RF power combiner / divider

Abstract

To provide a simplified and more compact RF power combiner / divider.SOLUTION: An RF power combiner / divider is for combining a plurality of RF inputs (1a, 1b) into a combined RF output (2), and comprises an isolating circuit (10) coupling the RF inputs to a common floating point 6. The isolating circuit (10) includes a grounded resonant cavity inside which transmission lines (20a, 20b) are arranged. Each of the transmission lines has a first end connected to one of the RF inputs (1a, 1b), and an opposite second end connected to grounded resistors (4a, 4b) arranged outside the resonant cavity. Each of the transmission lines (20a, 20b) is coupled to a coupling portion (22) of the resonant cavity, where one end of the coupling portion (22) is connected to ground, and where an opposite end of the coupling portion (22) forms the common floating point (6). Such an arrangement is more compact than existing arrangements, but allows easier cooling of the resistors (4a, 4b).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to the field of radio frequency (hereinafter "RF") power couplers and / or distributors.

Background Art

[0002] An RF power coupler is a device that combines RF signals from multiple input ports into a combined RF output signal. Conversely, an RF power distributor (often called a splitter) divides an RF input signal into multiple RF output signals. Most of these devices are reversible in the sense that a coupler can be used as a distributor, or vice versa. Such devices are well known in the art.

[0003] An exemplary power coupler / distributor is known from US3091743 (often called a Wilkinson coupler / distributor). When used as a distributor, the Wilkinson coupler uses a quarter-wave transformer to split an input signal into multiple output signals that are in phase with each other. Resistors are connected to the output ports in a star configuration to match the outputs and to perform isolation.

[0004] Wilkinson-type power distributors / couplers have proven to be very useful for equal or unequal power distribution in phase and for applications having moderate power levels or frequency ranges, where the series resistors can be made large enough to dissipate a reasonable power level. Since it is electrically and mechanically symmetric, its performance over a moderate bandwidth is superior to that of other types of distributors / couplers, such as rat-race and branch distributors / couplers. However, at higher frequencies or higher power levels, it is very difficult to construct a very accurate in-phase high-power distributor / coupler based on the Wilkinson principle due to the physical limitations of the resistors required in the Wilkinson circuit. These resistors must be physically small, and due to additional shunt capacitance that has the effect of degrading performance, it is difficult to dissipate heat from the resistors.

[0005] Another well-known RF power coupler is the Gysel coupler (UHGysel, "A new N-way power divider / combiner suitable for high-power applications," IEEE MTT-S Int.Microw.Sym., pp. 116-118, May 1975). The Gysel coupler is an extension of Wilkinson's N-way coupler. The main advantages of the Gysel design are the presence of an external isolated load, which allows for high-power loads, an easily understandable geometry, and the ability to monitor imbalances at the output ports.

[0006] In the original Wilkinson coupler, resistive star-shaped resistors are directly connected between the N output ports, resulting in a physically complex arrangement. The Gysel coupler replaces the resistive star-shaped resistors with a combination of transmission lines and shunt-connected load resistors. The transmission lines connect each output port to what are called the associated load ports. All load ports are connected by transmission lines of characteristic impedance Z with a common stray star point. The main advantages of the Gysel design are its high-power handling capability due to the availability of external high-power isolated loads, and its ability to monitor and adjust imbalances in the coupled RF sources.

[0007] In a Gysel power distribution / coupling circuit, the line lengths of the impedance conversion line, the first connection line, and the second connection line are odd multiples of a quarter wavelength at the operating frequency (n.λ / 2 + λ / 4). The frequency used is the frequency of the desired high-frequency signal to be divided or the frequency of the desired high-frequency signal to be coupled. However, the Gysel distribution / coupling circuit suffers significant power loss even when the frequency of the high-frequency signal deviates from the operating frequency and is affected by variations in the amplitude or phase of the high-frequency signal inputs from multiple input / output terminals. The heat generated when power is consumed by the terminating resistor propagates from the terminating resistor to ground and is dissipated from ground. Additionally, heat is generated due to conduction losses in the path for transmitting high-frequency signals input from multiple input / output terminals, and this generated heat is transmitted to ground via the terminating resistor. Therefore, heat concentrates on the terminating resistor, causing a temperature rise in the terminating resistor, which affects the circuit's durability.

