Electromagnetic hybrid coupling filter

Abstract

The invention relates to the technical field of radio frequency filters, and discloses an electromagnetic hybrid coupling filter. The filter is formed by stacking at least two spiral wiring resonators perpendicular to a winding plane, and comprises two input and output ports which are respectively connected with the first resonator and the last resonator. Each spiral wiring resonator is composed of at least two layers of metal spiral wiring, and the multiple layers of metal spiral wiring are sequentially connected through plated-through holes. The spiral wiring resonator is arranged in the insulating medium, and the resonant frequency of the spiral wiring resonator is determined by the length of the metal wiring and the dielectric constant of the dielectric material. Electric coupling and magnetic coupling exist between every two adjacent spiral wiring resonators at the same time, a transmission zero point can be generated outside a passband while a coupling signal forms the transmission passband, and the out-of-band rejection capacity is improved. The spiral wiring filter is compact and flexible in structure, can be realized by adopting various metal wiring processes, and can be independently made into a filter chip or directly wound in a circuit substrate of a radio frequency system to realize a filtering function.

Description

Technical Field

[0001] This invention relates to the field of radio frequency filter technology, and in particular to an electromagnetic hybrid coupling filter. Background Technology

[0002] Filters are crucial components in modern communication systems. With rapid societal development, the number of communication frequency bands in the same electronic communication products is increasing, while product size and weight are decreasing. This places higher demands on existing filters in terms of frequency selectivity and miniaturization. Electromagnetic hybrid coupling filters utilize the simultaneous electrical and magnetic coupling paths between adjacent resonators to generate transmission zeros outside the filter's passband, thus improving frequency selectivity. In particular, electromagnetic hybrid coupling filters implemented using multilayer metal wiring technologies such as LTCC exhibit a more compact λ / 4 resonator shape and a significantly smaller volume compared to electromagnetic hybrid coupling filters based on other technologies.

[0003] However, existing technologies for such filters have the following drawbacks: 1. They mostly use symmetrical structures, which are not flexible enough in design; 2. The resonators are relatively independent, which is not compact enough in structure; 3. The implementation process is simple and it is not convenient to integrate them according to the process characteristics of the RF system circuit board. Summary of the Invention

[0004] This invention provides an electromagnetic hybrid coupling filter to solve existing technical problems, addressing issues such as the relative independence of resonators, insufficient structural compactness, and the lack of design flexibility due to the prevalence of symmetrical structures in traditional filters.

[0005] To solve the above-mentioned technical problems, according to one aspect of the present invention, more specifically, an electromagnetic hybrid coupling filter is characterized by comprising: at least two spiral wired resonators stacked vertically on top of each other perpendicular to the plane of the winding layer; two input and output ports electrically connected to the first and last spiral wired resonators, respectively; a reference ground metal layer; and an insulating dielectric. The spiral wiring resonator is composed of at least two layers of metal spiral wiring and metallized vias.

[0006] Furthermore, the multiple metal spiral wiring layers are sequentially connected through metallized holes; the winding direction of the same spiral wiring resonator is the same in each part of different metal spiral wiring layers, and the winding direction of different spiral wiring resonators parallel to the winding plane is the same (clockwise or counterclockwise).

[0007] Furthermore, the two adjacent spiral wire resonators have opposite winding directions perpendicular to the winding plane (one upwards and the other downwards).

[0008] Furthermore, the metal materials used for each metal spiral wiring layer and metallized hole of the spiral wiring filter can be selected from gold, silver, copper or aluminum, depending on the different processing technology.

[0009] Furthermore, there is both electrical and magnetic coupling between two adjacent spiral wiring resonators; the end of the spiral wiring resonator electrically connected to the reference ground metal layer through the metal spiral wiring layer and the metallized via is the short-circuit end, and the end of the spiral wiring resonator away from the short-circuit end is the open-circuit end.

[0010] Furthermore, when the open terminals of two adjacent spiral wire resonators are close together, the electrical coupling is greater than the magnetic coupling, which will generate transmission zeros in the frequency range below the filter passband. When the short-circuit ends of two adjacent spiral wire resonators are close together, the magnetic coupling is greater than the electrical coupling, which will generate transmission zeros in the frequency range above the filter passband.

