1. Field of the Invention
The present invention relates to a mode converter and rotary joint of microwave, and more particularly to a multi-channel mode converter and rotary joint operating with a series of TE or TM mode electromagnetic wave.
2. Description of the Prior Art
Mode converters can transform a mode of electromagnetic wave to another mode of electromagnetic wave. For example, when using rotary joints for radar system and satellite system, mode converters can transform communication electromagnetic wave from general transmission mode to another mode which exempts from rotating influence or transform back without energy loss. As to dual channel mode converters, conventionally, two different modes of electromagnetic wave are used for operation and different mode converters must be designed accordingly, which makes the structure of the dual channel mode converter more complicated and limits the channel number. Besides, TEM mode electromagnetic wave is required in outer channels for operating conventional multi-channel converters, and TEM electromagnetic wave leads to heavy energy loss.
To solve the problems mentioned above, a multi-channel mode converter and rotary joint should be developed.
The present invention is directed to a multi-channel mode converter and rotary converter operating with a series of TE or TM mode electromagnetic wave, wherein a plurality of coaxial waveguides are sleeved to each other and each of them respectively induces electromagnetic wave in proper mode to obtain high power and high purity electromagnetic wave and prevent crosstalk between each coaxial waveguide.
According to an embodiment, the multi-channel mode converter operating with a series of TE or TM mode electromagnetic wave comprises a waveguide element. The waveguide element comprises a first mode converting structure and a second mode converting structure. The first mode converting structure comprises a first waveguide and N first rectangular waveguides, wherein N is a positive integer greater than 1. The first waveguide has a circular outer interface. A first port of the N first rectangular waveguides is respectively connected to the outer interface of the first waveguide and arranged uniform radially. A long axis of the first port of the N first rectangular waveguides is axially parallel to the first waveguide. A second port of the N first rectangular waveguides forms at least one first output/input port of the first mode converting structure. The second mode converting structure comprises a second waveguide and M second rectangular waveguides, wherein M is a positive integer greater than 1. The second waveguide has an outer interface and an inner interface which are circular and arranged coaxially. The first waveguide is sleeved into the second waveguide. A first port of the M second rectangular waveguides is respectively connected to the outer interface of the second waveguide and arranged uniform radially. A long axis of the first port of the second rectangular waveguide is axially parallel to the second waveguide. A second port of the M second rectangular waveguides forms at least one first output/input port of the second mode converting structure, wherein a port of the first waveguide and the second waveguide respectively forms a second output/input port of the second mode converting structure.
According to another embodiment, the multi-channel mode rotary joint operating with a series of TE or TM mode electromagnetic wave comprises two aforementioned waveguide elements. The two waveguide elements are arranged coaxially as the second output/input ports of the first mode converting structure and the second mode converting structure are arranged in opposition.
The objective, technologies, features and advantages of the present invention will become more apparent from the following description in conjunction with the accompanying drawings, wherein certain embodiments of the present invention are set forth by way of illustration and examples.
The foregoing aspects and many of the accompanying advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
The detail description is provided below and the preferred embodiments described are only for the purpose of description rather than for limiting the present invention.
When using rotary joint for operation, electromagnetic wave must exempt from rotating influence and conforms to circular symmetry of electromagnetic field, for example, TE01 mode electromagnetic wave with properties of torodial surface current. Radius ro and ri of outer conductors and inner conductors of coaxial structures can be changed to obtain extra freedoms to adjust and perform electromagnetic wave separation. However, it is a severe challenge to transform coaxial TE01 mode electromagnetic wave with high purity because low order parasitic mode wave may increase dramatically with decreasing radius ratio to cause harmful mode competition. In multi-channel system, electromagnetic wave under low order parasitic mode wave may further cause crosstalk between channels.
Cutoff frequency of coaxial TEmn mode electromagnetic wave can be founded by deriving the characteristic value xmn from the equation (1) to find the boundary in the system's frequency response.
