EP2151007A1

EP2151007A1 - Low-loss impedance coaxial interface for integrated circuits

Info

Publication number: EP2151007A1
Application number: EP08747243A
Authority: EP
Inventors: Rob Zienkewicz; Dave Harper; Ken Buer; John Decamp; Dean Cook; Charles Woods
Original assignee: Viasat Inc
Current assignee: Viasat Inc
Priority date: 2007-05-02
Filing date: 2008-04-30
Publication date: 2010-02-10
Also published as: WO2008137477A1

Abstract

In general, in accordance with one exemplary aspect of the present invention, a low-loss interface for connecting an integrated circuit such as a monolithic microwave integrated circuit to an energy transmission device such as a waveguide is disclosed. In one exemplary embodiment, the interface comprises a pin seated within an assembly that forms a hermetic sealed, coaxial structure to prevent signal loss at increasing frequencies. In another exemplary embodiment, the interface comprises a coaxial structure such as a coaxial cable that directly connects the monolithic microwave circuit to the waveguide to transmit energy signals such as microwave energy with minimal loss.

Description

LOW-LOSS IMPEDANCE COAXIAL INTERFACE FOR INTEGRATED

CIRCUITS

Field of Invention The present invention generally relates to an interface for use, for example, between an integrated circuit and a waveguide. More particularly and according to one exemplary embodiment, the present invention relates to an interface comprised of a low-loss pin and pin assembly that transports signals from, for example, an integrated circuit, such as a monolithic microwave integrated circuit, to a waveguide. In another exemplary embodiment, the present invention also relates to an interface comprised of a low-loss pin and pin assembly that transports energy signals from, for example, an integrated circuit, such as a monolithic microwave integrated circuit, to a waveguide.

Background of the Invention

There are numerous circuits and other electronic devices that produce energy waves such as electromagnetic waves and microwaves. These circuits produce energy waves that are delivered to a destination through different wires, guides, and other mediums.

Energy waves can be difficult to control on various circuits, cables, wires, and other mediums that transport the energy waves because these mediums are "lossy." Lossy materials and mediums loose energy by radiation, attenuation, or dissipation as heat. By being lossy, a portion of the signal is lost as it travels through the circuits, wires, and other mediums. Stated another way, a signal entering a lossy material will be greater at the point of entry than at the point of exit. Microwave energy is particularly difficult to control as many of the materials and mediums that transport microwave energy are lossy. One exemplary circuit that generates and transports microwaves is a "monolithic microwave integrated circuit" or "MMIC." Lost signal waves are unusable and decrease the efficiency of a MMIC as the signal strength decreases due to loss. Generally, the higher the frequency of the microwave, the more lossy the transmission medium and more inefficient the circuit. In certain applications, even signal losses that reduce the signal small amounts, such as 1/10 of a decibel, may result in a significant performance loss. One exemplary application where loss from energy waves such as microwaves is problematic is a power amplifier. One structure used to reduce lossiness is a waveguide. Waveguides are structures that guide energy waves with minimal signal loss. Unfortunately, signal loss is still problematic with certain waves because the connection or interface between the circuit generating the energy waves and the waveguide can be lossy itself. This is especially an obstacle with a MMIC generating microwaves. Moreover, impedance miss-matches also cause signal losses. For example, the impedance of the MMIC, for example fifty ohms, may not match the impedance of the connected waveguide, for example two hundred and seventy ohms. In this example, an interface between the waveguide and MMIC attempts to match the fifty ohm impedance of the MMIC with the two hundred and seventy ohm impedance of the waveguide. These types of interfaces are known generally as "impedance matching interfaces" or "impedance matching and transforming interfaces." Throughout, the term "interface" is meant to denote an "impedance matching interface" or "impedance matching and transforming interface."

Current interfaces between a MMIC and waveguide comprise numerous structures that include wirebonds, microstrips, pins, and other devices to connect a circuit to a waveguide or another structure. These interfaces also attempt to match and transform the impedance of the MMIC to the impedance at the waveguide. However, current impendence matching interfaces between an integrated circuit such as a MMIC and a waveguide still have an unacceptable amount of loss. Besides impedance, circuits such as MMICS also have different modes of energy wave propagation compared to other energy transporting devices such as a waveguide. For example, a MMIC may have a mode of energy wave propagation of quasi-TEM (Transverse Electromagnetic) while a waveguide has a mode of energy wave propagation of TEio (Transverse Electric, 10). These differing modes of energy wave propagation also contribute to loss in traditional interfaces. Impedance matching interfaces also match the differing modes of energy wave propagation to minimize loss.

Present interfaces between a MMIC and waveguide comprise numerous structures that include wirebonds, microstrips, pins, and other devices to connect a circuit to a waveguide or another structure. These interfaces also attempt to match and transform the impedance of the MMIC to the impedance at the waveguide. However, present impedance and mode of energy wave propagation matching interfaces between an integrated circuit such as a MMIC and a waveguide still have an unacceptable amount of loss. Certain present impedance matching interfaces comprise devices with coaxial structures. Specifically, coaxial cable is used as an impedance matching interface depending on how it is used. Specifically, coaxial structures are utilized as impedance matching interfaces when their impedance is somewhere in between the impedance of the devices they are connecting. For example, a MMIC may have an impedance of fifty ohms and a waveguide may have an impedance of two hundred and seventy ohms. A coaxial structure may be used as part of the interface connecting the MMIC to the waveguide with an impedance of one hundred ohms. This impedance of one hundred ohms helps reduce loss of energy traveling from the fifty ohm MMIC to the two hundred and seventy ohm waveguide. Loss is reduced because the impedance of the devices transporting the energy changes much more gradually (fifty-hundred-two hundred and seventy) than merely connecting the MMIC to the waveguide (fifty-two hundred and seventy).

