Superconducting multi-path coupler based on impedance traction network

Abstract

The invention discloses a superconductive multi-path coupler based on an impedance traction network. Comprising a common end, a first tunable filter circuit, a second tunable filter circuit and a plurality of impedance traction networks, and the first tunable filter circuit comprises a first branch knot and a plurality of first tunable filters arranged on the first branch knot; the second tunable filter circuit comprises a second branch knot and a plurality of second tunable filters arranged on the second branch knot; and at least one of the signal input end and the signal output end of each first tunable filter and each second tunable filter is provided with an impedance traction network for adjusting the port reactance of the first tunable filter and the second tunable filter. The impedance traction network is arranged at the signal input end and / or the signal output end of the first tunable filter and the second tunable filter, and the port reactance of the first tunable filter and the second tunable filter can be adjusted on line, so that the passband return loss performance of the multi-path coupler is improved.

Description

A superconducting multiplexer based on an impedance traction network Technical Field

[0001] This invention relates to the field of ultra-shortwave communication technology, specifically to a superconducting multiplexer based on an impedance-pulling network. Background Technology

[0002] The VHF anti-jamming multiplexer is a key component of VHF anti-jamming communication systems, primarily composed of a tunable RF channel filter and a broadband multiplexing network. Using an VHF multiplexer, multiple transceiver stations can be connected to a single broadband antenna, enabling multiple RF channels. Each channel can be connected to one station for simultaneous transmission and reception with minimal interference between channels. Furthermore, superconducting technology possesses zero resistance; superconducting channel filters based on this technology can construct RF channels with both extremely low passband insertion loss and extremely fast out-of-band rejection. The VHF anti-jamming superconducting multiplexer, implemented using superconducting technology combined with a broadband multiplexing network, significantly improves the passband insertion loss and isolation between RF channels.

[0003] In related technologies, tunable multiplexers suffer from high return loss. Summary of the Invention

[0004] The purpose of this invention is to provide a superconducting multiplexer based on an impedance traction network to solve the problem of high return loss in tunable multiplexers in related technologies.

[0005] This invention provides a superconducting multiplexer based on an impedance-pulling network, comprising a common terminal, a first tunable filter circuit and a second tunable filter circuit respectively connected to the common terminal, and a plurality of impedance-pulling networks. The first tunable filter circuit includes a first stub and a plurality of first tunable filters disposed on the first stub. The second tunable filter circuit includes a second stub and a plurality of second tunable filters disposed on the second stub. At least one of the signal input and signal output terminals of each of the first and second tunable filters is provided with an impedance-pulling network for adjusting the port reactance of the first and second tunable filters.

[0006] Optionally, the impedance pulling network is provided at both the signal input and signal output terminals of the first tunable filter and the second tunable filter.

[0007] Optionally, the impedance pulling network includes a transmission line and a variable capacitor. In the impedance pulling network corresponding to the signal input terminal, one end of the transmission line is connected to the signal input terminal of the first tunable filter at a first node, and the other end of the transmission line is connected to one end of the variable capacitor, with the other end of the variable capacitor grounded. In the impedance pulling network corresponding to the signal output terminal, one end of the transmission line is connected to the signal output terminal of the first tunable filter at a second node, and the other end of the transmission line is connected to one end of the variable capacitor, with the other end of the variable capacitor grounded.

[0008] Optionally, the transmission line has a bent structure.

[0009] Optionally, the line width of the transmission line is 0.1mm-0.2mm.

[0010] Optionally, the material of the transmission line includes yttrium barium copper oxide.

[0011] Optionally, the first tunable filter and the second tunable filter each include a filter cavity, and the impedance pulling network is disposed within the filter cavity.

[0012] Optionally, the first tunable filter and the second tunable filter further include a plurality of resonators, which are located between the two impedance pulling networks.

[0013] Optionally, the signal input terminal is located on one side of the filter cavity, and the signal output terminal is located on the other side of the cavity. Each filter cavity includes a first impedance pulling network and a second impedance pulling network. The first impedance pulling network corresponds to the signal input terminal, and the second impedance pulling network corresponds to the signal output terminal. The first impedance pulling network is closer to the signal input terminal than the resonator, and the second impedance pulling network is closer to the signal output terminal than the resonator.

[0014] Optionally, the first tunable filter circuit includes six first tunable filters connected in parallel, and the second tunable filter circuit includes four second tunable filter circuits connected in parallel.