J
m′(xmn)Ym′(xmnri/ro)−Jm′(xmnri/ro)Ym′(xmn)=0 (1)
Wherein, Jm′ and Ym′ are firth derivatives of the first kind and second kind of Bessel functions. When the radius ro of outer conductor is much greater than the radius ri of the inner conductor, Ym′(xmnri/ro) approaches infinity, and equation (1) can be simplified as Jm′(xmn)=0, which can determine the cutoff frequency of the circular waveguide. Referring to
According to an embodiment of the present invention, the multi-channel mode converter operating with a series of TE or TM mode electromagnetic wave comprises a waveguide element. The waveguide element can be one piece device or composed of multiple devices. Referring to
Referring to
The first mode converting structure 10a comprises a first waveguide 11a and N first rectangular waveguides 12a, wherein N is a positive integer greater than 1. The first waveguide 11a has an outer interface 111a and an inner interface 112a which are circular and coaxially arranged. In other words, the first waveguide 11a is a coaxial waveguide. A first port of the N first rectangular waveguides is respectively connected to the outer surface 111a of the first waveguide and the long axis of the first port is axially parallel to the first waveguide 11a. Besides, The N first rectangular waveguides 12a are uniform radially arranged around the first waveguide 11a. A second port of the N first rectangular waveguides forms at least one first output/input port 13a of the first mode converting structure 10a. A port of the first waveguide 11a forms a second output/input port 14a of the first mode converting structure 10a.
The second mode converting structure 10b comprises a second waveguide 11b and M second rectangular waveguides 12b, wherein M is a positive integer greater 1. Similarly, the second wave guide 11b has an outer interface 111b and an inner interface 112b which are circular and arranged coaxially. The first waveguide 11a is sleeved into the second waveguide 11b. It could be understood that the inner interface 112b of the second waveguide 11b is larger than the outer interface 111a of the first waveguide 11a. A first port of the M second rectangular waveguides 12b is respectively connected to the outer interface 11b of the second waveguide 11b and the long axis of the first port is axially parallel to the second waveguide 11b. Besides, the M second rectangular waveguides 12 surround the second waveguide 11b uniform radially. A second port of the M second rectangular waveguides 12b forms at least one first output/input port 14b of the second mode converting structure 10b and a port of the second waveguide 11b forms a second output/input port 14b of the second mode converting structure 10b.
The third mode converting structure 10c comprises a third waveguide 11c and L third rectangular waveguides 12c, wherein L is a positive integer greater than 1. Similarly, the third waveguide 11c has an outer interface 111c and an inner interface 112c which are circular and coaxially arranged, and the second waveguide 11b is sleeved into the third waveguide 11c. A first port of the L third rectangular waveguides 12c is respectively connected to the outer interface 111c of the third waveguide 11c and the long axis of the first port is axially parallel to the third waveguide 11c. Besides, the L third rectangular waveguides 12c surround the third waveguide 11c uniform radially. A second port of the L second rectangular waveguides 12c forms at least one first output/input port 13c of the third mode converting structure 10c. A port of the third waveguide 11c forms a second output/input port 14c of the third mode converting structure 10c.
According to an embodiment, the first port of the first rectangular waveguide 12a, the second rectangular waveguide 12b and the third rectangular waveguide 12c can be tetragonal symmetry in shape. In one embodiment, the waveguide element can comprises at least one plate conductor (not shown in the figure) which covers the first port of at least one of the first rectangular waveguide 12a, the second rectangular waveguide 12b and the third rectangular waveguide 12c, and the plate conductor has at least one coupling aperture which is column shaped and tetragonal symmetry. The long axis of the coupling aperture is axially parallel to the first waveguide 11a, the second waveguide 11b and the third waveguide 11c. Other coupling structures which can stimulate mode electromagnetic wave while operating shall fall with the spirit and the scope of the present invention.
According to an embodiment, the second ports of the plurality of the first rectangular waveguides 12a can converge into a single port, which is the first output/input port 13a of the first mode converting structure 10a. Similarly, the second ports of the plurality of the second rectangular waveguides 12b and the third rectangular waveguides 12c can respectively converge into a single port, which are the first output/input port 13b of the second mode converting structure 10b and the first output/input port 13c of the third mode converting structure 10c.
