Patent Description:
In a point-to-point wireless communications link, it is desirable to "peak" the receive side antenna beam (a first antenna's beam) with respect to the transmit side beam (a second antenna's beam) to maximize the receive signal strength and quality. In other words, it is beneficial to spatially align the peak of a "receive beam" formed based on the receiving antenna characteristics with the peak of the transmit side beam. One prominent example is in satellite signal communications in which a residential reflector antenna receives a satellite signal broadcast. In high frequency bands, such as in Ka band, the reflector antenna forms a narrow beam, e.g., having a 3dB beamwidth of <NUM>° or less, such that small beam mispointing errors can lead to significant signal loss. Such mispointing errors may occur upon initial use of the reflector antenna due to imperfect installation, and/or during later use of the reflector antenna, e.g., due to mechanical shifting of the feed illuminating the reflector, as a function of environmental conditions.

One approach to the fine tuning of the beam peak position employs a control system to mechanically tilt the reflector antenna's feed according to a predetermined sequence until a requisite signal metric is met. However, this type of system adds to the antenna complexity and may be prone to mechanical failure when environmental conditions change. <CIT> discloses a dielectric lens comprising an antenna array feed assembly. The array is used to determine the best signal strength of a signal. The method consists of switching between subarrays of antenna elements in order to determine which subarray of elements has the best signal strength. <CIT> discloses a reflector antenna comprising a feed in the form of a phased array. The antenna is mechanically moved for coarse tuning. The fine tuning is done using the phased array.

In an aspect of the present disclosure, a method for adjusting a pointing direction of an antenna beam involves forming a beam with a reflector antenna including a reflector and a feed, the feed including an array of N antenna elements, by activating a first set of antenna elements among the N antenna elements. A signal metric of a signal communicated via the beam is measured. In an iterative fashion, a pointing direction of the beam is adjusted at least in part by activating a different set of antenna elements among the N antenna elements, and the signal metric is re-measured with each iterative adjustment. A final pointing direction and associated final set of antenna elements are selected for operation of the reflector antenna based on the signal metric measurements.

In another aspect, a reflector antenna includes: a reflector and a feed including an array of N antenna elements, the feed being positioned to illuminate the reflector; a combiner/divider coupled between the N antenna elements and an input/output port of the antenna system; signal metric measurement circuitry; and a controller. The controller cooperates with the signal metric measurement circuitry to perform the operations delineated above to iteratively adjust the pointing direction of the beam by, in turn, activating different sets of antenna elements among the N antenna elements and measure the signal metric, and thereafter select a final set of antenna elements for operation of the reflector antenna based on the signal metric measurements.

The above and other aspects and features of the disclosed technology will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings in which like reference characters indicate like elements or features. Various elements of the same or similar type may be distinguished by annexing the reference label with an underscore / dash and second label that distinguishes among the same / similar elements (e.g., _1, _2), or directly annexing the reference label with a second label. However, if a given description uses only the first reference label, it is applicable to any one of the same / similar elements having the same first reference label irrespective of the second label. Elements and features may not be drawn to scale in the drawings.

The following description, with reference to the accompanying drawings, is provided to assist in a comprehensive understanding of certain exemplary embodiments of the technology disclosed herein for illustrative purposes. The description includes various specific details to assist a person of ordinary skill in the art with understanding the technology, but these details are to be regarded as merely illustrative. For the purposes of simplicity and clarity, descriptions of well-known functions and constructions may be omitted when their inclusion may obscure appreciation of the technology by a person of ordinary skill in the art.

Herein, the phrase "communicating signals" (or like forms) encompasses unidirectional and bidirectional communication. Thus, when a first device communicates signals with a second device, the first device transmits signals to and/or receives signals from the second device.

Herein, the phrase "combining / dividing" or like forms means combining and/or dividing.

Herein, the slash symbol " / " connecting two items signifies and/or ("and" or "or"), unless the context indicates otherwise. In other words, both items are present in one example, but only one of the items is present in another example.

<FIG> is a perspective view of an array-fed reflector antenna assembly, <NUM>, according to an embodiment (hereafter, "reflector antenna" or just "antenna" <NUM>). Antenna <NUM> includes a reflector <NUM> such as a parabolic reflector, which may be center-fed or offset-fed by an array feed <NUM>. Array feed <NUM> includes an antenna array <NUM> and a circuit assembly <NUM> containing at least RF front-end electronics, disposed behind antenna array <NUM>. Array feed <NUM> may be fixedly coupled to reflector <NUM> via a support boom <NUM>. A mounting bracket assembly <NUM> may be coupled between reflector <NUM> and a support pier <NUM>. Support pier <NUM> may fixedly mount reflector antenna <NUM> to a surface such as a roof or an exterior wall of a building or other terrestrial structure.

Array feed <NUM> is positioned in or near the focal plane of the reflector and oriented in relation to reflector <NUM> such that antenna <NUM> produces a beam for communication (transmit, receive, or transmit and receive) with an intended target such as a satellite. In a typical embodiment, a central point of array feed <NUM> is positioned at or near the focal point of reflector <NUM>. In examples in which the communication includes transmit and receive, the "beam" formed by antenna <NUM> may be considered to include a "receive beam" (used to receive a first signal from the target) and a "transmit beam" (used to transmit a second signal to the target). However, if different respective frequencies or polarizations are used for uplink signals (transmitted from antenna <NUM>) and downlink signals (received by antenna <NUM>), the receive beam may differ slightly from the transmit beam in terms of beamwidth and pointing direction.

