A high-temperature superconducting equi-ridge broadband balanced bandpass filter

Abstract

The application discloses a high-temperature superconducting equal-ridge broadband balanced band-pass filter, which comprises a dielectric substrate, a YBCO high-temperature superconducting film grounding plate, a YBCO high-temperature superconducting film layer and a filter circuit formed on the YBCO high-temperature superconducting film layer. The filter circuit comprises a pair of symmetrically distributed differential input feed lines, a pair of differential output feed lines, two pairs of parallel coupling lines, a first branch line located at the junction of the differential input feed lines and the parallel coupling lines, a second branch line located at the symmetric plane of the two pairs of parallel coupling lines, a third branch line located at the junction of the differential output feed lines and the parallel coupling lines, a transverse transmission line connecting the first branch line and the second branch line and a pair of symmetric open-circuit transmission lines located at the center of the third branch line. The horizontal direction of the application is distributed with two paths composed of input feed lines, a pair of cascaded parallel coupling lines and output feed lines. Under the differential mode excitation, the whole circuit shows the band-pass characteristic, and under the common mode excitation, the whole circuit shows the full-band stop-band characteristic.

Description

Technical Field

[0001] This invention relates to the field of radio astronomy technology, specifically to a high-temperature superconducting equiripple broadband balanced bandpass filter. Background Technology

[0002] With the rapid development of wireless communication systems and the gradual reduction of available spectrum resources, the demand for microstrip filters is shifting towards high selectivity, low noise, and low loss. High-temperature superconducting technology, a rapidly developing high-tech technology in recent years, has been widely used in the fabrication of microwave filters since its discovery. Because microwave filters use distributed parameter components, when the frequency exceeds a certain value, the reactance and susceptance of the components will transform into each other; inductance becomes capacitance, and capacitance becomes inductance, resulting in a new passband in the stopband, known as the parasitic passband. Filters using high-temperature superconducting technology possess extremely low insertion loss and extremely high frequency interference suppression capabilities, thus showing broad development prospects in the field of high-sensitivity radio astronomy.

[0003] In the design of traditional high-temperature superconducting high-order filters, it is usually necessary to use three-dimensional electromagnetic simulation tools to tune the circuit topology parameters over a long period of time to achieve a basic performance match. However, the structural optimization of the filter topology circuit is highly dependent on the designer's experience. In particular, as the filter order increases, the circuit topology becomes more and more complex, and the effort and time spent on traditional electromagnetic simulation optimization become increasingly longer, resulting in low design efficiency and difficulty in ensuring accuracy. Summary of the Invention

[0004] To address the aforementioned issues, this invention employs a comprehensive design method to design a high-temperature superconducting equiripple broadband balanced bandpass filter. An ideal Chebyshev response transfer function is selected as the objective function. By calculating the filtering function of the bandpass filter and performing a mean square error analysis between it and the ideal Chebyshev objective function, the electrical parameters of each component in the required filter are optimized, thereby shortening the design cycle.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A high-temperature superconducting equiripple broadband balanced bandpass filter includes: a dielectric substrate, a yttrium barium copper oxide high-temperature superconducting thin film ground plane printed on the lower surface of the dielectric substrate, a yttrium barium copper oxide high-temperature superconducting thin film layer printed on the upper surface of the dielectric substrate, and a filter circuit on the yttrium barium copper oxide high-temperature superconducting thin film layer.

[0007] The filter circuit has a symmetrical structure, specifically including a first input feed line, a second input feed line, a first output feed line, a second output feed line, a first parallel coupling line, a second parallel coupling line, a third parallel coupling line, a fourth parallel coupling line, a first branch line, a second branch line, a third branch line, a transverse transmission line, a first open-circuit transmission line, and a second open-circuit transmission line. The first and second parallel coupling lines are cascaded, with the left side of the first parallel coupling line connected to the first input feed line and the right side of the second parallel coupling line connected to the first output feed line. The third and fourth parallel coupling lines are cascaded, with the left side of the third parallel coupling line connected to the second input feed line and the right side of the fourth parallel coupling line connected to the second output feed line. The first branch line connects the intersection of the first input feed line and the first parallel coupling line, and the intersection of the second input feed line and the third parallel coupling line. The third branch line connects the intersection of the first output feed line and the second parallel coupling line, and the intersection of the second output feed line and the fourth parallel coupling line. The second branch line connects the intersection of the first and second parallel coupling lines, and the intersection of the third and fourth parallel coupling lines. A horizontal transmission line connects the center of the first branch line to the center of the second branch line. The first open-circuit transmission line and the second open-circuit transmission line are connected symmetrically on both sides of the center of the third branch line.

