Patent Description:
Antenna arrays are currently deployed in a variety of applications at microwave and millimeter wave frequencies, such as in aircraft, satellites, vehicles, and base stations for general land-based communications. Such antenna arrays typically include microstrip radiating elements driven with phase shifting beamforming circuitry to generate a phased array for beam steering. In many cases it is desirable for an entire antenna system, including the antenna array and beamforming circuitry, to occupy minimal space with a low profile while still meeting requisite performance metrics.

An "embedded" antenna array may be defined as an antenna array constructed with antenna elements integrated with radio frequency integrated circuit chips (RFICs) in a compact structure. An embedded array may have a sandwich type configuration in which the antenna elements are disposed in an exterior component layer and the RFICs are distributed across the effective antenna aperture within a proximate, parallel component layer behind the antenna element layer. The RFICs may include power amplifiers (PAs) for transmit, low noise amplifiers (LNAs) for receive, and/or phase shifters for beam steering. By distributing PAs and LNAs in this fashion, higher efficiency on transmit and improved noise performance on receive are attainable. Reliability of the antenna array may also be improved, since the overall antenna performance may still be acceptable even if a small percentage of the amplifiers malfunction. The RFICs typically include other beamforming circuitry such as filters, impedance matching elements, RF couplers, transmit / receive (T/R) switches and control lines.

<CIT> discloses an antenna array comprises an isolation element that is formed between a first antenna element and a second antenna element, in a plan view from the first normal line direction of the isolation element.

<CIT> discloses a phased array that has a laminar substrate, a plurality of elements on the laminar substrate forming a patch phased array, and first and second sets of integrated circuits on the laminar substrate.

<CIT> discloses an apparatus for wireless communication. The apparatus includes an integrated circuit, an antenna, and a module located adjacent to the antenna. The module includes at least one of a power amplifier or a low-noise amplifier.

<CIT> relates to a small module in which a radio-frequency circuit and an antenna are integral with each other in a millimeter-wave band.

In an aspect of the present disclosure, an antenna apparatus includes a first component layer including a plurality of RFICs arranged in a first plane with a first lattice geometry, where each RFIC comprises beamforming circuitry. A second component layer overlays the first component layer and includes a plurality of antenna elements arranged in a second plane parallel to the first plane, with a second, different lattice geometry. Each of the first and second lattice geometries is a two dimensional geometry. The first lattice geometry is rectangular and the second lattice geometry is non-rectangular, or vice versa, The antenna elements have respective feed points each coupled to an input / output (I/O) pad of an RFIC. Each I/O pad is substantially aligned with the feed point coupled thereto along an axis orthogonal to the first and second planes.

The first lattice geometry may be rectangular and the second lattice geometry may be triangular.

Since the I/O pads of the RFICs are substantially aligned with the feed points of the antenna elements, transmission lines and/or additional redistribution layers between the first and second layers may be avoided, allowing for a compact, low loss design.

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 a dash and second label that distinguishes among the same / similar elements (e.g., -<NUM>, -<NUM>), 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 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.

<FIG> is a top plan view of an example antenna apparatus, <NUM>, according to an embodiment. Antenna apparatus <NUM> may be constructed in a thin, stacked structure with an upper component layer comprising a plurality of antenna elements <NUM> forming an antenna array in a first plane, a lower component layer comprising a plurality of radio frequency integrated circuit chips (RFICs) <NUM> arranged in a second plane parallel to the first plane, and coupled to antenna elements <NUM>. A substrate <NUM> may be disposed between the upper and lower component layers. A ground plane (not shown) for reflecting signal energy from / to antenna elements <NUM> may be printed on the lower surface of substrate <NUM>. With such a multi-layered structure having integrated antenna elements <NUM> and RFICs <NUM>, antenna apparatus <NUM> may be referred to as an embedded antenna array. In the following discussion, for convenience of description, the horizontal plane / direction will generally refer to the plane / direction parallel to the major surfaces of antenna apparatus <NUM> and the vertical direction will be refer to the orthogonal direction, i.e., the thickness direction of antenna apparatus <NUM>.

Antenna elements <NUM> may each be a microstrip patch antenna element printed on substrate <NUM> and electrically or electromagnetically coupled to ("fed from") an RFIC <NUM> at a respective feed point <NUM>. RFICs <NUM> may be mechanically connected to substrate <NUM> by solder bump connections or the like to the ground plane and other connection pads located on substrate <NUM>. Each RFIC <NUM> may include transmitting and/or receiving RF front end circuitry including amplifiers, phase shifters and filters. (Herein, RF front end circuitry may be interchangeably called "beamforming" circuitry. ) With RF front end amplifiers distributed across the antenna array in this manner, antenna apparatus <NUM> may be referred to as an active antenna array. In some embodiments, each RFIC <NUM> includes receive circuitry comprising at least one low noise amplifier (LNA) for amplifying a receive signal, and at least one power amplifier (PA) for amplifying a transmit signal. If antenna apparatus <NUM> is designed as a phased array, each RFIC <NUM> may include at least one dynamically controllable phase shifter for steering a receive beam and/or a transmit beam.

In one example, antenna apparatus <NUM> is configured for operation over a millimeter (mm) wave frequency band, generally defined as a band within the <NUM> to <NUM> range. In other examples, antenna apparatus <NUM> operates in a microwave range from about <NUM> to <NUM>, or in a sub-microwave range below <NUM>. Herein, a radio frequency (RF) signal denotes a signal with a frequency anywhere from below <NUM> up to <NUM>. It is noted that an RFIC configured to operate at microwave or millimeter wave frequencies is often referred to as a monolithic microwave integrated circuit (MMIC), and is typically composed of III-V semiconductor materials.

