EP2887457A1

EP2887457A1 - Feed network and method of providing a feed network

Info

Publication number: EP2887457A1
Application number: EP13199379.2A
Authority: EP
Inventors: Dominik Arne
Original assignee: Alcatel Lucent Shanghai Bell Co Ltd
Current assignee: Nokia Shanghai Bell Co Ltd
Priority date: 2013-12-23
Filing date: 2013-12-23
Publication date: 2015-06-24

Abstract

The invention relates to a feed network (100) for feeding antenna elements (210_1_1, ..., 210_6_1, ..., 210_6_6) of an array antenna, wherein said feed network (100) comprises a rectangular array of nx many feed terminals along a first dimension (x) and ny many feed terminals along a second dimension (y), wherein nx, ny are even numbers with nx > 5, ny > 5, and wherein at least one of nx, ny is no power of two.

Description

Field of the invention

The invention relates to a feed network for feeding antenna elements of an array antenna. The invention further relates to a method of providing a feed network.

Background

Array antennas consist of an array of radiating elements, which, when transmitting a radio frequency (RF) signal, radiate electromagnetic energy in a per se known manner. For this purpose, each radiating element has to be fed, i.e. supplied with, a corresponding signal or electromagnetic energy, respectively, by means of a "transmission path" which is also denoted as feed line. Said feed lines form part of a feed network which enables individual radiating antenna elements to be supplied with an RF signal to be transmitted. Also, in the receive case, the feed network enables to collect from each of the individual antenna elements a received RF signal and to guide such received RF signal to a receiving system.
Conventional feed networks are designed such that they comprise matrix form with a predetermined number of feed terminals (nodes where an individual antenna element is connected to its associated feed line) per row and column, wherein said predetermined number is a power of two. I.e., conventional feed networks comprise 2*2=4, 4*4=16, 8*8=64, ... (generally: 2^(2*n), wherein n is a natural number >= 1) feed terminals, which correspondingly restricts conventional array antennas using such feed networks to a squared array configuration with 4, 16, 64, 256, 1024, 4096, ... elements. Obviously, this rather large spacing between the possible number of array elements results in poor flexibility regarding design and choice of array antennas.

