Patent Description:
Wi-Fi is a wireless LAN standard, based on the IEEE standard <NUM>, which is widely used in home, offices and other indoor / outdoor environments. Wi-Fi operates in <NUM> frequency bands, <NUM> band and <NUM> band, and manages the communication between an Access point and clients (computers, smart handset, various devices, etc.). The Wi-Fi protocol was developed to provide service to numerous users at arbitrary locations of the Access point' s coverage area. In other words, the Access point needs to cover the entire area of its operation. For that reason, a Wi-Fi antenna typically has an omnidirectional beam for wide coverage.

The ultimate goal of any Wi-Fi system is to provide the highest possible throughput for each user. This goal requires a strong signal, to enable a good Signal to Interference and Noise Ratio (SINR). This goal also requires, when necessary, a narrow, directional beam, which may be directed with high gain in the direction of a particular user, while reducing the interference to other cells. Thus, an ideal Wi-Fi access point should be able to alternately emit an omnidirectional beam and to emit a narrow, directional beam.

Various solutions for alternating or diversifying beam coverage in Wi-Fi antennas are known. One such solution is based on the use of reflectors and directors. The principle of operation of such prior art Wi-Fi antennas is based on the well-known Yagi-Uda antenna. A Yagi-Uda antenna is a directional antenna consisting of multiple parallel elements in a line, usually half-wave dipoles made of metal rods. Yagi-Uda antennas consist of a single driven element connected to the transmitter or receiver with a transmission line, and additional parasitic elements which are not connected to the transmitter or receiver: a reflector and one or more directors. The reflector and director absorb and re-radiate the radio waves from the driven element with a different phase, modifying the dipole's radiation pattern. The waves from the multiple elements superpose and interfere to enhance radiation in a single direction, achieving a very substantial directional increase in the antenna's gain.

The Yagi-Uda concept has been applied for antenna elements of Wi-Fi Access points, to enable the Access point to emit different signal patterns. For example, a Wi-Fi access point may consist of a structure with one active element having two vertical bi-conical dipoles at the center of the structure, and a very large number of passive elements arranged in several circular arrays of different radiuses around it. Each passive element is made of several very short metal sections (e.g., shorter than <NUM>/<NUM> of a wavelength) which may be either shorted by diodes to one long passive element (around <NUM> wavelength) or left open. Shorting the passive elements thus changes them from directors to a reflector, and thereby changes the directional gain of the Wi-Fi access points. In another example, various passive elements may be arranged in series, with diodes configured therebetween. When the diodes are off, the passive elements act as directors. When the diodes are on, the length of the passive part is enlarged, and it acts as a reflector.

Another known model for modifying the transmission of Wi-Fi access points involves selectively activating one of a plurality of radiating dipoles, each of which is attached to a ground component. The selection of the active dipole or dipoles may be done by operating series switches, e.g., diodes, on the feeding line of each dipole near its input. The radiating dipoles are of different sizes or configurations. Each dipole may be chosen depending on the type or characteristics of the signal that is desired.

Another model for diversifying the signal at Wi-Fi access points involves integrating both horizontally and vertically polarized elements within a single Wi-Fi access point. This model does not alter any signal characteristics, but rather integrates various signals into a single Access point.

<CIT> discloses an antenna system including a radio frequency feed port and four antenna elements coupled to the feed port, and a series of selectively coupled parasitic elements connected between the dipoles and the port. The antenna elements may be selectively combined to obtain a substantially omnidirectional radiation, or a directional state.

<CIT> discloses an Alford antenna wherein each of the dipoles is selectively connected to the feed port.

<NPL>, XP033398528, DOI: <NUM>/CSQRWC. <NUM> , discloses an Alford loop antenna wherein the ends of the dipoles are not disconnected, and where the center of the dipoles are selectively connected via a switch to toggle between directional and omnidirectional patterns.

<NPL>, discloses an Alford antenna comprising parasitic elements positioned in a circle around the Alford antenna, and wherein the parasitic elements can be selectively connected to one another to alter between omnidirectional and directional radiation patterns.

