Patent Description:
The present disclosure relates to directional or steerable beam antennas, of the type employed in such applications as radar and communications. More specifically, it relates to leaky-waveguide antennas, of the type including a dielectric feed line (i.e., a potentially leaky waveguide) loaded with scatterers, wherein the degree of scattering can be controllably altered by the actuation of a plurality of switches, whereby the antenna's beam shape and direction are determined by the pattern of the switches that are respectively turned on and off.

Steerable beam antennas, particularly leaky-wave antennas, are capable of sending electromagnetic signals in, and receiving electromagnetic signals from, desired directions. Such antennas are used, for example, in various types of radars (e.g., surveillance radar, collision avoidance radar), and in communications. In such antennas, the receiving or transmitting beam is generated by a set of scattering elements ("scatterers") coupled to the feed line or waveguide. Interacting with the feed line, the scatterers create leaky waves decoupled from the feed line. If the scatterers are properly phased, they create a coherent beam propagating in a specific direction. The leakage strength and phase caused by each scatterer depend on the geometry and location of the scatterer relative to the feed line or waveguide. The degree of scattering, and thus the beam shape and direction, can be controlled by changing the topology and/or geometry of the scattering-element current lines. This can be done by using microwave (or other suitable) switches connecting parts of the scatterers. Thus, the beam shape, including its direction, can be controlled electronically by changing the operational mode of the switches. Different ON/OFF switch patterns result in different beam shapes and/or directions.

Any of several types of switches integrated into the structure of the antenna elements or scatterers may be used for this purpose, such as semiconductor switches (e.g., PIN diodes, bipolar and MOSFET transistors, varactors, photo-diodes and photo-transistors, semiconductor-plasma switches, phase-change switches), MEMS switches, piezoelectric switches, ferroelectric switches, gas-plasma switches, electromagnetic relays, thermal switches, etc. For example, semiconductor plasma switches have been used in antennas described in <CIT>. A specific example of an antenna in which the geometry of the scattering elements is controllably varied by semiconductor plasma switches is disclosed <CIT>. Another example of a currently-available electronically-controlled steerable beam antenna using switchable antenna elements (scatterers) is disclosed in <CIT>. Another example of a steerable beam antenna is disclosed in <CIT>.

Another example of a steerable beam antenna is disclosed in <CIT>. Another example of a steerable beam antenna is disclosed in <CIT>.

US Patent <CIT> is assigned to the assignee of this disclosure. That patent discloses an electronically-controlled steerable beam antenna, of the general type described above, comprising a feed line or transmission line defining an axis x; and first and second arrays of electronically-controlled switchable scatters distributed along the axis x, each of the scatterers in the first and second arrays being switchable between a "high" scattering state and a "low" scattering state to scatter an electromagnetic wave propagating through the feed line so as to form a steerable antenna beam.

More specifically, in the antenna disclosed in the above-mentioned '<NUM> patent, the scatterers of the first array are configured to scatter an electromagnetic wave propagating through the feed line. The high-state scatterers in the first array follow a quasi-periodic pattern with an average period P = nd, where n is the number of scatterers per period (including both low-state scatterers and high-state scatterers), and where d is the spacing between adjacent scatterers along the axis x. The high-state scatterers in the second array follow the similar quasi-periodic pattern, with the same average period P, but the pattern of the second array is shifted along the x axis relative to the pattern of the first array.

The antenna beam direction φ is determined by the average period P and the wave phase propagation speed v in the antenna feed line: <MAT> where c is the speed of light, and λ is the free-space wavelength of the beam.

One problem in such steerable beam antennas operating in microwave/millimeter wavelengths is that, as the operational frequency increases, on/off switch-impedance contrast degrades, and scatterer losses increase, due to parasitic capacitances and inductances. Thus, while the above-described antenna of the '<NUM> patent achieves its intended results, it is not optimized for operating at higher millimeter-wave frequencies. Therefore, there is a need for an antenna with the same functionality as the antenna disclosed in the '<NUM> patent, but at higher operational frequencies. Furthermore, it would be advantageous for such an antenna to be compatible with microelectronics mass production techniques.

