Liquid crystal antenna unit and liquid crystal phased array antenna

Abstract

A liquid crystal antenna unit includes: a first substrate; a second substrate disposed opposite to the first substrate; a liquid crystal layer disposed between the first substrate and the second substrate; a transmission line located on a first surface and arranged to extend in a first direction along the first surface; a first antenna element located on the first surface and arranged as an elongated dipole extending in a second direction along the first surface; a second antenna element located on a surface of the second substrate facing away from the first substrate at a position corresponding to the first antenna element; and a ground electrode located on a surface of the first substrate facing away from the second substrate. A liquid crystal phased array antenna includes a plurality of the liquid crystal antenna units arranged in an array.

Description

Technical Field

[0001] The present invention relates to the field of antenna technology, and in particular to a liquid crystal antenna unit and a liquid crystal phased array antenna. Background Art

[0002] With the development of communication technology, services such as "Satcom on the move" are being widely used. This requires antennas with desired performance. Compared with mechanical scanning-based antennas, phased array antennas have advantages such as high tracking accuracy and short response time due to the elimination of mechanical control mechanisms. Phased array antennas based on liquid crystal materials also have additional advantages such as small size, low power consumption and easy integration with control circuit systems, and are therefore considered to be a promising solution. Summary of the invention

[0003] According to one aspect of the present invention, there is provided a liquid crystal antenna unit, comprising: a first substrate; a second substrate disposed opposite to the first substrate; a liquid crystal layer disposed between the first substrate and the second substrate; a transmission line located on a first surface and arranged to extend in a first direction along the first surface, the first surface being selected from a group consisting of a surface of the first substrate facing the second substrate and a surface of the second substrate facing the first substrate; a first antenna element located on the first surface and arranged as an elongated dipole extending in a second direction along the first surface, the dipole comprising two poles separated by a gap, the first antenna element being configured to couple between the two poles and the transmission line at the gap. Combined electromagnetic waves; a second antenna element, located at a position corresponding to the first antenna element on a surface of the second substrate facing away from the first substrate, the second antenna element having an elongated shape extending in the second direction along the surface of the second substrate facing away from the first substrate, the second antenna element also having a length less than the length of the first antenna element; and a grounding electrode, located on a surface of the first substrate facing away from the second substrate, the grounding electrode including an elongated electrode portion located at a position corresponding to the first antenna element, the elongated electrode portion extending in the second direction along the surface of the first substrate facing away from the second substrate, the elongated electrode portion having a length greater than the length of the first antenna element.

[0004] In some embodiments, the length of the second antenna element is 0.7-0.9 times the length of the first antenna element.

[0005] In some embodiments, the first substrate and the second substrate are made of the same material, and the second substrate has a thickness that is 3-5 times that of the first substrate.

[0006] In some embodiments, the first substrate and the second substrate are made of different materials, and the thickness of the first substrate and the thickness of the second substrate satisfy the following relationship:

[0007] ,

[0008] Wherein H1 is the thickness of the first substrate, H2 is the thickness of the second substrate, is the dielectric constant of the first substrate, and is the dielectric constant of the second substrate.

[0009] In some embodiments, the second substrate is a composite board including multiple layers of materials.

[0010] In some embodiments, the second antenna element, the first antenna element and the elongated electrode portion are arranged so that a center of the second antenna element, a center of the gap in the first antenna element and a center of the elongated electrode portion coincide in a direction perpendicular to the first substrate and the second substrate.

[0011] In some embodiments, the first direction is perpendicular to the second direction.

[0012] In some embodiments, the transmission line comprises a coplanar waveguide transmission line, which comprises a signal line and two ground lines respectively located on both sides of the signal line.

[0013] In some embodiments, one end of the signal line is electrically connected to one of the poles of the dipole at the gap in the first antenna element, and one end of one of the two ground lines is electrically connected to the other of the poles of the dipole at the gap.

[0014] In some embodiments, the first surface is a surface of the first substrate facing the second substrate, and the liquid crystal antenna unit further includes an electrode structure on the second surface, and the second surface is a surface of the second substrate facing the first substrate.

[0015] In some embodiments, the first surface is a surface of the second substrate facing the first substrate, and the liquid crystal antenna unit further includes an electrode structure on a second surface, and the second surface is a surface of the first substrate facing the second substrate.