Despite their impedance matching abilities, many known impedance matching interfaces are complex as they comprise several different parts and require numerous mechanisms to be connected to circuits or other energy transmission devices. Further, known coaxial impedance matching interfaces are not used to directly connect an integrated circuit such as a MMIC to another energy transmission device such a waveguide.

One present interface that reduces loss is disclosed in co-pending, commonly owned U.S. Patent Application Serial No. 11/853,287 entitled low loss interface which is also incorporated in its entirety by reference. This application also disclosed an excellent impedance matching device, but this device has numerous parts. It would be desirable to provide an impedance matching interface with a coaxial structure that directly connects a circuit such as a MMIC to a waveguide.

Therefore, it would be advantageous to provide an interface between an integrated circuit, such as a MMIC, and a waveguide, or other structure that reduces signal loss. It would also be advantageous to produce an interface that reduced loss that was inexpensive and easy to manufacture, particularly one that was constructed from parts that were commercially available.

Therefore, it would also be advantageous to provide a coaxial interface that directly connected an integrated circuit, such as a MMIC, to a waveguide, or other structure that reduces signal loss by matching the impedance. It would also be advantageous to produce a coaxial interface that reduced loss that was inexpensive and easy to manufacture, particularly one that was constructed from parts that were commercially available such a coaxial cable or other type of coaxial materials.

Summary of the Invention In general, in accordance with one exemplary aspect of the present invention, an interface for connecting an integrated circuit such as a MMTC to a waveguide is provided. In one exemplary embodiment, the interface comprises a pin placed within an assembly which is configured to reduce signal loss. In another aspect of the present invention, two or more beads connect the pin to the assembly to further define the space. In yet another aspect of one exemplary embodiment, one bead is formed from glass to form a hermetic seal and the interface is connected to the integrated circuit.

In accordance with another exemplary embodiment of the present invention, a coaxial interface for directly connecting an integrated circuit such as a MMIC to a waveguide is provided. In one exemplary embodiment, the interface is a coaxial cable that directly connects the integrated circuit to the waveguide. The coaxial structure has an impedance in between that of the integrated circuit and waveguide and assists in transforming the impedance between the integrated circuit and waveguide to reduce loss. In other exemplary embodiments, other coaxial structures are used such as coaxial pins to directly connect an integrated circuit such as a MMIC to a waveguide or other energy transmitting structure or device.

Brief Description of the Drawing

A more complete understanding of the present invention may be derived by referring to the detailed description and claims when considered in connection with the Figures, where like reference numbers refer to similar elements throughout the Figures, and:

FIG. 1 illustrates an exemplary schematic diagram of the interface in accordance with an exemplary embodiment of the present invention;

FIG. 2 illustrates an exemplary schematic diagram of the pin and beads apart from the assembly in accordance with an exemplary embodiment of the present invention; FIG. 3 illustrates an exemplary schematic diagram of the assembly apart from the pin and beads in accordance with an exemplary embodiment of the present invention;

FIG. 4 illustrates an exemplary schematic diagram of a side view of the interface in accordance with an exemplary embodiment of the present invention; and FIG. 5 illustrates an exemplary schematic diagram of a top view of the interface shown in FIG. 4 in accordance with an exemplary embodiment of the present invention.

Detailed Description of Exemplary Embodiments of the Invention In accordance with one aspect of the present invention, an interface for connecting an integrated circuit to an energy transmission device such as a waveguide is disclosed. In accordance with another aspect of the present invention, a method of manufacturing an interface is disclosed. Throughout, the interface according to this exemplary embodiment of the present invention will be referred to as interface 10. With reference to FTGS. 1 -3, and in accordance with one exemplary embodiment of the present invention, interface 10 is a low-loss interface comprising a coaxial structure that is configured to transmit energy from one device to another. It should be noted that the term "low-loss" refers to the ability to reduce signal loss as discussed above, hi an exemplary embodiment, interface 10 connects an integrated circuit 1 1 to another energy transmission device 13 and matches the impedance at integrated circuit 11 to the impedance at energy transmission device 13. Furthermore, interface 10 can be any device configured to transmit energy and match impedance between two or more energy producing or transmission devices.

In one exemplary embodiment, circuit 11 is a monolithic microwave integrated circuit (MMIC). In another exemplary embodiment, circuit 11 comprises discrete components on a circuit board such as memory devices, power sources, light emitting diodes, and the like. Circuit 11 can be any type of circuit, circuit board, printed circuit board, integrated circuit, or other type of device or medium that produces or transfers energy waves. As such, the term "circuit" is not limited to devices with discrete components on a circuit board but rather includes any device that produces or transmits energy waves such as wires, cables, or waveguides. Similarly, energy transmission device 13 can be any type of device or medium configured to produce or transport energy. In one exemplary embodiment, energy transmission device 13 is a waveguide that guides microwave energy waves. In another exemplary embodiment, energy transmission device 13 comprises wires, cables or other devices configured to transport and guide energy waves from one source to another.

