Hairpin filter and optical communication testing apparatus

Abstract

The utility model discloses a kind of hairpin type filter and optical communication testing device, the hairpin type filter includes ceramic substrate and first metal layer, first metal layer is provided with signal input line, resonator group, and signal output line, resonator group includes at least two orders hairpin type resonator, first metal layer is also provided with open-circuit branch and parallel coupling line;Parallel coupling line and resonator group take parallel coupling mode and carry out signal transmission;Open-circuit branch is set on signal input line and signal output line, length is between one fifth wavelength to one third wavelength, the hairpin type filter has the advantages that parasitic passband suppression effect is good, small in size, meet the demand of current high-speed high-frequency field to high performance, miniaturized filter.

Description

Technical Field

[0001] This utility model relates to the field of electronic components, and in particular to hairpin filters and optical communication testing devices. Background Technology

[0002] Filters are an indispensable component of radio frequency (RF) circuits. Their performance directly determines the quality of signal transmission and even the success or failure of the entire system. With the rapid development of RF integrated circuits and advancements in manufacturing processes, RF systems have increasingly higher demands on the size and performance of RF devices. Against this backdrop, filters made from ceramic substrates with high dielectric constants and low insertion loss are gradually gaining popularity among RF engineers. The high dielectric constant of ceramic substrates allows for significant reduction in filter size, and ceramic substrate thin-film microstrip filters offer advantages in RF link cascading.

[0003] In existing technologies, microstrip filters made from ceramic substrates mainly include parallel-coupled filters, hairpin filters, and elliptic function filters. For hairpin bandpass filters, parasitic passbands appear at integer multiples of the design frequency, affecting the overall performance of the filter. Furthermore, most hairpin bandpass filters are pre-packaged and not suitable for applications such as gold wire bonding.

[0004] Therefore, it is particularly important to provide hairpin filters that are small in size, have excellent performance, and can be used in applications such as gold wire bonding. Utility Model Content

[0005] This invention provides a hairpin filter and an optical communication testing device to at least solve the aforementioned problems existing in related technologies.

[0006] To solve the above-mentioned technical problems, the technical solution of this utility model is as follows:

[0007] According to a first aspect of the embodiments of this application, a hairpin filter is provided, including a ceramic substrate and a first metal layer located on one side surface of the ceramic substrate. The first metal layer is provided with a signal input line, a resonator group, and a signal output line. The resonator group includes at least two-order hairpin resonators. The first metal layer is also provided with open-circuit stubs and parallel coupling lines.

[0008] The parallel coupling line transmits signals in a parallel coupling manner with the resonator group, including an input parallel coupling line and an output parallel coupling line respectively disposed on both sides of the resonator group;

[0009] The open-circuit stub is disposed on the signal input line and on the signal output line, and the length of the open-circuit stub is between one-fifth and one-third of the wavelength.

[0010] In an optional embodiment, the first metal layer is further provided with bonding pads;

[0011] The bonding pads include a first pad and a second pad respectively disposed on both sides of the resonator group. The first pad is connected to the input parallel coupling line through the signal input line, and the second pad is connected to the output parallel coupling line through the signal output line.

[0012] In an optional embodiment, the top view of both the first pad and the second pad is a square, and the side length of the square is greater than or equal to 100 μm.

[0013] In an optional embodiment, the first metal layer is further provided with a first metal sheet, a second metal sheet, a third metal sheet and a fourth metal sheet, wherein the first metal sheet and the second metal sheet are respectively disposed on opposite sides of the first pad, and the third metal sheet and the fourth metal sheet are respectively disposed on opposite sides of the second pad;

[0014] The first metal sheet has a first through hole at its center, and the second metal sheet has a second through hole at its center. The first distance between the center point of the first pad and the center point of the first through hole, and the second distance between the first pad and the center of the second through hole are both less than 150 μm, and the difference between the first distance and the second distance is less than or equal to 10 μm.

[0015] The third metal sheet has a third through hole at its center, and the fourth metal sheet has a fourth through hole at its center. The third distance between the center point of the second pad and the center point of the third through hole, and the fourth distance between the second pad and the center of the fourth through hole are both less than 150 μm, and the difference between the third distance and the fourth distance is less than or equal to 10 μm.

[0016] In an optional embodiment, the angle between the open stub and the input signal line is a first preset angle, and the angle between the open stub and the output signal line is a second preset angle; the range of both the first preset angle and the second preset angle is 45 degrees to 135 degrees.

[0017] In an optional embodiment, the hairpin filter operates in the Ka band.

[0018] In an optional embodiment, the spacing between adjacent hairpin resonators in the resonator group is a fifth spacing, the spacing between the input parallel coupling line and the first-order hairpin resonator in the resonator group, and the spacing between the output parallel coupling line and the last-order hairpin resonator in the resonator group are all sixth spacings, and the fifth spacing is greater than or equal to the sixth spacing.

[0019] The width and length of the input parallel coupling line and the output parallel coupling line are equal.

[0020] In an optional embodiment, the open-circuit stub on the signal input line is a first open-circuit stub, and the open-circuit stub on the signal output line is a second open-circuit stub.

[0021] The first open-circuit stub and the second open-circuit stub are axially symmetrical about the resonant group, and the distance between the first open-circuit stub and the input parallel coupling line is the seventh distance, and the distance between the first open-circuit stub and the first pad is the eighth distance, wherein the seventh distance is greater than the eighth distance.

[0022] In an optional embodiment, the hairpin filter further includes a second metal layer disposed on the other side surface of the ceramic substrate and disposed opposite to the first metal layer;

[0023] The thickness of the ceramic substrate ranges from 0.12 mm to 0.4 mm.

[0024] According to a second aspect of the embodiments of this application, an optical communication testing apparatus is provided, including the hairpin filter described above.

