Printed filter

Abstract

A printed filter includes a first resonator, a second resonator, and a third resonator. The first resonator, the second resonator, and the third resonator each include one open-circuit segment and two short-circuit segments. Each short-circuit segment of the first resonator, the second resonator, and the third resonator are grounded. The two short-circuit segments of the respective first resonator and the second resonator are connected to form an L-shape. The open-circuit segment of the respective first resonator and the second resonator connects to its respective L-shape to form an arrow. The two short-circuit segments of the third resonator are connected to form a straight line. The open-circuit segment of the third resonator connects to the straight line of the third resonator to form a T-shape. One of the short-circuit segments of each of the first resonator and the second resonator is parallel to the straight line of the third resonator.

Description

Technical Field

[0001] This disclosure relates to a filter, and more particularly to a printed filter. Prior Technology

[0002] With increasing competition among communication products, reducing production costs has become an inevitable trend. Printed filters (such as microstrip filters) manufactured using printed circuit board (PCB) technology are small in size and cost-effective, thus widely used in communication products. Printed band-pass filters in communication products can prevent interference between signals from different frequency bands. However, traditional printed band-pass filters struggle to meet the nearly 1 GHz bandwidth required to support high data rates in the UNII-1 to UNII-3 bands used for Wi-Fi. Furthermore, when the frequency of the signal to be filtered is close to the passband frequency of the band-pass filter, a larger attenuation slope at the cutoff frequency is needed to effectively suppress out-of-band signals and reduce interference with surrounding frequency bands. Traditional printed band-pass filters typically use high-order designs to achieve greater bandwidth or increase the attenuation slope at the cutoff frequency, but this increases the circuit area. With the trend towards miniaturization of communication products, there is a need for printed filters that are small in size, have high bandwidth, and have a high attenuation slope to solve the above problems. Summary of the Invention

[0003] In some embodiments, a printed filter is provided, comprising: a first resonator, a second resonator, and a third resonator; wherein each of the first, second, and third resonators includes an open-circuit segment and two short-circuit segments, each short-circuit segment of the first, second, and third resonators is grounded; the two short-circuit segments of the first and second resonators are connected to form an L-shape; the open-circuit segments of the first and second resonators are connected to their respective L-shapes to form an arrow; the two short-circuit segments of the third resonator are connected to form a straight line; the open-circuit segment of the third resonator is connected to the straight line of the third resonator to form a T-shape; and one of the short-circuit segments of the first and second resonators is parallel to the straight line of the third resonator.

[0004] To further understand the features and technical content of this disclosure, please refer to the following detailed description and figures related to this disclosure. However, the figures provided are for reference and illustration only and are not intended to limit the content of this disclosure. Simple Explanation of the Diagram

[0005] Figure 1 shows a schematic diagram of a printed filter according to an embodiment of the present disclosure. Figures 2A, 2B, and 2C are schematic diagrams showing different morphologies of the resonator according to embodiments of the present disclosure. Figure 3 shows a schematic diagram of a trisection structure according to an embodiment of the present disclosure. Figure 4A shows the theoretical S-parameter curves calculated based on the required filter specifications. Figure 4B shows the S-parameter values ​​obtained by simulating the printed filter disclosed herein using electromagnetic simulation software. Implementation

[0006] Those skilled in the art can understand the advantages and effects of this disclosure from the content disclosed in this specification. This disclosure can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of this disclosure. In addition, the drawings in this disclosure are only simple illustrations and are not depictions based on actual dimensions, as stated in advance. The following embodiments will further describe the relevant technical content of this disclosure in detail, but the disclosed content is not intended to limit the scope of protection of this disclosure. In addition, it should be understood that although terms such as "first," "second," and "third" may be used in this document to describe various elements, these elements should not be limited by these terms. These terms are mainly used to distinguish one element from another. Furthermore, "connection" in the entire disclosure means that there is a physical connection between two elements, and it is a direct or indirect connection, and "coupling" in the entire disclosure means that there is no physical connection between two elements, but rather that the elements are coupled by the induction of electric and / or magnetic fields.

[0007] This disclosure provides a printed filter that is small in size, has high bandwidth, and has a high attenuation slope.

[0008] Figure 1 shows a schematic diagram of a printed filter 100 according to an embodiment of the present disclosure. The printed filter 100 can be disposed on a substrate (e.g., a PCB). The printed filter 100 can be a bandpass filter. The printed filter 100 includes a first resonator 104, a second resonator 106, a third resonator 108, a fourth resonator 110, a fifth resonator 112, and a sixth resonator 114. The first resonator 104 includes an open-circuit segment 104a and two short-circuit segments 104b, the second resonator 106 includes an open-circuit segment 106a and two short-circuit segments 106b, the third resonator 108 includes an open-circuit segment 108a and two short-circuit segments 108b, the fourth resonator 110 includes an open-circuit segment 110a and two short-circuit segments 110b, the fifth resonator 112 includes an open-circuit segment 112a and two short-circuit segments 112b, and the sixth resonator 114 includes an open-circuit segment 114a and two short-circuit segments 114b. Each short-circuit segment 104b, 106b, 108b, 110b, 112b, and 114b can be grounded via a separate via 118.