Take the first mode converting structure 10a for example. A mode electromagnetic wave is provided at the N first waveguides 12a around the first waveguides 11a, wherein the electrical field direction is axially orthogonal to the first waveguide 11a, for example but not limited to TE10 mode. Therefore, the electrical field direction of the electromagnetic wave provided at the first rectangular waveguides 12a which uniformly surround the first waveguide 11a deflects clockwise or counterclockwise; energy and phase of each electromagnetic wave provided at the first rectangular waveguide 12a is the same, thereby stimulating TE01 mode electromagnetic wave with circle electrical field at the first waveguide 11a.
In order to generate electromagnetic wave with equal energy and phase, the number N of the first rectangular waveguide 12a is equal to 2n, wherein n is a positive integer greater than or equal to 2. Besides, every two adjacent of the first rectangular waveguides 12a gradually converge into a Y-shaped or T-shaped structure and finally converge into a single port, i.e. the first output/input port 13a. Accordingly, each Y-shaped or T-shaped structure can be an energy splitter, which allows the single input port to generate electromagnetic waves with equal energy and phase at multiple output ports. In an embodiment, the number M of the second rectangular waveguides 12b is equal to 2n, wherein the n is a positive integer greater than or equal to 3; the number L of the third rectangular waveguide 12c is equal to 2n, wherein the n is a positive integer greater than or equal to 4.
Referring to
As known, azimuthal component presents as Γ=m+jN, wherein N is the number of electromagnetic waves entering the coaxial waveguides, that is the number of the rectangular waveguides 12a, 12b and 12c, j=0, ±1, ±2, . . . . For the TE01 mode electromagnetic wave, m=0, so that Γ=0, ±4, ±8 . . . . Take the first mode converting structure 10a for example. When frequency is higher than the cutoff frequency, TE01, TE41, TE81 . . . mode electromagnetic waves are stimulated correspondingly. As shown in
In one embodiment, the radius of the outer interface 111a of the first waveguide 11a of the first mode converting structure 10a is 2.43 mm and 0.60 mm is for the inner interface 112a; the radius ratio ro/ri is 4.05. Simulation results by using the software, High Frequency Structure Simulator (HFSS), which is developed by Ansoft, are demonstrated in
The radius of the outer interface 111b of the second waveguide 11b of the second mode converting structure 10b is 4.60 mm and 2.80 mm is for the inner interface; the radius ratio ro/ri is 1.64. Simulation results are demonstrated in
The radius of the outer interface 111c of the third waveguide 11c of the third mode converting structure 10c is 7.20 mm and 5.30 mm is for the inner interface; the radius ratio ro/ri is 1.36. Simulation results are demonstrated in
It should be noticed that the innermost layer, i.e. the first waveguide 11a, is described in the form of coaxial waveguide, but not limited to this. People who are skilled in art shall understand that the first waveguide 11a also can be a circle waveguide, that is to say, even though there is no inner interface 112a, the multi-channel mode converter operating with a series of TE or TM mode electromagnetic wave of the present invention still can be fulfilled.
Referring to
It should be noticed that TE01 mode electromagnetic wave is used while operating in aforementioned embodiments, but not limited to this. People who are skilled in art shall understand that other TE modes or TM series mode electromagnetic waves also can be used while operating. For example, by properly designing the spacing structure between two waveguide elements to form a choke type rotary joint, energy of radial direction can be decreased and further reduces crosstalk between channels.
In conclusion, the present invention relates to a multi-channel mode converter and rotary joint operating with a series of TE or TM mode electromagnetic wave, wherein a plurality of coaxial waveguides are sleeved to each other. By controlling radius ratio of each coaxial waveguide and the number of the coupling apertures, high power and high purity electromagnetic wave can be obtained and major competition mode electromagnetic waves can be suppressed, which prevents crosstalk between each coaxial waveguide.
While the invention is susceptible to various modifications and alternative forms, a specific example thereof has been shown in the drawings and is herein described in detail. It should be understood, however, that the invention is not to be limited to the particular form disclosed, but to the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the appended claims.
Number | Date | Country | Kind |
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101110559 | Mar 2012 | TW | national |