[0025] According to a third aspect of the embodiments of this application, a communication device is provided, including the hairpin filter described above.

[0026] The above-mentioned technical solution provided in this application has the following beneficial effects:

[0027] The hairpin filter provided in this embodiment includes a ceramic substrate and a first metal layer located on one side of the ceramic substrate. The first metal layer is provided with a signal input line, a resonator group, and a signal output line. The resonator group includes at least two-order hairpin resonators. The first metal layer is also provided with open-circuit stub parallel coupling lines. The parallel coupling lines transmit signals in a parallel coupling manner with the resonator group, including input parallel coupling lines and output parallel coupling lines respectively disposed on both sides of the resonator group. Signal transmission through parallel coupling is beneficial for miniaturization of the overall device. The open-circuit stubs are disposed on the signal input line and the signal output line. The length of the open-circuit stubs is between one-fifth and one-third of the wavelength, which can effectively suppress parasitic passbands and reduce in-band losses. The hairpin filter provided in this invention has the advantages of good parasitic passband suppression and small size, meeting the current demand for high-performance, miniaturized filters in high-speed and high-frequency fields.

[0028] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the structure of a hairpin filter provided in an embodiment of this utility model.

[0031] Figure 2 This is a schematic diagram of the structure of a resonator group provided in an embodiment of the present invention.

[0032] Figure 3 This is a schematic diagram of the structure of a first metal layer provided in an embodiment of the present invention.

[0033] Figure 4 This is a simulation circuit schematic provided by an embodiment of the present invention.

[0034] Figure 5 This is a simulation hairpin filter model diagram provided in an embodiment of the present invention.

[0035] Figure 6 This is a schematic diagram of the dimensions of a simulated hairpin filter provided in an embodiment of this utility model.

[0036] Figure 7 This is a simulation-designed hairpin filter in-band return loss curve provided by an embodiment of this utility model.

[0037] Figure 8 This is a simulation-designed hairpin filter in-band insertion loss curve provided by an embodiment of this utility model.

[0038] Figure 9 This is a measured in-band return loss curve of a hairpin filter provided in this embodiment of the present invention.

[0039] Figure 10 This is a measured in-band insertion loss curve of a hairpin filter provided in this embodiment of the present invention.

[0040] The corresponding reference numerals in the figure are:

[0041] 1-Ceramic substrate;

[0042] 2-First metal layer; 21-Signal input line; 22-Signal output line; 23-Resonator group; 231-First microstrip coupling line; 232-Second microstrip coupling line; 233-First microstrip line bend structure; 234-Second microstrip line bend structure; 235-Straight microstrip line structure; 24-Open circuit stub; 241-First open circuit stub; 242-Second open circuit stub; 25-Bonding pad; 251-First pad; 252-Second pad; 261-Input parallel coupling line; 262-Output parallel coupling line; 281-First metal sheet; 282-Second metal sheet; 283-Third metal sheet; 284-Fourth metal sheet; 291-First via; 292-Second via; 293-Third via; 294-Fourth via. Detailed Implementation

[0043] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0044] The term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of this application. In the description of this application, it should be understood that the terms "upper," "lower," "top," "bottom," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein.

[0045] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included. For example, a specified range from “1 to 10” should be considered to include any and all subranges between the minimum value 1 and the maximum value 10. Exemplary subranges of the range 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

[0046] Please see Figure 1 , Figure 1 This is a schematic diagram of a hairpin filter provided in an embodiment of this application. The hairpin filter includes a ceramic substrate 1 and a first metal layer 2 located on one side surface of the ceramic substrate 1. The first metal layer 2 is provided with a signal input line 21, a resonator group 23, and a signal output line 22. The resonator group 23 includes at least two-order hairpin resonators. The first metal layer 2 is also provided with an open-circuit stub 24 and a parallel coupling line.

[0047] The parallel coupling lines transmit signals in a parallel coupling manner with the resonator group 23, including an input parallel coupling line 261 and an output parallel coupling line 262 respectively disposed on both sides of the resonator group 23.

[0048] The open stub 24 is disposed on the signal input line 21 and on the signal output line 22, and the length of the open stub 24 is between one-fifth and one-third of the wavelength.

[0049] For example, such as Figure 1 As shown, the hairpin filter includes a ceramic substrate 1 and a first metal layer 2 located on one side surface of the ceramic substrate 1. The first metal layer 2 is provided with a signal input line 21, a signal output line 22, and a resonator group 23. The signal input line 21 and the signal output line 22 are respectively disposed on both sides of the resonator group 23. The resonator group 23 is provided with at least two-order hairpin resonators, that is, the resonator group 23 includes at least a first-order hairpin resonator and a last-order hairpin resonator. The signal input line 21, the resonator group 23, and the signal output line 22 are arranged sequentially along a first direction.

[0050] Please continue reading Figure 1The first metal layer 2 is also provided with parallel coupling lines. These parallel coupling lines and the resonator group 23 transmit signals via parallel coupling. Specifically, the parallel coupling lines include an input parallel coupling line 261 and an output parallel coupling line 262 located on both sides of the resonator. Specifically, the input parallel coupling line 261 is parallel-coupled to the first-order hairpin resonator, and the output parallel coupling line 262 is parallel-coupled to the last-order hairpin resonator. Furthermore, each hairpin resonator in the resonator group 23 also transmits signals via parallel coupling with its adjacent hairpin resonators. This invention achieves miniaturization of the overall device by using the parallel coupling between the ceramic substrate 1 and the microstrip line.

[0051] Continue as Figure 1 As shown, the first metal layer 2 is also provided with open stubs 24. The open stubs 24 are provided on the signal input line 21 and the signal output line 22. That is, there are two open stubs 24, and their length is between one-fifth and one-third of the wavelength.

[0052] Optionally, the open branch 24 can be implemented in the form of an open microstrip line.