Summary

It is an object to provide an improved feed network and an improved method of providing a feed network which enables to avoid the above mentioned disadvantages of prior art.
According to the embodiments, regarding the feed network, this object is achieved by said feed network comprising a rectangular array of nx many feed terminals along a first dimension and ny many feed terminals along a second dimension, wherein nx, ny are even numbers with nx > 5, ny > 5, and wherein at least one of nx, ny is no power of two. Thus an increased flexibility for the feed network design and also the array antenna design is attained. Preferably, the first and second dimensions are orthogonal to each other, and the parameters nx, ny represent the number of columns and the number of rows of the rectangular array.
According to an embodiment, the distances between different neighboring feed terminals and/or respective antenna elements along the two dimensions are denoted as dx and dy.
According to an embodiment, the feed terminals are equally spaced individually in each of the two axes x and y. E.g., either dx and/or dy is constant, wherein dx may be different from dy. According to a preferred embodiment, dx = dy is selected, e.g. the feed terminals are spaced equally along both dimensions.
According to an embodiment, the parameter nx and/or ny comprises one of the following values: 6, 10, 12, 14, 18, 20, 22, 24, 26, 28, 30, 34, 36, 38, 40. I.e., a feed network according to an embodiment may e.g. comprise a dimension of 6*6, 6*8, 10*8, 10*10, feed terminals and the like.
A further solution to the object of the present invention is given by a feed network for feeding antenna elements of an array antenna, wherein said feed network comprises a rectangular array of mx many feed terminals along a first dimension and my many feed terminals along a second dimension wherein mx, my are odd numbers with mx > 1 and my > 1. Thus, feed network configurations of size 3*3, 3*5, 3*7, 5*5, ... are also possible.
According to a further embodiment, nx equals ny and/or mx equals my. I.e., squared array configurations are also possible for the feed network according to the embodiments (i.e., for both the variants with a) even numbers with nx > 5, ny > 5, and wherein at least one of nx, ny is no power of two and with b) mx, my being odd numbers with mx > 1 and my > 1).
Advantageously, according to the embodiments, a wide variety of feed network configurations may be obtained with an overall number of feed terminals lying in between the above mentioned values of 16, 64, 256, 1024, 4096, ... as defined by the conventional approach.
As an example, when following the conventional approach of squared array feed networks with row and column counts that are a power of two, a next array size following a 256 element array (16x16), defined according to the conventional design method, is 1024 (32x32). In contrast, the principle according to the embodiments, defines a total of seven additional square array sizes (324, 400, 484, 576, 676, 784, 900, resulting from feed terminal matrices of side "lengths" 18x18, 20x20, .., 28x28, 30x30) in between these two conventional sizes (256, 1024), adding significant design flexibility enabling to better match RPE (radiation pattern envelope) and customer requirements at optimized cost.
According to a further embodiment, said feed network comprises elements of stripline technology, particularly microstrip and/or suspended stripline and/or triplate and/or suspended substrate line and/or shielded or semi-shielded microstrip, and/or of waveguide technology, particularly rectangular waveguides and/or ridged waveguides.
According to a further embodiment, feed lines connecting a central terminal of the feed network with respective feed terminals are provided. These feed lines may e.g. be implemented by using one or more of the aforementioned technologies. According to further embodiments, one or more feed lines may also comprise at least one of: T junctions (splitters), chamfered bends, quarter-wavelength transformers (e.g., as matching elements) or small chamfered cut out sections at T junctions, and the like.
According to a further embodiment, each feed line from a central terminal to a feed terminal comprises the same electrical length, so that all radiating elements of an array antenna having a feed network according to this embodiment may be fed with signals of exactly the same phase ("equi-phase signal supply"). According to a further embodiment, it is also possible that different feed lines comprise different electrical lengths, whereby the radiation pattern or beam characteristic of the antenna array comprising such feed network may be influenced in a per se known manner. Such different electrical lengths may e.g. be attained by incorporation of delay line sections, phase shifters, and the like.
According to a further embodiment, all feed lines of said feed network are arranged in basically one single plane, for example on a same surface of a common substrate, which according to one embodiment may also comprise radiating elements of an array antenna. Thus, a particularly flat ("two-dimensional") configuration may be attained.
A further solution to the object of the present invention is given by an array antenna with a plurality of antenna elements and at least one feed network according to the embodiments.
According to an embodiment, all transmission lines of the feed network and all antenna elements are arranged in basically one single plane.
A further solution to the object of the present invention is given by a method of providing a feed network for feeding antenna elements of an array antenna. The method comprises the following steps: providing a rectangular array of nx many feed terminals along a first dimension and ny many feed terminals along a second dimension, wherein nx, ny are even numbers with nx > 5, ny > 5, and wherein at least one of nx, ny is no power of two.
According to one embodiment, said step of providing comprises the following steps:

providing a square array of kx many feed terminals along a first dimension and kx many feed terminals along a second dimension, wherein kx is a power of two, and wherein kx <= nx and kx <= ny (i.e., the square array is at least in one of said two dimensions smaller or equal than said rectangular (nx * ny) array, as far as the count of feed terminals along the respective dimension is concerned),
providing ex many columns of further feed terminals along the first dimension and/or ey many rows of further feed terminals along the second dimension to extend said square array to said rectangular array,
connecting the further feed terminals of said ex many columns and/or ey many rows to the feed terminals of the square array.

According to a further embodiment, said step of providing ex many columns of further feed terminals along the first dimension and/or ey many rows of further feed terminals along the second dimension comprises adding said further feed terminals in sub-groups, preferably in sub-groups of four or sixteen further feed terminals. Advantageously, said sub-groups may be pre-designed and as such, the existing pre-designed layout of these sub-groups may be copied to perform said step of adding.
According to a further embodiment, feed lines are provided which connect a central terminal with respective feed terminals, wherein preferably each feed line from said central terminal to a feed terminal comprises the same electrical length.
The principle according to the embodiments is particularly advantageous as it provides parallel feed networks (so called 'corporate feed networks') which comprise a bandwidth that is significantly larger than that of serial feed networks.

