Communication device including a retroreflective structure

Abstract

The present invention relates to suppressing surface waves in a communication device (100) for a wireless communication system (500). The communication device (100) includes: a dielectric layer (106) extending along a plane (P) between a base plate (102) and a glass layer (104); an antenna element (108) configured to transmit radio waves (120); and a retroreflective structure (110) extending inside the dielectric layer (106) and located near the antenna element (108), wherein the retroreflective structure (110) is configured to reflect the radio waves (120) at an angle that is not parallel to the plane (P). The retroreflective structure (110) thus prevents parasitic antenna energy from penetrating into surface waves in and behind the glass layer (104) and directs radiation in a desired direction. The radiation pattern and antenna gain are thereby improved.

Description

Technical Field

[0001] The present invention relates to a communication device comprising a retroreflective structure for reflecting radio waves emitted by an antenna element in the communication device. Background Art

[0002] Nowadays, smartphones play an important role in our daily activities, not only for communication, but also for media applications. For example, media applications may involve processing, storing or transmitting audio or video content. Smartphones should be compact and give a powerful feeling, while their prices should remain affordable. A popular design includes a full display screen covered with glass and composed of a sturdy metal alloy frame. Other components such as cameras, batteries and integrated circuits are placed under the glass. In addition, smartphones require high data rates for the transmission of media content. Frequencies above 20 GHz (corresponding to wavelengths in the millimeter wave range) can be used. The antenna implementation under the glass of the smartphone is cumbersome and may result in disturbed radiation patterns and reduced antenna gain, especially at high frequencies. Summary of the invention

[0003] It is an object of embodiments of the present invention to provide a solution that mitigates or solves the disadvantages and problems of conventional solutions.

[0004] The above objects and further objects are solved by the subject-matter of the independent claims. Further advantageous embodiments of the invention can be found in the dependent claims.

[0005] According to a first aspect of the present invention, the above-mentioned objects and other objects are achieved by a communication device for a wireless communication system, the communication device comprising:

[0006] Base plate;

[0007] Glass layer;

[0008] a dielectric layer extending along a plane between the substrate and the glass layer;

[0009] an antenna element configured to transmit radio waves; and

[0010] A retroreflective structure extends within the dielectric layer and is located adjacent the antenna element, wherein the retroreflective structure is configured to reflect radio waves at an angle that is not parallel to the plane.

[0011] The retroreflective structure can be configured to have a reflection angle that is the same as the incident angle and may also be referred to as a reflective metasurface, an anomalous reflective metasurface, or a beam shaping metasurface.

[0012] The retroreflective structure being located near the antenna element is understood herein to mean that the interaction between the retroreflective structure and the antenna element is the so-called near field and occurs before the radio waves form a wavefront. The distance between the retroreflective structure and the antenna element may be, for example, less than half the wavelength of the radio waves.

[0013] The dielectric layer may be understood herein as various components distributed between the bottom plate and the glass layer of the communication device. The components of the dielectric layer vary for different positions of the antenna element in the communication device. In an embodiment, the antenna element may be arranged at the back surface of the communication device. Non-limiting examples of dielectric layers may include an air-filled gap between adjacent components, a foam or plastic structure used as a spacer, a dielectric substrate of a printed circuit board, and the like. In an embodiment, the antenna element may be arranged as the edge of the communication device. Non-limiting examples of dielectric layers may include insert molding, plastic components, foam or plastic structures, and dielectric substrates of printed circuit boards. In another embodiment, the antenna element may be arranged at the display surface of the communication device. Non-limiting examples of dielectric layers may include the structure of a display, including a polarizing film, an adhesive film, an organic light emitting diode (OLED) substrate, and a liquid crystal (LC) film.

[0014] The communication device according to the first aspect has the advantage that it prevents parasitic antenna energy from penetrating into surface waves in and behind the glass layer, but instead directs the radiation in a desired direction, thereby improving the radiation pattern and gain of the antenna element in the communication device.

