Ultrahigh-frequency hairpin type microstrip line band-pass filter

Abstract

The utility model relates to the technical field of band-pass filters, in particular to an ultra-high frequency hairpin type microstrip line band-pass filter. Comprising a hairpin type micro-strip, a reference ground plane and a substrate, the hairpin-type micro-strip is matched with the outer surface of the substrate; the substrate provided with the hairpin type micro-strip is also provided with a reference ground plane in a matched manner; the hairpin type micro-strip comprises a filtering input end, a parallel coupling line resonator and a filtering output end which are sequentially connected in series. And the in-band loss is reduced through the design of the filtering input ends with different sizes and the corresponding parallel coupling line resonators.

Description

Technical Field

[0001] This utility model relates to the field of bandpass filter technology, specifically to an ultra-high frequency hairpin microstrip bandpass filter. Background Technology

[0002] Microstrip bandpass filters are one of the key components in modern electronic systems. In practical applications, microstrip filters are easily integrated with other passive and active microwave circuit components, achieving the integration of microwave components and systems. Therefore, these filters are widely used in engineering design.

[0003] Hairpin microstrip bandpass filters are folded, parallel-coupled microstrip line filters. They consist of a U-shaped structure formed by half-wavelength microstrip lines coupled to adjacent U-shaped structures. By adjusting parameters such as the microstrip linewidth, hairpin spacing, hairpin arm length, and tap position of the U-shaped structures, the transmission and suppression of signals in specific frequency bands can be achieved. Hairpin microstrip bandpass filters are compact, suitable for implementing filtering functions in limited space, easy to integrate, and reduce costs. Due to their structural characteristics, they have advantages in achieving miniaturization and high performance. However, a current drawback of hairpin microstrip bandpass filters is high insertion loss. This is due to resistive and reactive losses in the coupling lines. Resistive loss is caused by inappropriate microstrip linewidth and impedance matching, while reactive loss is related to coupling and ultra-low frequency. Resistive loss leads to increased in-band loss, and the presence of reactance causes fluctuations in in-band loss. Utility Model Content

[0004] This invention provides an ultra-high frequency hairpin microstrip bandpass filter, which aims to solve the problem of large in-band insertion loss in the current hairpin microstrip bandpass filter structure.

[0005] The objective of this utility model is achieved through the following technical solution:

[0006] An ultra-high frequency hairpin microstrip bandpass filter includes: a hairpin microstrip, a reference ground plane, and a substrate;

[0007] The hairpin-shaped micro-line strip is mounted on the outer surface of the substrate; a reference ground plane is also mounted on the other outer surface of the substrate on which the hairpin-shaped micro-line strip is mounted.

[0008] The hairpin-type microstrip line includes a filter input terminal, a parallel coupled-line resonator, and a filter output terminal connected in series.

[0009] As a further improvement of this utility model, the lower surface of the substrate on which the hairpin-shaped micro-wire strip is installed can be detachably fixed or embedded in the reference ground plane.

[0010] As a further improvement of this utility model, the substrate is a Rogers 4350B high-frequency dielectric board with a thickness range of 0.250~0.270mm and a dielectric constant of 3.48.

[0011] As a further improvement of this utility model, the filter input end and the filter output end are symmetrically arranged about the center line of the hairpin-shaped micro-strip; both the filter input end and the filter output end include four impedance transformation sections of different sizes, and the impedance of each impedance transformation section is in the range of 30Ω~77Ω.

[0012] As a further improvement of this utility model, the four impedance transformation segments of different sizes include:

[0013] The impedance of the first impedance transformation section is 50Ω, the width is 0.52mm, and the length is 3mm;

[0014] The impedance of the second impedance transformation section is 33Ω, the width is 1mm, and the length is 1.66mm.

[0015] The impedance of the third impedance transformation section is 38Ω, the width is 0.82mm, and the length is 1.47mm.

[0016] The fourth impedance transformation section has an impedance of 30Ω, a width of 1.28mm, and a length of 2mm.

[0017] As a further improvement of this utility model, the parallel coupled-line resonator adopts a U-shaped or S-shaped structure.

[0018] As a further improvement to this utility model,

[0019] The parallel coupled-line resonator structure includes:

[0020] An input connection microstrip line is used to connect to the filter input terminal. The input connection microstrip line is configured as a right-angled triangle structure, and the right-angled side of the input connection microstrip line is connected to the filter input terminal.

