel between the elevated parts. The elevated parts, i.e. the choke arrangement could be positioned on the cover plate 2 on that side of the cover plate 2 that faces the choke plate. As can be seen in the following figures, the form of the ports/slots 24, 26 can vary and the number of substrates in the antenna arrangement can vary.

In figures 4-27, the antenna structure 100 comprises at least one long-slot choke-flange power divider 10. The antenna structure 100 extends with reference to orthogonal coordinates, in a width direction X, a length direction Y and a thickness direction Z. In figure 4, the length direction Y is along the slots and the width X direction is orthogonal to the slot extension, and the thickness direction Z is the stacking direction of the plates/substrates.

In figure 4, the antenna structure 100 comprises a first metal or metalized substrate 1 extending in a first plane extending in the width direction X and the length direction Y. The structure comprises a second metal or metalized substrate 2 extending in a second plane coinciding with the first plane. The second substrate 2 is positioned in connection with the first substrate 1 via a choke flange arrangement 21. The second substrate 2 has at least double the number of waveguide slots 24, 26 compared to the first substrate 1 and the first substrate 1 has a corresponding number of choke arrangements 21 as the number of waveguide slots in the second substrate 2. In figure 4 the first substrate could be the first substrate in the antenna arrangement 100 and a feeding platform for the arrangement 100, then the arrangement could comprise a feed horn arrangement 102E. According to one example, the feed horn arrangement 102E is positioned in the first substrate. The second substrate then comprises at least two waveguide slots and the first substrate has a corresponding number of choke arrangements as the number of waveguide slots in the second substrate. According to the example shown in figure 21, the feeding horn is positioned in the second substrate 102. The next layer in the structure 100 would then have at least the double the waveguide slots as in the second substrate.

Figure 4A shows a cross section view (X-Z plane) of the long-slot choke-flange power divider of figure 4, where the flat steps 28 and 281 makes the power divide with good impedance matching for low reflection coefficient. Here two steps are used in both steps 28 and 281 for the impedance matching. More steps and even Miter bends can be used here for wider bandwidth but the manufacture cost will be higher. Figure 4B shows another cross section in the Y-Z plane of the choke-flange power divider 10 in figure 4, which shows that the waveguide has choke flanges at the both ends. The wave propagates in the X-direction so steps 28 and 281 in the X-direction are needed for impedance matching, while no waves propagate in Y direction so no steps in the Y-direction are needed.

Figure 5 shows a first alternative embodiment of the choke-flange power divider of figure 4: the choke ditches are straight separate ditches. The choke-flange power divider 10 comprises two plates: the choke plate 1, i.e. the first substrate, and the cover plate 2, i.e. the second substrate. On the choke plate 1 the straight separate ditches 21A are employed. With this ditch, easy manufacture with disc milling technology can be used to make the ditch, which is faster and more stable (therefore cheaper) than normal milling. Though the ditch is broken, due to that the width of the ditch is much smaller than half the wavelength, no wave can propagate out (no leakage). A long-slot waveguide port 22 is at the choke plate 1. The cover plate 2 is a flat plate with two long-slot waveguide ports 24 and 26. When the cover plate 2 is mounted on the choke plate 1, the figure shows a 3-dB power divider with the large choke flange. The 3-dB power divider means that the power is split evenly into the two output ports 24, 25. Figure 6 shows a second alternative embodiment of the choke-flange power divider of figure 4, or more accurately, a gap wave flange power divider. This gap wave flange power divider 30 comprises two plates: the choke plate 1, i.e. the first substrate 1, and the cover plate 2, i.e. the second substrate 2. On the choke plate pins/stubs 21B are employed to fully or partly create the ditch. Here, the space/channel created between the pins/stubs becomes the ditch or part of the ditch. A long-slot waveguide port 22 is at the choke plate. The cover plate 2 is a flat plate with two long-slot waveguide ports 24 and 26. When the cover plate 2 is mounted on the choke plate 1, figure 6 shows a 3-dB power divider by the gap wave flange. The ditch can even be broken into many pins 21B, as shown in Fig. 6, with the same principle that there is no leakage. The pins/stubs can have many different forms, for example a cross-section in the X-Y plane being circular, oval or polygonal. The cross-section may vary in width in the Z-direction. The pins/stubs may be different in shape between themselves or may be have the same shape.