The foregoing models for modifying the signals in Wi-Fi antennas all rely on the inclusion of additional elements in the antenna system. For example, reliance on the Yagi-Uda principle requires inclusion of passive devices to serve as directors and reflectors. Similarly, selection from a plurality of radiating dipoles requires inclusion of additional radiating dipoles. In addition, use of both horizontally and vertically polarized elements adds one or more radiating dipole into the access point, and is not useful for a standard Wi-Fi access point, in which there is a single antenna that is only horizontally or vertically polarized.

In addition, the above-described models, with their various additional passive elements, active dipoles, and/or antennas with multiple polarizations, require an access point with a comparatively larger area or footprint. The excess space is a particularly important consideration for enterprise-grade Wi-Fi access points. An enterprise-grade Wi-Fi access point supports two or three bands, with <NUM> or <NUM> antennas for <NUM>, and an additional four antennas for <NUM>. The additional elements required for each of the antennas would thus greatly enlarge the size requirements of the antenna device.

Accordingly, there is a need for a smart antenna device that provides the ability to alternate radiating beams between omnidirectional coverage and directional beam coverage. There is additionally a need for a smart antenna device that can respond to dynamic changes in the operational environment, in order to select properly when to utilize the omnidirectional beam coverage or the directional beam coverage. In addition, there is a need for a smart antenna device that incorporates an antenna which occupies a minimum of space.

It is therefore an object of the present invention to provide a smart antenna device with the ability to alternate radiating beams between omnidirectional coverage and directional beam coverage pointing to a specific sector within a coverage area. It is a further object of the present invention to provide such a smart antenna device that does not rely on inclusion of additional passive elements, as directors and reflectors.

According to a first aspect, an antenna device comprises a plurality of dipole antennas and a port. Each of the dipole antennas is connected to the port, and the plurality of dipole antennas are arranged around the port. Each of the plurality of dipole antennas comprises two ends. The ends of the dipole antennas are arranged in a plurality of pairs. Each pair comprises one end of one of the dipole antennas and one end of another one of the dipole antennas. The two ends in each pair are arranged in proximity to each other. One or more switches are configured to switch the antenna device between (<NUM>) an omnidirectional state, in which the ends of the dipole antennas are not connected to each other; and (<NUM>) a directional state, in which the two ends in each of one or more of the pairs are connected to each other.

An advantage of this aspect is that the antenna device may be switched between omnidirectional mode and directional mode without using any passive devices. Rather, the the mode switching operation is based on coupling of multiple dipole antennas to each other. In the omnidirectional state, when the dipole antennas are not connected to each other, the antenna device provides a high gain pattern in the azimuthal plane. The antenna device is also convertible to a high gain directional pattern in the azimuthal plane, when two ends in each of one or more of the pairs are connected to each other.

In an implementation of the antenna device according to the first aspect, in the directional state, at least two dipole antennas are combined into a single long radiating element having two feeding points. Advantageously, the at least two combined dipole antennas thus function as a single long radiating element antenna, thereby increasing the directional gain without requiring use of any passive elements.

In another possible implementation of the antenna device according to the first aspect, each of the plurality of dipole antennas comprises two asymmetric arms. The use of asymmetric arms causes the excitation of each dipole antenna to be asymmetric. This, in turn, enables using the same feeding network to match the antenna output, for both the omnidirectional state and the directional state.

In another possible implementation of the antenna device according to the first aspect, the plurality of dipole antennas are arranged around the port in a substantially rectangular or substantially circular orientation. Advantageously, these exemplary orientations are well suited for providing an omnidirectional signal.

In another possible implementation of the antenna device according to the first aspect, the plurality of dipole antennas are arranged horizontally above a ground plane. The ground plane may serve as a reflecting surface for the antenna waves of the dipole antennas, to increase the gain of the antenna device, in both the omnidirectional and directional states.

In another possible implementation of the antenna device according to the first aspect, the plurality of dipole antennas comprises at least three dipole antennas. A minimum of three dipole antennas is necessary in order to distinguish between the omnidirectional state, when none of the antennas are connected to each other, and the directional state, when at least two of the antennas are connected to each other and at least one is not connected.