This disclosure relates to a beam-steering antenna that can be used in areas of imaging radar, communication, concealed weapon detection, landing support devices, collision avoidance systems, etc. More specifically, this disclosure describes a practical implementation of such an antenna that is particularly well-suited to operate at millimeter-wave frequencies and above, although it is not restricted to these frequencies.

In steerable beam antennas in accordance with embodiments of the disclosure, scatterer losses are minimized by providing scatterers that are configured so that they are substantially surrounded by air (a dielectric with minimal dielectric loss), rather than being embedded conductors in a silicon substrate. Furthermore, the scatterer-actuating switches are monolithically integrated into a semiconductor chip as doped regions compactly arranged in the chip, and are directly connected to the antenna scatterers, thereby minimizing switch-scatterer connection losses. In accordance with this disclosure, the switches that actuate the scatterers have three-electrodes configured to allow the switches to operate so as to minimize parasitic influences from the controlling circuit without employing lumped elements that degrade switch operation at high frequencies.

In accordance with aspects of this disclosure, an electronically controlled steerable beam antenna may comprise a base having a planar surface; a plurality of semiconductor antenna chips mounted on the planar surface of the base along a longitudinal axis X; each of the antenna chips defining an upper surface; a ground plane on the upper surface of each of the antenna chips; an array of semiconductor switches arranged longitudinally in each of the antenna chips along the axis X, each of the semiconductor switches comprising a ground electrode, a central electrode, and a control electrode, the control electrode being configured for electrical connection to a control circuit; an array of conductive scattering elements on each of the plurality of antenna chips, wherein each of the conductive scattering elements has a first leg connected to the ground plane and a second leg connected to the central electrode of one of the semiconductor switches; and a linear dielectric element (as a major part of a transmission/feed line) mounted on the plurality of antenna chips along the longitudinal axis X so as to overlie the scattering elements (scatterers), wherein the dielectric element is separated from the array of scattering elements by an air gap.

Other features and aspects of the disclosure will be described in the detailed description below.

<FIG> show a steerable beam antenna <NUM> in accordance with exemplary embodiments of this disclosure. The antenna <NUM> comprises a base <NUM> made of metal or metallized ceramic (or material with similar mechanical and thermal properties). The base <NUM> carries all antenna parts, and it may also advantageously serve as a heat sink. If necessary or advantageous, the base <NUM> may contain heat-dissipation ribs (not shown) on its back side, or coolant channels (not shown) inside its body. A flat central area <NUM> (<FIG>) on one major surface (which may be considered the top surface for the purpose of this disclosure) is configured to accommodate a plurality of semiconductor (e.g., silicon) antenna chips <NUM> (<FIG>) and one or more control boards <NUM> on which are mounted a plurality of control circuits <NUM> (<FIG>), as will be discussed below. An elevated area or plateau <NUM> (<FIG>) is provided adjacent each of the opposite ends of the base <NUM>. The plateaus <NUM> may advantageously be configured to support an antenna cover <NUM> (<FIG>), which may be secured to the base by suitable fasteners (not shown) installed in mounting holes <NUM> (<FIG>). As shown in <FIG> and <FIG>, the cover <NUM> may be formed as two symmetrical longitudinal cover halves, which together form a central wave horn <NUM>, as will be described below.

As shown in <FIG>, the upper surfaces of the chips <NUM> are coplanar with the upper surfaces of the plateaus <NUM>. A metallized layer is advantageously formed on the upper surface of each of the antenna chips <NUM>, as best shown in <FIG>. The metallized layer is divided by inter-chip gaps <NUM> and chip-to-plateau gaps <NUM> to form a ground plane <NUM> on the upper surface of each of the chips <NUM>. <FIG> shows two adjacent antenna chips <NUM> with their respective ground planes separated by an inter-chip gap <NUM>. The ground planes <NUM> are electrically connected across the inter-chip gap <NUM> by conductive links <NUM>, such as wire bonds or wire strips, as shown. Alternatively, the inter-chip gaps <NUM> may be electrically bridged by continuous solder or conductive epoxy. One particularly advantageous type of link may be provided by virtual short circuits, which can be implemented by a ball grid array (BGA) configuration of the type described below.

The antenna <NUM> is connected at each end to an external waveguide flange <NUM> through an impedance-matching transformer <NUM>, only one of which is visible in <FIG> and <FIG>. Mounted on the flat central area <NUM> of the base <NUM> is a plurality of electrical connectors <NUM>, through which DC power and control signals are provided to the plurality of control circuit boards <NUM>, as will be described below.