Brief description of the figures

Further features, aspects and advantages of the present invention are given in the following detailed description with reference to the drawings in which:

Figure 1a: schematically depicts a top view of an array antenna according to an embodiment,
Figure 1b: schematically depicts a top view of a feed network for the array antenna of figure 1a according to an embodiment with antenna elements symbolized by dashed squares,
Figure 1c: schematically depicts the feed network of figure 1b without antenna elements,
Figure 2a: schematically depicts a top view of a portion of a feed network according to an embodiment,
Figure 2b: schematically depicts a top view of a portion of a feed network according to an embodiment,
Figure 3a: schematically depicts a feed network for a 10x10 array antenna,
Figure 3b: schematically depicts a top view for a 10x10 array antenna according to a further embodiment,
Figure 4a: schematically depicts a cross-sectional side view of a radiating element according to an embodiment,
Figure 4b: schematically depicts a top view of the radiating element according to figure 4a,
Figure 5a: schematically depicts a cross-sectional side view of a radiating element according to a further embodiment,
Figure 5b: schematically depicts a top view of the radiating element of figure 5a,
Figure 6a: schematically depicts a cross-sectional side view of a radiating element according to a further embodiment,
Figure 6b: schematically depicts a top view of the radiating element of figure 6a,
Figure 7: schematically depicts a top view of a feed network comprising feed lines employing waveguide technology,
Figure 8: schematically depicts a top view of a feed network according to a further embodiment,
Figure 9: schematically depicts a simplified flow chart of a method according to an embodiment,
Figure 10a, 10b, 10c: schematically depict different states of a method of providing a feed network according to an embodiment, and
Figure 11: schematically depicts a top view of a 12x12 feed network according to an embodiment.