Figure 6B is a view of a curved long-slot choke-flange power divider 10, with the upper plate 2 opened. It has the same ditch 21 build up as in figure 4, but with a different waveguide slot 24, 26 form. See also figure 7c for an antenna structure with curved slots. The input ports and output ports, i.e. the waveguides slots can be arbitrary in shape, such as square waveguide for dual-polarization, cross-slot waveguide for dual polarization, rectangular waveguide for linear polarization, circular waveguide for dual polarization, and curved waveguide slots.

Figure 7 shows an example of the planar array antenna structure 100, based on the choke- flange power divider described above. The antenna structure 100 comprises eight plates to have thirty-two (32) long slots for radiation: the first plate 101, the second plate 102, the third plate 103, the fourth plate 104, the fifth plate 105, the sixth plate 106, the seventh plate 107 and the eighth plate 108. The antenna structure 100 has two symmetric planes; the X-Z plane and Y-Z plane are the symmetry planes. An antenna with eight plates is normally for 37dBi gain with a square aperture. For a 43dBi gain with a square aperture, the antenna should have nine plates. Similarly, for a 31 dBi gain with square aperture, the antenna should have seven plates. With 6 dBi increase or decrease, in gain with square aperture, one plate needs to be added or correspondingly subtracted, to the antenna. In order to have other gain as desired, a rectangular aperture can be used. Thus, by using a choke-flange power divider according to the invention, we can build up a low profile l-to-2 N power divider as a feeding network for a planar array antenna, as shown in figure 7. A l-to-32 power divider is made of 6 plates from Plate 103 to Plate 108. This feeding network makes the E-plane, i.e. the X-Z plane, aperture distribution of the planar array antenna as a uniform distribution, which gives high gain and low side lobe levels, as shown below in figures 7A and 7C. The two bottom plates 101 and 102 are for having a tapped aperture distribution in H-plane, i.e. the Y-Z plane, as shown below in figures 7A, 20 and 21.

Figure 7A shows a cross section view in the X-Z plane of the antenna structure 100. Figure 7B shows a zoom view of the cross section in figure 7A to illustrate some of the details of the antenna structure 100. 108A is the ditch on the eighth plate 108, 108B is a long slot on the eighth plate 108, 108C is a step horn on the eighth plate 108, 107A is the ditch on the seventh plate 107, 107B is a long slot on the seventh plate 107, 106A is the ditch on the sixth plate 106, 106B is a long slot on the sixth plate 106. Figure 7C is an exploded view of figure 7 with the plates separated. In figures 7A-7C is shown that the first two substrates/plates 101, 102 have curved slots 24, 26 and ditches 21, but where the following substrates 103-108 have straight slots and ditches. The curved slots are suitable when used together with a parabolic reflector.

One advantage with the array antenna structure 100 is that the plates 101, 102, 103, 104, 105, 106, 107, 108 are stacked only by putting the plates topping one by one, without requiring soldering, wielding or bonding for good conductive contact, due to the application of the choke principle. Figure 8 is a view of the front surface 108F of the eighth plate 108 of the planar array antenna structure 100 in figure 7. Figure 8A shows a zoom part view of the front surface 108F of the eighth plate 108 in figure 7. 108A is the ditch on the eighth plate 108, 108B is a long slot on the eighth plate 108 and 108C is a step horn on the eighth plate 108.

Figure 9 is a view of the rear surface 108R of the eighth plate 108 of the planar array antenna structure 100 in figure 7. Figure 9A is a zoom part view of the rear surface of the eighth plate in figure 8, where 108D is the steps for impedance matching (low reflection coefficient). Also the choke 108A on and the long slot 108B on the eighth plate 108 are shown. Figure 9A shows that the ditch arrangement 108A comprises both elongated elevated portions and pins/stubs for creating the ditches. Figure 9A also shows that the ditches 108A are open, i.e. runs along the entire substrate with no ends. This makes the manufacturing of the choke plate and the choke arrangement 21 easier since a milling apparatus does not have to start and stop within the substrate.

Figure 10 shows a view of the front surface 107F of the seventh plate 107 of the planar array antenna structure 100 in figure 7. Figure 10A shows a zoom part view of the front surface 107F of the seventh plate in figure 10, where 107A is a ditch and 107B is a long slot.

Figure 11 shows a view of the rear surface 107R of the seventh plate of the planar array antenna structure 100 in figure 7. Figure 11A shows a zoom view of the rear surface 107R of the seventh plate 107 in figure 10, where 107A is the ditch, 107B is a long slot, and 107C are the steps for impedance matching. Figure 12 shows a view of the front surface 106F of the sixth plate 106 of the planar array antenna structure 100. Figure 12A shows a zoom part view of the front surface 106F of the sixth plate 106 in figure 12, where 106A is the ditches and 106B is a long slot.