As shown in <FIG>, <FIG>, and <FIG>, according to aspects of this disclosure, the antenna chips <NUM> may advantageously be attached to the upper planar surface <NUM> of the base <NUM> along a longitudinal axis X using ball-grid arrays (BGAs) <NUM>, preferably one BGA <NUM> per chip <NUM>. The use of the BGAs <NUM> provides a good parallelism between the base <NUM> and the ground planes <NUM>, while providing an even leveling of the chips <NUM> with the plateaus <NUM>. The BGAs <NUM> also provide good thermal conductivity between the antenna chips <NUM> (which are heat sources) and the antenna base <NUM> (which, as mentioned above, may function as a heat sink). The BGAs <NUM> also provide virtual short circuits between the adjacent ground planes <NUM> and between each of the plateaus <NUM> and the adjacent ground planes <NUM>. The virtual short circuits eliminate or minimize parasitic scattering originated in the inter-chip gaps <NUM> (<FIG>) and chip-to-plateau gaps <NUM> (<FIG>). To create virtual short circuits, the BGAs <NUM> should advantageously have the following characteristics:.

The BGAs <NUM> represent photonic band-gap structures preventing wave coupling and propagation under the chips <NUM>. The gaps <NUM> and <NUM>, connected at the chip edges by air-filled spaces between the chips <NUM> and the base <NUM>, function as half-wavelength transmission lines shorted at one end by the corresponding BGA and effectively being shorted (zero voltage and maximal current) at the other end, where the gaps between adjacent ground-plane segments are located.

As shown, for example, in <FIG>, each antenna chip <NUM> carries two integrated linear arrays of mutually mirror-symmetric scatterers <NUM> (metal or metallized), scatterer switches <NUM>, and interface pads <NUM>. Each of the interface pads <NUM> connects one of the switches <NUM> to an appropriate control circuit <NUM> using a wire-bond <NUM>. In the illustrated configuration, the two linear arrays of scatterers <NUM> and scatterer switches <NUM> are arranged longitudinally along either side of the longitudinal central axis X defined by a transmission/feed line comprising a linear dielectric element or "rod" <NUM>, which may be configured as a flat strip of rectangular cross section (as shown), or a rod of any other suitable geometry. The interface pads <NUM> are arranged linearly along each of the opposite longitudinal edges of the antenna chips <NUM>.

As shown in <FIG>, <FIG>, and <FIG>, each scatterer <NUM> may be configured as a Π-shaped conductive element (e.g., metal or metal-plated wire), surrounded by air, so as to minimize dielectric losses, as compared to other materials. As best shown in <FIG>, each scatterer includes a main portion <NUM>, a first leg <NUM> connected to an adjacent portion of the ground plane <NUM>, and a second leg <NUM> connected, via a central contact <NUM>, to a central electrode <NUM> of a corresponding switch <NUM>. Each of the switches <NUM> is located in a switch area or pocket <NUM> formed in a silicon-on-insulator (SOI) device layer <NUM> on the upper chip surface. Each of the switches <NUM> also comprises a ground electrode <NUM> (for which the ground plane <NUM> is the contact), and a control electrode <NUM> connected to an interface pad <NUM> through a metal trace <NUM> formed from a metallized interconnection layer on the chip <NUM>. The device layer <NUM> may advantageously be separated from a handle layer <NUM> by a thin dielectric (e.g., silicon dioxide) layer <NUM>. A dielectric ring <NUM> (e.g., silicon dioxide) isolates each active switch area or pocket <NUM> from the rest of the device layer <NUM> and prevents the carriers injected into the pocket <NUM> from spreading across the device layer <NUM>. The metal traces <NUM> may advantageously be embedded between a first dielectric layer <NUM> and a second dielectric layer <NUM> under the ground plane <NUM>.