In some embodiments, antenna <NUM> is a user terminal antenna assembly for residential use, configured to communicate signals with one or more satellites at microwave / millimeter wave frequencies. As such, antenna <NUM> may form a narrow pencil (rotationally symmetric) beam, e.g., with a 3dB beamwidth under <NUM>° in some embodiments. Thus, small antenna beam pointing errors may lead to significant signal loss.

Mounting bracket assembly <NUM> may be used to coarsely point the beam at the intended target. During the coarse pointing an initial set of antenna elements may be activated and a signal metric measured to assist in the coarse pointing. Mounting bracket assembly <NUM> may include bolts that can be loosened to permit antenna assembly <NUM> to be moved in azimuth, elevation and skew. For example, an installer may determine an approximate elevation angle of a mounting surface to which support pier <NUM> is mounted. The installer may also know the approximate direction of the intended target with respect to the installation location based on predetermined information and/or signal measurements at the site. The installer may then manipulate mounting bracket assembly <NUM> in azimuth / elevation / skew to coarsely point the beam at the target and then secure the mounting bracket assembly <NUM>. In the process of the coarse pointing of the antenna beam, all the antenna elements of array <NUM> of feed <NUM> are activated, or only a subset of the antenna elements of array <NUM> of feed <NUM> located near focal point <NUM> (F) of the reflector is activated.

<FIG> illustrates examples of different "activatable" subsets of antenna elements, <NUM> and <NUM>, within the array <NUM> of feed <NUM>, and respective pointing directions of beams they may produce. In a typical embodiment, only some of the antenna elements of array <NUM> are activated at any given time; each set of activated antenna elements may therefore be referred to as a subset of antenna elements. At least some of the antenna elements of array <NUM> may be individually activatable, i.e., selectively activated and deactivated. An "activated" antenna element is an antenna element that operates normally in an array and is not "shut off" by an effective opening of a switching element in a signal path coupled to the antenna element. (An amplifier is one example of the switching element. When bias is applied normally, the switching element is turned on; when bias is removed, the switching element is off. ) In other words, an activated antenna element contributes to forming a beam of the antenna, while a deactivated antenna element is precluded from contributing to forming the beam. Thus, an activated antenna element transmits signal energy in the transmit direction and/or receives signal energy in the receive direction that contributes to a composite receive signal received by antenna <NUM>. A switching element within a signal path coupled to a respective antenna element of array <NUM> may be on-off controlled by a controller located within circuit assembly <NUM> or elsewhere. When the switching element is turned on (closed), the signal path is closed, whereby the antenna element is activated and operates normally, contributing to the formation of the overall beam of antenna <NUM>. In other words, the activated antenna element is part of an active, beam forming subset of array <NUM>. When the switching element is opened, the antenna element is deactivated and no longer part of an active subset, and does not contribute to forming the beam (with the exception of a possible slight impact on the beam's gain and pattern due to any parasitic excitation, reflections causing mismatch, etc.).

As noted above, an amplifier is one example of the switching element. Another example of the switching element is a series connected switch. Alternatively, an array element can be effectively "shut off" by reducing the amplitude of the RF signal fed into the element to an effectively negligible level, such as -<NUM> dB compared to the most-activated elements in the array. This may be done by embodying the switching element as either a variable attenuator or a modulation modifier.

Thus, an activated antenna element transmits signal energy in the transmit direction and/or receives signal energy in the receive direction that contributes to a composite receive signal received by antenna <NUM>. A switch within a signal path coupled to a respective antenna element of array <NUM> may be on-off controlled by a controller located within circuit assembly <NUM> or elsewhere. When the switch is turned on (closed) or the amplitude of the RF signal fed into the element is reduced to an effectively negligible level, the signal path is closed, whereby the antenna element is activated and operates normally, contributing to the formation of the overall beam of antenna <NUM>. In other words, the activated antenna element is part of an active, beam forming subset of array <NUM>. When the switch is opened or the amplitude of the RF signal fed into the element is above an effectively negligible level, the antenna element is deactivated and no longer part of an active subset, and does not contribute to forming the beam (with the exception of a possible slight impact on the beam's gain and pattern due to mutual electromagnetic coupling-induced parasitic excitation, reflections causing mismatch, etc.).

The above-mentioned controller functions as an "auto-peak device" that electronically adjusts the antenna beam pointing direction (the direction of the beam peak of the overall antenna, i.e., including the reflector) without the need for mechanical adjustment. The controller selects the subset of antenna elements in order to point and fine-tune the pointing of the beam as described herein. In other words, the switching elements (and optionally, other circuitry within circuit assembly <NUM>) are responsive to control signals from the controller to activate the selected subset of the antenna elements. In doing so, the beam can be pointed and scanned for ease of installation and peaking during service. Notably, the fine tune pointing of the beam is fully-electronic, as no mechanical movement is required or performed in a typical embodiment.

As illustrated in <FIG>, using the above-discussed switching scheme, different sets of antenna elements among the antenna elements of array <NUM> may be activated at different times to form beams that point in different directions. In this example, overlapping subsets <NUM> and <NUM> may be activated at different times to form beams that point in different directions <NUM> and <NUM>, respectively. The center of the selected subset defines the direction of the beam. Thus, first selecting a first subset will point the beam in a first direction, and thereafter selecting a second subset will steer the beam from the first direction to a second direction.