[0053] Preferably, the length of the open-circuit stub 24 is one-quarter wavelength. This is because parasitic passbands occur at integer multiples of the filter's design frequency, and the λ / 4 open-circuit stub 24 is equivalent to a short circuit at the design frequency, suppressing energy transfer at specific frequencies and improving the filter's selectivity. Furthermore, parasitic modes typically depend on phase matching and coupling paths between resonators. Introducing the λ / 4 open-circuit stub 24 alters the signal phase relationship at certain frequencies, thereby disrupting the excitation conditions for parasitic modes. It should be noted that the one-quarter wavelength here refers to the microstrip line length designed for the filter's operating frequency band.

[0054] Therefore, the hairpin resonator provided in the above embodiment not only uses the ceramic substrate 1 and the resonator group 23 to transmit signals in a parallel coupling manner, but also achieves miniaturization of the overall device because the parallel coupling unit spacing of the resonator group 23 is small. Furthermore, the open-circuit stubs 24 are provided on the signal input line 21 and the signal output line 22, which can suppress parasitic passbands and improve the selectivity of the filter. Through the above structural settings, the hairpin filter has the advantages of suppressing parasitic passbands and small size, which meets the current demand for high-performance and miniaturized filters in the high-speed and high-frequency field.

[0055] In some exemplary embodiments, the first metal layer 2 is further provided with bonding pads 25; the bonding pads 25 include a first pad 251 and a second pad 252 respectively disposed on both sides of the resonator group 23, the first pad 251 is connected to the input parallel coupling line 261 through the signal input line 21, and the second pad 252 is connected to the output parallel coupling line 262 through the signal output line 22.

[0056] like Figure 1 As shown, in order to be suitable for applications such as gold wire bonding, the embodiments of this application provide bonding pads 25 on both sides of the resonator group 23. Specifically, the bonding pads 25 include a first pad 251 and a second pad 252. The first pad 251 is connected to the input parallel coupling line 261 through the signal input line 21, and the second pad 252 is connected to the output parallel coupling line 262 through the signal output line 22, so that the bonding pads 25 can be matched by gold wire bonding, making the filter convenient for application and probe testing.

[0057] This embodiment of the application optimizes the structure of the signal input line 21 and the signal output line 22 by providing bonding pads 25, enabling the filter to be suitable for applications such as gold wire bonding.

[0058] In some exemplary implementations, such as Figure 3 As shown, the angle between the open-circuit stub 24 and the input signal line is a first preset angle α, and the angle between the open-circuit stub 24 and the output signal line is a second preset angle α. Both the first and second preset angles α range from 45 degrees to 135 degrees. This design allows the open-circuit stub 24 to be used in hairpin filters with different operating frequencies, thus allowing for different angles to be designed according to the parasitic passband suppression requirements at different operating frequencies. The introduction of these angles creates multipath coupling between the open-circuit stub 24 and the main transmission path. This coupling can effectively disrupt the propagation path of parasitic modes, thereby suppressing their propagation. Furthermore, to ensure a symmetrical distribution of the entire structure, the first preset angle α is equal to the second preset angle α.

[0059] Preferably, the first preset angle α and the second preset angle α are equal and both are 90°, meaning the open stub 24 is perpendicular to both the input and output signal lines. The perpendicular open stub 24 effectively reflects high-frequency signals, thus forming a high-impedance "barrier" in the high-frequency band to suppress the propagation of parasitic modes. This structure has a good suppression effect on parasitic modes at specific frequencies, especially harmonic modes related to the length of the open stub 24. Furthermore, the capacitance effect can be precisely controlled by adjusting the length and width of the open stub 24, thereby optimizing the suppression effect of parasitic modes.

[0060] In some exemplary embodiments, the opening directions of adjacent hairpin resonators in the resonator group 23 are opposite;

[0061] Each hairpin resonator in the resonant group includes a first microstrip coupling line 231, a second microstrip coupling line 232, a first microstrip line bending structure 233, a second microstrip line bending structure 234, and a microstrip line straight structure 235. The two ends of the microstrip line straight structure 235 are respectively connected to the first microstrip line bending structure 233 and the second microstrip line bending structure 234. The other end of the first microstrip line bending structure 233 is connected to the first microstrip coupling line 231, and the other end of the second microstrip line bending structure 234 is connected to the second microstrip coupling line 232. The first microstrip coupling line 231 and the second microstrip coupling line 232 are parallel, and the width and length of the first microstrip coupling line 231 and the second microstrip coupling line 232 are equal.

[0062] For example, such as Figure 1 As shown, the hairpin resonators in resonator group 23 have opposite opening directions to their adjacent hairpin resonators, while each hairpin resonator has the same shape, namely a U-shaped resonator. The basic principle is to form a hairpin resonator by bending a half-wavelength microstrip line.

[0063] For details, please refer to Figure 2 Each hairpin resonator includes a first microstrip coupling line 231, a second microstrip coupling line 232, a first microstrip line bending structure 233, a second microstrip line bending structure 234, and a microstrip line straight structure 235. The two ends of the microstrip line straight structure 235 are connected to one end of the first microstrip line bending structure 233 and one end of the second microstrip line bending structure 234, respectively. The other end of the first microstrip line bending structure 233 is connected to the first microstrip coupling line 231, and the second microstrip coupling line 232 of the second microstrip line bending structure 234 is connected to it. The first microstrip coupling line 231 and the second microstrip coupling line 232 are parallel and have equal length and width. In the above structure, the shape of the U-shaped resonator allows for a longer electrical length within a limited space, thereby significantly reducing the physical size of the filter in high-frequency bands (such as millimeter-wave bands). This compact structure is particularly suitable for the miniaturization and lightweight requirements of modern wireless communication systems. Furthermore, the parallel coupling between the hairpin resonators provides a stable coupling coefficient, and the coupling strength can be precisely controlled by adjusting the spacing and linewidth between the resonators.