[0011] Furthermore, the reference ground metal layer is located below all the spiral wiring resonators, and the short-circuit terminals of each spiral wiring resonator are electrically connected to the reference ground metal layer through the metal spiral wiring layer and metallized vias.

[0012] Furthermore, each metal spiral wiring layer of the spiral wiring filter is covered with an insulating medium on both the top and bottom. The insulating medium can be made of any material selected from ceramic, resin, or glass, depending on the different processing techniques used.

[0013] The electromagnetic hybrid coupling filter provided by this invention has the following advantages compared to existing technologies: 1. The electromagnetic hybrid coupling filter in this invention adopts a structure of vertically stacked multi-layer spiral wiring resonators, which enables the resonators to be arranged in three dimensions within a finite plane, significantly improving the space utilization of the structure and helping to achieve the miniaturization and integration of the filter as a whole. It is suitable for modern communication equipment with strict size requirements.

[0014] 2. By flexibly configuring the winding direction between adjacent spiral wiring resonators and the relative positions of their open and short-circuit ends, this invention can independently control the ratio of electrical and magnetic coupling strength, thereby precisely introducing transmission zeros above or below the passband, enhancing the frequency selectivity and out-of-band rejection capability of the filter, and meeting the high-performance filtering requirements of multi-band communication systems.

[0015] 3. The filter in this invention supports the selection of various metal materials and dielectric materials, and can adapt to different process technologies such as LTCC and multilayer PCB, demonstrating good process compatibility and design flexibility, which facilitates customized design and manufacturing according to specific RF system architecture, cost control and performance indicators.

[0016] 4. The spiral wiring resonator in this invention is constructed by connecting multiple layers of metal spiral wiring layers in series with metallized vias, which effectively extends the resonant electrical length. While maintaining a low resonant frequency, it significantly reduces the planar area occupied, making it particularly suitable for low-frequency and narrow-band filtering scenarios, and also beneficial for embedded integration in various RF modules.

[0017] 5. This invention introduces an optional magnetic coupling short-circuit structure, which can specifically enhance the magnetic coupling strength between adjacent resonators without significantly increasing the volume. This further expands the tuning freedom and performance optimization space of the filter, enabling designers to adjust the filter response more precisely and adapt to complex application environments. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the electromagnetic hybrid coupling filter in this invention; Figure 2 This is a schematic diagram of the stacked spiral wiring resonator in this invention; Figure 3 This is a schematic diagram of the spiral wiring resonator structure in this invention; Figure 4 This is a schematic diagram of the magnetic coupling short-circuit connection structure in this invention; Figure 5 This is a schematic diagram of the structure of Embodiment 1 of the present invention; Figure 6 This is the radio frequency performance curve of Embodiment 1 in this invention; Figure 7 This is a schematic diagram of the structure of Embodiment 2 of the present invention; Figure 8 This is the radio frequency performance curve of Embodiment 2 in this invention; Figure 9 This is a schematic diagram of the structure of Embodiment 3 of the present invention; Figure 10 This is the radio frequency performance curve of Embodiment 3 in this invention; Figure 11 This is a schematic diagram of the circuit board structure applied to the radio frequency system in Embodiment 4 of the present invention; Figure 12 This is a schematic diagram of the circuit board structure applied to the radio frequency system in Embodiment 5 of the present invention.

[0019] In the diagram: 1. Spiral wiring resonator; 2. Input / output port; 3. Reference ground metal layer; 4. Insulating dielectric; 5. Metal spiral wiring layer; 6. Metallized via; 7. Magnetic coupling short-circuit structure; 8. Open circuit terminal; 9. Short-circuit terminal. Detailed Implementation

[0020] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] like Figure 1 As shown, an electromagnetic hybrid coupling filter includes: a spiral wiring resonator 1; an input / output port 2; a reference ground metal layer 3; and an insulating medium 4.

[0022] like Figure 2 As shown, multiple spiral wiring resonators 1, each composed of multiple layers of metal spiral wiring layers 5, are stacked vertically from top to bottom on the winding layer plane. The winding directions of different spiral wiring resonators 1 are the same (clockwise or counterclockwise) parallel to the winding plane, and the winding directions of two adjacent spiral wiring resonators 1 are opposite (one facing up and the other facing down).

