WIDE-BANDWIDTH RADIO-FREQUENCY (RF) WINDOWS AND METHOD

A radio-frequency (RF) window comprises a first flange assembly including a first flange having a first flange thickness between a first surface and a second surface, and a first waveguide channel; and a first window element having a first window thickness and disposed in the first waveguide channel at a first location; and a second flange assembly stacked against the first flange assembly, the second flange assembly including a second flange having a second flange thickness between a third surface and a fourth surface, and a second waveguide channel; and a second window element having a second window thickness and disposed in the second waveguide channel at a second location, such that when the first flange assembly is stacked against the second flange assembly the second window element has a predetermined distance to the first window element, the predetermined distance selected based on a desired frequency band of operations.

TECHNICAL FIELD

This invention relates generally to radio frequency (RF) electronics, and more particularly provides wide-bandwidth radio-frequency (RF) window and methods.

BACKGROUND

Radio-frequency (RF) windows (irises) are used to separate and transport an electromagnetic wave from one medium to another. For example, in vacuum electronic devices, RF windows are used to enclose a vacuum envelope on one side of the RF window and to allow transportation of the electromagnetic wave from inside of the vacuum envelope to different atmospheric conditions (e.g., outside/external) on the other side of the RF window. For an RF device (e.g., RF circuit) operating across a wide band of frequencies, the RF window needs to match or exceed the wide band of operations of the RF device. Unfortunately, RF windows commonly serve as a limiting factor for transmitting a wide band of frequencies.

SUMMARY

Embodiments of the solution provide a wide-bandwidth radio-frequency (RF) window (iris), methods of manufacturing RF components for the wide-bandwidth RF window, and/or methods of assembling RF components to form the wide-bandwidth RF window. In some embodiments, the RF window comprises one or more flange assemblies, wherein each flange assembly includes a flange and one or more electromagnetic wave interface elements (one or more window elements) (e.g., one or more ceramic inserts) disposed inside of an opening in the flange. Each electromagnetic wave interface element may be made of ceramic and/or one or more other materials with low RF losses. In some embodiments, the flange may be made of metal and/or one or more other materials that allow for propagation and constraining of the electromagnetic wave.

RF performance of an RF window has been determined to be sensitive to the geometries (size, shape, orientation) and materials of the one or more electromagnetic wave interface elements in the waveguide channel. In embodiments having multiple electromagnetic wave interface elements in the waveguide channel, RF performance of the RF window has been determined to be sensitive to the positioning of the electromagnetic wave interface elements with respect to each other. Accordingly, by varying the geometries and/or materials of one or more of electromagnetic wave interface elements, the spacing between them, and their surrounding waveguide geometries, an RF window can be designed with a wide frequency band of operations coordinate with the operational needs of the RF device.

Some embodiments provide a simpler approach that reduces variables in designing and lowers precision demands in manufacturing a wide-bandwidth RF window with high quality RF performance. In some embodiments, each flange assembly may be designed to include a single electromagnetic wave interface element of the same or nearly the same size and shape as the waveguide. By generating the electromagnetic wave interface element of the same or nearly the same size and shape of the waveguide, the flange assembly generates a resonant mode at a certain frequency in the operating band of the waveguide. The size, shape and material properties of the electromagnetic wave interface element dictate the frequency and the quality factor of the resonant mode. By locating two electromagnetic wave interface elements with certain spacing therebetween, the RF window can be designed to provide a significantly wider bandwidth propagation mode. Accordingly, some embodiments may include two or more nearly identically sized (identically sized within design tolerances) precisely manufactured electromagnetic wave interface elements positioned in the waveguide channel with precise spacing away from each other to generate a desired band of operations for a given waveguide system.