As shown in <FIG> and <FIG>, in each switch <NUM>, the ground electrode <NUM> is connected to the ground plane <NUM>, the central electrode <NUM> is connected to the second leg <NUM> of a scatterer <NUM>, and the control electrode <NUM> is connected, via the metal trace <NUM>, to an interface pad <NUM>, and through a wire-bond <NUM>, to an appropriate control circuit <NUM> (<FIG>). (It will be appreciated that each of the control circuits <NUM> may be electrically connected to one or more of the switches <NUM>. ) All three electrodes <NUM>, <NUM>, and <NUM> are formed by doped pockets in the device layer <NUM>. In one control circuit polarity, the control electrode <NUM> is doped by acceptors, the ground electrode <NUM> and the central electrode <NUM> by donors. With an opposite control circuit polarity, the ground electrode <NUM> and the central electrode <NUM> may be doped by acceptors, while the control electrode <NUM> would be doped by donors. <FIG> shows an exemplary geometry of the doped regions forming the ground electrode <NUM>, the central electrode <NUM>, and the control electrode <NUM>.

When the control electrode <NUM> is biased by a corresponding voltage or current from a control circuit <NUM> (<FIG>), electrons and holes are injected into the pocket <NUM> through the electrodes <NUM>, <NUM>, and <NUM>. The injected electron-hole plasma connects the central electrode <NUM> and the ground electrode <NUM>. As the result, the second scatter leg <NUM> is also connected to the ground plane <NUM>, and the scatter <NUM> forms a closed loop (<FIG>). The length of the scatter <NUM> is selected such that the corresponding closed loop resonant frequency is sufficiently different from the frequency of the passing (transmitted or received) wave. Thus, the scatterer <NUM> has a weak effect on the wave, in what may be termed a "low-scatter state. " When the control electrode <NUM> is not biased, the scatterer <NUM> is open-looped (<FIG>), and its resonant frequency is close to the frequency of the passing wave. Therefore, the scatterer <NUM> effectively scatters energy from the passing wave, in what may be defined as a "high-scatter state. " Alternative geometries of the scatterers <NUM> (for example, different lengths) can yield a reversal of the biased/unbiased states, such that a high scatter state is obtained when a scatterer <NUM> is grounded at both ends, and a low scatter state is obtained when the scatterer <NUM> is grounded at only one end. The former arrangement may be preferable, because, in the latter case, a strong RF current through the switch may produce excessive RF losses.

Using linear mirror-symmetric arrays of scatterers <NUM> and switches <NUM>, as shown in <FIG>, is optional. Due to the mirror symmetry, the microwave currents generated in low-scattering scatterers in one array have the same values as the currents generated in low-scattering scatterers in the other array, but in the opposite direction. Therefore, the low-scattering scatterers from both arrays form destructive interference, and the parasitic radiation scattered by the low-scattering scatterers in each of the two arrays is thus effectively annihilated by the parasitic radiation scattered by the low-scattering scatterers in the other array. To prevent annihilation of the radiation scattered by the high-scattering scatterers, the biased/unbiased pattern of one array is advantageously shifted relative to the pattern of the other array by a distance equal to a half-period (PΣ/<NUM>) along the antenna waveguide. Then, due to the additional phase shift, all high-scattering scatterers operate in-phase and form constructive interference. Small relative shifts between two scatterer arrays, such as by a half-space distance s/<NUM>, may provide the benefits of more flexible beam-forming for the antenna and better control of quantization lobes. All antenna components are reciprocal, and the antenna forms the same beam shapes (however, in the opposite directions) when the antenna operates in a transmitting mode and a receiving mode, given the same biased/unbiased switch patterns.

<FIG> illustrate a dielectric element or rod <NUM> of a transmission/feed line, extending along the longitudinal axis X on the upper surfaces of the plurality of antenna chips <NUM> in accordance with an embodiment of this disclosure. In this embodiment, the dielectric element or rod <NUM> is configured as a strip or flattened rod of rectangular cross-section with opposed longitudinal edges mounted on a parallel pair of longitudinal metal spacers <NUM> that are disposed along the opposite longitudinal edges of the ground plane <NUM>, and that extend laterally to the opposite edges of the base <NUM> at each end thereof. The spacers <NUM> allow the dielectric element or rod <NUM> to overlie the scatterers <NUM> without contacting them, with an air space or gap <NUM> defined between the dielectric element or rod <NUM> and the upper surface of the chip <NUM>, as shown in <FIG>. The scatterers <NUM> are thus contained within the air space or gap <NUM>, without contacting the dielectric element or rod <NUM>, which thus overlies the scatterers <NUM> and is spaced from them by air within the air space or gap <NUM>. The object is to situate the scatterers <NUM> with respect to the dielectric rod <NUM> so as to be surrounded by air.