[0064] In some exemplary embodiments, the hairpin filter further includes a second metal layer disposed on the other side surface of the ceramic substrate 1 and disposed opposite to the first metal layer 2; the thickness of the ceramic substrate 1 is in the range of 0.12mm-0.4mm.

[0065] For example, the hairpin filter further includes a second metal layer (not shown in the figure), which is disposed on the other side surface of the ceramic substrate 1 and is disposed opposite to the first metal layer 2. The second metal layer serves as a ground layer, provides a reference ground potential, and together with the first metal layer 2, constitutes the electromagnetic field distribution of the microstrip line.

[0066] Considering cost and processability, the ceramic substrate 1 used in this application requires the dielectric constant to be as high as possible to ensure that the designed filter size is small enough. Therefore, when selecting the ceramic substrate 1, a material with high dielectric constant and low loss is selected, such as alumina ceramic, aluminum nitride ceramic, barium titanate (BaTiO3) ceramic composite material, zirconium titanate ceramic (ZrTiO4), etc.

[0067] The thickness of the ceramic substrate 1 ranges from 0.12mm to 0.4mm. This is because when the filter is applied to applications such as gold wire bonding, the bonding pads 25 need to be provided with ground vias. Therefore, the thickness of the ceramic substrate 1 should not be too thin. A reasonable selection of the thickness of the ceramic substrate 1 can take into account both the miniaturization of the device and the setting requirements of the bonding pads 25.

[0068] Optionally, the thickness of the ceramic substrate 1 can be 0.127 mm, 0.254 mm, 0.381 mm, etc.

[0069] Optionally, the first metal layer 2 and the second metal layer are made of nickel-palladium-gold (NiPG) material, with nickel (Ni) as the bottom layer, palladium (Pd) as the middle layer, and gold (Au) as the bottom layer. This is because using NiPG material can reduce the thickness of the metal layers, achieving device miniaturization while reducing costs; moreover, Pd and Ni in NiPG material are not easily oxidized and are more stable than pure gold, the Au surface ensures good bonding with the gold wire, and Ni / Pd can provide a support structure; furthermore, NiPG material is suitable for ball bonding and wedge bonding, adapting to various bonding equipment and processes.

[0070] When filters are applied in gold wire bonding cascade scenarios, the diameter of the bonding wires is typically around 15~50μm, and the number of bonding wires is generally greater than or equal to two. Therefore, to ensure bonding performance, the top view of both the first pad 251 and the second pad 252 is square. Figure 3 As shown, the side length s of the square is 100 μm or less.

[0071] Optionally, the top view of the first pad 251 and the second pad 252 can also be a rectangle, trapezoid, or rhombus shape, and the side length of any side of the top view of the first pad 251 and the second pad 252 is greater than or equal to 100μm.

[0072] It should be noted that the first metal layer 2 is symmetrically arranged with the center line of the short side of the ceramic substrate 1 as the axis of symmetry.

[0073] In some exemplary embodiments, the first metal layer 2 is further provided with a first metal sheet 281, a second metal sheet 282, a third metal sheet 283 and a fourth metal sheet 284, wherein the first metal sheet 281 and the second metal sheet 282 are respectively disposed on opposite sides of the first pad 251, and the third metal sheet 283 and the fourth metal sheet 284 are respectively disposed on opposite sides of the second pad 252;

[0074] The first metal sheet 281 has a first through hole 291 at its center, and the second metal sheet 282 has a second through hole 292 at its center. The first distance d1 between the center point of the first pad 251 and the center point of the first through hole 291 and the second distance d2 between the center point of the first pad 251 and the center point of the second through hole 292 are both less than 150μm, and the difference between the first distance d1 and the second distance d2 is less than or equal to 10μm.

[0075] The third metal sheet 283 has a third through hole 293 at its center, and the fourth metal sheet 284 has a fourth through hole 294 at its center. The third distance d3 between the center point of the second pad 252 and the center point of the third through hole 293, and the fourth distance d4 between the second pad 252 and the center of the fourth through hole 294 are both less than 150μm, and the difference between the third distance d3 and the fourth distance d4 is less than or equal to 10μm.

[0076] Please continue reading Figure 1 The first metal layer 2 is further provided with four metal plates. The first metal plate 281 and the second metal plate 282 are respectively disposed on opposite sides of the first pad 251, and located on opposite sides of the length extension direction of the input signal line. Similarly, the third metal plate 283 and the fourth metal plate 284 are respectively disposed on opposite sides of the second pad 252, and located on opposite sides of the length extension direction of the output signal line. That is, the first metal plate 281 and the third metal plate 283 are axially symmetrical, and the second metal plate 282 and the fourth metal layer are axially symmetrical. Each metal plate is provided with a through-hole penetrating the ceramic, namely the first through-hole 291, the second through-hole 292, the third through-hole 293, and the fourth through-hole 294.

[0077] In the embodiments of this application, such as Figure 3As shown, the distance between the center point of the first pad 251 and the center point of the first via 291 is defined as the first pitch d1; the distance between the center point of the first pad 251 and the center point of the second via 292 is defined as the second pitch d2; the distance between the center point of the second pad 252 and the center point of the third via 293 is defined as the third pitch d3; and the distance between the center point of the second pad 252 and the center point of the fourth via 294 is defined as the fourth pitch d4. All pitches d1, d2, d3, and d4 are set to be less than 150 μm, and the pitch difference between d1 and d2 is set to be less than or equal to 10 μm, and the pitch difference between d3 and d4 is set to be less than or equal to 10 μm. These settings ensure convenient contact between the probe and the bonding pad 25 for signal transmission or performance testing, and guarantee the performance of the gold wire bonding.