[0021] The output connection microstrip line is used to connect the filter output terminal. The output connection microstrip line has the same structure as the input connection microstrip line and is symmetrically arranged.

[0022] A parallel-coupled microstrip line, one end of which is used to connect to one corner of an input connection microstrip line, and the other end of which is used to connect to one corner of an output connection microstrip line.

[0023] As a further improvement to this utility model,

[0024] The parallel-coupled microstrip line includes two parallel-coupled line sections and a U-shaped bend section, with the bottom end of the parallel-coupled line section connected to the U-shaped bend section;

[0025] The parallel spacing of the parallel coupling lines is 0.12~0.13mm, the length of the parallel coupling lines is 3~4mm, and the width is 0.12~0.13mm;

[0026] The U-shaped bend of the parallel-coupled microstrip line has an impedance of 25~40Ω, a width of 1.1~1.3mm, and a length of 1.5~1.8mm.

[0027] As a further improvement of this utility model, the frequency range of the hairpin-type microstrip bandpass filter is 9.5GHz~15GHz.

[0028] As a further improvement of this utility model, the reference ground plane adopts a copper cladding layer with a thickness of 0.25~0.27mm.

[0029] The beneficial effects of this invention are as follows: The ultra-high frequency hairpin microstrip bandpass filter of this invention provides support for the bandpass filter through the substrate, ensuring stable operation of the filter in harsh environments. A stable reference potential is provided for the filter through the reference ground plane, which helps improve the stability and reliability of the filter. The hairpin microstrip design facilitates integration with other microwave circuits, making it suitable for applications in miniaturized, high-density microwave circuits. Its compact structure eliminates the need for via grounding, thus eliminating errors introduced by vias and resulting in better electrical performance in the ultra-high frequency band. Furthermore, the hairpin microstrip design, through the sequentially connected filter input, parallel coupled-line resonator, and filter output, and by modifying the structure of the filter input, parallel coupled-line resonator, and filter output, and designing multiple impedances, further enhances the filter's filtering effect, resulting in lower insertion loss and higher selectivity within the passband, thereby solving the problem of high in-band insertion loss.

[0030] Furthermore, a specific dielectric constant contributes to more accurate signal transmission. A dielectric constant of 3.48 allows for better control of signal propagation speed and phase in high-frequency environments, reducing signal distortion and improving transmission accuracy. The Rogers 4350B high-frequency dielectric substrate is specifically designed for high-frequency applications, exhibiting low dielectric loss and stable performance across the high-frequency range. This makes the hairpin micro-strip more efficient in processing high-frequency signals, meeting the stringent requirements for high-frequency signal filtering. Simultaneously, the substrate possesses high insulation properties, effectively preventing crosstalk and leakage between signals, thus improving the reliability and stability of the entire circuit.

[0031] Furthermore, employing four impedance transformation segments of different sizes allows for gradual adjustment and matching of signals at different frequencies, resulting in smoother signal transmission and reduced reflection and loss. By rationally designing the size and impedance of each impedance transformation segment, targeted filtering of signals within a specific frequency range can be achieved.

[0032] Furthermore, the symmetrically arranged input and output microstrip lines ensure signal symmetry during input and output, which is beneficial for maintaining the stability of filtering characteristics. The symmetrical structure ensures that signals experience similar electromagnetic environments when passing through the resonator, thereby improving the consistency and reliability of the filter. The parallel-coupled microstrip lines increase the coupling between signals. By rationally designing parameters such as the length, spacing, and width of the parallel-coupled microstrip lines, the coupling strength can be controlled to achieve resonance and filtering at specific frequencies. This coupling effect can effectively select and suppress signals at specific frequencies, improving the selectivity and performance of the filter. The input and output microstrip lines are set in a triangular structure. This unique shape enables better impedance matching during signal transmission. The triangular structure can gradually change the characteristic impedance of the microstrip line to match the impedance of the filter input and output terminals, reducing signal reflection and improving signal transmission efficiency.

