A portion of the disclosure of this patent document contains material which is subject to copyright protection. This patent document may show and/or describe matter which is or may become trade dress of the owner. The copyright and trade dress owner has no objection to the facsimile reproduction by anyone of the patent disclosure as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright and trade dress rights whatsoever.
This patent is related to a copending application, attorney docket number R009-P07238US, entitled “Modular MMW Source Component”.
1. Field
This disclosure relates to sources for millimeter wave (MMW) RF power, and to high power sources for W-band applications in particular.
2. Description of the Related Art
Sources of medium and high power MMW radiation can be applied in communications systems and in directed energy weapons. While lower frequency MMW wave application can now be satisfied with solid-state sources, high power sources for the W-band (75 MHz to 110 MHz) traditionally incorporate tubes such as magnetrons or gyrotrons. However, such tubes are expensive, bulky, fragile, and require high voltage electrical power. Thus MMW sources incorporating tubes are not readily portable.
Semiconductor devices are now available for use as oscillators or amplifiers in the W-band, but the available power output from each semiconductor device may be limited to no more than a few watts. Thus medium and high power solid state W-band sources may use quasi-optical methods that combine the power output from a large plurality of semiconductor devices within a waveguide or in free space. Approaches that have been suggested for combining the power output from plural semiconductor devices include the reflect array amplifier described in U.S. Pat. No. 6,765,535, the grid array amplifier described in U.S. Pat. No. 6,559,724, and the lens array or tray amplifier described in U.S. Pat. No. 5,736,908.
Throughout this description, the embodiments and examples shown should be considered as exemplars, rather than limitations on the apparatus and methods disclosed or claimed.
Description of Apparatus
Referring now to the block diagram of
Each circuit device 160A-H may include one or more of an amplitude adjuster 162, a phase shifter 164 and an amplifier 166. The amplitude adjuster may be a variable attenuator, a variable gain amplifier stage within or in addition to amplifier 166, or some other gain adjusting device. The amplitude adjuster 162, the phase shifter 164 and the amplifier 166, may be separate devices or components, or may be completed or partially implemented in one or more monolithic microwave integrated circuits. The circuit devices 160A-H on any submodule 140A-H may be identical or may be different.
Each circuit device 160A-H may have an input coupled to a corresponding receiving element and an output coupled to a corresponding radiating element. For example, receiving element 150A may be coupled to the input of circuit element 160A, and the output of circuit element 160A may be coupled to radiating element 170A. Receiving element 150A and radiating element 170A may each be a flared notch antenna, a tapered slot antenna, a Vivaldi antenna, a dipole antenna, a Yagi-uda antenna, or any other end-fire antenna element. Receiving element 150A and radiating element 170A may be identical or may be different.
The power source module 100 may include a wavefront expander 120 to accept an MMW input wavefront 110 and to provide an expanded MMW wavefront 130. The MMW input wavefront 110 may be coupled from a waveguide or other transmission medium. The wavefront expander 120, represented in the block diagram of
The expanded MMW wavefront 130 may be coupled to the receiving elements, such as receiving element 150A, on the submodules 140A-H. Each receiving element may convert a portion of the energy of expanded MMW wavefront 130 into a signal coupled to the input of a corresponding circuit device. Each circuit device may amplify or otherwise modify the input signal from the corresponding receiving element and provide an output signal to the corresponding radiating element. For example, receiving element 150A may provide an input signal to circuit device 160A. Circuit device 160A may, in turn, provide an output signal to radiating element 170A. Each radiating element may convert the output signal from the corresponding circuit element into a radiated wavefront (not shown). The radiated wavefronts from the plurality of radiating elements on the plurality of submodules may be spatially combined to provide an output wavefront (not shown) that differs from the expanded wavefront 130 in amplitude, direction, or some other property. The spatially combined output wavefront may be coupled into an output waveguide (not shown) or radiated into free space.
Each dielectric substrate 242 may support linear arrays of receiving elements and radiating elements coupled to and generally aligned with the circuit devices such as circuit device 160. The receiving elements and radiating elements may be constructed as metal films on one or both sides of the dielectric substrate 242 and are thus not visible in
The spacing between the rows of elements (the center-to-center spacing of the radiating elements on each submodule as shown in
Each submodule may also include a heat spreader 244 to conduct heat from the circuit devices to the heat sink structures 222 and 228. The heat spreader may be comprised of a metal material such as aluminum or copper, or a thermally conductive ceramic material such as alumina, beryllia, or aluminum nitride. The heat spreader 244 may be the same material as the dielectric substrate 242 or another material. The heat spreader 244 may be bonded or otherwise attached to the dielectric substrate 242 with a heat conducting material. Similarly, the interfaces 246 and 247 between the heat spreader 244 and the heat sink structures 222 and 228 may be filled with a heat conducting material. Suitable heat conducting materials may include a thermally-conductive grease, a thermally-conductive adhesive, a brazing material, or some other thermally-conductive material.
