Patent Description:
Leaky-wave antennas, which consist of a waveguide structure that allows low-level continuous Radio Frequency (RF) radiation along the length of the guiding structure, are used in a number of applications including communications applications such as <NUM> networks and satellite communication. To ensure radiation is directed in a fixed direction, typical leaky-wave antennas require that, at a given frequency, the propagation constant of a radiated field along the structure be kept constant. As a result, typical leaky-wave antennas have uniform aperture geometries. This configuration results in a natural exponential decay in amplitude from the feed point along the aperture of the antenna. The asymmetrical amplitude tapering field typically results in poor sidelobe performance in the radiation patterns for such antennas. Further, a typical leaky-wave antenna permits angular scan in fixed frequency only, and can only scan in approximately half of the available space (e.g., <<NUM> degrees) due to the inherent positive propagation constant of the antenna.

Metamaterials (MTM) are artificial structures that behave differently from natural right-hand materials alone. A metamaterial may be made to operate in either or both left-handed and right-handed mode. Such materials are referred to as composite right-left-handed (CRLH) metamaterials. CRLH metamaterials can be engineered using conventional dielectric and conductive materials to produce unique electromagnetic properties.

CRLH metamaterial components may be fabricated on various substrates or circuit platforms such as conventional Printed Circuit Boards (PCBs) or flexible PCBs, providing an easily manufactured, inexpensive solution. The substrate may include a ground plane or a surface having a truncated or patterned ground portion or portions. Metamaterials including CRLH metamaterials can be used to construct antennas including leaky-wave antennas that avoid many of the drawbacks of conventional antennas including poor sidelobe performance and beams that are not electronically beam steerable.

<CIT> describes an electronically tunable metasurface whose reflective phase can be electronically reconfigured to allow effective antenna beam steering. First and second double sided substrates define an intermediate region between them containing liquid crystal in a nematic phase. The first substrate has a first microstrip patch array formed on a side thereof that faces the second substrate, the first microstrip patch array comprising a two-dimensional array of microstrip patches each being electrically connected to a common potential. The second double sided substrate has a second microstrip patch array formed on a side thereof that faces the first substrate, the second microstrip patch array comprising a two-dimensional array of microstrip patches each having a respective conductive control terminal. The first microstrip patch array and the second micro strip patch array are aligned to form a two dimensional array of cells, each cell comprising a microstrip patch of the first microstrip patch array arranged in spaced apart opposition to a microstrip patch of the second microstrip patch array with a volume of the liquid crystal located therebetween. The control terminal to the microstrip patch of the microstrip patch second array permitting a control voltage to be applied to the cell to control a dielectric value of the volume of the liquid crystal, thereby permitting a reflection phase of the cell to be selectively tuned.

FOO: "Liquid-crystal-tunable metasurface antennas", DOI: <NUM>/EUCAP. <NUM>, describes an electronically tunable metasurface using nematic liquid crystal. The proposed metasurface is a high impedance surface that contains electrically small scatterers loaded with liquid crystal, distributed in a periodic two-dimensional plane with a relatively small periodicity as compared to the operating wavelength. Distribution of reflection phase on the metasurface is reconfigurable by varying DC control voltages on unit cells across the metasurface. This tunable metasurface concept can be useful for development of relatively large, dual linearly polarized, electronically tunable, beam steering antennas, especially for millimeter wave applications.

<CIT> describes a reflector antenna that includes a feed for generating a radio frequency (RF) signal, and a metasurface reflector for reflecting the RF signal originating from the feed. The metasurface reflector includes an array of cells each having a volume of liquid crystal with a controllable dielectric value enabling a reflection phase of the cells to be selectively tuned to effect beam steering of the reflected RF signal.

SHUANG: "Beam scanning range expansion of liquid crystal based leaky wave antennas", DOI: <NUM>/ISEMC. <NUM>, describes a method to expand the electronic beam scanning range of liquid crystal based composite right/left handed leaky wave antennas (LCCRLH-LWAs) based on dispersion sensitivity enhancement (DSE). The proposed method does not need to modify the cell structure of the LC-CRLH-LWA, and the balanced condition and impedance matching property of the original LC-CRLH-LWA can be completely kept. For demonstration, a LC-CRLH-L WA is designed. It is shown that, by adding the DSE elements, the electronic beam scanning range of the LC-CRLH-LWA is extended by more than <NUM>%, in the frequency region from <NUM> to <NUM>, where the good impedance matching and balanced condition are kept for both extreme tuning states of LC. Finally, prototypes of the designed LC-CRLH-LWA are fabricated.

The present disclosure describes a practically realizable uniform leaky-wave antenna device. More specifically, in various examples, the present disclosure describes a two-dimensional (2D) electronically steerable millimeter-wave leaky-wave antenna that incorporates a plurality of liquid-crystal loaded CRLH metamaterials and which is capable of full-space beam steering over multiple frequencies and at a fixed frequency. By taking advantage of the right and left-handed properties of the CRLH metamaterial array, the antenna in various examples of the present disclosure can scan over the entire space (+/-<NUM> degrees) and produce an aperture field that results in radiation patterns with relatively low sidelobes without requiring a non-uniform leaky-wave antenna structure.