Description of the embodiments

Figure 1 schematically depicts a top view of an array antenna 200 which comprises a rectangular, presently square, array of individual radiating elements or antenna elements, respectively. For the sake of clarity, only the four antenna elements 210_1_1, 210_6_1, 210_1_6, 210_6_6, which represent the corners of the array antenna 200, are provided with reference signs.
The antenna elements 210_1_1, .., 210_6_6 may e.g. be provided in the form of a metalized surface portion of a common substrate 202 of the array antenna 200.
Figure 1b schematically depicts a top view of a feed network 100 according to an embodiment, which may be provided to supply the antenna elements of the array antenna 200 of figure 1a with RF signals in a per se known manner. Likewise, the feed network 100 may also be used to collect RF signals arriving at the antenna elements of the area antenna 200 and to guide said RF-signals to a central terminal 102.
According to the embodiments, generally, the feed network 100 comprises a rectangular array of nx many feed terminals along a first dimension x and ny many feed terminals along a second dimension y, wherein nx, ny are even numbers with nx>5, ny>5, and wherein at least one of nx, ny is no power of two (e.g., 2, 4, 8, 16, 32, 64, ...).
As can be seen from figure 1b, for the present embodiment, the parameters nx, ny are chosen to six, i.e. nx=6, ny=6.
Thus, the feed network 100 comprises a total of 36 feed terminals, which are not provided with individual reference signs in figure 1b for the sake of clarity. Rather, instead, dashed squares 210_1_1, 210_2_1, .., 210_6_6 are depicted by figure 1b, which symbolize the individual antenna elements of the array antenna 200. More specifically, each of said antenna elements may be contacted by the respective feed terminal of the feed network 100 in a per se known manner, for example to simultaneously provide an RF signal from a center terminal 102 to all antenna elements.
Figure 1c schematically depicts the feed network 100 without symbolized antenna elements. Rather, two different groups 110, 120 of components ("portions") of said feed network 100 are designated by dashed rounded rectangles. From figure 1c, it can be seen that the feed network portion 110 comprises four feed terminals, also cf. the detailed view of figure 2a. Moreover, it can be seen that the further portion 120 depicted by figure 1c comprises four subgroups 110 which again are arranged in a symmetric manner in order to ensure identical electrical lengths between each feed terminal and the central terminal 102, whereby it is possible to provide all individual antenna elements by means of said feed network 100 with an RF-signal of equal phase.
Figure 2a depicts a detailed top view of a subgroup 110 of the feed network 100. As can be seen from figure 2a, the subgroup 110 comprises a central node 112 and two transmission lines 116a, 116b extending therefrom. To provide the first feed terminal 114a of the subgroup 110 with an RF signal supplied to the central point 112, further transmission line portions 118a, 118b, 118c are depicted which electrically conductively connect the feed terminal 114a with a central point 112. The electrical contact from central point 112 to the further feed terminals 114b, 114c, 114d is established in the same way. Particularly, according to a preferred embodiment, the complete subgroup 110 comprises symmetrical transmission lines from the central point 112 to each feed terminal 114a, 114b, 114c, 114d, to provide proper equi-phase signal supply to the antenna elements.
Also, for illustration purpose, figure 2a depicts a symbolized antenna element 210_2_1, which is coupled to the feed terminal 114c. The coupling itself may be attained in a per se known manner, i.e. by direct feed or by capacitive coupling, or the like.
Figure 2b schematically depicts a top view of a further subgroup 120 of the feed network 100 according to the embodiments. As can be seen from figure 2b, advantageously, the subgroup 120 comprises four subgroups 110 as explained above with reference to Fig. 2a, the center points 112 of which are respectively connected to a center point 122 of the further subgroup 120, again to attain identical electrical lengths for the respective signal paths. This way, an RF signal coming from the supply line 130 may be provided under equi-phase conditions via the central node 122 to each of the in total 16 feed points of the subgroup 120 depicted by figure 2b. As can also be seen from Figure 2b, symmetric transmission lines 126, 124a, 124h, which according to the present example are arranged in a "H"-shaped configuration, are provided for signal distribution from the center point 122 to the four subgroups 110.
Figure 3a schematically depicts a top view of a feed network 100a according to a further embodiment. Presently, the feed network 100a comprises a square array of 10x10 feed terminals (114a, .., cf. figure 2a), so that a total of one hundred individual antenna elements 210_1_1, .., 210_10_11, .., 210_1_10, .., 210_10_10 (cf. the dashed squares) of an array antenna can be handled by the feed network 100a.
A central terminal 104 of the feed network 100a is also depicted. Moreover, further feed lines are provided to distribute an RF signal supplied to the signal terminal 104 to the individual feed terminals of the feed network 100a. As can be seen from figure 3a, some portions 142a, 142b of the feed network extend beyond the basically squared shape of the antenna element matrix which is indicated by the dashed squares in figure 3a. This is due to the desired principle of equi-phase signal supply according to the present embodiment.
Figure 3b depicts a further embodiment 100b of the feed network. The feed network 100b is also of the 10x10 type, i.e. similar to figure 3a. However, the portions 142a, 142b of the figure 3a embodiment have been modified to obtain the figure 3b embodiment 100b, cf. the feed line sections denoted with the dashed ellipses E1, E2, E3. Thereby, the overall dimensions of the feed network 100b can be reduced while preserving equi-phase signal supply conditions.
