Planar radiating structure for a multi-band antenna

Abstract

The present disclosure relates to a planar radiating structure (200, 300, 400, 500, 600) for a multi-band antenna (1000). The radiating structure (200, 300, 400, 500, 600) is configured to operate on a first frequency band. The radiating structure (200, 300, 400, 500, 600) comprises: a first dipole arm (212a, 312a, 412a, 512a, 612a) and a second dipole arm (212b, 312b, 412b, 512b, 612b) arranged to form a first dipole radiating element; wherein each dipole arm (212a, 312a, 412a, 512a, 612a, 212b, 312b, 412b, 512b, 612b) comprises a plurality of filtering unit cells (214, 314, 414, 514, 614) configured to serve as a band-pass filter for frequencies within a second frequency band, different from the first frequency band; wherein each filtering unit cell (214, 314, 414, 514, 614) comprises: two or more multi-stepped impedance resonating structures (216a, 216b, 316a, 316b, 416a, 416b, 516a, 516b, 516c, 616a, 616b, 616c), each formed by metal strips (218, 318, 418, 518, 618) having at least two sections of different impedances, and a connecting strip (220, 320, 420, 520, 620) connecting the two or more multi-stepped impedance resonating structures (216a, 216b, 316a, 316b, 416a, 416b, 516a, 516b, 516c, 616a, 616b, 616c). The present disclosure further related to a multi-band antenna (1000) comprising the planar radiating structure (200, 300, 400, 500, 600), and a network node (700) comprising the antenna (1000).

Description

[0001] PLANAR RADIATING STRUCTURE FOR A MULTI-BAND ANTENNA

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to the field of antenna technology, particularly to a planar radiating structure for a multi-band antenna, as well as an antenna and network node comprising said radiating structure.

[0004] BACKGROUND

[0005] Antennas with multi-band capabilities are today widely used in modern communication systems. These antennas enable simultaneous operation across multiple frequency bands, allowing for enhanced data throughput, efficient spectrum utilization, and support multiple network generations in one antenna. As an example, ultra-wideband antennas have been designed for cellular base stations. In such antennas, low band radiating structures are interspersed with high band radiating structures. However, the inherent proximity of the antenna's radiating structures in such configurations often results in crossband scattering, a phenomenon where signals in one frequency band interfere with signals in the other band. More specifically, the physically large low band element can behave as a strong scatterer in the high band due to high band currents being undesirably induced on it. These currents re-radiate and cause distortion of high band radiation patterns. The cross-band interference thus degrades the radiation performance and reduce the isolation between the different frequency bands.

[0006] Conventional methods for mitigating cross-band interference involve spatial separation, isolation structures, choking techniques, or stubs in the dipole arms. For instance, increased physical spacing between the radiating structures of the different frequency bands can reduce coupling, but this approach is impractical for compact designs where space constraints are present as it leads to a larger footprint of the antenna. Similarly, isolation structures such as electromagnetic shields can partially suppress interference but often introduce additional cost, complexity, and weight to the system. Choking techniques, while effective in attenuating unwanted signals, can limit the bandwidth and flexibility of the antenna. Stubs in dipole arms have been used to creating new current paths, thereby altering the resonance mode of the induced currents on the low band element. This solution is however also narrowband, and requires a more complex structure to change this. Other solutions based on using stubs are limited to PCB (printed circuit board) based applications, making them less flexible. It is therefore need for new and improved solutions for reducing cross-band interference in multi-band antennas.

[0007] P112264W001SUMMARY

[0008] The herein disclosed technology seeks to mitigate, alleviate, or eliminate one or more deficiencies and disadvantages in the prior art, singly or in any combination, to address various problems relating to crossband scattering in multi-band antennas.

[0009] The presently disclosed technology addresses these challenges by providing a planar radiating structure for a multi-band antenna, as well as a multi-band antenna and a network node comprising said planar radiating structure, as defined in the appended claims. The presently disclosed technology can provide for improved transmission performance by reduction of cross-band scattering over wide bandwidth. The disclosed technology is applicable to a wide range of wireless communication systems, including but not limited to, telecommunications, satellite communication, and any other wireless networking technology or multiband application where radiating structures of different frequency band are located in a vicinity of each other. The solution also can also fulfill other common requirements on an antenna, such as high isolation, stable radiation pattern, dual-polarization, array implementation, etc.

[0010] Various aspects and embodiments of the technology disclosed herein are defined below and in the accompanying independent and dependent claims.

[0011] According to a first aspect, there is provided planar radiating structure for a multi-band antenna, said radiating structure is configured to operate on a first frequency band. The radiating structure comprises a first dipole arm and a second dipole arm arranged to form a first dipole radiating element. Each dipole arm comprises a plurality of filtering unit cells configured to serve as a band-pass filter for frequencies within a second frequency band, different from the first frequency band. Each filtering unit cell comprises two or more multi-stepped impedance resonating structures, each formed by metal strips having at least two sections of different impedances. Each filtering unit cell further comprises a connecting strip connecting the two or more multi-stepped impedance resonating structures. With this aspect of the disclosed technology, similar advantages and preferred features are present as in the other aspects.

[0012] According to a second aspect, there is provided multi-band antenna. The multi-band antenna comprises a first radiating unit. The first radiating unit comprises a planar radiating structure according to any embodiments of the first aspect. The multi-band antenna further comprises a second radiating unit, configured to operate on the second frequency band. With this aspect of the disclosed technology, similar advantages and preferred features are present as in the other aspects.

[0013] P112264W001According to a third aspect, there is provided a network node. The network node comprising the multiband antenna according to any embodiments of the second aspect. With this aspect of the disclosed technology, similar advantages and preferred features are present as in the other aspects.

[0014] The disclosed aspects and example embodiments may be suitably combined with each other in any manner apparent to anyone of ordinary skill in the art, such that one or more features or embodiments disclosed in relation to one aspect may also be considered to be disclosed in relation to another aspect or embodiment of another aspect.

[0015] Further embodiments are defined in the dependent claims. It should be emphasized that the term "comprises / comprising" when used in this specification is taken to specify the presence of stated features, integers, steps, or components. It does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0016] A possible associated advantage of some embodiments is that it provides for reduced cross-scattering or undesired resonance in the cross band in multi-band antennas. This can be achieved through filtering characteristics which can reduce the impact between the radiating structures of the antenna.

[0017] A possible associated advantage of some embodiments is that it provides a planar radiating structure that can reduce undesired resonance effects from the interaction of cross-coupled dipole arms. Moreover, the radiation structure of the disclosed technology may enable wideband operation while also achieving band-pass filtering characteristics, without using an extra parasitic structure.

[0018] A possible associated advantage of some embodiments is that it provides a planar radiating structure which is resonance free in certain frequency bands, which provides smooth radiation performance over the whole operating frequency band.

[0019] A possible associated advantage of some embodiments is that it provides a solution which can have a broadband operating frequency range achieved with a compact design.

[0020] A possible associated advantage of some embodiments is that the disclosed technology provides a solution in which the design can be easily tuned to create multiple variants of the design with band stop filtering characteristics in different frequency ranges.

[0021] A possible associated advantage of some embodiments is that it provides a simplified structure which leads to lower cost design and also improves the stability and robustness of the design.

[0022] P112264W001A possible associated advantage of some embodiments is that the proposed radiating structure can be realized either on a single layer PCB or as a full metal design.

[0023] A possible associated advantage of some embodiments is that it provides a robust and simplified mechanical design.

[0024] A possible associated advantage of some embodiments is that the design can be fed in various ways such metal feed, PCB feed, side feed straight feed, single feed etc.

[0025] A possible associated advantage of some embodiments is that it can provide for a more environment friendly solution due to lower PCB material, which helps to reduce the carbon-dioxide footprint of the antenna on the environment.

[0026] These and other features and advantages of the present disclosure will in the following be further clarified with reference to the embodiments described hereinafter.

[0027] BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The foregoing will be apparent from the following more particular description of the example embodiments, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views, unless otherwise stated. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the example embodiments. In the drawings:

[0029] Figure 1A illustrates, by way of example, a multi-band antenna in a perspective view, in accordance with some embodiments.

[0030] Figure IB illustrates, by way of example, the multi-band antenna in a top-view, in accordance with some embodiments.

[0031] Figure 1C illustrates, by way of example, the multi-band antenna in a side-view, in accordance with some embodiments.

[0032] Figure ID illustrates, by way of example, an alternative representation of the multi-band antenna, in a top-view, in accordance with some embodiments.

[0033] Figure 2 illustrates, by way of a first example, a planar radiating structure in accordance with some embodiments.

[0034] Figure 3 illustrates, by way of a second example, the planar radiating structure in accordance with some embodiments.

[0035] Figure 4 illustrates, by way of a third example, the planar radiating structure in accordance with some embodiments.

[0036] P112264W001Figure 5 illustrates, by way of a fourth example, the planar radiating structure in accordance with some embodiments.

[0037] Figure 6 illustrates, by way of a fifth example, the planar radiating structure in accordance with some embodiments.

[0038] Figure 7 schematically illustrates a network node in accordance with some embodiments.

[0039] Figure 8A illustrates, by way of example, an equivalent circuit of a filtering unit cell, in accordance with some embodiments.

