Field of Technology

The invention relates to high-power microwave generators and can be used in designing circuits of power combiners/dividers.

Background Art

Powerful microwave generators are currently constructed by one of two basic schemes: as a single high power amplifier or on the basis of combining power from several individual sources. The present application considers the second scheme of generators.

A variety of schemes of power combiners/dividers are known in the art. Most of conventional power combiners operate on two principles of combining/dividing power. A first principle relies on the use of different transmission lines implemented in coaxial cables, strip lines and baluns for transition between transmission lines of different type. Examples of such power combiners based on the Wilkinson scheme are disclosed in U.S. Patents 5,767,755 and 5,334,957 and provide for the use of a plurality of transmission lines with a plurality of input terminals and an output terminal, and a plurality of RF switches for opening/closing respective connections that provide an RF signal from respective inputs. Multichannel power combiners/dividers based on the Gysel principle, such as those disclosed in U.S. Patents 5,164,689 and 5,880,648, comprise a common output/input port, a plurality of input/output ports and a corresponding plurality of first and second transmission lines interconnecting the respective ports, which are implemented on planar substrates by the microstrip technology or with coaxial transmission lines for high power levels. However, these two types of schemes have limitations on the transmitted power levels, which usually do not exceed a few kW.

Another well known principle of combining/dividing power relies on the use of waveguide couplers, which use the principle of joining a set of waveguides in a single waveguide. In this case, input and output can be provided on the same type of waveguides (US 6,411,174; US 5,892,414) or with transformation of the wave type taking into account specific needs of the design, for example, using a coaxial- to-waveguide transition (US 2012/0025928) or rectangular-to circular waveguide transition (US 7,432,780). Power combiners of this type can operate at high power levels, but they have limitations on the number of power sources being combined, and have large sizes at low RF bands.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a device for combining RF power, which ensures a high stability of frequency and phase and features a compact size and low cost.

The object is accomplished in a device for combining

RF power, comprising a cavity, e.g. having a rectangular cross section, with a central (axial) cylindrical conductor; a set of inductive coupling elements for inputting RF power from a plurality of sources into the cavity, and a movable output element for outputting the combined power.

The cavity can be a cylindrical cavity, or can have a polygonal cross section.

The axial cylindrical conductor has a variable diameter, wherein the middle portion of the axial cylindrical conductor has a larger diameter. This allows increasing the amplitude of magnetic field near side walls of the cavity. The length of the cavity is approximately equal to half the wavelength, but may vary because the variation in the radius of the central conductor contributes to the conductivity of the oscillating circuit.

The inductive coupling elements (configured as coupling loops) for inputting RF power are disposed at the maximum of magnetic field amplitude. Such an arrangement provides the best coupling.

The movable output element for outputting the power combined in the cavity volume is configured as a coupling loop and secured on the axial cylindrical conductor.

In a possible embodiment a method for combining RF power according to the invention comprises:

providing a rectangular cavity with a central conductor disposed along the longitudinal axis of the cavity;

inputting RF power from a plurality of sources to the cavity via respective inductive coupling elements disposed at the maximum of magnetic field amplitude in the cavity; combining the RF power inputted from the plurality of sources in the cavity, and

outputting the combined RF power from the cavity via a movable coupling element secured on the central conductor.

Brief Description of the Drawings

The invention is illustrated by way of an example illustrated in the accompanying drawings, in which:

FIG.l shows schematically an embodiment of a device for combining RF power according to the invention;

FIG.2a shows the distribution of magnetic field in the cavity with a central conductor having a variable cross- section;

FIG.2b is a graph illustrating the distribution of the magnetic field amplitude along the length of the cavity; FIG.3a shows the distribution of electric field in the cavity with a central conductor having a variable cross- section;

FIG.3b is a graph illustrating the distribution of the electric field amplitude along the length of the cavity.

Description of Preferred Embodiment

As shown in Figure 1, the device for combining RF power according to the invention comprises a waveguide 1, a central (axial) cylindrical conductor 2 having a larger radius middle portion 3, elements 4 for inputting RF power from sources 5, configured as inductive coupling loops, and a movable output element 6 for outputting the combined RF power, secured on the central conductor 2. The cavity 1 has a length approximately equal to half the wavelength.

The RF power combining device operates in the following manner. RF power from sources 5 is inputted via the inductive RF power input elements 4 in the cavity 1. The inputted power from the plurality of sources 5 is combined in the cavity 1, where the distribution of electric and magnetic fields is set as illustrated in Figures 2a and 3a, respectively. Figures 3a and 3b show corresponding changes in the amplitudes of magnetic field and electric field along the length of the cavity, respectively .

The combined RF power is outputted from the cavity 1 via the movable combined RF power output member 6 secured on the central conductor 2.

The present power combiner combines power from up to 64 discrete sources. The number of sources, is chosen in accordance with the design tasks to be solved. The inventive scheme offers high stability of frequency and phase, and features a compact size and low cost.