When antenna <NUM> is first set up at a time of installation, a signal metric such as signal strength may be measured for each of a plurality of pointing directions of the beam formed with different respective sets of antenna elements in an iterative sequence. Based on the signal metric measurements, a final pointing direction and associated final set of antenna elements, typically with an optimized signal metric, may be selected for subsequent operation of antenna <NUM>. These operations may be herein referred to as "auto-peaking". Similar auto-peaking operations may be performed during the service life of antenna <NUM>. For instance, auto-peaking may be performed periodically or may be triggered by an event such as the signal metric falling below a threshold. (It is noted here that for circularly polarized systems, a first set of antenna elements may form a first beam - such as the transmit beam - and when the sequence switches over to a second set of antenna elements, this may form a second beam - such as a receive beam - with a different pointing angle, which may be equivalent to adjusting the pointing direction of the first beam. This would allow to eliminate the circular polarization-induced beam squint inherently present in all offset-fed reflector antennas.

In general, the far-field antenna pattern of the beam generated by antenna <NUM> can be understood as a Fourier transform of the electric field distribution (amplitude and phase) across the aperture of the reflector <NUM> The electric field distribution is due to the induced electric currents on the surface of the reflector <NUM> and may be correlated with the electric field of the "feed beam" pattern (the feed "illumination pattern", which may or may not be a near-field illumination) incident across the reflector <NUM> surface. Thus, with knowledge of the feed beam pattern of a subset and the position of the subset with respect to reflector <NUM>, the far-field radiation pattern of the overall antenna <NUM> may be computed, and candidate subsets may be determined.

Intuitively, relative pointing directions of beams generated using coplanarly shifted sets of antenna elements within array <NUM> may be understood as follows: For the case of an offset-fed reflector antenna, reflector <NUM> may be an asymmetrically-cut segment of a paraboloidal surface. (This is in contrast with center-fed reflector antennas, whose reflectors are cut symmetrically about the symmetry axis of the paraboloid. ) Array <NUM> may be positioned with respect to reflector <NUM> such that a center point <NUM> of array <NUM> is located at the focal point F of reflector <NUM>. A normal N1 to the planar surface of array <NUM>, drawn from center point <NUM>, may intersect reflector <NUM> at a central point of the projected aperture of reflector <NUM>.

Referring momentarily to <FIG> and <FIG>, another example subset ("cluster") <NUM> of antenna elements is composed of antenna elements of array <NUM> substantially symmetric about point <NUM>. If these are activated, the resultant beam may point in a direction N2, which may coincide with a central axis of reflector <NUM>. This may be understood intuitively by equating the activated portion of array <NUM> as a single collective source substantially symmetric about the focal point F and radiating - i.e., projecting rays - towards reflector <NUM>. With the collective source grouped about focal point F, all rays incident upon reflector <NUM> are reflected from the reflector in a mutually parallel manner, i.e., collimated, in a direction parallel to direction N2. By definition, in a collimated beam, the phase front of the electromagnetic wave is planar and perpendicular to the rays reflected from reflector <NUM>. Further, the "feed beam", i.e., the spatially combined radiated power of subset <NUM>, may produce a substantially symmetrical amplitude distribution (electric field strength) across the aperture of reflector <NUM>, which may in turn produce a rotationally symmetrical (pencil) beam from reflector <NUM>. In order for the spatial combination of the power radiated by two or more radiating sources to take place, the following four conditions may be met simultaneously: (<NUM>) The radiating sources are located near one another in space; (<NUM>) the radiating sources are radiating at the same time; (<NUM>) the radiating sources are operating at the same, or almost the same (i.e., not orthogonal), frequencies; and (<NUM>) the radiating sources are radiating electromagnetic waves of the same polarization.

On the other hand, when subset ("cluster") <NUM>, whose center point <NUM> is displaced from the focal point F, is activated, subset <NUM> may be approximated as a collective source laterally shifted (in the plane of array <NUM>) from focal point F. Due to the spatial combination of the power radiated by the individual elements of subset <NUM>, this displaced collective source behaves as a single common antenna feed, such as a feed horn. The feed beam rays are incident upon the reflector <NUM> surface points at incident angles differing from the case above. Rays from subset <NUM> are therefore reflected from the surface of reflector <NUM> substantially collimated and in a direction non-parallel to direction N2. This produces an overall antenna beam with a peak direction <NUM> skewed from direction N2. In other words, the phase front of the electromagnetic wave reflected from the reflector is substantially planar and perpendicular to direction <NUM>. Likewise, subset <NUM> with center point <NUM> is offset from the center point <NUM> on the opposite side with respect to subset <NUM> and may project a feed beam in direction <NUM> on the opposite side of normal N1, whereby antenna <NUM> produces a beam pointing in direction <NUM>. (It is noted here that subsets <NUM> and <NUM> overlap in the example of <FIG> but do not overlap in the example of <FIG>. The above discussion applies to both cases.

In other embodiments, the center point <NUM> of array <NUM> is slightly offset from the focal point F. In still other embodiments, a center-fed reflector system is implemented, but has the drawback of the reflector aperture blockage by the feed and the feed support, which may lead to higher sidelobes and lower gain. With a center-fed reflector embodiment, similar beam pointing adjustments to those described herein may be made by selectively activating different sets of antenna elements within the array feed.

As discussed above, a selected set of antenna elements among array <NUM> is, in some embodiments, a subset of the antenna elements of array <NUM>. Thus, array <NUM> may be considered an "oversized feed". When antenna <NUM> operates with just a subset of array <NUM>, antenna <NUM> may be considered a "thinned array-fed reflector".

For a reflector <NUM> with a generally large F/D (focal length to aperture size), changing the angle between the center of the reflector <NUM> and the center of the selected subarray (the set or subset of antenna elements, e.g., subset <NUM>) can result in the same or similar change in the angle of beam steering. In one example, changing the selected subarray so that its center is about <NUM> offset from the previously selected subarray can provide a <NUM> degrees scan.