Figure 4a exemplarily depicts a cross-sectional side view of a so called electrodynamically coupled patch, wherein item 152 represents a portion of a feed line (e.g., a feed terminal) of the feed network according to the embodiments, layer 150 represents a substrate (also cf. item 202 of figure 1), and wherein a radiating antenna element is noted with reference sign 154.
Figure 4b depicts a top view of the configuration of figure 4a.
Figure 5a schematically depicts a cross-sectional side view of a slot coupled patch with two substrate layers 150a, 150b and a conductor layer containing the slots arranged therebetween.
Figure 5b schematically depicts a top view of the configuration of figure 5a.
Figure 6a schematically depicts a cross-sectional side view of a slot coupled stacked patch according to an embodiment. This configuration comprises substrate layers 150a, 150b, 150c as depicted by figure 6a, and between the various substrate layers, electrically conductive layers are embedded in a per se known manner. Figure 6b schematically depicts a corresponding top view of Fig. 6a.
Figure 7 schematically depicts a top view of a portion of 120a of a feed network according to a further embodiment. In contrast to the preceding embodiments, which may e.g. comprise feed lines using micro strip line technology, the configuration according to figure 7 is based on wave guide technology. I.e., the feed line segments of the portion 120a are implemented by using wave guides. A subgroup providing four feed terminals is designated by reference sign 110, and regarding the number and topology of feed terminals, the configuration 120a of Figure 7 corresponds to Fig. 2b.
Figure 8 schematically depicts a top view of a feed network 100c according to a further embodiment. This embodiment is based on another aspect of the present invention, according to which a feed network comprises a rectangular array of mx many feed terminals along a first dimension x (also cf. Fig. 1b) and my many feed terminals along a second dimension y, wherein mx, my are odd numbers with mx>1 and my>1. Presently, mx=my=3.
The feed network 100c depicted by figure 8 can be used to provide an array antenna with nine antenna elements 210_1_1, .., 210_3_3 with a respective RF signal. A central point 104 of the configuration 110 is also depicted in figure 8.
According to a further embodiment, a method of providing a feed network for feeding antenna elements of an array antenna is proposed, the method comprising the following steps: providing a rectangular array of nx many feed terminals 114a, 114b, 114c, .. along a first dimension x and ny many feed terminals 114a, 114b, 114c, .. along a second dimension y, wherein nx, ny are even numbers with nx > 5, ny > 5, and wherein at least one of nx, ny is no power of two. For example, the embodiments 100, 100a, 100b, 100c of the feed network explained above may be obtained by this method.
Figure 9 schematically depicts a simplified flow chart of a method according a further embodiment. In a first step 310, a square array of kx many feed terminals along a first dimension x (Fig. 1b) and kx many feed terminals along a second dimension y are provided, wherein kx is a power of two (i.e. 2, 4, 8, 16, 32, 64, ..), and wherein kx<nx and kx<ny. In other words, in step 310 a square array of feed terminals is provided such that a number of feed terminals in any dimension x, y is smaller than or equal to the desired number nx, ny of feed terminals of the feed network to be provided.
Subsequently, in step 320, ex many columns of further feed terminals along the first dimension x and/or ey many rows of further feed terminals along the second dimension y are provided to extend the squared array to the desired rectangular array.
Subsequently, in step 330, the further feed terminals of said ex many columns and/or ey many rows, which have been obtained by the preceding step 320, are connected to the feed terminals of the square array.
The aforementioned method steps 310, 320, 330, are further exemplified below with reference to figure 10a, 10b, 10c, which depict different states of providing a feed network 100 according to an embodiment.
For the present example it is assumed that a feed network 100 (Fig. 10c) shall be provided which comprises nx=6 feed terminals along the x dimension, and which comprises ny=6 feed terminals along the y dimension. Consequently, in step 310 of figure 9, a power of two is determined which is smaller than nx=6 and ny=6. Thus, the power of two is selected kx=4. Correspondingly, according to step 310, a square array 1200 (figure 10a) is provided which comprises kx=4 many feed terminals along the x dimension and which also provides kx=4 feed terminals along the y dimension.
Subsequently, according to step 320 of figure 9, ex many columns c5, c6 (cf. figure 10b) along the first dimension x and/or ey many rows r1, r2 of further feed terminals along the second dimension y are provided to extend the square array 1200 as obtained by step 310 to the desired rectangular array 1202 (which presently is also a square array, since nx=ny=6, wherein, however, the rectangular array 1202 according to other embodiments could also be a true rectangular array with nx being different from ny, while array 1200 of step 310 always is a kx by kx square array).
In the present example, ex=2, ey=2. Generally, ex=nx-kx, and ey=ny-kx.
After performing step 320 according to figure 9, hence, the rectangular array 1202 is obtained, which already comprises feed terminals in a 6x6 type configuration.
As can be seen from figure 10a, the square array 1200, which has been provided in step 310 according to figure 9, already comprises feed line paths connecting a central terminal 122 of the square array 1200 with the individual 2x2 sub-arrays 110 (cf. Fig. 2a).