[0015] In an implementation form of the communication device according to the first aspect, the retroreflective structure has a non-uniform impedance along its extension in the dielectric layer.

[0016] The advantage of this implementation is that it can achieve a small area of ​​the retroreflective structure (eg, less than half the wavelength) while preventing the antenna energy from parasitically penetrating into the surface waves, thereby improving the radiation pattern.

[0017] In an implementation form of the communication device according to the first aspect, the retroreflective structure is conductively or capacitively coupled to the antenna element.

[0018] The advantage of this embodiment is that the structure is strongly excited by the near field of the antenna element and thus effectively reflects the radiation in the desired direction.

[0019] In an implementation form of the communication device according to the first aspect, the first end of the retroreflective structure is conductively or capacitively coupled to the antenna element.

[0020] The advantage of this implementation is that the parasitic path between the back-reflecting structure and the antenna ground plane is eliminated. Since the back-reflecting structure is coupled to the antenna element and therefore does not allow the guided mode to be excited, the guided mode is parasitic to the antenna, and the non-radiated electromagnetic (EM) energy guided along the dielectric layer is reducing the radiated EM energy. Therefore, the disclosed implementation eliminates the waves propagating along the ground plane inside the dielectric layer, thereby further improving the antenna efficiency.

[0021] In an implementation form of the communication device according to the first aspect, the retroreflective structure is located within a range r less than half the wavelength of the radio wave from the antenna element.

[0022] The advantage of this implementation form is that the occupied area of ​​the retroreflective structure is minimized and the performance of other device components allocated under the glass is not impaired.

[0023] In an implementation form of the communication device according to the first aspect, the antenna element is arranged perpendicularly or parallel to the plane of the dielectric layer.

[0024] The advantage of this implementation is that the retroreflective structure can work with antennas of different configurations. For example, an antenna aperture generally parallel to the plane of the dielectric layer provides broadside beamforming radiation. An antenna aperture generally perpendicular to the plane of the dielectric layer provides endfire beamforming radiation.

[0025] In an implementation form of the communication device according to the first aspect, the retroreflective structure has an extension inside the dielectric layer that is smaller than half the wavelength of the radio waves.

[0026] The advantages of this implementation form are: compact structure and no impairment of the performance of other devices located under the glass layer.

[0027] In an implementation form of the communication device according to the first aspect, the retroreflective structure is a conductive film.

[0028] The advantage of this implementation form is that it is easy to manufacture as a patterned metal layer.

[0029] In an implementation form of the communication device according to the first aspect, the conductive film includes a solid conductive film.

[0030] The advantage of this implementation is that the fabrication of the solid conductive film enables a cost-effective design.

[0031] In an implementation form of the communication device according to the first aspect, the conductive film includes a capacitive element and an inductive element forming a capacitive and inductive pattern.

[0032] The advantage of this implementation is that this arrangement enables the required surface impedance for the operation of the retroreflective structure to be achieved. This implementation enables design synthesis of antenna beam shaping. The conductive film can be configured to reflect radio waves at angles that are not parallel to the plane.

[0033] In an implementation form of the communication device according to the first aspect, a size of each capacitive element and each inductive element is smaller than a quarter of a wavelength of a radio wave.

[0034] The advantage of this implementation is that the retroreflective structure acts as a non-uniform impedance boundary, as required for the operation of the retroreflective structure. This enables a non-resonant frequency response. Thus, for each frequency at which the multi-band antenna operates, the radio waves are reflected in space to the desired direction without being reflected back to the source of emission.

[0035] In an implementation form of the communication device according to the first aspect, the capacitive and inductive patterns are non-repeating patterns.

[0036] The advantage of this implementation is that the retroreflective structure can reflect waves to the desired direction instead of the conventional periodic stopband structure that only prohibits surface wave propagation. This implementation performs surface wave near-field transformation of radiated waves at short cross-sections, such as less than half the wavelength.

[0037] In an implementation form of the communication device according to the first aspect, the capacitive and inductive patterns form a grid pattern.