Antenna elements <NUM>, when embodied as microstrip patches, may have any suitable shape such as square, rectangular, circular, elliptical or variations thereof, and may be fed and configured in a manner sufficient to achieve a desired polarization, e.g., circular, linear, or elliptical. The number of antenna elements <NUM>, their type, sizes, shapes, inter-element spacing, and the manner in which they are fed may be varied by design to achieve targeted performance metrics. While <FIG> depicts an example with <NUM> antenna elements <NUM>, in a typical embodiment antenna apparatus <NUM> includes hundreds or thousands of antenna elements <NUM>. In embodiments described below, each antenna element <NUM> is a microstrip patch fed with a probe feed. The probe feed may be implemented as a through substrate via (TSV) ("via") that electrically connects to an input / output (I/O) pad of an RFIC <NUM>. An I/O pad is an interface that allows signals to come into or out of the RFIC <NUM>. In other examples, an electromagnetic feed mechanism is used instead of a via, where each antenna element <NUM> is excited from a respective feed point with near field energy.

In antenna apparatus <NUM>, the RFICs <NUM> are arranged in a first lattice geometry whereas the antenna elements <NUM> are arranged in a second (different) lattice geometry. In <FIG> and other examples herein, the first lattice geometry is rectangular (herein, "square" is a subset of "rectangular") and the second lattice geometry is non-rectangular, e.g., triangular, but other combinations are possible in other embodiments. A non-rectangular antenna array lattice geometry (e.g., triangular) can provide desirable performance benefits, such as allowing a wider spacing of antenna elements <NUM> with grating-lobe free performance as compared to a rectangular lattice. Mutual coupling between antenna elements <NUM> can also be beneficially reduced in a triangular lattice as compared to a rectangular lattice configuration.

In any case, although RFICs <NUM> and antenna elements <NUM> are arranged in different respective lattice geometries, each feed point <NUM> is aligned in the vertical direction with a corresponding I/O pad of an RFIC <NUM> connected to that feed point. For instance, the region of each feed point <NUM> in <FIG> is represented as an "o", and the "x" within each "o" represents the connected RFIC <NUM> I/O pad; thus, in the vertical direction the feed point <NUM> overlays the I/O pad. In other words, the I/O pads of various RFICs <NUM> arranged in a horizontal plane define a pattern matching the pattern of the feed points <NUM>. This matching arrangement shortens the distance between each feed point <NUM> and corresponding I/O pad, and obviates the need for lossy transmission lines traversing horizontally therebetween. Conventionally, these transmission lines are formed within multi-layer connections between the RFICs <NUM> and the antenna substrate <NUM>. This is partly because the I/O pads on standard RFICs are arranged symmetrically adjacent to opposite edges of their rectangular footprints. The present embodiments allow for the elimination of such multi-layer connections and a reduction / elimination of losses otherwise caused by such transmission lines.

In <FIG>, locations of the feed points <NUM> and I/O pads of RFICs <NUM> are shown vertically aligned. As used herein, "alignment" of a feed point and a connected I/O pad can be either an exact alignment (within a manufacturing tolerance range) or a "substantial alignment" in which a slight offset is built in for purposes of manufacturability (discussed later). <FIG> also illustrates a case in which each RFIC <NUM> is coupled to four antenna elements <NUM>. In other embodiments, each RFIC <NUM> is coupled to more or fewer antenna elements <NUM>. It is also noted here that in some embodiments, each of the antenna elements <NUM> is shared for transmit and receive operations and each RFIC <NUM> includes suitable transmit / receive (T/R) circuitry for isolating signals in transmit and receive paths therein. However, in other antenna systems, two separate antenna arrays <NUM> are employed - one for transmit and one for receive. In this case, all of antenna elements <NUM> of a given antenna array <NUM> are either "receive antenna elements" dedicated for receive operations or "transmit antenna elements" dedicated for transmit operations.

The respective lattice geometries may be defined by center points <NUM> of the antenna elements <NUM> and center points <NUM> of the RFICs <NUM>. (Note that feed points <NUM> may be offset from respective center points <NUM> of the antenna elements <NUM>. ) Referring to <FIG>, imaginary lines connecting center points <NUM> results in a triangular lattice <NUM> for the antenna elements <NUM>. Imaginary lines connecting center points <NUM> of RFICs <NUM> results in a rectangular or square lattice <NUM> for the RFICs <NUM>. As seen in <FIG>, for the case of four antenna elements <NUM> coupled to one respective RFIC <NUM> in such lattice arrangements, in any given RFIC <NUM>, two I/O pads (the x's within feed points <NUM>) are situated at opposite edges of the RFIC and the other two I/O pads are situated inwardly from the opposite edges. In general, when each RFIC <NUM> in a rectangular lattice is coupled to at least two antenna elements <NUM> in a non-rectangular lattice, some of the RFIC I/O pads may be located at opposite edges of the RFIC <NUM> and remaining I/O pads are located inwardly from these opposite edges. This I/O pad arrangement differs from standard RFICs (having rectangular footprints) which typically have all their I/O pads (including "G" ports of ground-signal-ground ("GSG") or ground-signal ("GS") connection sets, discussed later) located proximate to opposite edges. As a result, when standard RFICs are arranged in a rectangular lattice and coupled to antenna elements in a non-rectangular lattice, some or all of the feed point locations are misaligned with the I/O pad locations. This in turn complicates the design by requiring horizontally oriented transmission lines, and makes the interconnections between the RFICs and antenna elements difficult and lossy. The present embodiments, which employ aligned feed points and I/O pads, avoid such complexity and transmission line losses.