In one exemplary embodiment, interface 10 is a coaxial structure comprising a pin 12 that connects to circuit 1 1 on one end and energy transmission device 13 on the other end. Pin 12 is disposed within an assembly 14. A set of beads 16, 18 contact pin 12 and assembly 14 and further define a space 20 between pin 12 and assembly 14 which helps impart the coaxial structure to interface 10. In one exemplary embodiment, an insulator 22 contacts pin 12 and circuit 11 and a wire connector 24 connects pin 12 to circuit 11. Pin 12 is a low-loss pin comprising a low-loss conductive medium. In an exemplary embodiment, pin 12 is a feedthru pin, such as a microwave feedthra pin comprising a low- loss conductive material. In one exemplary embodiment, pin 12 comprises two ends with one end configured to be connected to energy transmission device 13 and the other opposing end connected to circuit 11. Pin 12 can be connected to circuit 11 and energy transmission device 13 by mere contact without adhesives or the like or it can be connected by an adhesive, soldering, or attachment devices such as pins and screws. In one exemplary embodiment, pin 12 is configured to be connected to circuit 11 by wire connector 24.

In one exemplary embodiment, pin 12 is a relatively long, narrow member that is round. Other shapes of pin 12 in other exemplary embodiments of the present invention comprise an oval, square, rectangular shaped, irregularly shaped or the like. In one exemplary embodiment, pin 12 is one continuous shape from one end to the other. However, in other exemplary embodiments, half of pin 12 can be round while the other half is another shape (such as an oval) resulting in pin 12 having two shaped regions. Numerous different shaped regions can be located along pin 12. With reference to FIGS. 1-2, and in one exemplary embodiment, one end of pin 12 can be tapered and rests on insulator 22. In this exemplary embodiment, pin 12 is configured to have a flat portion 17 configured to receive wire connector 24, e.g. a bond wire. Further, flat portion 17 may be prepared with an ohmic material for forming a better connection with wire connector 24. In other exemplary embodiments, the end of pin 12 can be non-tapered and have the same radius as the rest of pin 12. In other exemplary embodiments, the end of pin 12 that contacts insulator 22 can be larger than the remaining portion of pin 12.

Furthermore, pin 12 can be any length or radius. In accordance with one aspect of the present invention, the length and radius of pin 12 are selected based on the impedance of pin 12 and energy transmission device 13. Further, the length and radius of pin 12 may depend on the frequency of the energy being transmitted, or the physical properties (size and overall dimensions) of pin 12 and energy transmission device 13. In one exemplary embodiment, where the impedance at circuit 1 1 is fifty ohms, pin 12 has a radius of 0.086 inches. Any other radius of pin 12 configured to facilitate impedance matching, appropriate for the frequency of the energy traveling through pin 12, and physically appropriate to match the physical properties of circuit 11 and energy transmission device 13 can be used and fall within the scope of the present invention. In one exemplary embodiment, pin 12 comprises or is formed of a single conductive metal. For example, pin 12 may be solid gold, silver, copper, and/or other similar materials with low resistance. Furthermore, the conductive material may be any material configured to conduct the energy being transmitted through pin 12.

In another exemplary embodiment, pin 12 comprises a core formed from a rigid material and the core is coated (or partially coated) with a conductive material. For example, pin 12 may comprise a rigid material such as a Kovar® alloy produced by the Westinghouse Electric and Manufacturing Company of Pittsburgh, Pennsylvania. The rigid alloy gives pin 12 strength and is coated with conductive materials such as gold, silver, or copper which is configured to conduct energy along pin 12. Furthermore, any rigid material (certain exemplary materials, include, but are certainly not limited to, metal, alloy, or plastic) configured to impart strength to pin 12 and/or configured to be plated or coated in a conductive material can be used. The conductive material may be the same as described above in the single conductive material embodiment.

Pin 12 can be custom manufactured or it can be a commercially available feedthru pin that is easily available to the public. In an exemplary embodiment, pin 12 is a microwave feedthru pin that is commercially available from numerous sources including Special Hermetic Products, Inc. of Wilton, New Hampshire, Thunderline Z (a division of Emerson, Inc.) of Hampstead, New Hampshire or Tyco Electronics of Wilmington, Delaware. In accordance with an exemplary embodiment of the present invention, pin 12 is disposed within assembly 14. In one exemplary embodiment, assembly 14 comprises a metal core that is coated with a low-loss metal. In another exemplary embodiment, assembly 14 comprises a plastic or an alloy to impart strength to assembly 14 that is covered in a low-loss metal. Certain exemplary low-loss metals are silver, gold, and copper. An exemplary alloy is a Kovar® alloy which is covered or coated with a low-loss material.