[0008] Furthermore, the first parallel coupling line has the same structural parameters as the second parallel coupling line, and the third and fourth parallel coupling lines, which are symmetrical about the central symmetry plane AA', have the same structural parameters as the first and second parallel coupling lines, respectively.

[0009] Furthermore, the structural parameters of the first input feeder and the second input feeder are the same, and the structural parameters of the first output feeder and the second output feeder are the same.

[0010] Furthermore, the structural parameters of the first branch line and the third branch line are identical. Also, the structural parameters of the first open-circuit transmission lines on both sides of the center of the third branch line are identical to those of the second open-circuit transmission line.

[0011] Furthermore, the first parallel coupling line, the second parallel coupling line, the third parallel coupling line, the fourth parallel coupling line, the first branch line, the third branch line, the first open-circuit transmission line, and the second open-circuit transmission line are all bent, with the first open-circuit transmission line and the second open-circuit transmission line being T-shaped bends.

[0012] Furthermore, the horizontal transmission line, the second branch line, the first open-circuit transmission line, and the second open-circuit transmission line are connected at their joints using a transition structure.

[0013] In the high-temperature superconducting equal-ripple broadband balanced bandpass filter, when differential-mode excitation is applied to the input and output ports, the central symmetry plane AA' is equivalent to an ideal electric wall, and the transverse transmission line and open-circuit transmission line are equivalent to a short circuit; when common-mode excitation is applied to the input and output ports, the central symmetry plane AA' is equivalent to an ideal magnetic wall, and the transverse transmission line and open-circuit transmission line are equivalent to an open circuit.

[0014] Furthermore, under differential-mode excitation, the equivalent circuit exhibits bandpass characteristics, while under common-mode excitation, with the action of transverse transmission lines and parallel open-circuit transmission lines, the equivalent circuit exhibits full-band stopband characteristics.

[0015] Preferably, the dielectric substrate is a magnesium oxide dielectric substrate, with a yttrium barium copper oxide high-temperature superconducting thin film ground plane on the lower surface and a yttrium barium copper oxide high-temperature superconducting thin film layer on the upper surface.

[0016] Preferably, the filter circuit has a planar structure and is closely attached to the dielectric substrate. The input and output feed line impedances of the planar filter circuit are 50Ω.

[0017] Preferably, the connection portion of the transverse transmission line, the connection portion of the second branch line, and the connection portion of the open-circuit transmission line adopt a transition structure.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. The differential mode passband provided by this invention has multiple poles, achieving equal ripple attenuation characteristics, and through a comprehensive design method, the required filter can be quickly designed according to different performance requirements.

[0020] 2. The common-mode suppression provided by this invention is full-band suppression, which has excellent noise suppression performance. Attached Figure Description

[0021] Figure 1 This is a topology diagram of the high-temperature superconducting equiripple broadband balanced bandpass filter proposed in this invention;

[0022] Figure 2 This is a three-dimensional topology diagram of the high-temperature superconducting equiripple broadband balanced bandpass filter proposed in this invention;

[0023] Figure 3 This is the transmission line model of the high-temperature superconducting equiripple broadband balanced bandpass filter proposed in this invention;

[0024] Figure 4 This invention provides the differential-mode equivalent circuit of the high-temperature superconducting equiripple broadband balanced bandpass filter.

[0025] Figure 5 This invention provides the common-mode equivalent circuit of the high-temperature superconducting equiripple broadband balanced bandpass filter.