To address the challenge of locating electromagnetic wave interface elements in the waveguide channel a precise distance away from each other, some embodiments use flanges formed to have precise thickness as well as electromagnetic wave interface elements formed to have precise thickness. In some embodiments, each of one or more electromagnetic wave interface elements may be positioned at one or more predetermined locations in the flange or inside one or more waveguides that are inserted in the flange. In some embodiments, standard WR-x type flange features may be manufactured (e.g., machined or etched) to have a desired size and thickness. The thickness of the flange can be controlled with extreme precision by lapping or grinding or starting with material sheet or plate stock rolled to precision.

In some embodiments, an electromagnetic wave interface element can be located or securely bonded to one end of the waveguide channel in the flange, flush with one of the flange surfaces, thereby providing a precise location mechanism for the electromagnetic wave interface element. Two or more nearly identical (identical within design tolerances) flange assemblies of this type can be stacked together. By designing the flange assemblies to have their surfaces tightly contact each other, the flange assemblies can be designed to generate precise spacing of the electromagnetic wave interface elements. As indicated above, the precise spacing may be calculated to provide an RF window with a desired band of operations for a given waveguide system. For an RF device (e.g., RF circuit) operating across a wide band of frequencies, the precise spacing may be calculated to provide the RF window that matches or exceeds the band of operations of the RF device.

In some embodiments, the electromagnetic wave interface elements may be ground to size and manufactured to be suitable for frequencies in microwave regions (3-30 GHz), in millimeter wave regions (30-300 GHz), in sub-terahertz regions (300 GHz-3 THz), and/or in terahertz regions (>3 THz). In some embodiments, each electromagnetic wave interface element can be inserted/bonded, grown, deposited or otherwise formed in the opening of the flange, or the flange can be formed around the electromagnetic wave interface elements. The RF window can be positioned between two waveguides, wherein each waveguide has a different atmospheric condition. In some embodiments, the electromagnetic wave interface elements may be disposed inside of the waveguide serving as an RF window to achieve proper bandwidth and RF losses while maintaining ultra-high vacuum on one side and other atmospheric conditions on the other side. The RF window can be used for applications in communications, radar, imaging, bio-chemistry, and other applications where access to instantaneous or sweeping bandwidth of frequencies is desired.

Alignment of the flange assemblies and/or other components such as external waveguides may be achieved using alignment features, such as pins or other clocking features in the flange itself, which may be configured to result in precise alignment of the electromagnetic wave interface elements.

According to some embodiments, the present invention provides a radio-frequency (RF) window, comprising a flange having a flange thickness and including a waveguide channel; and a window element having dimensions based on the waveguide channel and having a window thickness based on a desired resonant operation, the window element disposed in the waveguide channel at a first location.

The flange may be made of metal and the window element may be made of ceramic. The RF window may be used to separate different environments on both sides of the RF window. The waveguide channel may be a rectangular waveguide, rectangular waveguide with round corners, circular waveguide, elliptical waveguide, overmoded waveguide, ridged waveguide, or corrugated waveguide. The RF window may be configured for use with a passive waveguide. The RF window may be configured for use at microwave frequencies (3-30 GHz), millimeter wave frequencies (30-300 GHz), sub-THz frequencies (300 GHz-3 THz), or THz frequencies (>3 THz).

According to some embodiments, the present invention provides a radio-frequency (RF) window, comprising a flange including a first flange surface, a second flange surface, a flange thickness between the first flange surface and the second flange surface, and a waveguide channel; and a first window element disposed in the waveguide channel at a first location; and a second window element disposed in the waveguide channel at a second location, the first window element and the second window element being separated by a predetermined distance based on a desired frequency band of operations.

At least one of the first and second window elements may be made of ceramic. The first window element may be positioned with a first window surface flush with the first flange surface. The second window element may be positioned with a second window surface flush with the second flange surface. The first window element may be positioned with a first window surface recessed within the waveguide channel. The first window element may be disposed with a first window surface protruding from the first flange surface. The RF window may be used to separate different environments on both side of the RF window.