It is further noted that in the examples herein, a single beam antenna is described. In other embodiments, multiple simultaneous beams may be formed using the same techniques described herein. Each of the simultaneous beams may have its pointing direction optimized by iteratively selectively activating subsets of array <NUM> associated with that beam, measuring a signal metric for each of the activated subsets, and selecting a final subset having the best performance.

<FIG> shows examples of activatable subsets of antenna elements within the reflector feed array <NUM>. Array <NUM> is exemplified as a planar array of N antenna elements, 70_1 to 70_N arranged to approximate a circular profile <NUM>. Subsets <NUM> and <NUM> are exemplified as equal-sized, overlapping subsets approximating circular profiles <NUM> and <NUM>, respectively. Subset <NUM> has a center point <NUM> offset to the left of the array <NUM> center point <NUM>, and includes antenna elements 70_1 to 70_M. Subset <NUM> has a center point <NUM> offset to the right of center point <NUM>, and may include an equal number of antenna elements 70_K to 70_N (where (N-K) equals (M-<NUM>)). Antenna elements <NUM> may be any suitable type of antenna element such as a microstrip patch element, a dipole, a slot, or an open ended waveguide. Centrally located antenna elements 70_K to 70_M are shared by subsets <NUM> and <NUM>.

When the antenna elements of subset <NUM> are activated to form a beam just using subset <NUM>, all remaining elements of array <NUM> are deactivated. Likewise, when the antenna elements of subset <NUM> are activated to form a beam just using subset <NUM>, all remaining elements of array <NUM> are deactivated. Thus, in an iterative process to steer a beam and concurrently measure a signal metric, the antenna elements within differing peripheral regions of array <NUM> may be sequentially deactivated during a sequential activation of predetermined subsets.

<FIG> depicts further examples of activatable subsets of antenna elements within the reflector feed array <NUM>. Subsets <NUM> and <NUM> with circular profiles have center points <NUM> and <NUM> offset to the top and bottom of array <NUM>'s center point <NUM>, respectively. Subset <NUM> includes antenna elements 70_W to 70_Y arranged in a circular profile; subset <NUM> includes an equal number of circularly arranged antenna elements 70_X to 70_Z, where elements 70_X to 70_Y are shared between subsets <NUM> and <NUM>. Subsets <NUM> and <NUM> may each have an equal number of antenna elements as those of subsets <NUM> and <NUM>. Additional activatable subsets interpolated between those of subsets <NUM>-<NUM> may be similarly formed. Further activatable subsets may include a central subset (e.g., circular and the same size as subsets <NUM>-<NUM>) symmetrical about the array <NUM>'s center point <NUM>; and additional subsets incrementally formed between the central subset and any other subset that extends to an edge of array <NUM>, such as any of subsets <NUM>-<NUM>. Subsets of different sizes within array <NUM> may also be formed. As mentioned earlier, <FIG> is an example showing a centrally arranged subset <NUM> that overlaps smaller aperture versions of subsets <NUM> and <NUM> (the example subsets <NUM> and <NUM> do not overlap in <FIG>).

An advantage of using generally circular subsets of antenna elements as described above in conjunction with reflector <NUM> having a circular profile is that the feed illumination pattern from a circular aperture is generally the same in any direction across the diameter. Alternatively, feeds and subsets of different shapes, e.g., square, rectangular or oval, may be substituted. In another embodiment, array <NUM> is configured as a single linear array or a set of crossed linear arrays. Reflector <NUM> may alternatively have an oval or other shaped profile.

<FIG> schematically illustrates example components of antenna feed <NUM>. Antenna feed <NUM> may include antenna elements 70_1 to 70_N; an N:<NUM> combiner / divider <NUM>; RF front end elements (FEEs) 90_1 to 90_N; a controller <NUM>; signal metric measurement circuitry (SMMC) <NUM>, a coupler <NUM> and memory <NUM>.

Combiner/divider <NUM> is configured to divide and/or combine signals, depending on whether antenna <NUM> is configured as a transmitting antenna system, a receiving antenna system, or both a transmitting and receiving antenna system. In the transmit direction, combiner/divider <NUM> divides an input RF transmit (uplink) signal at an RF input/output (I/O) port <NUM> into N divided transmit signals provided at transmission lines 96_1 to 96_N. The transmit signals are routed through selected ones of FEEs <NUM> and antenna elements <NUM> to generate an uplink signal SU which is transmitted to a target device, e.g., a satellite <NUM>. (Note that the outputs of FEEs <NUM> may be electrically connected to respective antenna elements <NUM>. Alternatively, FEEs <NUM> are electromagnetically (EM) coupled to respective antenna elements <NUM> via a suitable EM excitation mechanism. ) In the receive direction, combiner/divider <NUM> combines up to N "element signals" received by antenna elements <NUM>, each derived from a downlink signal SD from target device <NUM>, and provides a combined signal at I/O port <NUM>. Some examples of satellite <NUM> include a low earth orbit (LEO) satellite, a medium earth orbit (MEO) satellite, a geosynchronous equatorial orbit (GEO) satellite, or an elliptical orbit satellite.

