A high Q-value tunable superconducting band-pass filter capable of improving return loss

Abstract

The application relates to a high-Q tunable superconducting band-pass filter capable of improving echo loss, comprising a filter circuit; the filter circuit comprises a plurality of superconducting resonators and a secondary coupling line arranged between adjacent superconducting resonators; the superconducting resonator is loaded with at least two first varactor tubes; and the secondary coupling line is loaded with a second varactor tube and a direct-current blocking capacitor. By loading the tunable secondary coupling line between the resonators, the coupling coefficient between the resonators can be adjusted, and the echo in the filter band can be improved; by loading a plurality of first varactor tubes in parallel, the Q value of the overall circuit can be effectively improved, and the performance of the tunable filter is improved.

Description

Technical Field

[0001] This invention relates to the field of microwave radio frequency communication technology, and specifically to a high-Q tunable superconducting bandpass filter that can improve return loss. Background Technology

[0002] A tunable superconducting filter is a superconducting microwave device whose center frequency or bandwidth can be changed drastically. Tunable superconducting filters made using superconducting films not only have advantages such as high sensitivity, strong anti-interference capability, and small size and weight, but also significantly reduce system size and increase system stability when replacing switched filter banks. Furthermore, because their frequency can be continuously varied, they increase the receiver's frequency band coverage and enhance compatibility.

[0003] Existing tunable superconducting bandpass filters adjust the resonant frequency of the resonator by regulating the voltage of the gallium arsenide varactor diode, thereby adjusting the filter's passband. However, because this method cannot adjust the coupling coefficient between the resonators, adjusting the filter's passband will cause a deterioration in-band echo. Summary of the Invention

[0004] The purpose of this invention is to provide a high-Q tunable superconducting bandpass filter that can improve return loss. This high-Q tunable superconducting bandpass filter can overcome the shortcomings of the prior art, filter out interference signals, and realize frequency hopping and high-quality communication in the signal path of microwave communication systems.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A high-Q tunable superconducting bandpass filter with improved return loss includes a filter circuit. The filter circuit comprises several superconducting resonators and secondary coupling lines disposed between adjacent superconducting resonators. Each superconducting resonator is loaded with at least two first varactor diodes. The secondary coupling lines are loaded with second varactor diodes and DC blocking capacitors. The parallel loading of two or more first varactor diodes on the superconducting resonators effectively improves the Q value of the circuit, thus better enhancing the performance of the filter and related systems.

[0007] Furthermore, the superconducting resonator includes a positive terminal, a negative terminal, a current-limiting resistor, and a current-limiting resistor; one end of the positive terminal is connected to a power source, and the other end is connected to the first end of the current-limiting resistor; one end of the negative terminal is connected to a power source, and the other end is connected to the first end of the current-limiting resistor; one end of the first varactor is connected to the second end of the current-limiting resistor, and the other end is connected to the second end of the current-limiting resistor; each of the first varactors is connected in parallel.

[0008] Furthermore, the secondary coupling line includes a coupling transmission line; a current-limiting resistor three and a current-limiting resistor four are also loaded on the secondary coupling line; one end of the current-limiting resistor three is connected to the first end of the coupling transmission line, and the other end is connected to a positive terminal two; one end of the current-limiting resistor four is connected to the second end of the coupling transmission line, and the other end is connected to a negative terminal two; one end of the second varactor is connected to the node between the coupling transmission line and the current-limiting resistor three, and the other end is connected to one end of the DC blocking capacitor, the other end of which is connected to the node between the coupling transmission line and the current-limiting resistor four.

[0009] Furthermore, it also includes a filter cavity; the filter circuit is installed inside the filter cavity; the filter cavity is provided with an input connector and an output connector.

[0010] Furthermore, the superconducting resonator adopts a half-wavelength resonator structure; the secondary coupling line adopts a ring resonator structure.

[0011] Furthermore, the first varactor is connected in parallel on the superconducting resonator; both the first and second varactors are tuning elements of the tunable filter, and both are gallium arsenide varactors.

[0012] Furthermore, the filter cavity is provided with a feedthrough capacitor for connecting the power supply terminal to the power source.

[0013] Furthermore, the filter circuit has an input terminal and an output terminal at its two ends; the input terminal is connected to the input connector; and the output terminal is connected to the output connector.

[0014] Furthermore, the superconducting resonator, the input terminal, the output terminal, and the secondary coupling line are all in microstrip form, and all three are made of superconducting materials.

[0015] Furthermore, both the input connector and the output connector are any one or more combinations of SMA, N, and DIN.