However, after step 320, which is reflected by the configuration of figure 10b, the newly added feed terminals of the rows r1, r2, and of columns c5, c6 are not yet connected to the feed terminals of the square array 1200. Consequently, in step 330 according to figure 9 it is proposed to provide these connections.
According to a further embodiment, it is also possible to omit individual interconnections or feed terminals. I.e., at first, the square array 1200 of feed terminals may be provided, which may be extended by step 320, i.e. by addition of further rows and columns, comprising a respective number of feed terminals. After these steps, any feed terminal may be connected with the other feed terminals and the central terminal 102 of the feed network 100 in the desired topology, e.g. symmetrical for equi-phase RF signal supply.
However, for an efficient provisioning of a feed network, according to a further embodiment, it may be beneficial to provide a proto type of a feed network subgroup ("pre-designed subgroup") such as e.g. the 2x2 configuration depicted by figure 2a. By copying and/or mirroring said configuration 110 according to figure 2a, e.g. the square array 1200 according to figure 10a may easily be obtained. Also, the further step 320 according to figure 9 may make use of such preconfigured subgroups 110. In other words, e.g. if two columns, c5, c6 are to be added to the square array 1200 according to figure 10b, this may be attained by adding three 2x2 configurations, whereby the two columns c5, c6 are attained.
Figure 10c schematically depicts the so obtained feed network 100, where individual feed terminals 114a, 114b, .. (figure 2a) are connected with the central terminal 102 in the depicted manner. According to an advantageous embodiment, each feed line from a central terminal 102 to a feed terminal comprises the same electrical length which advantageously enables equi-phase RF-signal supply to all antenna elements associated with the feed network 100.
According to a further embodiment, it is beneficial if all feed lines of the feed network 100 are arranged in basically one single plane, i.e. on a common substrate 202 (Figure 1a).
According to a further advantageous embodiment, all the feed lines of the feed network 100 are arranged in the same plane as the radiating elements 210_1_1, .. of the array antenna 200 (Fig. 1a).
In analogy to the configuration according to figure 10a to figure 10c, the feed network 100a as depicted by figure 3a may be obtained by applying the method according to the embodiments. For this example, it is supposed that the desired feed network 100a as depicted by figure 3a should comprise 10 columns of feed terminals and ten rows, i.e. being capable to supply 100 antenna elements arranged in a square matrix.
Consequently, according to step 310 as explained above with reference to figure 9, a square array 140 is provided with presently kx=8. Subsequently, in step 320 according to figure 9, further feed terminals are added to the existing configuration 140. Presently, this can be achieved by adding two columns c9, c10, which may be achieved by adding five copies of the 2x2 structure as depicted by figure 2a to the configuration 140 of figure 3a. Still further, four more feed network subgroups 110 as depicted by figure 2a must be added in figure 3a on top of the group 140 to provide the full 10x10 configuration.
Moreover, the electrical connection of the various feed terminals of the so obtained feed terminal matrix may either be performed simultaneously to the provisioning of the various arrays of feed terminals. Otherwise, the electrical connections between the individual feed terminals may also be provided afterwards, i.e. after providing the feed terminals themselves. As can be seen from Fig. 3a, a center terminal 142 of the group 140 may be connected by said feed line portions 142a, 142b to the feed terminals of the newly added columns c9, c10 and the first two rows of the configuration 100a.
According to a further preferred embodiment, the complete feed network 100a is provided by using micro strip line technology. This advantageously enables to simultaneously provide the antenna elements of the array antenna 200 (figure 1a), the feed terminals, as well as the feed lines connecting the various feed terminals with the central terminal 104.
Generally, the inventive principle advantageously enables to provide wide varieties of different feed networks, either rectangular or squared, wherein especially the number of rows or columns may comprise a wide variety of different values, as opposed to conventional systems, which rely on squared configurations having either 2, 4, 8, 16, 32, 64, 128, .. elements per row and column or other corresponding powers of two.
In contrast to the conventional systems, which rely on squared arrays with a side length that is a power of two, the feed network according to the embodiments can advantageously comprise many different sizes represented by different numbers of rows and/or columns, which are particularly not limited to powers of two, but rather to all intermediate values enabled by the rules according to the embodiments. For example, the number of rows and/or columns according to a preferred embodiment may be one of the following values: 6, 10, 12, 14, 18, 20, 22, 24, 26, 28, 30, 34, 36, 38, 40.
According to some embodiments, values larger than 40 are also possible, but physical reality as network losses will possibly rarely result in selecting these values.
According to an embodiment, the distances between different neighboring feed terminals 114a, 114c; 114a, 114b (Fig. 2a) and/or respective antenna elements along the two dimensions x, y are denoted as dx and dy. According to an embodiment, the feed terminals are equally spaced individually in each of the two axes x and y. E.g., either dx and/or dy is constant, wherein dx may be different from dy. According to a preferred embodiment, dx = dy is selected, e.g. the feed terminals are spaced equally along both dimensions.
According to another aspect of the present invention, also other values are possible for the number of rows or columns. Combinations of both aforementioned aspects are also possible, i.e. feed networks with e.g. three rows and eighteen columns, and the like.