<FIG> is a simplified cross-sectional view of a portion of antenna apparatus <NUM>, depicting an example structure along two adjacent RFICs <NUM> of <FIG>. A plurality of vias <NUM> are formed within substrate <NUM>, each connecting a feed point <NUM> of an antenna element <NUM> to an RFIC <NUM> I/O pad (not shown in <FIG>) at an I/O pad location <NUM>. Hereafter, an I/O pad location <NUM> is assumed to be a central location of the I/O pad. Detailed examples of an I/O pad are described later.

A ground plane <NUM> may be printed on the lower surface of substrate <NUM>. Since the feed point <NUM> locations and the corresponding I/O pad locations <NUM> are vertically aligned, one or more redistribution layers with horizontally oriented transmission lines between RFICs <NUM> and substrate <NUM> can be avoided. Thus, RFICs <NUM> may be attached directly to connection points at substrate <NUM> and ground plane <NUM>. In addition, the alignment of the I/O pad locations <NUM> with the corresponding feed point locations <NUM> reduces the complexity of the antenna substrate <NUM> (including the number of board layers needed. ) Note that the number of dielectric and conductive layers in antenna substrate <NUM> can vary from embodiment to embodiment. It is further noted that in some embodiments, each antenna element <NUM> may have two feed points that connect through two vias <NUM> to two respective I/O pads of an RFIC <NUM> to generate circular polarization in some designs. Designs for antenna element <NUM> described hereinbelow, however, achieve circular polarization utilizing a single feed. Further, if GSG connections are made, ground pads of RFICs <NUM> may be connected to ground plane <NUM> at locations <NUM> on opposite sides of vias <NUM>. Alternatively, GS connections are used in which a single ground pad to ground plane <NUM> connection is made on just one side of a via <NUM>.

<FIG> is a cross-sectional view of an example connection structure, <NUM>, between one antenna element <NUM> and an RFIC <NUM> in antenna apparatus <NUM>. In this embodiment, an "exact" vertical alignment of a feed point <NUM> and a touch pad location <NUM> is targeted by design through a connection via <NUM>. (Due to manufacturing tolerances as discussed below, a prescribed range of horizontal offset may be allocated even in this "exact alignment" case. ) Via <NUM> electrically contacts antenna element <NUM> at feed point location <NUM> and extends through antenna substrate <NUM> to couple antenna element <NUM> to a catch pad <NUM> on bottom surface <NUM> of substrate <NUM>. The feed point <NUM> location is the center of the electromagnetic interface with antenna element <NUM>. In the illustrated example, via <NUM> directly contacts antenna element <NUM> and thus the feed point <NUM> is at the center of the top surface of via <NUM>. In other embodiments in which antenna element <NUM> does not physically contact a via but is capacitively coupled to a slot, the feed point location may be at the optimal coupling location of the slot.

For instance, via <NUM> may be cylindrical and have a diameter D about a central axis <NUM>, and a junction of axis <NUM> and antenna element <NUM> defines the feed point <NUM> location. (If via <NUM> has an elliptical cross section, D may represent a distance across any cross-section of the ellipse. ) Catch pad <NUM> may be deposited and patterned conductive material that can have a footprint with a diameter or width about the same as or slightly larger than diameter D for manufacturing tolerance purposes. RFIC <NUM> has an I/O pad <NUM> which connects to catch pad <NUM> through an electrical connection joint <NUM> (where "s" denotes a "signal" line connection). This connection permits signal communication between antenna element <NUM> and beamforming circuitry (not shown) within RFIC <NUM>. I/O pad <NUM> may be cylindrical, oval or rectangular about a central axis <NUM>. The I/O pad location <NUM> may be defined as a location along central axis <NUM>. In the exact alignment example of <FIG>, a desirable alignment tolerance between axis <NUM> and axis <NUM> (i.e., an allowable horizontal offset due to manufacturing variations) may be about ¼ D. With such a minimal or zero offset, for a given thickness of antenna substrate <NUM> and conductive joining material (the thickness of connection joint <NUM>), the length of the signal path between the feed point <NUM> location and I/O pad location <NUM> is minimized. This allows antenna element <NUM> to be directly connected to RFIC <NUM> through via <NUM> and the conductive joining material (e.g. solder) of connection joint <NUM>, without the need for additional transmission lines or multi-layer connections. One example of a via <NUM> diameter D for millimeter wave designs is in the range of <NUM>-<NUM>. A typical alignment accuracy of an RFIC <NUM> in the exact alignment case may be about <NUM>. In a mm wave design, an example of a diameter or width of an antenna element <NUM> is in the range of <NUM>-<NUM>, with element to element spacing in the range of about <NUM>-<NUM> in each of X and Y directions. An RFIC <NUM> may have a length and width each in the range of about <NUM>-<NUM>. The thickness (height as seen in <FIG>) of each of RFIC <NUM> and underfill layer <NUM> may be on the order of <NUM>, and the thickness of antenna substrate <NUM> may be on the order of <NUM>. All of the above dimensions are exemplary to appreciate the small scale typical for millimeter wave applications, and may be varied by design and/or according to frequency and manufacturing accuracy.

