TWI875147B - Filter and circuit element - Google Patents

Abstract

A filter is disposed on a circuit board and includes a first coupling line, a second coupling line, a closed line, at least one ground plane and at least one ground via. The closed line includes a first coupling portion and a second coupling portion. The first coupling line, the second coupling line and the closed line are all located on a conductive layer of the circuit board. The first coupling line and the second coupling line are respectively parallel to the first coupling portion and the second coupling portion, and the first coupling line and the second coupling line are coupled to the closed line. The at least one ground plane is located on another conductive layer of the circuit board, and the at least one ground via is connected between the closed line and the at least one ground plane. Therefore, it is advantageous in expanding the operating bandwidth.

Description

Filters and circuit components

The present disclosure relates to a filter and a circuit element, and in particular to a filter and a circuit element disposed on a circuit board.

Driven by the pursuit of a more convenient life, a variety of wireless communication systems and their RF technologies have been developed. For example, with the rise of 5G millimeter wave (mmWave) technology in recent years, more and more consumer electronic products are equipped with this technology, and terminal products are constantly updated, which means that the development and manufacturing costs and design complexity of wireless communication modules and their components will increase accordingly. For example, 5G millimeter wave communication modules usually require a very small size, so some RF circuit components (such as filters) that occupy volume or area in existing technologies will not be applicable to 5G millimeter wave communication modules.

In view of this, how to reduce the size, cost and design complexity of circuit components such as filters in wireless communication modules, while meeting the RF characteristics requirements of wireless communication systems and further making the products more market-advantaged, has become a topic of concern in the market.

The present disclosure provides a filter and a circuit element, which are arranged on a circuit board and include a first coupling line, a second coupling line, a closed line, at least one ground plane and at least one ground through hole. The closed line is coupled through the first coupling line and the second coupling line, and the at least one ground through hole is connected between the closed line and the at least one ground plane to reduce the cost and the volume occupied. The ground through hole is used to generate a ground path so that a low-frequency mode is generated near the resonance frequency of the closed line, thereby achieving a dual-mode effect to expand the operating bandwidth.

According to an embodiment of the present disclosure, a filter is provided, which is arranged on a circuit board and includes a first coupling line, a second coupling line, a closed line, at least one ground plane and at least one ground through hole. The first coupling line is connected to a first feeding point, and the second coupling line is connected to a second feeding point. The closed line includes a first coupling portion and a second coupling portion, and the first coupling line, the second coupling line and the closed line are all located on a conductive layer of the circuit board, the first coupling line and the second coupling line are respectively parallel to the first coupling portion and the second coupling portion, and the first coupling line and the second coupling line are coupled to the closed line. The at least one ground plane is located on another conductive layer of the circuit board, and the at least one ground plane is a reference ground for the first coupling line, the second coupling line and the closed line. The at least one ground through hole is connected between the closed line and the at least one ground plane.

According to another embodiment of the present disclosure, a circuit element is provided, which is arranged on a circuit board and includes a first coupling line, a second coupling line, a closed line, at least one ground plane and at least one ground through hole. The first coupling line extends from a first feeding point in two directions with equal lengths, and the second coupling line extends from a second feeding point in two directions with equal lengths. The closed line includes a first coupling portion and a second coupling portion, and the first coupling line, the second coupling line and the closed line are all located on a conductive layer of the circuit board, the first coupling line and the second coupling line are respectively parallel to the first coupling portion and the second coupling portion, and the first coupling line and the second coupling line are coupled to the closed line. The at least one ground plane is located on another conductive layer of the circuit board, and the at least one ground plane is a reference ground for the first coupling line, the second coupling line and the closed line. The at least one grounding via is connected between the closing line and the at least one grounding plane, and the at least one grounding via divides the closing line into a plurality of regions with equal paths.

FIG. 1A shows a perspective view of a filter 100 according to the first embodiment of the present disclosure, and FIG. 1B shows a top view of a conductive layer 102 of the filter 100 in FIG. 1A. Referring to FIG. 1A and FIG. 1B, the circuit element according to the first embodiment of the present disclosure is specifically a filter 100. The filter 100 is disposed on a circuit board 108 and includes a first coupling line 120, a second coupling line 160, a closing line 130, at least one ground plane (not separately labeled) and a ground via 180. The circuit board 108 specifically includes conductive layers 101, 102, and 103 in order from top to bottom in FIG. 1A.