[0038] The advantage of this implementation is that it allows several groups of capacitive and inductive elements to be repeated as super cells of longer structures to further improve performance.

[0039] In an implementation form of the communication device according to the first aspect, the radio waves are transverse magnetic polarized radio waves.

[0040] The advantage of this implementation is that it is suitable for antennas that emit transverse magnetic polarized radio waves. Transverse magnetic polarized radio waves have the strongest coupling with parasitic surface waves along the device cover, so converting transverse magnetic polarized radio waves into radiated waves can achieve dual polarization beamforming of the antenna.

[0041] According to a second aspect of the present invention, the above-mentioned objects and other objects are achieved by a method for manufacturing a communication device for a wireless communication system, the method comprising:

[0042] Obtaining the base plate and glass layer;

[0043] obtaining a dielectric layer extending along a plane and comprising a retroreflective structure extending within the dielectric layer, wherein the retroreflective structure is configured to reflect radio waves at an angle that is not parallel to the plane;

[0044] disposing a dielectric layer between the backplane and the glass layer; and

[0045] disposing an antenna element adjacent to the retroreflective structure; and

[0046] The antenna element is conductively or capacitively coupled to the retroreflective structure.

[0047] The method according to the second aspect can be extended to an implementation form corresponding to the implementation form of the communication device according to the first aspect. Therefore, the implementation form of the method comprises the features of the corresponding implementation form of the communication device.

[0048] The advantages of the method according to the second aspect are the same as the advantages of the corresponding implementation form of the communication device according to the first aspect.

[0049] Additional applications and advantages of embodiments of the present invention will become apparent from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The accompanying drawings are intended to illustrate and describe different embodiments of the present invention, in which:

[0051] Figure 1 Schematically shows a communication device according to an embodiment of the present invention,

[0052] Figure 2a to Figure 2b Schematically shows a reverberation structure and an antenna element in a communication device according to an embodiment of the present invention,

[0053] Figure 3a to Figure 3b Schematically shows a reverberation structure and an antenna element in a communication device according to an embodiment of the present invention,

[0054] Figure 4a to Figure 4b The retroreflection concept and the transverse magnetic mode vector and its projection are shown.

[0055] Figure 5 a to Figure 5 c shows a retroreflective structure model according to an embodiment of the present invention,

[0056] Figure 6a to Figure 6b shows the impedance discretization according to an embodiment of the present invention,

[0057] Figures 7a to 7c shows the geometry of the retroreflective structure according to an embodiment of the present invention,

[0058] Figure 8 shows the directionality for a conventional communication device and for a communication device according to the present invention,

[0059] Figure 9a to Figure 9bshows the directivity and gain improvements for a communication device according to the present invention, and

[0060] Fig.10 A method for a communication device according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0061] The layer structure of conventional smartphones generates surface waves excited by the internal antenna, passing through the screen glass and the dielectric layer located below the screen glass. These surface waves strongly distort the radiation pattern of the antenna and reduce the gain of the antenna, and should therefore be avoided.

[0062] Conventional solutions for surface wave suppression can be divided into volumetric implementations and surface implementations. Volumetric solutions achieve wave suppression by changing the bulk electrical properties of the material of the layer. Common volumetric methods for wave suppression are based on Electro-Magnetic Bandgap Structure (EBG), Epsilon-Negative Material (ENG) or Mu-Negative Material (MNG). Surface solutions are based on creating additional interfaces inside the dielectric layer. This change in geometry changes the dispersion characteristics of surface waves that can propagate in the dielectric layer.

[0063] A more practical implementation is obtained using a leaky wave antenna approach, where surface wave propagation is reduced by radiating part of the energy away from the interface.

[0064] The solutions mentioned above only consider the properties of the smartphone body as a combination of different layers, but not the antenna itself. Better results can be obtained by modifying the antenna radiation pattern itself. Solutions proposed in this field include antenna devices consisting of multiple radiating conductors and dummy conductors in a multilayer circuit board and antenna devices consisting of a radiator surrounded by a filter unit located above the substrate.