With reference to FIG. 3, assembly 14 can comprise a single piece of material or it can comprise two or more pieces of material. In one exemplary embodiment, assembly 14 comprises a metal block that has been drilled out to form a space 15. In another exemplary embodiment, assembly 14 is formed from two or more pieces of conductive material that are joined together by welding, soldering, or other connectors such as screws, bolts, pins or adhesives. In other exemplary embodiments, any materials configured to facilitate impedance matching and reduce signal loss can be used to construct assembly 14. With reference again to FIG. 3, in accordance with an exemplary embodiment, assembly 14 comprises two openings. One opening 26 may be smaller and configured to be disposed next to energy transmission device 13. The other opening 28 may be larger and configured to be located next to circuit 11. As is explained below, openings 26 and 28 help define space 20 together with pin 12 and beads 16, 18. The size of opening 26 may be selected based on various factors such as (but not limited to) the size of pin 12, the size of space 20 desired, the size of bead 18, and to facilitate impedance matching and to reduce loss. The diameter of opening 28 may be selected based on various factors such as (but not limited to) the size of pin 12, the size and related depth of energy transmission device 13, the size of bead 16, and to facilitate impedance matching and reduce loss. Beads 16 and 18 are disposed within and contact assembly 14. Each bead 16, 18 further comprises a center hole or other opening which enables beads 16, 18 to slide onto and concentrically surround pin 12. Similar to openings 26 and 28, the diameter of beads 16, 18 varies depending on the application interface 10 is used for and various other factors such as (but not limited to) the size of pin 12, and the size of space 20. Beads 16, 18 create space 20 when they are attached to pin 12 and disposed within assembly 14. In one exemplary embodiment, bead 16 is larger than bead 18.

In one exemplary embodiment, bead 16 is the larger of the two beads and comprises a non-conductive material such as glass. In other exemplary embodiments, bead 16 comprises a Teflon® material produced by the E.I. DuPont De Nemours Company of Wilmington, Delaware. In other exemplary embodiments, bead 16 comprises non- conductive plastics, metals, or alloys. Any non-conductive material now known or developed in the future can be used for beads 16, 18 and fall within the scope of the present invention.

As depicted in this exemplary embodiment, bead 18 is smaller than bead 16 and is placed adjacent to energy transmission device 13. Bead 18 is used to secure pin 12 within assembly 14 and hold it in place in an exemplary embodiment, hi other exemplary embodiments, bead 18 can be eliminated. As noted herein, in one exemplary embodiment, bead 18 comprises a Teflon® material. Further, as depicted, a notch 23 is defined within assembly 14 to allow bead 16 to fit completely within assembly 14 and not slide into energy transmission device 13. In other exemplary embodiments, notch 23 is eliminated and bead 18 is completely flush with the edge of assembly 14. In other exemplary embodiments, bead 18 protrudes from assembly 14 into energy transmission device 13. In an exemplary embodiment, interface 10 is configured to form a hermetic seal between the space containing energy transmission device 13 and the space containing circuit 1 1. This seal is formed by sealing bead 16 to assembly 14. This hermetic seal prevents water, dust, air, and other pollutants from entering space 20.

As noted above, pin 12 and assembly 14 define space 20 which is further defined by beads 16, 18. Space 20 further reduces signal loss from interface 10. As depicted, space 20 concentrically surrounds pin 12 and extends from bead 16 to bead 18 in one exemplary embodiment. The size of space 20 is directly related to application interface 10 is used for, the frequency of the energy being transmitted, and the impedance of circuit and energy transmission device 13. The size of space 20 can also be directly related to physical properties of circuit 11 and energy transmission device 13 similarly to the size of beads 16, 18 and their respective openings 26, 28.

In one exemplary embodiment, one end of pin 12 rests on insulator 22. Insulator 22 can comprise any type of insulating material and can be any size. However, in one exemplary embodiment, insulator 22 is a thin insulator comprising a piece of insulating tape. In another exemplary embodiment, insulator 22 comprises a thin layer of liquid epoxy which has insulating properties. Further, in these exemplary embodiments, insulator 22 is two thousandths of an inch or smaller. In other exemplary embodiments, other insulators of various sizes and constructions are used and still fall within the scope of the present invention. Insulator 22 may be configured to prevent pin 12 from bending. Furthermore, insulator 22 may comprise material that is configured to separate pin 12 from the environment.

In one exemplary embodiment, wire connector 24 further connects interface 10 to circuit 1 1. hi certain exemplary embodiments, wire connector 24 is a wire bond connector comprising gold, aluminum, copper or a combination of two or more of these metals. Further, wire connector 24 is attached to flat edge 17 of pin 12. Certain exemplary types of wire bonds comprise, but are not limited to, ball bonds and wedge bonds. In other exemplary embodiments, other metals or materials are used to construct wire connector 24. An exemplary method of manufacturing interface 10 will now be discussed. While specific materials and techniques are mentioned herein, other materials, parts, supplies, and techniques can certainly be used to manufacture interface 10 and fall within the scope of the present invention. This exemplary method of manufacturing interface 10 first comprises the step of producing assembly 14. Assembly 14 comprises a metal block covered with another low- loss material such as a metal or alloy. In other exemplary embodiments assembly 14 is a metal block which is non-coated and constructed entirely from a low-loss material. The metal block is drilled out creating a cavity which forms space 15. Ln another exemplary embodiment, assembly 14 comprises two or more pieces of material that are attached together as described above. The size of space 15 is determined based on the application that interface 10 will be used for.

Part of the manufacturing process in this exemplary embodiment involves the assembly of pin 12. In this exemplary embodiment, pin 12 is an off-the-shelf RF feedthru pin such as a microwave feedthru pin that is commercially available from numerous sources as noted above. In other exemplary embodiments, pin 12 is custom manufactured and not an off-the-shelf pin. As noted above pin 12 comprises a solid piece of conductive material. In other exemplary embodiments, pin 12 comprises a rigid core coated or plated with a conductive material. The size of pin 12 is determined based on the application that interface 10 will be used for.