In some aspects the present disclosure describes an antenna including a first substrate, a second substrate, and a composite right- and left-handed (CRLH) metamaterial array disposed between the first and second substrates. The metamaterial array includes at least one pair of first and second rows of unit cells. One of the first and second rows of unit cells is controllable to operate in left-hand mode, and the other of the first and second rows of unit cells is controllable to operate in right-hand mode. The at least one pair is configured to propagate a radiation pattern along a first axis. Each unit cell includes a volume of liquid crystal with a controllable dielectric value and at least one isolated ground patch electrically isolated from the first and second substrates. The at least one isolated ground patch is configured as a virtual ground connection capable of generating a potential difference for tuning the dielectric value of the volume of liquid crystal. The first and second row of unit cells is oriented end-to-end along the first axis and separated from each other by a first distance. The antenna also includes a phase variable liquid-crystal loaded lens provided on the CRLH metamaterial array. The lens is controllable to be phase variable along at least a second axis orthogonal to the first axis.

In any of the preceding aspects/embodiments, the first or second substrate may include a ground plane of the antenna, the at least one isolated ground patch being electrically isolated from the ground plane.

In any of the preceding aspects/embodiments, the CRLH metamaterial array may include a first pair and a second pair of first and second rows of unit cells, the second pair of rows of unit cells being parallel to the first pair of rows of unit of cells, the first and second pair of rows of unit cells being separated by a second distance along the second axis.

In any of the preceding aspects/embodiments, the second distance between the first and second pair of unit cells may be one quarter of an operating wavelength of the antenna.

In any of the preceding aspects/embodiments, the first distance between the first and second rows of unit cells of the at least one pair of unit cells may be one quarter of an operating wavelength of the antenna.

In any of the preceding aspects/embodiments, the lens may be phase variable only along the second axis.

In any of the preceding aspects/embodiments, the lens may be phase variable along the first axis and is also phase variable along the second axis.

In any of the preceding aspects/embodiments, the first substrate may include a copper layer.

In some aspects, the present disclosure describes a composite right- and left-handed (CRLH) metamaterial unit cell. The unit cell includes a first substrate and a second substrate, and an intermediate region defined between the first and second substrates. The unit cell also includes series capacitors for electrically coupling the unit cell to one or more adjacent unit cells, and parallel inductors for electrically coupling the unit cell to ground. The series capacitors and parallel inductors together form a composite right- and left-hand metamaterial structure. The unit cell also includes a volume of liquid crystal located in a cavity disposed within the intermediate region. The unit cell also includes at least one electrically isolated ground patch. The at least one isolated ground patch is electrically isolated from ground and configured as a virtual ground connection capable of generating a potential difference in the volume of liquid crystal.

In any of the preceding aspects/embodiments, the series capacitor may be one of a planar capacitor, a circular capacitor, an interdigital capacitor, or a series-oriented parallel plate capacitor.

In any of the preceding aspects/embodiments, the parallel inductor may have two open ends in two terminals of the inductor.

In some aspects, the present disclosure describes a wireless communication device. The wireless communication device includes an antenna for receiving and transmitting wireless signals. The antenna includes a first substrate, a second substrate, and a composite right- and left-handed (CRLH) metamaterial array disposed between the first and second substrates. The metamaterial array includes at least one pair of first and second rows of unit cells. One of the first and second rows of unit cells is controllable to operate in a left-hand mode, and the other of the first and second rows of unit cells is controllable to operate in right-hand mode. The at least one pair is configured to propagate a radiation pattern along a first axis. Each unit cell includes a volume of liquid crystal with a controllable dielectric value and at least one isolated ground patch electrically isolated from the first and second substrates. The at least one isolated ground patch is configured as a virtual ground connection capable of generating a potential difference for tuning the dielectric value of the volume of liquid crystal. The first and second row of unit cells is oriented end-to-end along the first axis and separated from each other by a first distance. The antenna also includes a phase variable liquid-crystal loaded lens provided on the CRLH metamaterial array. The lens is controllable to be phase variable along at least a second axis orthogonal to the first axis. The wireless communication device also includes a processing device for providing control signals to the antenna. The control signals enable tuning of the volume of liquid crystal, to control direction of a beam of the antenna along the first axis. The control signals also enable control of the lens, to control direction of the beam along the second axis.

In any of the preceding aspects/embodiments, in the antenna, the first or second substrate may include a ground plane of the antenna, the at least one isolated ground patch being electrically isolated from the ground plane.

In any of the preceding aspects/embodiments, in the antenna, the CRLH metamaterial array may include a first pair and a second pair of first and second rows of unit cells, the second pair of rows of unit cells being parallel to the first pair of rows of unit of cells, the first and second pair of rows of unit cells being separated by a second distance along the second axis.

In any of the preceding aspects/embodiments, in the antenna, the second distance between the first and second pair of unit cells may be one quarter of an operating wavelength of the antenna.