<FIG> also illustrates a GSG connection example, in which a ground connection is made at two locations <NUM> on opposite sides of the above-described signal line connection with connection joint <NUM>. Each ground connection is made by connecting a ground pad <NUM> of RFIC <NUM> to ground plane <NUM> at a location <NUM> through a ground connection joint <NUM>. An isolation layer <NUM> may be comprised of underfill material surrounding each of connection joints <NUM> and <NUM> to provide mechanical support to connection joints <NUM>, <NUM> and thereby improve reliability. A typical underfill material may be a mixed material composed mainly of amorphous fused silica. In other embodiments, underfill material is omitted, whereby the isolation layer <NUM> just represents air. To isolate via <NUM> from ground plane <NUM>, a region of ground plane <NUM> surrounding catch pad <NUM> is cut away to expose a lower surface <NUM> of antenna substrate <NUM>. This feature may best be seen in <FIG>, which is a cross-sectional view through the connection joints <NUM>, <NUM> looking towards substrate <NUM> (with isolation layer <NUM> removed for clarity). Some examples of connection joints <NUM> and <NUM> are copper pillar connection joints, solder joints (e.g. formed from solder balls) and gold to gold bumping connections. As mentioned earlier, an alternative embodiment may employ a GS connection with just a single ground connection on one side of the signal connection. A GSG connection design provides more isolation than a GS design and reduces stray radiation, but is more complex. A GSG connection may have three or more ground connection joints <NUM> in some designs, but a practical implementation has two connection joints <NUM>.

In <FIG> and other figures herein, antenna substrate <NUM> is depicted as a single layer substrate. In other embodiments, antenna substrate <NUM> is a multi-layer substrate with a patterned metal layer to provide some chip to chip RF routing between RFICs <NUM> and/or connections between DC lines on RFIC <NUM>. In this metal layer, metal has been removed in the regions of the vias <NUM> to permit a direct connection between the RFIC <NUM> and antenna element <NUM>. It is further noted here that while a single I/O pad <NUM> is depicted in <FIG>, in other embodiments two or more I/O pads <NUM> connect to each antenna element <NUM> in an alternative scheme for achieving circular polarization.

<FIG> is a cross-sectional view of another example connection structure, <NUM>, between an antenna element <NUM> and an RFIC <NUM>. In this example a feed point <NUM> is "substantially aligned" but not exactly aligned with an I/O port location <NUM> of RFIC <NUM>. (This case may also be considered a subset of an "aligned" configuration as noted earlier. ) To this end, a wider catch pad <NUM> extends beneath via <NUM>, and via <NUM> connects to only a first portion of catch pad <NUM>. A signal connection joint <NUM> underlies a second portion of catch pad <NUM> beyond the first portion. Thus, a connection joint <NUM> does not directly underlie via <NUM>. This approach is advantageous in the case where the process for forming the connection via <NUM> results in a non-planar bottom surface of via <NUM>, which can be translated to the bottom surface of the catch pad. For instance, in the configuration of <FIG>, if catch pad <NUM> has a non-planar bottom surface, the reliability of connection joint <NUM> may be lower than desired. In <FIG>, reliability is improved by substituting the extended catch pad <NUM>, which may have a non-planar bottom surface in the right hand portion below via <NUM> but has a planar bottom surface on the left hand side. As a result, a more reliable connection to the connection joint <NUM> may be formed. RFIC <NUM> in this case includes an I/O pad <NUM> that is symmetrical about a central axis <NUM>. Central axis <NUM> of via <NUM> is horizontally offset from axis <NUM> by a distance d1, where a typical value of d1 may be about D (the diameter of via <NUM>). Although an offset exists between feed point <NUM> location and I/O pad location <NUM>, because the offset is small the two locations are considered aligned. For instance, in terms of wavelengths, a maximum value for the offset d1 may be <NUM> wavelengths at the operating frequency of antenna apparatus <NUM>, which may have a negligible electrical effect on antenna performance as compared to the exact alignment embodiment of <FIG>.

<FIG> illustrates a cross-sectional view of an exemplary detailed connection structure <NUM> between an antenna element <NUM> and an RFIC <NUM> within antenna apparatus <NUM>. The illustrated connection structure <NUM> is an example of connection structure <NUM> of <FIG> and illustrates a closely aligned flip-chip type connection in which a via <NUM> is slightly offset horizontally from a center point <NUM> of an I/O pad <NUM> of RFIC <NUM>. Alternatively, via <NUM> may be exactly aligned with I/O pad <NUM>, and in this case the configuration would be a detailed example of connection structure <NUM> of <FIG>. RFIC <NUM> may be a semiconductor die composed of III-V materials for microwave and millimeter wave designs, or silicon for lower frequencies. Some examples of III-V materials include indium phosphide (InP), gallium arsenide (GaAs), silicon germanium (SiGe) and gallium nitride (GaN). An active die side region <NUM> of RFIC <NUM>, e.g., the upper region of RFIC <NUM> above imaginary line <NUM>, faces toward antenna element <NUM>. Active die side region <NUM> may include doping regions of transistors used in beamforming circuitry, e.g., low noise amplifiers, power amplifiers, T/R switches, phase shifters, etc. A lower surface <NUM> may be plated with metal and used as a ground for the internal circuitry of RFIC <NUM>.