In another possible embodiment of the antenna device according to the first aspect, the gain in the entire azimuth plane is at least <NUM> dBi. This gain in the azimuth plane enables the antenna to be used to transmit a Wi-Fi signal to a suitably large area.

In another possible implementation of the antenna device according to the first aspect, the difference in gain between the omnidirectional state and the directional state is at least <NUM> dB. Advantageously, the difference in gain in the desired direction in the directional state, as compared to the gain in that direction in the omnidirectional state, is suitably significant.

In another possible implementation of the antenna device according to the first aspect, the antenna device further comprises electronic circuitry for connecting and disconnecting ends of adjacent dipole antennas, and a control algorithm for determining which ends of adjacent dipole antennas to connect in order to steer an antenna beam of the antenna device in a directional state towards a location of one or more mobile devices. In this implementation, the antenna device is thus part of a smart antenna that may be toggled back and forth between the omnidirectional and directional states according to the needs of the environment, e.g., the location of mobile devices within a given range of the antenna device.

In another possible implementation of the antenna device according to the first aspect, the one or more switches comprise at least one of a diode, a transistor, and an electronic switch. These switches may be integrated with the control algorithm for toggling the smart antenna between the omnidirectional and directional states.

In a second aspect of the invention, a method for switching an antenna device from an omnidirectional state to a directional state is disclosed. The antenna device comprises a plurality of dipole antennas and a port. Each of the dipole antennas is connected to the port. The plurality of dipole antennas are arranged around the port. Each of the plurality of dipole antennas comprises two ends, and the ends of the dipole antennas are arranged in a plurality of pairs, each pair comprising one end of one of the dipole antennas and one end of another one of the dipole antennas. The two ends in each pair are arranged in proximity to each other. The antenna device further comprises a switch configured to switch the antenna device between (<NUM>) an omnidirectional state, in which the ends of the dipole antennas are not connected to each other; and (<NUM>) a directional state, in which the two ends in each of one or more of the pairs are connected to each other. The method comprises operating the at least one switch to connect two ends in each of one or more of the pairs, and thereby switching the antenna device from the omnidirectional state to the directional state.

An advantage of this aspect is that the method may be used to switch an antenna device between the omnidirectional state and directional state without using any passive devices. Rather, the antenna device is switched between the states based on coupling of multiple dipole antennas to each other. This switching operation thus enables providing a high gain omnidirectional pattern in the azimuthal plane, when the dipole antennas are not connected to each other. The antenna device may also be converted to a high gain directional pattern in the azimuthal plane, when two ends in each of one or more of the pairs are connected to each other.

In an implementation of the method according to the second aspect, the method comprises connecting at least a pair of adjacent dipole antennas into a single long radiating element having two feeding points. Advantageously, in the directional state, the at least two combined dipole antennas thus function as a single dipole antenna, which increases the directional gain without requiring use of any passive elements.

In an implementation of the method according to the second aspect, the method further comprises increasing the gain between the omnidirectional state and the directional state in at least one direction by at least <NUM> dB. Advantageously, the difference in gain in the desired direction in the directional state, as compared to the gain in that direction in the omnidirectional state, is suitably significant.

In an implementation of the method according to the second aspect, the method further comprises determining which direction to steer an antenna beam of the antenna device towards a location of one or more mobile devices. In this implementation, the antenna device is part of a smart antenna that may be toggled back and forth between the omnidirectional and directional states according to the needs of the environment, e.g., the location of mobile devices within a given range of the antenna device.

In a further implementation of the method according to the second aspect, the method further comprises determining when to revert the antenna device back to the omnidirectional state, and operating the one or more switches, and thereby switching the antenna device back from the directional state to the omnidirectional state. In this implementation, the antenna device is part of a smart antenna that may be toggled back and forth between the omnidirectional and directional states according to the needs of the environment, e.g., the location of mobile devices within a given range of the antenna device.

The present invention, in some embodiments thereof, relates to an antenna device, and, more specifically, but not exclusively, to an antenna device that may be used with a Wi-Fi access point.