In any of the preceding aspects/embodiments, in the antenna, the first distance between the first and second rows of unit cells of the at least one pair of unit cells may be one quarter of an operating wavelength of the antenna.

In any of the preceding aspects/embodiments, in the antenna, the lens may be phase variable only along the second axis.

In any of the preceding aspects/embodiments, in the antenna, the lens may be phase variable along the first axis and is also phase variable along the second axis.

Directional references herein such as "front", "rear", "up", "down", "horizontal", "top", "bottom", "side" and the like are used purely for convenience of description and do not limit the scope of the present disclosure. Furthermore, any dimensions provided herein are presented merely by way of an example and unless otherwise specified do not limit the scope of the disclosure. Furthermore, geometric terms such as "straight", "flat", "curved", "point" and the like are not intended to limit the disclosure any specific level of geometric precision, but should instead be understood in the context of the disclosure, taking into account normal manufacturing tolerances, as well as functional requirements as understood by a person skilled in the art.

Reference will now be made, by way of example, to the accompanying drawings which show embodiments of the present application, and in which:.

In at least some examples, the disclosed array antenna (also referred to simply as an antenna) includes a bidirectional composite right-left-handed (CRLH) metamaterial (MTM) array (also referred to simply as a metamaterial array) that includes at least one pair of first and second rows of unit cells. The metamaterial array is capable of supporting radio frequency (RF) transmission both in left-hand and right-hand wave propagation. The metamaterial array includes a liquid crystal (LC) loaded transmission line structure based on a modification to a grounded coplanar waveguide (GCPW), with a thin layer of additional substrate material over at least one surface. The volume of liquid crystal is encapsulated using first and second substrates of the antenna. The liquid crystal in the CRLH metamaterial array allows beam scanning over multiple frequencies or at a fixed frequency, over the full angular range including the broadside angle (i.e., zero degrees). In some examples, this can result in reduced beam degradation.

In at least some examples, a one-dimensional (1D) or two-dimensional (2D) liquid crystal-loaded metamaterial lens is provided over the CRLH metamaterial array to allow beam scanning in a second orthogonal direction, thus enabling beam steering in two dimensions. The liquid-crystal-loaded metamaterial lens can allow a transmission phase of each pair of rows of unit cells to be independently electronically tuned. The unit cells of the metamaterial array can be fed in groups to allow flexible hybrid beam forming for multiple beams, or can be fed with coherent phase to form a directional steerable beam.

As a result of the beam steerable capability of the LC-loaded CRLH metamaterial array and LC-loaded MTM lens, examples of the disclosed antenna may be able to produce a steerable beam having relatively low sidelobe, and relatively high gain. The beam may be steerable in a 2D plane parallel to the lens aperture. Examples of the disclosed antenna may be suitable for various wireless communications applications, such as <NUM> networks and satellite communications.

Referring to the Figures, <FIG> illustrates an antenna <NUM> that includes at least a first substrate <NUM> and a second substrate <NUM>. In the example of <FIG>, the first substrate <NUM> may be the bottom substrate and the second substrate <NUM> may be the top substrate. The antenna <NUM> may include conductive material printed onto the first substrate <NUM>. The first substrate <NUM> may act as a ground plane of the antenna <NUM> and may include a dielectric material that can electrically isolate a surface of the substrate <NUM> from another surface. A surface of the first substrate <NUM> may be a layer included in a multilayer structure such as at least a portion of a printed circuit board (PCB) or application board in a wireless-capable device.

The antenna <NUM> includes a CRLH metamaterial array <NUM> that can be provided on a surface of a first substrate <NUM> and a phase variable liquid-crystal loaded lens <NUM>. The lens <NUM> may enable control of the antenna beam in one dimension, or in two dimensions.

In some embodiments, the antenna <NUM> includes the first substrate <NUM>, the second substrate <NUM>, and a CRLH metamaterial array <NUM> disposed between the first and second substrates <NUM>, <NUM>. The CRLH metamaterial array <NUM> includes at least one pair of first and second rows 102a, 102b of unit cells <NUM> (see <FIG>). Each unit cell <NUM> includes a volume of liquid crystal <NUM> (see <FIG>) with a controllable dielectric value and one or more electrically isolated ground patches. The isolated ground patches are configured as one or more virtual ground connections capable of generating a potential difference in the volume of liquid crystal <NUM>.

The first and second rows 102a, 102b of unit cells each have a propagation direction along a first axis (which may be a longitudinal or transverse axis) of the first substrate <NUM>, and are oriented end-to-end and separated by a distance 106a along the first axis of the first substrate <NUM>. Generally, the CRLH metamaterial array <NUM> includes first and second rows 102a, 102b that operate in opposite propagation direction and are fed in opposite phases. Each row of unit cells (e.g. 102a, 102b) is capable of operating in either left-hand or right-hand mode. However, in at least some embodiments, the first and second rows of unit cells (e.g. 102a, 102b) may be controlled such that one row of the pair of unit cells (e.g. 102a) operates substantially in left-hand mode and the other row of unit cells (e.g. 102b) operates substantially in the right-hand mode.