According to some embodiments, the present invention provides a flange assembly, comprising a flange having a first flange surface, a second flange surface, a flange thickness between the first flange surface and the second flange surface, and a waveguide channel; and a window element having a window thickness and disposed in the waveguide channel at a predetermined location, such that when the window element is positioned at the predetermined location the window element has a first distance to the first flange surface and a second flange distance to the second surface, at least one of the first distance or the second distance selected based on a desired frequency band of operations.

The flange may be made of metal and the window element may be made of ceramic. The flange assembly may be configured to be stacked against a second flange assembly. The flange assembly may be configured to be stacked with a nearly identical second flange assembly. The first distance may be zero and the second distance may be not zero. The first distance may be zero and the second distance may be zero.

According to some embodiments, the present invention provides a radio-frequency (RF) window, comprising a first flange assembly including a first flange having a first flange surface, a second flange surface, a first flange thickness between the first flange surface and the second flange surface, and a first waveguide channel; and a first window element having a first window thickness and disposed in the first waveguide channel at a first location; and a second flange assembly stacked against the first flange assembly, the second flange assembly including a second flange having a third flange surface, a fourth flange surface, a second flange thickness between the third flange surface and the fourth flange surface, and a second waveguide channel; and a second window element having a second window thickness and disposed in the second waveguide channel at a second location, such that when the first flange assembly is stacked against the second flange assembly the second window element has a predetermined distance to the first window element, the predetermined distance selected based on a desired frequency band of operations.

The first flange assembly may be nearly identical to the second flange assembly. The first flange thickness may be nearly identical to the second flange thickness. The first window thickness may be nearly identical to the second window thickness. Each of the first window element and the second window element may be made of ceramic. The first window element may be positioned into a waveguide component and waveguide component may be positioned in the first waveguide channel. The first window element may be positioned with a first window surface flush with the first flange surface. The second window element may be positioned with a second window surface flush with the second flange surface. The waveguide channel space between the first window element and the second window element may form a resonant cavity, and geometry of the resonant cavity may be based on a desired frequency band of operations. The RF window may be used to separate different environments on both sides of the RF window.

DETAILED DESCRIPTION

The following description is provided to enable a person skilled in the art to make and use various embodiments of the invention. Modifications are possible. The generic principles defined herein may be applied to the disclosed and other embodiments without departing from the spirit and scope of the invention. Thus, the claims are not intended to be limited to the embodiments disclosed, but are to be accorded the widest scope consistent with the principles, features and teachings herein.

Embodiments of the solution provide a wide-bandwidth radio-frequency (RF) window (iris), methods of manufacturing RF components for the wide-bandwidth RF window, and/or methods of assembling RF components to form the wide-bandwidth RF window. In some embodiments, the RF window comprises one or more flange assemblies, wherein each flange assembly includes a flange and one or more electromagnetic wave interface elements (one or more window elements) (e.g., one or more ceramic inserts) disposed inside of an opening in the flange. Each electromagnetic wave interface element may be made of ceramic and/or one or more other materials with low RF losses. In some embodiments, the flange may be made of metal and/or one or more other materials that allow for propagation and constraining of the electromagnetic wave.

RF performance of an RF window has been determined to be sensitive to the geometries (size, shape, orientation) and materials of the one or more electromagnetic wave interface elements in the waveguide channel. In embodiments having multiple electromagnetic wave interface elements in the waveguide channel, RF performance of the RF window has been determined to be sensitive to the positioning of the electromagnetic wave interface elements with respect to each other. Accordingly, by varying the geometries and/or materials of one or more of electromagnetic wave interface elements, the spacing between them, and their surrounding waveguide geometries, an RF window can be designed with a wide frequency band of operations coordinate with the operational needs of the RF device.

