Millimeter wave antenna

A microwave phased array antenna module. The antenna module includes a mandrel having an integrally formed waveguide splitter. Separate electromagnetic wave energy distribution panels that each include DC power, data and logic interconnects, as well as electronic modules incorporating ASICs, phase shifters and power amplifiers, are disposed on opposite sides of the mandrel. Waveguide coupling elements are further secured to the mandrel on opposing sides thereof to couple the electromagnetic wave energy received through an input port of the mandrel with each of the distribution panels. Antenna modules are disposed within openings formed in a second end of the mandrel and electrically coupled via electrical interconnects with the distribution panels. The use of the distribution panels provides ample room for the needed electronics while the use of radiating modules disposed at the second end of the mandrel in a brick-type architecture arrangement relative to distribution panels, enables the extremely tight radiating module spacing needed for V-band operation at up to +/−60° scan angles.

FIELD OF THE INVENTION

The present invention relates to antennas, and more particularly to a dual polarized, microwave frequency, phased array antenna.

BACKGROUND OF THE INVENTION

The Boeing Company (“Boeing”) has developed many high performance, low cost, compact phased array antenna modules. The antenna modules shown inFIGS. 1a–1chave been used in many military and commercial phased array antennas from S-band to Q-band. These modules are described in U.S. Pat. No. 5,886,671 to Riemer et. al. and U.S. Pat. No. 5,276,455 to Fitzsimmons et. al., both herein incorporated by reference.

The in-line first generation module has been used in a brick-style phased-array architecture at K-band and Q-band. The approach shown inFIG. 1arequires elastomeric connectors for DC power, logic and RF distribution but it provides ample room for electronics. As implemented inFIG. 1a, the in-line module provides only a single beam, either linear or right-hand or left-hand circularly polarized. As Boeing phased array antenna module technology has matured, many efforts have resulted in reduced parts count, reduced complexity and reduced cost of several key components. Boeing has also enhanced the performance of the phased array antenna with multiple beams, wider instantaneous bandwidths and improved polarization flexibility.

The second generation module, shown inFIG. 1b, represents a significant improvement over the in-line module ofFIG. 1ain terms of performance, complexity and cost. It is sometimes referred to as the “can-and-spring” design. This design provides dual orthogonal polarizations in a more compact, lower-profile package than the in-line module. The can-and-spring module forms the basis for several dual simultaneous beam phased arrays used in tile-type antenna architectures from S-band to K-band. The fabrication cost of the can-and-spring module has been reduced through the use of chemical etching, metal forming and injection molding technology. The third generation module developed by Boeing, shown inFIG. 1c, provides a low-cost dual polarization receive module used in high-volume production at Ku-band.

Each of the phased-array antenna module architectures shown inFIGS. 1a–1crequire multiple module components and interconnects. In each module, a large number of vertical interconnects such as electrically conductive fuzz buttons and springs are used to provide compliant DC and RF connectivity between the distribution printed wiring board (PWB), ceramic chip carrier and antenna probes.

A further development directed to reducing the parts count and assembly complexity for single antenna modules is described by Navarro and Pietila in U.S. application Ser. No. 09/915,836, presently allowed, and assigned to Boeing. The subject matter of this application is also incorporated by reference into the present application and involves an “Antenna-integrated ceramic chip carrier” for phased array antenna systems, as shown inFIG. 1d. The antenna integrated ceramic chip carrier (AICC) module combines the antenna probes of the phased array module with the ceramic chip carrier that contains the module electronics into a single integrated ceramic component. The AICC module eliminates vertical interconnects between the ceramic chip carrier and antenna probes and takes advantage of the fine line accuracy and repeatability of multi-layer, co-fired ceramic technology. This metallization accuracy, multi-layer registration can produce a more repeatable, stable design over process variations. The use of mature ceramic technology also provides enhanced flexibility, layout and signal routing through the availability of stacked, blind and buried visa between internal layers, with no fundamental limit to the layer count in the ceramic stack-up of the module. The resulting AICC module has fewer independent components for assembly, improved dimensional precision and increased reliability. The inline module, can-and-spring module, the molded module, and the AICC have been realized as single element modules. So far, the AICC has been implemented by Boeing as a single element phased array module which is connected to the printed wiring board and honeycomb in much the same way as the can-and-spring and injection-molded modules. The AICC approach provides manufacturing scalability from single to multiple elements. As manufacturing/assembly process yields increase, the AICC can be scaled from single to multiple element sub-arrays to reduce parts count and assembly complexity.