[0008] Another RF power coupler / distributor is known from WO201915932. This power distributor / coupler addresses some of the above problems by including multiple impedance matching lines. One end of each impedance matching line is connected to a common terminal, and the other end is connected to each of the multiple input / output terminals, as well as to multiple pairs of coupled transmission lines. Each pair of coupled transmission lines includes a first transmission line, one end of which is connected to the other end of an impedance matching line and the other end is grounded, and a second transmission line, one end of which is connected to a connection point and the other end is connected to a terminating resistor that is grounded. In each pair of coupled transmission lines, the first transmission line is electrically coupled to the second transmission line.

[0009] Such designs can be operated at high power using water-cooled termination resistors. However, the volume of this design remains large, especially for a large number of inputs and / or low RF frequencies.

[0010] Therefore, there is a need to simplify the design and have smaller couplers / distributors. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] U.S. Patent No. 3091743 [Patent Document 2] International Publication No. 201915932 [Non-patent literature]

[0012] [Non-Patent Document 1] UHGysel, "A new N-way power divider / combiner suitable for high-power applications," IEEE MTT-S Int.Microw.Sym., pp. 116-118, May 1975. [Overview of the Initiative] [Problems that the invention aims to solve]

[0013] The problem that this invention proposes to solve is to provide a simplified and smaller RF power coupler / distributor. [Means for solving the problem]

[0014] The present invention is defined by the independent claims. Dependent claims define advantageous embodiments.

[0015] According to the present invention, an RF power coupler is provided for coupling N input signals into a single output signal, the RF power coupler comprising N input ports, each connected to a common output port through N impedance matching elements, and a separation circuit that connects the N input ports to a common floating point.

[0016] The isolation circuit includes a grounded resonant cavity, inside which N transmission lines are arranged, each of the N transmission lines having a first end connected to one of the N input ports and an opposite second end connected to a grounded resistor arranged outside the resonant cavity, each of the N transmission lines being connected to a connection part of the resonant cavity, one end of the connection part being connected to the ground, and the opposite end of the connection part forming a common floating point.

[0017] Thanks to this specific design of the isolation circuit, the RF power coupler according to the invention is smaller, still enables effective cooling (e.g., water cooling) of the individual resistors, and moreover provides a wider bandwidth, for example compared to a Gysel coupler. It is also less expensive because it requires fewer components compared to the coupler of WO201915932.

[0018] In some examples, the resonant cavity has a cylindrical shape, the connection part has a cylindrical shape and is coaxial with the resonant cavity, and the N transmission lines are arranged at a connection distance from the connection part around the connection part.

[0019] In some other examples, the resonant cavity has a parallelepiped shape, the connection part has a parallelepiped shape and is coaxial with the resonant cavity, and the N transmission lines are arranged at a connection distance from the connection part around the connection part.

[0020] Such an arrangement indeed results in a small power coupler that is easy to manufacture.

[0021] In some examples, one or more ferrite rings are arranged around the N transmission lines inside the resonant cavity. Such an arrangement indeed results in an even smaller power coupler, especially at lower operating frequencies.

[0022] The rated operating frequency range of the RF power coupler according to the invention is included, for example, in the range of 1 MHz to 10 GHz.

[0023] The rated output power of the RF power coupler according to the present invention is included, for example, in the range of 1 KW to 1 MW.

[0024] These and further aspects of the present invention will be described in more detail, by way of example, with reference to the accompanying drawings.