Referring to <FIG>, antenna device <NUM> comprises a plurality of dipole antennas <NUM>, each electrically connected to port <NUM>. The port <NUM> is electrically connected via conducting wire <NUM> to power source <NUM>. The plurality of dipole antennas <NUM> may be arranged on an FR4 substrate, or on any other suitable substrate, such as a printed circuit board. The plurality of dipole antennas are arranged horizontally above a ground plane <NUM>. Ground plane <NUM> is a flat or nearly flat horizontal conducting surface extending underneath the dipole antennas <NUM>. For purposes of clarity, ground plane <NUM> may extend further outwards in all directions, and may have any suitable dimension. The ground plane may serve as a reflecting surface for the antenna waves of the dipole antennas <NUM>, to increase the gain of the antenna device <NUM>.

In the illustrated embodiment, there are four dipole antennas <NUM>. The choice of four dipole antennas <NUM> is merely exemplary, and there may be fewer or more dipole antennas <NUM>. In a preferred embodiment, there are at least three dipole antennas <NUM>. Each dipole antenna <NUM> is configured asymmetrically, with a feeding arm <NUM> connecting to the port <NUM>, a shorter arm <NUM> and a longer arm <NUM>. The ratio of the lengths of the shorter arm <NUM> compared to the longer arm <NUM> may be <NUM>:<NUM>. The sum of the lengths of the shorter arm <NUM> and longer arm <NUM> may be half of a wavelength of the transmitted signal. Thus, for example, when the transmitted signal is <NUM> (the midpoint of the <NUM> transmission band, which ranges between <NUM> and <NUM>), the wavelength of the transmitted signal is <NUM> in free space and about <NUM> in the FR4 substrate, and the cumulative length of arms <NUM>, <NUM> is about <NUM>. The Feeding arm <NUM> may be approximately <NUM> long.

The dipole antennas <NUM> are configured around the port <NUM> in a closed shape. In the illustrated embodiment, the closed shape is a rectangle; however, the closed shape may also be a circle, or any other polygon. The ends of arms <NUM>, <NUM> are either one above the other or in the same plane almost touching each other. The dipole antennas <NUM> thus define junction points <NUM>, <NUM>, <NUM>, and <NUM>, respectively at each of the interfaces between arm <NUM> of one dipole antenna <NUM>, and arm <NUM> of a second dipole antenna <NUM>.

A switch <NUM> is configured at each of the junction points <NUM>, <NUM>, <NUM>, <NUM>. The switch <NUM> comprises electronic circuitry for connecting and disconnecting ends of adjacent dipole antennas <NUM>. This electronic circuitry may be, for example, a diode, a transistor, and/or an electronic switch. The switch <NUM> is switchable between an "on" position, in which the electronic circuitry forms a closed, or shorted, circuit between the adjacent arms <NUM>, <NUM>, and an "off" position, in which the arms <NUM>, <NUM> remain unconnected. In the embodiment of <FIG>, each switch <NUM> is depicted as an open circle, indicating that it is in the "off" position. Switch <NUM> may be connected to a remote processor (not shown) with a control algorithm for determining whether to operate switch <NUM> at each of the junction points <NUM>, <NUM>, <NUM>, <NUM>. The remote processor and control algorithm may be used to toggle the antenna device <NUM> back and forth between the omnidirectional state and a directional state, as will be discussed further herein.

In the embodiment of <FIG>, because each switch <NUM> is in the "off" position, the antenna device <NUM> has an identical configuration throughout the entire circumference of antenna device <NUM>. For this reason, antenna device <NUM> generates an omnidirectional electric field, as will be discussed in connection with <FIG>, and is said to be in an omnidirectional state.

<FIG> depicts an electric field that is generated along each dipole antenna <NUM>, when the antenna device <NUM> is in the omnidirectional state. The strength of the electric field is measured in Volts per meter (V/m). For purposes of illustration, the strength of the electric field is divided into four regions. It is to be recognized that the variations in electric field across antenna device <NUM> are continuous, rather than discrete, and the following approximations of electric field for each particular region are for purposes of general explanation only. In region <NUM>, which represents the darkest region, the electric field is between <NUM> and <NUM> V/m. In region <NUM>, both near the port <NUM> and near each of the corners <NUM>, <NUM>, <NUM>, <NUM>, the electric field is between <NUM>,<NUM> and <NUM>,<NUM> V/m. In region <NUM>, both at feeding arm <NUM> and at arms <NUM> and <NUM>, the electric field is between <NUM>,<NUM> and <NUM>,<NUM> V/m. Finally, at a small part of dipoles <NUM> near corners <NUM>, <NUM>, <NUM>, <NUM>, the electric field increases to a maximum of <NUM>,<NUM> V/m.