[0016] In some embodiments, the electrode structure includes a plurality of electrodes that are parallel to each other and extend along the second surface in a direction perpendicular to the first direction.

[0017] In some embodiments, the ground electrode further comprises an additional electrode portion extending from the elongated electrode portion in a direction perpendicular to the second direction along the surface of the first substrate facing away from the second substrate.

[0018] According to another aspect of the present invention, there is provided a liquid crystal phased array antenna, comprising a plurality of liquid crystal antenna units as described above arranged in an array.

[0019] In some embodiments, each first substrate of the plurality of liquid crystal antenna units is formed as a whole from a single substrate, and each second substrate of the plurality of liquid crystal antenna units is formed as a whole from another single substrate.

[0020] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Further details, features and advantages of the invention are disclosed in the following description of exemplary embodiments in conjunction with the accompanying drawings, in which:

[0022] Figure 1 schematically illustrates a top view of a liquid crystal antenna unit according to an embodiment of the present invention;

[0023] Figure 2A Schematically illustrates the Figure 1 The AA' line in Figure 1 A cross-sectional view of a liquid crystal antenna unit;

[0024] Figure 2B Schematically illustrates the Figure 1 The BB' line in Figure 1 A cross-sectional view of a liquid crystal antenna unit;

[0025] Figure 3 Schematically illustrates Figure 1 Arrangement of the first antenna element and the transmission line in the liquid crystal antenna unit;

[0026] Figure 4 Schematically illustrates Figure 1 A bottom view of a liquid crystal antenna unit;

[0027] Figure 5 Shows Figure 1 Two-dimensional far-field directivity pattern of the liquid crystal antenna unit;

[0028] Fig. 6A and 6B schematically illustrates a cross-sectional view of a liquid crystal antenna unit according to another embodiment of the present invention; and

[0029] Figure 7 The block diagram of a liquid crystal phased array antenna according to an embodiment of the present invention is schematically illustrated. DETAILED DESCRIPTION

[0030] It will be understood that, although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and / or parts in this article, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish an element, component, region, layer or part from another region, layer or part. Therefore, the first element, component, region, layer or part discussed below may be referred to as a second element, component, region, layer or part without departing from the teaching of the present invention.

[0031] Spatially relative terms such as "below", "below", "below", "above", "above", etc. may be used herein for ease of description to describe the relationship between an element or feature and another element or feature as illustrated in the figure. It will be understood that these spatially relative terms are intended to cover different orientations of the device in use or operation in addition to the orientation depicted in the figure. For example, if the device in the figure is flipped, the element described as "below other elements or features" or "below other elements or features" or "below other elements or features" will be oriented to "above other elements or features". Therefore, the exemplary terms "below" and "below" can cover both orientations above and below. Terms such as "before" or "before" and "after" or "followed by" can be similarly used, for example, to indicate the order in which light passes through the elements. The device can be oriented in other ways (rotated 90 degrees or in other orientations) and the spatially relative descriptors used in this article are interpreted accordingly. In addition, it will also be understood that when a layer is referred to as being “between two layers,” it can be the only layer between the two layers, or one or more intervening layers may also be present.

[0032] The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used herein, the singular forms "one", "one" and "the" are intended to also include plural forms, unless the context clearly indicates otherwise. It will be further understood that the terms "include" and / or "comprise" specify the existence of the features, integral bodies, steps, operations, elements and / or parts when used in this specification, but do not exclude the existence of one or more other features, integral bodies, steps, operations, elements, parts and / or their groups or add one or more other features, integral bodies, steps, operations, elements, parts and / or their groups. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0033] It will be understood that when an element or layer is referred to as being "on another element or layer," "connected to another element or layer," "coupled to another element or layer," or "adjacent to another element or layer," it may be directly on another element or layer, directly connected to another element or layer, directly coupled to another element or layer, or directly adjacent to another element or layer, or there may be intermediate elements or layers. Conversely, when an element is referred to as being "directly on another element or layer," "directly connected to another element or layer," "directly coupled to another element or layer," or "directly adjacent to another element or layer," there are no intermediate elements or layers. However, in no case should "on..." or "directly on..." be interpreted as requiring that one layer completely cover the layer below.

