Multi title-configured phased array antenna architecture

A multi-tile configured, two-dimensional phased array antenna architecture is configured of an gridwork of sub-array `tiles`, each of which contains a mechanically integrated and RF-integrated antenna elements and RF interface components therefor. Each tile is formed of a multilayer printed wiring board and supports a sub-array of antenna elements and their associated RF circuits, so that the tile itself is effectively an operative phased-array antenna. The gridwork supports the sub-array tiles in sealed engagement with the framework, whereby associated RF networks components at rear sides of the tiles are protected against the free space environment to which the antenna elements on front faces of the tiles are exposed. Each RF interface network contains signal processing circuitry for controlling the operation of a respective one or a set of the antenna elements on the front side of the tile.

FIELD OF THE INVENTION 
The present invention relates in general to communication systems and 
components, and is particularly directed to a new and improved phased 
array antenna architecture, configured of an array of multilayer printed 
circuit wiring board-based tiles. Opposite sides of a respective tile 
respectively support plural antenna elements and associated RF signal 
processing interface networks therefor, that are coupled to one another by 
way of RF feeds through the multilayer printed circuit wiring board. The 
array also contains power and control units mounted to the sides of the 
tiles containing the RF signal processing interface networks. 
BACKGROUND OF THE INVENTION 
Conventional phased array antenna structures, an example of which is 
described in U.S. Pat. No. 5,206,655, employ relatively complex electrical 
and mechanical structures, that contain diverse types of individually 
packaged RF modules, including those housing the antenna radiator element, 
and associated RF electronics, power supplies, control processor units and 
RF distribution circuits. As these modules are typically assembled in 
honeycomb or mechanically layered architectures, they require large 
numbers of different types of cabling and interconnects, which may entail 
the use of thousands of ribbon bond connections for large scale 
applications. Such complexities of structural design and assembly not only 
make these systems expensive to manufacture, but result in phased array 
antenna architectures that have a relatively large size and 
weight--constituting a substantial payload penalty for airborne and 
spaceborne applications. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, the above described weight and 
cost drawbacks of conventional phased array antenna designs are 
substantially reduced by a multi-tile configured, two-dimensional phased 
array architecture configured of a gridwork of sub-array tiles, each of 
which contains a mechanically integrated and RF-integrated antenna 
elements and RF interface components therefor. Because each tile of the 
overall array provides both mechanical and electrical support for a 
sub-array of antenna elements and their associated RF circuits, the tile 
itself is effectively an operative phased-array antenna. This novel 
architecture is extremely flexible and is not limited by frequency, 
electrical scan requirements, antenna element array type, or the RF 
components used. 
The two dimensional tile-supporting gridwork is configured as a generally 
planar frame having a two-dimensional matrix of generally polygonally 
shaped pockets, that are sized to receive and support in a sealed 
engagement respective ones of a plurality of sub-array `tiles`. Because 
the pockets of the supporting framework allow the sub-array tiles to be 
mounted in sealed engagement with the framework, the components of 
associated RF networks components at rear sides of the tiles are 
inherently protected against the free space environment to which the 
antenna elements on front faces of the tiles are exposed. Each RF 
interface network contains signal processing circuitry for controlling the 
operation of a respective one or a set of the antenna elements on the 
front side of the tile. 
A plurality of power supply and control units are supported at the back 
sides of a plurality of tiles of the array. A respective power supply and 
control unit contains power supply circuitry for supplying DC power to the 
interface circuits of multiple tiles of the array, a supervisory 
microcontroller that is programmed to control the operation of sub-array 
tiles, and RF distribution networks. Connectivity between each power and 
control unit and the tiles it controls and powers may be provided by 
ribbon cables, and coaxial cables for RF distribution, connected 
therebetween. 
An alternative configuration of the connection scheme employs a frequency 
multiplexed cable, wherein respective DC power, control signals and RF 
signals are carried over a single transmission cable. Each has an allotted 
frequency spectrum on the cable, and filtering among the respective DC 
power, control and RF signals takes place on tile. 