Some embodiments provide a simpler approach that reduces variables in designing and lowers precision demands in manufacturing a wide-bandwidth RF window with high quality RF performance. In some embodiments, each flange assembly may be designed to include a single electromagnetic wave interface element of the same or nearly the same size and shape as the waveguide. By generating the electromagnetic wave interface element of the same or nearly the same size and shape of the waveguide, the flange assembly generates a resonant mode at a certain frequency in the operating band of the waveguide. The size, shape and material properties of the electromagnetic wave interface element dictate the frequency and the quality factor of the resonant mode. By locating two electromagnetic wave interface elements with certain spacing therebetween, the RF window can be designed to provide a significantly wider bandwidth propagation mode. Accordingly, some embodiments may include two or more nearly identically sized (identically sized within design tolerances) precisely manufactured electromagnetic wave interface elements positioned in the waveguide channel with precise spacing away from each other to generate a desired band of operations for a given waveguide system.

To address the challenge of locating electromagnetic wave interface elements in the waveguide channel a precise distance away from each other, some embodiments use flanges formed to have precise thickness as well as electromagnetic wave interface elements formed to have precise thickness. In some embodiments, each of one or more electromagnetic wave interface elements may be positioned at one or more predetermined locations in the flange or inside one or more waveguides that are inserted in the flange. In some embodiments, standard WR-x type flange features may be manufactured (e.g., machined or etched) to have a desired size and thickness. The thickness of the flange can be controlled with extreme precision by lapping or grinding or starting with material sheet or plate stock rolled to precision.

In some embodiments, an electromagnetic wave interface element can be located or securely bonded to one end of the waveguide channel in the flange, flush with one of the flange surfaces, thereby providing a precise location mechanism for the electromagnetic wave interface element. Two or more nearly identical (identical within design tolerances) flange assemblies of this type can be stacked together. By designing the flange assemblies to have their surfaces tightly contact each other, the flange assemblies can be designed to generate precise spacing of the electromagnetic wave interface elements. As indicated above, the precise spacing may be calculated to provide an RF window with a desired band of operations for a given waveguide system. For an RF device (e.g., RF circuit) operating across a wide band of frequencies, the precise spacing may be calculated to provide the RF window that matches or exceeds the band of operations of the RF device.

In some embodiments, the electromagnetic wave interface elements may be ground to size and manufactured to be suitable for frequencies in microwave regions (3-30 GHz), in millimeter wave regions (30-300 GHz), in sub-terahertz regions (300 GHz-3 THz), and/or in terahertz regions (>3 THz). In some embodiments, each electromagnetic wave interface element can be inserted/bonded, grown, deposited or otherwise formed in the opening of the flange, or the flange can be formed around the electromagnetic wave interface elements. The RF window can be positioned between two waveguides, wherein each waveguide has a different atmospheric condition. In some embodiments, the electromagnetic wave interface elements may be disposed inside of the waveguide serving as an RF window to achieve proper bandwidth and RF losses while maintaining ultra-high vacuum on one side and other atmospheric conditions on the other side. The RF window can be used for applications in communications, radar, imaging, bio-chemistry, and other applications where access to instantaneous or sweeping bandwidth of frequencies is desired.

Alignment of the flange assemblies and/or other components such as external waveguides may be achieved using alignment features, such as pins or other clocking features in the flange itself, which may be configured to result in precise alignment of the electromagnetic wave interface elements.

FIG.1is a cross-sectional exploded side view of a passive or active radio-frequency (RF) waveguide system100, in accordance with some embodiments of the present invention. The RF waveguide system100includes a left waveguide102coupled via an RF window118to a right waveguide108. The left waveguide102includes a left waveguide channel116, left attachment channels122and left alignment channels124. The right waveguide108includes a right waveguide channel120, right attachment channels126and right alignment channels128. The RF window118includes a first flange assembly104aand a second flange assembly104b. The first flange assembly104aincludes a first flange105ahaving a first waveguide channel134a, first attachment channels132aand first alignment channels130a. The second flange assembly104bincludes a second flange105bhaving a second waveguide channel134b, second attachment channels132band second alignment channels130b. Alignment pins114may be inserted between the left alignment channels124and the first alignment channels130a, between the first alignment channels130aand the second alignment channels130b, and between the second alignment channels130band the right alignment channels128to align the components and their features, including the left waveguide channel116, the first waveguide channel134a, the second waveguide channel134b, and the right waveguide channel120, with each other. After establishing proper alignment, screws110may be inserted across the left attachment channels122, the first attachment channels132a, the second attachment channels132b, and the right attachment channels126and tightened using bolts112to secure the components together. Other alignment mechanisms or attachment mechanisms may additionally or alternatively be used. In some embodiments, the attachment mechanism and the alignment mechanism may be the same mechanism.