[0026] Figure 6 This is a topology diagram of the high-temperature superconducting equiripple broadband balanced bandpass filter proposed in this invention;

[0027] Figure 7 The results are the synthesis and simulation of the high-temperature superconducting equiripple broadband balanced bandpass filter proposed in this invention.

[0028] Reference numerals: 1. First input feed line; 2. First output feed line; 3. Second input feed line; 4. Second output feed line; 5. First parallel coupling line; 6. Third parallel coupling line; 7. Second parallel coupling line; 8. Fourth parallel coupling line; 9. First branch line; 10. Second branch line; 11. Third branch line; 12. Lateral transmission line; 13. First open-circuit transmission line; 14. Second open-circuit transmission line; 15. Dielectric substrate; 16. Yttrium barium copper oxide high-temperature superconducting thin film layer; 17. Filter circuit; 18. Yttrium barium copper oxide high-temperature superconducting thin film ground plane. Detailed Implementation

[0029] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the invention. The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] like Figure 1 and Figure 2 As shown, a high-temperature superconducting equiripple broadband balanced bandpass filter includes a dielectric substrate 15, a yttrium barium copper oxide high-temperature superconducting thin film ground plane 18 located on the lower surface of the dielectric substrate 15, a yttrium barium copper oxide high-temperature superconducting thin film layer 16 located on the upper surface of the dielectric substrate 15, and a filter circuit 17 constructed on the yttrium barium copper oxide high-temperature superconducting thin film layer 16. The filter circuit 17 includes a first input feed line 1, a second input feed line 3, a first output feed line 2, a second output feed line 4, a first parallel coupling line 5, a second parallel coupling line 7, a third parallel coupling line 6, a fourth parallel coupling line 8, a first branch line 9, a second branch line 10, a third branch line 11, a lateral transmission line 12, a first open-circuit transmission line 13, and a second open-circuit transmission line 14.

[0031] The first parallel coupling line 5 and the second parallel coupling line 7 are cascaded, wherein the left side of the first parallel coupling line 5 is connected to the first input feed line 1, and the right side of the second parallel coupling line 7 is connected to the first output feed line 2;

[0032] The third parallel coupling line 6 and the fourth parallel coupling line 8 are cascaded, wherein the third parallel coupling line 6 is connected to the second input feed line 3 on the left and the fourth parallel coupling line 8 is connected to the second output feed line 4 on the right.

[0033] The first branch line 9 connects the junction of the first input feed line 1 and the first parallel coupling line 5 and the junction of the second input feed line 3 and the third parallel coupling line 6; the third branch line 11 connects the junction of the first output feed line 2 and the second parallel coupling line 7 and the junction of the second output feed line 4 and the fourth parallel coupling line 8.

[0034] The second branch line 10 connects the intersection of the first parallel coupling line 5 and the second parallel coupling line 7, and the intersection of the third parallel coupling line 6 and the fourth parallel coupling line 8;

[0035] The transverse transmission line 12 connects the center of the first branch line 9 and the center of the second branch line 10, and is located between the first branch line 9 and the second branch line 10;

[0036] The first open-circuit transmission line 13 and the second open-circuit transmission line 14 are symmetrically connected on both sides of the center of the third branch line 11.

[0037] The high-temperature superconducting equiripple broadband balanced bandpass filter is symmetrical about the central horizontal plane AA'. The first input feed line 1, the first parallel coupling line 5, the second parallel coupling line 7, and the first output feed line 2 have the same structural parameters as the second input feed line 3, the third parallel coupling line 6, the fourth parallel coupling line 8, and the second output feed line 4, which are symmetrical about the central symmetry plane AA'. Among them, the first parallel coupling line 5 has the same structural parameters as the second parallel coupling line 7, and the third parallel coupling line 6 has the same structural parameters as the fourth parallel coupling line 8.

[0038] The first branch line 9 and the third branch line 11 have the same structural parameters; the first open-circuit transmission line 13 and the second open-circuit transmission line 14 have the same structural parameters.

[0039] The first parallel coupling line 5, the second parallel coupling line 7, the third parallel coupling line 6, the fourth parallel coupling line 8, the first branch line 9, the third branch line 11, the first open-circuit transmission line 13, and the second open-circuit transmission line 14 are all bent; among them, the first open-circuit transmission line 13 and the second open-circuit transmission line 14 are T-shaped bends.