[0009] The printed filter 100 may further include an input section 102 and an output section 116. Signals transmitted from the input section 102 to the output section 116, after passing through the printed filter 100, can filter out signals other than the high cutoff frequency and low cutoff frequency, allowing passband signals between the high and low cutoff frequencies to pass through; this avoids interference with signals of other surrounding frequencies. The input section 102 is physically separated from and configured to be energy-coupled with the first resonator 104. The output section 116 is physically separated from and configured to be energy-coupled with the fourth resonator 110. The input section 102 may include a branch 102', and the shape of the branch 102' can be adapted to the first resonator 104 so that the input section 102 can surround at least a portion of the open-circuit section 104a of the first resonator 104, thereby increasing the coupling. Furthermore, due to its shape design, a portion of the branch 102' of the input segment 102 can be energy-coupled with the two short-circuit segments 104b of the first resonator 104 to increase the coupling amount. The output segment 116 may include the branch 116', and the shape of the branch 116' can be matched with the fourth resonator 110, such that the output segment 116 can surround at least a portion of the open-circuit segment 110a of the fourth resonator 110 to increase the coupling amount. Furthermore, due to its shape design, a portion of the branch 116' of the output segment 116 can be energy-coupled with the two short-circuit segments 110b of the fourth resonator 110 to increase the coupling amount.

[0010] The first resonator 104, the second resonator 106, the third resonator 108, the fourth resonator 110, the fifth resonator 112, and the sixth resonator 114 are physically separated from each other. One of the short-circuit segments 104b, 106b, 110b, and 112b of each of the first resonator 104, the second resonator 106, the fourth resonator 110, and the fifth resonator 112 is parallel to the straight line formed by the short-circuit segments 108b and 114b of the third resonator 108 and the sixth resonator 114, respectively.

[0011] The principle of the printed filter 100 is described below with reference to Figures 2A, 2B, 2C, and 3. Figures 2A, 2B, 2C, and 3 can be referred to in conjunction with Figure 1. Figure 2A shows a resonator 200, which includes an open-circuit segment 202a and two short-circuit segments 202b, each of which is grounded via a separate via 118. The resonator 200 may have a resonant frequency, wherein the lengths of the open-circuit segment 202a and the short-circuit segment 202b can be designed according to the wavelength corresponding to the resonant frequency. For example, the resonator 200 may be a quarter-wavelength resonator, wherein the lengths of the open-circuit segment 202a and the short-circuit segment 202b are each approximately one-eighth of a wavelength. The impedance of the open-circuit segment 202a is approximately Z0, while the impedance of the short-circuit segment 202b is approximately 2Z0, that is, the impedance of each short-circuit segment 202b is approximately twice that of the open-circuit segment 202a. The two short-circuit segments 202b in Figure 2A are connected in parallel, so the equivalent impedance of the two parallel short-circuit segments 202b is Z0, thereby realizing the resonator 200 as a quarter-wavelength resonator with uniform impedance.

[0012] Figure 2B shows a resonator 210, which also includes an open-circuit segment 202a and two short-circuit segments 202b, with the lengths and impedances of the open-circuit segment 202a and the short-circuit segment 202b as described in Figure 2A; however, the arrow shape of the resonator 210 differs from that of the resonator 200 in Figure 2A. In Figure 2B, the two short-circuit segments 202b are connected to form an L-shape, and then the open-circuit segment 202a is connected to the L-shape to form an arrow. This arrow shape increases the coupling flexibility between resonators. The L-shape formed by the two short-circuit segments 202b shown in Figure 2B has an included angle of approximately 90 degrees, but in some other embodiments, the L-shape can have other included angles. Furthermore, Figure 2B shows that the open-circuit segment 202a is generally rectangular, but the open-circuit segment 202a may be configured in other shapes, such as a stepped shape or other shapes. The aforementioned shape variations of the short-circuit segments 202b and the open-circuit segment 202a can still be considered as forming an arrow. The arrow-shaped resonator 210 shown in Figure 2B corresponds to the first resonator 104, the second resonator 106, the fourth resonator 110, and the fifth resonator 112 in Figure 1. However, it should be noted that the lengths and widths of the open-circuit segments 104a, 106a, 110a, and 112a and the short-circuit segments 104b, 106b, 110b, and 112b of the first resonator 104, the second resonator 106, the fourth resonator 110, and the fifth resonator 112 may vary due to adjustments. For example, the length or width of the open-circuit segment 104a of the first resonator 104 may differ from the length or width of the open-circuit segment 106a of the second resonator 106. For example, the two short-circuit segments 104b of the first resonator 104 may have the same length, and the two short-circuit segments 106b of the second resonator 106 may have the same length, and the lengths of the two short-circuit segments 104b of the first resonator 104 may differ from the lengths of the two short-circuit segments 106b of the second resonator 106. For the sake of simplicity, other variations in length and width are not listed one by one.

