Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q21/00—Antenna arrays or systems
  • H01Q21/06—Arrays of individually energised antenna units similarly polarised and spaced apart
  • H01Q21/061—Two dimensional planar arrays
  • H01Q21/065—Patch antenna array
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q21/00—Antenna arrays or systems
  • H01Q21/0006—Particular feeding systems
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q21/00—Antenna arrays or systems
  • H01Q21/0006—Particular feeding systems
  • H01Q21/0025—Modular arrays

Definitions

• This invention relates to a multilayer printed wiring board radiating device.
• this invention relates to phased array antennae based on such technology.
• active phased array radar antennae are difficult to be realised within a given small volume and a limited weight budget, while maintaining a high performance and high reliability at an acceptable cost, in particular at high operating frequencies (> 10 GHz).
• These antennae must become even more compact due to emerging requirements for e.g. planar and conformal systems.
• Active phased array antennae are typically characterised by a large bill of materials.
• a large number of separate, individually manufactured radiators e.g. waveguides or vivaldi-type radiators
• must be assembled of individual parts requiring tight assembly tolerances and many complex interconnections. Therefore, production and assembly costs are high, and further miniaturization is limited.
• the radiator design consists of a stack of discs or patches comprising a lower active radiator on a so called dielectric puck, fed by a pair of a so called probes (basically a number of via connections and a parasitic radiator separated from the active radiator by dielectric material.
• this antenna is not optimised and has the above mentioned drawbacks as the known of the art technologies.
• the dielectric pucks comprising the lower active radiators must each be disposed in a surrounding recess formed in an upper dielectric layer of a different material.
• a contemporary X-Band antenna array for radar application may be an assembly of thousands of individually manufactured sub assemblies, each consisting of, for example, a radiator and a number of impedance matching components, a connector assembly, etc. Every part must be manufactured and assembled, hence requiring significant effort and accuracy. Obviously, the involved costs are significant. For example, a radar system of this type could contain significantly more than 3000 transmitting/receiving module channels per antenna array.
• This invention solves the above-mentioned drawbacks using a printed wiring board radiating device more optimised at least in use of available volume by allowing at least some radiators not to be aligned with their respective input/output connectors.
• the obtained system design is thus less complex and requires less tight assembly tolerances.
• An object of this invention is a multilayer printed wiring board radiating device comprising
• a feed layer comprising the feed circuitry; and - A radiator layer coupled to the first face of the feed layer, the radiator layer comprising an array of tab radiator elements (e.g. microstrip patch radiator elements),
• Input/output connectors for connecting transmitter/receiver modules to their respective radiator elements
• An offset layer for correcting the positional shift due to a non-alignment of the radiator with its respective input/output connector, the offset layer being coupled directly or indirectly to the second face of the feed layer.
• a further object of this invention is a phased array antenna comprising the above described multilayer printed wiring board radiating device and at least one transmitter / receiver module connected to the input/output connector linked to the radiator element to be activated.
• FIG. 1 an impression of part of a printed wiring board radiating device according to the invention, - Figure 2, a cross section through a printed wiring board radiating device according to the invention, - Figure 3, an example of an offset layer according to the invention, - Figures 4a and 4b, an implementation of a printed wiring board radiating device according to the invention with T/R modules, Figure 4a is zooming in on a part of Figure 4b showing the link between the T/R modules and the radiators, - Figure 5, an example of calibration layer according to the invention.
• Figure 1 shows an impression of a layered structure of an Antenna PWB (printed wiring board). Only part of the total laminated structure is shown, not to scale.
• PWB printed wiring board
• the printed wiring board comprises dielectric laminates in several striplines 11-14 linked with adhesive 19.
• Each radiator could be surrounded by metallized trenches 18, on the sides of which a metallization has been deposited, to create mentioned “box” structure.
• the "trenches” could be replaced by a pattern of closely spaced metallized holes (blind via's).
• Figure 2 shows a cross section through a typical antenna PWB.
• the printed wiring board radiating device 1 integrates radiators
• phase matched offset circuits 11 feed circuits 13 including their respective microwave interconnections embedded into one multilayer printed wiring board 1, and eventually calibration networks 12.
• the functional design uses a two layer dielectric loaded stripline structure containing the feed circuit within the stripline feed layer 13, and an offset circuit within the stripline offset layer 11.
• the offset circuit for example a phase matched offset circuit, is used to overcome a planar offset between the position of the radiator 143 and its respective feed connector 111 at the back side of the assembly.
• This feed connector 111 could be an RF Coaxial Input/Output.
• the circuit of the stripline feed layer 13 is slot coupled 141 (non galvanic) to an array of arbitrarily shaped microstrip patch radiators 143. This transfer could occur inside a dielectric cavity to reduce RF coupling inside the structure.
• the radiator 143 is surrounded by a conducting "box" 142, 18 to eliminate surface wave coupling phenomena.
• the radiator 143 itself could consist of a arbitrarily shaped patch metallization 142, which is surrounded by machined trenches 18, on the sides of which a metallization has been deposited, to create mentioned "box” structure. Essentially, this box is a plated structure again realised using state of the art PCB technology.
• the radiators 143 could have different 3D shape using the same PCB technology.
• the radiator 143 could consist of one or multiple stacked patches, with or without the metallized box structure, e.g. by surrounding the patches with plated trenches 18.
• the stripline feed layer 13 may also be galvanically connected to the (bottom) patch using a metallized hole (via).
• the box structure can also acts as a dielectric loaded waveguide radiator while the patch metallization 142 could be adapted to an iris type aperture.
• the baseline multilayer printed wiring board radiating device can comprise a total of 10 individual dielectric layers, with the option to add specific layers, for example in case integrated filtering is required.