[0040] Figure 8B illustrates, by way of another example, an equivalent circuit of a filtering unit cell, in accordance with some embodiments.

[0041] DETAILED DESCRIPTION

[0042] The present technology is described below with reference to the accompanying drawings, in which certain aspects of the present technology are shown. The technology described herein may however, be embodied in many different forms and should not be construed as limited to the embodiments and aspects set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the present technology to those skilled in the art. Like numbers refer to like elements throughout the description, unless otherwise stated.

[0043] It is to be understood that the present disclosure is not limited to the embodiments described herein and illustrated in the drawings; rather, those skilled in the art will recognize that many changes and modifications may be made within the scope of the appended claims.

[0044] It is also to be understood that the terminology used herein is for purpose of describing particular embodiments only, and is not intended to be limiting. It should be noted that, as used in the specification and the appended claim, the articles "a", "an", "the", and "said" are intended to mean that there are one or more of the elements unless the context clearly dictates otherwise. Thus, for example, reference to "a unit" or "the unit" may refer to more than one unit in some contexts, and the like. Furthermore, the words "comprising", "including", "containing" do not exclude other elements or steps. It should be emphasized that the term "comprises / comprising" when used in this specification is taken to specify the presence of stated features, integers, steps, or components. It does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. The term "and / or" is to be interpreted as meaning "both" as well and each as an alternative.

[0045] More specifically, the wording "one or more" of a set of elements (as in "one or more of A, B and C" or "at least one of A, B and C") is to be interpreted as either a conjunctive or disjunctive logic. Put differently, it may refer either to all elements, one element or combination of two or more elements of P112264W001a set of elements. For example, the wording "one or more of A, B and C" may be interpreted as A or B or C, A and B and C, A and B, B and C, or A and C.

[0046] It will also be understood that, although the term first, second, etc. may be used herein to describe various elements or features, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first radiating unit could be termed a second radiating unit, and, similarly, a second radiating unit could be termed a first radiating unit, without departing from the scope of the embodiments. The first radiating unit and the second radiating unit are both radiating units, but they are not the same radiating unit, unless stated otherwise.

[0047] Even though in the following description, numerous specific details are set forth to provide a more thorough understanding of the described technology, it will be apparent to one skilled in the art that the planar radiating structure and the multi-band antenna and network node thereof, may be realized without some of these details. In other instances, well known constructions or functions are not described in detail, so as not to obscure the present disclosure.

[0048] Overview

[0049] The disclosed technology generally relates to a multi-band antenna, and more specifically to a radiating structure thereof. A multi-band antenna may in the present context be understood as an antenna comprising two or more radiating units, where each radiating unit is configured to operate on a certain frequency band. The radiating structure then refers to the component of a radiating unit which is the active part in emitting and receiving electromagnetic waves.

[0050] Typically, a multi-band antenna has a first radiating unit being configured to operate on a first frequency band, and a second radiating unit being configured to operate on a second frequency band. The frequency band herein refers to a frequency range across which an antenna or radiating unit can emit and receive electromagnetic waves. One of the first and second frequency band may be a low frequency band (or just "low band"), and the other a high frequency band (or just "high band"). The low frequency band is typically in the range of 0.6 GHz to 0.96 GHz, and the high frequency band in the range of 1.7 GHz to 2.7 GHz. It is however to be noted that the disclosed technology is not limited to a specific range of the first and second frequency bands, but can be applied to any multi-band antenna with two or more frequency bands. The terms "high-frequency" and "low-frequency" referred to throughout the text, unless otherwise defined, are simply used to describe a relatively high frequency and a relatively low frequency respectively, rather than limiting specific values of the frequencies. Similarly, the terms "high band" and "low band", unless otherwise defined, are also used to describe a higher frequency band and a lower frequency band.

[0051] P112264W001As explained in the foregoing, multi-band antennas can suffer from cross-band interference (or scattering), which refers to unwanted electromagnetic coupling or signal interference between the different frequency bands that the antenna is designed to operate on. This can be caused by the physical proximity of different radiating structures of the antenna. Put differently, signals in one band can interfere with or distort signals in another band, due to unwanted resonance in the radiating structures. A result being deterioration in the performance of the radiating structures. More specifically, the desired signal transmitted by one radiating structure may cause resonance in the other radiating structure, which in turn can cause the other radiating structure to emit an unwanted signal which interfere with the desired signal.

[0052] The disclosed technology is at least partly based on the realization that a specific multi-section stepped impedance filter (MSF) structure can be implemented in the planar radiating structure to mitigate such problems. More specifically, the MSF can achieve filtering effects in a radiating structure of one frequency band, for frequencies in another frequency band of the antenna. The MSF can be realized by two or more multi-section stepped impedance resonating structures (MSRs) arranged in a specific fashion, as will be further explained below.

[0053] An objective of the disclosed technology is thus to provide a first radiator on a first frequency band (referred to as the first radiating unit below) which is radiation free in a second frequency band on which a second radiator operates. This means that the radiation power of the first frequency band radiator is relatively low in the targeted second frequency band. Thus, making the first radiating structure transparent in the operating band of the second radiating structure.

[0054] Definitions

[0055] The disclosed technology relates to the field of antenna technology. More specifically, to a planar radiating structure for a multi-band antenna. Antennas are known in the art and used to convert radio frequency fields into alternating current or converting alternating current in to propagating waves at radio frequencies. The radio frequency wave (or electromagnetic wave of certain frequencies) has a polarization, which refers to the direction of the electric field of the signal. More specifically, the polarization can refer to an orientation of the plane of the electric field from a perspective of looking at it from the transmitter of the signal.

[0056] As known in the art, there are various kinds of antennas, for example, single-polarized antennas, dualpolarized antennas and etc. In order to facilitate the description, in the following, examples are taken where the antenna is of a dual-polarized type. However, it should be noted that the technical solutions of the disclosed technology also apply to other types of antennas, such as single-polarized antennas.

[0057] P112264W001Thus, in some embodiments of the disclosed technology, the planar radiating structure may be a so-called dual-polarized radiating structure. By a dual-polarized radiating structure (or antenna), it is meant a radiating structure (or antenna) that is capable of receiving and emitting electromagnetic waves with two distinct forms of polarization, typically horizontal and vertical polarization. These antennas have been developed to overcome some of the limitations of single-polarized antennas, which include limited ability to efficiently transmit and receive signals in diverse scenarios where signal orientations may vary. Moreover, dual-polarized antennas have gained popularity due to their ability to enhance communication reliability, mitigate signal interference, and support a broader range of applications, mainly due to enabling simultaneous transmission and reception of signals with different polarizations.

[0058] Embodiments

[0059] Figure 1A illustrates, by way of example, a multi-band antenna 1000 in accordance with some embodiments. The antenna 1000 may be part of a network node 700, as described below in connection with Fig. 7. The antenna 1000 is herein shown in a top perspective view. It is to be noted that the illustrations of the antenna 1000 (and any components thereof) provided herein is a simplified view of the antenna 1000. It is intended solely to depict the various components of the antenna and their relationships to one another for the purpose of understanding the disclosed technology. These illustrations should not be construed as limiting with regard to the size, shape, proportions, or precise arrangement of the components, which may vary depending on specific implementations or applications of the disclosed technology. Moreover, the antenna 1000 may, comprise additional components, such as additional structural, mechanical and / or electric parts. Together with some functional components for producing a driving signal to the antenna, such as a power supply, an antenna interface, processing circuitry etc., the antenna 1000 can form a network node, such as the network node 700 which will be further explained below in connection with Fig. 7.

[0060] The antenna 1000 may be seen as a device for transmitting and / or receiving signals in the form of electromagnetic waves. More specifically, the antenna 1000 may be configured to transmit and / or receive radio waves. Radio waves (also referred to as radio signal, or radio frequency (RF) signal) herein refers to electromagnetic waves in a certain frequency range (i.e. a radio frequency range).

[0061] In the broadest example embodiment, the antenna 1000 comprises a first radiating unit 102 and a second radiating unit 104. The first radiating unit 102 is configured to operate on a first frequency band. The second radiating unit 104 is configured to operate on a second frequency band.

[0062] The wording "radiating unit" (or just "radiator") may herein be construed as the necessary components responsible for converting electrical signals into electromagnetic waves (e.g. radio waves), or for receiving electromagnetic waves and converting them into electrical signals, as well as transmitting and P112264W001receiving said signals. Thus, it can be seen as the part of the antenna where the energy from a radio transceiver is transformed into the desired radiation pattern, or where the energy of a received radio wave is transformed into a useful signal by a radio receiver. In many antennas, the radiating unit typically comprise a conductive element / pattern (referred to below as "radiating structure") responsible for receiving and transmitting the electromagnetic waves / signals. The radiating structure can thus be seen as the active part in emitting or receiving the electromagnetic waves. The design of the radiating structure can depend e.g. on the type of antenna, its intended application, or its operating conditions. The radiating unit (i.e. the first and second radiating unit 102, 104 referred to below) may further comprise (in addition to the radiating structure) structural components, such as a substrate on (or within) which the radiating structure is arranged. The substrate can be a non-conductive or dielectric substrate on which electrically conductive patterns of the radiating structure, or electrically conductive tracks for feeding the radiating structure can be provided. The substrate may further comprise vias and pads, laminated on, under or between different layers of the substrate. The substrate may be a printed circuitry board (PCB). In the examples illustrated herein, the substrate has a rectangular or square shape. It is however to be appreciated that the substrate may have any arbitrary shape. In some embodiments, the radiating structure may be formed by a metal structure, requiring no substrate for support. In such case, the radiating unit may comprise structural parts for holding the radiating structure in place. The radiating unit may further comprise electrical components such as amplifiers, switches and DC circuitry, as well as a feeding network.