[0013] Figure 2C shows resonator 220, which also includes an open-circuit segment 202a and two short-circuit segments 202b, and the lengths and impedances of the open-circuit segment 202a and the short-circuit segment 202b are as described in Figure 2A; however, the T-shape of resonator 220 differs from that of resonator 200 in Figure 2A. In Figure 2C, the two short-circuit segments 202b are connected to form a straight line, and then the open-circuit segment 202a is connected to form a T-shape. This T-shape also increases the coupling flexibility between resonators. Figure 2C shows that the open-circuit segment 202a is generally rectangular, but the open-circuit segment 202a may be configured in other shapes, such as a stepped shape or other shapes. The T-shaped resonator 220 shown in Figure 2C corresponds to the third resonator 108 and the sixth resonator 114 in Figure 1. However, it should be noted that the lengths and widths of the open-circuit segments 108a and 114a and the short-circuit segments 108b and 114b of the third resonator 108 and the sixth resonator 114 may vary due to adjustments. For example, the length or width of the open-circuit segment 108a of the third resonator 108 may differ from the length or width of the open-circuit segment 114a of the sixth resonator 114. As another example, the two short-circuit segments 108b of the third resonator 108 may have the same length, and the two short-circuit segments 114b of the sixth resonator 114 may have the same length, but the lengths of the two short-circuit segments 108b of the third resonator 108 may differ from the lengths of the two short-circuit segments 114b of the sixth resonator 114. For the sake of simplicity, other variations in length and width are not listed individually.

[0014] In some variations, the lengths of the open-circuit segment 202a and the short-circuit segment 202b in the same resonator 210 and 220 shown in Figures 2B and 2C may differ. In other words, although it was previously mentioned that the lengths of the open-circuit segment 202a and the short-circuit segment 202b are approximately one-eighth of the wavelength, in practice, the lengths of the open-circuit segment 202a and / or the short-circuit segment 202b may be changed to adjust the characteristics of the filter, resulting in different lengths of the open-circuit segment 202a and the short-circuit segment 202b. This disclosure includes such variations.

[0015] Furthermore, the length and width of the open-circuit segments (e.g., open-circuit segments 104a, 106a, 110a, 112a) and short-circuit segments (e.g., short-circuit segments 104b, 106b, 110b, 112b) of the arrow-shaped resonators (e.g., the first resonator 104, the second resonator 106, the fourth resonator 110, and the fifth resonator 112) may also differ from those of the open-circuit segments (e.g., open-circuit segments 108a, 114a) and short-circuit segments (e.g., short-circuit segments 108b, 114b) of the T-shaped resonators (e.g., the third resonator 108 and the sixth resonator 114).

[0016] Figure 3 shows a trisection 300 formed by two arrow-shaped resonators 302 and 304 and a T-shaped resonator 306. A single trisection 300 already provides filtering, but multiple trisections 300 can be cascaded to enhance the filtering characteristics. Figure 3 can be referenced in conjunction with Figure 1. Figure 1 can be considered as two cascaded trisections 300, where resonators 302 and 304 in Figure 3 correspond to the first resonator 104 and the second resonator 106 in Figure 1, or to the fourth resonator 110 and the fifth resonator 112. Furthermore, resonator 306 in Figure 3 can correspond to the third resonator 108 or the sixth resonator 114 in Figure 1. Referring to Figure 3, resonator 302 includes an open-circuit segment 302a and two short-circuit segments 302b, resonator 304 includes an open-circuit segment 304a and two short-circuit segments 304b, and resonator 306 includes an open-circuit segment 306a and two short-circuit segments 306b. One of the short-circuit segments 302b and 304b of each of resonators 302 and 304 can be parallel to the straight line formed by the two short-circuit segments 306b of resonator 306. Resonators 302, 304, and 306 are physically separated but can be energy-coupled, where energy coupling is represented in Figure 3 as coupling C1, coupling C2, and coupling C3. In the embodiment shown in Figure 3, resonators 302 and 304 are coupled via short-circuit segments 302b and 304b (C1); resonators 304 and 306 are coupled via short-circuit segments 304b and 306b (C2); and resonators 306 and 302 are coupled via short-circuit segments 306b and 302b (C3). A first gap G1 exists between resonators 302 and 304, a second gap G2 exists between resonators 304 and 306, and a third gap G3 exists between resonators 302 and 306. The minimum value of the first gap G1 may be the same as or different from the minimum value of the second gap G2; the minimum value of the first gap G1 may be the same as or different from the minimum value of the third gap G3; and the minimum value of the second gap G2 may be the same as or different from the minimum value of the third gap G3. For example, in some embodiments, the minimum value of the third gap G3 may be greater than the minimum value of the first gap G1 or the minimum value of the second gap G2. The sizes of the first gap G1, the second gap G2, and the third gap G3 may directly or indirectly affect the following characteristics of the three-section structure 300: the coupling amount between conductors C1-C3, bandwidth, insertion loss, stopband attenuation, and transmission zero. The length and width of the open-circuit sections 302a, 304a, 306a and the short-circuit sections 302b, 304b, 306b will also affect the characteristics of the three-section structure 300, such as the resonant frequency and the coupling amount.The theoretical examples above are for reference only. In practice, the various characteristics of a filter may be interconnected, meaning that the length, width, and gaps between each resonator all affect these characteristics.