The first flange assembly104amay include a first electromagnetic wave interface element106a(which may be or include a first ceramic insert) positioned on the right side of the first waveguide channel134a, such that the right surface of the first electromagnetic wave interface element106ais flush with the right surface of the first flange105a. Although shown as positioned flush with the right surface of the first flange105a, the first electromagnetic wave interface element106amay be positioned in a different location, such as flush with the left surface of the first flange105aor at an inner position in the first waveguide channel134a(with predesigned distances to the left and/or right surfaces of the first flange105a). To assist with positioning the first electromagnetic wave interface element106aat a position located within the first waveguide channel134a, the first waveguide channel134amay include first alignment features, such as one or more fixed protrusions or protrusions created by one or more alignment pins that may be removed or partially withdrawn after positioning and bonding of the first electromagnetic wave interface element106a.

The second flange assembly104bmay include a second electromagnetic wave interface element106b(which may be or include a second ceramic insert) positioned on the right side of the second waveguide channel134b, such that the right surface of the second electromagnetic wave interface element106bis flush with the right surface of the second flange105b. Although shown as positioned flush with the right surface of the second flange105b, the second electromagnetic wave interface element106bmay be positioned in a different location, such as flush with the left surface of the second flange105bor at an inner position in the second waveguide channel134b(with predesigned distances to the left and/or right surfaces of the second flange105b). To assist with positioning the second electromagnetic wave interface element106bat a position located within the second waveguide channel134b, the second waveguide channel134bmay include second alignment features, such as one or more fixed protrusions or protrusions created by alignment pins that may be removed or partially withdrawn after positioning and bonding of the second electromagnetic wave interface element106b. In some embodiments, the second flange assembly104bmay be nearly identical (identical within design tolerances) to the first flange assembly104a.

The sizes and shapes of the left waveguide channel116, the first waveguide channel132a, the second waveguide channel132band the right waveguide channel120may be the same or may vary, depending on the design and desired RF performance. The geometries of the first electromagnetic wave interface element106aand the second electromagnetic wave interface element106bmay be the same or may vary, depending on the design and desired RF performance. The distance between the first electromagnetic wave interface element106aand the second electromagnetic wave interface element106bmay depend on the design and desired RF performance. Although the first flange assembly104aand the second flange assembly104bare shown as nearly identical, they need not be. For example, the first flange assembly104amay be thinner, which as long as the first electromagnetic wave interface element106aremains on the right surface may not affect the spacing between the first electromagnetic wave interface element106aand the second electromagnetic wave interface element106b. Further, the materials used for the first electromagnetic wave interface element106aand the second electromagnetic wave interface element106bmay be the same or may vary, depending on the design and desired RF performance. Although shown as an integral structure, the flange105aand/or the flange105bmay be formed from multiple sections affixed together.

FIG.2is a cross-sectional side view of the RF window118, in accordance with some embodiments of the present invention. The RF window118includes the first flange assembly104aand the second flange assembly104bwith the right surface of the first flange assembly104atightly positioned against the left surface of the second flange assembly104b. The first flange assembly104aincludes the first waveguide channel134a, first attachment channels132aand first alignment channels130a. The second flange assembly104bincludes the second waveguide channel134b, second attachment channels132band second alignment channels130b. Alignment pins114may have been inserted between the first alignment channels130aand the second alignment channels130bto align the components and their features, including the first waveguide channel134aand the second waveguide channel134bwith each other.