[0078] In some exemplary embodiments, the spacing between adjacent hairpin resonators in the resonator group 23 is a fifth spacing d5, the spacing between the input parallel coupling line 261 and the first-order hairpin resonator in the resonator group 23, and the spacing between the output parallel coupling line 262 and the last-order hairpin resonator in the resonator group 23 are all sixth spacing d6, the fifth spacing d5 is greater than or equal to the sixth spacing d6; the width and length of the input parallel coupling line 261 and the output parallel coupling line 262 are equal.

[0079] For example, setting the spacing between adjacent resonators to be greater than or equal to the spacing between the input / output parallel coupling line 262 and the resonators adjacent to the input / output parallel coupling line 262, i.e., setting the fifth spacing d5 to be greater than the sixth spacing d6, can improve signal transmission efficiency, reduce reflection loss, and achieve a narrower passband width and higher selectivity. At the same time, it can improve out-of-band rejection performance, and the coupling coefficient can be flexibly controlled by flexibly adjusting the spacing to optimize the filter performance.

[0080] Optionally, the length of the input parallel coupling line 261 is equal to the length of the first microstrip coupling line 231, and the width of the input parallel coupling line 261 is less than the width of the first microstrip coupling line 231.

[0081] For example, to achieve overall structural symmetry, the width and length of the input parallel coupling line 261 and the output parallel coupling line 262 are set to be equal; and the length L2 of the input parallel coupling line 261 is set to be equal to the length L1 of the first microstrip coupling line 231. This is because the coupling between the input parallel coupling line 261 and the resonator is mainly achieved through the interaction of electromagnetic fields. When the length L2 of the input parallel coupling line 261 is equal to the length L1 of the first microstrip coupling line 231, the electromagnetic field distribution in the coupling region is more uniform, thereby improving coupling efficiency. Furthermore, when the length of the input parallel coupling line 261 is equal to the length of the first microstrip coupling line 231, it helps to achieve good impedance matching at the resonant frequency. Impedance matching can reduce signal reflection and improve signal transmission efficiency. This design can also reduce parasitic capacitance and inductance generated during coupling, thereby reducing the influence of parasitic modes and improving filter performance.

[0082] Setting the width W2 of the input parallel coupling line 261 to be smaller than the width W1 of the first microstrip coupling line 231 can reduce the influence of high-frequency parasitic modes.

[0083] In some exemplary embodiments, the open-circuit stub 24 disposed on the signal input line 21 is a first open-circuit stub 241, and the open-circuit stub 24 disposed on the signal output line 22 is a second open-circuit stub 242.

[0084] The first open-circuit stub 241 and the second open-circuit stub 242 are axially symmetrical about the resonant group. The distance between the first open-circuit stub 241 and the input parallel coupling line 261 is the seventh distance d7, and the distance between the first open-circuit stub 241 and the first pad 251 is the eighth distance d8. The seventh distance d7 is greater than the eighth distance d8.

[0085] like Figure 3 As shown, the open-circuit stubs 24 on the input signal line and the output signal line are respectively called the first open-circuit stub 241 and the second open-circuit stub 242, and the first open-circuit stub 241 and the second open-circuit stub 242 are symmetrically arranged. The distance between the first open-circuit stub 241 and the input parallel coupling line 261 is the seventh distance d7, and the distance between the first open-circuit stub 241 and the first pad 251 is the eighth distance d8. The seventh distance d7 is designed to be greater than the eighth distance d8. This is because the farther the open-circuit stub 24 is from the bonding pad 25, the closer the frequency point of the filter outside the passband will be to the passband. This may cause additional resonance loss in the passband, thereby affecting the resonator performance. Therefore, designing the seventh distance d7 to be greater than the eighth distance d8 can keep the out-of-band resonance point away from the passband, reduce the influence of the out-of-band resonance point, thereby improving the filter's out-of-band suppression capability and preventing out-of-band signals from leaking into the passband.

[0086] Optionally, the width W3 of the open stub 241 and the second open stub 242 is greater than the width W1 of the microstrip coupling line 231.

[0087] The hairpin filter provided by this invention operates in the millimeter-wave band, specifically in the Ka-band. The Ka-band frequency range is 26.5 GHz - 40 GHz. The hairpin filter in the millimeter-wave band has advantages such as small size, high selectivity, and long parasitic passband, making it suitable for integrated applications. Furthermore, open-circuit stubs 24 are provided on the signal input line 21 and signal output line 22 to suppress parasitic passbands, meeting the current demand for high-performance, miniaturized filters in high-speed, high-frequency applications and demonstrating promising application prospects.

[0088] Optionally, the structure of the hairpin filter described above can also be applied to low-frequency hairpin filters, for example, those operating at frequencies between 0-30 GHz.

[0089] On the other hand, embodiments of this application provide an optical communication testing device, including the hairpin filter described above.

[0090] On the other hand, embodiments of this application also provide a communication device, including the hairpin filter described above.

[0091] On the other hand, embodiments of this application also provide a design method for a hairpin filter, including:

[0092] 1. Determine the parameters of the hairpin filter, including but not limited to operating frequency, center frequency, bandwidth (BW), in-band insertion loss, in-band return loss, out-of-band rejection, material of ceramic substrate 1, thickness of ceramic substrate 1, dielectric loss factor (Df) of ceramic substrate 1, dielectric constant (Dk) of ceramic substrate 1, material and fabrication process of metal layer, thickness of metal layer, and filter selection, etc.

[0093] 2. Calculate the theoretical parameters based on the selected filter, including key parameters such as order calculation, passband ripple, stopband attenuation, passband cutoff frequency, stopband cutoff frequency, group delay, insertion loss, return loss, bandwidth, and center frequency.

[0094] 3. The structure is modeled and simulated in HFSS (High Frequency Structure Simulator) based on theoretical parameters. An open stub 24 is added to both the signal input line 21 and the signal output line 22. The position and length of the stub are simulated to determine the actual parameters of the hairpin filter.