[0033] Furthermore, the parallel-coupled microstrip line structure achieves complex functions within a limited space. The design of the parallel coupling line section and the U-shaped bend section makes the entire microstrip line structure more compact, saving circuit board space and facilitating the miniaturization and integration of electronic devices. The parallel coupling line spacing is 0.12~0.13mm, and this small spacing achieves a strong coupling effect. Precise control of the coupling line spacing can adjust the coupling strength of the signal in the parallel coupling section, thereby enabling more effective selection and filtering of signals at specific frequencies and reducing in-band loss. The U-shaped bend section design, with a width of 1.1~1.3mm and a length of 1.5~1.8mm, takes into account the characteristic changes of the signal at the bend. Through reasonable size design, signal loss and reflection at the bend can be reduced, improving the performance stability of the circuit. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a structural diagram of the ultra-high frequency hairpin microstrip bandpass filter in this embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of the structure of the filter input terminal in an embodiment of this utility model;

[0037] Figure 3 This is a schematic diagram of the structure of the filter output terminal in an embodiment of this utility model;

[0038] Figure 4 This is a schematic diagram of the structure of the parallel coupled-line resonator in an embodiment of this utility model;

[0039] Figure 5 This is a schematic diagram of the hairpin-type micro-wire strip structure in an embodiment of this utility model;

[0040] Figure 6 This is a simulation result diagram of the filter in ADS in an embodiment of this utility model;

[0041] Figure 7 This is a simulation result diagram of the filter in HFSS in an embodiment of this utility model.

[0042] In the figure, 1 is the substrate; 2 is the reference ground plane; 3 is the filter input terminal; 4 is the parallel coupled-line resonator; 5 is the filter output terminal; 3.1 is the first impedance transformation segment; 3.2 is the second impedance transformation segment; 3.3 is the third impedance transformation segment; 3.4 is the fourth impedance transformation segment; 4.1 is the input connection microstrip line; 4.2 is the parallel coupled microstrip line; 4.3 is the output connection microstrip line; 5.1 is the fifth impedance transformation segment; 5.2 is the sixth impedance transformation segment; 5.3 is the seventh impedance transformation segment; 5.4 is the eighth impedance transformation segment. Detailed Implementation

[0043] To make the objectives and technical solutions of this utility model clearer and easier to understand, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. The specific embodiments described herein are only for explaining the present utility model and are not intended to limit the present utility model.

[0044] The technical solution of this utility model will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. The described embodiments are only some embodiments of this utility model, and not all embodiments.

[0045] Example 1

[0046] like Figure 1-Figure 5 As shown, this embodiment provides an ultra-high frequency hairpin microstrip bandpass filter, including: a hairpin microstrip, a reference ground plane, and a substrate.

[0047] The lower surface of the substrate with the hairpin-shaped micro-line strip is fitted with a reference ground plane.

[0048] A hairpin-shaped micro-line is mounted on the outer surface of the substrate; a reference ground plane is also mounted on the other outer surface of the substrate on which the hairpin-shaped micro-line is mounted; the reference ground plane uses a copper plating layer with a thickness of 0.254 mm. The lower surface of the substrate on which the hairpin-shaped micro-line is mounted is detachably fixed to the reference ground plane or embedded. This embodiment uses a mechanically detachable fixed mounting.

[0049] The hairpin-type micro-strip line includes a filter input terminal 3, a parallel coupled-line resonator 4, and a filter output terminal 5 connected in series.

[0050] In general circuit design, the characteristic impedance of commonly used transmission lines is 50 ohms. When designing printed circuit boards (PCBs), once the PCB material, dielectric constant, and thickness are determined, the width of the microstrip line can be largely determined and used as the standard for a 50-ohm transmission line. However, in practical applications, we found that changing the microstrip line width actually improves the matching with microwave devices. This is because the parallel-coupled resonator is not a standard 50-ohm impedance, leading to a mismatch with the 50-ohm front-end, affecting not only the standing wave ratio (SWR) but also deteriorating in-band losses. Therefore, filter input 3 and filter output 5 are symmetrically positioned about the center line of the hairpin-shaped microstrip line. Both filter input 3 and filter output 4 include four impedance transformation segments of different sizes, with each segment having an impedance ranging from 30Ω to 77Ω, to improve the matching between the microstrip line and the filter and reduce in-band insertion loss.