Combiner/divider <NUM>, transmission lines <NUM>, and FEEs <NUM> collectively form a feed network of feed <NUM>. Each FEE 90_i (i = any of <NUM> through N) may include a switching element (e.g., an amplifier or a series connected switch, described below) controlled by controller <NUM> to activate/deactivate an associated antenna element 70_i. In this manner, candidate subsets of antenna elements are selectively activated. For instance, in the example illustrated in <FIG>, subset <NUM> of <FIG> may be activated by closing the switching elements in FEEs 90_1 to 90_M and thereby activating antenna elements 70_1 to 70_M, and opening the remaining switching elements (e.g., in FEE 90_N, etc.) coupled to the remaining antenna elements <NUM>. On the other hand, <FIG> shows switching states of switching elements in an example for activating subset <NUM>, by closing the switching elements in FEEs 96_K to 96_N to thereby activate antenna elements 70_K to 70_N, and opening the switching elements in the FEEs coupled to the remaining antenna elements <NUM>. In the receive direction, when a subset having M elements is activated, N:<NUM> combiner/divider <NUM> effectively acts as an M:<NUM> combiner, since there are no element signals incident upon the output ports that are not coupled to any of the M elements.

It is further noted here that in an exemplary embodiment, the feed network composed of combiner/divider <NUM>, transmission lines <NUM> and FEEs <NUM> are configured to "drive" antenna elements <NUM> in a fixed phase relationship among the antenna elements for each of the candidate subsets, which is typically an in-phase relationship. In some embodiments, the fixed phase relationship is achieved by having the electrical length (or insertion phase) of a signal path from port <NUM> to antenna element 70_1 be the same as the electrical length from port <NUM> to any of the other antenna elements, such that all of the antenna elements are driven in phase. (Here, "drive" applies to both the transmit and receive directions. ) When the antenna elements of any subset are driven in phase, a pencil beam should be formed with a pointing direction (and beam peak) aligned with a normal to the plane of the subset (more precisely, the pointing direction should be aligned with a normal to a center point of the subset).

On the other hand, other embodiments may implement a built in phase gradient across the aperture if desired, in which case the fixed phase relationship is not an equal phase relationship. Still other embodiments employ phase shifters within the FEEs <NUM> or elsewhere (e.g., within combiner/divider <NUM>) to enable dynamic steering of the feed beam and hence the antenna <NUM> beam to enable further fine tuning of the pointing direction. This approach, however, adds to the complexity and cost of the feed <NUM>. Embodiments that omit phase shifters have a manufacturing and cost advantage over those employing phase shifters.

Coupler <NUM> may couple receive path signal energy to signal metric measurement circuitry (SMMC) <NUM> to allow SMMC <NUM> to measure a signal metric, typically signal strength, signal to noise ratio (SNR), signal to interference and noise (SINR) or any combination thereof. (Other examples include Energy per bit / Noise-spectral density (EbNo), Energy per symbol / Noise-spectral density (EsNo), Error Vector Magnitude (EVM), Bit Error Rate (BER), or any combination thereof. ) SMMC <NUM> may provide the signal metric measurement result to controller <NUM>. As discussed later, controller <NUM> may base a decision to select one of the candidate subsets as a final subset of antenna elements for subsequent operations of antenna <NUM>. Controller <NUM> may include at least one processor that reads and executes program instructions from memory <NUM> coupled thereto to carry out its operations. Memory <NUM> may also store the signal metric measurement results. As noted earlier, controller <NUM> may be disposed within circuit assembly <NUM> in close proximity to antenna array <NUM>, but is alternatively disposed elsewhere within reflector antenna <NUM>, or is disposed remotely. In either of these cases, controller <NUM> may be considered a component of feed <NUM>.

<FIG> depict respective examples of front end elements (FEEs) in antenna feed <NUM>. Each example shows an FEE that may be used for any of FEEs 90_1 to 90_N. <FIG> shows a receive path example for a case in which antenna <NUM> is a receiving antenna system, or, antenna array <NUM> is an interleaved transmitting and receiving array (described below in connection with <FIG>). Here, an FEE 90a_i includes a low noise amplifier (LNA) <NUM> serving as the FEE switching element. LNA <NUM> is coupled between an antenna element 70_i and a transmission line 96_i. To turn the switching element of FEE 90a_i on and thereby activate antenna element 70_i, a bias voltage is supplied by controller <NUM> to LNA <NUM> on control line 92_i, enabling LNA <NUM> to function normally to amplify an element signal provided by antenna element 70_i. To deactivate antenna element 70_i, the bias voltage is withdrawn by controller <NUM> in a manner sufficient to turn off LNA <NUM>. The bias voltage may be withdrawn either by floating control line 92_i open or tying control line 92_i to a different voltage, e.g., a ground voltage, sufficient to turn off LNA <NUM>. As a result, the element signal does not pass to transmission line 96_i. Accordingly, LNA <NUM> is controlled to have a dual function as both an amplifier and a switch (i.e., an antenna element activation/deactivation switch).

<FIG> shows a transmit path example for the case in which in which antenna <NUM> is a transmitting antenna system, or, antenna array <NUM> is an interleaved transmitting and receiving array. Here, an FEE 90b_i includes a power amplifier (PA) <NUM> serving as the FEE switching element. PA <NUM> is coupled between antenna element 70_i and transmission line 96_i, that is on-off controlled by supplying / withdrawing a bias voltage in the same way as described above for LNA <NUM>. When PA <NUM> is normally biased, a transmit signal on line 96_i is amplified and routed to antenna element 70_i, and when PA <NUM> is turned off by withdrawing the bias voltage, the transmit signal does not pass to antenna element 70_i.

<FIG> shows a transmit path or receive path example in which an FEE 90c_i is embodied as an in-line switch <NUM> such as a PIN diode switch coupled between antenna element 70_i and transmission line 96_i. Switch <NUM> is switched on (closed) by an on-voltage supplied on line 92_i to thereby activate antenna element 70_i. Switch <NUM> is switched off (opened) by an off-voltage on line 92_i to deactivate antenna element 70_i. Another example of switch <NUM> is a variable attenuator controllable, e.g., to have attenuation in the range of ~0dB to 20dB. Still another example of switch <NUM> is a modulation modifier that may, e.g., provide variable attenuation in the range of ~0dB to 20dB.