[0034] Embodiments of the invention are described herein with reference to schematic illustrations of idealized embodiments of the invention (and intermediate structures). As such, variations in the illustrated shapes, for example as a result of manufacturing techniques and / or tolerances, should be expected. Therefore, embodiments of the invention should not be construed as limited to the specific shapes of the regions illustrated herein, but should include deviations in shapes, for example, due to manufacturing. Therefore, the regions illustrated in the figures are schematic in nature, and their shapes are not intended to illustrate the actual shapes of the regions of the device and are not intended to limit the scope of the invention.

[0035] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. It will be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the relevant art and / or the context of this specification, and will not be interpreted in an idealized or overly formal sense unless explicitly defined as such herein.

[0036] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0037] Figure 1 A top view of a liquid crystal antenna unit 100 according to an embodiment of the present invention is schematically illustrated.

[0038] like Figure 1 As shown, the liquid crystal antenna unit 100 includes a second substrate 120 and a second antenna element 122. The second substrate 120 is made of, for example, glass. The second antenna element 122 is located on the upper surface of the second substrate 120 and has an elongated shape extending in a second direction D2 along the upper surface of the second substrate 120.

[0039] Figure 1Also shown in the figure are a transmission line 112, a first antenna element 118, and an electrode structure 124 indicated by dashed lines. Dashed lines are used because these elements are not formed on the upper surface of the second substrate 120. The transmission line 112 is arranged to extend in a first direction D1 (the first direction D1 is perpendicular to the second direction D2 in this embodiment, although this is not necessary; the first direction D1 can be at any angle to the second direction D2 in some embodiments). Specifically, the transmission line 112 is a coplanar waveguide (CPW) transmission line, which includes a signal line 113 and two ground lines 115 and 117 located on both sides of the signal line 113. The electrode structure 124 includes a plurality of electrodes 125 that are parallel to each other and extend in a direction perpendicular to the first direction D1 (in this example, the second direction D2).

[0040] It will be understood that Figure 1 The transmission line 112 shown in is exemplary, and any other suitable type of transmission line may be used in other embodiments, such as grounded coplanar waveguide (CPWG) and ordinary microstrip line. It will also be understood that Figure 1 The electrode structure 124 shown in FIG. 1 is exemplary, and in other embodiments the electrode structure 124 may have any other suitable pattern.

[0041] Figure 2A and 2B The diagrams are schematically shown along Figure 1 The AA' and BB' lines in Figure 1 The structure of the liquid crystal antenna unit 100 is shown in FIG. Figure 2A and 2B is shown more clearly in.

[0042] refer to Figure 2A , the liquid crystal antenna unit 100 includes, among other things, a first substrate 110 disposed opposite to a second substrate 120 and a liquid crystal layer 130 disposed between the first substrate 110 and the second substrate 120. The first substrate 110 is made of, for example, glass. The liquid crystal layer 130 contains liquid crystal molecules (not shown) and has a typical thickness of less than 100 μm. A transmission line 112 including a signal line 113 and ground lines 115, 117 is located on a first surface S1 and is arranged to extend in a first direction D1 along the first surface S1. In this embodiment, the first surface S1 is a surface of the first substrate 110 facing the second substrate 120, and the surface of the second substrate 120 facing the first substrate 110 is correspondingly referred to as a second surface S2. The respective electrodes 125 of the electrode structure 124 are located on the second surface S2 and extend in a direction perpendicular to the first direction D1 (in this example, the second direction D2) along the second surface S2.