[0065] Conventional solutions have shown promising results in wave suppression or enhancing antenna radiation characteristics under controlled conditions. Unfortunately, the assumptions chosen for each solution are not compatible with the constraints imposed by the antenna under the glass of a full-display smartphone. Smartphone design prioritizes display over other device characteristics. Therefore, any structure placed behind the glass should have little impact on the display performance. This situation requires compact antennas, which is impossible using conventional solutions for surface wave suppression because they require a large area.

[0066] Additionally, some conventional solutions are implemented using volumetric structures that cannot be placed behind the glass without compromising antenna or display performance. In some implementations, the structure cannot be mounted between the glass and the backplane, requiring a change in the size of the smartphone without any guarantee of performance improvement. It should also be noted that the structural design should be compatible with practical manufacturing methods. However, the manufacture of volumetric structures is challenging and expensive, and in practice only thin sheets of planar material may be used.

[0067] In summary, conventional solutions for surface wave suppression guarantee good performance under ideal conditions. However, compact implementation of these solutions is not possible and therefore they are not suitable for antennas integrated in full-display smartphones.

[0068] The object of the present invention is to solve the above mentioned disadvantages and to improve the performance of an antenna located behind a glass layer in a communication device using a retroreflective structure designed to reflect electromagnetic waves that can excite surface waves. The retroreflective structure is arranged to prevent parasitic penetration of antenna energy into the glass layer and into the surface waves behind the glass layer, and to direct the radiation in the desired direction. The radiation pattern and gain of the antenna in the communication device are thereby improved.

[0069] Figure 1 The communication device 100 for a wireless communication system according to an embodiment of the present invention is schematically shown. The communication device 100 includes a substrate 102, a glass layer 104, and a dielectric layer 106. Figure 1 , the dielectric layer 106 extends along a plane P between the base plate 102 and the glass layer 104. The dielectric layer 106 may also be referred to as a dielectric display portion or a dielectric spacer portion.

[0070] The communication device 100 further includes an antenna element 108 and a retroreflective structure 110. The antenna element 108 is configured to transmit radio waves 120. In an embodiment, the radio waves 120 may be transverse magnetic polarized radio waves.

[0071] Reference Figure 1 , the reverberation structure 110 extends inside the dielectric layer 106 and is located near the antenna element 108. In an embodiment, the reverberation structure 110 can be conductively or capacitively coupled to the antenna element 108. For example, a first end of the reverberation structure 110 can be conductively or capacitively coupled to the antenna element 108.

[0072] The retroreflective structure 110 is configured to reflect the radio waves 120 emitted by the antenna element 108 at an angle that is not parallel to the plane P. The reflection angle of the retroreflective structure 110 is the same as or substantially the same as the incident angle. Therefore, the angle that the retroreflective structure 110 reflects the radio waves 120 that is not parallel to the plane P is the same as the angle at which the radio waves 120 are incident toward the retroreflective structure 110. The retroreflective structure 110 therefore serves as an effective boundary that reflects the radio waves 120 from the antenna element 108 back to the antenna element 108.

[0073] The reflection phase of the reflected radio waves can be designed by adjusting the topology of the retroreflective structure 110. According to an embodiment of the present invention, the retroreflective structure 110 has a non-uniform impedance along its extension in the dielectric layer 106. In this way, the desired phase synchronization between the incident surface wave and the reflected radiation wave can be ensured. Figure 4a-4b as well as Figure 7a-7c Additional details related to the topology of retroreflective structure 110 are described.

[0074] By utilizing the near field region close to the antenna element 108, the retroreflective structure 110 can be used as a beam forming surface for the antenna element 108. The near field region can be defined as up to half the wavelength of the radio wave. Therefore, in an embodiment, the retroreflective structure 110 can be located within a range r from the antenna element 108 that is less than half the wavelength of the radio wave 120. In addition, the retroreflective structure 110 can have an extension less than half the wavelength of the radio wave 120 inside the dielectric layer 106.