[0040] The electrical lengths of the first parallel coupling line 5, the second parallel coupling line 7, the third parallel coupling line 6, the fourth parallel coupling line 8, the transverse transmission line 12, the first open-circuit transmission line 13, and the second open-circuit transmission line 14 are quarter wavelengths; the electrical lengths of the first branch line 9, the second branch line 10, and the third branch line 11 are half wavelengths.

[0041] The connection between the transverse transmission line 12, the second branch line 10, the first open-circuit transmission line 13, and the second open-circuit transmission line 14 is made using a transition structure.

[0042] Figure 3This is the transmission line model of the high-temperature superconducting equiripple broadband balanced bandpass filter proposed in this invention. It includes the input and output feed lines (Z = 50Ω, θ), and the first and second pairs of parallel coupling lines (Z...). 0e1 Z 0o1 ,θ), the first and third pairs of branch lines (Z b1 ,θ), the second pair of branch lines (Z) b2 ,θ), a transverse transmission line (Z) c1 ,θ) and an open-circuit transmission line (Z) c2 Composed of θ). When differential-mode excitation is applied to the input and output ports, the horizontal symmetry plane SS' will become a perfect electric wall, at which point the transverse transmission line and the open-circuit transmission line shown in the figure will be short-circuited. Its equivalent circuit diagram is as follows. Figure 4 As shown, it exhibits bandpass characteristics. When common-mode excitation is applied to the input and output ports, the horizontal symmetry plane SS' becomes a perfect magnetic wall. In this case, the transverse transmission line shown in the figure and the two connected branches form a severe signal path, while the open-circuit transmission line is equivalent to being cascaded at the end of the connected branches with doubled impedance. Its equivalent circuit diagram is shown below. Figure 5 As shown, the signal exhibits full-band stopband characteristics. At the center frequency of the differential mode passband, the electrical length θ of all transmission lines in the figure is equal to one-quarter wavelength.

[0043] To achieve the characteristics of an equiripple filter, this invention selects an ideal Chebyshev response transfer function as the objective function. By ensuring that the filtering function of the bandpass filter and the ideal Chebyshev objective function have the same response, the characteristic impedance values ​​of each transmission line required in the bandpass filter can be calculated. In this example, the design parameter is: Z 0e1 =136.52Ω, Z 0o1 = 44.51Ω, Z b1 =70.16Ω, Z b2 =26.95Ω, Z c1 =20.15Ω, Z c2 =9.6Ω.

[0044] Figure 6 The layout of the high-temperature superconducting equiripple broadband balanced bandpass filter proposed in this invention is shown, along with the final physical dimensions. All dimensions in the figure are in millimeters (mm).

[0045] The high-temperature superconducting equal-ripple broadband balanced bandpass filter proposed in this invention comprises a dielectric substrate, a high-temperature superconducting thin film layer printed on the surface of the dielectric substrate, and a filter circuit constructed on the high-temperature superconducting thin film layer. In this example, the dielectric substrate uses magnesium oxide material, and the high-temperature superconducting thin film material is yttrium barium copper oxide, with a relative permittivity ε. r =9.78, the dielectric substrate thickness is 0.5mm. The upper layer of the dielectric substrate is tightly bonded to the filter circuit.

[0046] Figure 7 This paper compares the synthesis and simulation results of the high-temperature superconducting equiripple broadband balanced bandpass filter proposed in this invention. The results show that the simulated differential mode center frequency is 4 GHz, the differential mode relative bandwidth is 116%, the return loss in the differential mode passband is less than -26.3 dB, the minimum differential mode suppression is 10 dB, and it can be observed that the common mode is effectively suppressed throughout the entire frequency band.

[0047] The above examples are merely illustrative of the invention to illustrate its superior effects and are not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the spirit and principles of this invention should be included within the scope of protection of the claims of this invention.