[0051] In coaxial cables or their equivalent microstrip lines, 30 ohms provides the highest transmission power, while 77 ohms minimizes signal loss. The commonly used 50-ohm impedance in existing technologies is merely a compromise between the average of 30 and 77 ohms in engineering applications, aiming to simultaneously maximize power transmission and minimize loss. Furthermore, a 50-ohm transmission impedance matches the port impedances of both half-wavelength dipole and quarter-wavelength monopole antennas, minimizing reflection loss. Therefore, this embodiment does not use the traditional 50-ohm impedance transformation at the input and output terminals. Instead, the input and output are divided into four segments, each with an impedance ranging from 30 to 77 ohms, less than a quarter wavelength in length, thus addressing the problem of excessive in-band loss in existing filters.

[0052] The parallel-coupled-line resonator 4 adopts a U-shaped or S-shaped structure. The structure of the parallel-coupled-line resonator 4 includes: an input connection microstrip line 4.1 for matching the filter input terminal, an output connection microstrip line 4.3 for matching the filter output terminal, and a parallel-coupled microstrip line 4.2. The input connection microstrip line 4.1 is configured as a right-angled triangle, with its right-angled side connected to the filter input terminal 3. The output connection microstrip line 4.3 connects to the filter output terminal 5. The output connection microstrip line 4.3 has the same structure as the input connection microstrip line 4.1 and is symmetrically arranged. One end of the parallel-coupled microstrip line 4.2 is used to connect to one corner of the input connection microstrip line, and the other end is used to connect to one corner of the output connection microstrip line.

[0053] The parallel spacing of the line coupling lines is 0.12~0.13mm, the length of the parallel coupling lines is 3~4mm, and the width is 0.12~0.13mm;

[0054] The U-shaped bend of the parallel-coupled microstrip line has an impedance of 25~40Ω, a width of 1.1~1.3mm, and a length of 1.5~1.8mm.

[0055] The bandwidth of the parallel coupled-line resonator 4 is mainly determined by the spacing of the coupled lines. Reducing the spacing between adjacent couplers can widen the bandwidth. The center frequency is mainly determined by the length of the resonator; the longer the resonator, the lower the center frequency, and vice versa. Therefore, considering integration, a suitable length and spacing of the coupled lines should be selected for the parallel coupled-line resonator 4.

[0056] The input connection microstrip line is configured as a triangular structure, while the output connection microstrip line 4.3 has the same structure as the input connection microstrip line 4.1 and is symmetrically arranged. One end of the parallel coupling microstrip line 4.2 is used for mating connection with one end of the input connection microstrip line, and the other end is used for mating connection with the output connection microstrip line.

[0057] In this embodiment, the input connecting microstrip line 4.1 and the parallel coupled microstrip line 4.2 are configured as a triangular structure. This unique shape can improve the signal transmission characteristics. The triangular structure can reduce signal reflection and loss, and improve signal transmission efficiency. At the same time, the triangular structure also has a certain filtering effect, which can perform preliminary screening of signals of specific frequencies.

[0058] Furthermore, the frequency range of the ultra-high frequency hairpin microstrip bandpass filter in this embodiment is 9.5 GHz to 15 GHz.

[0059] Example 2

[0060] In another embodiment of this utility model, the dimensions of the four impedance transformation segments of the filter input terminal 3 and their corresponding characteristic impedances include:

[0061] The impedance of the first impedance transformation section 3.1 is 50Ω, the width is 0.52mm, and the length is 3mm;

[0062] The impedance of the second impedance transformation section 3.2 is 33Ω, the width is 1mm, and the length is 1.66mm;

[0063] The impedance of the third impedance transformation section 3.3 is 38Ω, the width is 0.82mm, and the length is 1.47mm;

[0064] The impedance of the fourth impedance transformation section 3.4 is 30Ω, the width is 1.28mm, and the length is 2mm.

[0065] Similarly, the dimensions and corresponding impedance value of the fifth impedance transformation segment 5.1 are the same as those of the fourth impedance transformation segment 3.4, with an impedance of 30Ω, a width of 1.28mm, and a length of 2mm; the dimensions and corresponding impedance value of the sixth impedance transformation segment 5.2 are the same as those of the third impedance transformation segment 3.3, with an impedance of 38Ω, a width of 0.82mm, and a length of 1.47mm; the dimensions and corresponding impedance value of the seventh impedance transformation segment 5.3 are the same as those of the second impedance transformation segment 3.2, with an impedance of 33Ω, a width of 1mm, and a length of 1.66mm; and the dimensions and corresponding impedance value of the eighth impedance transformation segment 5.4 are the same as those of the first impedance transformation segment 3.1, with an impedance of 50Ω, a width of 0.52mm, and a length of 3mm.