Figure 13 shows a view of the rear surface 106R of the sixth plate of the planar array antenna structure 100 in figure 7. Figure 13A shows a zoom view of the rear surface 106R of the sixth plate 106 in figure 12, where 106A is the ditch, 106B is a long slot, and 106C is the steps for impedance matching.

Figure 14 shows a view of the front surface 105F of the fifth plate 105 of the planar array antenna structure 100 in figure 7. Figure 14A shows a zoom part view of the front surface 105F of the fifth plate in figure 14, where 105A is the ditches and 105B is a long slot.

Figure 15 shows a view of the rear surface 105R of the fifth plate 105 of the planar array antenna structure 100 in figure 5. Figure 15A shows a zoom view of the rear surface 105R of the fifth plate 105 in figure 14, where 105B is a long slot, and 105C is the steps for impedance matching. Figure 16 shows a view of the front surface 104F of the fourth plate of the planar array antenna structure 100 in figure 7. Figure 16A shows a zoom part view of the front surface 104F of the fourth plate 104 in figure 16, where 104A is the ditches and 104B is a long slot.

Figure 17 shows a view of the rear surface 104R of the fourth plate 104 of the planar array antenna structure 100 in figure 7. Figure 17A shows a zoom view of the rear surface 104R of the fourth plate 104 in figure 17, where 104B is a long slot, and 104C is the steps for impedance matching.

Figure 18 shows a view of the front surface 103F of the third plate 103 of the planar array antenna structure 100 in figure 7. Figure 18A shows a zoom part view of the front surface 103F of the third plate 103 in figure 18, where 103A is the ditches, 103B is a long slot and 103C is the steps for impedance matching.

Figure 19 shows a view of the rear surface 103R of the third plate 103 of the planar array antenna structure 100 in figure 7, one slot on a smooth surface. Figure 20 shows a view of the front surface 102F of the second plate 102 of the planar array antenna structure 100 in figure 7, which is a parabolic reflector with a reflector wall made by ditches 102A. Figure 20A shows a zoom part view of the front surface 102F of the second plate 102 in figure 20, where 102A is the ditches, and 102B and 102C are two long parabolic curved slots for coupling the waves from the lower parallel plate waveguide between the first and the second plates to the upper parallel plate waveguide between the second and the third plates. By using these two slots 102B, 102C, the input feed horn has no blockage to the reflector. Figure 20B is a part zoom view of the front surface 102F of the second plate 102 in figure 20, where 102D is the steps for impedance matching. By using the two long parabolic curved slots 102B and 102C, no wave will be reflected back to the input feed horn, which eliminates the blockage of the feed in the parallel waveguide parabolic reflector. Therefore, multiple feeds can be employed for multi-beam performance.

Figure 21 shows a view of the rear surface 102R of the second plate 102 of the planar array antenna structure 100 in figure 7, where 102E is a symmetrical feed horn to feed the two symmetrical parabolic reflectors. By using the symmetrical configuration, the beam of the antenna is guaranteed to be symmetrical and in the normal direction of the aperture. Figure 21A shows a zoom view of the rear surface 102R of the second plate 102 in figure 21, where 101G and 101H are connectors for mechanically stabilizing the long curved metal strip between the two slots which may be used or not used depending on the material used for the plate. Figure 21B shows a zoom view of the symmetrical feed horn 102E of the second plate 102 in figure 21, where 1021 is the steps for impedance matching. The purpose to have a symmetrical two-port horn is to guarantee a symmetric main beam and a main beam direction at the normal of the array aperture. In addition, this symmetry makes simulation of the antenna much easier, since a design model needs including only one fourth part of the antenna, which makes the simulation much faster.

A symmetrical two-port feed horn transmits the waves into two parabolic reflectors symmetrically with the axis in the parallel plate waveguide made by plates 101 and 102. Then the waves are reflected by the parabolic shape choke and coupled into upper layer between plates 102 and 103 by the two parabolic shaped slots 102B and 102C in figure 20. By this invented two-slot coupling to upper layer, we eliminate the blockage due to the feed horn. Therefore, we can use multiple horns for feeding the parabolic reflector to get multiple beams without any problem. With this parabolic reflector in the parallel waveguide, we achieve a tapped aperture distribution over the H-plane.

The two-slot coupling has very long curved slots. In order to have a stable mechanical solution and easy manufacture, the slots can be broken into a few shorter slots, as shown in Fig. 21A that slots have 102G and 102H to break the long slots into shorter slots, for instance two, three or more slots. Since the slots are very long, the effect of the small connection piece 102G and 102H on performance can be neglected.

