A long-delay low-loss wideband delay line of defectively open stub-coupled strips

Abstract

The application relates to a long-delay low-loss wideband delay line of a lack of ground open-circuit branch coupling strip, and belongs to the field of microwave systems. The long-delay low-loss wideband delay line comprises a metal microstrip line layer, a dielectric layer and a metal ground layer which are sequentially connected from top to bottom; the metal microstrip line layer comprises a fork structure composed of a U-shaped main microstrip line, a first U-shaped open-circuit branch and a second U-shaped open-circuit branch; a coupling strip is added in the fork structure, the coupling strip is grounded through a metallized via, and a complementary defect ground of the open-circuit branch is designed at a non-coplanar metal ground. Two or more long-delay low-loss wideband delay lines are connected in series to form a cascade delay line. The application works in a sub-6 frequency band range, has a relative bandwidth of 31.6%, a maximum delay time of 1.3 ns and an average transmission loss of 0.5 dB; a cascade delay line formed by connecting four long-delay low-loss wideband delay lines in series has a maximum delay time of 7.4 ns and an average transmission loss of less than 2.6 dB. The application effectively solves the mutual coupling eddy current effect between adjacent transmission lines.

Description

Technical Field

[0001] This invention belongs to the field of microwave systems, and specifically relates to a long-delay, low-loss broadband delay line with a defective open-circuit stub coupling strip. Background Technology

[0002] With the rapid development of 5G communication, multi-target detection, and synthetic aperture microwave imaging, phased array technology has been widely used in 5G base stations, MIMO radar, and large-scale active arrays. As one of the core components of phased array radar, the delay line directly determines the performance of the antenna beam. Due to the large number of channels in active array antennas, the delay line occupies a large circuit area, which is detrimental to circuit miniaturization and weight reduction. This contradiction is even more pronounced in the low-frequency microwave band. Therefore, developing broadband, long-delay, and low-loss microwave delay lines is more important and urgent in the low-frequency microwave band.

[0003] Existing delay line structures commonly include four types: coaxial cable delay lines, surface acoustic wave (SAW) delay lines, superconducting delay lines, and microstrip delay lines. Coaxial cable delay lines are relatively large and heavy, hindering system miniaturization and integration, and their relatively high losses lead to signal attenuation. SAW delay lines have a relatively narrow operating frequency range and limited delay time adjustment. Superconducting delay lines operate under harsh conditions, increasing system complexity and cost, and making fabrication and processing difficult. Existing microstrip delay lines use folded microstrip lines and complementary slot lines to extend the delay time; however, the truncation and proximity effects are not well addressed. The proximity coupling eddy current effect between adjacent transmission lines is not effectively resolved. This proximity coupling eddy current effect not only fails to increase the transmission line delay time but also increases the RF equivalent resistance of the transmission line, resulting in greater transmission loss. Summary of the Invention

[0004] To improve the delay time of low-frequency planar microwave circuits, this invention provides a long-delay, low-loss broadband delay line with a defect-ground open-stub coupled strip.

[0005] A long-delay, low-loss broadband delay line with a defective open-circuit stub coupling strip is a microstrip planar structure, comprising a metal microstrip line layer 1, a dielectric layer 2, and a metal ground layer 3 connected sequentially from top to bottom.

[0006] The metal microstrip layer 1 includes a U-shaped main microstrip line, one side of which is a first microstrip line 16 and the other side is a second microstrip line 17. The corresponding ends of the first microstrip line 16 and the second microstrip line 17 are connected by a transition microstrip line 18.

[0007] A first U-shaped open-circuit stub is symmetrically provided on the first microstrip line 16 adjacent to the transition microstrip line 18, and the opening end of the first U-shaped open-circuit stub is in the same direction as the opening end of the U-shaped main microstrip line.

[0008] A second U-shaped open stub is symmetrically provided on the second microstrip line 17 adjacent to the open end of the U-shaped main microstrip line, and the open end of the first U-shaped open stub corresponds to the transition microstrip line 18 of the U-shaped main microstrip line.