[0023] like Figure 3 As shown, each spiral wiring resonator 1 consists of at least two layers of metal spiral wiring 5, which are sequentially connected through metallized vias 6. The number of turns of the spiral wire in the same metal spiral wiring layer 5 can be greater than one, and the winding direction of the same spiral wiring resonator 1 is the same in different parts of different metal spiral wiring layers 5. One end of the spiral wiring resonator 1 is open-circuited, and the other end is electrically connected to the reference ground metal layer 3 through the metal spiral wiring layer 5 and the metallized via 6.

[0024] Based on transmission line theory, the resonant frequency of the spiral wiring resonator 1 can be calculated. Typically, the resonant frequency of the spiral wiring resonator 1 is inversely proportional to the spiral wiring length in the metal spiral wiring layer 5 and inversely proportional to the dielectric constant of the insulating medium.

[0025] According to electromagnetic field theory, both electrical and magnetic coupling exist between the two stacked spiral wire resonators 1. When the electrical coupling is greater than the magnetic coupling, a transmission zero will be generated in the frequency range below the filter passband; when the magnetic coupling is greater than the electrical coupling, a transmission zero will be generated in the frequency range above the filter passband. The greater the difference between the two couplings, the wider the coupling bandwidth, and vice versa; the closer the ratio of the two couplings is to 1, the closer the distance between the transmission zero and the transmission passband, and vice versa.

[0026] According to transmission line theory, the electric field strength at the open end 8 of the λ / 4 resonator is relatively high, and the magnetic field strength at the short end 9 is relatively high. By adjusting the facing area and distance of the wiring at the open end 8 of the two spiral wiring resonators 1, the electric coupling strength can be changed. By adjusting the number of turns and distance of the wiring at the short end 9 of the two spiral wiring resonators 1, the magnetic coupling strength can be changed.

[0027] Based on the above theoretical analysis, it can be concluded that Figure 2 The close proximity of the open terminals 8 of the top spiral wiring resonator 1 and the middle spiral wiring resonator 1 will generate transmission zeros in the frequency range below the filter passband. Figure 2The short-circuit ends of the middle spiral wiring resonator 1 and the bottom spiral wiring resonator 1 are close together, which will generate transmission zeros in the frequency range above the filter passband.

[0028] like Figure 4 As shown, the magnetic coupling strength can be improved by adding a magnetically coupled short-circuit structure near the short-circuit end 9 of the two spiral wired resonators 1. The magnetically coupled short-circuit structure 7 is implemented by a metal wiring layer and metallized vias, and its two ends are connected to the two spiral wired resonators 1 respectively. The farther the connection point is from the short-circuit end 9 of the spiral wired resonator, the greater the increase in magnetic coupling strength. The magnetically coupled short-circuit structure can be placed in the area without metal wiring in the middle of the spiral wired resonator 1, or it can be placed on the outside of the spiral wired resonator.

[0029] like Figure 1 As shown, the two input and output ports are electrically connected to the first and last spiral wire resonators 1, respectively. According to electromagnetic field theory, the closer the connection point is to the open end 8 of the spiral wire resonator 1, the larger the external coupling coefficient is; conversely, the closer the connection point is to the short end 9 of the spiral wire resonator 1, the smaller the external coupling coefficient is.

[0030] The number and oscillation frequency of helical wire resonators in an electromagnetic hybrid coupling filter, as well as the strength of electromagnetic hybrid coupling between adjacent helical wire resonators and the number and location of the generated transmission zeros, all affect the filter's performance indicators and can be adjusted and optimized according to relevant filter design theories.

[0031] like Figure 1 As shown, the reference ground metal layer 3 is typically located below all spiral wiring resonators 1, and the short-circuit terminal 9 of each spiral wiring resonator 1 is electrically connected to the reference ground metal layer 3 through the metal wiring layer 5 and the metallized via 6.

[0032] The choice of metal and insulating dielectric materials is related to the processing technology. For example, in multilayer substrate processes, copper is often used as the metal and resin as the insulating dielectric; in LTCC processes, silver is often used as the metal and ceramic as the insulating dielectric. Different processing technologies have different processing precision, cost, and shape characteristics, and the selection should be based on the actual requirements.