Before pin 12 is placed within assembly 14, bead 16 is placed around pin 12. Bead 16 may be placed around pin 12 in one exemplary embodiment or pin 12 may be manufactured with bead 16 already attached to pin 12. As noted above, bead 16 may comprise a low-loss material such as glass or a Teflon® material. A hole is placed through bead 16 which is slightly larger than the radius of pin 12. Bead 16 is then slid onto pin 12 and concentrically surrounds pin 12.

Pin 12 and bead 16 are then placed within assembly 14. Once pin 12 and bead 16 are placed within assembly 14, bead 18 is placed around pin 12. As noted above, bead 18 may comprise a low-loss material such as a glass or a Teflon® material. A hole is placed through bead 18 which is slightly smaller than the radius of pin 12. Bead 18 can still be slid onto pin 12 because, in one exemplary embodiment, bead 18 is made from a pliable material.

Further, in one exemplary embodiment, beads 16, 18 are attached to the assembly 14 to create a hermetic seal at one or both ends of the assembly 14. This hermetic seal helps reduce loss in an exemplary embodiment. The exact spacing around pin 12 and beads 16, 18 can vary. Bead 18 is completely flush within the cavity and seated directly against assembly 14. hi other exemplary embodiments, there is no space around either bead 16, 18 and pin 12 and beads 16, 18 are firmly seated within space 15. The next step in this exemplary manufacturing process is to connect pin 12 to insulator 22. In one exemplary embodiment, pin 12 is merely placed on and not attached to insulator 22 to prevent pin 12 from bending. In other exemplary embodiments, pin 12 is attached to insulator 22 by adhesives. Pin 12 is also connected to circuit 1 1 by wire connector 24. In one exemplary embodiment, wire connector 24 is a wire bond between interface 10 and circuit 11 and is attached by wire bonding techniques. Further, any number of wires or other connector members can be used as wire connector 24 and fall within the scope of the present invention.

Once the manufacturing process of interface 10 is complete, interface 10 is configured to deliver energy waves such as microwaves from circuit 11 to energy transmission device 13. In one exemplary embodiment, circuit 1 1 is a MMIC and energy transmission device 13 is a waveguide. Further, interface 10 is configured to be an impedance matching device and loose little energy and signal even as the frequency of the energy and signal is increased.

Turning now to FIGS. 4 and 5 and in accordance with another exemplary embodiment of the present invention, a coaxial interface for connecting a circuit to an energy transmission device such as a waveguide is disclosed. Throughout, the interface according to this exemplary embodiment shall be referred to as interface 110.

With reference to FIGS. 4-5, and in accordance with this exemplary embodiment of the present invention, coaxial interface 110 is a low-loss interface comprising a coaxial structure that is configured to transmit energy between two devices that it is directly connected or coupled to. It should be noted that the term "low-loss" refers to the ability to reduce signal loss as discussed above. In an exemplary embodiment, coaxial interface 110 connects a circuit 111 to another energy transmission device 113. Furthermore, coaxial interface 110 can be any device with a coaxial structure configured to transmit energy with minimal loss by matching or transforming impedance and modes of energy wave propagation between two or more energy producing or transmission devices.

In one exemplary embodiment, circuit 111 is an integrated circuit such as a monolithic microwave integrated circuit (MMIC). In another exemplary embodiment, circuit 1 11 comprises discrete components on a circuit board, such as memory devices, power sources, light emitting diodes, and the like. Circuit 11 1 can be any type of circuit, integrated circuit, circuit board, printed circuit board, or other type of device or medium that produces or transfers energy waves. As such, the term "circuit" is not limited to devices with discrete components on a circuit board but rather includes any device that produces or transmits energy waves such as wires, cables, or waveguides. Similarly, energy transmission device 1 13 can be any type of device or medium configured to produce or transport energy. In one exemplary embodiment, energy transmission device 113 is a waveguide that guides microwave energy waves. In another exemplary embodiment, energy transmission device 113 comprises wires, cables or other devices configured to transport and guide energy waves from one source to another.

Further, it should be noted that while this application gives examples of energy traveling from circuit 11 1 to energy transmission device 113 through coaxial interface 110, that energy can travel in the other direction from energy transmission device 113 to circuit 111 and still fall within the scope of the present invention. According to these exemplary embodiments, energy can be produced or originate at energy transmission device 113 and travel through coaxial interface 110 to reach circuit 111.

In an exemplary embodiment, coaxial interface 1 10 is any device with two or more layers that share a common axis that is configured to transport energy with minimal loss. Further, an exemplary coaxial interface 110 has an impedance that is in between the impedance of the two devices it is directly connected to. The impedance of coaxial interface 1 10 is determined by the ratio of the outer to inner diameters of the coaxial interface 110 and an insulating material such as a spacer as described below. One exemplary coaxial interface 110 with a fifty ohm impedance has an inner diameter of 0.0255 inches, an outer diameter of 0.66 inches, and a spacer with a dielectric of T-PTFE with a relative dielectric constant of 1.3. Reducing the ratio of outer to inner diameters lowers the impedance and increasing the ratio of outer to inner diameters increases the impedance. Further, providing a spacer with a lower dielectric constant increases the impedance and providing a spacer with a higher dielectric constant decreases the impedance. Changing the length of coaxial interface 10 will also affect its impedance transforming capabilities for a given frequency.