A surface finish metal layer <NUM> such as Electroless Nickel Electroless Palladium Immersion Gold (ENEPIG) may be present between I/O pad <NUM> and connection joint <NUM> to help liquefiable metal (e.g. solder) of connection joint <NUM> to adhere to I/O pad <NUM>. Layer <NUM> may have been formed in the general shape of an upside down truncated cone, with a central cavity on a top surface thereof to provide a more reliable connection interface. When a solder ball or other metal structure is placed and then liquified atop layer <NUM> in a flip-chip connection formation process, a portion of the liquid metal fills the upper cavity. This helps to form connection joint <NUM> as a robust connection between catch pad <NUM> and I/O pad <NUM>. In the example of <FIG>, a metal routing layer <NUM> serves as a redistribution layer to make connections between circuit points within RFIC <NUM> and/or between different RFICs <NUM>. To this end, a first polymer overcoat layer <NUM> such as Benzocyclobutene (BCB) may have been formed between a top surface of RFIC <NUM> and metal routing layer <NUM>, and a second polymer overcoat layer <NUM> may have been formed between metal routing layer <NUM> and isolation layer <NUM>. Layers <NUM> and <NUM> provide isolation and support for metal routing layer <NUM>. The material of layer <NUM> may overlap a peripheral portion of I/O pad <NUM> as illustrated. If metal routing layer <NUM> is omitted, the first polymer overcoat layer <NUM> may still be present on the top surface of RFIC <NUM>. Isolation layer <NUM> surrounds connection joint <NUM> and extends between overcoat layer <NUM> and the lower surface of antenna substrate <NUM>. A similar connection structure may be provided for connecting ground pads <NUM> to a ground plane <NUM> (both not shown in <FIG>). That is, ground pads <NUM> may each be constructed similarly to I/O pad <NUM>, and a surface finish metal layer <NUM> may be present between each ground pad <NUM> and a corresponding connection joint <NUM>, akin to connection joint <NUM> in <FIG>.

The flip-chip connection configuration of <FIG>, while satisfactory for providing a short, aligned connection between the feed point <NUM> and I/O pad <NUM>, may exhibit a side effect of signal loss caused by interfacing the polymer overcoat layer <NUM> with the active die side of RFIC <NUM>. Another possible side effect is due to the proximity between the active die side region <NUM> and the antenna ground plane <NUM> (seen in <FIG>) located between isolation layer <NUM> and antenna substrate <NUM>. This causes a risk of oscillations due to reflections between ground plane <NUM> and the circuitry within active die side region <NUM>.

<FIG> is a cross-sectional view of an example dual via type connection structure <NUM> between an antenna element <NUM> and an RFIC <NUM> in antenna apparatus <NUM>. (Connection structure <NUM> is shown flipped <NUM>° with respect to those of <FIG>. ) Connection structure <NUM> differs from structure <NUM> of <FIG> in that an active die side of RFIC <NUM> does not interface with a polymer layer, whereby loss that otherwise occurs due to such an interface is avoided. In addition, the connection structure is less likely to cause oscillations due to reflections between the antenna ground plane and the active die side region of RFIC <NUM>, since these regions are further apart and do not face each other.

RFIC <NUM> in <FIG> has an active die side region <NUM> above imaginary line <NUM>. A first via <NUM> formed through the die of RFIC <NUM> electrically connects to a conductive trace <NUM> at a local region of the active die side region <NUM>. The local region may be a conductive I/O node of beamforming circuitry within RFIC <NUM>, and conductive trace <NUM> may connect to another circuit point or points of the beamforming circuitry. First via <NUM> may be called a "hot via" because it is not electrically connected to ground. First via <NUM> connects on the opposite end to an I/O pad <NUM> situated on the lower surface of RFIC <NUM> opposite the active side region <NUM>. I/O pad <NUM> in turn connects to antenna element <NUM> at feed point <NUM> through a series of conductors. These may include a copper pillar <NUM> or gold / solder bump, a solder cap <NUM> (or other liquefiable metal cap), a surface finish metal layer <NUM> such as ENEPIG, a catch pad <NUM>, and a second via <NUM> formed through antenna substrate <NUM>. A signal connection joint <NUM> includes copper pillar <NUM> and solder cap <NUM>, where copper pillar <NUM> may have been formed by growing copper up into a pillar, to which solder cap <NUM> was applied to produce signal connection joint <NUM> as a solder connection. Catch pad <NUM> is formed on rear surface <NUM> of substrate <NUM> and may be similar to catch pad <NUM> of <FIG>. A passivation layer <NUM>, e.g., a quartz polymer layer, may surround the surface finish metal layer <NUM> and may have been formed partly on substrate surface <NUM> and partly on an exposed surface of catch pad <NUM>. As described below in the example of <FIG>, one or more passivation layers <NUM> may act as an insulator between ground plane <NUM> and one or more redistribution metal layers between substrate <NUM> and RFIC <NUM>.

For example, when via <NUM> is formed, it may result in a non-planar surface near surface <NUM> of substrate <NUM>, which may be translated to the adjacent region of catch pad <NUM>. Thus, catch pad <NUM> may be designed horizontally extended as shown so that the connection joint region to RFIC <NUM> (layers <NUM>, <NUM> and <NUM>) may have higher strength and reliability. The same is applicable to via <NUM> and catch pad <NUM>. Since the horizontal extensions of catch pad <NUM> and <NUM> may be similar, the feed point <NUM> may be substantially or exactly aligned with the I/O pad <NUM> location <NUM> (i.e., aligned as defined earlier). Further, even if catch pads <NUM> and <NUM> are not designed to extend in the same direction, since the offsets between the respective vias <NUM>, <NUM> and a central axis of connection joint <NUM> are small (e.g., less than <NUM> wavelengths), the I/O pad location <NUM> and antenna feed point <NUM> would still be aligned.