In operation, at frequencies below a transition frequency of antenna <NUM>, a row of unit cells (e.g. 102a, 102b) operates in left-hand mode. At frequencies above the transition frequency, the same row of unit cells (e.g. 102a, 102b) operates in right-hand mode. Thus, the first and second rows 102a, 102b of the metamaterial array <NUM> operate in opposite propagation directions as one of the rows of unit cells (e.g. 102a) is configured to operate in left-hand mode by operating the row of unit cells 102a at a frequency below the transitional frequency. The other row of unit cells (e.g. 102b) is configured to operate in right-hand mode by operating the row of unit cells 102b at a frequency above the transitional frequency. In some examples, one row of unit cells (e.g., 102a) may be configured to operate mostly in the left-hand mode, and the other row of unit cells (e.g., 102b) may be configured to operate mostly in the right-hand mode. Such tuning of left-hand or right-hand mode operation may be made by implementing suitable variations in the physical parameters when manufacturing the respective rows 102a, 102b.

In some embodiments, the first and second rows of unit cells 102a, 102b are separated by a distance 106a that is about a quarter of the operational wavelength λ of the antenna <NUM>.

In the embodiment shown in <FIG>, the metamaterial array <NUM> also includes a second pair of first and second rows 102c, 102d of unit cells. The second pair of rows 102c, 102d are arranged parallel to the first pair of rows 102a, 102b (i.e., parallel to the longitudinal axis of the metamaterial array <NUM>. The two pairs of rows 102a, 102b; 102c, 102d are staggered and offset side-by side by a distance <NUM> along a transverse axis of the metamaterial array <NUM>. The distance <NUM> may be a quarter of the operational wavelength λ.

As mentioned above, the antenna <NUM> includes a liquid crystal loaded metamaterial lens <NUM>. The lens <NUM> is configured to be phase variable in one or two dimensions. In some embodiments, the lens <NUM> is phase variable only along the longitudinal axis of the metamaterial array <NUM> (in which case the lens <NUM> may be referred to as a one-dimensional or 1D lens). In other embodiments, the lens <NUM> may be phase variable along the longitudinal axis of the metamaterial array <NUM> and also along a transverse axis of the metamaterial array <NUM> (in which case the lens <NUM> may be referred to as a two-dimensional or 2D lens). In some embodiments, the diameter of the lens <NUM> is approximately <NUM>. The lens <NUM> may be positioned a distance F above the metamaterial array <NUM>. The distance F may be selected in order to achieve a desired value of F/D, where D is the diameter of the lens. In at least some embodiments, an F/D value of approximately <NUM> may be desired. In such cases, when the diameter of the lens <NUM> is about <NUM>, the distance F above the metamaterial array <NUM> is selected to be approximately <NUM>.

In at least some embodiments, a 1D lens, as described herein, may be used. A 1D lens may require fewer direct control lines compared to a 2D lens. A 2D lens may also have a limited aperture lens dimension due to DC control restriction, whereas in a 1D lens the aperture dimension in the beam steerable direction may not be restricted since DC control may be only required in one direction. This may help to eliminate or reduce distortion in beam patterns due to the presence of metallic DC walls. Such distortion may otherwise result in a limited angular scan range. Due to the complexity of wiring and connections of DC control signals, it is typically not practical to avoid the presence of metallic walls and maintain a low profile with 2D scanning using LC-loaded lens. A 2D lens may also be more complicated to control compared to a 1D lens, as a 1D lens may be easier to feed with a DC control signal.

<FIG> shows an example configuration of a CRLH metamaterial array <NUM>. In this embodiment, the CRLH metamaterial array <NUM> includes only one pair of first and second rows 102a, 102b of unit cells oriented with opposite propagation direction and fed to operate in opposite modes (i.e., one operating in left-hand transmission mode and the other operating in right-hand transmission mode) along the longitudinal axis of the CRLH metamaterial array <NUM>. In at least some embodiments, when the rows 102a, 102b are fed in opposite phase and separated by a distance <NUM> of approximately one quarter wavelength λ apart, steering over an angular range from +<NUM> degrees to -<NUM> degrees is possible. A high-gain, low-sidelobe radiation pattern can be produced (as seen in <FIG>). The sidelobe performance can be further improved by staggering another pair of rows (e.g., rows 102c, 102d shown in <FIG>) of unit cells alongside the first pair of rows 102a, 102b and separating the two pairs of rows by the offset distance <NUM>. The offset distance <NUM> may be substantially equal to the separation distance <NUM> (e.g., approximately a quarter of the operating wavelength λ).

Reference is now made to <FIG>, which shows a representative segment of one row 102a, 102b, 102c, 102d of unit cells. Each row 102a, 102b, 102c, 102d of unit cells is made of one or more liquid crystal loaded CRLH unit cells <NUM> that repeat to form the metamaterial transmission line structure of the one row of unit cells. A longer row of unit cells <NUM> may provide a higher gain of the antenna <NUM>.