A Boeing antenna which departs from a single element module is described by Navarro, Pietila and Riemer in U.S. Pat. No. 6,424,313, also incorporated by reference herein, which is shown inFIG. 1e. This module is referred to within Boeing as the “3D flashcube”. It has been implemented as a four-element module to provide additional space for electronics. This approach also avoids the use of fuzz buttons and button holders for its vertical interconnects. It has been used successfully to provide two independent simultaneous receive beams at 21 GHz with +/−60° scanning. It has also been implemented at 31 GHz in a switchable transmit application with +/−60° scanning. The 3D flashcube model can also be used to implement more than two independent receive and/or transmit beams.

InFIG. 1f, Boeing-Phantom Works further combines many more functions of a phased array antenna into a single component through an approach known as the “Antenna Integrated Printed Wiring Board” (“AIPWB”). This approach is disclosed in U.S. application Ser. No. 10/007,067, presently pending, which is also incorporated by reference into the present application. The approach reduces parts count and further improves alignment and mechanical tolerances during manufacturing and assembly. The improved alignment and manufacturing tolerances improves yield and electrical performance while the reduced parts count shortens assembly time and reduces the number of processing steps required to manufacture the antenna module. This ultimately lowers the overall phased array antenna system costs. The AIPWB approach can be scaled to larger sub-arrays without degrading performance and represents an important step in the direction of more easily and affordably manufactured phased array antenna systems.

The first generation module inFIG. 1ais the standard single polarization in-line or brick architecture used extensively for many electronic phased array systems because of the ample room provided for electronics.FIGS. 1b,1cand1duses a tile-type or planar architecture which naturally provides dual polarization. A drawback of the tile architecture is that space is severely limited as frequency and scanning angle increases since the electronics and input/output pads must fit within the physical area of the radiators in the array lattice. Because of the additional input and output pads required to connect to the RF/DC power/logic distribution, single element modules are further constrained in dimensions. As the array dimensions increase, the single element module pads require tighter dimensional tolerances to ensure alignment and connectivity.

FIG. 1eshows another deviation from the single element tile-type modules. It has some of the benefits of tile-type architectures by providing dual polarization and broad-side interconnections to the printed wiring board. It also has some of the benefits of the in-line architectures by providing ample area for electronics and transitions. The 3D flashcube concept has been realized as a quad-module but the approach can be increased to 2×N modules as yield in electronics and packaging increase. The 3D flashcube uses a three layer flexible stripline to provide connections from the electronics to the antennas as well as connections from the electronics to the printed wiring board.

However, even with the 3D flashcube implementation, it is difficult to provide the extremely tight antenna module spacing between adjacent antenna modules that is needed to achieve +/−60° scanning in the microwave frequency spectrum (e.g., 60 GHz). The limitation of using the three layer flexible stripline for interconnections is that as scan angles and frequencies increase, the stripline must be bent at very, very tight (i.e., small) bend radii in order to achieve the extremely close antenna module spacing required for +/−60° scan angle performance in the microwave frequency spectrum. The stripline ground plane and conductor line can break apart at the very small bend radii which is needed to accomplish the extremely tight radiating element spacing necessary for +/−60° scanning at microwave frequencies.

Accordingly, there still exists a need in the art for a dual polarized, phased array antenna which is able to operate within the V-band frequency spectrum (generally between 40 GHz–75 GHz), and more preferably at 60 GHz, while providing at least +/−60° grating-lobe free scanning. Such an antenna, however, requires a new packaging scheme for coupling the electronics of the antenna to the radiating elements in a manner that accommodates the very tight radiating element spacing required for 60 GHz operation, while still providing adequate room for the electronics associated with each antenna module.

SUMMARY OF THE INVENTION

The present invention is directed to a microwave phased array antenna system. The antenna system provides the very close antenna module spacing of adjacent antenna modules needed to achieve operation at 60 GHz (i.e., within the V-band spectrum) while providing a +/−60° scan range. In one preferred form the system includes an electromagnetic wave energy distribution panel that is mounted to one side of a mandrel. The mandrel includes an input for receiving electromagnetic wave energy and a waveguide splitter for channeling the energy to the distribution panel. In one preferred form the mandrel is formed from a single piece of metal with the waveguide splitter machined inside of it. In one preferred form the distribution panel forms a 1×8 microstrip combiner and includes DC power and data logic circuitry. The distribution panel also includes the phase shifters, power amplifiers and applications specific integrated circuits (ASICs) needed for controlling the beam radiated from the module.

