Patent Description:
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.

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.

Document <CIT> relates to methods, apparatuses and systems which are provided for use in a wireless routing network, including an adaptive antenna that is configurable to receive a transmission signal from a transmitter and in response transmit corresponding outgoing multi-beam electromagnetic signals exhibiting a plurality of selectively placed transmission peaks and transmission nulls within a far field region of a coverage area.

Document <CIT> relates to a system and method for a wireless link to a remote receiver and includes a communication device for generating RF and a planar antenna apparatus for transmitting the RF, wherein the planar antenna apparatus includes selectable antenna elements, each of which has gain and a directional radiation pattern.

Document <CIT> relates to a switchable antenna that includes a substrate, a first antenna element, a second antenna element, a first switch element, a second switch element, a first radiating portion on an upper surface of the substrate including a first center, a first bend section and a second bend section, and a second radiating portion on an lower surface of the substrate including a second center, a third bend section and a fourth bend section.

<NPL>, describes a <NUM> ° beam-steerable frequency-reconfigurable antenna that is based on an Alford loop and a parasitic circular array of resonators.

<NPL>, describes an Alford antenna further comprising parasitic elements positioned in a circle around the Alford antenna.

The foregoing models for modifying the signals in Wi-Fi antennas all rely on the inclusion of additional, space-consuming elements in the antenna system. For example, reliance on the Yagi-Uda principle requires inclusion of a large number 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, above-described models, with their various additional passive elements, active dipoles, and/or antennas with multiple polarizations, require an access point with a 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.

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 antenna device further comprises a plurality of passive elements. The ends of the plurality of dipole antennas and the plurality of passive elements are, e.g. interchangeably, arranged around the port, such that each of the plurality of passive elements is situated between ends of two different antennas from the plurality of dipole antennas. One or more switches are configured to switch between an omnidirectional state, in which the ends of the dipole antennas are not connected to the plurality of passive elements, and a directional state, in which at least one end of one of the plurality of passive elements is connected to at least one end of one of the plurality of antennas.

An advantage of this aspect is that the antenna device may be switched between omnidirectional state and the directional state using only passive elements that are situated on the perimeter of the array of dipole antennas. This permits mode switching without increasing the space requirement of the antenna device. 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 ends of one of the plurality of passive elements are connected to two different antennas, thereby converting the two different antennas 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.

In another possible implementation of the antenna device according to the first aspect, the plurality of dipole antennas and the plurality of passive elements 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 antenna, 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 example, which is not covered by the claims, 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, which is not covered by the claims, 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 each passive element and adjacent antenna, and a control algorithm for determining which passive element to connect to an adjacent antenna, 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. The 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. The antenna device further comprises a plurality of passive elements interchangeably arranged around the port such that each of the plurality of passive elements is situated between two different antennas from the plurality of dipole antennas. The antenna device further comprises one or more switches configured to switch between (<NUM>) an omnidirectional state, in which the ends of the dipole antennas are not connected to the plurality of passive elements; and (<NUM>) a directional state, in which at least one of the plurality of passive elements is connected to at least one end of one of the plurality of dipole antennas. The method comprises operating the one or more switches to connect at least one end of the at least one of the plurality of passive elements to at least one end of the plurality of dipole antennas, 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 the antenna device between the omnidirectional state and the directional state using only passive elements that are situated on the perimeter of the array of dipole antennas. This permits mode switching without increasing the space requirement of the antenna device. 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 method according to the second aspect, the method comprises connecting at least one of the plurality of passive elements to two different antennas, thereby converting the two different 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 long radiating element antenna.

In an implementation of the method according to the second aspect, which is not covered by the claims, 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.

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 FR-<NUM> 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 three dipole antennas <NUM>. The choice of three 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>, and arms <NUM> and <NUM>. In the depicted embodiment, arms <NUM> and <NUM> are approximately equal in length. However, arms <NUM> and <NUM> may also be asymmetrical. The dipole antenna <NUM> may have a total length that is half of the wavelength of the transmitted signal. Thus, for example, for a signal transmitted at <NUM>, the wavelength is <NUM> in free space and about <NUM> on the FR4 substrate, and the total length of both arms of dipole antenna <NUM>, printed on the FR4 substrate, is about <NUM>.