Brief Description of the Drawings

[0025] [Figure 1] FIG. is a diagram showing an equivalent electrical circuit of an exemplary two-way RF power coupler according to the present invention. [Figure 2] FIG. schematically shows an exemplary electromechanical implementation of a separation circuit of a four-way RF power coupler according to the present invention. [Figure 3] FIG. is a cross-sectional view taken along line "A-A" of the separation circuit of FIG. 2. [Figure 4] FIG. schematically shows another exemplary electromechanical implementation of a separation circuit of a four-way RF power coupler according to the present invention. [Figure 5] FIG. schematically shows yet another exemplary electromechanical implementation of a separation circuit of an eight-way RF power coupler according to the present invention. [Figure 6] FIG. is a cutaway 3D view showing an exemplary four-way RF power coupler according to the present invention. [Figure 7] FIG. schematically shows an exemplary electromechanical implementation of a separation circuit of a four-way RF power coupler according to the present invention.

Modes for Carrying Out the Invention

[0026] The figures in the drawings are not to scale and are not in proportion. Generally, like or identical components are denoted by the same reference numerals in the figures.

[0027] For clarity, exemplary embodiments of two-way, four-way, and eight-way RF power couplers / distributors according to the present invention are disclosed. Nevertheless, the present invention relates more generally to N-way RF power couplers / distributors, where N is greater than or equal to 2. For example, N can have a realistic value included between 2 and 50.

[0028] For the sake of clarity, the examples disclosed below will be described from the perspective of their coupling function, but each can also operate as a distributor (often called a splitter), as in the case of conventional RF power couplers / distributors that use only passive components.

[0029] Figure 1 shows the equivalent electrical circuit of an exemplary two-way RF power coupler according to the present invention.

[0030] A two-way RF power coupler comprises two input ports (1a, 1b), each of which is connected to a common output port (2) through two impedance matching elements (3a, 3b), in this example the two impedance matching elements (3a, 3b) are shown as a transmission line, but may instead be lumped elements such as an inductor and / or a capacitor and / or a transformer. This part of the RF power coupler is well known in the art and will not be described further.

[0031] Here, we focus on the lower part of the coupler, more specifically the separation circuit (10), as shown inside the dotted line in Figure 1.

[0032] The separation circuit (10) in this example includes two transmission lines (20a, 20b), both of which are electrically connected to a common transmission line (22). The common transmission line (22) is grounded at one end and left floating at the opposite end, forming a common floating point (6) (often called a “star point”). As is commonly known in the art, transmission lines are said to be connected (or electrically connected) when they are close enough that energy flows from one line to the other.

[0033] The first transmission line (20a) has one end connected to the first input port (1a) and another end connected to a resistor (4a) that is individually grounded. The second transmission line (20b) has one end connected to the second input port (1b) and another end connected to a resistor (4b) that is individually grounded. Each of the two transmission lines (20a, 20b) has an electrical length preferably λ / 4 at the rated operating frequency of the RF power coupler.

[0034] Figure 2 schematically shows an exemplary electromechanical implementation of the isolation circuit (10) of the four-way RF power coupler according to the present invention.

[0035] The isolation circuit comprises a grounded resonant cavity (15) in which four transmission lines (20a, 20b, 20c, 20d) are arranged. Each of the four transmission lines has a first end (upper end in Figure 2) connected to one of the four input ports (1a, 1b, 1c, 1d) of the coupler, and a second end on the opposite side (lower end in Figure 2) connected to grounded resistors (4a, 4b, 4c, 4d) located outside the resonant cavity (15).

[0036] There are four electrical connections between the first end of each of the four transmission lines and each of the four input ports (1a, 1b, 1c, 1d).

[0037] The resonant cavity (15) may have four through-holes through which the four electrical connections each pass.

[0038] Additionally, there are four other electrical connections between the second end of each of the four transmission lines (20a, 20b, 20c, 20d) and each of the four grounded resistors (4a, 4b, 4c, 4d).

[0039] The resonant cavity (15) may have four other holes passing through its base (9), through which the four other electrical connections pass to the four grounded resistors (4a, 4b, 4c, 4d), respectively. This makes it possible to place the four grounded resistors (4a, 4b, 4c, 4d) outside the resonant cavity (15), as a result allowing the resistors to be easily cooled and / or accessed. Alternatively, the four grounded resistors (4a, 4b, 4c, 4d) could be placed inside the resonant cavity (15).