As shown, because the first flange assembly104aincludes the first electromagnetic wave interface element106adesigned with precise dimensions and positioned on the right side of the first waveguide channel134a, such that the right surface of the first electromagnetic wave interface element106ais flush with the right surface of the first flange assembly104a, and because the second flange assembly104bincludes the second electromagnetic wave interface element106bdesigned with precise dimensions and positioned on the right side of the second waveguide channel134b, such that the right surface of the second electromagnetic wave interface element106bis flush with the right surface of the second flange assembly104b, a resonant cavity202with precise dimensions may be generated between the first electromagnetic wave interface element106aand the second electromagnetic wave interface element106bafter stacking them. In some embodiments, RF performance of the RF window118may be based on the geometry of the resonant cavity202or primarily the distance between the first electromagnetic wave interface element106aand the second electromagnetic wave interface element106b.

As indicated above, although shown as positioned flush with the right surface of the first flange105a, the first electromagnetic wave interface element106amay be positioned in a different location, such as flush with the left surface of the first flange105a, at an inner position in the first waveguide channel134aor protruding from either side. Further, as indicated above, although shown as positioned flush with the right surface of the second flange104, the second electromagnetic wave interface element106bmay be positioned in a different location, such as flush with the left surface of the second flange104, at an inner position in the second waveguide channel134bor protruding from either side. It will be noted that the same geometry of the resonant cavity202may be achieved with the first electromagnetic wave interface element106aand the second electromagnetic wave interface element106beach placed at a different position in their respective waveguide channels of their respective flanges104aand104b. Further, the geometries of the first electromagnetic wave interface element106aand/or the second electromagnetic wave interface element106bmay be different, and form the resonant cavity202with the same or different geometry. Still further, the same resonant cavity can be formed using the first electromagnetic wave interface element106aand the second electromagnetic wave interface element106beach placed at a different position in a single flange.

FIG.3is a front view of the first flange assembly104aor the second flange assembly104bof the RF window118, in accordance with some embodiments of the present invention. The first flange assembly104aor the second flange assembly104bincludes a round face having four attachment channel openings302to four attachment channels132a/132b, four alignment channel openings304to four alignment channels130a/130b, and a first waveguide opening306to the first waveguide channel132a/132b. As shown, the each waveguide134aor134bis shown as rectangular, other waveguide types are possible, such as round, square, rectangular with round corners, elliptical, ridged, overmoded, and corrugated.

FIG.4is a cross-sectional side view of an RF window400having a single flange assembly, in accordance with some embodiments of the present invention. The RF window400includes a flange402and two electromagnetic wave interface elements404aand404binside the waveguide channel410. As shown and described above, the flange402may include attachment channels406and alignment channels408.

In some embodiments, the first electromagnetic wave interface element404amay be designed with precise dimensions and positioned on the left side of the waveguide channel410such that its left surface is flush with the left surface of the flange402. Similarly, in some embodiments, the second electromagnetic wave interface element404bmay be designed with precise dimensions and positioned on the right side of the waveguide channel410such that its right surface is flush with the right surface of the flange402. That way, based on the thickness of the flange402and the thicknesses of the two electromagnetic wave interface elements404aand404b, the two electromagnetic wave interface elements404aand404bcan be precisely spaced apart to form a resonant cavity412with precise dimensions.

As indicated above, although shown as positioned flush with the left surface of the flange402, the first electromagnetic wave interface element404amay be positioned in a different location, such as at a left inner position in the waveguide channel410or protruding therefrom. Similarly, although shown as positioned flush with the right surface of the flange402, the second electromagnetic wave interface element404bmay be positioned in a different location, such as at a right inner position in the waveguide channel410or protruding therefrom. It will be noted that the same geometry of the resonant cavity412may be achieved with the first electromagnetic wave interface element404aand the second electromagnetic wave interface element404beach placed at a different position in the waveguide channel410. Further, the geometries of the first electromagnetic wave interface element404aand/or the second electromagnetic wave interface element404bmay differ, and form the resonant cavity412with the same or different geometry.