A first embodiment of a tile is formed of a laminate structure containing a 
generally planar metallic layer and a multilayer printed wiring board. An 
outer face of the metallic support layer provides a support surface for 
the sub-array of antenna elements. RF-connectivity between the antenna 
elements and RF coupling ports of associated RF interface circuits on the 
rear face of the printed wiring board is directly provided by means of a 
conductive pin that passes through a generally cylindrical aperture in the 
tile. This RF connectivity pin is preferably encapsulated in a dielectric 
medium, such as a glass bead, that fills the aperture and provides both 
mechanical stabilization and a matched impedance RF transmission path 
between the antenna element and an RF output amplifier chip that is 
surface-mounted to an outer RF microstrip layer of the RF interface 
circuit. 
The laminate structure of a second embodiment of a tile is comprised of a 
multilayer printed wiring board, without a metallic support layer. 
RF-connectivity between the antenna elements and their associated RF 
interface circuits is provided by means of a plated through holes in the 
multilayer printed wiring board. 
Alternative configurations of each of the first and second embodiments 
include placing RF signal processing components on the same face of the 
tile as the antenna elements. These RF components may be connected to RF 
components on the other side of the tile using RF links through the 
printed wiring board, in effectively the same manner that the antenna 
elements are connected therethrough. The alternative configuration can 
improve performance through the use of shorter length RF pathways to the 
antenna elements, and also allows for higher packaging density.

DETAILED DESCRIPTION 
FIGS. 1-9 diagrammatically illustrate the architecture of the sub-array 
tile based, electronically scanned phased array antenna in accordance with 
the present invention. As shown in FIGS. 1 and 2, the antenna array 
comprises a generally planar or flat grid-configured support member, such 
as a metallic (e.g., aluminum) frame 10, having a two-dimensional matrix 
of generally polygonally shaped (e.g., square) pockets 12. The frame 
pockets 12 of the supporting framework are sized to receive and support in 
a sealed engagement respective ones of a plurality of sub-array `tiles` 
20, front sides 21 of which contain a plurality of antenna elements 30, 
and which are configured to conform with the geometries of the pockets 12. 
For purposes of illustrating a reduced complexity example, the gridwork 
geometry of the tile-supporting frame 10 is shown as defining a 4.times.4 
array of generally square shaped pockets. It is to be understood, however, 
that the gridwork geometry is not limited to defining pockets of a 
particular shape or number. 
Because the pockets of the framework 10 allow sub-array tiles 20 to be 
mounted in sealed engagement with framework 10, the components of 
associated RF networks components 40 mounted to rear sides 23 of the tiles 
are inherently protected or sealed against the free space environment to 
which the antenna elements are exposed. Also, this two dimensional 
gridwork support structure facilitates repair and replacement of 
individual sub-array tiles. 
As shown in the front view of FIG. 1, and the partial perspective view of 
FIG. 2, a plurality or sub-array of free space RF energy-coupling 
(emitting--receiving) antenna elements 30 are distributed on a first, 
front side or face 21 of a respective sub-array tile 20. In a 
complementary fashion, as shown in the overall tile matrix rear view of 
FIG. 3, the side view of FIG. 4, and the rear view of a respective tile in 
FIG. 5, a plurality of RF interface networks 40 may be formed on a second, 
back side or face 23 of a respective sub-array tile 20. Each RF interface 
network 40 is associated with and contains signal processing circuitry for 
controlling the operation of a respective one or set of the antenna 
elements 30 on the front side of the tile. 
Also shown in FIGS. 3 and 4 are a plurality of power supply and control 
units 50-1 and 50-2, mounted to the back sides of a plurality of tiles 
(e.g., four tiles per power and control unit, as shown). A respective 
power supply and control unit 50 contains power supply circuitry for 
supplying DC power to interface circuits 40 of multiple tiles of the 
array, a supervisory microcontroller programmed to control the operation 
of multiple sub-array tiles, and the RF distribution networks thereof. 
As pointed out briefly above, connectivity between each power and control 
unit 50 and the tiles it controls and powers may be provided by ribbon 
cables and RF coaxial cables 51 connected therebetween. An alternative 
connection scheme to be described below with reference to FIG. 8, employs 
a frequency multiplexed cable, wherein respective DC power, control 
signals and RF signals are carried over a single transmission cable. Each 
has an allotted frequency spectrum on the cable, and filtering among the 
respective DC power, control and RF signals takes place on tile. 