[0033] According to electromagnetic field theory, the Q value of a spiral wire resonator is proportional to the thickness of the metal layer, the thickness of the insulating dielectric material between adjacent metal layers, and the width of the spiral wire. In general, appropriate process parameters should be selected in combination with the manufacturing process capability to maximize the Q value of the spiral wire resonator and thus reduce the filter loss.

[0034] Example 1 like Figure 5As shown, an electromagnetic hybrid coupling filter includes two spiral wire resonators 1; two input / output ports 2; a reference ground metal layer 3 and an insulating medium 4.

[0035] This embodiment is implemented using a 10-layer LTCC process.

[0036] Both the upper spiral wire resonator 1 and the lower spiral wire resonator 1 are composed of three layers of metal spiral wires.

[0037] Both spiral wiring resonators 1 have metal wiring layers 5 wound in a counterclockwise direction.

[0038] The upper spiral wire resonator 1 is perpendicular to the winding plane and points downwards, while the lower spiral wire resonator 1 is perpendicular to the winding plane and points upwards.

[0039] The two input / output ports are located at the bottom layer and are connected to the upper spiral wiring resonator 1 and the lower spiral wiring resonator 1 respectively through the metal wiring layer and metallized via.

[0040] The open-circuit terminals 8 of the upper and lower spiral resonators 1 are close together, resulting in a higher electrical coupling strength than magnetic coupling strength. This leads to a transmission zero frequency lower than the transmission passband, achieving out-of-band rejection of over 30dB in the 0–2.7GHz frequency range. Figure 6 As shown.

[0041] The metal material used for each metal wiring layer and metallized via is silver, with a thickness of 10um.

[0042] The insulating dielectric material is resin, the thickness of the metal layers is 50 μm, and the dielectric constant is 7.8.

[0043] Example 2 like Figure 7 As shown, an electromagnetic hybrid coupling filter includes two helical wiring resonators 1; two input / output ports 2; a magnetically coupled short-circuit structure 7; a reference ground metal layer 3; and an insulating medium 4.

[0044] This embodiment is implemented using a 10-layer LTCC process.

[0045] The upper spiral wire resonator 1 is composed of four layers of metal spiral wires 5, and the lower spiral wire resonator 1 is composed of three layers of metal spiral wires 5.

[0046] Both spiral wiring resonators 1 have metal wiring layers 5 wound in a counterclockwise direction.

[0047] The upper spiral wire resonator 1 is perpendicular to the winding plane and the winding direction is upward, while the lower spiral wire resonator 1 is perpendicular to the winding plane and the winding direction is downward.

[0048] The two input / output ports are located at the bottom layer and are connected to the upper spiral wiring resonator 1 and the lower spiral wiring resonator 1 respectively through the metal wiring layer and metallized via.

[0049] The short-circuit terminals 9 of the upper and lower spiral wiring resonators 1 are close to each other, and a magnetic coupling short-circuit structure is set near the short-circuit terminals 9 of the two spiral wiring resonators 1. The magnetic coupling strength is greater than the electrical coupling strength, resulting in a transmission zero-point frequency higher than the transmission passband, achieving out-of-band rejection of more than 30dB in the frequency range of 6.5~8GHz. Figure 8 As shown.

[0050] The metal material used for each metal wiring layer and metallized via is silver, with a thickness of 10um.

[0051] The insulating dielectric material is resin, the thickness of the metal layers is 50 μm, and the dielectric constant is 7.8.

[0052] Example 3 like Figure 9 As shown, an electromagnetic hybrid coupling filter includes three helical wiring resonators 1; two input / output ports 2; a magnetically coupled short-circuit structure 7; a reference ground metal layer 3; and an insulating medium 4.

[0053] This embodiment is implemented using a 10-layer substrate process.

[0054] The upper spiral wire resonator 1 and the middle spiral wire resonator 1 are both composed of three layers of metal spiral wires 5, while the lower spiral wire resonator 1 is composed of two layers of metal spiral wires 5.

[0055] The three spiral wiring resonators 1 have metal wiring layers wound in a counterclockwise direction.

[0056] The upper and lower spiral wire resonators 1 are perpendicular to the winding plane and the winding direction is downward, while the middle spiral wire resonator 1 is perpendicular to the winding plane and the winding direction is upward.