[0009] The U-shaped main microstrip line, the first U-shaped open-circuit stub, and the second U-shaped open-circuit stub constitute an interdigitated structure;

[0010] A coupling strip 15 is provided between one side branch of the first U-shaped open branch and one side branch of the adjacent second U-shaped open branch, and the coupling strip 15 has two or more first metal through holes 19.

[0011] The dielectric layer 2 has two or more second metal through holes 21, and the two or more second metal through holes 21 are vertically connected to two or more first metal through holes 19.

[0012] The metal grounding layer 3 is provided with a first U-shaped defect ground 31 and a second U-shaped defect ground 32. The opening ends of the first U-shaped defect ground 31 and the opening ends of the second U-shaped defect ground 32 are opposite to each other. One side of the first U-shaped defect ground 31 and one side of the adjacent second U-shaped defect ground 32 are in a cross structure. Two or more third metal through holes 33 are opened between one side of the cross structure first U-shaped defect ground 31 and one side of the adjacent second U-shaped defect ground 32.

[0013] Two or more third metal through holes 33 are vertically connected to two or more second metal through holes 21 and two or more first metal through holes 19;

[0014] The end of the first microstrip line 16 is the output terminal of a long-delay, low-loss broadband delay line, and the end of the second microstrip line 17 is the input terminal of a long-delay, low-loss broadband delay line.

[0015] The long-delay, low-loss broadband delay line operates in the sub-6 frequency band, with a relative bandwidth of 31.6%, a maximum delay time of 1.3ns, and an average transmission loss of 0.5dB.

[0016] Further technical solutions are as follows:

[0017] The first U-shaped open-circuit stub is composed of a pair of L-shaped microstrips, namely the first open-circuit stub 11 and the second open-circuit stub 12; the short side ends of the first open-circuit stub 11 and the second open-circuit stub 12 are respectively fixedly connected to the first microstrip line 16, and the first open-circuit stub 11 is located outside the first microstrip line 16, and the second open-circuit stub 12 is located between the first microstrip line 16 and the second microstrip line 17.

[0018] The second U-shaped open branch is also composed of a pair of L-shaped microstrips, namely the third open branch 13 and the fourth open branch 14; the short side ends of the third open branch 13 and the fourth open branch 14 are respectively fixedly connected to the first microstrip line 16. The third open branch 13 is located between the first microstrip line 16 and the second open branch 12, and the fourth open branch 14 is located outside the second open branch 12.

[0019] The second open branch 12 and the third open branch 13 are adjacent to each other, and the coupling strip 15 is located between the second open branch 12 and the third open branch 13.

[0020] The materials of the metal microstrip layer 1 and the metal ground layer 3 are copper; the material of the dielectric layer 2 is a microwave dielectric substrate with a dielectric constant of 3.4-3.7 and a thickness of 0.0035λ-0.0065λ, where λ is the wavelength corresponding to the antenna operating frequency band.

[0021] The first microstrip line 16 and the second microstrip line 17 have the same dimensions, with a width of 1.6-2 mm and a length of 0.15λ-0.3λ, where λ is the wavelength corresponding to the antenna's operating frequency band; the spacing between the first microstrip line 16 and the second microstrip line 17 is 3-5 mm.

[0022] The first open-circuit stub 11, the second open-circuit stub 12, the third open-circuit stub 13, and the fourth open-circuit stub 14 have the same structural dimensions; the length of the first open-circuit stub 11 is 0.1λ-0.2λ and the width is 0.1-0.5mm; the distance between the second open-circuit stub 12 and the third open-circuit stub 13, which form an interdigitated structure, is 1.5-2mm, where λ is the wavelength corresponding to the antenna's operating frequency band.

[0023] The coupling strip 15 is spaced equally between itself and the second open stub 12 and the third open stub 13, with a spacing of 0.7-1.0 mm. The coupling strip 15 has a length of 0.05λ-0.08λ and a width of 0.3-0.7 mm, where λ is the wavelength corresponding to the antenna's operating frequency band.