[0066] By setting four impedance transformation segments of different sizes, targeted filtering of signals at different frequencies can be achieved. Different impedance values ​​and sizes can adapt to the characteristics of signals at different frequencies, thereby achieving a more precise filtering effect, effectively removing interference signals, and improving signal purity.

[0067] For the first impedance transformation section, an impedance of 50Ω is a common standard impedance value with good versatility. Its dimensions of 0.52mm width and 3mm length provide suitable impedance characteristics within a specific frequency range, enabling effective signal transmission and filtering. The second impedance transformation section has an impedance of 33Ω, a width of 1mm, and a length of 1.66mm. This parameter combination allows for some adjustment of the signal impedance, making it more suitable for the requirements of subsequent circuits. Simultaneously, the shorter length reduces signal transmission time in this section, improving signal processing speed. The third impedance transformation section has an impedance of 38Ω, a width of 0.82mm, and a length of 1.47mm. This parameter setting further optimizes the signal impedance characteristics, bringing it closer to the ideal filtering effect. The smaller width and moderate length save space and improve circuit integration while ensuring performance. The fourth impedance transformation section has an impedance of 30Ω, a width of 1.28mm, and a length of 2mm. The lower impedance value provides better signal matching at the output, reducing signal reflection. The longer length increases the signal transmission path in this section, further improving the filtering effect.

[0068] Example 3

[0069] As another embodiment of this utility model, such as Figure 4 As shown, the parallel coupled-line resonator 4 in this embodiment adopts a U-shaped structure, and the parallel coupled microstrip line 4.2 includes two parallel coupled-line sections and a U-shaped bend section. Figure 4 As shown, the distance between the parallel lines in each parallel coupling line section is set.

[0070] In this embodiment, the parallel coupling line spacing is 0.125 mm, the parallel coupling line length is 3.5 mm, and the width is 0.125 mm. The U-shaped bend of the parallel coupling microstrip line has an impedance of 30 Ω, a width of 1.28 mm, and a length of 1.62 mm.

[0071] The parallel coupling lines are spaced 0.125mm apart. This close spacing enhances coupling and improves filter performance. Precise spacing control ensures more stable and efficient signal transmission between the coupling lines.

[0072] The parallel coupling line is 3.5 mm long and 0.125 mm wide. This size design achieves good coupling within a specific frequency range without occupying excessive space. Appropriate length and width contribute to improved filter selectivity and passband characteristics.

[0073] The U-shaped bend has an impedance of 30Ω, a width of 1.28mm, and a length of 1.62mm. This specific impedance design reduces reflections and losses when the signal bends, ensuring signal continuity. The dimensions of the U-shaped bend also allow for flexible circuit layout, improving overall integration.

[0074] Example 4

[0075] In another embodiment of this invention, the dielectric constant of the substrate also affects the filter performance; the smaller the dielectric constant, the lower the in-band loss of the filter. Therefore, in this embodiment, substrate 1 uses a Rogers 4350B high-frequency dielectric board with a thickness of 0.254 mm and a dielectric constant of 3.48. The 0.254 mm thickness of the Rogers 4350B high-frequency dielectric board provides stable electrical performance during high-frequency signal transmission. A suitable thickness reduces signal transmission loss within the substrate, ensuring signal strength and quality. Simultaneously, this thickness facilitates circuit layout and design, making the entire system more compact and reliable. The Rogers 4350B high-frequency dielectric board with a dielectric constant of 3.48 maintains good dielectric performance in high-frequency environments. A moderate dielectric constant effectively controls signal transmission speed and impedance, reducing signal reflection and distortion. This helps improve the filter's performance and stability, ensuring accurate signal transmission.

[0076] In summary, this invention also uses ADS and HFSS for simulation to verify the effectiveness and practicality of its structure.

[0077] like Figure 6The simulation results of the filter in ADS are shown in the figure above. It can be seen from the figure that the in-band insertion loss is less than 1dB, the input and output standing wave ratio is less than -18, and the out-of-band rejection is greater than 20dB (outside the 2GHz sideband), but the center frequency is too high.

[0078] like Figure 7 The simulation results of the filter in HFSS are shown in the figure above. It can be seen from the figure that the in-band insertion loss is less than 1dB, the input and output standing wave ratio is less than -12, the out-of-band rejection is greater than 20dB (outside the 2GHz sideband), and the bandwidth meets the requirements.