<FIG> illustrates a dielectric element or rod <NUM>' in accordance with another embodiment of the disclosure. In place of the spacers <NUM>, the dielectric element or rod <NUM>' is Π-shaped, comprising a longitudinal strip <NUM> having a pair of downwardly-depending extensions or rails <NUM> extending longitudinally along opposite sides of the strip <NUM>, thereby spacing the strip <NUM> from the upper surface of the chip <NUM> so as to create an air space or gap <NUM>' between the strip <NUM> and the upper surface of the chip <NUM>, with the scatterers <NUM> situated within the air space <NUM>' so as to be separated by air from all parts of the dielectric rod <NUM>', the object again being to situate the scatterers <NUM> so as to be surrounded by air.

<FIG> illustrate that the scatterers <NUM> may optionally be arranged in first and second parallel arrays of scatterers, with the scatterer control switches <NUM> arranged in corresponding first and second parallel switch arrays. Where first and second arrays of scatterers and switches are used, the first arrays of scatterers <NUM> and switches <NUM> are in mirror symmetry with the respective second arrays of scatterers <NUM> and switches <NUM> with respect to a longitudinally-extending plane of symmetry S, as shown in <FIG>. The plane of symmetry S is orthogonal to the surface of the chip <NUM>, and it extends along (that is, includes) the longitudinal axis X.

Microwave energy injected into the antenna <NUM> through the transformers <NUM> (transmitting mode) or coupled out to the external waveguide (receiving mode) (see <FIG>) is channelized (confined) inside a slow-wave waveguide formed by the ground plane <NUM>, the dielectric element or rod <NUM> or <NUM>', the metal spacers <NUM> (in the <FIG> embodiment), the air channel <NUM> or <NUM>', and the cover <NUM> (including the horn <NUM>). The field strength in the air channel <NUM> or <NUM>' around the scatterers <NUM> depends on the thickness of the spacer <NUM> (<FIG> embodiment) or the length of the legs or rails <NUM> of the dielectric strip <NUM>' (<FIG> embodiment). Depending on the corresponding switch state (unbiased or biased), the scatterers <NUM> scatter the propagating wave weakly (biased) or strongly (unbiased). By properly selecting unbiased/biased switch pattern, a coherent beam can be formed with an almost flat phase-front in the required direction.

As shown in <FIG>, the wire-bonds <NUM> electrically connect the antenna chips <NUM> to the control boards <NUM>, which carry control or driver circuits <NUM>, preferably implemented as ICs. In other embodiments, the control circuits <NUM> may be integrated directly into the antenna chips <NUM>. The control or driver circuits <NUM> may be configured as a set of shift-registers, or, alternatively, as FPGAs (Field-Programmable Gate Arrays) or another type of controlling device. The control or driver circuits <NUM>, in turn, are controlled by signals from a controller (not shown), such as a suitably programmed microprocessor, which is connected to the control boards <NUM> through the connectors <NUM>. The controller can also be integrated into one or more of the control circuits <NUM>. The same connectors <NUM> may advantageously be used to provide DC power to the antenna.

The control circuits <NUM> convert a pulse-stream control signal into parallel outputs that bias the required switches <NUM> according to the desired pattern. A typical biased/unbiased switch pattern is periodic or quasi-periodic. The average period PΣ determines the scattered beam direction, <MAT> where NP is the number of periods, and Pi are individual periods.

<FIG> shows a diagram <NUM> representing a fragment of a quasi-periodic pattern of unbiased switches <NUM> and biased switches <NUM> with average period PΣ = <NUM>. <FIG> shows a diagram <NUM> representing a half-average-period (PΣ/<NUM>) shift between the switch patterns of the two mirror-symmetric arrays necessary for proper phasing of high-scattering from both scatterer loop arrays.

<FIG> shows a diagram <NUM> representing how an antenna taper can be achieved through programming patterns of unbiased/biased switches. The average coupling per period can be controlled by varying the number of unbiased switches without changing the total number of switches per period, i.e., without affecting beam direction. In the diagram <NUM>, all unbiased/biased periods consist of eight switches. The number of couplings per period, however, is different and increases from the left period to the right period, as shown in the figure.