Claims

1. A high-temperature superconducting equal-ripple broadband balanced bandpass filter, characterized in that: The device includes a dielectric substrate (15), a yttrium barium copper oxide high-temperature superconducting thin film ground plane (18) located on the lower surface of the dielectric substrate (15), a yttrium barium copper oxide high-temperature superconducting thin film layer (16) located on the upper surface of the dielectric substrate (15), and a filter circuit (17) constructed on the yttrium barium copper oxide high-temperature superconducting thin film layer (16). The filter circuit (17) includes a first input feed line (1), a second input feed line (3), a first output feed line (2), a second output feed line (4), a first parallel coupling line (5), a second parallel coupling line (7), a third parallel coupling line (6), a fourth parallel coupling line (8), a first branch line (9), a second branch line (10), a third branch line (11), a lateral transmission line (12), a first open-circuit transmission line (13), and a second open-circuit transmission line (14). The first parallel coupling line (5) is cascaded with the second parallel coupling line (7), wherein the first parallel coupling line (5) is connected to the first input feed line (1) on the left and the second parallel coupling line (7) is connected to the first output feed line (2) on the right. The third parallel coupling line (6) is cascaded with the fourth parallel coupling line (8), wherein the third parallel coupling line (6) is connected to the second input feed line (3) on the left and the fourth parallel coupling line (8) is connected to the second output feed line (4) on the right. The first branch line (9) connects the intersection of the first input feed line (1) and the first parallel coupling line (5) and the intersection of the second input feed line (3) and the third parallel coupling line (6); the third branch line (11) connects the intersection of the first output feed line (2) and the second parallel coupling line (7) and the intersection of the second output feed line (4) and the fourth parallel coupling line (8); The second branch line (10) connects the intersection of the first parallel coupling line (5) and the second parallel coupling line (7) and the intersection of the third parallel coupling line (6) and the fourth parallel coupling line (8); The transverse transmission line (12) connects the center of the first branch line (9) and the center of the second branch line (10), and is located between the first branch line (9) and the second branch line (10); The first open-circuit transmission line (13) and the second open-circuit transmission line (14) are symmetrically connected on both sides of the center of the third branch line (11).

2. The high-temperature superconducting equal-ripple broadband balanced bandpass filter according to claim 1, characterized in that: The filter circuit (17) has a symmetrical structure. The first input feed line (1), the first parallel coupling line (5), the second parallel coupling line (7), and the first output feed line (2) have the same structural parameters as the second input feed line (3), the third parallel coupling line (6), the fourth parallel coupling line (8), and the second output feed line (4), respectively. Among them, the first parallel coupling line (5) has the same structural parameters as the second parallel coupling line (7), and the third parallel coupling line (6) has the same structural parameters as the fourth parallel coupling line (8).

3. The high-temperature superconducting equiripple broadband balanced bandpass filter according to claim 1, characterized in that: The first branch line (9) and the third branch line (11) have the same structural parameters; the first open-circuit transmission line (13) and the second open-circuit transmission line (14) have the same structural parameters.

4. The high-temperature superconducting equiripple broadband balanced bandpass filter according to claim 1, characterized in that: The first parallel coupling line (5), the second parallel coupling line (7), the third parallel coupling line (6), the fourth parallel coupling line (8), the first branch line (9), the third branch line (11), the first open-circuit transmission line (13), and the second open-circuit transmission line (14) are all bent; among them, the first open-circuit transmission line (13) and the second open-circuit transmission line (14) are T-shaped bend structures.

5. A high-temperature superconducting equiripple broadband balanced bandpass filter according to claim 1, characterized in that: The electrical lengths of the first parallel coupling line (5), the second parallel coupling line (7), the third parallel coupling line (6), the fourth parallel coupling line (8), the transverse transmission line (12), the first open-circuit transmission line (13), and the second open-circuit transmission line (14) are quarter wavelengths; the electrical lengths of the first branch line (9), the second branch line (10), and the third branch line (11) are half wavelengths.

6. A high-temperature superconducting equiripple broadband balanced bandpass filter according to claim 1, characterized in that: The connection between the transverse transmission line (12), the second branch line (10), the first open-circuit transmission line (13), and the second open-circuit transmission line (14) is made using a transition structure.

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