[0063] The first radiating unit 102 comprises a planar radiating structure. The planar radiating structure is not shown in detail in Fig. ID. The planar radiating structure may be provided on or within (or formed by) the planar structure shown herein. For details, reference is made to Fig., 2 to 6 below. The planar radiating structure may be a planar radiating structure such as any of the planar radiating structures 200, 300, 400, 500, 600, as further described below in connection with Fig. 2 to Fig. 6. The planar radiating structure being configured to operate on the first frequency band. In other words, the planar radiating structure can be designed to emit or receive electromagnetic waves across the first frequency band.

[0064] In the present context, the term "planar" can be understood as a structure that lies substantially within a two-dimensional plane. The planar radiating structure of the first radiating unit 102 can e.g. be realized as a flat or substantially flat structure. The planar radiating structure can be implemented using conductive materials on a dielectric substrate, such as microstrip on a printed circuit board (PCB), or from a sheet metal.

[0065] P112264W001The second radiating unit 104 may comprise one or more radiating sub-units 104a, 104b, 104c, 104d. More specifically, the second radiating unit 104 may comprise a plurality of radiating sub-units 104a, 104b, 104c, 104d. In the illustrated example, the second radiating unit 104 comprises four radiating sub-units. In some embodiments, the second radiating unit 104 comprises two radiating sub-units. It is however to be appreciated that any number of radiating sub-units may be applicable, depending on a specific need.

[0066] The plurality of radiating sub-units 104a-d can be seen as individual (or stand-alone) radiating units, but which can work together. The plurality of radiating sub-units 104a-d can thus be configured to work together as a single radiating unit (i.e. the second radiating unit 104). This way, signals of the plurality of radiating sub-units can be combined in order to achieve improved performance over that of a single radiating sub-unit. For instance, the plurality of radiating sub-units enables the second radiating unit 104 to match a radiation pattern to a desired coverage area, change radiation pattern, and adapt to changing signal conditions.

[0067] Each of the plurality of radiating sub-units 104a-d of the second radiating unit 104 comprises a respective radiating structure (not shown). The radiating structure of the plurality of radiating subunits 104a-d may have a different design than the planar radiating structure of the first radiating unit 102. This is at least partly by the fact that the plurality of radiating sub-units 104a-d of the second radiating unit 104 are configured to operate on the second frequency band, different from the first frequency band at which the planar radiating structure of the first radiating unit 102 is configured to operate. It is however to be appreciated that the plurality of radiating sub-units 104a-d of the second radiating unit 104 may be planar radiating structures as well (although of different designs). Moreover, the plurality of radiating sub-units 104a-d of the second radiating unit 104 may be of a same antenna type as the planar radiating structure of the first radiating unit 102, namely being formed by one or more dipole radiating elements, as will be further elaborated upon below.

[0068] Fig. IB illustrates the multi-band antenna 1000 in a top-view. As shown in Fig. IB (and even more clearly in Fig. 1C), the first radiating unit 102 is arranged above the second radiating unit 104. The first radiating unit 102 may thus at least partly physically cover the second radiating unit 104. Typically, the plurality of radiating sub-units 104a-d of the second radiating unit 104 are arranged in an equally spaced grid, depending on the frequencies of the second frequency band. The plurality of radiating sub-units 104a-d of the second radiating unit 104, may be distributed so as to form a common phase center of the second radiating unit 104. Moreover, they may be arranged such that the common phase center coincides with a phase center of the first radiating unit 102.

[0069] P112264W001In the illustrated example, the first radiating unit 102 is a low band radiating unit. In other words, the planar radiating structure of the first radiating unit 102 is configured to operate on low band frequencies. Hence, the first radiating unit 102 emits signals having longer wavelengths. For this reason, the first radiating unit 102 is physically larger than the radiating sub-units 104a-d of the second radiating unit 104, which is configured to operate on high band frequencies. As the radiating sub-units 104a-d of the second radiating unit 104 (or high band radiating unit) emit shorter wavelengths, they can be made smaller, allowing for multiple such structures to be incorporated in the antenna 1000 without conflicting with space constraints. Moreover, as shorter wavelengths have shorter range, and more affected by obstacles, it can be advantageous to incorporate more than one high-band radiating sub-unit 104a-d.

[0070] Fig. 1C shows the multi-band antenna 1000 in a side-view. The antenna 1000 may further comprise a base structure 106 (or just "base"). The base structure 106 may be understood as a foundational component or support framework onto which the first radiating unit 102 and the second radiating unit 104 are mounted. The base structure 106 may thus serve as structural support of the radiating units. The base structure 106 may further serve the purpose of providing electrical functionality, such as a ground plane for the antenna 1000. The base structure 106 may further comprise any necessary electrical lines of a feeding network of the antenna 1000. The base structure 106 can further serve as a reflector. This may be to enhance and control the radiation characteristics of the antenna 1000.

[0071] As further seen in Fig. 1C, the second radiating unit 104 may be arranged between the base structure 106 and the first radiating unit 102. More specifically, a plane of the radiating structure of the second radiating unit 104 may be arranged between the base structure 106 and the plane of the radiating structure of the first radiating unit 102. In other words, the first radiating unit 102 may be arranged above the second radiating unit 104, as seen along the direction D. The direction D being parallel, and pointing in the direction of, a normal vector N to the base structure 106.

[0072] Fig. ID illustrates an alternative representation of the multi-band antenna 1000. More specifically, Fig. ID shows the planar radiating structure of the first radiating unit 102 and the radiating structures of the plurality of radiating sub-units 104a-d of the second radiating unit 104 as equivalent dipole radiating elements. In the illustrated example, each radiating structure (i.e. of both the first radiating unit 102 and the second radiating unit 104) comprises a dual-polarized dipole radiating element. It is however to be appreciated that the disclosed technology is also applicable for single-polarized dipole radiating elements, as well as other types of antennas (i.e. other than dipole).

[0073] P112264W001A dipole antenna generally comprises two identical conductive elements, such as metal wires, rods, or strips, oriented in opposite directions. For transmission, the driving signal is applied, or for receiving, the output signal is taken, between the two elements. Looking e.g. at the first radiating unit 102, it comprises a first dipole radiating element (or dipole antenna), formed by a first dipole arm 112a and a second dipole arm 112b. Thus, a pair of dipole arms together form a dipole radiating element. The first dipole radiating element having a first polarization. In other words, the first dipole radiating element is configured to emit / receive electromagnetic waves with the first polarization.

[0074] The first radiating unit 102 further comprises a second dipole radiating element, formed by a third dipole arm 112c and a fourth dipole arm 112d. The second dipole radiating element having a second polarization. The second polarization may be orthogonal to the first polarization. Thereby, a dualpolarized planar radiating structure, which can both emit and receive signals in two orthogonal polarizations can be achieved. In some embodiments, the polarization refers to a linear polarization of the emitted / received waves. Thus, by the first and second polarization being orthogonal to each other, in reference to linear polarization, it is herein meant that an electric field vector of the first dipole radiating element oscillates in a plane perpendicular to a plane of oscillation of an electric field vector of the second dipole radiating element. In a typically arrangement, the first polarization may be a horizontal polarization, and the second polarization may be a vertical polarization, or vice versa. It is however to be appreciated that depending on the orientation of the antenna structure, the first and second polarization may be different from the horizontal and vertical direction (although still orthogonal to each other).

[0075] Similar to the first radiating unit 102, and as shown in Fig. ID, each of the radiating sub-units 104a-d of the second radiating unit 104 also comprises a pair of dipole radiating elements, which in turn is formed by two pairs of dipole arms. It is however to be appreciated that the plurality of radiating subunits 104a-d of the second radiating unit 104 may be formed by any other suitable antenna type as well. For the sake of brevity, the structure of second radiating unit 104 is not described in more detail.

[0076] The dipole arms of each dipole radiating element extends in opposite directions to each other.

[0077] Moreover, each dipole radiating element may be a quarter-wave dipole antenna. This means that a length of each dipole arms is about a quarter of the wavelength of the signals that the respective radiating unit 102, 104 is configured to transmit / receive. Or more specifically, a quarter of the wavelength of the center frequency of the frequency band that the respective radiating unit 102, 104 is configured to transmit / receive. In the present context, and as further described below, the dipole arms can be formed by a closed loop, or a "metal ring structure" as referred to below. In such case, a side

[0078] P112264W001length (e.g. the circumference in case of a circular ring structure) of the ring structure may be about a quarter of the wavelength to make it a quarter-wave dipole antenna.