FIG.5is a flowchart illustrating a method500of forming a flange, e.g., flange105a,105bor402, in accordance with some embodiments of the present invention. Method500begins in step502with the step of obtaining flange material, e.g., a metal and/or other material that allows for propagation and constraining of the electromagnetic wave. In step504, a form having a predetermined thickness is generated from the flange material. In step506, a waveguide channel, e.g., waveguide channel134a,134bor410is generated in the form. In step508, optional attachment channels, e.g., attachment channels132a,132bor406, and/or optional alignment channels, e.g., alignment channels130a,130bor408, may be generated in the form.

FIG.6is a flowchart illustrating a method600of assembling an RF window, e.g., RF window400, using a single flange, e.g., flange402, in accordance with some embodiments of the present invention. Method600begins in step602with a first electromagnetic wave interface element, e.g., first electromagnetic wave interface element404a, being inserted into the waveguide channel, e.g., the waveguide channel410. In some embodiments, the first electromagnetic wave interface element may be positioned on the left side of the waveguide channel. Although shown as positioned flush with the left surface of the flange, the first electromagnetic wave interface element may be positioned at a different location, such as at an inner position in the waveguide channel or protruding therefrom. In step604, a second electromagnetic wave interface element, e.g., second electromagnetic wave interface element404b, is inserted into the waveguide channel, e.g., the waveguide channel410, at a predetermined spacing from the first electromagnetic wave interface element. In some embodiments, the second electromagnetic wave interface element may be positioned on the right side of the waveguide channel. Although shown as positioned flush with the right surface of the flange, the second electromagnetic wave interface element may be positioned at a different location, such as at an inner position in the waveguide channel or protruding therefrom. In some embodiments, the pair of electromagnetic wave interface elements form a resonant cavity therebetween. To achieve a particular spacing of the first electromagnetic wave interface element and the second electromagnetic wave interface element, each of the flange, the first electromagnetic wave interface element and the second electromagnetic wave interface element may be formed with precise dimensions (including thickness).

FIG.7is a flowchart illustrating a method700of assembling an RF window, e.g., RF window118, using multiple flange assemblies, e.g., flange assemblies104aand104b, in accordance with some embodiments of the present invention. Method700begins in step702with a first electromagnetic wave interface element, e.g., first electromagnetic wave interface element106abeing inserted into a first waveguide channel, e.g., waveguide channel134a, of a first flange, e.g., first flange105a, at a first predetermined location. In some embodiments, the predetermined location may be positioned on the right side of the first waveguide channel, such that the right surface of the first electromagnetic wave interface element is flush with the right surface of the first flange. Although shown as positioned flush with the right surface of the first flange, the first electromagnetic wave interface element may be positioned at a different location, such as flush with the left surface of the first flange, at an inner position in the first waveguide channel or protruding from one of the ends.

In step704, a second electromagnetic wave interface element, e.g., second electromagnetic wave interface element106bis inserted into a second waveguide channel, e.g., waveguide channel134b, of a second flange, e.g., second flange105b, at a second predetermined location. In some embodiments, the second predetermined location may be positioned on the right side of the second waveguide channel, such that the right surface of the second electromagnetic wave interface element is flush with the right surface of the second flange. Although shown as positioned flush with the right surface of the second flange, the second electromagnetic wave interface element may be positioned at a different location, such as flush with the left surface of the second flange, at an inner position in the second waveguide channel or protruding from one of the ends. The first predetermined location need not be the same location as the second predetermined location, although they may be for ease of manufacturing.

In step706, the first flange assembly, e.g., first flange assembly104a, and the second flange assembly, e.g., second flange assembly104b, are aligned and assembled, e.g., stacked, together, thereby causing a predetermined distance between the first electromagnetic wave interface element and the second electromagnetic wave interface element.

FIG.8Ais a cross-sectional side view of an electromagnetic wave interface element802in a waveguide804, in accordance with some embodiments of the present invention.

FIG.8Bis a graph852of a reflection (S4) coefficient relative to frequency (f) for the electromagnetic wave interface element802, in accordance with some embodiments of the present invention. As shown, the electromagnetic wave interface element802has a narrowband resonance at frequency f0. Frequencies with low reflection coefficient are frequencies where the RF wave is transmitted.