<FIG> depicts the far electric field generated by antenna device <NUM> in the omnidirectional state. Far electric field <NUM> is measured in dBi as the azimuthal plane pattern, at frequency of <NUM>, with theta at <NUM>. As can be seen, far electric field <NUM> is measured at more than <NUM> dBi, and nearly <NUM> dBi, throughout the circumference of the azimuthal plane. The reason that the far electric field <NUM> has an omnidirectional profile is because the near electric field shown in <FIG> has circular symmetry. As a result, far field <NUM> has a low ripple omnidirectional pattern.

<FIG> and <FIG> depict the gain <NUM> generated by the antenna device in the omnidirectional state. <FIG> illustrates the shape of the gain <NUM> profile in three dimensions, and <FIG> depicts the values of the gain <NUM> for various regions in the <NUM> dimensional profile, expressed in dBi. As can be seen in <FIG> and <FIG>, in the omnidirectional state, the gain <NUM> can be measured along an approximately spherical plot. In addition, as seen best in <FIG>, the gain is approximately equivalent at each point along the azimuthal plane (i.e., a cross section taken along the X-Y planes). As seen in <FIG>, the realized gain in region <NUM> is <NUM> dBi; in region <NUM>, which is the largest region, the realized gain is between <NUM> and <NUM> dBi; in region <NUM>, which is limited to a small portion along the Z-axis, the realized gain is between-<NUM> to <NUM> dBi, and in the solid-colored region <NUM>, the realized gain is between -<NUM> to -<NUM> dBi. The differences in gain across the <NUM>-dimensional profile are continuous, rather than discrete, and the regions <NUM>, <NUM>, <NUM>, and <NUM> are drawn for purposes of general illustration only. <FIG> and <FIG> demonstrate that the antenna device <NUM> may generate a gain of at least <NUM> dBi in <NUM> dimensions.

<FIG> depicts the impedance matching of the antenna device <NUM> in the omnidirectional state. In electronics, impedance matching is the practice of designing the input impedance of an electrical load or the output impedance of its corresponding signal source to maximize the power transfer or minimize signal reflection from the load. In <FIG>, the matching is illustrated for S11 for frequencies in the <NUM> band. As is known to those of skill in the art, S11 is a measure of antenna efficiency that represents how much power is reflected from the antenna. This measure is known as the reflection coefficient or the return loss. For example, if S11 is <NUM> dBi, then all the power is reflected from the antenna, and none is radiated. If S11 is less than <NUM> dBi, it is an indication that a portion of the power is radiated from the antenna. The more that S11 is negative, the less the amount of power that is reflected from the antenna, and the more power is radiated from the antenna.

As seen in <FIG>, at <NUM>, the return loss, or matching (indicated on the Y-axis) is -<NUM> decibels; at <NUM>, the matching is -<NUM> decibels, and at <NUM>, the matching is -<NUM> decibels. Furthermore, as can be seen from the plot, the measured dBi is less negative at frequencies lower than <NUM> or higher than <NUM>. Thus, each dipole antenna <NUM> transmits most effectively (i.e., absorbs the least amount of power, and radiates best) at <NUM>.

Attention is now directed to <FIG>, which illustrate the antenna device <NUM> in a directional state. <FIG> illustrates the antenna device <NUM>, which is identical to the antenna device <NUM> as depicted in <FIG>, with the following exception: whereas in <FIG>, each of the switches <NUM> associated with junction points <NUM>, <NUM>, <NUM>, <NUM> was "off," in <FIG>, the switch <NUM> associated with junction point <NUM> is "on," and thus depicted as a filled circle, while the other switches <NUM> are off, and thus depicted as an open circle.