[0043] The liquid crystal molecules in the liquid crystal layer 130 are anisotropic and exhibit different dielectric constants in the long axis direction and the short axis direction. When in operation, the transmission line 112 is used to transmit electromagnetic wave signals to / from a receiver / transmitter (not shown), and each electrode 125 of the electrode structure 124 is applied with a modulation voltage to establish a bias electric field between the electrode 125 and the ground lines 115, 117. Due to the bias electric field between the electrode 125 and the ground lines 115, 117, the liquid crystal molecules are deflected so that the dielectric constant of the liquid crystal layer 130 changes with the deflection of the liquid crystal molecules. When the electromagnetic wave signal is transmitted along the transmission line 112 in the liquid crystal layer 130 with the changed dielectric constant, the electromagnetic wave signal is phase-shifted to a certain extent. Therefore, the phase shift of the electromagnetic wave signal can be achieved by controlling the deflection of the liquid crystal molecules in the liquid crystal layer 130, and the deflection can be achieved by controlling the modulation voltage applied to the electrode structure 124. This is a known technology called a liquid crystal phase shifter. For this purpose, the liquid crystal antenna unit 100 further includes a first alignment layer 132 disposed on the first surface S1 and a second alignment layer 134 disposed on the second surface S2, such as Figure 2A The first alignment layer 132 and the second alignment layer 134, for example, made of polyimide, are used to set the initial orientation of the liquid crystal molecules in the liquid crystal layer 130 without a bias electric field. The first alignment layer 132 and the second alignment layer 134 have such a thickness that they have substantially no effect on the electromagnetic wave signal in the transmission line 112.

[0044] It will be appreciated that the electrode structure 124 (and hence the electrode 125) provided for the purpose of modulating the dielectric constant of the liquid crystal layer 130 may even be optional in some embodiments, since the required bias electric field may be established using only the transmission line 112. For example, a modulation voltage may be applied to the signal line 113 of the transmission line 112, establishing the required bias electric field between the signal line 113 and the ground lines 115, 117 of the transmission line 112.

[0045] refer to Figure 2B , the liquid crystal antenna unit 100 includes, among other things, a first antenna element 118. The first antenna element 118 is located on the first surface S1 and is arranged as an elongated dipole extending in the second direction D2 along the first surface S1. As shown, the dipole includes two poles 118A and 118B separated by a gap 119. The first antenna element 118 is configured to couple electromagnetic waves between the two poles 118A, 118B and the transmission line 112 at the gap 119.

[0046] Figure 3 An exemplary arrangement of the first antenna element 118 and the transmission line 112 is schematically illustrated.

[0047] refer to Figure 3 , the transmission line 112 extends in a first direction D1, and the dipoles 118A, 118B of the first antenna element 118 extend in a second direction D2. One end of the signal line 113 of the transmission line 112 is electrically connected to one of the poles 118A, 118B of the dipole (in this example, the pole 118A) at a gap 119 in the first antenna element 118, and one end of one of the two ground lines 115, 117 of the transmission line 112 (in this example, the ground line 117) is electrically connected to the other of the poles 118A, 118B of the dipole (in this example, the pole 118B) at the gap 119. In a transmission scenario, the transmission line 112 feeds the electromagnetic wave signal from a transmitter (not shown) to the first antenna element 118. Alternatively, in a receiving scenario, the first antenna element 118 feeds the received electromagnetic wave signal to the transmission line 112 , and the electromagnetic wave signal is further provided to a receiver (not shown) through the transmission line 112 .

[0048] It will be understood that although in this embodiment the first antenna element 118 and the transmission line 112 are shown as being perpendicular to each other, in other embodiments the first antenna element 118 and the transmission line 112 may be at any suitable angle (e.g., parallel to each other), and although in this embodiment the first antenna element 118 and the transmission line 112 are shown as being directly electrically connected to each other, other embodiments are possible. For example, the transmission line 112 may be electromagnetically coupled to the first antenna element 118 through any suitable intermediate medium.

[0049] It will also be understood that Figure 3 The pattern of the first antenna element 118 (more specifically, the dipoles 118A, 118B) shown in is exemplary, and in other embodiments the first antenna element 118 may be a dipole having other patterns, such as a folded dipole formed by an elongated conductor. Folded dipoles are known per se, and such folded dipoles formed by an elongated conductor are still referred to herein as “elongated” dipoles.

[0050] Figure 4 A bottom view of the liquid crystal antenna unit 100 is schematically illustrated.

[0051] refer to Figure 4, the liquid crystal antenna unit 100 includes, among other things, a ground electrode 114. The ground electrode 114 includes an elongated electrode portion 114A extending in a second direction D2 along a surface of the first substrate 110 facing away from the second substrate 120. The elongated electrode portion 114A has a length L3. In this example, the ground electrode 114 also includes an additional electrode portion 114B extending from the elongated electrode portion 114A in a direction perpendicular to the second direction D2 (in this example, the first direction D1) along the surface of the first substrate 110 facing away from the second substrate 120.