[0079] The multi-band antenna 1000 may further comprise a feeding network. The feeding network comprises a plurality of feeding lines 108a, 108b, 108c, 108d, 108e. The feeding lines may be understood as a conductive pathway (and any other associated equipment) within the feeding network. The feeding lines are configured to deliver electromagnetic energy from a signal source (e.g. a radio transceiver) or transmission line (such as a coaxial cable, twin-lead, or ladder line) to the radiating structures of the multi-band antenna 1000. More specifically, the plurality of feeding lines 108a, 108b, 108c, 108d, 108e may be coupled to the first radiating unit 102 and the second radiating unit 104, and configured to feed the first radiating unit 102 and the second radiating unit 104 with a driving signal. The feeding network may comprise a sub-feeding network for each radiating structure of the first and second radiating unit. The sub-feeding networks may e.g. comprise a balun for feeding the respective radiating structures. The feeding network may deliver the driving signal to the respective radiating structure through a capacitive coupling. Alternatively, the radiating structure and a corresponding feeding line may be coupled through a via in a substrate on / in which the radiating structure is arranged.

[0080] A part of the feeding network for feeding the planar radiating structure 200 may be implemented as a center feed 234. The center feed 234 is herein represented by a solid black circle, for illustrative purposes only. The center feed may be a crossed center feed (or cross-coupled feed), comprising two interconnected crossed PCB boards. The PCB boards may further comprise a balun for each dipole arm, or for each dipole radiating element. The feed may however be of other types as well, with different configurations well known to those skilled in the art.

[0081] The driving signal may be an alternating current of radio frequency, generated by the radio transceiver. The driving signal may thus be fed through the feeding network to the radiating structures of the multiband antenna, which converts the alternating current of the driving signal to radio waves. In receiving mode, the incoming radio waves can excite alternating currents in the radiating structures, and the feeding network can deliver this current to the radio transceiver, which processes the signal. The feeding network can ensure proper distribution of the signals to achieve the desired radiation characteristics. The feeding network may be realized as a full metal feed, a PCB feed, or a hybrid feed. Moreover, the feeding network can be any one of a side feed, a slanted feed or a straight feed.

[0082] The specific design of the feeding network depends e.g. on the type of antenna (or radiating units), its intended application, the physical structural characteristics of the antenna, and the desired performance characteristics. For example, in addition to the above, the feeding network may comprise

[0083] P112264W001a slanted side feed, or any planar structure in a single layer on a substrate. The specific details of the feeding network are therefore left out of the present description. Moreover, only parts of the feeding network are shown in Fig. 1A and 1C, for illustrative purposes. The feeding network may comprise further feeding lines, and additional components.

[0084] It should be noted that the multi-band antenna 1000, as illustrated and described in connection with Figs. 1A to ID, is provided merely as a non-limiting example. Multi-band antennas, in general, are well-known in the art. It is for the sake of brevity, only one first radiating unit 102, and four radiating subunits 104a-d of the second radiating unit 104 is shown. However, more radiating units (or radiating sub-units) may be provided as part of the antenna 1000 depending on actual needs.

[0085] As will be appreciated by a person skilled in the art, the disclosed technology— particularly the planar radiating structure of the first radiating unit— can be implemented in any suitable multi-band antenna configuration known in the art. In the following, the planar radiating structure of the first radiating unit 102 will be further described through a series of examples, in connection with Fig. 2 to Fig. 6.

[0086] Throughout Fig. 2 to 6, like components are depicted in the drawings having like reference numbers iterated by a factor of 100. It is to be further noted that any features or aspects described in connection with one of the examples of Fig. 2 to 6 are applicable to the other examples as well, unless stated otherwise.

[0087] Figure 2 illustrates, by way of a first example, a planar radiating structure 200 in accordance with some embodiments. The planar radiating structure 200 (or "radiating structure 200" for short) may form part of the multi-band antenna 1000 as described in the foregoing. More specifically, the radiating structure 200 may form part of the first radiating unit 102 as described above. Put differently, the planar radiating structure 200 may constitute the radiating structure of the first radiating unit 102 of the multi-band antenna 1000. The radiating structure 200 is thus configured to operate on the first frequency band.

[0088] The planar radiating structure 200 may also be referred to as a planar dipole radiating structure. Since the planar radiating structure 200 comprises at least one dipole radiating element. In the illustrated example, the planar radiating structure 200 is a dual-polarized radiating structure 200. More specifically, the radiating structure 200 comprises a first dipole radiating element and a second dipole radiating element. The first and second dipole radiating elements being configured to emit electromagnetic waves at different polarizations (as further explained in the foregoing). It is however to be noted that in some embodiments of the disclosed technology, the planar radiating structure 200 comprises only one dipole radiating element. Thus, the radiating structure 200 may alternatively be a single-polarized radiating structure 200.

[0089] P112264W001More specifically, the radiating structure 200 comprises a first dipole arm 212a and a second dipole arm 212b. The first and second dipole arms 212a, 212b, are arranged to form the first dipole radiating element. The first dipole arm 212a may be coupled to a feeding line (or a microstrip line) delivering a driving signal to the first dipole radiating element, while the second dipole arm 212b is coupled to ground. The radiating structure 200 further comprises a third dipole arm 212c and a fourth dipole arm 212d. The third and fourth dipole arms 212c, 212d are arranged to form the second dipole radiating element. Similar to the first dipole radiating element, the second dipole element may be coupled to a feeding network to receive a driving signal. The dipole arms of the first and second dipole radiating elements may be arranged as cross-coupled dipole arms.

[0090] The first, second, third and fourth dipole arms 212a-d are herein shown to be of the same shape and size. It is however to be noted that the first, second, third and fourth dipole arms 212a-d need not all be of the same shape and / or size. Depending on the specific application, the dipole arms 212a-d may have different shapes and / or sizes.

[0091] As described above, the first dipole radiating element may be of a first polarization, and the second dipole radiating element may be of a second polarization. Put differently, the first and second dipole radiating elements may be configured to emit electromagnetic waves with the first and second polarization respectively. The first polarization may be orthogonal to the second polarization.

[0092] Each dipole arm 202a, 202b, 212c, 212d comprises a plurality of filtering unit cells 214. The filtering unit cells 214 are configured to serve as a band-pass filter for frequencies within the second frequency band of the multi-band antenna 1000. As mentioned in the foregoing, the second frequency band is different from the first frequency band. The second frequency band being the frequency band which a second radiating unit of the multi-band antenna being configured to operate on. In some embodiments, the second frequency band is higher than the first frequency band. In other words, the first frequency band may be a (relatively) low frequency band, while the second frequency band is a (relatively) high frequency band. The first frequency band can be overlapping with the second frequency band. In the alternative, the first frequency band and the second frequency band do not have any common frequency range.

[0093] The plurality of filtering unit cells 214 of each dipole arm can together form an impedance filter structure. As will be further elaborated upon below in connection with Fig. 5 and 6, the impedance filter structure may be further formed by one or more intermediate stubs or one or more intermediate multi-stepped impedance resonating structure, provided between neighboring filtering unit cells. The impedance filter structure (or multi-section stepped impedance filter, MSF) are then configured such as to serve as a band-pass filter for frequencies within a second frequency band. This can effectively make the planar P112264W001radiating structure 200 transparent for frequencies within the second frequency band. The MSF can be realized by a number of multi-stepped impedance resonating structures, arranged in a specific fashion, as will be explained in the following.

[0094] In Fig. 2, a zoomed in portion of one of the filtering unit cells 214 is shown. The filtering unit cell 214 comprises two multi-stepped impedance resonating structures (or "MSRs" for short). More specifically, the filtering unit cell 214 comprises a first multi-stepped impedance resonating structure 216a, and a second multi-stepped impedance resonating structure 216b. It is however to be noted that the filtering unit cell 214 may comprise any number of multi-stepped impedance resonating structures 216a, 216b. Specifically, the filtering unit cell 214 may comprise two or more multi-stepped impedance resonating structures 216a, 216b. The filtering unit cell 214 further comprises a connecting strip 220 connecting the two or more multi-stepped impedance structures 216a, 216b. In other words, the connecting strip 220 electrically couples the two or more multi-stepped impedance structures 216a, 216b. Moreover, the connecting strip 220 may have a relatively high impedance (e.g. as compared to the impedance of the MSRs). The multi-stepped impedance structures 216a, 216b can thus provide a capacitance required for the filtering unit cell 214 and the high impedance connecting strip 220 provides the required inductance for the filtering unit cell 214 to operate with its intended filtering effect (by creating a wideband LC filtering structure).

[0095] The MSRs 216a, 216b may be formed by a respective metal strip 218. The metal strip (as with the connecting strip 220) should herein be interpreted broadly, as it may encompass any suitable conductive structure, such as conductive lines on a substrate, a sheet metal structure, or a combination thereof.

[0096] Each multi-stepped impedance resonating structure 216a, 216b may be connected in one end (may also be referred to as a first end 230a) to a respective connecting point 238a, 238b on a metal ring structure 222 of the dipole arms. The ring structure will be further explained below. The solid black circles representing the connecting points are simply for illustrative purpose. The connecting strip 220 may thus constitute a part of the metal ring structure 222 which is located between the connecting points of the multi-stepped impedance resonating structures 216a, 216b of a certain filtering unit cell 214. The connecting points may thus be understood as the points or portion where the multi-stepped impedance resonating structure 216a, 216b connects to the metal ring structure 222.