<FIG> shows a transmit and receive path example in which an FEE 90d_i includes a PA <NUM> and an LNA <NUM> connected in parallel between first and second diplexers 112_1 and 112_2, which enables both transmit path and receive path signals to flow between antenna element 70_i and transmission line 96_i simultaneously. Control lines 92_i in this case may include a first control line supplying a first bias voltage to PA <NUM> and a second control line supplying a second bias voltage to LNA <NUM>. The first and second bias voltages may be concurrently supplied to activate antenna element 70_i in a subset of antenna elements allocated for both transmit and receive operations. The first and second bias voltages may be concurrently withdrawn to deactivate antenna element 70_i for both transmit and receive. It is also possible to activate antenna element 70_i on transmit and deactivate antenna element 70_i on receive, or vice versa. For instance, if different respective frequencies are used for transmit and receive, a first subset of antenna elements <NUM> may be optimal on transmit whereas a second subset may be optimal on receive. In this case, if antenna element 70_i is a member of only one of the first and second subsets, it may be activated on transmit and deactivated on receive, or vice versa.

<FIG> illustrates that additional RF front end components may be included in any given FEE <NUM>. For instance, FEE 90e_i includes a switch <NUM> in series with a phase shifter <NUM> and/or a filter <NUM>. Switch <NUM> may be any one of PA <NUM>, LNA <NUM>, in-line switch <NUM>, or the combination of components within FEE 90d_i of <FIG>. Switch <NUM> is on-off controlled via control line 92_i to activate/deactivate antenna element 70_i as described above for <FIG>. Filter <NUM> may be a band pass, high pass or low pass filter. Phase shifter <NUM> may have its insertion phase controlled via a command from controller <NUM> on control line 92_j. By employing a phase shifter <NUM> behind every antenna element <NUM>, a controllable phase gradient may be applied across any candidate subset, which provides further beam peak adjustment capability. However, such further adjustment capability is added at the expense of additional complexity to feed <NUM>. One or more further components such as an upconverter and/or a downconverter may be further included in FEE 90e_i (or may alternatively be coupled between port <NUM> and combiner/divider <NUM>).

<FIG> schematically illustrates another example of an antenna feed, <NUM>', that may be employed in the reflector antenna <NUM>, according to another embodiment. Feed <NUM>' utilizes a smaller number of FEEs <NUM> than feed <NUM> described above, where each FEE <NUM> within feed <NUM>' is coupled to two or more antenna elements <NUM> to control activation/deactivation thereof. Feed <NUM>' includes an N:<NUM> combiner/divider <NUM> that performs the same functionality as N:<NUM> combiner/divider <NUM> discussed above, with the exception of the smaller number FEEs <NUM> being included within combiner/divider <NUM>. Thus, in the transmit direction, combiner/divider <NUM> divides an input RF transmit signal at RF I/O port <NUM> into N divided transmit signals provided at transmission lines 96_1 to 96_N, where the divided transmit signals are routed directly to antenna elements 70_1 to 70_N to generate uplink signal SU. In the receive direction, combiner/divider <NUM> combines up to N element signals directly provided by antenna elements 70_1 to 70_N and provides a combined receive signal at I/O port <NUM>.

In the example of <FIG>, the number of FEEs within feed <NUM>' is reduced from N to N/<NUM> as compared to feed <NUM>. To this end, combiner/divider <NUM> may include "G" hierarchical levels of combiner/dividers, such as 3dB couplers 502_1 to 502_G, interchangeably called <NUM>:<NUM> combiner/dividers. A first set (highest level set) of 3dB couplers is a single coupler 502_1 connected to I/O port <NUM>; a last set (lowest level set) contains N/<NUM> couplers 502_G; a next to last set contains N/<NUM> couplers 502_(G-<NUM>); and sets therebetween (if any, depending on the value of N) are arranged within an (N/<NUM>):<NUM> combiner/divider <NUM> between coupler 502_1 and the set of 502_(G-<NUM>) couplers. FEEs 90_1 to 90_(N/<NUM>) may be controlled by controller <NUM>' in the same way as for feed <NUM> described above, and other aspects of feed <NUM>' may be the same as described above for feed <NUM>.

The switching states of FEEs <NUM> in <FIG> are for the example of activating antenna elements 70_1 to 70_M of subset <NUM> of <FIG> and deactivating remaining antenna elements 70_(M+<NUM>) to 70_N of array <NUM>. Thus, the switching states of FEEs 90_1 to 90_(M/<NUM>) are on and the switching states of FEEs 90_(M+<NUM>) to FGEE 90_N are off. In other embodiments, more or fewer FEEs 90_1 to 90_(N/<NUM>) may be included, e.g., by arranging the FEEs between different levels of combiner/dividers <NUM>. For instance, FEEs <NUM> could be alternatively arranged between the sets of couplers 502_(G-<NUM>) and 502_1 to group more than two antenna elements <NUM> with each FEE <NUM> and reduce the number of FEEs further. The number of FEEs <NUM> and their arrangement may depend on the number N of antenna elements <NUM> within array <NUM>, the number of antenna elements <NUM> within each subset such as <NUM>-<NUM>, the shape of each subset, and whether it is desirable to group more antenna elements per each FEE <NUM> within each of the subsets.