[0040] Each of the four transmission lines (20a, 20b, 20c, 20d) is electrically connected to the coupling section (22) of the resonant cavity. One end of the coupling section (22) (the lower end in Figure 2) is connected to ground, for example, by being electrically connected to the base (9) of the resonant cavity. The opposite end of the coupling section (22) (the upper end in Figure 2) forms the common floating point (6) discussed above with respect to Figure 1. In this example, the resonant cavity (15) has a cylindrical shape, and the coupling section (22) has a cylindrical shape coaxial with the resonant cavity. As seen in Figure 2, the four transmission lines (20a, 20b, 20c, 20d) are arranged around the coupling section (22) at coupling distances from the coupling section (22). In some examples, the four transmission lines have a trough shape.

[0041] Each of the four transmission lines (20a, 20b, 20c, 20d) preferably has an electrical length of λ / 4 at the rated operating frequency of the RF power coupler.

[0042] Figure 3 shows a cross-sectional view of "AA" in the separation circuit of Figure 2.

[0043] Figure 4 schematically shows another exemplary electromechanical implementation of the isolation circuit for a four-way RF power coupler according to the present invention.

[0044] It is essentially the same as the separation circuit in Figure 2, except that the resonant cavity (15), the four transmission lines (20a, 20b, 20c, 20d), and the connecting section (22) all have a parallelepiped shape instead of a (semi)cylindrical shape. A cross-sectional view of "AA" of the separation circuit in Figure 4 can also be seen in Figure 3.

[0045] Figure 5 schematically shows another exemplary electromechanical implementation of the isolation circuit (10) of the 8-way RF power coupler according to the present invention.

[0046] The isolation circuit comprises a grounded resonant cavity (15) in which eight transmission lines (20a, 20b, 20c, 20d, ...) are arranged. Each of the eight transmission lines has a first end connected to one of each of the eight input ports (1a, 1b, 1c, 1d, ...) of the coupler, and a second end on the opposite side connected to grounded resistors (4a, 4b, 4c, 4d) located outside the resonant cavity (15).

[0047] There are eight electrical connections between the first end of each of the eight transmission lines and each of the eight input ports (1a, 1b, 1c, 1d, ...).

[0048] The resonant cavity (15) may have eight through-holes through which the eight electrical connections each pass.

[0049] Additionally, there are eight other electrical connections between each of the eight transmission lines (20a, 20b, 20c, 20d, ...) and each of the eight grounded resistors (4a, 4b, 4c, 4d, ...).

[0050] The resonant cavity (15) may have eight other holes passing through its base (9), through which the eight other electrical connections pass to eight grounded resistors (4a, 4b, 4c, 4d, ...). This makes it possible to place the eight grounded resistors (4a, 4b, 4c, 4d, ...) outside the resonant cavity (15), as a result allowing the resistors to be easily cooled and / or accessed. Alternatively, the eight grounded resistors (4a, 4b, 4c, 4d, ...) may be placed inside the resonant cavity (15).

[0051] Each of the eight transmission lines (20a, 20b, 20c, 20d, ...) is electrically connected to the coupling portion (22) of the resonant cavity (15). A common floating point (6) is formed, in this example, by the center of the resonant cavity.

[0052] To be understood, the embodiment in Figure 5 is similar to the embodiment in Figure 2, except that the transmission lines (20a, 20b, 20c, 20d, ...) are arranged radially instead of axially, and that it has eight input ports and therefore eight grounded resistors instead of four. In Figure 5, only four grounded resistors are shown for clarity, but the other four are arranged symmetrically.

[0053] Each of the eight transmission lines (20a, 20b, 20c, 20d, ...) has an electrical length of preferably λ / 4 at the rated operating frequency of the RF power coupler.

[0054] Figure 6 shows a cutaway 3D view of an exemplary four-way RF power coupler according to the present invention.

[0055] The lower half of it (the part below the dotted line) is equipped with a separation circuit (10), and this lower half is the same as, for example, the one shown in Figure 2.