[0052] It will be understood that Figure 4 The ground electrode 114 shown in FIG. 1 is exemplary, and in some embodiments the ground electrode 114 may cover the entire surface of the first substrate 110 facing away from the second substrate 120. However, the attachment electrode portion 114B may be optional in some embodiments.

[0053] Return to reference Figure 2B , the second antenna element 122 has an elongated shape extending in the second direction D2 along the surface of the second substrate 120 facing away from the first substrate 110. The second antenna element 122 has a length L2 that is less than the length L1 of the first antenna element 118, and the length L1 of the first antenna element 118 is less than the length L3 of the elongated electrode portion 114A. Figure 2B The second antenna element 122 is located at a position corresponding to the first antenna element 118 on a surface of the second substrate 120 facing away from the first substrate 110, and the elongated electrode portion 114A is located at a position corresponding to the first antenna element 118 on a surface of the first substrate 110 facing away from the second substrate 120.

[0054] The term "corresponding to" as used herein in connection with the second antenna element 122, the first antenna element 118, and the elongated electrode portion 114A means that the second antenna element 122, the first antenna element 118, and the elongated electrode portion 114A are positioned relative to each other so that they form a three-unit directional radiator, wherein the second antenna element 122 acts as a director, the first antenna element 118 acts as an active element, and the elongated electrode portion 114A acts as a reflector. Specifically, the reflector is positioned on one side of the active element to weaken the electromagnetic waves coming from this side or emitted to this side, and the director is positioned on the other side of the active element to enhance the electromagnetic waves coming from this side or emitted to this direction. Such a directional radiator operates in a manner similar to a Yagi antenna, and a detailed description thereof is therefore omitted here.

[0055] exist Figure 2BIn the example of FIG. 1 , first antenna element 118 is positioned directly above elongated electrode portion 114A, and second antenna element 122 is positioned directly above first antenna element 118. More specifically, second antenna element 122, first antenna element 118, and elongated electrode portion 114A are arranged so that the center of second antenna element 122, the center of gap 119 in first antenna element 118, and the center of elongated electrode portion 114A coincide in a direction perpendicular to first substrate 110 and second substrate 120, as indicated by dashed line OO'.

[0056] Depending on the wavelength of the electromagnetic wave, the second antenna element 122, the first antenna element 118 and the elongated electrode portion 114A are appropriately arranged. For example, the first antenna element 118 has a suitable length, such as half the wavelength of the electromagnetic wave. In some embodiments, the length L2 of the second antenna element 122 is 0.7-0.9 times the length L1 of the first antenna element 118. In an embodiment in which the first substrate 110 and the second substrate 120 are made of the same material, the second substrate 120 has a thickness H2 that is 3-5 times the thickness H1 of the first substrate 110. In an embodiment in which the first substrate 110 and the second substrate 120 are made of different materials, the thickness H1 of the first substrate 110 and the thickness H2 of the second substrate 120 satisfy the following relationship:

[0057] ,

[0058] in is the dielectric constant of the first substrate 110, and is the dielectric constant of the second substrate 120 .

[0059] In some embodiments, the second substrate 120 may be a composite plate including multiple layers of materials to provide a suitable dielectric constant. For example, the outermost layer of the second substrate 120 may even be formed of air. That is, the second antenna oscillator 122 is not directly on the surface of the second substrate 120 facing away from the first substrate 110, but is positioned at a certain distance above the second substrate 120. In this case, the second antenna oscillator 122 may be fixed by means of any appropriate supporting means (e.g., a column).

[0060] It will be understood that, although in the above Figure 1 and 2BAn example arrangement of the second antenna element 122, the first antenna element 118, and the elongated electrode portion 114A is described, but other embodiments are possible. For example, the first antenna element 118 may be offset by a distance in the first direction D1 relative to the elongated electrode portion 114A, and the second antenna element 122 may be further offset by a distance in the first direction D1 relative to the first antenna element 118. Alternatively or additionally, the first antenna element 118 may be offset by a distance in the second direction D2 relative to the elongated electrode portion 114A, and / or the second antenna element 122 may be offset by a distance in the second direction D2 relative to the first antenna element 118. In practice, the second antenna element 122, the first antenna element 118, and the elongated electrode portion 114A may be arranged in any suitable manner as long as they can form a three-unit directional radiator.