The first coupling line 120 is connected to the first feeding point 119, and the second coupling line 160 is connected to the second feeding point 179. The closed line 130 includes a first coupling portion 131 and a second coupling portion 132. The first coupling line 120, the second coupling line 160 and the closed line 130 are all located on the conductive layer 102 of the circuit board 108. The first coupling line 120 and the second coupling line 160 are respectively parallel to the first coupling portion 131 and the second coupling portion 132 (i.e., they maintain the same distance as the first coupling portion 131 and the second coupling portion 132). The first coupling line 120 and the second coupling line 160 couple the closed line 130. The at least one ground plane is located on the conductive layers 101 and 103 of the circuit board 108. The ground planes located on the conductive layers 101 and 103 are reference grounds for the first coupling line 120, the second coupling line 160 and the closed line 130. The ground via 180 is connected between the closed line 130 and the ground planes located on the conductive layers 101 and 103. In this way, the filter 100 is designed as a planar band pass filter (BPF) using the circuit board 108 without using discrete components, thereby reducing costs and occupied volume. Furthermore, by using the grounding via 180 to generate a grounding path, a low-frequency mode (such as the frequency 37.40 GHz corresponding to the point m1 in FIG. 1C ) is generated adjacent to the resonance frequency of the closed line 130 (such as the frequency 39.70 GHz corresponding to the point m2 in FIG. 1C ), thereby achieving a dual-mode effect to expand the operating (application) bandwidth.

In addition, each of the first coupling line 120, the second coupling line 160 and the closed line 130 of the filter 100 is specifically a stripline, and it should be understood that the transmission line type of the first feed line, the second feed line, the first coupling line, the second coupling line and the closed line of the filter according to the present disclosure can also be a microstrip line and is not limited to the first to third embodiments. Furthermore, the circuit element according to other embodiments of the present disclosure can be specifically a filter or a circuit element including a filtering feature, such as a diplexer. The shape and size of the circuit board are not limited to the drawings in the present disclosure. The circuit board can be a printed circuit board, a flexible circuit board or a circuit substrate of other dielectric materials, but is not limited thereto. In addition, the “connection” described in the present disclosure refers to a physical connection between two components and is either a direct connection or an indirect connection, while the “coupling” described in the present disclosure refers to two components being separated from each other and not physically connected, and the electric field energy (Electric Field Energy) generated by the current of one component excites the electric field energy of another component.

In detail, the closed line 130 specifically includes a first annular area 141 and a second annular area 142, both of which are closed annular shapes. The first coupling portion 131 and the second coupling portion 132 are respectively located in the first annular area 141 and the second annular area 142. The first annular area 141 and the second annular area 142 are connected to the intersection 143, and the grounding via 180 is connected to the intersection 143. Thus, the filter 100 has a grounding through hole 180 at the intersection 143 at the center of the structure, which is grounded to the upper and lower conductive layers 101 and 103. By using the grounding through hole 180 to generate a grounding path, the filter 100 generates a low-frequency mode adjacent to the resonance frequency of the ring structure of the original closed line 130, thereby achieving a dual-mode effect to expand the operating bandwidth. Furthermore, more than two grounding through holes can be specifically set on the intersection of the filter according to the present disclosure, so as to further expand the operating bandwidth while meeting the characteristic requirements of the single-passband dual-mode 3dB bandwidth.

The closed line 130 is in a "sun" shape, specifically in an 8-shape, and the path length of the first annular region 141 is equal to the path length of the second annular region 142, wherein the path length described in the present disclosure refers to the center path length. Furthermore, a grounding via 180 divides the closed line 130 into two regions with equal path lengths (i.e., the first annular region 141 and the second annular region 142), and the first coupling portion 131 and the second coupling portion 132 are respectively located in the first annular region 141 and the second annular region 142. Thus, the filter 100 has a simple resonant structure, which is beneficial to reduce the design complexity, and can achieve a dual-mode effect without multiple structures being connected in series.