[0015] Compared with related technologies, by setting an impedance pulling network at the signal input and / or signal output terminals of the first and second tunable filters, the port reactance of the first and second tunable filters can be adjusted online, thereby improving the passband return loss performance of the multi-coupler. Attached Figure Description

[0016] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 is a topology diagram of a multi-channel coupler provided in comparison with the present invention; Figure 2 is a frequency response diagram of the multi-channel coupler in Figure 1; Figure 3 is a topology diagram of a superconducting multi-channel coupler according to an embodiment of the present invention; Figure 4 is a frequency response diagram of the superconducting multi-channel coupler in Figure 3; Figure 5 is a schematic diagram of the structure of a tunable filter provided in an embodiment of the present invention.

[0017] Figure reference numerals: 10-tunable filter; 11-filter cavity; 12-signal input terminal; 13-signal output terminal; 14-transmission line; 15-variable capacitor; 16-resonator; 21-first stub; 22-second stub. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] The inventors discovered that, as a type of multiplexer, this multiplexer includes a common terminal, a first filter circuit, and a second filter circuit. The first and second filter circuits are connected to the common terminal. The first and second filter circuits include multiple filters, and their communication channels are generally constructed using conventional materials (such as tunable filters with coaxial metal cavities forming the channel). Then, they are combined with a star-shaped or piecewise linear multiplexing network to form a multiplexer. Among them, the star-shaped or piecewise linear multiplexing network can achieve a wider operating frequency band. The schematic diagram of a 10-channel multiplexer operating in the VHF band is shown in Figure 1. When the tunable filter implemented with a coaxial metal cavity structure is applied to the tunable multiplexer, its input and output structure needs to be specially designed to ensure that the out-of-band reactance is less than one-quarter of the wavelength in the operating frequency band. Otherwise, a high-performance radio frequency channel cannot be formed. However, due to the non-stretchable nature of its material and the fact that it cannot be debugged online, the superconducting tunable filter is difficult to achieve the goal of input and output structures that are much smaller than one-quarter of the wavelength.

[0020] Therefore, the tunable multiplexer implemented by combining the superconducting tunable filter with the piecewise linear and star-shaped structures has two problems in practical implementation. First, because the out-of-band reactance of the superconducting tunable filter is relatively large and increases sharply with the number of channels, the channel ripple and return loss of the tunable multiplexer implemented by the star-shaped and piecewise linear structures will deteriorate sharply. In particular, the return loss index in the passband is often less than -10dB, which affects the normal use of the multiplexer (as a comparative example of this invention, the performance of a 10-channel multiplexer is shown in Figure 2). Second, the superconducting multiplexer needs to operate at a liquid nitrogen temperature of 77K. Therefore, the length of the transmission line on the broadband multiplexer network cannot be tuned online in real time. Each experiment must be tuned at room temperature, then slowly cooled to the superconducting temperature to test its performance, and then slowly restored to room temperature before the second tuning can be performed. This will result in a huge amount of debugging work for the superconducting multiplexer.

[0021] As shown in Figures 3 and 5, based on this, the present invention provides a superconducting multiplexer based on an impedance traction network. The superconducting multiplexer based on the impedance traction network includes a common terminal, a first tunable filter circuit and a second tunable filter circuit respectively connected to the common terminal, and multiple impedance traction networks.

[0022] The first tunable filter circuit includes a first branch 21 and a plurality of first tunable filters 10 disposed on the first branch 21. The plurality of first tunable filters 10 are connected in parallel to the first branch 21. The second tunable filter circuit includes a second branch 22 and a plurality of second tunable filters 10 disposed on the second branch 22. The plurality of second tunable filters 10 are connected in parallel to the second branch 22. The first branch 21 and the second branch 22 are connected to a common node, which is connected to a common terminal. At least one of the signal input terminal 12 and the signal output terminal 13 of each first tunable filter 10 and the second tunable filter 10 is provided with an impedance traction network for adjusting the port reactance of the first tunable filter 10 and the second tunable filter 10. In other words, for the first tunable filter 10, an impedance pulling network can be set at the signal input terminal 12 and the signal output terminal 13 of the first tunable filter 10. For the second tunable filter 10, an impedance pulling network can be set at the signal input terminal 12 and the signal output terminal 13 of the second tunable filter 10. That is to say, at least one of the signal input terminal 12 and the signal output terminal 13 of the first tunable filter 10 and at least one of the signal input terminal 12 and the signal output terminal 13 of the second tunable filter 10 need to be provided with an impedance pulling network.

[0023] In this invention, by setting an impedance pulling network at the signal input terminal 12 and / or signal output terminal 13 of the first tunable filter 10 and the second tunable filter 10, the port reactance of the first tunable filter 10 and the second tunable filter 10 can be adjusted online, thereby improving the passband return loss performance of the multi-coupler.