Isolation layer <NUM> (with or without underfill material) may be disposed between passivation layer <NUM> and lower surface <NUM> of RFIC <NUM>. If isolation layer <NUM> is comprised of underfill, since the underfill does not interface with the active die region <NUM> of RFIC <NUM>, signal loss that would otherwise be caused by the interface is avoided. In addition, the likelihood of oscillations is reduced as compared to connection structure <NUM> of <FIG>. This is because active die side region <NUM> is located further away from ground plane <NUM> (not shown in <FIG> but located between surface <NUM> of substrate <NUM> and isolation layer <NUM> as seen in <FIG>, <FIG>, <FIG> and <FIG>). Moreover, a ground surface acting as a ground for beamforming circuitry within RFIC <NUM> may be present at the lower surface <NUM> of RFIC <NUM>, further diminishing the risk of oscillations.

<FIG> is a cross-sectional view of an exemplary portion of antenna apparatus <NUM> depicting an example expanded connection structure encompassing the dual via type connection of <FIG>. Connection structure 700a includes the above-described connection structure <NUM>, with first and second ground connection joints 720g1 and 720g2 on opposite sides, collectively forming a GSG connection set <NUM>. Each of ground connection joints 720g1 and 720g2 may have the same type of construction and similar dimensions as signal connection joint <NUM>. Ground connection joints 720g1 and 720g2 may each electrically connect a respective local region of a ground surface <NUM> of RFIC <NUM> to a connection point on ground plane <NUM>. Local surface finish layers <NUM> may have been applied to ground plane <NUM> to help ground connection joints 720g1, 720g2 adhere to ground plane <NUM>.

<FIG> also illustrates a redistribution layer (RDL) <NUM> that may be present between RFIC <NUM> and ground plane <NUM>. Redistribution layer <NUM> may be used to connect circuit points within RFIC <NUM> and/or circuit points of different RFICs <NUM>, typically to route DC bias between circuit points. RDL <NUM> is formed on a region of passivation layer <NUM>, which isolates it from ground plane <NUM>. A connection joint <NUM> that may have the same type of construction as signal connection joint <NUM> may connect an I/O pad <NUM> of RFIC <NUM> to RDL <NUM>. RDL <NUM> may extend horizontally and connect to another I/O pad of RFIC <NUM> (not shown) or of a different RFIC <NUM> through another connection joint <NUM> to route signals / DC voltages between different circuit points of RFIC(s) <NUM>. If at least one additional RDL <NUM> is added to the antenna apparatus <NUM> configuration, additional passivation layers <NUM> may be disposed on one or more sides of each additional RDL to provide necessary isolation between RDLs.

<FIG> illustrates an example arrangement 800a of antenna element feed point locations with respect to a coupled RFIC in antenna apparatus <NUM>. In this example, an RFIC <NUM> is coupled to four antenna elements <NUM>-a, <NUM>-b, <NUM>-c and <NUM>-d arranged as part of a triangular lattice, with respect to center points <NUM> of the antenna elements. Center points <NUM> may also be referred to herein interchangeably as phase centers <NUM> of the respective antenna elements. RFIC <NUM> is arranged as part of a rectangular lattice as previously illustrated in <FIG> and <FIG>. Antenna elements <NUM>-a to <NUM>-d are each exemplified as a circular patch element with a slit <NUM> (an elongated slot) extending from an open end at a periphery of the antenna element to a closed end towards a center point <NUM>. Antenna elements <NUM>-a to <NUM>-d are coupled to RFIC <NUM> from feed points <NUM>-a, <NUM>-b, <NUM>-c and <NUM>-d, respectively. Note that the "x's" within the "o"'s indicating feed points <NUM> represent I/O pads of RFIC <NUM>, e.g., any of I/O pads <NUM>, <NUM>, <NUM> or <NUM> described above.

Instead of feeding each antenna element <NUM> at its center point <NUM>, feed points <NUM>-a to <NUM>-d, in each group of four antenna elements coupled to an RFIC <NUM>, are each offset in a different direction from the center points <NUM>, and the slits <NUM> are each correspondingly aligned in a different direction. The patch design may be the same for each of the four antenna elements <NUM>-a to <NUM>-d, but rotated in units of <NUM> degrees among the antenna elements. This rotation in the patch design from antenna elements <NUM>-a to <NUM>-d beneficially produces pattern diversity as well as circular polarization with a low axial ratio. Each slit <NUM> location and dimension, and the relative location of an adjacent feed point <NUM>, is designed to produce circular polarization for the corresponding antenna element <NUM>. To this end, a length of each slit <NUM> may be in the range of ¼ to ¾ of the antenna element <NUM> radius. In one example, each slit <NUM> is approximately <NUM>/<NUM> the radius. Feed points <NUM>-a to <NUM>-d are each offset laterally from a side of the adjacent slit <NUM> near the closed end.