The first coupling line 120 extends from the first feeding point 119 in two directions (i.e., the upper and lower directions in FIG. 1B ) with equal lengths, and the second coupling line 160 extends from the second feeding point 179 in two directions with equal lengths, that is, each of the first coupling line 120 and the second coupling line 160 forms a coupling arm or a feeding arm structure. Thus, an appropriate feeding method can effectively excite the dual-mode resonance of the filter 100, thereby avoiding the complex structure, large size and high cost of connecting multiple structures in series or using discrete elements.

The path length of the first coupling line 120 and the path length of the second coupling line 160 are equal, and the ratio of the path length of the closed line 130 to the path length of the first coupling line 120 may be between 2.2 and 20. Furthermore, the ratio may be between 2.5 and 4.5. In this way, the filter 100 can reduce the structure volume by not using discrete elements, so as to be suitable for millimeter wave wireless communication modules. In the first embodiment, the path length of the closed line 130 is 4168 um (Micrometer), and the path length of the first coupling line 120 is 1164 um, so the ratio is 3.58.

The filter 100 may further include a first feed line 110 and a second feed line 170, both of which are located in the conductive layer 102. Each of the first feed line 110, the second feed line 170, the first coupling portion 131 and the second coupling portion 132 may be a 50 ohm strip line. The first feed point 119 is connected between the first feed line 110 and the first coupling line 120. The second feed point 179 is connected between the second feed line 170 and the second coupling line 160. The first feed line 110 and the second feed line 170 are both arranged along a virtual transverse axis (also known as a transverse plane) p. Thus, the planar design of the filter 100 helps to reduce the structural volume. Furthermore, the first feed line and the second feed line of the filter according to the present disclosure may be connected to the first coupling line and the second coupling line by vias and located in different conductive layers. In addition, a plurality of ground vias 189 may be disposed on the inner side of each of the first annular region 141 and the second annular region 142, and a plurality of ground vias 188 may be disposed along the two sides or around the filter 100, and the arrangement of the ground vias 188 and 189 is not limited to FIG. 1A and FIG. 1B, so as to reduce the interference of the characteristics of the filter 100 by the adjacent circuits or electromagnetic waves and provide grounding integrity.

Specifically, the filter 100 is symmetrical about the transverse axis p and the virtual longitudinal axis (also called the longitudinal plane) q, and the transverse axis p and the longitudinal axis q are perpendicular to each other. This helps to reduce the complexity of the design.

Referring to FIG. 1B , there is a distance g23 between the first coupling line 120 and the first coupling portion 131, and the ratio of the width w2 of the first coupling line 120 to the width w3 of the closing line 130 may be between 0.2 and 5, and the ratio of the width w2 of the first coupling line 120 to the distance g23 may be between 0.25 and 3. Furthermore, the ratio of the width w2 of the first coupling line 120 to the width w3 of the closing line 130 may be between 0.3 and 2. In addition, the ratio of the width w2 of the first coupling line 120 to the distance g23 may be between 0.4 and 2.25. In this way, a dual-mode filter 100 can be effectively realized to meet the application requirements of wide operating bandwidth such as 5G millimeter wave communication modules. In the first embodiment, the ratio of the width w2 (30 um) of the first coupling line 120 to the width w3 (62 um) of the closed line 130 is 0.48, and the ratio of the width w2 of the first coupling line 120 to the spacing g23 (30 um) is 1.

FIG. 1C is a schematic diagram showing the S parameters of the filter 100 in FIG. 1A , wherein the first measuring port and the second measuring port for measuring the S parameters in the figure can be respectively disposed at the positions of the first feeding line 110 and the second feeding line 170 at the edge of the circuit board 108 . Please refer to FIG. 1C . The 3dB bandwidth of the filter 100 defined by the S21 parameter is 37.00 GHz to 40.25 GHz, so it is applicable to the current 5G millimeter wave band. The S11 and S22 parameters within the 3dB bandwidth are both less than -10 dB and exhibit dual modes. The marking point m1 of the S11 parameter is 37.40 GHz and -16.34 dB, and the marking point m2 of the S11 parameter is 39.70 GHz and -17.48 dB. It can be seen that the filter 100 has two resonant frequencies of 37.40 GHz and 39.70 GHz, and the corresponding frequency of the S parameter extreme value within the 3dB bandwidth of the filter 100 can be defined as the resonant frequency.