[0056] The upper half of it (the part above the dotted line) essentially corresponds to the coupler function and in this example has four input ports (1a, 1b, 1c, 1d) connected to a common output port (2) through four impedance matching elements, each of which is a transmission line (3a, 3b, 3c, 3d). In this example, all the transmission lines (3a, 3b, 3c, 3d, 20a, 20b, 20c, 20d) and the connector (22) have longitudinal axes parallel to each other and are packed into a grounded resonant cavity (15).

[0057] As shown in Figure 6, the four input ports (1a, 1b, 1c, 1d) pass through the middle of the resonant cavity (15) and are arranged radially around the middle, while the output port (2) passes through the top of the resonant cavity (15) and is located at the top. In this example, the four grounded resistors (4a, 4b, 4c, 4d) are located outside the resonant cavity (15), but they could instead be located inside the resonant cavity (15).

[0058] The lower sides of the four impedance matching elements (3a, 3b, 3c, 3d) (in this example, the four transmission lines) are electrically connected to the upper sides of the four transmission lines (20a, 20b, 20c, 20d) of the isolation circuit (10), respectively.

[0059] Figures 2-6 provide only a few examples of realistic geometric arrangements, but it will be clear that other geometric arrangements can be used in a similar manner, for example, by using prism shapes instead of cylindrical or parallelepiped shapes.

[0060] Figure 7 schematically shows another exemplary electromechanical implementation of the isolation circuit for a four-way RF power coupler according to the present invention.

[0061] In this example, multiple ferrite rings (30) (three rings in this example) are arranged inside the resonant cavity (15) around the four transmission lines (20a, 20b, 20c, 20d) of the isolation circuit (10). In some examples, multiple ferrite rings are arranged inside the resonant cavity around N transmission lines, distributed over at least a portion of the length of the N transmission lines of the isolation circuit (10). Obviously, if the cavity connections have a parallelepiped shape, such as shown in Figure 4, the ferrite rings may be rectangular or square with rounded corners, rather than circular or oval.

[0062] The RF power coupler according to the present invention has, for example, a rated operating frequency in the range of 1 MHz to 10 GHz and a rated output power in the range of 1 KW to 1 MW.

[0063] In the example in Figure 6, at an operating frequency of 75 MHz, the isolation circuit (10) typically has a length of 1 m without the four grounded resistors (4a, 4b, 4c, 4d), and the entire coupler typically has a length of 2 m without the four grounded resistors (4a, 4b, 4c, 4d). These physical lengths can, of course, decrease as the operating frequency increases.

[0064] Furthermore, in the example shown in Figure 6, the resonant cavity (15) has a typical outer diameter of 15 cm for an output power of 100 kW to 200 kW at an operating frequency of 75 MHz.

[0065] In any embodiment, each of the grounded resistors (4a, 4b, 4c, 4d) has a value of, for example, 50Ω, or each has a value of, for example, 75Ω. The power rating of each grounded resistor (4a, 4b, 4c, 4d) is, for example, greater than or equal to the input power of each input port. The isolation between input ports is, for example, -30dB.

[0066] The present invention is described in terms of specific embodiments, which are illustrative and should not be considered limiting. More generally, it will be understood by those skilled in the art that the present invention is not limited by what is specifically shown and / or described above.

[0067] The reference figures in the claims do not limit the scope of their protection.

[0068] The use of verbs such as "to comprise," "to include," and "to be composed of," or any other variations thereof, as well as their respective conjugations, does not exclude the existence of elements other than those referred to by them.

[0069] The use of articles such as "a," "an," or "the" preceding an element does not exclude the existence of multiple such elements.

[0070] The present invention can also be described as follows: An RF power coupler / distributor comprising a separation circuit (10) for combining a plurality of RF inputs (1a, 1b, 1c, 1d) into a coupled RF output (2), and / or for connecting the RF inputs to a common floating point (6). The separation circuit (10) includes a grounded resonant cavity (15) inside which transmission lines (20a, 20b, 20c, 20d) are arranged, each of which has a first end connected to one of the RF inputs (1a, 1b, 1c, 1d) and a second end on the opposite side connected to grounded resistors (4a, 4b, 4c, 4d) located outside the resonant cavity. Each of the transmission lines (20a, 20b, 20c, 20d) is connected to a resonant cavity coupling (22), one end of the coupling (22) is connected to ground, and the other end of the coupling (22) forms a common floating point (6). Such an arrangement is smaller than existing arrangements, yet still allows for easier cooling of the resistors (4a, 4b, 4c, 4d).