[0024] The distance between one side of the first U-shaped defect ground 31 with the cross structure and one side of the adjacent second U-shaped defect ground 32 is 0.05λ-0.15λ, where λ is the wavelength corresponding to the antenna operating frequency band.

[0025] The first U-shaped defect ground 31 and the second U-shaped defect ground 32 have the same dimensions, with a length of 0.15λ-0.4λ and a width of 0.1-0.5mm, where λ is the wavelength corresponding to the antenna's operating frequency band.

[0026] The two or more long-delay, low-loss broadband delay lines are connected in series through a cascaded transition microstrip line 4 to form a cascaded delay line. The maximum delay time of the cascaded two or more long-delay, low-loss broadband delay lines is 7.4 ns, and the average transmission loss is less than 2.6 dB.

[0027] The cascaded transition microstrip line 4 has a width of 0.5-1.0 mm and a length of 5.5-9.5 mm; both ends of the cascaded transition microstrip line 4 are provided with 45° chamfers.

[0028] Compared with the prior art, the beneficial technical effects of the present invention are reflected in the following aspects:

[0029] 1. The long-delay, low-loss broadband delay line of this invention effectively solves the mutual coupling eddy current effect between adjacent transmission lines by leading out U-shaped open-circuit stubs with a central mirror-symmetric structure from the main transmission line, then adding coupling strips to the interdigital structure and grounding the coupling strips through metallized vias, and designing complementary defect grounds for the open-circuit stubs at the non-coplanar metal grounding points. This extends the delay time per unit area, reduces transmission loss, expands bandwidth, and enables circuit miniaturization. The unit delay line structure proposed in this invention has a maximum delay time of 1.3 ns and an average transmission loss of 0.5 dB. Furthermore, the unit delay line also has good cascading properties; the cascaded delay line structure has a maximum delay time of 7.4 ns, an average transmission loss of less than 2.6 dB, and a relative bandwidth of 31.6%.

[0030] 2. The present invention leads out a first open-circuit stub 11, a second open-circuit stub 12, a third open-circuit stub 13, and a fourth open-circuit stub 14 from the first microstrip line 16 and the second microstrip line 17, respectively, and adds a coupling strip 15 between the second open-circuit stub 12 and the third open-circuit stub 13. This combined structure enhances the slow wave transmission effect of the delay line, reduces the coupling eddy current effect, thereby effectively extending the delay time, achieving impedance matching, and reducing insertion loss.

[0031] 3. By designing metallized through-holes to connect the coupling strip 15 to the metal ground layer 3, the present invention can introduce more equivalent capacitance into the circuit, enhance the electromagnetic shielding effect of the microstrip line, make the electromagnetic energy distribution more uniform, and improve the stability and reliability of the circuit.

[0032] 4. The present invention designs a first U-shaped defect ground 31 and a second U-shaped defect ground 32 on the metal grounding layer 3 to form a complementary relationship with the first open-circuit branch 11, the second open-circuit branch 12, the third open-circuit branch 13, and the fourth open-circuit branch 14, thereby effectively improving the impedance matching of the circuit, introducing new frequency points to expand the bandwidth, and achieving a more compact circuit layout.

[0033] 5. The long-delay, low-loss broadband delay line with defective open-circuit stub coupling strip proposed in this invention can be applied to the radio frequency front-end link system. By using the idea of ​​time for space, it can cleverly convert various functional circuits of the radio frequency front-end, thereby flexibly adjusting the working state of the radio frequency link in the microwave imaging radar system.

[0034] 6. The long-delay, low-loss broadband delay line structure with defective open-circuit stub coupling strip proposed in this invention is miniaturized, easy to integrate, low in manufacturing cost, and has a high yield rate. It plays an important role in the stability and reliability of signals in microwave imaging radar systems and can be widely used. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the three-dimensional structure of the unit delay line of the present invention.