[0061] By virtue of the directional radiator formed by the second antenna element 122, the first antenna element 118 and the elongated electrode portion 114A, the liquid crystal antenna unit 100 is expected to achieve a higher amplitude gain.

[0062] Figure 5 The two-dimensional far-field directivity diagram of the liquid crystal antenna unit 100 is shown. The directivity diagram is obtained from a simulation implemented by software, in which the frequency of the electromagnetic wave is set to 30 GHz. According to the simulation results, in the main lobe direction of 0 degrees, the main lobe amplitude gain is 8.89 dBi. This is 2-3 dB higher than the gain of a conventional patch antenna. Therefore, the liquid crystal antenna unit 100 advantageously achieves an increase in gain.

[0063] Fig. 6A and 6B A cross-sectional view of a liquid crystal antenna unit 200 according to another embodiment of the present invention is schematically illustrated.

[0064] Similar to Figure 2A , Fig. 6A An example arrangement of the transmission line 112 and the electrode 125 of the electrode structure 124 is shown. Unlike the liquid crystal antenna unit 100, in the liquid crystal antenna unit 200, the first surface S1 is defined as the surface of the second substrate 120 facing the first substrate 110, and the second surface S2 is defined as the surface of the first substrate 110 facing the second substrate 120. Therefore, in this embodiment, the transmission line 112 is located on the surface of the second substrate 120 facing the first substrate 110, and the electrode 125 of the electrode pattern 124 is located on the surface of the first substrate 110 facing the second substrate 120.

[0065] Similar to Figure 2B , Figure 6BAn example arrangement of second antenna element 122, first antenna element 118 and elongated electrode portion 114A is shown. Unlike liquid crystal antenna unit 100, in liquid crystal antenna unit 200, first antenna element 118 is located on a surface of second substrate 120 that faces first substrate 110.

[0066] In addition to the differences described here, the above Figure 1-5 The details and variations described for the liquid crystal antenna unit 100 may also be applicable to the liquid crystal antenna unit 200 and are therefore not repeated here.

[0067] Figure 7 The block diagram of a liquid crystal phased array antenna 700 according to an embodiment of the present invention is schematically illustrated.

[0068] refer to Figure 7 , the liquid crystal phased array antenna 700 includes a plurality of liquid crystal antenna units 710 arranged in an array. Each of the liquid crystal antenna units 710 may take the form of the liquid crystal antenna unit 100 or the liquid crystal antenna unit 200 described above, or a variation thereof, a detailed description of which is therefore omitted herein. The plurality of liquid crystal antenna units 710 may be applied with different modulation voltages through a feeding network (not shown) in order to change the phase of the electromagnetic wave signal, thereby realizing the functions of beam scanning and beam forming. Advantageously, the liquid crystal antenna unit 710 may provide a higher gain than a conventional patch antenna unit.

[0069] In some embodiments, each first substrate of the plurality of liquid crystal antenna units 710 is formed as a whole by a single substrate, and each second substrate of the plurality of liquid crystal antenna units 710 is formed as a whole by another single substrate. This is conducive to mass production of liquid crystal phased array antennas. Alternatively, the liquid crystal phased array antenna 700 can also be formed by combining separate liquid crystal antenna units 710.

[0070] The liquid crystal phased array antenna 700 is expected to provide higher gain because each antenna unit 710 as described above can provide higher gain. With the same antenna array size, the liquid crystal phased array antenna 700 can provide higher gain than a conventional liquid crystal phased array antenna. This improves communication performance.

[0071] The liquid crystal phased array antenna 700 is also expected to have a smaller size because each antenna element 710 can be made smaller than a conventional patch antenna element while still providing the same gain. With the same number of antenna elements in the array, the liquid crystal phased array antenna 700 can have a size that is approximately 1 / 2 of the size of a conventional liquid crystal phased array antenna. This saves antenna layout space.