The dipole antennas <NUM> are configured around the port <NUM> in a closed shape. In the illustrated embodiment, the closed shape is a circle; however, the closed shape may also be a rectangle, or any other polygon.

Passive elements <NUM> are configured between arms <NUM>, <NUM> of the antennas. Passive elements <NUM> are metal strips. The passive elements <NUM> are configured on the perimeter of a circular or polygonal array around port <NUM>. The length of each passive element is also approximately half of the transmitted wavelength, e.g., <NUM> for a <NUM> signal.

Passive elements <NUM> are configured adjacent to arms <NUM>, <NUM> of dipole antenna <NUM>. The passive elements <NUM> and the arms <NUM>, <NUM> define junction points around the perimeter of the antenna array. In the illustrated embodiment, in which there are three antennas <NUM>, there are six junction points, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. The ends of arms <NUM>, <NUM> are either above the corresponding passive element <NUM> or in the same plane almost touching the passive element <NUM>.

A switch <NUM> is arranged at each of the junction points <NUM>-<NUM>. The switch <NUM> comprises electronic circuitry for connecting and disconnecting the passive elements <NUM> and the adjacent arms <NUM>, <NUM> of the 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 passive elements <NUM> and arms <NUM>, <NUM>, and an "off" position, in which the passive elements <NUM> and 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. The switches <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>. 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 five 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>, both on feeding arms <NUM> and on the perimeter of antenna device <NUM> (both the region of arms <NUM>, <NUM> and the passive elements <NUM>, which is unconnected to the rest of antenna device <NUM>) the electric field is between <NUM> and <NUM>,<NUM> V/m. In region <NUM>, both on feeding arms <NUM> and on the perimeter of antenna device <NUM>, the electric field is between <NUM>,<NUM> and <NUM>,<NUM> V/m. In region <NUM>, both on feeding arm <NUM> and on the perimeter of the antenna device <NUM>, the electric field is between <NUM>,<NUM> and <NUM>,<NUM> V/m. In region <NUM>, both on feeding arm <NUM> and on the perimeter of antenna device <NUM>, the electric field is between <NUM>,<NUM>-<NUM>,<NUM> V/m. Finally, at region <NUM>, corresponding to the portion of the dipole antennas <NUM> closest to port <NUM>, and also at a small portion of the antenna arms <NUM>, the electric field is between <NUM>,<NUM> and <NUM>,<NUM> V/m. As can be seen, the electric field is symmetrical around the perimeter of antennas <NUM>, and there is no meaningful distinction in the electric field at corners <NUM>, <NUM>, <NUM>, and <NUM> of antenna device <NUM>.

<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 <IMG>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 <NUM> 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 ellipsoidal 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> to -<NUM> dBi; in region <NUM>, the realized gain is between -<NUM> and -<NUM> dBi; in region <NUM>, the realized gain is between -<NUM> dBi and <NUM> dBi; in region <NUM>, the realized gain is between <NUM> to <NUM> dBi; in region <NUM>, which is the largest region, the realized gain is between <NUM> dBi and <NUM> dBi; and in region <NUM>, the realized gain is around <NUM> dBi. The differences in gain across the <NUM>-dimensional profile are continuous, rather than discrete, and the regions <NUM>-<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 at a frequency range of <NUM> to <NUM>. 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. Thus, each dipole antenna <NUM> transmits effectively at all frequencies between <NUM> and <NUM>, and, from the measured range, 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> was "off," in <FIG>, the switch <NUM> associated with junction points <NUM> and <NUM> are "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 switches <NUM> at junction points <NUM> and <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 points <NUM> and <NUM>, which is now closed, including passive element <NUM> which is between junction points <NUM> and <NUM>, and to junction point <NUM>. The other dipole antenna <NUM> and passive elements <NUM> remain as they were originally. The two combined dipole antennas <NUM> and passive element <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 switches <NUM> enables the antenna device <NUM> to be switched between a directional state and an omnidirectional state using only passive elements <NUM> that are situated on the perimeter of the array of dipole antennas. This permits mode switching without increasing the space requirement of the antenna device <NUM>. The mode switching is based on using the passive elements <NUM> to couple 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 five regions <NUM>, <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, the maximum energy achieved in passive elements <NUM> that are not part of combined dipole antenna <NUM> is in the highest energy region <NUM>. Such high energy regions are located, for example, at junction points <NUM>, <NUM>, <NUM>, and <NUM>. However, no such high energy region <NUM> exists at closed junction points <NUM>, <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 <IMG> As can be seen, far electric field <NUM> exceeds <NUM> dBi between the angles of <IMG> and <IMG> At angles lower than <IMG> and higher than <IMG> the electric field <NUM> is lower than <NUM> dBi, and, between <IMG> and <IMG> it descends to below <NUM> dBi. 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 areas <NUM> and <NUM>, assume a more limited profile, and approximately correspond to the low gain area of the far electric field as depicted in <FIG>.