An example unit cell <NUM> is shown in <FIG> shows a top-down view of the unit cell <NUM>, and <FIG> shows a side cross-sectional view of the unit cell <NUM>. The unit cell <NUM> includes portions of the first and second substrates <NUM>, <NUM>. In some embodiments, the first and second substrates <NUM>, <NUM> are provided by a portion of a PCB or application board. In some embodiments, the first and second substrates <NUM>, <NUM> are double sided PCBs. A volume of liquid crystal <NUM> is embedded in a cavity between the first and second substrates <NUM>, <NUM>. The liquid crystal <NUM> is thus encapsulated between the first and second substrates <NUM>, <NUM>. Encapsulation of the liquid crystal <NUM> within the unit cells <NUM> of the metamaterial array <NUM> may enable positive and negative electronic beam scanning, including scanning of the broadside angle (zero degrees). The other components of the unit cell <NUM> can be glued together and then positioned within first and second substrates <NUM>, <NUM>. Thus the unit cell <NUM> can be more easily manufactured using a scalable process, for example without requiring manual construction. In some embodiments (for example uniform leaky wave antennas), each of the unit cells <NUM> of the metamaterial array <NUM> have identical geometry and configurations. However, in at least some embodiments (for example non-uniform leaky wave antennas), one or more unit cells <NUM> of the metamaterial array <NUM> may have different geometries and configurations with differences in at least one of capacitors, inductors and positions of the virtual grounds. In some embodiments, the lengths of the pairs of first and second rows that make up the metamaterial array <NUM> are substantially equal (i.e. the lengths of rows 102a and 102b are substantially equal and the lengths of rows 102c and 102d are substantially equal).

The first and second substrates <NUM>, <NUM> of the unit cell <NUM> are oriented in spaced opposition to each other and may align with each other to form a region which contains a volume of liquid crystal <NUM>. In an example embodiment, first and second substrates <NUM>, <NUM> and the volume of liquid crystal <NUM> can be relatively thin, which may help to improve liquid crystal response to an electrostatic field that may be applied to tune the liquid crystal <NUM>.

In some embodiments, the volume of liquid crystal <NUM> can be a nematic liquid crystal or any other suitable liquid crystal. Where the liquid crystal <NUM> is a nematic liquid crystal, the nematic liquid crystal may have an intermediate nematic gel-like state between solid crystalline and liquid phase at the intended operating temperature range of the antenna <NUM>. Examples of suitable liquid crystals include, for example, GT3-<NUM> liquid crystal or BL038 liquid crystal from the Merck group. Liquid crystal <NUM> may possess dielectric anisotropy characteristics at microwave frequencies and the effective dielectric constant may be adjusted by setting different orientations of the molecules of liquid crystal <NUM> relative to its reference axis.

At microwave frequencies, the liquid crystal <NUM> may change its dielectric properties due to different orientations of the molecules caused by application of electrostatic field between the first and second substrates <NUM>, <NUM>. Thus, the effective dielectric constant can be tuned by varying the DC voltage applied to each unit cell <NUM>, allowing the transmission phase of the unit cells <NUM> to be controlled.

The unit <NUM> cell includes one or more ground planes 112a, 112b, 112c which may be provided on one or both sides of one or both of the first and second substrates <NUM>, <NUM>. The unit cell <NUM> includes two series capacitors <NUM> and two parallel inductors <NUM>. The unit cell <NUM> also includes one or more isolated patches configured as virtual grounds <NUM> of the unit cell <NUM>. The virtual ground(s) <NUM> are located on one side (e.g. the top side) of the first substrate <NUM>. The virtual ground(s) <NUM> are electrically isolated from DC by one or more slots <NUM>. The planar series capacitor <NUM> and parallel inductor <NUM> are arranged similar to a grounded coplanar waveguide (GCPW) configuration. As shown in <FIG>, the unit cell <NUM> includes the series capacitors <NUM> providing electrical coupling in series between adjacent unit cells <NUM>. The unit cell <NUM> also includes the parallel inductors <NUM> provide parallel electrical coupling to ground.

In the embodiment shown in <FIG>, the parallel inductors <NUM> and planar capacitors <NUM> are DC grounded via a DC ground plane of the unit cell <NUM>, which may be one or more of the ground planes 112a, 112b, 112c. Thus, isolated patches of the virtual ground <NUM> provide a means of introducing a DC bias voltage to tune the liquid crystal <NUM>. To introduce a potential difference in the volume of liquid crystal <NUM> between the first substrate <NUM> and the second substrate <NUM>, the virtual ground planes <NUM> may be provided on one side (e.g. the top side) of the first substrate <NUM> and positioned directly under the series capacitor <NUM> and the parallel inductors <NUM>, as shown in <FIG>. The isolated patches of the virtual ground <NUM> can be used as a substitute for an open microstrip transmission structure. Conventional microstrip transmission structures tend to require additional layers of substrate material. At higher operating frequencies, such as millimeter wave frequencies (e.g., as proposed for <NUM> communications), the additional substrate material can result in spurious transmission modes.