A local coordinate system for RFIC <NUM> with a rectangular footprint may be defined with an origin at a center point <NUM>, a X axis parallel to upper and lower sides of the rectangular footprint, and a Y axis parallel to the left and right sides. A local coordinate system of each antenna element <NUM>-a to <NUM>-d may be defined with an origin at a center point <NUM>, an x axis parallel to the X axis and a y axis parallel to the Y axis. Antenna elements <NUM>-a and <NUM>-b are arranged in a top row in which the center points <NUM> have the same +X coordinate and are spaced in the row direction by X1. Antenna elements <NUM>-c and <NUM>-d are in a bottom row at the same -Y level, separated in the row by X1, and spaced from the top row by Y1. The slits <NUM> of antenna elements <NUM>-a to <NUM>-d, and the corresponding feed points <NUM>-a to <NUM>-d, are progressively rotated by <NUM>°. Thus, feed points <NUM>-a, <NUM>-b, <NUM>-c and <NUM>-d are each located in a different quadrant of the local x-y coordinate system. In the example, feed points <NUM>-a to <NUM>-d are in the bottom left (-x, -y), top left (+y, -x), top right (+x, +y), and bottom right (+x, -y) quadrants, respectively. Each feed point <NUM> is offset from the respective center point <NUM> by Δx and Δy in the x and y directions. In the y direction, in each row, the feed points have y-axis variation of 2Δy. In the x direction, as compared to feeding all of the antenna elements at the center points <NUM>, there is a row to row variation of 2Δx.

In the arrangement of <FIG>, the rotation of the patch design, producing variation in the feed point <NUM> locations from quadrant to quadrant with respect to the centers <NUM> of the antenna elements <NUM>, results in improved axial ratio and pattern diversity. However, because the feed points in each row have y-direction variation, the layout of beamforming circuitry within RFIC <NUM> is asymmetrical, which makes the circuit layout and packaging more complex and difficult.

<FIG> illustrates another example arrangement 800b of antenna element feed point locations with respect to a coupled RFIC <NUM> in antenna apparatus <NUM>. This case differs from arrangement 800a in that the feed points <NUM> in each row have the same Y coordinate, which allows for a simpler beamforming circuit layout. As in arrangement 800a, an RFIC <NUM> is coupled to four antenna elements <NUM>-a, <NUM>-b, <NUM>-c and <NUM>-d, which may, for comparison purposes, be assumed to have the same footprints and relative locations as in <FIG>. Each feed point <NUM> is also shown to be offset from the adjacent center point <NUM> by Δx and Δy. However, in arrangement 800b, in the top row, feed point <NUM>-a is in the top left quadrant and feed point <NUM>-b is in the top right quadrant. Thus, the X spacing between these feed points is (X1 + 2Δx), which is wider than that of arrangement 800a by 2Δx. Similarly, in the bottom row, feed point <NUM>-c is in the bottom left quadrant and feed point <NUM>-d is in the bottom right quadrant, such that the X spacing between these feed points is likewise (X1 + 2Δx). Further, in the Y direction the spacing between feed points <NUM> of the upper and lower rows is a uniform (Y1 + 2Δy). It is also noted that the locations of the slits <NUM> with respect to the quadrant locations of the feed points <NUM> are the same as in arrangement 800a.

Accordingly, for a given RFIC <NUM> with I/O pad locations according to arrangement 800b, the I/O pad locations (corresponding to the feed point <NUM> locations) are further apart in both the X and Y directions, as compared to the spacing between center points <NUM>. This is also the case for arrangement 800a, when considering the maximum X and Y spacings between any two feed points <NUM>. Thus, assuming the same beamforming circuitry within the RFICs <NUM> of arrangement 800b vs. 800a, the same rectangular footprint for RFIC <NUM> may be typical.

<FIG> illustrates yet another example arrangement 800c of antenna element feed point locations with respect to a coupled RFIC <NUM> in antenna apparatus <NUM>. In this embodiment, the same relative locations of antenna elements <NUM>-a to <NUM>-d may be assumed, i.e., intra-row antenna element <NUM> spacings of X1 and inter-row spacings of Y1. In arrangement 800c, however, feed points <NUM>-a, <NUM>-b, <NUM>-c and <NUM>-d are located in the bottom right, bottom left, top right, and top left quadrants, respectively. This results in a reduced X spacing of (X1 - 2Δx) between feed points <NUM>-a, <NUM>-b in the top row and also between feed points <NUM>-c, <NUM>-d of the bottom row. Further, the inter-row Y spacing between feed points <NUM> is also reduced to (Y1 - 2Δy). Accordingly, with arrangement 800c, since the corresponding I/O pads (the "x"'s within the feed points <NUM>, representing any of I/O pads <NUM>, <NUM>, etc.) it is possible to use a smaller rectangular footprint for RFIC <NUM>, if the packaging of the beamforming components permits.

Accordingly, aspects of the arrangements 800a, 800b and 800c can be summarized as follows. Each of the RFICs <NUM> includes a plurality N I/O pads coupled to a corresponding plurality of feed points of a group of N circularly polarized antenna elements. A first antenna element of a group has at least one feed point offset from its center point in a first direction, and a second antenna element of the group has at least one feed point offset from its center point in a second, different direction different, where the first and second directions are defined relative to a common coordinate system. Each group may be a group of four antenna elements coupled to a single RFIC. If there are four antenna elements in each group, each of the four antenna elements has a feed point offset from a center of the respective antenna element in a different direction than that of any of the other of the four antenna elements, relative to a common coordinate system. Each of the antenna elements of a group can have the same design configuration with a slit and at least one feed point laterally offset from an edge of the slit to generate the circular polarization for transmit and/or receive operations. Each of the second through fourth of the four antenna elements of a group can be rotated with respect to a first antenna element of the group by K x <NUM>°, where K is in the range of one to three and is different for each one of the second through fourth antenna elements.