[0075] According to an embodiment of the present invention, the retroreflective structure 110 is a conductive film 112. Therefore, the retroreflective structure 110 can be a thin and flat structure extending inside the dielectric layer 106, wherein the main extension is along the plane P. The conductive film 112 can include a solid conductive film, or the conductive film 112 can include capacitive elements and inductive elements forming capacitive and inductive patterns.

[0076] In an embodiment where the conductive film 112 includes capacitive elements and inductive elements, the size of each capacitive element and each inductive element can be less than one quarter of the wavelength of the radio wave 120. The capacitive elements and the inductive elements can thus form sub-wavelength spaced capacitive and inductive patterns. The capacitive and inductive patterns can also be non-repeating patterns, for example, non-periodic patterns. In this way, resonances due to periodicity can be avoided. In addition, the capacitive and inductive patterns can form a grid pattern. The capacitive and inductive patterns can be designed as a set of gripping impedance strips, for example using discrete values ​​of the reflector grid impedance function, as will be further described below.

[0077] The antenna element 108 may be arranged perpendicular to or parallel to the plane P of the dielectric layer 106 or in other suitable directions. Figure 2a to Figure 2b Schematically shows an embodiment in which the antenna element 108 is arranged perpendicular to the plane P of the dielectric layer 106. Figure 2a to Figure 2b In the embodiment shown, the antenna element 108 is a monopole antenna and the backreflection structure 110 is a conductive film 112 including capacitive elements 114a, 114b, ..., 114n and inductive elements 116a, 116b, ..., 116n forming capacitive and inductive patterns. There are metallic elements of the antenna structure that shield the volume between the conductive film 112 and the bottom plate / ground plane 102, thereby preventing the excitation of waves guided between the conductive film 112 and the bottom plate / ground plane 102. As an example, this can be ensured by conductively coupling the antenna element 108 at the first end 110a of the backreflection structure 110, such as Figure 2b shown.

[0078] Figure 3a to Figure 3b Schematically shows an embodiment in which the antenna element 108 is arranged parallel to the plane P of the dielectric layer 106. Figure 3a to Figure 3b In the illustrated embodiment, the antenna element 108 is a monopole antenna and the retroreflective structure 110 is a solid conductive film 112. The retroreflective structure 110 is further conductively coupled to the antenna element 108. There is a metallic element of the antenna structure that shields the volume between the conductive film 112 and the backplane / ground plane 102, thereby preventing the excitation of waves guided between the conductive film 112 and the backplane / ground plane 102. As an example, this can be ensured by conductively coupling the antenna element 108 at the first end 110a of the retroreflective structure 110, as shown in FIG. Figure 3b shown.

[0079] The embodiments described above are two examples of possible combinations of antenna element arrangements and types of reverberation structures 110. However, other combinations are possible without departing from the scope of the present invention. For example, antenna element 108 may be arranged perpendicular to plane P of dielectric layer 106, and reverberation structure 110 may be a solid conductive film; or antenna element 108 may be arranged parallel to plane P of dielectric layer 106, and reverberation structure 110 may be a conductive film 112 forming a capacitive and inductive pattern.

[0080] The retroreflective structure 110 enables waves incident from space to be redirected back to the source of the incident waves, such as Figure 4a As indicated.

[0081] According to an embodiment of the present invention, the retroreflective structure 110 may be implemented as a metasurface, wherein the desired phase synchronization between the incident wave and the reflected wave may be adjusted by designing the surface impedance defined by the following boundary conditions:

[0082]

[0083] Among them, E t and H t is the total, i.e. incident plus reflected, electric and magnetic field tangential components, and is a unit vector perpendicular to the surface. Therefore, the tangential components of both the electric and magnetic fields must be defined to provide the desired retroreflective effect.