<FIG> shows a portion of the CRLH metamaterial array <NUM>, with a clearer view of the position of the virtual ground <NUM> and virtual ground slots <NUM>. The configuration of the virtual ground <NUM> enables control of static field strength in the volume of liquid crystal <NUM>, by enabling appropriate control voltages to be applied for electrically tuning the volume of liquid crystal <NUM>. The isolated patches of virtual ground <NUM> act as a virtual RF ground and permit changes of electrostatic field in the volume of liquid crystal <NUM> for beam steering. In operation, the virtual grounds <NUM> isolate the path of the DC current while allowing RF signals to propagate. Each isolated patch of virtual ground may <NUM> operate as an isolated ground at low frequencies while operating as a relatively continuous ground at high frequencies. Incorporation of the virtual grounds <NUM> in the unit cells <NUM> of the metamaterial array <NUM> and the GCPW configuration of the unit cell <NUM> may thus enable the introduction of DC voltages in the volume of liquid crystal <NUM> for beam scanning.

Reference is made to <FIG>, which shows an equivalent circuit of the example CRLH metamaterial array unit cell <NUM> of <FIG>. In this example, the unit cell <NUM> includes series capacitors <NUM> and parallel inductors <NUM> with finite length transmission lines. With the inherent right-hand circuit parameters in the finite transmission line length, the unit cell <NUM> can be characterized by four circuit parameters, namely right-hand capacitance CR, left-hand capacitance CL, right-hand inductance LR and left-hand inductance LL.

Dimensions of the capacitors <NUM> and the inductors <NUM> may be selected using simulation software (e.g., using iterative calculations) such as High Frequency Structure Simulator (HFSS) to generate the desired right-hand and left-hand capacitances and inductances (CL, CR, LL, LR). In example simulations, the transition frequency of the unit cell can be calculated using the following example equation: <MAT>.

Further, in example simulations where the antenna <NUM> is operating in balanced mode (i.e., when the series resonant frequency ωse is approximately equal to the shunt resonance frequency ωsh), the series and shunt resonance frequencies, respectively, can be calculated as follows: <MAT> <MAT>.

The above parameters are variable depending on the geometries of the structure and effective dielectric constant (ER) of the liquid crystal <NUM> embedded between the first and second substrates <NUM>, <NUM> which can be tuned as described herein.

When antenna <NUM> is in operation, the liquid crystal <NUM> may be controlled such that the antenna <NUM> is operating in the maximum scan angle when the effective dielectric constant is set at the lowest value (e.g., <NUM>). The antenna <NUM> may be controlled so that the radiation beam is slowly scanned from the initial angle through the broadside angle (i.e., <NUM> degrees) to the opposite angular space as the dielectric constant increases (e.g., from <NUM> to <NUM>).

Referring to <FIG>, the unit cell <NUM> of the CRLH metamaterial array <NUM> can also be implemented using various series capacitors and inductors with different geometries.

<FIG> show configurations of example series capacitors that can be used as part of unit cell <NUM> in place of the series capacitor <NUM> configuration shown in <FIG>. The different example configurations of the series capacitors may provide substantially similar performance at various frequencies. Possible variations of the planar series capacitor include series orientation parallel plate capacitors (<FIG>), interdigital finger series capacitor (<FIG>), or circularly shaped disk series capacitor (<FIG>). CRLH unit cells <NUM> with these configurations may provide series capacitor that are smaller in the transverse direction of the transmission line. This may be advantageous for CRLH metamaterial arrays in which a larger series capacitance is required in a more compact design. However, since these types of series capacitors have longer effective length in the propagation direction, they tend to have a higher right-hand parameters CR and LR, which may limit overall frequency bandwidth of a leaky wave antenna.

<FIG> shows an example configuration of a parallel inductor <NUM> that can be used as part of unit cell <NUM> in place of the parallel inductor <NUM> shown in <FIG>. The different example configurations of the parallel inductors may provide substantially similar performance at various frequencies. As seen in <FIG>, the parallel inductor has two open ends 116a in the two terminals 116b of the inductor <NUM>, instead of being grounded to the DC ground plane. This type of inductor configuration may result in higher right-hand capacitance and inductance. Consequently, this geometry may result in reduced frequency bandwidth and degraded antenna performances. However, in some cases, the inductor shown in <FIG> may be desirable. In the embodiments shown in <FIG>, the unit cells <NUM> are configured such that while virtual grounds <NUM> can be present, the structure of capacitors <NUM> and inductors <NUM> is such that virtual grounds <NUM> may not be required to introduce a DC bias into the unit cell <NUM>. In the embodiments shown in <FIG>, copper pattern layers of inductors <NUM> and capacitor <NUM> are not DC grounded. As a result, they can be directly connected to a source of DC voltage to tune the volume of liquid crystal <NUM>, thus obviating the need for a virtual ground. However, this may be at the expense of reducing the overall frequency bandwidth.