The ratio of the sum of the path length of the first annular region 141 and the path length of the second annular region 142 (i.e., the path length of the 8-shaped closed line 130 including the intersection 143) to the effective wavelength of each of the resonance frequencies 37.40 GHz and 39.70 GHz of the filter 100 on the circuit board 108 may be between 0.8 and 1.1. Furthermore, the ratio may be between 0.9 and 1.05. Thus, when the wavelength of the input signal matches the loop path length of the closed line 130, a higher frequency of the two resonance frequencies in the dual mode is generated, and the grounding path is generated by the grounding via 180 to generate a low frequency mode adjacent to the higher frequency resonance frequency, thereby achieving a dual mode effect. In the first embodiment, the path length of the closed line 130 is 4168 um, and the effective wavelengths of the two resonance frequencies 37.40 GHz and 39.70 GHz of the filter 100 on the circuit board 108 are approximately 4424 um and 4168 um, respectively, so their ratios are 0.94 and 1, respectively.

FIG. 1D shows a schematic diagram of the surface current density of another filter and the filter 100 in FIG. 1A, wherein FIG. 1D (a) shows the surface current density of another filter (not shown) without the grounding via 180, and FIG. 1D (b) and (c) show the surface current density of the filter 100 according to the present disclosure, and the structural edge lines of the filter 100 in FIG. 1D are only schematic edges and are not used to indicate the size of the surface current density. Please refer to FIG. 1B to FIG. 1D, when the difference between the other filter and the filter 100 is that the grounding via 180 is not provided, the surface current density at a frequency of 37.4 GHz is as shown in FIG. 1D (a), and the excitation current on the closed line is very small, that is, no resonance occurs. On the contrary, the surface current density of the filter 100 according to the present disclosure at 37.4 GHz and 39.7 GHz is shown in Figure 1D (b) and (c) respectively, indicating that the current distribution on the closed line 130 is concentrated at both the low frequency 37.4 GHz and the high frequency 39.7 GHz, that is, the filter 100 generates a resonant frequency, wherein Figure 1D (b) shows that an exciting current occurs at 37.4 GHz, which is lower than 39.7 GHz, that is, the resonance generates an adjacent mode with a lower frequency, and as shown in the S parameters of the dual modes in Figure 1C, the filter 100 is specifically suitable for today's 5G millimeter wave products and can expand the operating bandwidth. Furthermore, in FIG. 1B of the first embodiment, the distance between the first feed point 119 and the second feed point 179 is 1686 um, and the distance between the two ends of the first coupling line 120 parallel to the longitudinal axis q is 756 um, so the filter 100 has sufficiently small length and width dimensions to be suitable for 5G millimeter wave products.

FIG. 2A shows a perspective view of a filter 200 according to a second embodiment of the present disclosure, and FIG. 2B shows a top view of a conductive layer 202 of the filter 200 in FIG. 2A. Referring to FIG. 2A and FIG. 2B, the circuit element according to the second embodiment of the present disclosure is specifically a filter 200. The filter 200 is disposed on a circuit board 208 and includes a first coupling line 220, a second coupling line 260, a closing line 230, at least one ground plane (not separately labeled) and a ground through hole 280. The circuit board 208 specifically includes conductive layers 201, 202, and 203 in order from top to bottom in FIG. 2A.

The first coupling line 220 is connected to the first feeding point 219, and the second coupling line 260 is connected to the second feeding point 279. The closed line 230 includes a first coupling portion 231 and a second coupling portion 232. The first coupling line 220, the second coupling line 260 and the closed line 230 are all located on the conductive layer 202 of the circuit board 208 and are specifically strip lines. The first coupling line 220 and the second coupling line 260 are parallel to the first coupling portion 231 and the second coupling portion 232, respectively. The first coupling line 220 and the second coupling line 260 couple the closed line 230. The at least one ground plane is located on the conductive layers 201 and 203 of the circuit board 208 . The ground planes on the conductive layers 201 and 203 are reference grounds for the first coupling line 220 , the second coupling line 260 and the closing line 230 . The ground via 280 is connected between the closing line 230 and the ground planes on the conductive layers 201 and 203 .