[0084] Due to the desired field polarization, the retroreflective structure 110 can be designed for transverse-magnetic (TM) polarized waves where the normal component of the magnetic field is absent. Figure 4b Using the coordinate definition shown in , the tangential components of the incident and reflected magnetic fields can be written as:

[0085]

[0086] in, is the reflection coefficient ( is the phase of the reflection coefficient), and θ i is the angle of incidence. To find the electric field component of the TM wave, the time harmonic correlation of the field e is used. jωt Ampere's law:

[0087]

[0088] where ε0 is the dielectric constant of the background medium assumed to be a vacuum. Therefore, the tangential electric field is simplified to:

[0089]

[0090] Using equation (1) and knowing that the tangential component of the total magnetic field and the tangential component of the total electric field are both the sum of the reflected field and the incident field (respectively and ), the surface impedance of the modeled retroreflective structure 110 is read as:

[0091]

[0092] in, is the phase gradient introduced by the metasurface. The phase gradient required for the retroreflective structure 110 produces a frequency-dependent surface impedance. Based on the definition of the phase gradient, the period of the retroreflective structure 110 is calculated as

[0093] As the angle of incidence decreases, the period increases, and in the limit of zero angle, i.e., at normal incidence, the retroreflective structure 110 degenerates into a generally uniform reflector. In either case, the compact retroreflective structure 110 will react to the field near the antenna and therefore only requires one period of surface impedance.

[0094] In the communication device 100, it is more convenient to use the glass surface as a reference to create the impedance of the retroreflective structure 110, such as Figure 5 a to Figure 5 c. The retroreflective structure 110 located inside the dielectric layer 106 can be modeled as a grid impedance Z g , which will introduce discontinuity of the tangential magnetic field at its two sides.

[0095] The electromagnetic field is at an angle θ relative to the surface of the retroreflective structure 110. i propagates toward the retroreflective structure 110 (see Figure 5 a). With normal Component and tangent The incident electromagnetic field coefficient of the component The multilayer retroreflective structure 110 has a glass cover layer d3 with a thickness, a dielectric layer d2 between the glass cover layer and the conductive pattern 112 layer, and a grid impedance Z of the conductive pattern 112. g and a dielectric layer d1 between the conductive pattern 112 and the ground plane. The impedances Z1, Z2, Z3 of the dielectric layer and the grid impedance Z g ( Figure 5 b) can be converted to the surface impedance Z that models the retroreflective structure 110 s ( Figure 5 c).

[0096] In order to ensure that the multilayer structure acts as a retroreflector on the glass surface, it is necessary to simulate the behavior of the surface impedance defined in equation (6). Using the transmission line method, e.g. Figure 5 b, the input impedance of the multilayer system can be calculated and equated to the desired value. The resulting expression for the desired mesh impedance—as a function of the surface impedance and other parameters of the multilayer system—can be written as:

[0097]

[0098] in, as well as where n∈[1,2,3] numbers the dielectric layers.

[0099] Figure 6aThe discretization of the grid impedance distribution and the surface impedance distribution is shown. It is worth noting that both the grid impedance and the surface impedance are continuous functions along the surface in the x-direction. Because the retroreflective structure 110 is implemented as a set of elements of finite size, this problem may become troublesome in terms of surface implementation. Therefore, as Figure 6b As schematically shown in , the retroreflective structure 110 is discretized into strips with constant grid impedance values, thereby replacing the continuous function with a stepwise constant approximation. Selecting an appropriate number of discrete values ​​can achieve a good compromise between performance and complexity.

[0100] Figures 7a to 7c A retroreflective structure 110 is shown according to an embodiment, wherein the retroreflective structure 110 has been discretized into six elements. These elements can be manufactured, for example, based on a meandering groove topology. Figure 7a An element of a meander slot based retroreflective structure 110 is shown. Each element comprises two metal patches 116a, 116b separated by a gap or slot 114a between them. The grid impedance Z can be adjusted by varying the length A and width w of the slot gap g . Figure 7b A cross section of retroreflective structure 110 along the y-axis is shown, wherein the cross section has been designed to achieve the desired retroreflective functionality.