<FIG> illustrates an example layout of beamforming circuitry within an RFIC <NUM> having I/O pads arranged according to arrangement 800b of <FIG>. In this example, RFIC <NUM> has four GSG I/O pad connection sets ("GSG sets") <NUM>-a, <NUM>-b, <NUM>-c and <NUM>-d, each having a signal I/O pad ("S pad") <NUM> and a pair of ground ("G") pads <NUM> on opposite sides of the S pad <NUM>. Thus, each of the GSG sets <NUM>-a to <NUM>-d may be a set of linearly aligned first and second ground pads and a signal pad that collectively form an oblong profile with a long axis and an orthogonal short axis, where the long axis is substantially parallel to the left and right edges of the respective RFIC <NUM>.

Each S pad <NUM> may be configured as any of the above-described I/O pads <NUM>, <NUM>, <NUM> or <NUM>, and each G pad <NUM> may be configured as any of the G pads <NUM> of <FIG>. Each S pad <NUM> is coupled to a corresponding feed point <NUM>-a to <NUM>-d using any of the connection structures described above for I/O pads <NUM>, <NUM>, etc. Thus, each S pad <NUM> is aligned with a respective one of feed points <NUM>-a, <NUM>-b, <NUM>-c and <NUM>-d. In each GSG set <NUM>-a to <NUM>-d, the G pads <NUM> and S pad <NUM> may be linearly aligned in the Y direction.

A first output amplifier region <NUM>-<NUM> may be disposed between GSG sets <NUM>-a and <NUM>-b, and a second output amplifier region <NUM>-<NUM> may be disposed between GSG sets <NUM>-c and <NUM>-d. Each GSG set <NUM>-a to <NUM>-d may connect to the output or input of a respective amplifier <NUM> within the adjacent amplifier region <NUM>-<NUM> or <NUM>-<NUM>. In the illustrated example, amplifiers <NUM> are power amplifiers on transmit, and each GSG set connects to an amplifier <NUM> output port. In other examples, some of amplifiers <NUM> are PAs and other amplifiers <NUM> are LNAs. In the latter case, any given GSG set <NUM> may connect to an input of an LNA.

A circuit region <NUM> with additional beamforming circuitry may be disposed outside regions <NUM>-<NUM> and <NUM>-<NUM>. For example, each amplifier <NUM> may be coupled to a respective bandpass filter <NUM> and phase shifter <NUM> within circuit region <NUM>. Generally speaking, amplifiers <NUM> in conjunction with the beamforming circuitry within circuit region <NUM> adjusts (e.g., amplifies, phase shifts, filters, etc.) signals input from / output GSG sets <NUM> (received from / output to antenna elements <NUM>). Circuit region <NUM> may further include at least one combiner / divider <NUM> comprised of one or more RF couplers (e.g., <NUM> dB directional couplers) for combining and / or dividing signals received from / transmitted to at least two antenna elements <NUM>.

GSG sets <NUM>-a and <NUM>-d are disposed proximate the upper left and lower right corners, respectively, of RFIC <NUM>. These locations may be set as close as possible to the respective left and right edges of RFIC <NUM> (as seen in <FIG>) as design rules of the foundry producing RFIC <NUM> allow. GSG sets <NUM>-a and <NUM>-b may be at the same Y level proximate to the upper edge of RFIC <NUM>; and GSG sets <NUM>-c and <NUM>-d may be at the same -Y level proximate to the lower edge. GSG set <NUM>-b may have an X-direction central coordinate about halfway between that of GSG sets <NUM>-c and <NUM>-d. Likewise, GSG set <NUM>-c may have an X-direction central coordinate about halfway that of GSG sets <NUM>-a and <NUM>-b. When each GSG set <NUM> is aligned with a corresponding feed point <NUM> of an antenna element <NUM> as described above, the locations of the GSG sets <NUM> are aligned with the triangular lattice points <NUM> of the antenna elements <NUM> as shown in <FIG>. This configuration differs from standard RFIC chips, which typically have all I/O pads arranged symmetrically adjacent to opposite edges of their rectangular footprints. For instance, in a standard RFIC chip, GSG set <NUM>-c is disposed at the lower left corner and GSG set <NUM>-b is disposed at the upper right corner. The arrangement of <FIG>, which moves some of the GSG sets inwardly from the corners, allows for alignment of the GSG sets with the antenna feed points <NUM>.

Claim 1:
An antenna apparatus (<NUM>) comprising:
a first component layer comprising a plurality of radio frequency integrated circuit chips, RFICs, (<NUM>) arranged in a first plane with a first lattice geometry (<NUM>), each of the RFICs comprising beamforming circuitry (<NUM>, <NUM>); and
a second component layer overlaying the first component layer and comprising a plurality of antenna elements (<NUM>) arranged in a second plane parallel to the first plane, with a second, different lattice geometry (<NUM>), wherein each of the first and second lattice geometries is a two dimensional geometry, the first lattice geometry is rectangular and the second lattice geometry is non-rectangular, or vice versa, the antenna elements having respective feed points (<NUM>) each coupled to an input / output, I/O, pad (<NUM>, <NUM>, <NUM>, <NUM>) of one of the RFICs, each said I/O pad being substantially aligned with the feed point coupled thereto along an axis (<NUM>) orthogonal to the first and second planes.