Specifically, the closed line 230 includes a first annular area 241 and a second annular area 242, both of which are closed annular shapes. The first coupling portion 231 and the second coupling portion 232 are located in the first annular area 241 and the second annular area 242, respectively. The first annular area 241 and the second annular area 242 are connected to the intersection 243, and the grounding via 280 is connected to the intersection 243. The closed line 230 is a "sun" shape, specifically an 8 shape, and the path length of the first annular area 241 is equal to the path length of the second annular area 242. Furthermore, a ground via 280 divides the sealing line 230 into two regions (ie, a first annular region 241 and a second annular region 242 ) with equal paths, and the first coupling portion 231 and the second coupling portion 232 are respectively located in the first annular region 241 and the second annular region 242 .

The first coupling line 220 extends from the first feeding point 219 in two directions (i.e., the upper and lower directions in FIG. 2B) with equal lengths, and the second coupling line 260 extends from the second feeding point 279 in two directions with equal lengths, that is, each of the first coupling line 220 and the second coupling line 260 forms a coupling arm or feeding arm structure. The path length of the first coupling line 220 and the path length of the second coupling line 260 are equal, the path length of the closed line 230 is 4085 um, and the path length of the first coupling line 220 is 1463 um, so the ratio is 2.79.

The filter 200 further includes a first feed line 210, wires 213, 273 and a second feed line 270, all of which are located in the conductive layer 202. The first feed line 210, the second feed line 270, the first coupling portion 231 and the second coupling portion 232 are each a 50 ohm strip line. The width of the wires 213 and 273 is 30 um and the length is 100 um. The width of each of the wires 213 and 273 is different from that of the first feed line 210 and the second feed line 270 and forms an impedance matching unit. The first feed line 210, the wire 213, the first feed point 219 and the first coupling line 220 are connected in sequence, the second feed line 270, the wire 273, the second feed point 279 and the second coupling line 260 are connected in sequence, and the first feed line 210 and the second feed line 270 are both arranged along the virtual transverse axis p. Furthermore, the filter 200 is not symmetrical with respect to the transverse axis p, nor is it symmetrical with respect to the virtual longitudinal axis q, wherein the transverse axis p and the longitudinal axis q are perpendicular to each other. In addition, a plurality of grounding holes 289 are disposed on the inner side of each of the first annular region 241 and the second annular region 242, and a plurality of grounding holes 288 are also disposed along the two sides or around the filter 200. The impedance matching unit of the filter according to the present disclosure can be a wire or pattern on a circuit board.

2B , there is a distance g23 between the first coupling line 220 and the first coupling portion 231 , the ratio of the width w2 (30 um) of the first coupling line 220 to the width w3 (62 um) of the closing line 230 is 0.48, and the ratio of the width w2 of the first coupling line 220 to the distance g23 (29 um) is 1.03.

FIG. 2C is a schematic diagram showing the S parameters of the filter 200 in FIG. 2A , wherein the first measuring port and the second measuring port for measuring the S parameters in the figure can be respectively disposed at the positions of the first feeding line 210 and the second feeding line 270 at the edge of the circuit board 208 . Please refer to Figure 2C. The 3dB bandwidth of filter 200 defined by the S21 parameter is 36.66 GHz to 40.00 GHz. The S11 and S22 parameters within the 3dB bandwidth are both less than -10 dB and exhibit dual modes. The marking point m1 of the S11 parameter is 37.20 GHz and -18.79 dB, and the marking point m2 of the S11 parameter is 39.30 GHz and -19.14 dB. It can be seen that filter 200 has two resonant frequencies of 37.20 GHz and 39.30 GHz, so filter 200 is specifically suitable for today's 5G millimeter wave products and can expand the operating bandwidth. Furthermore, in FIG. 2B of the second embodiment, the distance between the first feed point 219 and the second feed point 279 is 1688 um, and the distance between the two ends of the first coupling line 220 parallel to the longitudinal axis q is 756 um, so the filter 200 has sufficiently small length and width dimensions to be suitable for 5G millimeter wave products.