Additionally or alternatively, in some embodiments, distributed amplifiers / phase shifters / filters are unnecessary (e.g., one or more amplifiers behind every antenna element <NUM>, or behind every group of antenna elements <NUM>, is unnecessary). In this case, if some of the N antenna elements 70_1 to 70_N are common to all candidate subsets of antenna elements <NUM> and are therefore always activated, FEEs <NUM> may be omitted in all paths coupled to those antenna elements <NUM>, and may be included in each path, or for each group of paths, coupled to the remaining antenna elements. For example, in some applications, a single low noise amplifier (LNA) or transmit side amplifier (both not shown), coupled to port <NUM>, may be utilized for the entire array <NUM>.

<FIG> schematically illustrates example components of an alternative antenna feed <NUM>" that may be employed within reflector antenna <NUM> of <FIG>. Feed <NUM>" includes interleaved transmit and receive antenna elements 70_1 to 70_N, in which some of the antenna elements <NUM> are transmit antenna elements ("transmit elements") dedicated for transmitting signals and the remaining antenna elements are receive antenna elements ("receive elements") dedicated for receiving signals. The transmit and receive elements are arranged in an interleaving pattern that may vary from embodiment to embodiment. In one example, an alternating interleaving pattern may include transmit and receive elements alternating within rows and/or columns. For instance, as illustrated in the layouts of <FIG> and <FIG>, subset <NUM> may include, in a common row, a transmit element 70_1 adjacent to a receive element 70_2 one column to the right, which is in turn adjacent to a transmit element 70_3, and so on. A staggered arrangement may also be implemented in which elements in the same column differ from row to row. For example, antenna element 70_Q in <FIG> directly above transmit element 70_2 is a receive element.

As depicted in <FIG>, an (N/<NUM>):<NUM> divider 60a may be divide an RF transmit signal input to a port <NUM> into N/<NUM> divided transmit signals, each coupled to one of the N/<NUM> transmit elements 70_1, 70_3,. 70_(N-<NUM>) through a power amplifier (PA) <NUM> functioning as a front end element (FEE) <NUM> as described above. Alternatively, a switch <NUM> or FEE 90e_i (see <FIG>) is substituted for each PS <NUM>. Likewise, an (N/<NUM>):<NUM> combiner 60b may combine (N/<NUM>) element signals from the receive elements 70_2, 70_4,. , 70_N into a combined receive signal that is output to a modem at port <NUM>. In the example of <FIG>, the element signals are first amplified by LNAs <NUM>, each coupled between one of the receive elements and an output port of combiner 60b. Alternatively, a switch <NUM> or FEE 90e_i is substituted for each LNA <NUM>. Coupler <NUM> may couple a portion of the combined receive signal to SMMC <NUM>, which may function in the same way as described above to measure a signal metric and output measured results to controller <NUM>. Controller <NUM> is configured to control the activation/deactivation of antenna elements <NUM> by outputting/withdrawing bias voltages to the PAs <NUM> and LNAs <NUM> on control lines 92_1 to 92_N. Other aspects of feed <NUM>' may be the same as described above for feed <NUM>.

<FIG> is a flow diagram of a method, <NUM>, for adjusting a pointing direction of an antenna beam, according to an embodiment. The operations of method <NUM> may be executed by controller <NUM> or <NUM> controlling the formation of an antenna beam of reflector antenna <NUM>, in cooperation with signal metric measurement circuitry (SMMC) <NUM> performing signal metric measurements on a signal received from a target.

Following manual installation of an array-fed reflector antenna <NUM> and an optional coarse mechanical adjustment of the reflector antenna to coarsely point the beam at a target, a beam may be formed with the reflector antenna by activating a first set of antenna elements (e.g., subset <NUM>) among N antenna elements (e.g., 70_1 to 70_N) of the antenna feed (e.g., <NUM> or <NUM>') (S802). A signal metric of a signal communicated by the beam may then be measured (S804). Typically, this is performed by SMMC <NUM> on a received (downlink) signal SD from the target (e.g., satellite <NUM>). Alternatively, it is possible to measure the signal metric at the target, by measuring a signal transmitted by antenna <NUM>. In this case, the signal metric measurement data is routed to the controller <NUM>, <NUM>' or <NUM> by a suitable link and method.

Once a signal metric associated with the first set of antenna elements is obtained, method <NUM> may iteratively adjust a pointing direction of the beam by activating a different set of antenna elements among the N antenna elements in an iterative sequence (S806). Various types of optimization algorithms may be used for the iterative procedure, where the algorithm selected may depend on the number of antenna sets to be sequentially activated. The signal metric of the signal may then be re-measured with each iterative adjustment of the pointing direction (S808). When the iterative sequence is completed (Y outcome of S809), a final pointing direction and associated final set of antenna elements may be selected for operation of the reflector antenna based on the signal metric measurements (S810). For instance, the subset of antenna elements with the highest signal metric may be selected as the final set.

<FIG> is a flow diagram depicting further example pointing direction adjusting operations in the method <NUM> of <FIG>, which may occur subsequent to an initial set-up (subsequent to operation S810). With these operations, the signal metric of a signal communicated by the reflector antenna <NUM> with the target may be monitored (S902). The monitored signal metric may be compared to a threshold (S904), and if it falls below the threshold (Y outcome of S904), the above-described iterative sequence may be repeated. Thus, the adjustment of the pointing direction in the iterative sequence may be repeated, where the signal metric is re-measured with each iterative adjustment (S906). Upon completion of the re-measurements, the set of antenna elements having the highest signal metric may be re-selected as the final set of antenna elements for subsequent operation of the reflector antenna (S908).