[0097] Another end (may also be referred to as a second end 230b) of the multi-stepped impedance resonating structure 216a, 216b may be a free end. However, in some embodiments, the second end 230b may be connected to another multi-stepped impedance resonating structure 216a, 216b (of the dipole arm to which they both belong). The two connected multi-stepped impedance resonating structures 216a, 216b may either belong to the same filtering unit cell 214, or different filtering unit cells 214.

[0098] P112264W001It should be noted that there is no requirement on the connecting manner between the MSRs, the connecting strip, or the metal ring structure. Terms such as "connecting point", "connected to" and "connection" are not intended to limit the connecting manner to be physically connections, instead, it generally refers to an electronic connection or coupling between two elements. The connection may be implemented in many forms, such as direct physical connections or indirect couplings, such as capacitive couplings.

[0099] Each metal strip 218 forming the MSRs 216a, 216b has at least two sections of different impedances. The different impedances can e.g. be realized through having different widths of the at least two sections. For example, the MSR 216a, 216b may comprise at least a higher impedance section and a lower impedance section. Put differently, the MSR 216a, 216b may comprise a (relatively) wide section and a (relatively) narrow section. The MSR can effectively be represented by a set of impedance lines connected in series, where each impedance line has a certain length, and a certain width.

[0100] In the illustrated example, it is shown on the second multi-stepped impedance resonating structure 216b, how it can have three different sections with different widths. A first section 232a has a first width, as indicated by the distance Wl. A second section 232b has a second width, as indicated by the distance W2. A third section 232c has a third width, as indicated by the distance W3. In the illustrated example, the different widths relate to each other as W3 < Wl < W2. This is however only to be seen as a nonlimiting example. The physical characteristics defining the shape of the multi-stepped impedance resonating structures, can be determined as an optimization problem with the physical characteristics as variables. Techniques for solving such problems are known in the art. By optimizing the length and width of the different sections, different impedances and electrical lengths can be obtained to tune the filtering characteristics to have a desired effect.

[0101] It is to be appreciated that the first and second multi-stepped impedance resonating structures 216a, 216b are herein shown in a bent configuration. Put differently, the metal strip making up the MSR may curve (or turn) along its extension. Having a bent configuration may be advantageous from a structural perspective, e.g. to save space and make the radiating structure 200 more compact. However, in some embodiments, the MSR may be formed by a straight structure.

[0102] Since the multi-stepped impedance resonating structures are bent, the different sections of the MSR having different impedance can be divided differently, depending on how you look at it. For illustrative purposes, dashed lines are used to shown one example of how the multi-stepped impedance resonating structures can be divided into the different sections (first through third section 232a-c). It is however to be noted that this division is merely illustrative, and does not have to correlate to an actual structural or

[0103] P112264W001physical division. To further explain how the multi-stepped impedance resonating structures can be formed, reference will in the following be made to Fig. 8A.

[0104] Fig. 8A shows an equivalent circuit of the filtering unit cell 214 as shown in Fig. 2. The first and second multi-stepped impedance resonating structure 216a, 216b are represented by a respective leg of sections with different impedance (e.g. the first, second and third section 232a, 232b, 232c above). Each leg being connected to their respective connecting point 238a, 238b. As is further shown in Fig. 8A, the filtering unit cell 214 may further comprise connecting points 240a, 240b to a respective neighboring filtering unit cell (not shown).

[0105] The different sections are herein represented by a respective electrical circuit component defining the properties of the respective section. The electrical circuit components of one leg are connected in series to form the multi-stepped impedance resonating structure 216a, 216b. Looking e.g. at the first multistepped impedance resonating structure 216a, the first section 232a is represented by a first electrical circuit component having a first impedance Zl. The first electrical circuit component may further have a first width W1 and a first length LI. The second section 232b is represented by a second electrical circuit component having a second impedance Z2. The second electrical circuit component may further have a second width W2 and a second length L2. Lastly, the third section 232c is represented by a third electrical circuit component having a third impedance Z3. The third electrical circuit component may further have a third width W3 and a third length L3. The same holds for the second multi-stepped impedance resonating structure 216b.

[0106] As further shown in Fig. 8A, the connecting strip 220 can be represented by a fourth electrical circuit component having a fourth impedance Z4. The fourth electrical circuit component may further have a fourth width W4 and a fourth length L4.

[0107] Moreover, the filtering unit cell 214 may further comprise fifth electrical circuit components 242a, 242b arranged between the connecting points 238a, 238b for the multi-stepped impedance resonating structures 216a, 216b and the connecting points 240a, 240b for the neighboring filtering unit cell. The fifth electrical circuit components may have a fifth impedance Z5. The fifth electrical circuit component may further have a fifth width W5 and a fifth length L5. It should be noted that even though the different electrical circuit components have impedances, widths and lengths denoted by different labels (i.e. "first", "second", "third" etc.) some (or all) of the electrical circuit components may have the same values of the impedance, width and / or length.

[0108] Fig. 8B herein illustrates a circuit equivalent of another example. The circuit in Fig. 8B comprises the structure of Fig. 8A, with the addition of some further electrical circuit components. More specifically,

[0109] P112264W001each of the multi-stepped impedance resonating structures 216a, 216b comprises a respective sixth electrical circuit component 232d and a respective seventh electrical circuit component 232e. The sixth and seventh electrical circuit components 232d, 232e may represent a respective sixth and seventh section of the filtering unit cell 214. As shown herein, the sixth electrical circuit component 232d may be connected at a point between the first electrical circuit component 232a and the second electrical circuit component 232b. Similarly, the seventh electrical circuit component 232e may be connected at a point between the second electrical circuit component 232b and the third electrical circuit component 232c. The sixth electrical circuit component 232d may have a sixth impedance Z6. The sixth electrical circuit component 232d may further have a sixth width W6 and a sixth length L6. The seventh electrical circuit component 232e may have a seventh impedance 7J . The seventh electrical circuit component 232e may further have a seventh width W7 and a seventh length L7.

[0110] The physical characteristics may comprise the number of sections with different impedances, a length and width of each section, a thickness of the conductor, and how the impedances of the different sections relate to each other. The physical characteristics may further comprise the number of multistepped impedance resonating structures, distance between the multi-stepped impedance resonating structures, and how they are distributed around the dipole arm. Moreover, the properties of the MSR can be selected in view of what frequency band it should serve as a band-pass filter for. More specifically, one or more physical characteristics of the multi-stepped impedance resonating structures 216a, 216b may be set so as to have a band-pass behavior for frequencies within the second frequency band, and a band-stop behavior for frequencies within the first frequency band.

[0111] As mentioned above, each dipole arm 202a, 202b, 212c, 212d further comprises a metal ring structure 222. The ring structure may be made of any suitable conductive material. By ring structure, it is herein meant a closed geometric structure or a closed loop, which forms an enclosed area or space. It should be appreciated that the ring structure is not limited to a circular shape. Instead, it can encompass any structure which forms a closed path. For example, the term can encompass (but is not limited to) rectangular, square, polygonal, circular, or elliptical shapes. Moreover, the ring structure can be either a regular / symmetric shape, or an irregular / asymmetric shape. Even further, the ring structure can either have a uniform or a non-uniform cross-section. The ring structure may e.g. have different cross-sectional areas or widths at different sections around the ring structure. As shown in Fig. 2, the metal ring structure 222 may form the connecting strips 220 between the multi-stepped impedance structures 216a, 216b of the respective dipole arm. Put differently, the connecting strips 220 may be seen as different portions of the metal ring structure (i.e. a portion of the metal ring structure connecting the MSRs of the filtering unit cell). As stated above, the connecting strip 220 may have a relatively high impedance. Thus, the ring structure 222 being formed by the connecting strips 220, may also have a relatively high impedance. In P112264W001other words, the ring structure may be relatively thin (i.e. a small width), e.g. in comparison with the widths of the multi-stepped impedance resonating structures 216a, 216b.

[0112] It is to be appreciated that the ring structure, as described herein, is known in the art for realizing a dipole arm. The disclosed technology can thus be realized by employing the proposed filtering unit cells 214 in any existing ring-shaped dipole arm.

[0113] In the illustrated example, each dipole arm 212a, 212b, 212c, 212d comprises four filtering unit cells 214. It is however to be appreciated that any number of filtering unit cells 214 may be possible. The plurality of filtering unit cells 214 are distributed around the metal ring structure 222. In other words, the plurality of filtering unit cells may be distributed around a central axis of the metal ring structure 222. Or more generally, along an outer region of the respective dipole arms, or along a perimeter of the metal ring structure 222. More specifically, the two or more filtering unit cells 214 may be distributed uniformly along the metal ring structure 222 of the respective dipole arm 212a-d. However, in some embodiments, the two or more filtering unit cells 214 may be distributed non-uniformly along the metal ring structure 222 of the respective dipole arm 212a-d. Moreover, the two or more filtering unit cells 214 may be symmetrically distributed along the metal ring structure 222 of the respective dipole arm 212a-d. However, in some embodiments, the two or more filtering unit cells 214 may be asymmetrically distributed along the metal ring structure 222 of the respective dipole arm 212a-d.