[0016] Compared with the prior art, the advantages of the present invention are:

[0017] (1) This invention improves the in-band echo of the filter by loading a tunable secondary coupling line between the resonators, thereby enabling the coupling coefficient between the resonators to be adjustable. By loading a second varactor tube onto the secondary coupling line, this invention can adjust the secondary coupling between the resonators while simultaneously adjusting the resonant frequency, effectively improving the in-band echo of the superconducting bandpass filter.

[0018] (2) By loading multiple first varactor transistors in parallel, this invention can effectively improve the Q value of the overall circuit and enhance the performance of the tunable filter. By adjusting the varactor transistors on the resonator and the secondary coupling line, the resonant frequency and coupling coefficient of the resonator can be adjusted simultaneously, so that the filter can improve the in-band echo while adjusting the frequency, thereby better improving the performance of the related system. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the high-Q tunable superconducting bandpass filter in this invention;

[0020] Figure 2 This is a schematic diagram of the filter cavity structure in this invention.

[0021] in:

[0022] 1. Input terminal, 2. Output terminal, 3. Superconducting resonator, 4. Secondary coupling line, 5. First varactor tube, 6. Positive power-on terminal two, 7. Current-limiting resistor four, 8. DC blocking capacitor, 9. Filter circuit, 10. Input connector, 11. Output connector, 12. Feedthrough capacitor, 13. Filter cavity. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings:

[0024] like Figure 1 and Figure 2 The diagram illustrates a high-Q tunable superconducting bandpass filter that improves return loss. It includes a filter circuit 9; the filter circuit 9 comprises several superconducting resonators 3 and secondary coupling lines 4 disposed between adjacent superconducting resonators 3; each superconducting resonator 3 is loaded with at least two first varactor tubes 5; the secondary coupling line 4 is loaded with a second varactor tube and a DC blocking capacitor 8. The first varactor tubes, second varactor tubes, and DC blocking capacitors are loaded by welding or bonding. The number of secondary coupling lines 4 is one less than the number of superconducting resonators 3, with one secondary coupling line 4 between two adjacent superconducting resonators 3. The secondary coupling lines between adjacent resonators are loaded with varactor tubes. By adjusting the capacitance of the varactor tubes, the coupling between the resonators is changed, thereby improving return loss at different frequencies. The secondary coupling line 4, loaded with a second varactor tube, can adjust the secondary coupling between resonators while adjusting the resonant frequency, effectively improving the in-band return of the superconducting bandpass filter. The superconducting resonator 3 is connected in parallel with two or more first varactor transistors 5, which can effectively improve the Q value of the circuit and better improve the performance of the filter and related systems. The secondary coupling line is protected from short circuit by loading a DC blocking capacitor 8.

[0025] Furthermore, the superconducting resonator 3 includes a positive terminal, a negative terminal, a current-limiting resistor, and a second current-limiting resistor. One end of the positive terminal is connected to a power source, and the other end is connected to the first terminal of the first current-limiting resistor. One end of the negative terminal is connected to a power source, and the other end is connected to the first terminal of the second current-limiting resistor. One end of the first varactor tube 5 is connected to the second terminal of the first current-limiting resistor, and the other end is connected to the second terminal of the second current-limiting resistor. The first varactor tubes 5 are connected in parallel. An external power source applies voltage to the first varactor tubes through the terminals to adjust the capacitance of the first varactor tubes.

[0026] Furthermore, the secondary coupling line 4 includes a coupling transmission line; a current-limiting resistor three and a current-limiting resistor four 7 are also loaded on the secondary coupling line 4; one end of the current-limiting resistor three is connected to the first end of the coupling transmission line, and the other end is connected to a positive terminal 6; one end of the current-limiting resistor four 7 is connected to the second end of the coupling transmission line, and the other end is connected to a negative terminal 2; one end of the second varactor is connected to the node between the coupling transmission line and the current-limiting resistor three, and the other end is connected to one end of the DC blocking capacitor 8, the other end of which is connected to the node between the coupling transmission line and the current-limiting resistor four 7. The current-limiting resistor three and the line resistor four are used to limit the current of the external power supply to prevent the current from exceeding the threshold of the varactor.

[0027] Furthermore, it also includes a filter cavity 13; the filter circuit 9 is installed inside the filter cavity 13; the filter cavity 13 is provided with an input connector 10 and an output connector 11. The filter cavity 13 is used for magnetic shielding of the superconducting circuit, facilitating cooling and connection with other devices.

[0028] Furthermore, the superconducting resonator 3 adopts a half-wavelength resonator structure; the secondary coupling line 4 adopts a ring resonator structure.

[0029] Furthermore, the first varactor 5 is connected in parallel to the superconducting resonator 3; both the first varactor 5 and the second varactor are tuning elements of the tunable filter, and both are gallium arsenide varactors. By changing the applied voltage, the varactor can change the resonant frequency of the resonator, thereby achieving adjustable circuit frequency bands.