FIG. 6 is a diagrammatic partial side view showing the laminate structure 
of a first embodiment of a respective tile 20, and the manner in which RF 
coupling between an antenna element 30 on the front face 21 of the tile 
and its associated RF interface circuit 40 on the tile's rear face 23 is 
directly coupled through the tile. In accordance with this first 
embodiment, a tile is comprised of a laminate arrangement of a generally 
planar metallic support plate 60, and a multilayer printed wiring board 
70. The multilayer printed wiring board 70 may comprise a laminated 
arrangement of alternating dielectric (e.g. co-fired ceramic) layers, and 
conductive stripline layers patterned to define RF filtering and signal 
distribution circuitry on a rear face 71 of the board 70, and an internal 
interconnect structure therefor. RF signal distribution and filtering 
stripline circuit patterns may also be provided on one or more interior 
layers of the printed wiring board laminate structure. 
As a non-limiting example, the multilayer printed wiring board 70 may be of 
the type described in the U.S. Pat. No. 5,384,555 to Wilson et al, 
entitled "Combined RF and Digital/DC Signalling Interconnect Laminate," 
assigned to the assignee of the present application and the disclosure of 
which is incorporated herein. An outer face 61 of the metallic support 
layer 60 provides the mounting/support surface for the sub-array of 
(radiating) antenna elements 30. As a non-limiting example, antenna 
elements 30 may be configured as stacked patch antennas, such as those 
described in the U.S. Pat. No. 5,874,919 to Rawnick et al, entitled: 
"Stub-Tuned, Proximity-Fed, Stacked Patch Antenna," assigned to the 
assignee of the present application and the disclosure of which is 
incorporated herein. 
RF-connectivity between a feed port 31 of the antenna element 30 and an RF 
coupling port 41 of its associated RF interface circuit 40 formed on the 
rear face 71 of the multilayer printed wiring board 70 is provided by 
means of a conductive (e.g., gold) pin 33, that passes through a generally 
cylindrical aperture 63 in the metallic support layer 60 and the 
multilayer printed wiring board 70. The RF transmission pin 33 may be 
surrounded by or encapsulated in a dielectric medium, such as a glass bead 
35, that fills the aperture 63 and provides both mechanical stabilization 
and a matched impedance RF transmission line path between the antenna 
element 30 and RF circuitry, such as an RF output amplifier chip 45, 
surface-mounted to an outer RF microstrip layer of the RF interface 
circuit 40. 
Such a direct, shortest distance RF connection between an antenna element 
30 on the front side of the tile and its associated RF interface circuit 
40 on the rear side of the tile provides a substantial increase in power 
efficiency in transmit mode, and also decreases the noise figure of a 
receive array. Surface-mounting the RF electronic components to the rear 
sides 23 of the tiles 20 eliminates the need for complex, time consuming 
and expensive wire-bonding employed for individual mechanically parasitic 
phased array modules and panels of conventional phased array systems. It 
also reduces substantially the size and weight penalty associated with 
additional connectivity material. Moreover, this approach is not limited 
to surface-mount packaged components, and may include chip-on-board and 
flip-chip technology. 
As pointed out above, an RF microstrip layer formed on the rear face and/or 
interior layers of the multilayer printed wiring board 70 may be 
selectively etched to realize various components of an RF signal coupling 
network, such as but not limited to filters, power dividers, circulators 
and the like, to which one or more active RF circuit devices and 
millimeter wave, microwave integrated circuit (MMIC) signal processing 
circuits therefor, such as RF power amplifiers, multiplexer units, etc. 
are mechanically and electrically connected (e.g., using flip-chip or 
other surface mount configurations). 
The laminate structure of a second embodiment of a respective tile, and the 
manner in which an antenna element 30 on the front face 21 of the tile is 
coupled through the tile to an associated RF interface circuit 40 on the 
tile's rear face 23 is shown diagrammatically in the partial side view of 
FIG. 7. In the second embodiment, the mechanical strength and electrical 
interconnectivity (including control signals and DC power distribution) of 
the tile are provided by a multilayer printed wiring board 80 of the type 
described in the above-referenced Wilson et al patent. 