[0024] Figure 4 is a frequency response characteristic curve of the superconducting multiplexer provided in the embodiment of the present invention. As shown in Figure 4, the superconducting multiplexer of the present invention has a passband return loss of better than -12dB for its 10 communication channels, and the in-band ripple is also improved, thereby optimizing the performance of the superconducting multiplexer.

[0025] In this invention, both the signal input terminal 12 and the signal output terminal 13 of the first tunable filter 10 and the second tunable filter 10 are provided with impedance pulling networks. That is, each tunable filter 10 is provided with two impedance pulling networks. Compared with providing impedance pulling networks only at the signal input terminal 12 or the signal output terminal 13 of the tunable filter 10, the port reactances of the signal input terminal 12 and the signal output terminal 13 can be adjusted online at the same time, thereby further improving the return loss performance of the multi-coupler.

[0026] As shown in Figure 5, in this invention, the impedance pulling network includes a transmission line 14 and a variable capacitor 15. In the impedance pulling network corresponding to the signal input terminal 12, one end of the transmission line 14 is connected to the signal input terminal 12 of the first tunable filter 10 at a first node, and the other end of the transmission line 14 is connected to one end of the variable capacitor 15, with the other end of the variable capacitor 15 grounded. In the impedance pulling network corresponding to the signal output terminal 13, one end of the transmission line 14 is connected to the signal output terminal 13 of the first tunable filter 10 at a second node, and the other end of the transmission line 14 is connected to one end of the variable capacitor 15, with the other end of the variable capacitor 15 grounded. Therefore, by controlling the magnitude of the DC voltage (e.g., V1, V2, etc. in Figure 5) input to one end of the feedthrough capacitor connected to the variable capacitor 15, the magnitude of the variable capacitor 15 can be adjusted. This allows for the adjustment of the parallel reactance of the impedance traction network, thereby enabling online adjustment of the port reactance of the signal input terminal 12 and the signal output terminal 13. This improves the passband return loss performance of the multiplexer and significantly reduces the debugging time of the superconducting multiplexer. Online adjustment of the port reactance by adjusting the capacitance of the variable capacitor 15 is more convenient and faster than tuning by changing the transmission line length.

[0027] The transmission line 14 can be configured as a bent structure, that is, the transmission line 14 can be in a serpentine bend. This is conducive to making reasonable use of space, saving the arrangement space of the transmission line 14, and realizing the arrangement of a longer transmission line 14 in a smaller space, thereby significantly reducing the overall size of the filter and realizing the miniaturization of the filter.

[0028] Furthermore, the linewidth of transmission line 14 is 0.1mm-0.2mm. For example, the linewidth of transmission line 14 can be set to 0.11mm, 0.12mm, 0.13mm, 0.14mm, 0.15mm, 0.16mm, 0.17mm, 0.18mm, 0.19mm, or 0.2mm. The linewidth of transmission line 14 directly affects its inductance and capacitance per unit length, and thus affects its characteristic impedance. For example, when the linewidth increases, the area between the transmission line and the ground plane increases, the capacitance per unit length of transmission line 14 increases accordingly, and the inductance of transmission line 14 decreases, resulting in a smaller characteristic impedance. If the linewidth of transmission line 14 deviates from the above range, it will lead to increased signal reflection and standing wave ratio. The transmission line 14 can be made of yttrium barium copper oxide, which has a critical temperature of about 92K, higher than the boiling point of liquid nitrogen of 77K. This provides an easily achievable condition for a superconducting environment, allowing for direct cooling using relatively inexpensive and easy-to-maintain liquid nitrogen or a small electric chiller, avoiding the use of expensive and complex cooling systems. At the same time, yttrium barium copper oxide has a lower surface resistance and higher current density than ordinary materials in a superconducting environment, and is also more compatible with the substrate of the filter cavity.

[0029] As shown in Figure 5, in this invention, the first tunable filter 10 and the second tunable filter 10 each include a filter cavity 11, and an impedance pulling network is disposed inside the filter cavity 11. By disposing the first tunable filter 10 and the second tunable filter 10 inside the filter cavity 11, compared to disposing the impedance pulling network outside the filter cavity 11, the length of the transmission line 14 can be reduced. If the length of the transmission line 14 is too large, it is not convenient for the miniaturization design of the filter. Therefore, reducing the length of the transmission line 14 can ensure the normal transmission of the signal. Thus, the transmission line of the impedance pulling network and the filter are integrated together on the substrate of the filter cavity.

[0030] As shown in Figure 5, in this invention, the first tunable filter 10 and the second tunable filter 10 each include a plurality of resonators 16, which are located between two impedance pulling networks. The plurality of resonators 16 are arranged in a U-shape, which can change the electromagnetic coupling mode between the resonators.