[0072] Variations to the disclosed embodiments will be understood and effected by those skilled in the art in practicing the claimed subject matter by studying the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. A liquid crystal antenna unit, comprising: a first substrate; a second substrate, arranged opposite to the first substrate; a liquid crystal layer, disposed between the first substrate and the second substrate; a transmission line located on a first surface and arranged to extend in a first direction along the first surface, the first surface being selected from the group consisting of a surface of the first substrate facing the second substrate and a surface of the second substrate facing the first substrate; a first antenna element, located on the first surface and arranged as an elongated dipole extending in a second direction along the first surface, the dipole comprising two poles separated by a gap, the first antenna element being configured to couple electromagnetic waves between the two poles and the transmission line at the gap; a second antenna element, located at a position corresponding to the first antenna element on a surface of the second substrate facing away from the first substrate, the second antenna element having an elongated shape extending in the second direction along the surface of the second substrate facing away from the first substrate, and the second antenna element also having a length smaller than that of the first antenna element; as well as a ground electrode located on a surface of the first substrate facing away from the second substrate, the ground electrode comprising an elongated electrode portion located at a position corresponding to the first antenna element, the elongated electrode portion extending in the second direction along the surface of the first substrate facing away from the second substrate, the elongated electrode portion having a length greater than a length of the first antenna element, The transmission line comprises a coplanar waveguide transmission line, which comprises a signal line and two ground lines respectively located on both sides of the signal line, and the two ground lines have different lengths. 2 . The liquid crystal antenna unit according to claim 1 , wherein the length of the second antenna element is 0.7-0.9 times the length of the first antenna element. 3 . The liquid crystal antenna unit according to claim 1 , wherein the first substrate and the second substrate are made of the same material, and wherein the second substrate has a thickness 3 to 5 times greater than that of the first substrate.

4. The liquid crystal antenna unit according to claim 1, wherein the first substrate and the second substrate are made of different materials, and wherein the thickness of the first substrate and the thickness of the second substrate satisfy the following relationship: Wherein H1 is the thickness of the first substrate, H2 is the thickness of the second substrate, ε1 is the dielectric constant of the first substrate, and ε2 is the dielectric constant of the second substrate. 5 . The liquid crystal antenna unit of claim 1 , wherein the second substrate is a composite board including multiple layers of materials.

6. A liquid crystal antenna unit as described in claim 1, wherein the second antenna element, the first antenna element and the slender electrode portion are arranged so that the center of the second antenna element, the center of the gap in the first antenna element and the center of the slender electrode portion coincide in a direction perpendicular to the first substrate and the second substrate.

7. The liquid crystal antenna unit of claim 1, wherein the first direction is perpendicular to the second direction.

8. A liquid crystal antenna unit as described in claim 1, wherein one end of the signal line is electrically connected to one end of one of the two poles of the dipole close to the gap, and wherein one end of one of the two ground lines is electrically connected to one end of the other of the two poles of the dipole close to the gap.

9. The liquid crystal antenna unit of claim 1, wherein the first surface is a surface of the first substrate facing the second substrate, and wherein the liquid crystal antenna unit further comprises an electrode structure on the second surface, and the second surface is a surface of the second substrate facing the first substrate.

10. The liquid crystal antenna unit of claim 1, wherein the first surface is a surface of the second substrate facing the first substrate, and wherein the liquid crystal antenna unit further comprises an electrode structure on a second surface, the second surface being a surface of the first substrate facing the second substrate.

11. The liquid crystal antenna unit according to claim 9 or 10, wherein the electrode structure comprises a plurality of electrodes which are parallel to each other and extend along the second surface in a direction perpendicular to the first direction.

12. The liquid crystal antenna unit of claim 1, wherein the ground electrode further comprises an additional electrode portion extending from the elongated electrode portion in a direction perpendicular to the second direction along the surface of the first substrate facing away from the second substrate.

13. A liquid crystal phased array antenna, comprising a plurality of liquid crystal antenna units according to any one of claims 1 to 12 arranged in an array.

14. The liquid crystal phased array antenna of claim 13, wherein each first substrate of the plurality of liquid crystal antenna units is formed as a whole from a single substrate, and wherein each second substrate of the plurality of liquid crystal antenna units is formed as a whole from another single substrate.

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