The power source module 200 may include end caps on one or both sides, of which only end cap 280 is shown in
The edges of the submodules (i.e. the top and bottom edges as shown in
The wavefront expander may be comprised of two sections. The first section may be a waveguide power divider 380 that expands the input wavefront along the axis normal to the page in
Referring back to
Metal structures 322 and 328 may function as a heat exchanger to remove heat generated in the submodules such as submodule 340A. Metal structures 322 and 328 may each include one or more heat exchanger coolant channels 390. Heat generated in the circuit devices on the submodules may be coupled to the metal structures 322 and 328 by heat spreaders incorporated in each submodule. This heat may be conducted through the metal structures 322 and 328, and then transferred to a coolant fluid flowing through the heat exchanger coolant channels 390. The coolant fluid may be gaseous or liquid. While the heat exchanger coolant channels are shown as simple circular openings in
Metal structures 324 and 328 may be a single continuous piece, or may be separated by a dielectric slab 326. When the dielectric slab is present, metal structure 328 may be electrically isolated at DC and low frequencies from metal structures 324 and 322. When the dielectric slab 326 is present metal structures 322 and 328 are DC isolated, and may be used as a DC feed network to provide DC electrical power to the submodules, such as submodule 340A. In this case, each submodule may be electrically coupled to the metal structures 322 and 328.
When metal structures 324 and 328 are DC isolated by dielectric slab 326, a standard RF choke groove 327 may be cut into either metal structure 324 or 328. The use of such grooves is fairly common practice when joining waveguide flanges. The RF choke groove is located one-fourth of a wavelength (accounting for the dielectric constant of the dielectric slab 326) from the surface of the metal structure, and is cut one-fourth of a wavelength deep. The resultant effect is a one-half wavelength shorted transmission line which acts as an RF short across the discontinuity caused by dielectric slab 326. Thus the presence of the dielectric slab 326 does not effect propagation of the MMW wavefront in the parallel plate horn formed by metal structures 322 and 328.
When the metal structures 322 and 328 are used as a DC feed network to provide DC electrical power to the submodules, such as submodule 340A, end caps (not visible in
The height 530 of each submodule may be essentially equal to Mλy. To allow room for the metal structures that conduct heat away from the submodules, the height 530 of each submodule may be essentially equal to (M+1)λy. In this case the spacing 540 between rows of radiating elements may be essentially equal to λy except at the boundaries between adjacent submodules, where the spacing 550 between radiating elements may be essentially equal to 2λy. Effectively, a single row of radiating elements may be missing at the boundary between adjacent modules.
As used in the preceding paragraphs, height and width, and row and column, are relative terms descriptive of the modular power source as shown in
The modular MMW power source may include end caps, similar to end cap 280 of
Closing Comments
The foregoing is merely illustrative and not limiting, having been presented by way of example only. Although examples have been shown and described, it will be apparent to those having ordinary skill in the art that changes, modifications, and/or alterations may be made.
Although many of the examples presented herein involve specific combinations of method acts or system elements, it should be understood that those acts and those elements may be combined in other ways to accomplish the same objectives. With regard to flowcharts, additional and fewer steps may be taken, and the steps as shown may be combined or further refined to achieve the methods described herein. Acts, elements and features discussed only in connection with one embodiment are not intended to be excluded from a similar role in other embodiments.
For means-plus-function limitations recited in the claims, the means are not intended to be limited to the means disclosed herein for performing the recited function, but are intended to cover in scope any means, known now or later developed, for performing the recited function.
As used herein, “plurality” means two or more.
As used herein, a “set” of items may include one or more of such items.
As used herein, whether in the written description or the claims, the terms “comprising”, “including”, “carrying”, “having”, “containing”, “involving”, and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of” and “consisting essentially of”, respectively, are closed or semi-closed transitional phrases with respect to claims.
Use of ordinal terms such as “first”, “second”, “third”, etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.
As used herein, “and/or” means that the listed items are alternatives, but the alternatives also include any combination of the listed items.