In general any combination of the inductors and capacitors shown in <FIG>, or other suitable capacitor and inductor configurations, may be used as part of the unit cell <NUM>.

As described above, in at least some embodiments, the CRLH metamaterial array <NUM> may include only one pair of first and second rows 102a, 102b of unit cells. This embodiment can also demonstrate improved sidelobe performance. <FIG> shows a plot of amplitude tapering of an example CRLH metamaterial array <NUM> shown in <FIG> (i.e., having one pair of first and second rows 102a, 102b of unit cells). To obtain the amplitude tapering shown in <FIG>, with symmetrical maximum in the middle of the CRLH metamaterial array <NUM>, power is injected in the middle of the metamaterial array <NUM> between the first and second rows 102a, 102b of unit cells along their end-to-end orientation. This configuration of the CRLH metamaterial array <NUM> may result in a radiation field that has a symmetrically decaying amplitude taper.

In operation, a first row of unit cells (e.g. 102a) operates in left-hand transmission mode and a second row of unit cells (e.g. 102b) operates in right-hand transmission mode. As a result of the opposite propagation direction of the respective unit cells, the CRLH metamaterial array <NUM> is therefore able to scan from positive angular space (right-hand mode) to negative angular space (left-hand mode).

<FIG> shows the S-<NUM> transmission parameter of a CRLH metamaterial array <NUM> with one pair of first and second rows 102a, 102b of unit cells designed to have a transition frequency of <NUM>. Below <NUM>, the array <NUM> can operate in left-hand propagation mode. Above <NUM>, the array <NUM> operates in right-hand propagation mode. In at least some embodiments, the CRLH metamaterial array <NUM> can operate between <NUM> and <NUM>, with a frequency bandwidth of over <NUM>%.

<FIG> shows example radiation patterns to illustrate the performance of an example of the disclosed antenna <NUM> having a CRLH metamaterial array <NUM>. For comparison, <FIG> shows the radiation pattern for a single row of unit cells. <FIG> also shows the radiation pattern for a CRLH metamaterial array <NUM> with one pair of rows 102a, 102b of unit cells fed in opposite phase and separated by a quarter wavelength λ; and a CRLH metamaterial array <NUM> with two pairs of parallel rows 102a, 102b; 102c, 102d of unit cells, with each respective pair fed in opposite phase, the two pairs being staggered by a quarter wavelength λ and separated by a quarter wavelength λ. As can be seen from <FIG>, a CRLH metamaterial array <NUM> with a single pair of rows of unit cells 102a, 102b, spaced a quarter wavelength λ apart end-to-end, results in an improved radiation pattern and improved sidelobes as compared to only one row of unit cells. In some examples, adding a second pair of first and second rows 102c, 102d of unit cells can further improve sidelobe performance, particularly in the far end of the radiation patterns of antenna <NUM>.

<FIG> shows example radiation patterns of an example antenna <NUM> with a metamaterial array <NUM> with a single pair of rows 102a, 102b of unit cells over a range of frequencies and with the liquid crystal dielectric constant fixed at <NUM>. <FIG> shows radiation patterns of a comparable antenna <NUM> at a fixed frequency of <NUM> over a range of dielectric constants of the liquid crystal from <NUM> and <NUM>. A DC bias voltage can be introduced to change the dielectric constant, thus changing the beam angle. As described herein, the dielectric constant can be changed by applying a potential difference in the volume of liquid crystal <NUM> using the isolated ground patches of the virtual ground <NUM>. Thus, as shown in <FIG> and <FIG>, the antenna <NUM> is able to scan in left-hand and right-hand mode over a continuous frequency range and at a single frequency, over a continuous angular range, by tuning the liquid crystal through changing the dielectric constant. The disclosed configuration of the unit cell <NUM> enables a practical way to encapsulate the liquid crystal and to enable practical tuning of the liquid crystal.

It should be noted that <FIG> and <FIG> show the ability of the metamaterial array <NUM> to scan over a continuous angular range, along one dimension (e.g., along the axis of the metamaterial array <NUM>). The lens <NUM> of the antenna <NUM> may be controlled to control the angle of the antenna beam in an orthogonal direction, such that the overall antenna <NUM> may be capable of scanning over two dimensions.

The embodiments disclosed herein may provide a number of advantages compared to conventional leaky wave antenna arrays. The embodiments disclosed herein are beam steerable in two dimensions over the full available space. Compared to a conventional leaky-wave antenna arrays, the embodiments described herein are electronically beam steerable by using electrostatic control of liquid crystal. Moreover, the example antenna <NUM> can provide two dimensional bidirectional beam steering over a range of frequencies, or a fixed frequency, using the composite right-left-handed (CRLH) waveguide structure. The waveguide structure of antenna <NUM>, includes a CRLH metamaterial array having two rows of LC-loaded unit cells, each row operating in opposite propagating mode (one in right-hand mode and the other in left-hand transmission mode) with a separation in array distance by approximately quarter wavelength. This has been found to result in substantially symmetrical amplitude taper and improved sidelobe performance in radiation patterns compared to a conventional uniform leaky-wave antenna. In various embodiments, the disclosed antenna <NUM> provides a practically realizable antenna that may enable full-space beam steering (e.g., +/-<NUM> degrees), including the broadside angle (i.e., zero degrees), without narrowing the frequency band and without resulting in undesirably high sidelobes in the radiation patterns.