[0030] Furthermore, the filter cavity 13 is provided with a feedthrough capacitor 12 for connecting the power supply terminals to the power source. Each power supply terminal is connected to the power source through the feedthrough capacitor on the cavity. The power supply terminals are soldered to the feedthrough capacitor 12. External power is conveniently supplied through the feedthrough capacitor.

[0031] Furthermore, the filter circuit 9 has an input terminal 1 and an output terminal 2 at its two ends; the input terminal 1 is welded to the input connector 10; and the output terminal 2 is welded to the output connector 11.

[0032] Furthermore, the superconducting resonator 3, the input terminal 1, the output terminal 2, and the secondary coupling line 4 are all in microstrip form, and all three are made of superconducting material. Preferably, the superconducting material is YBCO. The superconducting microstrip circuit facilitates the assembly of varactor diodes.

[0033] Furthermore, the input connector 10 and the output connector 11 are any one or more combinations of SMA, N, and DIN.

[0034] In summary, this invention improves the in-band echo of the filter by loading a tunable secondary coupling line between the resonators, thereby enabling adjustable coupling coefficients. By loading a second varactor diode onto the secondary coupling line, the invention can adjust the secondary coupling between the resonators simultaneously with adjusting the resonant frequency, effectively improving the in-band echo of the superconducting bandpass filter. By loading multiple first varactor diodes in parallel, this invention effectively increases the Q value of the overall circuit, improving the performance of the tunable filter. By adjusting the resonators and the varactor diodes on the secondary coupling line, the resonant frequency and coupling coefficient can be adjusted simultaneously, allowing the filter to improve in-band echo while adjusting the frequency, thus better improving the performance of the related system.

[0035] The above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A high-Q tunable superconducting bandpass filter that can improve return loss, characterized in that, The system includes a filter circuit; the filter circuit includes a plurality of superconducting resonators and a secondary coupling line disposed between adjacent superconducting resonators; each superconducting resonator is loaded with at least two first varactor tubes; the secondary coupling line is loaded with a second varactor tube and a DC blocking capacitor; The secondary coupling line includes a coupling transmission line; a current-limiting resistor three and a current-limiting resistor four are also loaded on the secondary coupling line; one end of the current-limiting resistor three is connected to the first end of the coupling transmission line, and the other end is connected to a positive terminal two; one end of the current-limiting resistor four is connected to the second end of the coupling transmission line, and the other end is connected to a negative terminal two; one end of the second varactor is connected to the node between the coupling transmission line and the current-limiting resistor three, and the other end is connected to one end of the DC blocking capacitor, the other end of which is connected to the node between the coupling transmission line and the current-limiting resistor four.

2. The high-Q tunable superconducting bandpass filter with improved return loss according to claim 1, characterized in that, The superconducting resonator includes a positive terminal, a negative terminal, a current-limiting resistor, and a current-limiting resistor. One end of the positive terminal is connected to a power source, and the other end is connected to the first terminal of the current-limiting resistor. One end of the negative terminal is connected to a power source, and the other end is connected to the first terminal of the current-limiting resistor. One end of the first varactor is connected to the second terminal of the current-limiting resistor, and the other end is connected to the second terminal of the current-limiting resistor. The first varactors are connected in parallel.

3. A high-Q tunable superconducting bandpass filter with improved return loss according to claim 1, characterized in that, It also includes a filter cavity; the filter circuit is installed in the filter cavity; the filter cavity is provided with an input connector and an output connector.

4. A high-Q tunable superconducting bandpass filter with improved return loss according to claim 1, characterized in that, The superconducting resonator adopts a half-wavelength resonator structure; the secondary coupling line adopts a ring resonator structure.

5. A high-Q tunable superconducting bandpass filter with improved return loss according to claim 1, characterized in that, The first varactor is connected in parallel on the superconducting resonator; both the first and second varactors are tuning elements of the tunable filter, and both are gallium arsenide varactors.

6. A high-Q tunable superconducting bandpass filter with improved return loss according to claim 3, characterized in that, The filter cavity is equipped with a feedthrough capacitor for connecting the power supply terminal to the power source.

7. A high-Q tunable superconducting bandpass filter with improved return loss according to claim 3, characterized in that, The filter circuit has an input terminal and an output terminal at its two ends; the input terminal is connected to the input connector; and the output terminal is connected to the output connector.

8. A high-Q tunable superconducting bandpass filter with improved return loss according to claim 7, characterized in that, The superconducting resonator, the input terminal, the output terminal, and the secondary coupling line are all in microstrip form, and all three are made of superconducting materials.

9. A high-Q tunable superconducting bandpass filter with improved return loss according to claim 3, characterized in that, Both the input connector and the output connector are combinations of any one or more of SMA, N, and DIN.

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