Radial power combiner/divider using dielectrically loaded waveguides

A power combiner/power divider has a disk shaped housing cavity and a housing of electrically conductive material, such as metal. A junction pin is positioned centrally in the power combiner/divider. Additional ports are positioned radially along the periphery of the disk shaped portion. Tapered waveguides may extend from the radially positioned ports to the centrally positioned junction pin. A hollow radial cavity provided in the cavity holds a dielectric insert that may have tapering extensions radiating from a central ring. The ring surrounds the centrally positioned port.

BACKGROUND OF THE INVENTION

Power combiners combine the power from multiple inputs into a single output. Conversely, power dividers divide the power from a single input into multiple outputs. Power combiners and dividers have found use in many applications. For example, power combiners are often used in microwave communications to receive inputs from multiple amplifiers and combine those inputs into a single output. Thus, multiple lower power cheaper amplifiers may be used rather than a single more expensive higher power amplifier.

One limitation with current power combiners/dividers relates to the size of such power combiners/dividers. Conventional power combiners/dividers generally are large devices, which are often both costly and difficult to deploy.

SUMMARY

In accordance with at least one aspect of the present invention, a radial power combiner includes an electrically conductive housing having a disk shaped cavity. Input ports for receiving inputs are positioned radially around the disk shaped cavity and have electrical connections to the housing. A junction rod is centrally positioned in the disk shaped cavity for combining the inputs received by the input party. The junction rod has electrical communication with the output port. The housing provides tapered waveguides extending from the input ports to the output port. A dielectric material is positioned in the disk shaped cavity concentrically around the output port The dielectric material has tapered extensions extending radially outward from a central portion. The dielectric material may be, for example, plastic, such as polytetrafluoroethylene.

In accordance with another aspect of the present invention, a radial power divider includes an electrically conductive housing having a disk shaped cavity. An input port is positioned on the housing for receiving an input. A junction rod is in the electrical communication with the output port and receives the input from the input port. Output ports are positioned radially around the disk shaped cavity for outputting outputs. The output ports have electrical connections to the housing. A dielectric material is positioned concentrically around the junction rod. The dielectric material has tapered extensions extending radially outward from a central portion surrounding the junction rod. The disk shaped cavity includes tapered waveguides extending from the input port to the respective output ports.

DETAILED DESCRIPTION OF THE INVENTION

Exemplary embodiments described herein relate to a power combiner/divider architecture that provides several benefits. The architecture described herein has a smaller size than conventional power dividers/combiners. In addition, the power combiner/divider is designed to provide appropriate impedance matching at the transitions from ports to transmission lines in a power combiner/divider. This results in reduced reflections and a high level of power transfer.

The exemplary embodiments described herein deploy one or more dielectric materials in a radial cavity provided within the power combiner/divider. The one or more dielectric materials help to perform appropriate impedance transformations to yield the appropriate impedance matching. The power combiner/divider also deploys other approaches to further help with such impedance transformations.

FIG. 1shows a radial power combiner/divider100for an exemplary embodiment. For purposes of this discussion, we will initially discuss the device100as a power combiner. Nevertheless, as will be explained below, this architecture may be also deployed in a power divider. The device100includes a housing101. Those skilled in the art will appreciate that the combiner may have numerous shapes such a rectangular shape, an oval shape or another suitable shape. The housing101is made of an electrically conductive material, such as a metal, like stainless steel.

The power combiner100includes input ports102that are uniformly spaced radially along the housing101. These input ports102may be designed to receive coaxial inputs from an energy sources, such as microwave sources. The input ports102may include a configuration that is suitable for acting as a connector with a coaxial connector.

The housing101may include holes104for fasteners, such as screws for securing together components of the housing101. Screws106may also be provided at more radially outward positions to secure together components.

The power combiner100includes a coaxial output port110. As will be described in more detail below, the housing101provides waveguides that extend from the input ports102to a junction pin centrally located in a radial cavity.

FIG. 2shows a top portion200of the power combiner. The top portion200includes a central portion202that is disk-shaped in this illustrative case but can assume other shapes. The central portion202has a star-shaped recess204in which a dielectric insert206may rest. The central portion202may have a raised centrally located probe assembly208into which a junction pin210may be screwed or may be attached by other means, such as epoxy. The central portion202may include holes212through which fasteners, such as screws, may pass to attach the top portion200to a lower portion302(FIG. 3). Holes214are provided for inputs pins310(FIG. 3) to pass to create the input connectors102(shown inFIG. 1). Posts216are provided to align and connect the top portion200with the lower portion302. Fasteners may pass through the interiors of the posts210.

The dielectric insert206is made of a dielectric material, such as a plastic, like polytetrafluoroethylene. As will be explained in more detail below, the dielectric insert206helps to provide impedance transformations for a smooth transformation between the input ports102and the output ports110.

The dielectric insert206shown inFIG. 2is star shaped. The dielectric insert206may include a number of spoke like extensions207that taper in their width as they extend outward from the central portion205. The dielectric extensions207surround the waveguides and help to transform the impedance as will be described in more detail below. The number of extensions207may equal the number of input ports and also equal the number of waveguides extending from the input ports. The dielectric insert206has a circular interior opening that abuts and concentrically surrounds the center portion assembly208(FIG. 2) of the power combiner.

Those skilled in the art will appreciate that the dielectric insert206need not be made of a single dielectric material but may be formed by multiple dielectric materials. Moreover, the dielectric constant of the materials may vary. For example, different extensions202may have different dielectric constants. Moreover, the shape of the dielectric insert206may vary and need not assume a star shape as shown inFIG. 2. Still further, the dielectric constant of the dielectric insert206need not be uniform throughout but rather may vary over the insert. That said, for purposes of discussion of the exemplary embodiment herein, it is assumed that the dielectric insert206is composed of a single material having a single dielectric constant.