[0071] As those skilled in the art of RF coupling will understand, the coupling according to the present invention can also be used as an RF splitter or distributor by using the RF output of the previously described examples as an RF input and the RF input as an RF output. Therefore, the present invention also relates to RF splitters as described herein. [Explanation of Symbols]

[0072] 1a Input port, RF input 1b Input port, RF input 1c input port, RF input 1d Input port, RF input 2 output ports, RF output 3a Impedance matching elements, transmission lines 3b Impedance matching elements, transmission lines 3c transmission line, impedance matching element 3D transmission line, impedance matching element 4a resistor 4b resistor 4c resistor 4d resistor 6. Floating point 9 base 10 Separation circuit 15 Resonant cavity 20a transmission line 20b transmission line 20c transmission line 20d transmission line 22 Transmission lines, connecting sections 30 Ferrite Rings

Claims

1. An RF power coupler for coupling N input signals into a single output signal, comprising N input ports (1a, 1b, 1c, 1d) each connected to a common output port (2) through N impedance matching elements (3a, 3b, 3c, 3d), and a separation circuit (10) connecting the N input ports to a common floating point (6), The separation circuit (10) comprises a grounded resonant cavity (15) in which N transmission lines (20a, 20b, 20c, 20d) are arranged inside. Each of the N transmission lines has a first end connected to one of the N input ports (1a, 1b, 1c, 1d), and a second end on the opposite side connected to a grounded resistor (4a, 4b, 4c, 4d) located outside or inside the resonant cavity (15). An RF power coupler characterized in that each of the N transmission lines (20a, 20b, 20c, 20d) is connected to a connecting portion (22) of the resonant cavity, one end of the connecting portion (22) is connected to ground, and the opposite end of the connecting portion (22) forms the common floating point (6).

2. The RF power coupler according to claim 1, wherein the resonant cavity (15) has a cylindrical shape, the connecting portion (22) has a cylindrical shape and is coaxial with the resonant cavity, and the N transmission lines (20a, 20b, 20c, 20d) are arranged around the connecting portion (22) at a connecting distance from the connecting portion (22).

3. The RF power coupler according to claim 1, wherein the resonant cavity (15) has a parallelepiped shape, the connecting portion (22) has a parallelepiped shape and is coaxial with the resonant cavity, and the N transmission lines (20a, 20b, 20c, 20d) are arranged around the connecting portion (22) at a connecting distance from the connecting portion (22).

4. The RF power coupler according to claim 1, wherein one or more ferrite rings (30) are arranged inside the resonant cavity (15) around the N transmission lines (20a, 20b, 20c, 20d).

5. The RF power coupler according to claim 1, wherein the resonant cavity (15) has a cylindrical shape, and the N transmission lines (20a, 20b, 20c, 20d) are arranged radially inward of the resonant cavity at a connection distance from the connecting portion (22a, 22b, 22c, 22d).

6. The RF power coupler according to claim 1, wherein the N impedance matching elements (3a, 3b, 3c, 3d) each comprise N elongated conductors arranged parallel to each other, one end of each of the N elongated conductors is connected to the first end of each of the N transmission lines (20a, 20b, 20c, 20d), and the opposite ends of the N elongated conductors are connected to each other and to the common output port (2).

7. The RF power coupler according to claim 1, wherein the base (9) of the resonant cavity (15) is provided with N through-holes, and electrical connections between each of the second ends of the N transmission lines (20a, 20b, 20c, 20d) and the N grounded resistors (4a, 4b, 4c, 4d) pass through the N through-holes.

8. The RF power coupler according to claim 1, having a rated operating frequency in the range of 1 MHz to 10 GHz.

9. The RF power coupler according to claim 1, having a rated output power in the range of 1 kW to 1 MW.

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