[0095] 4. Physical processing and testing: Based on the simulation, physical processing is carried out and testing is conducted to confirm whether the design requirements are met.

[0096] The design method and structure of the hairpin filter described above are illustrated below with a specific embodiment.

[0097] First, the filter's parameters include: the filter operates in the millimeter-wave band, Fc (center frequency) = 32GHz, BW = 3.4GHz, in-band insertion loss less than 2dB, in-band return loss required to be below -15dB, out-of-band (DC-28GHz, 34GHz-67GHz) suppression below 30dB. For miniaturization design requirements, the ceramic substrate 1 uses 996 alumina, Dk = 9.9, Df = 0.0002, thickness = 0.127mm, and the surface and back sides are sputtered using a nickel-palladium-gold process with a thickness of 4μm.

[0098] It should be noted that in-band insertion loss refers to the signal loss of a filter within its passband (i.e., the frequency range that the filter is designed to pass through). Ideally, in-band insertion loss should be as low as possible to minimize the attenuation of the useful signal. In-band return loss refers to the reflection loss of a filter within its passband, i.e., the proportion of the input signal reflected back to the signal source by the filter. The higher the return loss, the better the match between the filter and the signal source, and the less signal is reflected. Out-of-band rejection refers to the filter's ability to suppress unwanted signals within its stopband (i.e., the frequency range that the filter is designed to suppress). The higher the out-of-band rejection, the stronger the filter's ability to suppress unwanted frequency components, and the better it can prevent interference and noise.

[0099] To achieve miniaturization and high out-of-band rejection, a microstrip hairpin filter was chosen. The filter prototype adopted the Chebyshev type, which has good out-of-band rejection performance.

[0100] Secondly, in order to design a hairpin bandpass filter that meets the requirements, it is necessary to first perform the corresponding parameter calculations. The theoretical parameter calculation steps for a microstrip hairpin bandpass filter are as follows:

[0101] (1) According to the design requirements, a Chebyshev type bandpass filter is adopted, with Lar (ripple coefficient) = 0.1dB, ΩS (normalized stopband sideband) = 3.7, and Las (stopband attenuation) = 30dB. The order n of the Chebyshev type microstrip hairpin bandpass filter is calculated by the table lookup method. In order to reduce the volume and facilitate the design, the third order is adopted in this design.

[0102] (2) By looking up the table, the Chebyshev component values ​​are obtained as g1=1.1192, g2=1.1541, g1=g3=1.1192, where g1, g2 and g3 represent the normalized component values ​​of the third-order filter, which are used to design the specific circuit of the filter.

[0103] (3) The characteristic impedances of the odd-mode and even-mode coupling transmission lines in the bandpass filter are determined by the Chebyshev component values. The specific calculation formula is as follows:

[0104] Formula (1) is as follows:

[0105] ;

[0106] This formula calculates the normalized conductance J of the first-order coupling line (from 0 to 1). 0，1 Where Z0 is the characteristic impedance of the system, B w This is the bandwidth of the filter. g0 and g1 are the first two coefficients of the Chebyshev polynomial. g0 represents the normalized impedance at the input, which is 1 here. g1 is the normalized element value of the first-order filter.

[0107] Formula (2) is as follows:

[0108] ;

[0109] This formula calculates the normalized conductance J of the intermediate stage coupling line (i to i+1). i，i+1 , where i ranges from 1 to N-1, and N is the order of the filter.

[0110] Formula (3) is as follows:

[0111] ;

[0112] This formula calculates the normalized conductance J of the last stage of coupling (N to N+1). N，N+1 , This represents the normalized value of the Nth-order Chebyshev polynomial. Here, N is the order of the filter, i.e., the number of elements or stages in the filter. Chebyshev polynomials are not typically used directly in standard Chebyshev filter designs because they exceed the filter's order. However, in certain situations, particularly when designing more complex filter structures, higher-order Chebyshev polynomial values ​​may be required. In such cases, This could represent the normalized value of the next higher-order Chebyshev polynomial used in the design, or it could be a design parameter used to adjust specific characteristics of the filter. The setting here depends on the actual design.

[0113] Formula (4) is as follows:

[0114] ;

[0115] Formula (5) is as follows:

[0116] ;

[0117] In formulas (4) and (5), i = 0, 1, 2, ..., N. Formula (4) calculates the even-mode resistance. Formula (5) calculates the odd-mode impedance. Formulas (4) and (5) take into account the normalized conductance J. i，i+1 The effect of dual-mode impedance.

[0118] Then, the odd-mode and even-mode characteristic impedances of each order of the strip line can be calculated using formulas (1)-(5), as shown in Table 1.

[0119] Table 1. Odd and even mode impedance parameters of microstrip lines of various orders

[0120]

[0121] In the above table, Y O For characteristic admittance, The unit is Siemens.

[0122] (4) Use the Linear tool in ADS simulation software to calculate the geometric dimensions of the coupling lines corresponding to the odd and even mode impedances of each level: microstrip line width W, hairpin spacing S, and microstrip line length L, as shown in Table 2.

[0123] Table 2 Parallel coupling line parameters corresponding to odd and even mode impedances of microstrip lines of various orders

[0124]

[0125] It should be noted that in the simulation results, due to the even-mode impedance of the second-order and third-order filters... and odd-mode impedance Since they are consistent, the parameters of the third-order resonator are the same as those of the second-order resonator in the table. The table above lists the calculation results of the first-order and second-order resonators.

[0126] Third, the calculated parameters of each coupling line are used to draw the schematic diagram in ADS (Advanced Design System) and perform simulation. Then, a layout design is generated, and the DXF (Drawing Exchange Format) is exported to HFSS (High Frequency Structure Simulator) for modeling and simulation. Furthermore, quarter-wavelength open-circuit microstrip lines are added to signal input line 21 and signal output line 22 to obtain the following result: Figure 4 The design schematic is shown. The dimensions and odd / even mode impedances of each resonator in the schematic are consistent with those in Table 2.