In the second embodiment, the path length of the closed line 230 is 4085 um, and the effective wavelengths of the two resonance frequencies of the filter 200, 37.20 GHz and 39.30 GHz, on the circuit board 208 are approximately 4316 um and 4085 um, respectively. Therefore, the sum of the path lengths of the first annular region 241 and the second annular region 242 (i.e., the path length of the 8-shaped closed line 230 including the intersection 243) is 0.95 and 1, respectively, compared to the effective wavelengths of the resonance frequencies of the filter 200, 37.20 GHz and 39.30 GHz, on the circuit board 208.

FIG. 3A shows a perspective view of a filter 300 according to a third embodiment of the present disclosure, and FIG. 3B shows a top view of a conductive layer 302 of the filter 300 in FIG. 3A. Referring to FIG. 3A and FIG. 3B, the circuit element according to the third embodiment of the present disclosure is specifically a filter 300, which is disposed on a circuit board 308 and includes a first coupling line 320, a second coupling line 360, a closing line 330, at least one ground plane (not separately labeled) and ground vias 380 and 383. The circuit board 308 specifically includes conductive layers 301, 302, and 303 in order from top to bottom in FIG. 3A.

The first coupling line 320 is connected to the first feeding point 319, and the second coupling line 360 is connected to the second feeding point 379. The closed line 330 includes a first coupling portion 331 and a second coupling portion 332. The first coupling line 320, the second coupling line 360 and the closed line 330 are all located on the conductive layer 302 of the circuit board 308 and are specifically strip lines. The first coupling line 320 and the second coupling line 360 are parallel to the first coupling portion 331 and the second coupling portion 332, respectively. The first coupling line 320 and the second coupling line 360 are coupled to the closed line 330. The at least one ground plane is located on the conductive layers 301 and 303 of the circuit board 308. The ground planes located on the conductive layers 301 and 303 are reference grounds for the first coupling line 320, the second coupling line 360 and the closing line 330. The ground vias 380 and 383 are connected between the closing line 330 and the ground planes located on the conductive layers 301 and 303.

Specifically, the closed line 330 is a single ring, and the number of grounding holes 380 and 383 is two. The grounding holes 380 and 383 are located inside the closed line 330 and divide the closed line 330 into two regions with equal paths (i.e., the first line segment region 341 and the second line segment region 342), and the first coupling portion 331 and the second coupling portion 332 are respectively located in the first line segment region 341 and the second line segment region 342, wherein the first line segment region and the second line segment region of the filter according to the present disclosure can each be a straight line, an arc or a curve. Thus, the filter 300 has a simple resonant structure, which is beneficial to reduce the complexity of the design, and can achieve a dual-mode effect without connecting multiple structures in series. Furthermore, the filter 300 generates a ground path by using the grounding vias 380 and 383, so that the filter 300 generates a low-frequency mode adjacent to the resonance frequency of the ring structure of the original closed line 330, thereby achieving a dual-mode effect to expand the operating bandwidth.

Specifically, the filter 300 further includes branch lines 390 and 393, wherein the branch line 390 is connected between the closed line 330 and the grounding via 380, and the branch line 393 is connected between the closed line 330 and the grounding via 383, and the ratio of the path length of the closed line 330 to the path length d9 of each of the branch lines 390 and 393 is between 10 and 100, wherein the path length of the closed line 330 does not include the path lengths of the branch lines 390 and 393, and the path length d9 of the branch line 390 (or 393) refers to the path length from the edge of the closed line 330 to the center of the grounding via 380 (or 383). Furthermore, the ratio is between 35 and 55. In this way, the characteristic requirements of single-passband dual-mode 3dB bandwidth and the expansion of operating bandwidth can be taken into account. In the third embodiment, the ratio of the path length of the closed line 330 (3906 um) to the path length d9 (89 um) of each of the branch lines 390 and 393 is 43.89.

The first coupling line 320 extends from the first feeding point 319 in two directions (i.e., the upper and lower directions in FIG. 3B) with equal lengths, and the second coupling line 360 extends from the second feeding point 379 in two directions with equal lengths, that is, each of the first coupling line 320 and the second coupling line 360 forms a coupling arm or feeding arm structure. The path length of the first coupling line 320 and the path length of the second coupling line 360 are equal, the path length of the closed line 330 is 3906 um, and the path length of the first coupling line 320 is 1163 um, so the ratio is 3.36.