<FIG> is a perspective view of an antenna feed, <NUM>‴, which is an example of antenna feed <NUM> deployable within reflector antenna <NUM>. <FIG> depicts antenna feed <NUM>‴ with internal excitation couplers, which implements spatially overlapping beamforming according to an embodiment. Referring to <FIG> and <FIG>, antenna feed <NUM>‴ may include another example antenna array <NUM> having a plurality of slotted antenna elements 70_1 to 70_N (where N is any suitable integer); a circuit assembly <NUM>' behind antenna array <NUM>, and a plurality J of electromagnetic (EM) couplers 177_1 to 177_J, where J < N.

The structure of antenna feed <NUM>‴ forming the slotted antenna elements <NUM> may be in the form of a hollow disc with a patterned upper surface <NUM> to form the antenna elements <NUM>, and a patterned lower surface <NUM> with openings allowing couplers <NUM> to protrude. Each coupler <NUM> may be an excitation pin that electromagnetically (EM) couples signal energy to/from at least two antenna elements <NUM> that at least partially surround the excitation pin. (Each coupler <NUM> may protrude from one of the openings in bottom surface <NUM> and extend to a point below the upper surface <NUM>. ) For example, peripherally located coupler 177_1, when is partially surrounded by antenna elements 70_1, 70_2 and 70_4 and, when excited (discussed below), couples signal energy to/from these antenna elements. More centralized located elements may couple energy to four surrounding antenna elements in the example. For instance, coupler 177_2, when excited, couples signal energy to/from surrounding antenna elements 70_2, 70_3, 70_4 and 70_5. Because adjacent couplers such as 177_1 and 177_2 are capable of coupling signal energy to some of the same antenna elements, e.g., 70_2 and 70_4, respectively, feed <NUM> may be characterized as a feed that implements spatially overlapping beamforming.

<FIG> is a schematic diagram of the antenna feed of <FIG> according to an embodiment, and illustrates a first example of how a subset of antenna elements may be activated. Antenna feed <NUM>‴ may further include J front end elements (FEEs) 90_1 to 90_J connected to couplers 177_1 to 177_J, respectively, each of which may be configured as discussed above to include at least one switching element. A controller <NUM> may control the switching states of FEEs 90_1 to 90_J through voltages applied on control lines 92_1 to 92_J. A <NUM>:J combiner/divider <NUM> may be coupled between FEES <NUM> and I/O port <NUM>. Coupler <NUM>, SMMC <NUM> and memory <NUM> may operate as described above. In the example of <FIG>, based on the layout of <FIG>, coupler 177_1 is EM coupled to antenna elements 70_1 , 70_2 and 70_4; coupler 177_2 is EM coupled to antenna elements 70_2 to 70_5; coupler 177_3 is EM coupled to antenna elements 70_3 and 70_5 to 70_7; and so forth.

In an example in which it is desired to activate small subsets of antenna elements in the iterative activation sequence described above, only one of FEEs 90_1 to 90_J may be switched on at a time, to thereby activate the antenna elements <NUM> coupled thereto via the connected coupler <NUM>. In <FIG>, FEE 90_2 is switched on while the remaining FEEs, FEE 90_1 and 90_3 to 90_N are switched off. As a result, antenna elements 70_2 to 70_5 are activated and form an activated subset, whereas the remaining antenna elements, 70_1 and 70_6 to 70_N are deactivated.

<FIG> illustrates another activation method for antenna feed <NUM>"', in which a larger subset of antenna elements may be activated. Here, FEEs <NUM> connected to two or more non-adjacent couplers <NUM> may be switched on concurrently, to thereby activate a cluster of antenna elements <NUM> EM coupled to the non-adjacent couplers. In the shown example, FEEs 90_1 and 90_3 are switched on while the remaining FEEs are switched off. Accordingly, based on the layout of <FIG>, antenna elements 70_1 to 70_7 form an activated subset.

Many variations in the layout of <FIG> and <FIG> are available, such that more or fewer groups of antenna elements may be simultaneously activated to form desired subsets for optimizing the antenna <NUM>'s beam pointing angle as described above. Moreover, other types of spatially overlapped beamforming may be implemented.

The various illustrative logical blocks, engines, and circuits described in connection with the present disclosure may be implemented or performed with processing circuitry within any of the reflector antennas (e.g., within controller <NUM>, <NUM>', <NUM> or <NUM>), that may read and execute instructions from a non-transitory recording medium (e.g., memory <NUM>). The processing circuitry may include a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array signal (FPGA) or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any commercially available processor, controller, microcontroller or state machine.

Claim 1:
A reflector antenna (<NUM>) comprising:
a reflector (<NUM>) and a feed (<NUM>) including a planar array (<NUM>) of N antenna elements (70_1 to 70_N), the feed being positioned to illuminate the reflector;
a combiner/divider (<NUM>, (60a, 60b), <NUM>) coupled between the N antenna elements and an input/output port (<NUM>) of the reflector antenna;
signal metric measurement circuitry (<NUM>); and
a controller (<NUM>, <NUM>', <NUM>, <NUM>) cooperating with the signal metric measurement circuitry, said controller configured to:
activate a first set of antenna elements (<NUM>) among the N antenna elements and thereby cause the reflector antenna to form a beam;
measure a signal metric of a signal communicated via the beam;
iteratively:
adjust a pointing direction of the beam at least in part by activating a different set of antenna elements (<NUM>, <NUM>, <NUM>, <NUM>) among the N antenna elements; and
re-measure the signal metric of the signal with each iterative adjustment of the pointing direction; and
select a final pointing direction and associated final set of antenna elements for operation of the reflector antenna, based on the signal metric measurements.