[0101] Figure 7c The location of retroreflective structure 110 within dielectric layer 106 is shown. Retroreflective structure 110 is located in the middle of dielectric layer 106 below glass layer 104 in this embodiment.

[0102] Table 1 shows the incident angle θ i The optimum value for retroreflective structure 110 with angle = 85° considers glass with a thickness of 0.5 mm and a relative dielectric constant of 5.5, and wherein dielectric layer 106 is characterized as a 1.0 mm plate with a relative dielectric constant of 2.7.

[0103] # 1 2 3 4 5 6 <![CDATA[Im(Z g )]]> -47 -254 -68 -62 -58 -55 <![CDATA[Im(Z s )]]> 60 -1255 -54 -18 0.86 20 A, mm 0.34 0.26 0.34 0.32 0.34 33 w,mm 0.06 0.065 0.065 0.055 0.063 0.058

[0104] Table 1

[0105] for Figure 7c For the embodiment shown in , the required optimum impedance values ​​given in Table 1 indicate that none of the discrete strips need to operate close to resonance, even though the retroreflective structure 110 uses only capacitive mesh elements. Therefore, the retroreflective structure 110 can operate in a wider frequency band than other conventional structures, which can only operate in a resonant state within a narrow frequency range.

[0106] In terms of size, the proposed retroreflective structure 110 is a suitable compact solution because its length is reduced to a single-phase period of Equation 6. For the case discussed above, the length of the retroreflective structure 110 is about 5.2 mm, which is less than half a wavelength at a reference frequency of 29 GHz, and each element occupies 1 / 6 of the total length. If more discrete points are used and appropriate manufacturing methods are utilized, the length of the elements can be reduced even more.

[0107] By using the retroreflective structure 110 according to the present invention, not only can the propagation of the surface wave inside the dielectric layer 106 be blocked, but the energy can also be further redirected to a desired direction, such as Figure 8 shown. Figure 8 Directivities at 29 GHz are shown for two cases: the first case 802 shows the directivity of a communication device without any surface wave suppression structure, and the second case 804 shows the directivity of the same communication device with an additional retroreflective structure 110 according to the present invention in the middle of the dielectric layer 106. Note that the surface waves propagating under the glass in a 90° direction are suppressed by the retroreflective structure 110 and redirected to the region of interest at the top of the glass, i.e., in the 0° direction.

[0108] For different frequencies, the retroreflective structure 110 shows consistent improvements, as shown in FIG. Figure 9a to Figure 9b It can be seen. Figure 9a shows the improvement in directionality of the retroreflective structure 110, and Figure 9b The gain improvement is shown for the retroreflective structure 110. The retroreflective structure 110 may provide an average directivity improvement of about 3 dB and an average gain improvement of about 5 dB.

[0109] The invention also relates to a method for manufacturing a communication device 100 according to any of the described embodiments. Fig.10 A flow chart of a method 200 is shown, the method 200 comprising obtaining 202 a backplane 102 and a glass layer 104, and further obtaining 204 a dielectric layer 106, the dielectric layer 106 extending along a plane P and comprising a retroreflective structure 110 extending inside the dielectric layer 106, wherein the retroreflective structure 110 is configured to reflect radio waves 120 at an angle that is not parallel to the plane P. The method 200 also comprises arranging 206 the dielectric layer 106 between the backplane 102 and the glass layer 104; and arranging 208 an antenna element 108 adjacent to the retroreflective structure 110. The method 200 also comprises conductively or capacitively coupling 210 the antenna element 108 to the retroreflective structure 110.