[0036] Figure 2 This is a schematic diagram of the top layer microstrip line structure of the unit delay line.

[0037] Figure 3 This is a schematic diagram of a unit dielectric layer structure.

[0038] Figure 4 This is a schematic diagram of the underlying defect structure of the unit delay line.

[0039] Figure 5 This is a schematic diagram of the three-dimensional structure of the cascaded delay line of the present invention.

[0040] Figure 6 The simulation results are shown for the input port reflection coefficient, output port reflection coefficient, input-to-output port insertion loss, and delay time of the unit delay line.

[0041] Figure 7 The simulation results are shown for the input port reflection coefficient, the total output port reflection coefficient, the input-to-output port insertion loss, and the delay time of the cascaded delay line.

[0042] Figure 1-5 In the middle, the following are the microstrip line layers: 1. Metallic microstrip line layer; 2. Dielectric layer; 3. Metallic ground layer; 11. First open-circuit stub; 12. Second open-circuit stub; 13. Third open-circuit stub; 14. Fourth open-circuit stub; 15. Coupling strip; 16. First microstrip line; 17. Second microstrip line; 18. Transition microstrip line; 19. First metallic via; 21. Second metallic via; 31. First U-shaped defect ground; 32. Second U-shaped defect ground; 33. Third metallic via; 4. Cascaded transition microstrip line; 10. Input port; 100. Output port; 101. Detailed Implementation

[0043] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. Example 1

[0044] See Figure 1 A long-delay, low-loss broadband delay line with defective open-circuit stub coupling strip is a microstrip planar structure, comprising a metal microstrip line layer 1, a dielectric layer 2, and a metal ground layer 3 connected sequentially from top to bottom.

[0045] Both the metal microstrip layer 1 and the metal ground layer 3 are made of copper. The dielectric layer 2 is made of Rogers 4003 with a dielectric constant of 3.55 and a thickness of 0.0045λ. The long-delay, low-loss broadband delay line of this embodiment 1 can be used as a unit delay line, with overall dimensions of 0.813 mm thickness, 34.2 mm length, and 16 mm width.

[0046] See Figure 2 The metal microstrip layer 1 includes a U-shaped main microstrip line, one side of which is a first microstrip line 16 and the other side is a second microstrip line 17. The corresponding ends of the first microstrip line 16 and the second microstrip line 17 are connected by a transition microstrip line 18.

[0047] The first microstrip line 16 and the second microstrip line 17 have the same dimensions, with a width of 1.7 mm and a length of 0.216λ, where λ is the wavelength corresponding to the antenna's operating frequency band; the distance between them is 4 mm. The transition microstrip line 18 has a 1.8 mm 45° chamfer at both ends, with a width of 0.7 mm and a length of 7.6 mm, effectively reducing signal reflection, lowering losses, and expanding bandwidth.

[0048] A first U-shaped open-circuit stub is symmetrically provided on the first microstrip line 16 adjacent to the transition microstrip line 18, and the opening end of the first U-shaped open-circuit stub is in the same direction as the opening end of the U-shaped main microstrip line.

[0049] The first U-shaped open-circuit stub is composed of a pair of L-shaped microstrips, namely the first open-circuit stub 11 and the second open-circuit stub 12. The short side ends of the first open-circuit stub 11 and the second open-circuit stub 12 are respectively fixedly connected to the first microstrip line 16, and the first open-circuit stub 11 is located outside the first microstrip line 16, while the second open-circuit stub 12 is located between the first microstrip line 16 and the second microstrip line 17.

[0050] A second U-shaped open stub is symmetrically provided on the second microstrip line 17 adjacent to the open end of the U-shaped main microstrip line, and the open end of the first U-shaped open stub corresponds to the transition microstrip line 18 of the U-shaped main microstrip line.