As noted above, and as shown in <FIG>, <FIG>, and <FIG>, the antenna <NUM> is advantageously protected by the cover <NUM> that may advantageously be made of two mirror-symmetric metal or metallized halves. Each of the cover halves may be formed with a longitudinal recess <NUM> that accommodates the dielectric element or rod <NUM>. Each of the halves of the cover <NUM> includes a sloped interior surface, whereby the two sloped interior surfaces together define the elongated horn <NUM> that provides signal coupling between the dielectric element or rod <NUM> and the ambient environment. The illustrated configuration of the horn <NUM> is exemplary only, and horns with different profiles, for example, with corrugated or curved walls, may be found advantageous in some applications.

<FIG> shows one of the two tapered end-transitions <NUM> located at the antenna ends. The end-transitions <NUM> function as matching transformers between the antenna body and an external waveguide. The tapered end transitions <NUM>, along with advantageously-provided tapered features <NUM> and <NUM>, smoothly transforms the principal antenna mode propagating along the dielectric element or rod <NUM> (or <NUM>') to the mode propagating in a rectangular external metal waveguide <NUM> at each end of the antenna. Each tapered end-transition <NUM> defines an air cavity or void <NUM>, which includes a portion defining a cavity for the dielectric element rod <NUM> (or <NUM>'), a portion defining a cavity for a matching transformer <NUM>, and a portion defining a cavity for the external metal waveguide <NUM>. The antenna end construction restricts motion of the dielectric element or rod <NUM> in all directions. Therefore, the dielectric element or rod <NUM> can be installed in the antenna without the use of an adhesive, which could introduce substantial losses at high frequencies.

Low return losses (VSWR) across a designated scanning range, as may be provided by the end-transition <NUM>, are illustrated graphically in <FIG>, which represents the results of high frequency structure simulator (HFSS).

<FIG> illustrates an antenna <NUM>' that employs a dielectric element or rod <NUM>' in accordance with the embodiment of <FIG>. Thus, as illustrated, the antenna <NUM>' lacks the spacers <NUM> that provides an air gap or channel for the dielectric element or rod <NUM>', instead using the Π-shaped dielectric element or rod <NUM>' of <FIG> to create the air channel <NUM>' in which the arrays of scatterers <NUM> are situated. As in the previously-described embodiments, the antenna <NUM>' includes a cover <NUM>' formed of two longitudinal cover halves, each with a sloped interior surface, whereby the sloped surfaces together define a horn <NUM>'. As shown, each of the cover halves includes a longitudinal recess <NUM>' that accommodates the dielectric element <NUM>'. In accordance with this embodiment, control or driver circuits <NUM>' are mounted directly onto the antenna chips <NUM>, using, for example, ball grid arrays (not shown), and the control circuit boards <NUM> shown in <FIG> may therefore be omitted. Each of the cover halves may, in some embodiments, include longitudinal choke channels (not shown) to help to confine the propagating wave inside the waveguide formed by the dielectric element <NUM> and the cover <NUM>', and to prevent leakage through optional air gaps (not shown) between the cover <NUM> and the ground planes <NUM>.

From the foregoing description of the structure of a steerable beam antenna in accordance with aspects and embodiments of the disclosure, a method of making an antenna in accordance with this disclosure may include the steps of (a) providing a semiconductor wafer having an upper surface; (b) doping the semiconductor wafer to form a plurality of embedded semiconductor switches, each of the semiconductor switches comprising a ground electrode, a central electrode, and a control electrode; (c) forming an interconnection layer on the semiconductor wafer, wherein the interconnection layer comprises metal traces configured for connecting the control electrode of each of the semiconductor switches with a corresponding control circuit; (d) metallizing the top surface of the semiconductor wafer to form a ground plane, wherein the ground plane is electrically connected to the ground electrode of each of the semiconductor switches; (e) forming a plurality of conductive scatterers on the semiconductor wafer, wherein each of the conductive scatterers electrically connects the central electrode of one of the semiconductor switches to the ground plane, and wherein each of the conductive scatterers has a main portion spaced from the upper surface of the semiconductor wafer; (f) dicing the wafer into a plurality of antenna chips, each of the antenna chips including an array of semiconductor switches and an array of conductive scatterers; (g) installing the plurality of antenna chips onto a base using a ball-grid array for each of the antenna chips; (h) electrically interconnecting each of the installed antenna chips; (i) installing a dielectric element onto the antenna base so as to overlie the array of conductive scatterers on each of the antenna chips, wherein an air gap is provided between the dielectric element and the arrays of conductive scatterers; (j) installing a conductive cover on the base so as to provide a waveguide with the dielectric element; and (k) installing a plurality of control circuits on the base and electrically connecting each of the control circuits to the semiconductor switches in at least one of antenna chips. The step of mounting the chips on the base preferably includes mounting the chips using a ball grid array on each of the chips.