Figure 22 shows a view of the front surface 101F of the first plate 101 of the planar array antenna structure 100 in figure 7, where 101A is the ditch to make a parabolic reflector wall and 101B is the input waveguide port. Figure 22A is a part zoom view of the front surface 101F of the first plate 101 in figure 22, showing the parabolic reflector wall by using ditches 101A.

It should be noted that the horn can be arranged in the first plate or the second plate, or be arranged separately from the plates for allowing free movement of the horn. One advantage of arranging the horn in the second plate is that screws can be used to fasten the second plate to the first plate.

Figure 23 is a view of the rear surface of the first plate of the planar array antenna structure 100 in figure 7 showing input waveguide port 101B.

Figure 24 shows a view of a simple symmetrical feed horn 110A with difference patterns function for tracking for the last plate 110. Many functions can be easily implemented in the feed horn in this invention. Figure 22A shows a detailed view of the simple symmetrical feed horn 110A with difference patterns function for tracking in figure 24, where HOB is the sum port, HOC and HOD are the ports for azimuth difference pattern, and HOE is the port for elevate difference pattern.

Tracking function is very important in many applications, such as in radars, wireless communication links, etc. This invention provides a very simple configuration for tracking function, as shown in Fig. 24 and Fig. 24A. Ports HOC and HOD are the port for difference pattern in H-plane and port HOE is the port for difference pattern in E-plane, and the isolation between the port of sum pattern and the ports of difference pattern is very high, more than 50 dB. After having the difference patterns, we have three methods to steer the main beam to the direction we need: 1) mechanically rotate the whole antenna; 2) mechanically rotate only the feed horn; 3) using multiple feed horns to steer the beams electrically.

With multiple horns as feed horns, we can get multiple beams in H-plane simultaneously, and therefore, we can steer the multiple beams electrically simultaneously in all desired directions in H-plane (X-Z plane).

Since all plates in the invention are not contacted with each other, the plates can move horizontally with a mechanical mechanism, such as rotating gearwheel, to make the beams steered in the E-plane. Therefore, the planar antenna can offer a 3D multi-bean scanning without steering the whole antenna mechanically. Figure 25 shows a view of an array feed 120 for multiple beams and MIMO, and integration with MMIC for the planar array antenna structure 100 of figure 7, where 120A is the ditches to make a parabolic reflector wall and 120B is MMIC Tx/Rx circuitry. Figure 25A is a zoom view of an array feed 120C for multiple beams and MIMO, and integration with MMIC in 120D.

A two-port feed horn can be either connected as shown in Fig. 21 or non-directly connected as shown in Fig. 25 where a Tx/Rx circuitry is connected to feeds and provides a possibility for multiple beams and MIMO functionality. Tx refers to transmission and Rx refers to a receiver circuitry.

Figure 26 is a view of a planar array antenna structure 100 with unsymmetrical (half) parabolic reflector 130. Plates 130 and 132 correspond to plates 101 and 102 respectively described above, with the difference that they are halved along the width direction X. Figure 26A is a cross section view of a planar array antenna structure with unsymmetrical (half) parabolic reflector. One advantage of having a halve structure for the first two plates is that the other half space can be used for complicated circuitry. Furthermore, the manufacture cost and the weight will be a bit lower. The feeding horn 102E can be positioned in the front surface of the first plate 130 or the rear surface of the second plate 132. Hence the second plate 132 has at least one waveguide slot 24 and the first plate 130 has a corresponding number of choke arrangements as the number of wave guide slots 21 in the second plate 132.

Figure 27 is a view of the planar array antenna structure with ultra-wideband (UWB) feed horn for UWB performance. The feed horn is a so-called double-ridged horn which makes the horn working over an ultra-wideband, such as 6:1 bandwidth. Together with the ultra-wideband long-slot power dividers (6:1 bandwidth) from plate 3 to plate 8, the whole planar antenna can have an ultra-wideband (6:1 bandwidth) performance. Figure 27A is a zoom view of the cross section of ultra-wideband (UWB) feed horn for UWB performance, where 271A and 271B are the upper and lower ridges to make the double ridged waveguide horn and 271 is the feeding mechanism which can be coax feeding or microstrip feeding.

Reference signs mentioned in the claims should not be seen as limiting the extent of the matter protected by the claims, and their sole function is to make claims easier to understand.

As will be realised, the invention is capable of modification in various obvious respects, all without departing from the scope of the appended claims. Accordingly, the drawings and the description thereto are to be regarded as illustrative in nature, and not restrictive.