[0051] The second U-shaped open-circuit stub is also composed of a pair of L-shaped microstrips, namely the third open-circuit stub 13 and the fourth open-circuit stub 14; the short side ends of the third open-circuit stub 13 and the fourth open-circuit stub 14 are respectively fixedly connected to the first microstrip line 16. The third open-circuit stub 13 is located between the first microstrip line 16 and the second open-circuit stub 12, and the fourth open-circuit stub 14 is located outside the second open-circuit stub 12.

[0052] The second open branch 12 and the third open branch 13 are adjacent to each other, and the coupling strip 15 is located between the second open branch 12 and the third open branch 13.

[0053] The U-shaped main microstrip line, the first U-shaped open-circuit stub, and the second U-shaped open-circuit stub constitute an interdigitated structure.

[0054] The first open branch 11, the second open branch 12, the third open branch 13, and the fourth open branch 14 have the same structural dimensions; the length of the first open branch 11 is 0.135λ and the width is 0.3mm; the distance between the second open branch 12 and the third open branch 13, which form an interdigitated structure, is 1.7mm.

[0055] A coupling strip 15 is provided between the second open-circuit branch 12 and the third open-circuit branch 13, and five first metal through holes 19 are provided on the coupling strip 15. The coupling strip 15 has a length of 0.0625λ and a width of 0.5mm.

[0056] See Figure 3 The dielectric layer 2 has five second metal through holes 21, and the five second metal through holes 21 are vertically connected to the five first metal through holes 19.

[0057] See Figure 4 The metal grounding layer 3 is provided with a first U-shaped defect ground 31 and a second U-shaped defect ground 32. The opening ends of the first U-shaped defect ground 31 and the second U-shaped defect ground 32 are opposite to each other. One side of the first U-shaped defect ground 31 and one side of the adjacent second U-shaped defect ground 32 are in a cross structure. Five third metal through holes 33 are opened between one side of the cross structure first U-shaped defect ground 31 and one side of the adjacent second U-shaped defect ground 32.

[0058] The distance between one side of the first U-shaped defect 31 and the adjacent second U-shaped defect 32 is 1.7 mm; the first U-shaped defect 31 and the second U-shaped defect 32 have the same dimensions, with a length of 0.27λ and a width of 0.2 mm.

[0059] Five third metal vias 33 are vertically connected to five second metal vias 21 and five first metal vias 19, with the same diameter of 0.4 mm. The spacing between adjacent vias is the same, 2 mm. This connects the metal microstrip layer 1 and the metal ground layer 3.

[0060] By adopting a combination structure of open stubs and coupled strips, the mutual coupling eddy current effect between adjacent transmission circuits is significantly reduced, the insertion loss is decreased, and the delay time per unit area is extended.

[0061] See Figure 2 The end of the first microstrip line 16 is the output port 100 of the long delay low loss broadband delay line, and the end of the second microstrip line 17 is the input port 10 of the long delay low loss broadband delay line.

[0062] The long-delay, low-loss broadband delay line operates in the sub-6 frequency band, with a relative bandwidth of 31.6%, a maximum delay time of 1.3ns, and an average transmission loss of 0.5dB.

[0063] The long-delay, low-loss broadband delay line in this embodiment 1 operates in the sub-6 frequency band, and the wavelength λ corresponding to the operating frequency band in this embodiment 1 is 158mm.

[0064] Verification simulation was performed on the long-delay, low-loss broadband delay line of Example 1, see [link to simulation]. Figure 6 In the values ​​of a and b, the reflection coefficients of the input and output ports of the long-delay, low-loss broadband delay line are both less than -10dB in the frequency range of 1.6GHz-2.2GHz; see also... Figure 6 In the formula 'c', the insertion loss from the input port to the output port is an average of 0.5 dB in the frequency range of 1.6 GHz to 2.2 GHz; see [link to relevant documentation]. Figure 6 In the d, the maximum delay time can reach 1.3ns. Example 2

[0065] See Figure 5 Four long-delay, low-loss broadband delay lines of Embodiment 1 are connected in series via a cascaded transition microstrip line 4 to form a cascaded delay line. The cascaded transition microstrip line 4 has a width of 0.7 mm and a length of 7.6 mm. Both ends of the cascaded transition microstrip line 4 are chamfered at 45°. The overall dimensions of the cascaded structure of the long-delay, low-loss broadband delay line are: thickness 0.813 mm, length 55.73 mm, and width 37 mm. The maximum delay time of the cascaded delay line is 7.4 ns, and the average transmission loss is less than 2.6 dB.