The effect of turning on the switch <NUM> at junction point <NUM> is to combine two adjacent dipole antennas <NUM> into a single long radiating element, or dipole antenna, <NUM> having two feeding points. The combined dipole antenna <NUM> thus extends from junction point <NUM>, through junction point <NUM>, which is now closed, and to junction point <NUM>. The other two dipole antennas remain as they were originally, each with ends <NUM>, <NUM>. The two combined dipole antennas <NUM> thus function as a single dipole antenna. The result of combining the two dipole antennas <NUM> is to change the current distribution on these dipole antennas. Specifically, the energy in the combined dipole antenna <NUM> is lower compared to the energy in the separate dipole antennas <NUM>. This increases the directional gain in the direction directly opposite the combined dipole antenna <NUM>, relative to the directions in which the dipole antennas <NUM> are combined.

Notably, the use of switch <NUM> enables the antenna device <NUM> to be switched between a directional state and an omnidirectional state without the use of passive elements or devices. Rather, the mechanism of the mode switching is based on coupling of multiple dipole antennas <NUM> to each other.

<FIG> depicts an electric field that is generated along each dipole antenna <NUM> and the combined dipole antenna <NUM>, when the antenna device <NUM> is in the directional state. The strength of the electric field is measured in Volts per meter (V/m). The strength of the electric field is divided into the same four regions <NUM>, <NUM>, <NUM>, <NUM> as in <FIG>. As described above in connection with <FIG>, it is to be recognized that the variations in electric field across antenna device <NUM> are continuous, rather than discrete, and the approximations of electric field for each particular region are for purposes of general explanation only.

As can be seen in <FIG>, and in contrast to the electric field of <FIG>, in the directional mode, the electric field is not symmetric around the entire antenna device <NUM>. For example, corners <NUM>, <NUM>, and <NUM> each include a high energy region <NUM>, as they did in the omnidirectional mode. However, corner <NUM> does not have an equivalent high energy region <NUM>. Rather, the maximum energy achieved in corner <NUM> is in middle energy region <NUM>. Similarly, further toward the port along each of the feeding arms <NUM>, the feeding arm <NUM> leading to corner <NUM> has a section with energy region <NUM>, whereas the equivalent areas on the other feeding arms <NUM> have an electric field within energy region <NUM>.

<FIG> depicts the far electric field generated by antenna device <NUM> in the directional state. Far electric field <NUM> is measured in dBi as the azimuthal plane pattern, at frequency of <NUM>, with theta at <NUM><IMG>. As can be seen, far electric field <NUM> exceeds <NUM> dBi between the angles of -<NUM><IMG> and <NUM><IMG>. At angles lower than -<NUM><IMG> and higher than <NUM><IMG>, the electric field <NUM> is lower than <NUM> dBi, and, at indentation <NUM>, it descends to nearly -<NUM> dBi at <NUM><IMG>. The reason that the far electric field <NUM> has a non-symmetrical profile is because of the asymmetry in the near electric field shown in <FIG>. The asymmetrical near electric field over the dipoles produces strong directivity in the far electric field, in the direction opposite combined antenna <NUM>.

<FIG> and <FIG>depict the gain <NUM> generated by the antenna device in the directional state. <FIG> illustrates the shape of the gain <NUM> profile in three dimensions, and <FIG> depicts the values of the gain <NUM> for various regions in the <NUM> dimensional profile, expressed in dBi. As can be seen in <FIG> and <FIG>, in the directional state, areas of high gain <NUM>, <NUM> assume an approximately hemispherical profile. The areas of low gain, such as area <NUM>, assume a less regular profile, corresponding to the indentation <NUM> in the curve of electric field <NUM>.

As seen in <FIG>, the realized gain is strongly directional. In region <NUM>, the realized gain is between <NUM> to <NUM> dBi; in region <NUM>, the realized gain is <NUM> to <NUM> dBi; in region <NUM>, the realized gain is -<NUM> to <NUM> dBi, in region <NUM> the realized gain is - <NUM> to -<NUM> dBi, in region <NUM> the realized gain is -<NUM>. 0087dBi to -<NUM> dBi, in region <NUM> the realized gain is -<NUM> to <NUM>-. <NUM> dBi, and in region <NUM> the realized gain is -<NUM> to -<NUM> dBi.