The filter 300 further includes a first feed line 310 and a second feed line 370, both of which are located in the conductive layer 302. Each of the first feed line 310, the second feed line 370, the first coupling portion 331 and the second coupling portion 332 is a 50 ohm strip line. The first feed point 319 is connected between the first feed line 310 and the first coupling line 320. The second feed point 379 is connected between the second feed line 370 and the second coupling line 360. The first feed line 310 and the second feed line 370 are both arranged along the virtual transverse axis p. Furthermore, the filter 300 is specifically symmetrical about each of the transverse axis p and the virtual longitudinal axis q, wherein the transverse axis p and the longitudinal axis q are perpendicular to each other, that is, the filter 300 is a balanced structure, and it should be understood that the structure of the filter according to the present disclosure can also be symmetrical about only one of the transverse axis and the longitudinal axis, or asymmetrical. In addition, a plurality of ground through holes 388 are also set along the two sides or around the filter 300.

Referring to FIG. 3B , there is a distance g23 between the first coupling line 320 and the first coupling portion 331 , the ratio of the width w2 (30 um) of the first coupling line 320 to the width w3 (62 um) of the closing line 330 is 0.48, and the ratio of the width w2 of the first coupling line 320 to the distance g23 (30 um) is 1.

FIG. 3C is a schematic diagram showing the S parameters of the filter 300 in FIG. 3A , wherein the first measuring port and the second measuring port for measuring the S parameters in the figure can be respectively disposed at the positions of the first feeding line 310 and the second feeding line 370 at the edge of the circuit board 308 . Please refer to FIG. 3C . The 3dB bandwidth of the filter 300 defined by the S21 parameter is 36.98 GHz to 40.41 GHz. The S11 and S22 parameters within the 3dB bandwidth are both less than -10 dB and exhibit dual modes. The marking point m1 of the S11 parameter is 37.40 GHz and -16.41 dB, and the marking point m2 of the S11 parameter is 39.80 GHz and -18.58 dB. It can be seen that the filter 300 has two resonance frequencies of 37.40 GHz and 39.80 GHz, so the filter 300 is specifically suitable for today's 5G millimeter wave products and can expand the operating bandwidth. Furthermore, in FIG. 3B of the third embodiment, the distance between the first feed point 319 and the second feed point 379 is 1840 um, and the distance between the two ends of the first coupling line 320 parallel to the longitudinal axis q is 756 um, so the filter 300 has sufficiently small length and width dimensions to be suitable for 5G millimeter wave products.

In the third embodiment, the path length of the closed line 330 is 3906 um, and the effective wavelengths of the two resonance frequencies of the filter 300, 37.40 GHz and 39.80 GHz, on the circuit board 308 are approximately 4157 um and 3906 um, respectively. Therefore, the sum of the path lengths of the first line segment area 341 and the second line segment area 342 (i.e., the path length of the closed line 330) is 0.94 and 1, respectively, compared to the effective wavelengths of the resonance frequencies of the filter 300, 37.40 GHz and 39.80 GHz, on the circuit board 308.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope of the attached patent application.

100,200,300: filter 101,102,103,201,202,203,301,302,303: conductive layer 108,208,308: circuit board 110,210,310: first feed line 119,219,319: first feed point 120,220,320: first coupling line 130,230,330: closing line 131,231,331: first coupling part 132,232,332: second coupling part 141,241: first annular area 142,242: second annular area 143,243: intersection part 160,260,360: Second coupling line 170,270,370: Second feed line 179,279,379: Second feed point 180,188,189,280,288,289,380,383,388: Ground via 213,273: Conductor 341: First line segment area 342: Second line segment area 390,393: Branch line d9: Path length g23: Spacing m1,m2: Marking point p: Transverse axis q: Longitudinal axis w2,w3: Width

FIG. 1A is a three-dimensional diagram of a filter of the first embodiment of the present disclosure; FIG. 1B is a top view of the conductive layer of the filter in FIG. 1A; FIG. 1C is a schematic diagram of the S parameter of the filter in FIG. 1A; FIG. 1D is a schematic diagram of the surface current density of another filter and the filter in FIG. 1A; FIG. 2A is a three-dimensional diagram of a filter of the second embodiment of the present disclosure; FIG. 2B is a top view of the conductive layer of the filter in FIG. 2A; FIG. 2C is a schematic diagram of the S parameter of the filter in FIG. 2A; FIG. 3A is a three-dimensional diagram of a filter of the third embodiment of the present disclosure; FIG. 3B is a top view of the conductive layer of the filter in FIG. 3A; and Figure 3C shows a schematic diagram of the S parameters of the filter in Figure 3A.