[0066] Verification simulation was performed on the cascaded delay line of Example 2, see [link / reference]. Figure 7In the values ​​of a and b, the reflection coefficients of the input and total output ports of the cascaded delay line are both less than -10dB in the frequency range of 1.6GHz-2.2GHz; see also... Figure 7 In the figure, c indicates that the insertion loss from the input port to the output port is an average of 2.6 dB in the frequency range of 1.6 GHz to 2.2 GHz; see [link to relevant documentation]. Figure 7 The maximum delay time for d in the model is 7.4ns.

[0067] Those skilled in the art will readily understand that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A long-delay, low-loss broadband delay line with defectively open-circuit stub coupling stripe, characterized in that: The long-delay, low-loss broadband delay line is a microstrip planar structure, comprising a metal microstrip line layer (1), a dielectric layer (2), and a metal ground layer (3) connected sequentially from top to bottom. The metal microstrip layer (1) includes a U-shaped main microstrip line, one side of which is a first microstrip line (16) and the other side is a second microstrip line (17). The first microstrip line (16) and the second microstrip line (17) are connected by a transition microstrip line (18). A first U-shaped open stub is symmetrically provided on the first microstrip line (16) adjacent to the transition microstrip line (18), and the opening end of the first U-shaped open stub is in the same direction as the opening end of the U-shaped main microstrip line. The second microstrip line (17) adjacent to the open end of the U-shaped main microstrip line is symmetrically provided with a second U-shaped open stub, and the open end of the first U-shaped open stub corresponds to the transition microstrip line (18) of the U-shaped main microstrip line. The U-shaped main microstrip line, the first U-shaped open-circuit stub, and the second U-shaped open-circuit stub constitute an interdigitated structure; A coupling strip (15) is provided between one side branch of the first U-shaped open branch and one side branch of the adjacent second U-shaped open branch, and two or more first metal through holes (19) are provided on the coupling strip (15). The dielectric layer (2) has two or more second metal through holes (21), and the two or more second metal through holes (21) are vertically connected to the two or more first metal through holes (19); The metal grounding layer (3) is provided with a first U-shaped defect ground (31) and a second U-shaped defect ground (32). The opening ends of the first U-shaped defect ground (31) and the second U-shaped defect ground (32) are opposite to each other. One side of the first U-shaped defect ground (31) and one side of the adjacent second U-shaped defect ground (32) are in a cross structure. Two or more third metal through holes (33) are opened between one side of the cross structure first U-shaped defect ground (31) and one side of the adjacent second U-shaped defect ground (32). Two or more third metal through holes (33) are connected vertically to two or more second metal through holes (21) and two or more first metal through holes (19); The end of the first microstrip line (16) is the output end of a long-delay, low-loss broadband delay line, and the end of the second microstrip line (17) is the input end of a long-delay, low-loss broadband delay line. The long-delay, low-loss broadband delay line operates in the sub-6 frequency band, with a relative bandwidth of 31.6%, a maximum delay time of 1.3ns, and an average transmission loss of 0.5dB.