As can be seen from a comparison of the realized gain in <FIG>, <FIG> and <FIG> versus <FIG>, <FIG> and <FIG>, the maximum gain in the directional state is more than 3dBi greater than the maximum gain in the omnidirectional state. For example, the maximum gain in region <NUM> of <FIG> is <NUM> dBi, whereas the maximum gain in region <NUM> of <FIG> is <NUM> dBi. Thus, the directional state provides a significantly higher gain in the desired direction, compared to the gain in that direction in the omnidirectional state.

<FIG> depicts the impedance matching of the antenna device <NUM> in the directional state. In <FIG>, the matching is illustrated for S11 at a frequency of around <NUM>. As seen in <FIG>, at <NUM>, the matching (indicated on the Y-axis) is -<NUM> decibels; at <NUM>, the matching is -<NUM> decibels, and at <NUM>, the matching is -<NUM> decibels. A comparison of <FIG> and <FIG> shows that the frequency which results in the lowest return loss for the measured antenna device <NUM>, in both the omnidirectional and directional states, is <NUM>.

The ability of the antenna device <NUM> to obtain effective matching at two different frequencies is a result of the asymmetry between arms <NUM>, <NUM>. One of the main problems in design of smart antennas is matching. In the described embodiment, there is an array of four dipole antennas <NUM> on a single feeding network. Usually, with careful design of dipoles and their feeding network, one can get good matching for a single state, e.g., the omnidirectional state of the depicted embodiment. But, in the depicted embodiment, it is necessary to design a single feeding network that provides good matching in two states, omnidirectional and directional. This is achievable through the use of dipole antennas <NUM> with asymmetric arms, <NUM>, <NUM>. Given the comparatively narrow bandwidth of the <NUM> band, it is possible to determine a precise degree of asymmetry of the dipoles <NUM>, <NUM> that enables matching the structure in both the omnidirectional and directional states. In one embodiment, this degree of asymmetry is approximately <NUM>:<NUM>.

Antenna device <NUM> is particularly beneficial for transmission at <NUM>, compared to transmission at <NUM> using other devices that incorporate passive elements. This is because, usually, passive elements of a <NUM> antenna device resonate at <NUM>, causing strong coupling between all elements. This problem is intensified since modern access points provide high throughput by using massive MIMO (multiple input, multiple output) techniques, and which may have other antennas designed to transmit at <NUM>. Therefore for modern access points, that include large number of antennas (such as <NUM>, <NUM>, <NUM> or <NUM>), it is beneficial to avoid the use of passive elements, so as to reduce the coupling between elements. The absence of passive elements thus enables gaining strong directional gain, even with <NUM> elements nearby.

The described antenna device <NUM> has many other benefits compared to alternative devices. The structure of antenna device <NUM> has a small form-factor, which enables it to be included in a small size access point. Furthermore, the ability to achieve high gain in the omnidirectional mode enables achieving low error vector magnitude (EVM) with relatively high transmission power (high effective isotropic radiation power (EIRP)). Furthermore, the unique mechanism of the beam diversion in directional mode provides high additional gain. The antenna device <NUM> may be manufactured very simply, e.g., as a PCB trace antenna, and thus is cost-effective.

<FIG> depicts steps of a method <NUM> of switching an antenna device <NUM> from an omnidirectional state to a directional state, according to some embodiments of the invention. Antenna device <NUM> includes a plurality of dipole antennas <NUM> and a port <NUM>, in the manner discussed above. Each of the dipole antennas <NUM> is connected to the port <NUM>, and the plurality of dipole antennas <NUM> are arranged around the port <NUM>. Each of the plurality of dipole antennas <NUM> comprises two ends <NUM>, <NUM>, and the ends of the dipole antennas are arranged in a plurality of pairs, each pair comprising one end of one of the dipole antennas and one end of another one of the dipole antennas. The two ends in each pair are arranged in proximity to each other.

The method commences when antenna device <NUM> is in the omnidirectional state, which may be a default state. At step <NUM>, the device <NUM> optionally determines a desired direction of field for the directional state. This determination may be based on the detection of one or more mobile devices in the vicinity of antenna device <NUM>, e.g., when the one or more mobile devices are clustered in a particular direction relative to the antenna device <NUM>. The antenna device may be part of a smart antenna that may be toggled back and forth between the omnidirectional and directional states according to the needs of the environment, e.g., the sensing of mobile devices within a given range of the antenna device.