In accordance with one exemplary embodiment of an antenna design in accordance with aspects of this disclosure, a dielectric element or rod <NUM> with dimensions <NUM>λ × <NUM>λ × <NUM>. 11λ is preferably made out of quartz, where λ is the average operational wavelength. The antenna chips <NUM> are preferably made of SOI wafer with a <NUM> µm-thick device layer separated from the handle layer by <NUM> µm-thick silicon oxide. The isolated switch pockets <NUM>, with dimensions <NUM> µm × <NUM> µm × <NUM> µm, are formed in the device layer by deep-trench etching with consecutive planarization, as is well-known in the art. The switch electrodes are preferably made by phosphorous and boron ion implantation with consecutive annealing, and they have a resistivity below <NUM>.

The scatterers <NUM>, ~<NUM>λ long, are preferably made as wire bonds. Two scatterer arrays <NUM> are separated by the distance of ~<NUM>λ. Spacing between the adjacent scatterers in the same array along the dielectric feed <NUM> is ~<NUM>λ.

The ball diameter in the ball-grid arrays <NUM> is <NUM> mm, with a ball spacing of ~<NUM>λ. The antenna chips <NUM> are placed on the base surface <NUM> at a distance ~<NUM> mm from each other and from the platforms <NUM>.

The simulated antenna beam patterns for the above-described exemplary embodiment are shown in <FIG>. The average unbiased/biased switch pattern period PΣ varies between approximately <NUM>s and approximately <NUM>s, where s is the spacing between the adjacent scatterers in the same array. The corresponding scanning angles shown in the graph cover a sector from about -<NUM>° through about +<NUM>° in the direction toward a single antenna feed point at one end. If the antenna is also fed from a second feed point at the other end, the covered sector will increase correspondingly.

If the unbiased/biased switch patterns can be represented by overlapping patterns with different periods, the antenna generates multiple beams corresponding to the number of the different periods, which can be controlled independently from each other.

For all simulated beam positions excluding <NUM>° and vicinities, the antenna is characterized by low return loss (VSWR < <NUM>) and high radiation efficiency (exceeding <NUM>%-<NUM>%). At the scanning angle <NUM>° and nearby, the Bragg reflection essentially increases the return loss. To minimize the return loss and maximize the antenna radiation efficiency at the Bragg angles, the relative shift between the unbiased/biased switch patterns in the two mirror-symmetric arrays should be optimized by changing it from PΣ/<NUM> to <NUM>PΣ.

Claim 1:
An electronically controlled steerable beam antenna (<NUM>), comprising;
a base (<NUM>) having a planar surface;
a plurality of semiconductor antenna chips (<NUM>) mounted on the planar surface of the base along a longitudinal axis X, each of the antenna chips (<NUM>) defining an upper surface;
a ground plane on the upper surface of each of the antenna chips (<NUM>);
an array of semiconductor switches arranged longitudinally in each of the antenna chips, each of the semiconductor switches comprising a ground electrode (<NUM>), a central electrode (<NUM>), and a control electrode (<NUM>), the control electrode (<NUM>) being configured for electrical connection to a control circuit;
an array of conductive scattering elements on each of the plurality of antenna chips, wherein each of the conductive scattering elements comprises a first leg connected to the ground plane, a second leg connected to the central electrode of an associated one of the semiconductor switches, and a main portion extending between the first leg and the second leg, wherein at least the main portion is surrounded by air; and
a linear dielectric element mounted on the plurality of antenna chips along the longitudinal axis X above the conductive scattering elements, and spaced by an air gap from the conductive scattering elements.