[0114] In some embodiments, and as illustrated herein, the multi-stepped impedance resonating structures 216a, 216b of the filtering unit cells 214 can be arranged at an inner periphery of the metal ring structure 222. Put differently, the multi-stepped impedance resonating structures 216a, 216b may be arranged along an inner boundary of the metal ring structure 222. This may provide for a space efficient structure. It is however to be noted that the multi-stepped impedance resonating structures 216a, 216b of the filtering unit cells 214 may as well be arranged at an outer periphery of the metal ring structure 222. I.e. along an outer boundary of the metal ring structure 222.

[0115] The dipole arms 212a-d may be formed as electrically conductive elements arranged on or within a substrate, such as a printed circuit board. The dipole arms 212a-d may for instance be formed by a microstrip structure on the substrate. Such an example is shown in Fig. 3. Alternatively, or in combination, the dipole arms 212a-d may be formed by a stripline structure. In other words, the dipole arms 212a-d may be provided as electrically conductive elements within the substrate. The electrically conductive elements may e.g. be formed by etching of a metal layer on the substrate. In another example, the dipole arms 212a-d may be formed by a metal structure. For example, the dipole arms 212a-d can be formed from a sheet metal, e.g. by metal punching / stamping, die casting, or any other suitable metal cutting techniques.

[0116] P112264W001The dipole arms 212a-d may be formed as a single piece design. In other words, each dipole arm 212a-d may be formed as one integral structure. The term "integral" refers to a unitary or one-piece structure made of a single material and does not include structures formed by e.g. welding, soldering or gluing several pieces together. Thus, the term "integral structure" refers to that the structure is a monolithic structure. Accordingly, the term "integral" may be interchanged with the term "monolithic". Thus, each dipole arm 212a-d may be a monolithic metal structure. In such case, the multi-stepped impedance resonating structures 216a, 216b can be seen as the portions which extends inwards (or outwards) from the ring structure 222.

[0117] It is however to be appreciated that each dipole arm 212a-d may be formed by a plurality of individual components as well. In other words, the dipole arms 212a-d may each be formed as a multi-piece design. For example, the MSRs can be formed as separate parts, which are then joined or coupled to the ring structure 222, e.g. though welding or any other suitable means for connecting two conductive parts. It is further to be noted that the planar radiating structure 200 may comprise additional parts or components, such as structural parts for mounting.

[0118] The radiating structure 200 (specifically the multi-stepped impedance resonating structures 216a, 216b of the filtering unit cells 214 of the respective dipole arm 212a-d) is specifically designed to realize an MSF response over a second frequency band of 1.7 GHz to 2.7 GHz. In other words, the plurality of filtering unit cells 214 of the radiating structure 200 are configured to serve as a band-pass filter for said frequency range, thereby making the radiating structure 200 transparent to said frequency band. In the following, reference will be made to Fig. 3 to 6. These figures show different examples / variants of the planar radiating structure 200 as described above in connection with Fig. 2. The radiating structures 300, 400, 500, 600 of Fig. 3 to 6 share many features with the radiating structure 200 of Fig. 2. Any aspects or features described in connection with one example, is applicable also to the other examples, unless otherwise stated. To avoid undue repetition, focus will in the following mainly be at what differs (or distinguishes) the examples from each other.

[0119] Figure 3 illustrates a second example of the planar radiating structure 300, in accordance with some embodiments. The planar radiating structure 300 mainly differs from the radiating structure 200 as described above in connection with Fig. 2 in its structural design of the multi-stepped impedance resonating structures 316a, 316b.

[0120] As with the radiating structure 200 described above, the present radiating structure 300 comprises a first to fourth dipole arm 312a-d. The radiating structure 300 as depicted herein, are realized as a structure on a substrate 324, such as a PCB. The radiating structure 300 (specifically the multi-stepped P112264W001impedance resonating structures 316a, 316b of the filtering unit cells 314 of the respective dipole arm 312a-d) is specifically designed to realize an MSF response over a second frequency band of 2.3 GHz to 4.2 GHz. In other words, the plurality of filtering unit cells 314 of the radiating structure 300 are configured to serve as a band-pass filter for said frequency range.

[0121] Figure 4 illustrates a third example of the planar radiating structure 400, in accordance with some embodiments. In addition to what has been described in the foregoing, the planar radiating structure 400 of Fig. 4 further has a plurality of filtering unit cells 414, where each multi-stepped impedance resonating structures 416a, 416b of said filtering unit cells 414 comprises a cut-out 436. The cut-out 436 may be a circular hole through the metal strip 418 making up the MSR 416a, 416b, as shown herein. The cut-outs 436 may however take other shapes as well. Moreover, more than one cut-out 436 may be provided at each MSR 416a, 416b. The cut-outs may facilitate mechanical fixation of the planar radiating structure 400. They may further provide for improved radiating characteristics of the radiating structure 400, and / or weight savings.

[0122] It goes without saying that the cut-outs 436 as described herein, in connection with Fig. 4, may be implemented as part of any of the other examples of the radiating structure as shown in Fig. 2 to 3 and 5 to 6.

[0123] Figure 5 illustrates a fourth example of the planar radiating structure 500, in accordance with some embodiments. The planar radiating structure 500 as shown herein, shows an example where each filtering unit cell 514 comprises three multi-stepped impedance resonating structures 516a, 516b, 516c. More specifically, each filtering unit cell 514 comprises a first multi-stepped impedance resonating structure 516a, a second multi-stepped impedance resonating structure 516b, and a third multi-stepped impedance resonating structure 516c. The third multi-stepped impedance resonating structure 516c being located between the first multi-stepped impedance resonating structure 516a and the second multi-stepped impedance resonating structure 516b. Put differently, the connecting point of the third MSR 516c to the connecting strip 520 (or to the metal ring structure 522) is located at a point along the connecting strip 520 (or the metal ring structure 522) between the connecting point of the first MSR 516a and the connecting point of the second MSR 516c. Having a third multi-stepped impedance resonating structure 516c may further help in suppressing the unwanted resonance over a wider bandwidth, for achieving a wider transparency bandwidth, as well as further suppressing the cross-band scattering.

[0124] As is further shown in Fig. 5, each dipole arm 512a-d may further comprise an intermediate stub 526. The intermediate stub may be formed by a metal strip. The metal strip may be connected in one end to

[0125] P112264W001the metal ring structure 522 between two neighboring filtering unit cells 514. The other end of the intermediate stub 516 may be a free end. By the wording stub, it is herein meant a structure which protrudes from the metal ring structure 522, and which has a constant width. Thus, in contrast to the multi-stepped impedance resonating structures 516a, 516b, 516c, is has a constant impedance (or width) along its direction of extension.

[0126] It is to be noted that the intermediate stub 526 is not limited to be used in connection with an embodiment in which each filtering unit cell 514 comprises three MSRs, as shown herein. The intermediate stub 526 may as well be combined with embodiments having just two MSRs, e.g. as the examples in Fig. 2-4, or more than three MSRs.

[0127] Figure 6 illustrates a fifth example of the planar radiating structure 600, in accordance with some embodiments. Similar to Fig. 5, the radiating structure 600 of Fig. 6 where the filtering unit cells 614 comprises three structures. Namely a first and second multi-stepped impedance resonating structure 616a, 616b, as well as a third structure 616c. The third structure 616c being arranged between the first and second MSR 616a, 616b.

[0128] In the illustrated example, the third structure 616c is a stub. In other words, the third structure 616c may be a structure having a constant width along its direction of extension. It is however to be appreciated that the third structure 616c may, in some embodiments, be a third multi-stepped impedance resonating structure.

[0129] As further shown in Fig. 6, each dipole arm further comprises an intermediate multi-stepped impedance resonating structure 628. The intermediate multi-stepped impedance resonating structure 628 may be formed by a metal line having at least two portions of different impedance. Moreover, the metal line may be connected in one end to the metal ring structure 622 between two neighboring filtering unit cells 614. The other end of the intermediate multi-stepped impedance resonating structure 628 may be a free end. By having an intermediate stub 526 or an intermediate multi-stepped impedance resonating structure 628 can further help in suppressing a radar cross section (RCS) over a wider bandwidth. The above illustrated examples merely serve as non-limiting examples. For altering the embodiments, parameters such as positions of the MSRs around the ring structure, the number of MSRs in each filtering unit cell, the number of filtering unit cells, the shape and size of the ring structure, the thickness or fatness of the ring structure, the presence / non-presence and configuration of intermediate stubs or MSRs could all be changed or modified by those skilled in the art, without departing from the scope of the present application.

[0130] P112264W001Fig. 7 is a schematic illustration of a network node 700 in accordance with some embodiments. The network node 700 may for instance be used in mobile communication networks, or in testing scenarios. The network node 700 may e.g. be a base station in a cellular network, or a network router or access point in a wireless local area network. As used herein, network node 700 refers to a device or unit capable, configured, arranged and / or operable to transmit and / or receive signals using electromagnetic waves, such as radio waves. In particular, the network node 700 may communicate over wide- or ultrawide-band, by which it is meant a wide range of frequencies, including, but not limited to 4G, 5G, 6G, and millimeter wave (mmWave) bands. In particular, the network node 700 is configured to communicate over multiple frequency bands. Specifically, the antenna 1000 can be designed to operate at a first frequency band and a second frequency band. The first frequency band may e.g. be in the range of 0.6 GHz to 0.96 GHz. The second frequency band may e.g. be in the range of 1.7 GHz to 2.7 GHz, or in the range of 2.3 GHz to 4.2 GHz, or in the range of 5 to 9 GHz (e.g., 5.9 to 8.4 GHz), or in the range of 10-16 GHz (e.g., 10.7 to 15.35 GHz). However, also other frequency bands are possible.