[0079] Comparing the ADS theoretical simulation results, it is clear that after HFSS simulation, the bandwidth of the filter becomes narrower and the center frequency is lower. In reality, not only will coupling occur between two adjacent coupling lines, but coupling will also occur between all coupling lines in the resonator.

[0080] The ADS layout was imported into HFSS for further modeling and simulation. HFSS simulation results show that the filter model achieves the expected results: within the 9.5GHz~15GHz passband, it satisfies the requirements of in-band insertion loss less than 1, input and output VSWR better than -12dB, and good out-of-band suppression.

Claims

1. A high-frequency hairpin-type microstrip bandpass filter, characterized in that, include: Hairpin-shaped micro-strip, reference ground plane, and substrate; The hairpin-shaped micro-wire strip is mounted on the outer surface of the substrate; A reference ground plane is also mounted on the other outer surface of the substrate on which the hairpin-shaped micro-line strip is mounted. The hairpin-type microstrip line includes a filter input terminal, a parallel coupled-line resonator, and a filter output terminal connected in series.

2. The ultra-high frequency hairpin microstrip bandpass filter according to claim 1, characterized in that, The lower surface of the substrate on which the hairpin-shaped micro-strip is mounted can be detachably fixed or embedded in the reference ground plane.

3. The ultra-high frequency hairpin microstrip bandpass filter according to claim 1, characterized in that, The substrate is a Rogers 4350B high-frequency dielectric board with a thickness ranging from 0.250 to 0.270 mm and a dielectric constant of 3.

48.

4. The ultra-high frequency hairpin microstrip bandpass filter according to claim 1, characterized in that, The filter input and filter output are symmetrically positioned about the center line of the hairpin-shaped micro-strip. Both the filter input and filter output include four impedance transformation segments of different sizes, with each segment having an impedance ranging from 30Ω to 77Ω.

5. The ultra-high frequency hairpin microstrip bandpass filter according to claim 4, characterized in that, The four impedance transformation segments of different sizes include: The impedance of the first impedance transformation section is 50Ω, the width is 0.52mm, and the length is 3mm; The impedance of the second impedance transformation section is 33Ω, the width is 1mm, and the length is 1.66mm. The impedance of the third impedance transformation section is 38Ω, the width is 0.82mm, and the length is 1.47mm. The fourth impedance transformation section has an impedance of 30Ω, a width of 1.28mm, and a length of 2mm.

6. The ultra-high frequency hairpin microstrip bandpass filter according to claim 1, characterized in that, The parallel coupled-line resonator adopts a U-shaped or S-shaped structure.

7. The ultra-high frequency hairpin microstrip bandpass filter according to claim 6, characterized in that, The parallel coupled-line resonator structure includes: An input connection microstrip line is used to connect to the filter input terminal. The input connection microstrip line is configured as a right-angled triangle structure, and the right-angled side of the input connection microstrip line is connected to the filter input terminal. The output connection microstrip line is used to connect the filter output terminal. The output connection microstrip line has the same structure as the input connection microstrip line and is symmetrically arranged. A parallel-coupled microstrip line, one end of which is used to connect to one corner of an input connection microstrip line, and the other end of which is used to connect to one corner of an output connection microstrip line.

8. The ultra-high frequency hairpin microstrip bandpass filter according to claim 7, characterized in that, The parallel-coupled microstrip line includes two parallel-coupled line sections and a U-shaped bend section, with the bottom end of the parallel-coupled line section connected to the U-shaped bend section; The parallel spacing of the parallel coupling lines is 0.12~0.13mm, the length of the parallel coupling lines is 3~4mm, and the width is 0.12~0.13mm; The U-shaped bend of the parallel-coupled microstrip line has an impedance of 25~40Ω, a width of 1.1~1.3mm, and a length of 1.5~1.8mm.

9. The ultra-high frequency hairpin microstrip bandpass filter according to any one of claims 1 to 8, characterized in that, The frequency range of the hairpin-type microstrip bandpass filter is 9.5 GHz to 15 GHz.

10. The ultra-high frequency hairpin microstrip bandpass filter according to claim 1, characterized in that, The reference ground plane uses a copper cladding layer with a thickness of 0.25~0.27mm.

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