[0127] It should be noted that the above simulation design process can be carried out using existing technologies.

[0128] Specifically, Figure 4 In the diagram, MLOC represents a microstrip line, Bend represents a bent structure, TL represents a transmission line, MTEE_ADS represents a T-type microstrip line assembly, Tee represents a T-type connector, Term represents a signal termination (i.e., signal input and signal output), MCFIL is a component used to represent a microstrip line coupling segment, Nμm refers to the component number, and subst="M Sub1" is used to specify the name of a replacement model or subcircuit. Referencing subcircuits or replacement models simplifies circuit design and improves design flexibility and maintainability. Correspondingly, the numbers after the components in the diagram (e.g., Bend1, Bend2) are merely codes for that component for easy identification and have no special meaning. Figure 4 In the diagram, the microstrip linewidth W of open-circuit stubs 24 (TL4, TL5) is 0.625 mm, and the microstrip line length L is 2.5 mm. The signal input line 21 and signal output line 22 have a width of 0.118 mm, and the input-coupled microstrip line and output-coupled microstrip line have W of 0.108 mm, S of 0.123 mm, and L of 0.915 mm. For detailed parameters, please refer to [link to relevant documentation]. Figure 4 This will not be elaborated upon here. However, Figure 4 Simulation tests were performed on the corresponding structure, and parameter scanning was conducted in HFSS to determine the optimal design scheme. The resulting simulation model is shown below. Figure 5 As shown, the specific dimensions of the model are as follows: Figure 6 As shown.

[0129] like Figure 6As shown, the designed hairpin filter includes a third-order resonator, an input parallel coupling line 261 parallel to the first microstrip coupling line 231 of the first-order resonator, an output parallel coupling line 262 parallel to the second microstrip coupling line 232 of the third-order resonator, a signal input line 21 with one end connected to the input parallel coupling line 261, the other end of the signal input line 21 connected to the bonding pad 25, a signal input line 21 with one end connected to the output parallel coupling line 262, and the other end of the signal output line 22 connected to the bonding pad 25. A first open-circuit stub 241 parallel to the input parallel coupling line 261 is provided on the signal input line 21, and a second open-circuit stub 242 parallel to the output parallel coupling line 262 is provided on the signal output line 22. The entire structure is symmetrically arranged with the second-order resonator as the axis of symmetry. The input parallel coupling line 261 and the first microstrip coupling line 231 of the first-order resonator form a first parallel coupling structure, the second microstrip coupling line 232 of the first-order resonator and the first microstrip coupling line 231 of the second-order resonator form a second parallel coupling structure, and so on, which will not be elaborated here.

[0130] Specifically, such as Figure 6As shown, the dimensions of each order resonator are completely identical. The microstrip linewidth of the first microstrip coupling line 231 and the second microstrip coupling line 232 is 0.117 mm and the microstrip line length is 0.460 mm. The microstrip linewidth of the microstrip line straight structure 235 is 0.050 mm and the microstrip line length is 0.600 mm. The spacing between adjacent hairpin resonators, i.e., the fifth spacing d5, is 0.060 mm. The spacing between the input parallel coupling line 261 and the first order hairpin resonator in the resonator group 23, and the spacing between the output parallel coupling line 262 and the... The spacing between the last-order hairpin resonators in resonator group 23, i.e., the sixth spacing d6, is 0.020 mm; the first open-circuit stub 241 is perpendicular to the signal input line 21, with a length of one-quarter wavelength, i.e., 0.441 mm, and a width of 0.122 mm; the microstrip linewidth of the input parallel coupling line 261 and the output parallel coupling line 262 is 0.094 mm, and the microstrip line length is 0.460 mm; the spacing between the first open-circuit stub 241 and the input parallel coupling line 261, i.e., the seventh spacing d7, is 0.440 mm. mm; the distance between the first open-circuit microstrip line and the first pad 251, i.e., the eighth distance d8, is 0.150 mm; the top view of the first pad 251 is a square with a side length of 0.150 mm; the top view of the first metal sheet 281 is a rectangle with a side length of 0.200 mm in the resonator arrangement direction and a side length of 0.350 mm in the direction perpendicular to the resonator arrangement direction; the structures of the second metal sheet 282, the third metal sheet 283, and the fourth metal sheet 284 are the same as those of the first metal sheet 281; the radius of the first via 291 is 0.050 mm; and the first distance d1, the second distance d2, the third distance d3, and the fourth distance d4 are all less than 150 μm, and the distance difference between the first distance d1 and the second distance d2 is less than or equal to 10 μm, and the distance difference between the third distance d3 and the fourth distance d4 is less than or equal to 10 μm.

[0131] Figure 7 The in-band return loss curve of the filter designed for simulation in the embodiments of this application is based on... Figure 7 A bandpass filter with a working bandwidth of 3.4 GHz and a center frequency of 32 GHz can be obtained, and its in-band return loss meets the requirement of being below -15 dB. Specifically, within the working bandwidth (29.90 GHz - 33.37 GHz), the in-band return loss is less than -15 dB.

[0132] Figure 8 The in-band insertion loss curve of the filter designed for simulation in the embodiments of this application is based on... Figure 8It can be seen that adding an open-circuit microstrip line to suppress parasitic passband does not affect the passband performance of the hairpin bandpass filter. The simulated design of a hairpin bandpass filter with a working bandwidth of 3.4 GHz and a center frequency of 32 GHz shows an in-band insertion loss of less than 2 dB (e.g., ...). Figure 8 As shown, the maximum in-band insertion loss is approximately -1.25dB, while the out-of-band (DC-28GHz, 34GHz-67GHz) suppression capability reaches 30dB. The filter's dimensions are only 4.5 mm × 1.5 mm.