[0131] The network node 700 may communicate with other network nodes, or any type of mobile communication enabled device, such as a smart phone, a mobile phone, a wearable terminal device, a wireless endpoint, a mobile station, a tablet, a laptop, a vehicle etc.

[0132] The network node 700 may comprise processing circuitry 708 (may also be referred to as control circuitry 708) and a memory 710. The processing circuitry 708 may be configured to perform the overall functions and operations of the network node 700. The processing circuitry 708 may be distributed over several circuitry devices. The processing circuitry 708 may comprise one or more processors, such as a central processing unit (CPU), microcontroller, or microprocessor. The one or more processors may be configured to execute program code stored in the memory 710, in order to carry out various functions and operations of the network node 700. The processor(s) may be or include any number of hardware components for conducting data or signal processing or for executing computer code stored in the memory 710. The memory 710 optionally includes high-speed random-access memory, such as DRAM, SRAM, DDR RAM, or other random-access solid-state memory devices; and optionally includes nonvolatile memory, such as one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid-state storage devices. The memory 710 may include database components, object code components, script components, or any other type of information structure for supporting the various activities of the disclosed technology. Furthermore, the processing circuitry 708 may include baseband processing circuitry and application processing circuitry.

[0133] As illustrated in Fig. 7, the network node 700 comprises an antenna such as the antenna 1000 as described above in connection with Fig. 1. The antenna 1000 may be connected to an interface 702 of

[0134] P112264W001the network node 700. The interface 702 may comprise RF front-end circuitry 704 and the antenna 1000. The RF front-end circuitry 704 may comprises one or more filters, one or more amplifiers (e.g. VGAs and LGAs), one or more mixers, one or more ADCs, one or more PLLs, and one or more DACs. The RF frontend circuitry 704 is connected to the antenna 1000 and processing circuitry 708, and is configured to condition signals communicated between antenna 1000 and processing circuitry 708. The RF front-end circuitry 704 may be coupled to or a part of the antenna 1000. In some embodiments, the network node may not include separate RF front-end circuitry 704, rather, the processing circuitry 712 may comprise RF front-end circuitry and may be connected to antenna 1000.

[0135] Similarly, in some embodiments, the RF front-end circuitry 704 may perform the functions of a radio (frequency) transceiver. More specifically, the RF front-end circuitry 704 may receive digital data that is to be transmitted by the antenna 1000. The RF front-end circuitry 704 may convert the digital data into a radio signal (or driving signal) having the appropriate channel and bandwidth parameters using a combination of components of the RF front-end circuitry 704. The radio signal may then be transmitted via the antenna 1000. Similarly, when receiving data, the antenna 1000 may collect radio signals which are then converted into digital data by the RF front-end circuitry 704. The digital data may be passed to processing circuitry 708. In other embodiments, the interface 702 may comprise different components and / or different combinations of components.

[0136] The power source 712 may, in some embodiments, be in the form of a battery or battery pack. Other types of power sources, such as an external power source (e.g., an electricity outlet), photovoltaic devices or power cells, may also be used. The network node 700 may further comprise power circuitry 706 for delivering power from power source 712 to the various parts of the network node 700 which need power from power source 712 to carry out any functionality described or indicated herein. Power circuitry 706 may in certain embodiments comprise power management circuitry. Power circuitry 706 may additionally or alternatively be operable to receive power from an external power source, in which case the network node 700 may be connectable to the external power source (such as an electricity outlet) via input circuitry or an interface such as an electrical power cable. The power circuitry 706 may also in certain embodiments be operable to deliver power from an external power source to the power source 712. This may be, for example, for the charging of the power source 712. The power circuitry 706 may perform any formatting, converting, or other modification to the power from the power source 712 to make the power suitable for the respective components of the network node 700 to which power is supplied.

[0137] In the drawings and specification, there have been disclosed exemplary aspects of the disclosed technology. However, many variations and modifications can be made to these aspects without

[0138] P112264W001substantially departing from the principles of the disclosed technology. Thus, the disclosed technology should be regarded as illustrative rather than restrictive, and not as being limited to the particular aspects discussed above. Accordingly, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation.

[0139] Exemplary embodiments of a planar radiating structure, as well as an antenna and network node thereof, are set out in the following items.

[0140] Item 1. A planar radiating structure for a multi-band antenna, wherein said radiating structure is configured to operate on a first frequency band, the radiating structure comprising:

[0141] a first dipole arm and a second dipole arm arranged to form a first dipole radiating element; wherein each dipole arm comprises a plurality of filtering unit cells configured to serve as a band-pass filter for frequencies within a second frequency band, different from the first frequency band;

[0142] wherein each filtering unit cell comprises:

[0143] two or more multi-stepped impedance resonating structures, each formed by metal strips having at least two sections of different impedances, and

[0144] a connecting strip connecting the two or more multi-stepped impedance resonating structures.

[0145] Item 2. The planar radiating structure according to item 1, wherein the planar radiating structure further comprises a third dipole arm and a fourth dipole arm arranged to form a second dipole radiating element.

[0146] Item 3. The planar radiating structure according to item 2, wherein the first dipole radiating element is of a first polarization, and the second dipole radiating element is of a second polarization.

[0147] Item 4. The planar radiating structure according to item 3, wherein the first polarization is orthogonal to the second polarization.

[0148] Item 5. The planar radiating structure according to any one of the items 1 to 4, wherein the second frequency band is higher than the first frequency band.

[0149] Item 6. The planar radiating structure according to any one of the items 1 to 5, wherein each dipole arm further comprises a metal ring structure.

[0150] P112264W001Item 7. The planar radiating structure according to item 6, wherein the metal ring structure is of a rectangular shape, a square shape, a polygonal shape, a circular shape, or an elliptical shape.

[0151] Item 8. The planar radiating structure according to item 6 or 7, wherein the multi-stepped impedance resonating structures of the filtering unit cells are arranged at an inner periphery of the metal ring structure.

[0152] Item 9. The planar radiating structure according to item 6 or 7, wherein the multi-stepped impedance resonating structures of the filtering unit cells are arranged at an outer periphery of the metal ring structure.

[0153] Item 10. The planar radiating structure according to any one of the items 6 to 9, wherein the two or more filtering unit cells are distributed uniformly along the metal ring structure of the respective dipole arm.

[0154] Item 11. The planar radiating structure according to any one of the items 6 to 9, wherein the two or more filtering unit cells are distributed non-uniformly along the metal ring structure of the respective dipole arm.

[0155] Item 12. The planar radiating structure according to any one of the items 6 to 11, wherein the two or more filtering unit cells are symmetrically distributed along the metal ring structure of the respective dipole arm.

[0156] Item 13. The planar radiating structure according to any one of the items 6 to 11, wherein the two or more filtering unit cells are asymmetrically distributed along the metal ring structure of the respective dipole arm.

[0157] Item 14. The planar radiating structure according to any one of the items 6 to 13, wherein one end of each multi-stepped impedance resonating structure is connected to a respective connecting point on the metal ring structure, and the other end of the multi-stepped impedance resonating structure is a free end.

[0158] Item 15. The planar radiating structure according to any one of the items 1 to 14, wherein each dipole arm further comprises an intermediate stub, formed by a metal strip, and connected in one end to the metal ring structure between two neighboring filtering unit cells.

[0159] P112264W001Item 16. The planar radiating structure according to any one of the items 1 to 15, wherein each dipole arm further comprises an intermediate multi-stepped impedance resonating structure, formed by a metal line having at least two portions of different impedance, and connected in one end to the metal ring structure between two neighboring filtering unit cells.

[0160] Item 17. The planar radiating structure according to any one of the items 1 to 16, wherein the radiating structure forms part of a first radiating unit of the multi-band antenna, and wherein the second frequency band is a frequency band on which a second radiating unit of the multi-band antenna operates.

[0161] Item 18. The planar radiating structure according to any one of the items 1 to 17, wherein one or more physical characteristics of the multi-stepped impedance resonating structures are set so as to have a band-pass behavior for frequencies within the second frequency band, and a band-stop behavior for frequencies within the first frequency band.

[0162] Item 19. The planar radiating structure according to any one of the items 1 to 18, wherein each dipole arm is a monolithic metal structure.

[0163] Item 20. The planar radiating structure according to any one of the items 1 to 19, wherein each dipole arm is formed by a microstrip structure.

[0164] Item 21. The planar radiating structure according to any one of the items 1 to 20, wherein each dipole arm is formed by a stripline structure.

[0165] Item 22. A multi-band antenna comprising:

[0166] a first radiating unit, wherein the first radiating unit comprises a planar radiating structure according to any one of the items 1 to 21; and a second radiating unit, configured to operate on the second frequency band.

[0167] Item 23. The multi-band antenna according to item 22, wherein the multi-band antenna further comprises a base structure, and wherein the second radiating unit is arranged between the base structure and the first radiating unit.