[0057] Two input / output ports 2 are located at the bottom layer and are connected to the upper spiral wiring resonator 1 and the lower spiral wiring resonator 1 respectively through a metal wiring layer and a metallized via.

[0058] The open-circuit terminals 8 of the upper spiral resonator 1 and the middle spiral resonator 1 are close together, resulting in a stronger electrical coupling than magnetic coupling. This leads to a transmission zero-point frequency lower than the transmission passband, achieving out-of-band rejection of over 25 dB in the 0–2.7 GHz frequency range. Figure 10 As shown.

[0059] The short-circuit ends of the middle spiral wiring resonator 1 and the lower spiral wiring resonator 1 are close to each other, and a magnetic coupling short-circuit structure is set near the short-circuit ends of the two spiral wiring resonators. The magnetic coupling strength is greater than the electrical coupling strength, and the resulting transmission zero-point frequency is higher than the transmission passband, achieving out-of-band rejection of more than 30dB in the frequency range of 9.5~18GHz. Figure 10 As shown.

[0060] The metal material used for each metal wiring layer and metallized via is copper, with a thickness of 15um.

[0061] The insulating dielectric material is resin, the thickness of the metal layers is 25 μm, and the dielectric constant is 4.4.

[0062] Example 4 like Figure 11 As shown, an electromagnetic hybrid coupling filter is assembled as a separate chip along with other chips on a radio frequency system circuit board.

[0063] Example 5 like Figure 12 As shown, an electromagnetic hybrid coupling filter is implemented by substrate metal wiring and integrated into the radio frequency system circuit substrate.

[0064] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. An electromagnetic hybrid coupling filter, characterized in that, include: At least two spiral wire resonators (1) are stacked vertically on top of each other perpendicular to the plane of the winding layer; Two input / output ports (2) are electrically connected to the first and last spiral wiring resonators (1) respectively; reference ground metal layer (3); insulating medium (4); The spiral wiring resonator (1) is composed of at least two metal spiral wiring layers (5) and metallized holes (6).

2. The electromagnetic hybrid coupling filter according to claim 1, characterized in that: The multilayer metal spiral wiring layers (5) are connected sequentially through metallized holes (6); the same spiral wiring resonator (1) has the same winding direction in each part of different metal spiral wiring layers (5), and different spiral wiring resonators (1) have the same winding direction parallel to the winding plane.

3. The electromagnetic hybrid coupling filter according to claim 1, characterized in that: The two adjacent spiral wire resonators (1) have opposite winding directions perpendicular to the winding plane.

4. The electromagnetic hybrid coupling filter according to claim 2, characterized in that: The metal materials used for each metal spiral wiring layer (5) and metallized hole (6) of the spiral wiring filter (1) can be selected from gold, silver, copper or aluminum depending on the different processing technology.

5. The electromagnetic hybrid coupling filter according to claim 1, characterized in that: There are both electrical and magnetic coupling between two adjacent spiral wiring resonators (1); one end of the spiral wiring resonator (1) that is electrically connected to the reference ground metal layer (3) through the metal spiral wiring layer (5) and the metallized hole (6) is the short-circuit end (9), and the other end of the spiral wiring resonator (1) that is away from the short-circuit end (9) is the open-circuit end (8).

6. The electromagnetic hybrid coupling filter according to claim 5, characterized in that: When the open terminals (8) of two adjacent spiral wire resonators (1) are close together, the electrical coupling is greater than the magnetic coupling, which will generate transmission zeros in the frequency range below the filter passband. When the short-circuit terminals (9) of two adjacent spiral wire resonators (1) are close together, the magnetic coupling is greater than the electrical coupling, which will generate transmission zeros in the frequency range above the filter passband.

7. The electromagnetic hybrid coupling filter according to claim 2, characterized in that: The reference ground metal layer (3) is located below all the spiral wiring resonators (1), and the short-circuit terminal (9) of each of the spiral wiring resonators (1) is electrically connected to the reference ground metal layer (3) through the metal spiral wiring layer (5) and the metallized via (6).

8. The electromagnetic hybrid coupling filter according to claim 7, characterized in that: The spiral wiring filter (1) has an insulating medium (4) covering both the top and bottom of each metal spiral wiring layer (5). The insulating medium (4) can be made of any one of ceramic, resin or glass depending on the different processing technology.

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