As seen in <FIG>, the realized gain is strongly directional. In region <NUM>, the realized gain is around <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> dBi to -<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 3dB 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, in both the omnidirectional and directional states, there is a wide band of frequencies with matching below -<NUM> decibels. Specifically, the matching is below -<NUM> decibels across the entire range of <NUM> to <NUM>.

The presence of passive elements <NUM> plays an important role in enabling the above-described wide band matching. One of the main problems in design of smart antennas is matching. In the described embodiment, there is an array of three 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. With careful design of the passive elements <NUM>, i.e., with specific calculation of their length and width (e.g., a length that is half the transmitted wavelength), it is possible to achieve wide matching in both the omnidirectional and directional mode (based on the principle that two dipole antennas <NUM> and one passive element <NUM> turn into a single radiating element <NUM> with two excitations).

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> comprises a plurality of dipole antennas <NUM> and a common port <NUM>. Each of the dipole antennas <NUM> is connected to the common port <NUM>. 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>. The antenna device further comprises a plurality of passive elements <NUM> interchangeably arranged around the port <NUM> such that each of the plurality of passive elements <NUM> is situated between two different antennas <NUM> from the plurality of dipole antennas <NUM>. The antenna device <NUM> further comprises one or more switches <NUM> configured to switch between (<NUM>) an omnidirectional state, in which the ends <NUM>, <NUM> of the dipole antennas <NUM> are not connected to the plurality of passive elements <NUM>; and (<NUM>) a directional state, in which at least one of the plurality of passive elements <NUM> is connected to at least one end <NUM>, <NUM> of one of the plurality of dipole antennas <NUM>.

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 antenna device <NUM> from an omnidirectional state, in which none of the ends of passive elements <NUM> and dipole antennas <NUM> connect to each other, to a directional state, in which at least one end of at least one of the passive elements <NUM> is connected to at least one end of one of the dipole antennas <NUM>. More specifically, the operating step <NUM> comprises operating the one or more switches <NUM> to connect an adjacent passive element <NUM> and dipole antennas <NUM>.

Advantageously, the method may be used to switch the antenna device between the omnidirectional state and the directional state using only passive elements that are situated on the perimeter of the array of dipole antennas. This permits mode switching without increasing the space requirement of the antenna device. 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.

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 <NUM>, 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 passive elements <NUM>, the length of feeding arm <NUM>, the orientation of the dipole antennas <NUM> and passive elements <NUM> around the port <NUM>, the structure of the closed shape formed by the dipole antennas <NUM> and passive elements <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. 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 and passive elements will be developed and the scope of the term dipole antenna and passive element 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 is connected to the port (<NUM>), wherein the plurality of dipole antennas (<NUM>) are arranged around the port (<NUM>), and wherein each of the dipole antennas comprises two ends;
a plurality of passive elements (<NUM>), wherein the ends of the plurality of dipole antennas (<NUM>) and the plurality of passive elements (<NUM>)are arranged around the port (<NUM>) such that each of the plurality of passive elements (<NUM>) is situated between ends of two different dipole antennas from the plurality of dipole antennas (<NUM>); and
one or more switches (<NUM>) configured to switch the antenna device (<NUM>) between an omnidirectional state, in which the ends of the dipole antennas are not connected to the plurality of passive elements (<NUM>), and a directional state, in which at least one end of one of the plurality of passive elements (<NUM>) is connected to at least one end of one of the plurality of dipole antennas (<NUM>).