[0168] P112264W001Item 24. The multi-band antenna according to item 22 or 23, wherein the second radiating unit comprises a plurality of radiating sub-units.

[0169] Item 25. The multi-band antenna according to any one of the items 22 to 24, further comprising a feeding network comprising a plurality of feeding lines, wherein the plurality of feeding lines is coupled to the first radiating unit and the second radiating unit, and configured to feed the first radiating unit and the second radiating unit with a driving signal.

[0170] Item 26. A network node comprising the multi-band antenna according to any one of the items 22 to 25.

[0171] P112264W001

Claims

CLAIMS1. A planar radiating structure (200, 300, 400, 500, 600) for a multi-band antenna (1000), wherein said radiating structure (200, 300, 400, 500, 600) is configured to operate on a first frequency band, the radiating structure (200, 300, 400, 500, 600) comprising:a first dipole arm (212a, 312a, 412a, 512a, 612a) and a second dipole arm (212b, 312b, 412b, 512b, 612b) arranged to form a first dipole radiating element;wherein each dipole arm (212a, 312a, 412a, 512a, 612a, 212b, 312b, 412b, 512b, 612b) comprises a plurality of filtering unit cells (214, 314, 414, 514, 614) configured to serve as a band-pass filter for frequencies within a second frequency band, different from the first frequency band;wherein each filtering unit cell (214, 314, 414, 514, 614) comprises:two or more multi-stepped impedance resonating structures (216a, 216b, 316a, 316b, 416a, 416b, 516a, 516b, 516c, 616a, 616b, 616c), each formed by metal strips (218, 318, 418, 518, 618) having at least two sections of different impedances, anda connecting strip (220, 320, 420, 520, 620) connecting the two or more multi-stepped impedance resonating structures (216a, 216b, 316a, 316b, 416a, 416b, 516a, 516b, 516c, 616a, 616b, 616c).

2. The planar radiating structure (200, 300, 400, 500, 600) according to claim 1, wherein the planar radiating structure (200, 300, 400, 500, 600) further comprises a third dipole arm (212c, 312c, 412c, 512c, 612c) and a fourth dipole arm (212d, 312d, 412d, 512d, 612d) arranged to form a second dipole radiating element.

3. The planar radiating structure (200, 300, 400, 500, 600) according to claim 2, wherein the first dipole radiating element is of a first polarization, and the second dipole radiating element is of a second polarization.

4. The planar radiating structure (200, 300, 400, 500, 600) according to claim 3, wherein the first polarization is orthogonal to the second polarization.

5. The planar radiating structure (200, 300, 400, 500, 600) according to any one of the claims 1 to 4, wherein the second frequency band is higher than the first frequency band.P112264W0016. The planar radiating structure (200, 300, 400, 500, 600) according to any one of the claims 1 to 5, wherein each dipole arm (212a-d, 312a-d, 412a-d, 512a-d, 612a-d) further comprises a metal ring structure (222, 322, 422, 522, 622).

7. The planar radiating structure (200, 300, 400, 500, 600) according to claim 6, wherein the metal ring structure (222, 322, 422, 522, 622) is of a rectangular shape, a square shape, a polygonal shape, a circular shape, or an elliptical shape.

8. The planar radiating structure (200, 300, 400, 500, 600) according to claim 6 or 7, wherein the multi-stepped impedance resonating structures (216a, 216b, 316a, 316b, 416a, 416b, 516a, 516b, 516c, 616a, 616b, 616c) of the filtering unit cells (214, 314, 414, 514, 614) are arranged at an inner periphery of the metal ring structure (222, 322, 422, 522, 622).

9. The planar radiating structure (200, 300, 400, 500, 600) according to claim 6 or 7, wherein the multi-stepped impedance resonating structures (216a, 216b, 316a, 316b, 416a, 416b, 516a, 516b, 516c, 616a, 616b, 616c) of the filtering unit cells (214, 314, 414, 514, 614) are arranged at an outer periphery of the metal ring structure (222, 322, 422, 522, 622).

10. The planar radiating structure (200, 300, 400, 500, 600) according to any one of the claims 6 to 9, wherein the two or more filtering unit cells (214, 314, 414, 514, 614) are distributed uniformly along the metal ring structure (222, 322, 422, 522, 622) of the respective dipole arm (212a-d, 312a-d, 412a-d, 512a-d, 612a-d).

11. The planar radiating structure (200, 300, 400, 500, 600) according to any one of the claims 6 to 9, wherein the two or more filtering unit cells (214, 314, 414, 514, 614) are distributed non-uniformly along the metal ring structure (222, 322, 422, 522, 622) of the respective dipole arm (212a-d, 312a-d, 412a-d, 512a-d, 612a-d).

12. The planar radiating structure (200, 300, 400, 500, 600) according to any one of the claims 6 to 11, wherein the two or more filtering unit cells (214, 314, 414, 514, 614) are symmetrically distributed along the metal ring structure (222, 322, 422, 522, 622) of the respective dipole arm (212a-d, 312a-d, 412a-d, 512a-d, 612a-d).

13. The planar radiating structure (200, 300, 400, 500, 600) according to any one of the claims 6 to 11, wherein the two or more filtering unit cells (214, 314, 414, 514, 614) are asymmetrically P112264W001distributed along the metal ring structure (222, 322, 422, 522, 622) of the respective dipole arm (212a-d, 312a-d, 412a-d, 512a-d, 612a-d).

14. The planar radiating structure (200, 300, 400, 500, 600) according to any one of the claims 6 to 13, wherein one end of each multi-stepped impedance resonating structure (216a, 216b, 316a, 316b, 416a, 416b, 516a, 516b, 516c, 616a, 616b, 616c) is connected to a respective connecting point on the metal ring structure (222, 322, 422, 522, 622), and the other end of the multi-stepped impedance resonating structure (216a, 216b, 316a, 316b, 416a, 416b, 516a, 516b, 516c, 616a, 616b, 616c) is a free end.

15. The planar radiating structure (200, 300, 400, 500, 600) according to any one of the claims 1 to 14, wherein each dipole arm (212a-d, 312a-d, 412a-d, 512a-d, 612a-d) further comprises an intermediate stub (526), formed by a metal strip, and connected in one end to the metal ring structure (522) between two neighboring filtering unit cells (514).

16. The planar radiating structure (200, 300, 400, 500, 600) according to any one of the claims 1 to 15, wherein each dipole arm further comprises an intermediate multi-stepped impedance resonating structure (628), formed by a metal line having at least two portions of different impedance, and connected in one end to the metal ring structure (622) between two neighboring filtering unit cells (614).

17. The planar radiating structure (200, 300, 400, 500, 600) according to any one of the claims 1 to 16, wherein the radiating structure (200, 300, 400, 500, 600) forms part of a first radiating unit (102) of the multi-band antenna (1000), andwherein the second frequency band is a frequency band on which a second radiating unit (104) of the multi-band antenna (1000) operates.

18. The planar radiating structure (200, 300, 400, 500, 600) according to any one of the claims 1 to 17, wherein one or more physical characteristics of the multi-stepped impedance resonating structures (216a, 216b, 316a, 316b, 416a, 416b, 516a, 516b, 516c, 616a, 616b, 616c) are set so as to have a band-pass behavior for frequencies within the second frequency band, and a band-stop behavior for frequencies within the first frequency band.P112264W00119. The planar radiating structure (200, 300, 400, 500, 600) according to any one of the claims 1 to 18, wherein each dipole arm (212a-d, 312a-d, 412a-d, 512a-d, 612a-d) is a monolithic metal structure.

20. The planar radiating structure (200, 300, 400, 500, 600) according to any one of the claims 1 to 19, wherein each dipole arm (212a-d, 312a-d, 412a-d, 512a-d, 612a-d) is formed by a microstrip structure.

21. The planar radiating structure (200, 300, 400, 500, 600) according to any one of the claims 1 to 20, wherein each dipole arm (212a-d, 312a-d, 412a-d, 512a-d, 612a-d) is formed by a stripline structure.

22. A multi-band antenna (1000) comprising:a first radiating unit (102), wherein the first radiating unit (102) comprises a planar radiating structure (200, 300, 400, 500, 600) according to any one of the claims 1 to 21; anda second radiating unit (104), configured to operate on the second frequency band.

23. The multi-band antenna (1000) according to claim 22, wherein the multi-band antenna (1000) further comprises a base structure (106), andwherein the second radiating unit (104) is arranged between the base structure (106) and the first radiating unit (102).

24. The multi-band antenna (1000) according to claim 22 or 23, wherein the second radiating unit (104) comprises a plurality of radiating sub-units (104a, 104b, 104c, 104d).

25. The multi-band antenna (1000) according to any one of the claims 22 to 24, further comprising a feeding network comprising a plurality of feeding lines (108a, 108b, 108c, 108d, 108e), wherein the plurality of feeding lines (108a, 108b, 108c, 108d, 108e) is coupled to the first radiating unit (102) and the second radiating unit (104), and configured to feed the first radiating unit (102) and the second radiating unit (104) with a driving signal.

26. A network node (800) comprising the multi-band antenna (1000) according to any one of the claims 22 to 25.P112264W001

Images