In one exemplary embodiment, coaxial interface 110 comprises a pin 114 surrounded by a spacer 116, a conductor sheath 118, and an insulating jacket 120. According to this exemplary embodiment, coaxial interface 110 is directly connected to circuit 1 1 1 and energy transmission device 113 such as a waveguide. According to one exemplary embodiment, pin 114 is constructed from an electrically conductive low-loss medium such as solid gold, silver, copper, and/or other similar materials with low resistance. Pin 1 14 also generally defines the central axis of coaxial interface 110. Pin 1 14 can be a single piece of metal or it can be a constructed from numerous smaller pieces of metal that are joined together. Certain exemplary pins therefore comprise numerous strands of low- loss conductive material that are braided together to form pin 114.

Pin 114 can also be any shape, for example, pin 114 can be round, square, or rectangular. In one exemplary embodiment, pin 114 is a relatively long, narrow member that is round. Other shapes of pin 1 14 in other exemplary embodiments of the present invention comprise an oval, square, rectangular shaped, irregularly shaped or the like. In one exemplary embodiment, pin 114 is one continuous shape from one end to the other. In other exemplary embodiments, half of pin 114 can be round while the other half is another shape (such as an oval) resulting in pin 114 having two shaped regions. Numerous different shaped regions can be located along pin 114.

With reference to FIG. 4 and in accordance with one exemplary embodiment of the present invention, pin 114 may also extend out of and away from spacer 116, conductor sheath 118, and insulating jacket 120 to contact circuit 111 on one end and energy transmission device 113 on the opposing end. Pin 114 may also contact circuit 111 at certain connection points such as one or more bond pads 122. Pin 114 may be may soldered or connected to bond pad 122 by any known method in the art such as an adhesive, soldering, or attachment devices such as pins and screws. In one exemplary embodiment, pin 1 14 is wire bonded to bond pad 122.

With reference to FIG. 5 and in accordance with an exemplary embodiment of the present invention, coaxial interface 110 may further comprise one or more ground wires 124 that connect coaxial interface 1 10 to circuit 11 1. In this exemplary embodiment, coaxial interface 110 comprises a ground-signal- ground interface with both ground wires 124 flanking pin 114. In one exemplary embodiment, pin 114 and ground wires 124 are connected to circuit 11 1 such as a MMIC at bond pads 122. Spacer 116 is any device or material that is configured to act as an insulator. In one exemplary embodiment, spacer 116 is a dielectric material such as PTFE such as a Teflon® PTFE produced by the E. I. Du Pont De Nemours and Company of Wilmington, Delaware. Further, spacer 116 can be constructed of a solid material or a perforated material with air spaces In yet other exemplary embodiments, spacer 116 is nothing more than a space that can comprise air or a vacuum In an exemplary embodiment where spacer 116 comprises air or a vacuum, spacer 116 functions as an ideal dielectric with no loss

In one exemplary embodiment, conductor sheath 1 18 is a cylindrical member that concenti ically sunounds the spacei 116 Conductor sheath 118 can be any type of material configured to conduct electricity with low loss Certain exemplary materials include solid gold, silvei, copper, and/or other similar materials with low resistance Further, conductor sheath 1 18 can be rigid or flexible depending on whether a rigid or flexible coaxial interface 110 is desired For example, if a rigid coaxial cable is used, conductor sheath 118 is rigid Alternatively, if a flexible coaxial cable is used, conductor sheath 118 is flexible Insulating jacket 120 coveis and sunounds conductor sheath 118

In one exemplary embodiment, coaxial interface 1 10 is a rigid or flexible coaxial cable such as the types that are readily available from numerous commercial sources such as Haverhill Cable and Manufacturing Corporation of Haverhill, Massachusetts In other cxcmplaiy embodiments, coaxial interface 110 is a coaxial pin available from various commercial sources such as Thunderlme Z (a division of Emerson, Inc ) of Hampstead, New Hampshire, Special Hermetic Products, Inc of Wilton, New Hampshire, and Mill-Max Manufacturing Corporation of Oyster Bay, New York