[0133] Fourth, to ensure the accuracy and effectiveness of the design, the embodiments of this application have actually manufactured and tested the filter obtained from the simulation. To ensure the accuracy and effectiveness of the design, the embodiments of this application have manufactured and tested the filter obtained from the simulation, and its return loss curve is as follows: Figure 9 As shown, the insertion loss curve is as follows Figure 10 As shown in the analysis and test results, the bandpass filter with a working bandwidth of 3.4 GHz and a center frequency of 32 GHz meets the requirements for in-band return loss and has an in-band insertion loss of less than 2 dB (see [link to relevant documentation]). Figure 9 It effectively suppresses parasitic passbands below 67 GHz, achieving an out-of-band rejection of 36 dB, with an out-of-band rejection coverage up to 67 GHz, and good frequency selectivity. The filter measures only 4.5 mm × 1.5 mm.

[0134] It should be noted that the simulation results and actual results differ slightly due to factors such as manufacturing errors, but the overall performance of the filter meets the requirements, and the overall performance of the physical filter is basically consistent with the design. Figures 7-10 In the graph, the horizontal axis represents frequency, with the unit being GHz.

[0135] In summary, the hairpin filter provided in this application embodiment effectively suppresses the parasitic passband problem faced by traditional hairpin filters. This hairpin filter achieves parasitic passband suppression by adding an open-circuit stub 24 to both the signal input line 21 and the signal output line 22. Furthermore, the parallel coupling structure further miniaturizes the device, achieving a miniaturized design for the hairpin filter. By optimizing the structure of the signal input line 21 and the signal output line 22 and adding bonding pads 25, the hairpin filter can be applied to scenarios such as gold wire bonding, broadening the application range of hairpin resonators. The hairpin filter provided in this application embodiment has a simple structure, low design difficulty, and miniaturization characteristics, meeting the current demand for high-performance, miniaturized filters in the high-speed and high-frequency field, and demonstrating good application prospects.

[0136] The above description is only an optional embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A hairpin filter, comprising a ceramic substrate and a first metal layer located on one side surface of the ceramic substrate, the first metal layer having a signal input line, a resonator group, and a signal output line, the resonator group comprising at least two-order hairpin resonators, characterized in that, The first metal layer is also provided with open-circuit stubs and parallel coupling lines; The parallel coupling line transmits signals in a parallel coupling manner with the resonator group, including an input parallel coupling line and an output parallel coupling line respectively disposed on both sides of the resonator group; The open-circuit stub is disposed on the signal input line and on the signal output line, and the length of the open-circuit stub is between one-fifth and one-third of the wavelength.

2. The hairpin filter according to claim 1, characterized in that, The first metal layer is also provided with bonding pads; The bonding pads include a first pad and a second pad respectively disposed on both sides of the resonator group. The first pad is connected to the input parallel coupling line through the signal input line, and the second pad is connected to the output parallel coupling line through the signal output line.

3. The hairpin filter according to claim 2, characterized in that, The top view of the first pad and the second pad is a square, and the side length of the square is greater than or equal to 100 μm.

4. The hairpin filter according to claim 2, characterized in that, The first metal layer is further provided with a first metal sheet, a second metal sheet, a third metal sheet and a fourth metal sheet, wherein the first metal sheet and the second metal sheet are respectively disposed on opposite sides of the first pad, and the third metal sheet and the fourth metal sheet are respectively disposed on opposite sides of the second pad; The first metal sheet has a first through hole in its center, and the second metal sheet has a second through hole in its center. The first distance between the center point of the first pad and the center point of the first through hole and the second distance between the first pad and the center of the second through hole are both less than 150 μm, and the difference between the first distance and the second distance is less than or equal to 10 μm. The third metal sheet has a third through hole at its center, and the fourth metal sheet has a fourth through hole at its center. The third distance between the center point of the second pad and the center point of the third through hole, and the fourth distance between the second pad and the center of the fourth through hole are both less than 150 μm, and the difference between the third distance and the fourth distance is less than or equal to 10 μm.

5. The hairpin filter according to claim 1, characterized in that, The angle between the open stub and the input signal line is a first preset angle, and the angle between the open stub and the output signal line is a second preset angle; the range of both the first preset angle and the second preset angle is 45 degrees to 135 degrees.

6. The hairpin filter according to claim 1, characterized in that, The hairpin filter operates in the Ka band.

7. The hairpin filter according to claim 1, characterized in that, The spacing between adjacent hairpin resonators in the resonator group is the fifth spacing. The spacing between the input parallel coupling line and the first-order hairpin resonator in the resonator group, and the spacing between the output parallel coupling line and the last-order hairpin resonator in the resonator group are both the sixth spacing. The fifth spacing is greater than or equal to the sixth spacing. The width and length of the input parallel coupling line and the output parallel coupling line are equal.

8. The hairpin filter according to claim 2, characterized in that, The open-circuit stub set on the signal input line is the first open-circuit stub, and the open-circuit stub set on the signal output line is the second open-circuit stub. The first open-circuit stub and the second open-circuit stub are axially symmetrical about the resonant group, and the distance between the first open-circuit stub and the input parallel coupling line is the seventh distance, and the distance between the first open-circuit stub and the first pad is the eighth distance, wherein the seventh distance is greater than the eighth distance.

9. The hairpin filter according to claim 1, characterized in that, The hairpin filter further includes a second metal layer, which is disposed on the other side surface of the ceramic substrate and is disposed opposite to the first metal layer. The thickness of the ceramic substrate ranges from 0.12 mm to 0.4 mm.

10. An optical communication testing device, characterized in that, Includes the hairpin filter as described in any one of claims 1-9.

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