Figure 11 schematically depicts a top view of a 12x12 feed network 100d according to a further embodiment. As can be seen, the feed network 100d may also be obtained according to the method of the embodiments, as e.g. exemplified by Fig. 9, wherein first a 8x8 subgroup 140 is provided, which is then extended by adding five 4x4 subgroups 120, only one of which is denoted by the reference sign 120 for clarity.
Array antennas 200 (Fig. 1a) according to the embodiments may be beneficial in many target systems due to the following reasons: freedom of pattern shaping, need for adaptive patterns, beam scanning, digital beam forming, the requirement to come up with 'flat' (close to 2D) antenna structures in order to get low obtrusiveness to facilitate landlords acceptance of antenna installation in residual areas.
According to an embodiment, depending on a desired pattern (also: antenna characteristic) of the array antenna 200, which in a per se known manner results from a superposition of the radiation of all radiating elements of the array, the power (electromagnetic wave with an amplitude and a phase) from the antenna input 102 (Figure 1b) may be splitted and distributed in a defined way by means of the feed network according to the embodiments, to ensure each radiating element is fed with the correct amplitude and phase. By employing feed networks designed according to the embodiments, this complex object may efficiently and reliably be attained especially also for larger arrays with many radiating elements.
According to a further embodiment, a feed network or its array of feed terminals may be created by building up larger arrays from sub-arrays of 2x2 elements or 4x4 elements or the like. According to an embodiment, these sub-arrays are connected with feed lines to their central feed points or center points 112, 122.
According to a further embodiment, extending a base array of feed terminals such as the arrays 120 of Fig. 1b or 140 of Fig. 3a, even by single rows r1 or columns c9 is possible.
According to a further embodiment, e.g. microstrip-type feed lines or the like may be used. According to a further embodiment, such feed lines may also comprise details such as chamfered bends, quarter-wavelength transformers as matching elements or small chamfered cut out sections at the T junctions, which are not depicted in the embodiments explained above for simplicity, as they do not impact or change the concept according to the embodiments.
According to further embodiments, multilayer approaches such as electrodynamic coupled patches (Fig. 4a), slot coupled patches (Fig. 5a), slot coupled stacked patches (Fig. 6) may be employed to implement feed lines and/or antenna elements.
According to further embodiments, waveguide feed systems may also be used for implementing the feed lines. According to an embodiment, a transition area from a feed line (waveguide) to the radiating element (horn or slot), e.g. at the feed terminal 114a (Fig. 2a), may depend on the selected technology. If horn technology is selected according to an embodiment, extending from normal waveguide dimensions from the feed line section to the horn aperture may e.g. require a 90 degree bent and/or some extension of the configuration in a direction perpendicular to the plane of the array antenna 200. An example of a corresponding embodiment is shown in Fig. 7.
The principle according to the embodiments represents a highly flexible, broad concept to design array antennas 200 and their feed networks 100, 100a, 100b, 100c, 100d. The principle is agnostic to a variety of technologies (direct fed microstrip arrays, electrodynamic coupled microstrip arrays, slot coupled microstrip arrays, waveguide fed slot arrays, waveguide fed horn arrays, ..). Also, according to some embodiments, a same path length from an input/output terminal 102 (Fig. 1b) towards each radiating element (equi-phase condition) is ensured. Depending on a required antenna pattern, uniform as well as tapered amplitude distributions can be realized and are equally supported by the concept.
Theoretically, there is no limit to the concept and huge arrays could be built (physical reality as network losses limit the sizes that will be applicable depending on the selected feed line technology).
Applying the proposed design approach results in significantly more array variants for feed networks and array antennas comprising such feed networks, with finer steps in feed terminal counts or antenna element counts, which corresponds to an "aperture size" of the array antenna 200. This enables to meet configuration needs that would have been impossible to match with conventional concepts. For some frequency ranges, the proposed solution is a pre-requirement to find a physically possible design solution meeting the RPE requirements at all. The significantly larger number of variants for feed networks and array antennas according to the embodiments advantageously allows to propose design solutions very close to targeted aperture surface sizes therefore delivering required performance at lowest cost.
The principle according to the embodiments is particularly advantageous as it provides parallel feed networks (so called 'corporate feed networks') which comprise a bandwidth that is significantly larger than that of serial feed networks.
The description and drawings merely illustrate the principles of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass equivalents thereof.
It should be appreciated by those skilled in the art that any block diagrams herein represent conceptual views of illustrative circuitry embodying the principles of the invention. Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, pseudo code, and the like represent various processes which may be substantially represented in computer readable medium and so executed by a computer or processor, whether or not such computer or processor is explicitly shown.