• the multitude of machined trenches (or via's) tends to undermine the mechanical stability of the laminate; to overcome this problem an auxiliary dielectric layer 15 is attached to make sure that structural integrity is maintained throughout the manufacturing process. This auxiliary layer is later used as a spacer for radome 16/FSS structure 161.
• An optional feature could be a built-in RF filter using, for example, a photonic bandgap structure inside one of the existing stripline layers or an additional dedicated layer (not shown).
• Multilayer printed wiring board technology is an enabling technology used, consisting of organic, controlled dielectric laminates A to J and patterned metallizations 18, with which all features required can be manufactured in a batch process.
• the number of individual parts and assembly steps usually associated with Phased array antennae can be greatly reduced.
• this enables a more flexible, compact and highly integrated design that is also less susceptible to assembly tolerances.
• it facilitates good structural integrity, scalability, integrated calibration, high bandwidth, good scan performance, excellent EMI shielding and low RCS.
• the multilayer printed wiring board radiating device has a low RCS.
• a RF-Via Z axis layer-to-layer interconnect could be implemented through the offset layer 11 and, if needed, the calibration layer 12 to the feed layer 13 in order to bypass layer 11 and 12.
• multilayer printed circuit board technology is based on a laminated structure consisting of selectively plated dielectric layers, together forming a concurrent circuit thanks to post machining and post plating.
• the combination of basic technologies involved, i.e. photochemical etching, laminating, machining and galvanic technologies will enable a clever designer to create more unconventional RF-structures like radiating elements and 3D transitions embedded into and functionally interfacing with the existing RF circuitry, all in one product.
• Each printed circuit board can contain hundreds or even thousands of identical RF structures. Moreover, it enables further integration of additional functionality.
• radiators 142 Due to the mechanical simplicity offered by the technology of multilayer printed wiring board radiating device, it is relatively easy to tune in order to yield a high bandwidth. Furthermore, at an operating frequency up to 12 GHz, the high level of integration that is facilitated by this technology makes sure that radiators 142 can be replaced well within a pitch of half a wavelength. Thus, this enables extreme scan angles (beam agility) without grating lobes occurring. Moreover, as patch radiator 143 is backed by a metallic cavity 18, it has much better directivity than what can usually be achieved by patch radiators, while surface waves are suppressed. This contributes to offering good scan performance.
• the stripline feed circuit 13 is slot-coupled (non galvanic) to each patch radiator 143. Figure 3 shows more in details the offset layer.
• the offset layer 11 is adapted for an array of 256 channels.
• the basic radiator grid pitch is approximately 15 mmx15 mm. Thanks to this offset layer 11 , the T/R modules 2 do not have to be aligned to the radiator grid, thus facilitating for areas that can accommodate, for example, supporting structure, cabling, coolant manifolds, etc.
• the purpose of the offset layer 11 is thus to enable more flexibility in the mechanical design, as the T/R modules 2 are not any longer required to be aligned with their respective radiators 143, which have to be positioned in a fixed grid.
• the offset layer (11 ) introduces a phase matched offset on each channel comprising a radiator element 143 and its respective input/output connector 111 such as the phase matched offset decouples the grid of the radiator element 143 and the grid of its respective external module 2.
• Figures 4a and 4b show the advantage of the offset layer to facilitate for space behind the antenna array for auxiliary functions.
• the advantage applies to both horizontal and /or vertical offset even if the figure only shows vertical offset.
• FIG. 4b shows an antenna multilayer 1 connected to T/R modules 2 contained in standard racks comprised between structural support 3 comprising, if needed, cooling manifold and cabling or printed wiring.
• the structural support is adapted to receive the T/R modules 2, the latter not having to be aligned to their respective antenna radiator.
• the offset layer 11 facilitates the interconnection between
• FIG. 5 shows in more detail the calibration layer containing a testpulse distribution network and couplers for each of the 768 channels 51 in this example. This testpulse signal is being injected into each channel using couplers. This is a very convenient and cost effective way to keep the antenna calibrated at all times.
• integrated calibration is rarely done because of manufacturing difficulties. In e.g. waveguide technology, it means that a full testpulse distribution circuit must be interlaced with all the active radiator channels (at least several thousands of channels), adding many more parts and making assembly much more complicated and requiring an even higher level of accuracy.
• an integrated calibration layer 12 can be used very frequently and under all circumstances keeping the antenna 1 calibrated at all times for maximum performance.
• the complete assembly is based on known production processes, tailored to obtain the structures and features required for this application. It consists of a sequence of photolithographic, 3D Machining, galvanic and laminating processes to create the desired multilayer printed wiring board radiating devices. The sequence in which these process steps take place is a crucial factor and determines the feasibility of the design.
• This multilayer printed wiring board radiating device design has inherent structural integrity. From a mechanical point of view, a multilayer printed circuit board is a laminated, polymer composite panel. The thickness of a panel as described is more than about 10 millimetre. Hence, it is very rigid and does not usually require additional structural backup, thus simplifying the mechanical design of the radiating device.
• applications are primarily radar, but could also include wireless telecommunication applications.
• this could be applied in, for example S-Band and X-Band radar systems, but the invention is also suitable for a wide range of other frequency bands.
• the higher frequency bands will benefit more due to smaller feature sizes, which are proportional to the wavelength.

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• Variable-Direction Aerials And Aerial Arrays (AREA)
• Waveguide Aerials (AREA)

Applications Claiming Priority (2)

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Cited By (5)

Citations (5)

• 2004
  • 2004-05-03 NL NL1026104A patent/NL1026104C2/nl active Search and Examination
• 2005
  • 2005-04-26 WO PCT/EP2005/051876 patent/WO2005107014A1/en active Application Filing

Patent Citations (5)

Non-Patent Citations (2)

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