The choice between using a rigid coaxial interface 1 10 and a flexible coaxial interface 110 depends on the application For example, if coaxial interface 110 is used m a small area that is subject to vibrations or other movement, it might be desirable to utilize a flexible coaxial interface 1 10 such as a coaxial cable However, if coaxial interface 110 is used m an area where physical strength and durability of coaxial interface 110 are important, using a iigid coaxial interface 110 would be more appropriate In yet other exemplary embodiments, coaxial interface 110 can be any device with a coaxial structure that is constructed of two or more parts that are joined together to create a coaxial structure In this exemplary embodiment, the parts of the coaxial interface 110 are coaxial structures themselves and when they are connected or otherwise joined together, these individual coaxial parts create a coaxial interface created from at least two or more coaxial parts Certain exemplary coaxial structures are disclosed in co-pending and commonly owned U S Patent Application Serial No 11/743,496 entitled "Interface for Waveguide Pm Launch " Any number of parts, assemblies, or other devices can be used to create coaxial interface 1 10 and fall withm the scope of the present invention In an exemplary embodiment, coaxial interface 110 transmits energy such as microwaves from circuit 111 to energy tiansmission device 113 with minimal loss by piovidmg a pathway with an impedance that is in between the impedance of circuit 111 and energy tiansmission device 113 for energy to travel through as it encounters these changes in impedance and modes of energy wave propagation between circuit 1 1 1 and energy tiansmission device 113 For example, the impedance of the energy source at circuit 111 may be fifty ohms while the impedance of the energy transmission device 113 is two hundred and seventy ohms Normally, these changes of impedance between interface circuit 1 1 1 and eneigy transmission device 1 13 would generate unacceptable signal loss Coaxial interface 110 reduces this loss because its impedance is between the impedance of circuit 111 and energy transmission device 113 Essentially, this "steps down" or "steps up" (depending on the direction of travel) the impedance from circuit 1 1 1 to energy transmission device 1 13 and reduces loss by providing a middle ground impedance thus enabling coaxial interface 1 10 to have impedance transforming capabilities In an exemplary embodiment, increasing or decreasing the electrical length of coaxial interface 110 affects its impedance transforming capabilities at a given frequency

Besides impedance, circuit 111 and energy transmission device 1 13 also have diffeient modes of energy wave propagation For example, a mode of energy wave piopagation foi energy transmission device 113 such as a waveguide may be TEi₀ (Tiansverse Electric, 10) while circuit 111 such as a MMIC may have a microstπp mode of wave propagation of quasi-TEM (Traverse Electromagnetic)

As discussed above, the present invention provides a direct connection between circuit 1 11 and transmission device 113 In an exemplary embodiment, a coaxial structure such as a coaxial cable is used and directly connected to a MMIC on one end and a waveguide on the other opposing end

While the principles of the invention have now been made clear in illustrative embodiments, there will be immediately obvious to those skilled in the art many modifications of structuie, arrangements, proportions, the elements, materials and components, used m the practice of the invention which are particularly adapted for a specific environment and operating lequirements without departing from those principles These and othei changes or modifications are intended to be included within the scope of the present invention, as expressed in the following claims

Claims

What is claimed is

1 An interface comprising a pin configured to transport energy from a circuit to a waveguide, and an assembly surrounding the pin configured to reduce energy loss as compared to a pin without the assembly sunounding the pin

2 The interface of claim 1, furthei comprising a space defined between the pm and the assembly

3 The interface of claim 2, further comprising two beads that are connected to the assembly that further define the space

4 The interface of claim 1, further comprising an insulator attached to the pm

5 The interface of claim 1 , wherein the interface comprises two opposing ends, wherein one end is attached to a circuit and the other end is attached to a waveguide, and a hermetic seal between the circuit and the waveguide 6 An interface comprising a pm comprising first and second ends, wherein the first end is connected to a waveguide assembly and the other end is connected to a circuit, wherein the pm is configured to transport energy from the circuit to the waveguide, an assembly with two opposing ends surrounding the pin and connected to the waveguide wherein the assembly is configured to reduce energy loss, two beads contacting the pm and the assembly wherein one bead contacts one end of the assembly adjacent to the waveguide and the other bead contacts the opposing end of the assembly, and a space defined by the pin, the assembly, and the two beads 7 The interface of claim 6, wherein the circuit is a monolithic microwave integrated circuit

8 The interface of claim 6, wherein the bead contacting the opposing end of the assembly from the waveguide forms a hermetic seal between the assembly and the pm

9 The interface of claim 6, wherein the interface has a coaxial structure 10 The interface of claim 6, further comprising an insulator attached to the pm adjacent to the circuit

1 1 The interface of claim 10, wherein the insulator is tape 12 The interface of claim 6, wherein the pin is a commercially available feedthru pm

13 The interface of claim 6, wherein the interface further comprises a hermetic seal between the circuit and the waveguide assembly 14 An interface comprising a feedthru pm with one end connected to a waveguide assembly and another end connected to a monolithic microwave integrated circuit wherein the feedthru pm is configured to transport energy from the monolithic microwave integrated circuit to the waveguide, an assembly surrounding the pin and connected to the waveguide wherein the assembly is configured to reduce eneigy loss, two beads connected to the feedthru pin and the assembly wherein one bead contacts one end of the assembly and the other bead is a glass bead contacting an opposing end of the assembly that foπns a hermetic seal between the feedthru pin and assembly, a space concentrically surrounding the feedthru pm defined by the feedthru pm, the assembly, and the two beads configured to reduce energy loss, and a thm insulator attached to the pm adjacent to the monolithic microwave integrated circuit

15 The interface of claim 14, further comprising a wire bond connecting the feedthru pm to the monolithic microwave integrated circuit

16 The interface of claim 14, wherein the interface is a coaxial structure

17 The interface of claim 14, wherein the space has a radius of 0 086 inches and the interface is configured for a fifty ohm feedthru pm

18 The interface of claim 14, wherein the assembly comprises metal coated with a low-loss metal coating

19 The interface of claim 14, wherein the assembly comprises plastic coated with a low-loss material

20 The interface of claim 14, wherein the feedthru pm is compπsed substantially of gold 21 The interface of claim 14, wherein the interface further comprises a hermetic seal between the monolithic microwave integrated circuit and the waveguide assembly 22 A pathway for a microwaves comprising a monolithic microwave integrated circuit, an interface connected to the monolithic integrated circuit comprising a feedthru pin and an assembly surrounding the feedthru pin and defining a space between the feedthru pm and the assembly, and a waveguide attached to the interface 23 The pathway of claim 22, wherein the interface further comprises two beads that contact the assembly and further define the space