FIG.9Ais a cross-sectional side view of first and second identical electromagnetic wave interface elements902and904in the waveguide804, in accordance with some embodiments of the present invention.

FIG.9Bis a graph952of a reflection coefficient relative to frequency for the first electromagnetic wave interface element902, in accordance with some embodiments of the present invention. As shown, the first electromagnetic wave interface element902has a narrowband resonance at frequency f0.

FIG.9Cis a graph954of a reflection coefficient relative to frequency for the second electromagnetic wave interface element904, in accordance with some embodiments of the present invention. As shown, the second electromagnetic wave interface element904also has a narrowband resonance at frequency f0. Around the resonant frequency, the reflection coefficient is low and the RF wave is transmitted.

Because as shown inFIGS.9B and9Cboth the first and second identical electromagnetic wave interface elements902and904have good resonance at f0, the combination will also have good resonance at frequency f0.

FIG.9Dis a graph962of a reflection coefficient relative to frequency for the first electromagnetic wave interface element902, in accordance with some embodiments of the present invention. Notably, the first electromagnetic wave interface element902will have a large reflection at frequency f1.

FIG.9Eis a graph964of a reflection coefficient relative to frequency for the second electromagnetic wave interface element904, in accordance with some embodiments of the present invention. Notably, like the first electromagnetic wave interface element902, the second electromagnetic wave interface element904will also have a large reflection at frequency f1.

FIG.9Fa cross-sectional side view of the first and second identical electromagnetic wave interface elements902and904spaced apart by distance L in the waveguide804and further illustrating transmission and reflection paths of an electromagnetic wave at frequency f1, in accordance with some embodiments of the present invention. As shown, an electromagnetic wave970at frequency f1approaches the first electromagnetic wave interface element902. A first portion972reflects, and a second portion974transmits therethrough. The second portion974that transmits therethrough approaches the second electromagnetic wave interface element904. Of the second portion974that transmits through the first electromagnetic wave interface element902, a third portion976reflects off the second electromagnetic wave interface element904and a fourth portion980transmits therethrough. Of the third portion976that reflects, a fifth portion978transmits through the first electromagnetic wave interface element902. The spacing L between the first electromagnetic wave interface element902and the second electromagnetic wave interface element904may be designed so that the first portion972that reflects from the first electromagnetic wave interface element902and the fifth portion978(the returning portion978) that transmits through the first electromagnetic wave interface element902are 180 degrees out of phase and cancel each other at frequency f1. This configuration can be analyzed by taking the S-parameters of each window block individually, and doing a cascaded S-parameter analysis, with an additional straight waveguide between them for phase length.

FIG.9Gis a graph990of a reflection coefficient relative to frequency for the combination of the first and second electromagnetic wave interface elements902and904, in accordance with some embodiments of the present invention. As shown, an RF window with the first and second identical electromagnetic wave interface elements902and904spaced apart by distance L will have two frequencies f0and f1with low reflection.

FIG.10is a graph of a series of reflection coefficients relative to frequency for the combination of the first and second electromagnetic wave interface elements902and904by varying the spacing L between them, in accordance with some embodiments of the present invention. As shown, as the spacing L is changed, the frequency at which the reflections changes, thereby changing the band of operating frequencies of an RF window. Although the above has been shown with two identical electromagnetic wave interface elements spaced apart by distance L, there can be more than two electromagnetic wave interface elements to further modify the band of operating frequencies. Further, the electromagnetic wave interface elements need not be identical. Still further, the waveguide need not be straight or have consistent cross-sectional shape. Other variations are also possible.

The foregoing description of the preferred embodiments of the present invention is by way of example only, and other variations and modifications of the above-described embodiments and methods are possible in light of the foregoing teaching. The embodiments described herein are not intended to be exhaustive or limiting. The present invention is limited only by the following claims.