2. The long-delay, low-loss broadband delay line with defective open-circuit stub coupling strip as described in claim 1, characterized in that: The first U-shaped open-circuit stub is composed of a pair of L-shaped microstrips, namely the first open-circuit stub (11) and the second open-circuit stub (12); the short side ends of the first open-circuit stub (11) and the second open-circuit stub (12) are respectively fixedly connected to the first microstrip line (16), and the first open-circuit stub (11) is located outside the first microstrip line (16), and the second open-circuit stub (12) is located between the first microstrip line (16) and the second microstrip line (17); The second U-shaped open-circuit stub is also composed of a pair of L-shaped microstrips, namely the third open-circuit stub (13) and the fourth open-circuit stub (14); the short side ends of the third open-circuit stub (13) and the fourth open-circuit stub (14) are respectively fixedly connected to the first microstrip line (16). The third open-circuit stub (13) is located between the first microstrip line (16) and the second open-circuit stub (12), and the fourth open-circuit stub (14) is located outside the second open-circuit stub (12). The second open branch (12) and the third open branch (13) are adjacent to each other, and the coupling strip (15) is located between the second open branch (12) and the third open branch (13).

3. The long-delay, low-loss broadband delay line with defective open-circuit stub coupling strip as described in claim 1, characterized in that: The metal microstrip layer (1) and the metal ground layer (3) are made of copper; the dielectric layer (2) is made of microwave dielectric substrate with a dielectric constant of 3.4-3.7 and a thickness of 0.0035λ-0.0065λ, where λ is the wavelength corresponding to the antenna operating frequency band.

4. The long-delay, low-loss broadband delay line with defective open-circuit stub coupling strip as described in claim 1, characterized in that: The first microstrip line (16) and the second microstrip line (17) have the same dimensions, with a width of 1.6-2 mm and a length of 0.15λ-0.3λ, where λ is the wavelength corresponding to the antenna operating frequency band; the spacing between the first microstrip line (16) and the second microstrip line (17) is 3-5 mm.

5. A long-delay, low-loss broadband delay line with a defective open-circuit stub coupling strip as described in claim 2, characterized in that: The first open-circuit stub (11), the second open-circuit stub (12), the third open-circuit stub (13), and the fourth open-circuit stub (14) have the same structural dimensions; the length of the first open-circuit stub (11) is 0.1λ-0.2λ and the width is 0.1-0.5mm; the distance between the second open-circuit stub (12) and the third open-circuit stub (13) forming the interdigitated structure is 1.5-2mm, where λ is the wavelength corresponding to the antenna operating frequency band.

6. The long-delay, low-loss broadband delay line with defective open-circuit stub coupling stripe according to claim 1, characterized in that: The coupling strip (15) is spaced equally with the second open stub (12) and the third open stub (13), with a spacing of 0.7-1.0 mm. The coupling strip (15) has a length of 0.05λ-0.08λ and a width of 0.3-0.7 mm, where λ is the wavelength corresponding to the antenna's operating frequency band.

7. The long-delay, low-loss broadband delay line with defective open-circuit stub coupling stripe according to claim 1, characterized in that: The distance between one side of the first U-shaped defect ground (31) and the adjacent second U-shaped defect ground (32) is 0.05λ-0.15λ, where λ is the wavelength corresponding to the antenna operating frequency band.

8. The long-delay, low-loss broadband delay line with defective open-circuit stub coupling stripe according to claim 1, characterized in that: The first U-shaped defect (31) and the second U-shaped defect (32) have the same dimensions, with a length of 0.15λ-0.4λ and a width of 0.1-0.5mm, where λ is the wavelength corresponding to the antenna's operating frequency band.

9. A long-delay, low-loss broadband delay line with defective open-circuit stub coupling strip as described in claim 1, characterized in that: Two or more long-delay, low-loss broadband delay lines are connected in series through a cascaded transition microstrip line (4) to form a cascaded delay line. The maximum delay time of the cascaded two or more long-delay, low-loss broadband delay lines is 7.4 ns, and the average transmission loss is less than 2.6 dB.

10. A long-delay, low-loss broadband delay line with a defective open-circuit stub coupling strip according to claim 9, characterized in that: The cascaded transition microstrip line (4) has a width of 0.5-1.0 mm and a length of 5.5-9.5 mm; both ends of the cascaded transition microstrip line (4) are provided with 45° chamfers.

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