[0110] The communication device 100 herein may be represented as a user device, a user equipment (UE), a mobile station, an Internet of Things (IoT) device, a sensor device, a wireless terminal and / or a mobile terminal, and may be enabled to communicate wirelessly in a wireless communication system, sometimes also referred to as a cellular radio system. UE may also be referred to as a mobile phone, a cellular phone, a tablet computer or a laptop computer with wireless capabilities. The UE in this context may be, for example, a portable mobile device, a pocket mobile device, a handheld mobile device, a mobile device including a computer, or a vehicle-mounted mobile device, which is enabled to communicate voice and / or data with another entity, such as another receiver or a server, via a radio access network. The UE may be a station (STA), which is any device including a media access control (MAC) and a physical layer (PHY) interface in accordance with IEEE 802.11 with a wireless medium (WM). The UE may also be configured to communicate in 3GPP-related LTE and LTE-Advanced, in WiMAX and its evolution, and in fifth-generation wireless technologies such as New Radio.

[0111] Finally, it should be understood that the present invention is not limited to the embodiments described above, but also relates to and incorporates all embodiments within the scope of the appended independent claims.

Claims

1. A communication device (100) for a wireless communication system (500), the communication device (100) comprising: Bottom plate (102); Glass layer (104); a dielectric layer (106) extending along a plane (P) between the base plate (102) and the glass layer (104); an antenna element (108) configured to transmit radio waves (120); as well as A retroreflective structure (110) extending inside the dielectric layer (106) and located near the antenna element (108), wherein the retroreflective structure (110) is configured to reflect the radio waves (120) at an angle that is not parallel to the plane (P), wherein the retroreflective structure (110) is a conductive film (112), and the conductive film (112) includes capacitive elements (114a, 114b, ..., 114n) forming a capacitive pattern and inductive elements (116a, 116b, ..., 116n) forming an inductive pattern.

2. The communication device (100) according to claim 1, wherein: The retroreflective structure (110) has a non-uniform impedance along its extension in the dielectric layer (106).

3. The communication device (100) according to claim 1, wherein: The retroreflective structure (110) is conductively or capacitively coupled to the antenna element (108).

4. The communication device (100) according to claim 3, wherein: The first end of the retroreflective structure (110) is conductively or capacitively coupled to the antenna element (108).

5. The communication device (100) according to any one of claims 1 to 4, wherein: The retroreflective structure (110) is located within a range of less than half a wavelength of the radio wave (120) from the antenna element (108).

6. The communication device (100) according to any one of claims 1 to 4, wherein: The antenna element (108) is arranged perpendicularly or parallel to a plane (P) of the dielectric layer (106).

7. The communication device (100) according to any one of claims 1 to 4, wherein: The retroreflective structure (110) has an extension inside the dielectric layer (106) that is less than half the wavelength of the radio wave (120).

8. The communication device (100) according to claim 1, wherein: The size of each capacitive element and each inductive element is smaller than a quarter of the wavelength of the radio wave (120).

9. The communication device (100) according to claim 1 or 8, wherein: The capacitive and inductive patterns are non-repeating patterns.

10. The communication device (100) according to claim 1 or 8, wherein: The capacitive and inductive patterns form a grid pattern.

11. The communication device (100) according to any one of claims 1 to 4 and 8, wherein: The radio waves (120) are transverse magnetic polarized radio waves.

12. A method (200) for manufacturing a communication device (100) for a wireless communication system (500), the method (200) comprising: Obtaining (202) a base plate (102) and a glass layer (104); Obtaining (204) a dielectric layer (106), the dielectric layer (106) extending along a plane (P) and comprising a retroreflective structure (110) extending inside the dielectric layer (106), wherein the retroreflective structure (110) is configured to reflect radio waves (120) at an angle that is not parallel to the plane (P); disposing (206) the dielectric layer (106) between the base plate (102) and the glass layer (104); and disposing (208) an antenna element (108) adjacent to the retroreflective structure (110); and conductively or capacitively coupling the antenna element (108) to the retroreflective structure (110), The retroreflective structure (110) is a conductive film (112), and the conductive film (112) includes capacitive elements (114a, 114b, ..., 114n) forming a capacitive pattern and inductive elements (116a, 116b, ..., 116n) forming an inductive pattern.

Images