A first face 81 of the board 80 provides a mounting and support surface for 
the sub-array of (radiating) antenna elements 30. As in the first 
embodiment, each antenna element 30 may be configured as a stacked patch 
antenna described in the Rawnick et al U.S. Pat. No. 5,874,919. In the 
second embodiment, RF-connectivity between feed ports of the antenna 
elements 30 and RF coupling ports of their associated RF interface circuit 
devices 45 formed in an RF microstrip layer on the rear side 81 or 
interior layers of the printed wiring board 80 is provided by means of 
plated through holes 85 in the multilayer printed wiring board 80. 
As pointed out briefly above, connectivity between each power and control 
unit and its associated tiles may be provided by ribbon cables and RF 
coaxial cables connected therebetween. An alternative DC-powering, control 
and RF distribution signal connection scheme employs a single, frequency 
multiplexed cable, that transports DC power, control signals and RF 
signals in respectively allotted portions of the frequency spectrum, with 
filtering among these three components taking place on the tile proper, as 
shown diagrammatically in FIG. 8. 
More particularly, FIG. 8 shows an enlarged portion of the rear view of a 
respective tile of FIG. 5, having a coaxial connector 91 to which the 
frequency multiplexed coaxial cable from a power and control unit is 
connected. The coaxial connector 91 is coupled through a capacitor and 
inductor configured low pass filter 93 to a plated via 95, through which a 
filtered-out DC voltage is coupled to the power distribution conductors of 
the printed wiring board. 
The output of the coaxial connector 91 is further coupled to a plated via 
97, to which a quarter wave RF open tuning stub 99 is connected. The RF 
open tuning stub 99 removes the RF signals, so that plated via 97 may 
supply the control signals to the control signal distribution portion of 
the printed wiring board. The coaxial connector 91 is additionally coupled 
to an RF high pass filter 101, to which a Wilkinson power divider 103 is 
connected. The output of the Wilkinson power divider 103 is coupled to a 
section of RF stripline 105, to which RF components are connected. 
As noted earlier, alternative configurations of the printed wiring 
board-based tiles include placing RF signal processing components on the 
same face of the tile as the antenna elements. This is diagrammatically 
illustrated in the side view of FIG. 9, which shows RF components 110 
mounted on the front side 21 of a tile adjacent to the antenna elements 
30. These front side-mounted RF components 110 may be connected to the RF 
components 40 on the rear side 23 of the tile via RF links 112 through the 
printed wiring board, in effectively the same manner that the antenna 
elements are connected therethrough, as described above. This alternative 
front side mounting of RF components can improve performance through the 
use of shorter length RF pathways 114 to the antenna elements 30, and also 
allows for higher packaging density, as described above. 
As will be appreciated from the foregoing description, substantial weight 
and cost of manufacture shortcomings of conventional discrete module-based 
phased array antenna designs are substantially reduced by a multi-tile 
configured architecture, in which a respective sub-array tile contains 
mechanically integrated and RF-integrated antenna elements and RF 
interface components. Not only does such a tile-based architecture 
facilitates shortest distance connections between antenna elements and 
their RF feed circuit, it provides a substantial increase in power 
efficiency in transmit mode, and decreases the noise figure of a receive 
array. 
Also, surface-mounting the RF electronic components to the rear sides of 
the tiles eliminates the need for complex, time consuming and expensive 
wire-bonding employed for individual mechanically parasitic, phased array 
modules of conventional phased array systems substantially reduces the 
size and weight penalty associated with this additional connectivity 
material, and provides protection for the components of associated RF 
networks components at rear sides of the tiles are inherently protected 
against the free space environment to which the antenna elements on front 
faces of the tiles are exposed. 
While we have shown and described several embodiments in accordance with 
the present invention, it is to be understood that the same is not limited 
thereto but is susceptible to numerous changes and modifications as known 
to a person skilled in the art, and we therefore do not wish to be limited 
to the details shown and described herein, but intend to cover all such 
changes and modifications as are obvious to one of ordinary skill in the 
art.