The mandrel further includes a second end having a plurality of apertures into which a corresponding plurality of independent antenna modules having electromagnetic radiating elements are disposed. The radiating elements are electrically coupled to the distribution panel via an interconnect assembly coupled at an edge of each distribution panel. In one preferred form the antenna modules each comprise an antenna integrated ceramic chip carrier module such as that shown inFIG. 1d.

In one preferred embodiment a pair of electromagnetic wave distribution panels are disposed on opposite sides of the mandrel. The mandrel, in this embodiment includes a 1×2 waveguide splitter formed intermediate first and second ends and in communication with an input at its first end. A pair of waveguide couplers are disposed on opposite sides of the mandrel to cover corresponding ports formed in the mandrel. The couplers couple electromagnetic wave energy split by the splitter and passing through the ports, to each of the distribution panels. Thus, each of the distribution panels receive approximately 50% of the electromagnetic wave energy traveling through the input. In this embodiment, each distribution panel feeds electromagnetic wave energy to one associated subplurality of the antenna modules.

The antenna system of the present invention provides the benefit of an inline architecture through the use of at least one electromagnetic wave distribution panel mounted along a side portion of the mandrel. This provides ample room for the various electronic components needed for the antenna. The use of antenna modules disposed at one end of the mandrel, and the use of the interconnect assembly, provides the very tight radiating element spacing needed for V-band operation. A plurality of the antenna systems described herein can be easily coupled together to form a single, larger antenna system having hundreds, or even thousands, of antenna modules.

Further areas of applicability of the present invention will become apparent from the following detailed description. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 2 and 3illustrate an antenna system10in accordance with a preferred embodiment of the present invention. The antenna system10is able to operate within the V-band spectrum, and more preferably at 60 GHz, with ±60° scanning capability. The system10generally includes a mandrel12, a first electromagnetic wave energy distribution panel14secured to a first side16of the mandrel12, a second electromagnetic wave energy distribution panel18secured to a second opposing side20of the mandrel12, and a pair of subpluralities of antenna modules22aand22b. The mandrel12includes an input24and a pair of spaced apart interconnects26for coupling to a printed circuit board (not shown). The interconnects26and the input24are formed at a first end28of the mandrel12and the modules22aand22bare disposed in openings30aand30b, respectively, at a second end32of the mandrel12. The openings30aand30bare shown as hexagonal. Other shapes such as circular openings could readily be employed. The openings30aand30breceive the antenna modules22aand22bin the desired orientation.

Modules22aand22bmay be AICC modules in accordance with the teachings of U.S. application Ser. No. 09/915,836, presently allowed, the disclosure of which is hereby incorporated by reference. It will be appreciated, however, that any other antenna component that provides the function of an antenna module that radiates electromagnetic wave energy could be implemented.

With further reference toFIGS. 2 and 5, the mandrel12includes an opening34formed on side16and an opening36formed on side20opposite the opening34. With specific reference toFIG. 2, a first waveguide coupling element38is secured over the opening34and a second waveguide coupling element40is secured within opening36. The two waveguide coupling elements38and40are identical in construction. The openings34and36are further in communication with the input port24and function to couple portions of the electromagnetic wave energy received through input port24with its associated distribution panel14or18.

Referring toFIG. 4, the waveguide coupling element38is shown in greater detail. Waveguide coupling element38is preferably formed from a single block of metallic material, for example aluminum and essentially forms a cover for covering the opening34. The element38includes a recessed area38ahaving an angled surface38cat one end of the recessed area and a centrally disposed rib that forms a projecting stepped waveguide transition surface38bat the opposite end. One waveguide coupling element38is secured over each of openings34and36, such by epoxying or any other suitable means of attachment.

Referring now toFIG. 5, the mandrel12includes a 1×2 waveguide splitter42formed internally adjacent the openings34and36. The waveguide splitter42is longitudinally aligned with the input port24to receive the electromagnetic wave energy traveling through the input port24and to split the energy into approximately two equal subcomponents. Approximately 50% of the electromagnetic wave energy is directed towards opening34and the other 50% towards opening36. A step38b1of stepped surface38bcontacts a circuit trace14aon distribution panel14to transfer the electromagnetic wave energy channeled through opening34into the distribution panel. Angled surface38chelps to channel electromagnetic wave energy received by the antenna system into the opening34during a receive phase of operation. During a transmit operation, openings34and36can be termed as “output'” ports, while during a receive phase of operation they would form “input” ports, and input port24would instead function as an “output” port.