FIG. 3shows the top portion300and the lower portion302of the device100in a partially exploded view. The bottom portion302includes holes306in which the posts304of the top portion300rest when the two portions300and302are assembled. The bottom portion302includes an opening308through which the junction pin320passes. The opening308may be tapered to accommodate the base of the center probe assembly. Holes314in the top portion300align with the holes312in the bottom portion302so that the fasteners may secure the top portion300with the lower portion. Pins310for the input probe pass through holes316in the top portion.

The bottom portion322includes a recessed disk shaped portion322that aligns with the disk shaped portion324of the top portion. When the top portion300and the bottom portion302are assembled, a disk shaped radial cavity is created.

The dielectric insert318rests within the radial cavity that is otherwise hollow in the power combiner100. In some embodiments, the dielectric insert318may occupy substantially the entire height of the radial cavity. In other embodiments, the dielectric insert318need not occupy the entire height of the radio cavity.

Each input port102(FIG. 1) has a center conductor pin310that is short circuited to the housing and that is designed to transfer electromagnetic energy to the disk portion of the structure. A hollow waveguide extends from the input port102to carry the energy to the disk portion. The combined energy from the input ports is collected at the center of the disk position (i.e. probe assembly) and exits over a coaxial transmission line for the output port110. Each waveguide extending from the input port is conical. The conical nature of this waveguide has the advantage that it supports a transferred electromagnetic (TEM) mode and therefore has a constant characteristic transmission line impedance against radial distance. In TEM mode, there is no electric or magnetic fields in the directions of propagation. The conical waveguide provides a gradual impedance taper.

As can be seen inFIG. 3, the star shaped dielectric insert318is positioned concentric to the junction pin320such that the number of extensions help to create electrically uniform phase paths between the input ports (see pins310) and the junction pin320.

FIG. 4shows the backside of the power combiner. Bottom part406includes a waveguide407. The centrally positioned junction pin402extends into the waveguide407and is in electrical communication with the waveguide407. At the other end of the waveguide407is an electrical pin404for the output port. (See110inFIG. 1). Microwave energy is communicated from the junction pin402to the waveguide407and is transmitted along the waveguide to pin404. The pin404is part of the output port110(shown inFIG. 1). An additional plate408covers the waveguide407. The additional plate408is secured by fasteners, such as screws110, that pass through holes412into holes414in the bottom portion.

FIG. 5shows a quarter wavelength section500of the transmission path that extends from the disk portion to where the coaxial line for the output port reduces in diameter. This quarter length section500thus extends from the inner radius of the dielectric206(FIG. 2) to the location in the coaxial line for the junction pin210(FIG. 2) where it steps down in diameter. This section560is designed to act as a quarter wavelength transformer to adjust the impedance to better match the output.

FIG. 6provides a cross-sectional view of the power combiner600. As can be seen inFIG. 6, top portion602is secured to bottom portion604by screws606that pass through aligned holes608. Similarly, additional plate hole610is secured via screws612that pass through aligned holes614. The waveguide622receives the combined microwave energy via central probe620and facilitates the passage of the microwave energy to probe624. Pin626passes the microwave energy to the output port which includes coaxial connector628. Input ports607pass the microwave signals to the waveguides in the top portion602so that the energy can be gathered at the central probe620. Dielectric603is positioned in the hollow cavity and helps to position the waveguides.

FIG. 7shows a graph that maps impedance relative to position along the transmission path. As was mentioned previously, the aim of this architecture is to provide impedance matching at the input and impedance matching at the output to reduce reflections and to maximize power transfer. As can be seen inFIG. 7, initially the waveguide has a characteristic impedance. This section of the graph is designated by reference number700. This represents the portion of the waveguide that is not enveloped by the dielectric. Then the presence of the dielectric produces a gradual reduction and impedance due to the taper of the dielectric and the taper of the waveguide. This section of the graph is designated by reference number702. The impedance then stays at a constant level for the portions where the extension have stopped but there is still dielectric present. This is designated by reference704inFIG. 7. At the end of the dielectric, at impedance step occurs along the quarter wavelength section500(SeeFIG. 5). This is designated by reference706inFIG. 7. Lastly, with the taper, due to the step down and the coaxial line, an increase of high impedance is reached that is designed to match the coaxial line output impedance. This is shown in reference number708inFIG. 7.

Thus, asFIG. 7illustrates, the impedance is matched to the input and output and gradually tapered as needed to produce optical performance.

The effect of the dielectric insert on the impedance of the waveguide may be expressed as follows. The impedance of the dielectric loaded part is

ZD=1k⁢Zair
where k is the dielectric constant of the dielectric used in the dielectric insert and Zairis the impedance of the radial waveguide in air.

As was discussed above, a quarter wavelength impedance transformers is utilized. The impedance of the output may be expressed as Zair2=ZDZoutput. As such, we get that Zoutput=√{square root over (k)}Zairby combining the two equations set forth above. This equation illustrates that the dielectric constant of the dielectric insert affects the output impedance and therefore the output match.

The device100ofFIG. 1may instead be a power divider. When the device is configured as a power divider, the radially positioned ports102act as output ports, and the centrally positioned port110acts as an input port. The dielectric insert and the disk shaped cavity may be the same as described above relative to the power combiner. The waveguides and other structures described below may also be the same.

While the present invention has been described with reference to exemplary embodiments herein, those skilled in the art will appreciate that various changes in form and detail may be made without departing from the intended scope of the present invention as defined in the appended claims.