100: filter 101,102,103: conductive layer 108: circuit board 110: first feed line 119: first feed point 120: first coupling line 130: closing line 131: first coupling part 132: second coupling part 141: first annular area 142: second annular area 143: intersection 160: second coupling line 170: second feed line 179: second feed point 180,188,189: ground via

Claims (10)

A filter is provided on a circuit board and comprises: a first coupling line connected to a first feed point; a second coupling line connected to a second feed point; a closed line comprising a first coupling portion and a second coupling portion, wherein the first coupling line, the second coupling line and the closed line are all located on a conductive layer of the circuit board, the first coupling line and the second coupling line are respectively parallel to the first coupling portion and the second coupling portion, and the first coupling line and the second coupling line couple the closed line; at least one ground plane located on at least another conductive layer of the circuit board, wherein the at least one ground plane is a reference ground for the first coupling line, the second coupling line and the closed line; and at least one ground via connected between the closed line and the at least one ground plane. A filter as described in claim 1, wherein the closed line includes a first annular region and a second annular region, the first coupling portion and the second coupling portion are respectively located in the first annular region and the second annular region, the first annular region and the second annular region are connected to an intersection, and the at least one grounding via is connected to the intersection. A filter as described in claim 2, wherein the closed line is in the shape of a figure 8, and the path length of the first annular region is equal to the path length of the second annular region. A filter as described in claim 2, wherein the filter has at least two resonant frequencies, and the ratio of the sum of the path length of the first annular region and the path length of the second annular region to the effective wavelength of each of the at least two resonant frequencies of the filter in the circuit board is between 0.8 and 1.1. A filter as described in claim 1, wherein the closed line is a single ring, the number of the at least one grounding via is two, and the two grounding vias divide the closed line into a first line segment area and a second line segment area with equal path lengths. The filter as described in claim 5 further comprises: two branches, wherein each branch is connected between the closed line and a ground via, and the ratio of the path length of the closed line to the path length of each branch is between 10 and 100. A filter as described in claim 1, wherein the path length of the first coupled line and the path length of the second coupled line are equal, and the ratio of the path length of the closed line to the path length of the first coupled line is between 2.2 and 20. The filter as described in claim 1 further comprises: a first feed line, wherein the first feed point is connected between the first feed line and the first coupling line; and a second feed line, wherein the second feed point is connected between the second feed line and the second coupling line; wherein the first feed line and the second feed line are both arranged along a virtual transverse axis. A filter as described in claim 8, wherein the filter is symmetrical about each of the transverse axis and a virtual longitudinal axis, and the transverse axis and the longitudinal axis are perpendicular to each other; wherein there is a spacing between the first coupling line and the first coupling portion, and the ratio of the width of the first coupling line to the width of the closed line is between 0.2 and 5, and the ratio of the width of the first coupling line to the spacing is between 0.25 and 3. A circuit element is arranged on a circuit board and comprises: a first coupling line extending from a first feeding point to two directions with equal lengths; a second coupling line extending from a second feeding point to two directions with equal lengths; a closing line comprising a first coupling portion and a second coupling portion, wherein the first coupling line, the second coupling line and the closing line are all located on a conductive layer of the circuit board, and the first coupling line and the second coupling line are respectively parallel to the first coupling line. The first coupling line and the second coupling line are coupled to the closed line; at least one ground plane is located on at least another conductive layer of the circuit board, wherein the at least one ground plane is a reference ground for the first coupling line, the second coupling line and the closed line; and at least one ground via is connected between the closed line and the at least one ground plane, wherein the at least one ground via divides the closed line into a plurality of regions with equal paths.