At step <NUM>, one or more switches <NUM> are operated, to switch antenna device <NUM> from the omnidirectional state to the directional state, so that the device <NUM> will generate a directional field in the desired direction. The operating step <NUM> comprises switching the switches between an omnidirectional state, in which the ends of the dipole antennas <NUM> are not connected to each other; and a directional state, in which the two ends in each of one or more of the pairs of ends are connected to each other. More specifically, the operating step <NUM> comprises operating the one or more switches to connect two of ends one or more of the pairs of dipole antennas <NUM>.

The method may accordingly be used to switch an antenna device between the omnidirectional state and directional state without using any passive devices. Rather, the antenna device is switched between the states based on coupling of multiple dipole antennas to each other. This enables providing a high gain omnidirectional pattern in the azimuthal plane, in the omnidirectional state, when the dipole antennas are not connected to each other, put also providing a to a high gain directional pattern in the azimuthal plane, when two ends in each of one or more of the pairs are connected to each other.

At step <NUM>, the method further comprises determining when to revert the antenna device back to the omnidirectional state. This determination may be based on the detection of one or more mobile devices in the vicinity of antenna device <NUM>, e.g., at numerous directions around the antenna device <NUM>. At step <NUM>, the method further comprises operating the one or more switches, and thereby switching the antenna device back from the directional state to the omnidirectional state. In this implementation, the antenna device <NUM> is part of a smart antenna that may be toggled back and forth between the omnidirectional and directional states according to the needs of the environment, e.g., the location of mobile devices within a given range of the antenna device <NUM>.

At step <NUM>, the method is reiterated. That is, upon detection of one or more devices in a single direction relative to the antenna device <NUM>, the antenna device <NUM> may be switched back to the directional state, in the manner described above.

As can be understood by those of skill in the art, each of the measurements for the electric field, gain, and impedance matching of the antenna device <NUM> discussed above are for one particular embodiment of the antenna device <NUM>. Adjustments in various parameters of the antenna device <NUM>, such as the length of arms <NUM>, <NUM>, the length of feeding arm <NUM>, the orientation of the dipole antennas <NUM> around the port <NUM>, the structure of the closed shape formed by the dipole antennas <NUM>, the size and location of ground plane <NUM> relative to the dipole antennas <NUM>, and the energy delivered from power source <NUM>, all influence the electric field, gain, and impedance matching. Accordingly, the values described above should be understood in an exemplary, as opposed to a limiting, sense.

The descriptions of the various embodiments of the present invention have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope of the appended claims. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

It is expected that during the life of a patent maturing from this application many relevant dipole antennas will be developed and the scope of the term dipole antenna is intended to include all such new technologies a priori.

The phrases "ranging/ranges between" a first indicate number and a second indicate number and "ranging/ranges from" a first indicate number "to" a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals there between.

Claim 1:
An antenna device (<NUM>) comprising:
a plurality of dipole antennas (<NUM>) and a port (<NUM>), wherein each of the dipole antennas (<NUM>) is connected to the port (<NUM>), and wherein the plurality of dipole antennas (<NUM>) are arranged around the port (<NUM>);
wherein each of the plurality of dipole antennas (<NUM>) comprises two ends (<NUM>, <NUM>), wherein the ends (<NUM>, <NUM>) of the dipole antennas (<NUM>) are arranged in a plurality of pairs, each pair comprising one end (<NUM>, <NUM>) of one of the dipole antennas (<NUM>) and one end (<NUM>, <NUM>) of another one of the dipole antennas (<NUM>), wherein the two ends (<NUM>, <NUM>) in each pair are arranged in proximity to each other; and
one or more switches (<NUM>) configured to switch the antenna device (<NUM>) between an omnidirectional state, in which the ends (<NUM>, <NUM>) of the dipole antennas (<NUM>) are not connected to each other; and a directional state, in which the two ends (<NUM>, <NUM>) in each of one or more of the pairs are connected to each other.