[0031] Since the superconducting circuit substrate can be a lanthanum aluminate substrate with a relative permittivity of 23.75, if the length of the transmission line 14 is 1 mm, then the length of the transmission line 14 in the filter cavity 11 is equivalent to 5 times that of the transmission line 14 in air, i.e., 5 mm. Therefore, the length of the transmission line 14 should be as short as possible (making the transmission line 14 as short as possible while ensuring the same reactance). Therefore, in this invention, the transmission line 14 is set close to the signal input terminal 12 or the signal output terminal 13 of the tunable filter 10. Specifically, the signal input terminal 12 is located on one side of the filter cavity 11, and the signal output terminal 13 is located on the other side of the cavity. Each filter cavity 11 includes a first impedance pulling network and a second impedance pulling network. The first impedance pulling network corresponds to the signal input terminal 12, and the second impedance pulling network corresponds to the signal output terminal 13. The first impedance pulling network is closer to the signal input terminal 12 than the resonator 16, and the second impedance pulling network is closer to the signal output terminal 13 than the resonator 16. The impedance pulling network is set close to the signal input terminal or the signal output terminal.

[0032] In this invention, the first tunable filter circuit includes six parallel first tunable filters 10, and the second tunable filter circuit includes four parallel second tunable filters 10. Thus, the superconducting multiplexer of this invention can form 10 communication channels to meet the simultaneous information transmission and reception needs of multiple radio stations. The superconducting multiplexer can operate in the VHF band (108MHz-174MHz).

[0033] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0034] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A superconducting multiplexer based on an impedance-pulling network, characterized in that, The system includes a common terminal, a first tunable filter circuit and a second tunable filter circuit respectively connected to the common terminal, and a plurality of impedance pulling networks. The first tunable filter circuit includes a first stub and a plurality of first tunable filters disposed on the first stub. The second tunable filter circuit includes a second stub and a plurality of second tunable filters disposed on the second stub. At least one of the signal input terminal and the signal output terminal of each first tunable filter and the second tunable filter is provided with an impedance pulling network for adjusting the port reactance of the first tunable filter and the second tunable filter.

2. The superconducting multi-channel coupler based on an impedance traction network according to claim 1, characterized in that, The impedance pulling network is provided at both the signal input and signal output terminals of the first tunable filter and the second tunable filter.

3. The superconducting multiplexer based on an impedance traction network according to claim 1 or 2, characterized in that, The impedance pulling network includes a transmission line and a variable capacitor. In the impedance pulling network corresponding to the signal input terminal, one end of the transmission line is connected to the signal input terminal of the first tunable filter at a first node, and the other end of the transmission line is connected to one end of the variable capacitor, with the other end of the variable capacitor grounded. In the impedance pulling network corresponding to the signal output terminal, one end of the transmission line is connected to the signal output terminal of the first tunable filter at a second node, and the other end of the transmission line is connected to one end of the variable capacitor, with the other end of the variable capacitor grounded.

4. The superconducting multiplexer based on an impedance-pulling network according to claim 3, characterized in that, The transmission line has a bent structure.

5. The superconducting multi-channel coupler based on an impedance traction network according to claim 4, characterized in that, The line width of the transmission line is 0.1mm-0.2mm.

6. The superconducting multiplexer based on an impedance-pulling network according to claim 4, characterized in that, The transmission line is made of yttrium barium copper oxide.

7. The superconducting multi-channel coupler based on an impedance traction network according to claim 3, characterized in that, The first tunable filter and the second tunable filter each include a filter cavity, and the impedance pulling network is disposed in the filter cavity.

8. The superconducting multi-coupler based on an impedance traction network according to claim 7, characterized in that, The first tunable filter and the second tunable filter each include a plurality of resonators located between the two impedance pulling networks.

9. The superconducting multiplexer based on an impedance traction network according to claim 8, characterized in that, The signal input terminal is located on one side of the filter cavity, and the signal output terminal is located on the other side of the cavity. Each filter cavity includes a first impedance traction network and a second impedance traction network. The first impedance traction network corresponds to the signal input terminal, and the second impedance traction network corresponds to the signal output terminal. The first impedance traction network is closer to the signal input terminal than the resonator, and the second impedance traction network is closer to the signal output terminal than the resonator.

10. The superconducting multiplexer based on an impedance-pulling network according to claim 1, characterized in that, The first tunable filter circuit includes six first tunable filters connected in parallel, and the second tunable filter circuit includes four second tunable filter circuits connected in parallel.

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