With further reference toFIGS. 2 and 3, printed circuit boards44and46couple the interconnects26with the distribution panel14. A similar pair of interconnects (not shown) is disposed on the second side20of the mandrel12and serves to couple the interconnects26with the distribution panel18.

Referring toFIGS. 2 and 6, each electronic module48in distribution panel14includes an application specific integrated circuit (ASIC)50, a power amplifier52and a phase shifter54. Each electronic module48is associated with a particular one of the antenna modules22aor22b. With specific reference toFIG. 6, an enlarged view of a portion of the distribution panel14illustrates the coupling of one electronic module48with one antenna module22a. A metallic wire or pin56extending from the antenna module22acontacts the circuit trace14ato make an electrical connection between the module22aand the distribution panel14. The wire or pin56is preferably epoxied to the circuit trace14aor otherwise fixedly secured to make an excellent electrical connection with the electronics module48. The wire or pin56also contacts one of radiating/reception elements (i.e., probes)22a1of the antenna module22ato electrically couple the distribution panel14to the radiating/reception element22a1of the antenna module22a. In this regard it will be appreciated that each antenna module22aincludes a pair of radiating/reception elements in the form of probes22a1, such as illustrated inFIG. 2. Independent pins or wires56are independently coupled to each radiating/reception element22a1and22a2. This form of electrical coupling avoids the bending limitations of a stripline conductor that heretofore has prevented the very close antenna module spacing required for +/−60° scanning in the gigahertz bandwith, and thus allows electrical connections to be made to extremely tightly spaced antenna modules.

The mandrel12is preferably formed from a single piece of metal, and more preferably from a single piece of aluminum or steel. The first end28further includes a plurality of openings58for allowing a plurality of antenna systems10to be ganged together to form a larger antenna system composed of hundreds of thousands of antenna modules22.

With reference now toFIG. 7, an antenna system100incorporating eight ones of the antenna system10is illustrated. The antenna system100includes a 1×8 waveguide distribution network102which is coupled to a DC power/logic distribution printed wiring board104. DC power/logic distribution printed wiring board104is in turn coupled to the first end28of each mandrel12of each antenna system10. The antenna system100thus forms a128element millimeter wave (i.e., V-band) phased array antenna system. An even greater plurality of antenna system10components can be coupled together to form a128element,256element, or larger 1×N (where “N” is 2iand “i” is an integer) phased array antenna system. Accordingly, it will be appreciated that antenna systems having varying numbers of radiating elements can be assembled using various numbers of the system10of the present invention.

Referring toFIGS. 8 and 9, the 1×8 waveguide distribution network102can be seen. Network102, in this example, functions to divide electromagnetic wave energy received through an input port106evenly between eight output ports108. Each of the output ports108are longitudinally aligned with an associated input port24of one of the antenna systems10to allow a portion of the electromagnetic wave energy passing through the output port108to enter the input port24of each antenna system10. It will be appreciated that the printed wiring board104includes eight sections or areas which form conventional “pass throughs” (i.e., essentially waveguide structures) to enable the electromagnetic wave energy to pass from each of the outputs108through an associated one of the pass throughs and into an associated one of the input ports24of one of the antenna systems10. Interconnects26(FIG. 2) further electrically couple with portions of the DC power/logic board104on opposite sides of an associated one of the pass throughs so the DC power and logic signals can be provided to the distribution panels14and18of each antenna system10.

It is a principal advantage of the antenna system10of the present invention that the use of the distribution panels14and18of each system provide ample room for the electronics required for the antenna system10, and that the use of the antenna modules22, which are formed in accordance with a brick-type architecture, enable the extremely tight radiating element spacing required for operation at V-band frequencies. The antenna system10thus combines the advantages of previous “tile” type antenna architectures with those of the “brick” type architectures. The antenna system10further combines the use of a stripline waveguide (on distribution panels14and18) with an air-filled waveguide (i.e., input port24) to provide an antenna system with acceptable loss characteristics that still is able to distribute electromagnetic wave energy to a large plurality of tightly spaced antenna modules. The antenna system10further enables easy, modular expansion to create a larger overall antenna system having a much greater plurality of antenna modules. Additionally, the antenna system10is readily suited for use with conventional waveguide distribution network components (e.g., a corporate waveguide component), thus making the system10especially well suited for use in larger (e.g., 128 element, 256 element, etc.) antenna systems.