In some embodiments, antenna <NUM> can be incorporated into a wireless device for example mobile communication devices, satellite communication devices, wireless routers, and other wireless and telecommunication applications. The wireless devices may include additional components such as controllers for controlling operation of modules and components within the device. The devices may be used in a stationary or mobile environment. The device may also include one or more antenna controllers to control operation of the components of antenna <NUM>. The wireless device may include additional hardware, software, firmware or a combination thereof and may include peripheral devices.

<FIG> is a schematic diagram of an example wireless communication device <NUM>, in which examples of the antenna <NUM> described herein may be used. For example, the wireless communication device <NUM> may be a base station, an access point, or a client terminal in a wireless communication network. The wireless communication device <NUM> may be used for communications within <NUM> communication networks or other wireless communication networks. Although <FIG> shows a single instance of each component, there may be multiple instances of each component in the wireless communication device <NUM>. The wireless communication device <NUM> may be implemented using at least one of a parallel architecture and a distributed architecture.

The wireless communication device <NUM> may include one or more processing devices <NUM>, such as a processor, a microprocessor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a dedicated logic circuitry, or combinations thereof. The wireless communication device <NUM> may also include one or more optional input/output (I/O) interfaces <NUM>, which may enable interfacing with one or more optional input devices <NUM> and output devices <NUM>. The wireless communication device <NUM> may include one or more network interfaces <NUM> for wired or wireless communication with a network (e.g., at least one of an intranet, the Internet, a P2P network, a WAN, a LAN, and a Radio Access Network (RAN)) or other node. The network interface(s) <NUM> may include one or more interfaces to wired networks and wireless networks. Wired networks may make use of wired links (e.g., Ethernet cable). The network interface(s) <NUM> may provide wireless communication (e.g., full-duplex communications) via an example of the disclosed antenna <NUM>. The wireless communication device <NUM> may also include one or more storage units <NUM>, which may include a mass storage unit such as one or more of a solid state drive, a hard disk drive, a magnetic disk drive and an optical disk drive.

The wireless communication device <NUM> may include one or more memories <NUM> that can include a physical memory <NUM>, which may include a volatile or non-volatile memory (e.g., one or more of a flash memory, a random access memory (RAM), and a read-only memory (ROM)). The non-transitory memory(ies) <NUM> (as well as storage <NUM>) may store instructions for execution by the processing device(s) <NUM>. The memory(ies) <NUM> may include other software instructions, such as for implementing an operating system (OS), and other applications/functions. In some examples, one or more data sets or modules may be provided by an external memory (e.g., an external drive in wired or wireless communication with the wireless communication device <NUM>) or may be provided by a transitory or non-transitory computer-readable medium. Examples of non-transitory computer readable media include a RAM, a ROM, an erasable programmable ROM (EPROM), an electrically erasable programmable ROM (EEPROM), a flash memory, a CD-ROM, or other portable memory storage.

There may be a bus <NUM> providing communication among components of the wireless communication device <NUM>. The bus <NUM> may be any suitable bus architecture including, for example, a memory bus, a peripheral bus or a video bus. Optional input device(s) <NUM> (e.g., at least one of a keyboard, a mouse, a microphone, a touchscreen, and a keypad) and optional output device(s) <NUM> (e.g., one or more of a display, a speaker and a printer) are shown as external to the wireless communication device <NUM>, and connected to optional I/O interface <NUM>. In other examples, one or more of the input device(s) <NUM> and the output device(s) <NUM> may be included as a component of the wireless communication device <NUM>.

The processing device(s) <NUM> may be used to control communicate transmission/reception signals to/from the antenna <NUM>. The processing device(s) <NUM> may be used to control beam steering by the antenna <NUM>, for example by controlling the voltage applied to the isolated ground of the unit cells, for tuning the encapsulated liquid crystal. The processing device(s) <NUM> may also be used to control the phase of the phase variable lens, in order to steer the antenna beam over a 2D plane.

Claim 1:
A composite right- and left-handed, CRLH, metamaterial unit cell (<NUM>) comprising:
a first substrate (<NUM>) and a second substrate (<NUM>);
an intermediate region defined between the first and second substrates; and
a volume of liquid crystal (<NUM>) located in a cavity disposed within the intermediate region,
characterized by further comprising:
series capacitors (<NUM>) for electrically coupling the unit cell to one or more adjacent unit cells, and parallel inductors (<NUM>) for electrically coupling the unit cell to ground;
the series capacitors and parallel inductors together forming a composite right- and left-hand metamaterial structure; and
at least one electrically isolated ground patch (<NUM>), the at least one isolated ground patch being electrically isolated from ground and configured as a virtual ground connection capable of generating a potential difference in the volume of liquid crystal.