Claims

Feed network (100; 100a; 100b) for feeding antenna elements (210_1_1, .., 210_6_1, .., 210_6_6) of an array antenna (200), wherein said feed network (100) comprises a rectangular array of nx many feed terminals (114a, 114b, 114c, ..) along a first dimension (x) and ny many feed terminals (114a, 114b, 114c, ..) along a second dimension (y), wherein nx, ny are even numbers with nx > 5, ny > 5, and wherein at least one of nx, ny is no power of two.
Feed network (100; 100a; 100b; 100c) according to claim 1, wherein nx and/or ny has one of the following values: 6, 10, 12, 14, 18, 20, 22, 24, 26, 28, 30, 34, 36, 38, 40.
Feed network (100c) for feeding antenna elements (210_1_1, .., 210_6_6) of an array antenna (200), wherein said feed network (100c) comprises a rectangular array of mx many feed terminals (114a, 114b, 114c, ..), along a first dimension (x) and my many feed terminals (114a, 114b, 114c, ..) along a second dimension (y) wherein mx, my are odd numbers with mx > 1 and my > 1.
Feed network (100; 100a; 100b; 100c) according to one of the preceding claims, wherein nx equals ny and/or wherein mx equals my.
Feed network (100; 100a; 100b; 100c) according to one of the preceding claims, wherein said feed network comprises elements of stripline technology, particularly microstrip and/or suspended stripline and/or triplate and/or suspended substrate line and/or shielded or semi-shielded microstrip, and/or of waveguide technology, particularly waveguides and/or ridged waveguides.
Feed network (100; 100a; 100b; 100c) according to one of the preceding claims, wherein feed lines connecting a central terminal (104) with respective feed terminals (114a, 114b, 114c, ..) are provided.
Feed network (100; 100a; 100b; 100c) according to one of the preceding claims, wherein each feed line from a central terminal (104) to a feed terminal (114a, 114b, 114c, ..) comprises the same electrical length.
Feed network (100; 100a; 100b; 100c) according to one of the preceding claims, wherein all feed lines (116a, 116b, 118a, 118b, 124a, 124b, 126, 130) of said feed network are arranged in basically one single plane.
Array antenna (200) with a plurality of antenna elements (210_1_1, .., 210_6_1, .., 210_6_6) and at least one feed network (100; 100a; 100b; 100c) according to one of the preceding claims.
Array antenna (200) according to claim 9, wherein all transmission lines (116a, 116b, 118a, 118b, 124a, 124b, 126, 130) of the feed network and all antenna elements (210_1_1, .., 210_6_1, .., 210_6_6) are arranged in basically one single plane.
Method of providing a feed network (100; 100a; 100b; 100c) for feeding antenna elements (210_1_1, .., 210_6_1, .., 210_6_6) of an array antenna (200), comprising the following steps: providing a rectangular array (1202) of nx many feed terminals (114a, 114b, 114c, ..) along a first dimension (x) and ny many feed terminals (114a, 114b, 114c, ..) along a second dimension (y), wherein nx, ny are even numbers with nx > 5, ny > 5, and wherein at least one of nx, ny is no power of two.
Method according to claim 11, wherein said step of providing (300) comprises the following steps:
- providing (310) a square array (1200) of kx many feed terminals along a first dimension (x) and kx many feed terminals along a second dimension (y), wherein kx is a power of two, and wherein kx <= nx and kx <= ny,

- providing (320) ex many columns (c5, c6) of further feed terminals along the first dimension (x) and/or ey many rows (r1, r2) of further feed terminals along the second dimension (y) to extend said square array (1200) to said rectangular array (1202),

- connecting (330) the further feed terminals of said ex many columns (c5, c6) and/or ey many rows (r1, r2) to the feed terminals of the square array (1200).
Method according to one of the claims 11 to 12, wherein said step of providing (320) ex many columns (c5, c6) of further feed terminals along the first dimension (x) and/or ey many rows (r1, r2) of further feed terminals along the second dimension (y) comprises adding said further feed terminals in sub-groups (120), preferably in sub-groups of four or sixteen further feed terminals.
Method according to one of the claims 11 to 13, wherein feed lines are provided which connect a central terminal (104) with respective feed terminals (114a, 114b, 114c, ..), wherein preferably each feed line from said central terminal (104) to a feed terminal (114a, 114b, 114c, ..) comprises the same electrical length.