24 The pathway of claim 22, wherein at least one bead forms a hermetic seal

25 The pathway of claim 22, wherein the interface has a coaxial structure

26 The pathway of claim 22, wherein the interface further comprises a hermetic seal between the monolithic microwave integrated circuit and the waveguide assembly

27 A low loss impedance interface configured to facilitate microwave signal transmission from a MMIC to a waveguide, wherein the interface comprises a pm having a first end configured to connect the waveguide to the pin, the pm further compiising a second end configured to connect to the MMIC via a wirebond, a fust bead configured to be around said pm, a second bead configured to be aiound the pm wherein the first bead is closer to the first end than the second bead, and an assembly comprising a low-loss material configured to surround the pm, the first bead, the second bead, and a hermetically sealed space between the MMIC and the waveguide

28 An electrical system comprising an integrated ciicuit configured to produce energy waves, wherein the integrated ciicuit has a fust impedance and a first mode energy wave propagation, an energy transmission device configure to transmit energy, wherein the energy tiansmission device has a second impedance and a second mode of energy wave piopagation, and a coaxial interface directly connected to the integrated circuit and the energy tiansmission device wherein the coaxial interface is configured to transmit energy between the integrated circuit and the energy transmission device with minimal loss 29 The electrical system according to claim 28, wherein the integrated circuit is a monolithic microwave integrated circuit

30 The electrical system according to claim 28, wherein the energy transmission device is a waveguide

31. The electrical system according to claim 29, wherein the energy transmission device is a waveguide.

32. The electrical system according to claim 28, wherein the coaxial interface is a coaxial cable. 33. The electrical system according to claim 28, wherein the coaxial interface is a pin.

34. An electrical system comprising: a monolithic microwave integrated circuit, wherein the monolithic microwave integrated circuit has a first impedance and first mode of energy wave propagation; a waveguide configured to transmit energy, wherein the waveguide has a second impedance and a second mode of energy wave propagation; and a coaxial interface directly connected to the monolithic microwave integrated circuit and the waveguide wherein the coaxial interface is configured to transmit the energy waves between the monolithic microwave integrated circuit and the waveguide with minimal loss. 35. The electrical system according to claim 34, wherein the coaxial interface is a cable.

36. The electrical system according to claim 34, wherein the coaxial interface is a pin.

37. The electrical system according to claim 34, wherein the coaxial interface is a structure that comprises at least two coaxial parts.

38. The electrical system according to claim 34, wherein the impedance of the monolithic microwave integrated circuit is about fifty ohms and the impedance of the waveguide is about two hundred and seventy ohms.

39. The electrical system according to claim 34, wherein the mode of energy wave propagation at the monolithic microwave integrated circuit is quasi-TEM and the mode of energy wave propagation at the waveguide is TEi₀.

40. The electrical system according to claim 38, wherein the mode of energy wave propagation at the monolithic microwave integrated circuit is quasi-TEM and the mode of energy wave propagation at the waveguide is TEi₀. 41. An electrical system comprising: a monolithic microwave integrated circuit configured to produce energy waves with an impedance of about fifty ohms and a mode energy wave propagation of quasi-TEM; a waveguide configured to transmit energy with an impedance of about two hundred and seventy ohms and a second mode of energy wave propagation of TEio; and a coaxial interface directly connected to the monolithic microwave integrated circuit and the waveguide wherein the coaxial interface is configured to transmit the energy waves between the monolithic microwave integrated circuit and the waveguide with minimal loss.

42. The electrical system according to claim 41 , wherein the coaxial interface is a coaxial cable.

43. The electrical system according to claim 41, wherein the coaxial interface is a coaxial pin. 44. The electrical system according to claim 41, wherein the coaxial interface comprises a structure that comprises at least two coaxial parts.

45. The electrical system according to claim 41, wherein the coaxial interface is a flexible coaxial cable.

46. The electrical system according to claim 41, wherein the coaxial interface is a rigid member.

47. A method of transmitting energy with minimal loss comprising: providing an integrated circuit that produces energy waves wherein the integrated circuit has a first impedance and a first mode of energy wave propagation; providing an energy transmission device configured to transmit energy waves wherein the energy transmission device has a second impedance and a second mode of energy wave propagation; directly connecting a coaxial interface to the integrated circuit on one end of the coaxial interface and to the energy transmission device on an opposing end of the coaxial interface; and transmitting energy from the integrated circuit to the energy transmission device through the coaxial interface with minimal loss.

48. The method according to claim 47, wherein the coaxial interface is a coaxial cable.

49. The method according to claim 47, wherein the integrated circuit is a monolithic microwave integrated circuit.

50. The method according to claim 49, wherein the impedance of the monolithic microwave integrated circuit is about fifty ohms and the impedance of the energy transmission device is about two hundred and seventy ohms.

51. The method according to claim 50, wherein the mode of energy wave propagation at the monolithic microwave integrated circuit is quasi-TEM and the mode of energy wave propagation at the energy transmission device is TEio.

52. The method according to claim 51, wherein the energy transmission device is a waveguide.