[0017] The three-section structure 300 shown in Figure 3 can generate a transmission zero in the out-of-band region. The printed filter 100 shown in Figure 1 is formed by cascading two three-section structures 300 together, which can generate two transmission zeros in the out-of-band region to provide sufficient out-of-band suppression. The transmission zero will be further described in Figure 4A. The cascading of two three-section structures 300 can be achieved through open-circuit coupling of resonators. For example, as shown in Figure 1, the third resonator 108 and the sixth resonator 114 are configured to couple energy via their respective open-circuit segments 108a and 114a to cascade the two three-section structures.

[0018] Figure 4A shows the theoretical S-parameter curves calculated according to the required filter specifications. Figure 4B shows the S-parameter values ​​obtained by simulating the printed filter 100 disclosed herein using electromagnetic simulation software. The results obtained in Figure 4B should be as close as possible to the curves in Figure 4A. S-parameters are frequently used to evaluate the transmission and reflection characteristics of one or more ports in a circuit. The S-parameters shown in Figures 4A and 4B include S11 and S21, where S11 can be used to evaluate the reflection characteristics of the signal at input segment 102, and S21 can be used to evaluate the transmission characteristics of the signal from input segment 102 to output segment 116.

[0019] As shown in Figure 4A, the goal is to design a bandpass filter that generates a passband in the frequency band of approximately 5180 MHz to 5835 MHz, allowing passband signals to pass through while filtering out signals outside the passband. This design can meet the bandwidth requirements of Wi-Fi in the UNII-1 to UNII-3 frequency bands. In the passband between 5180 MHz and 5835 MHz shown in Figure 4A, S11 is approximately -20 dB to -50 dB, and S21 is approximately 0 dB, indicating that the signal in the passband frequency receives minimal reflection at input segment 102, and most of the signal can be transmitted from input segment 102 to output segment 116 without attenuation. Regarding out-of-band characteristics, since it is desirable to effectively filter signals above 6 GHz while allowing signals between 5180 MHz and 5835 MHz to pass through, generating a high attenuation slope in the narrow frequency band between 5835 MHz and 6 GHz will be one of the challenges in bandpass filter design. As previously mentioned, cascading two three-section structures 300 generates two transmission zeros, corresponding to approximately 5980 MHz and 6090 MHz of the S21 parameter in Figure 4A. These two transmission zeros enhance the filtering effect near 6 GHz, resulting in approximately 40 dB of out-of-band attenuation at approximately 5900 MHz.

[0020] Figure 4B shows the S-parameter values ​​obtained by simulating the printed filter 100 of this disclosure using electromagnetic simulation software. Figure 4B shows that the passband bandwidth is close to 1 GHz, while an out-of-band attenuation of approximately 45 dB is achieved at 6105 MHz. Although the results shown in Figure 4B do not clearly show the two transmission zeros near 6 GHz as in Figure 4A, the out-of-band suppression effect still exists. The S-parameters shown in Figure 4B are for reference only; however, the S-parameters measured for a real-world printed filter 100 will be affected by the size of each resonator and the gap between the resonators. Nevertheless, the printed filter 100 of this disclosure achieves a small size, high bandwidth, and high attenuation slope.

[0021] The scope of the patent application disclosed herein is not limited to the above content. Therefore, all equivalent technical changes made using the contents of this disclosure specification and drawings are included within the scope of the patent application.

[0022] 100: Printed Filter 102: Input segment 102', 116': Support segment 104: First resonator 104a, 106a, 108a, 110a, 112a, 114a, 202a, 302a, 304a, 306a: Open sections 104b, 106b, 108b, 110b, 112b, 114b, 202b, 302b, 304b, 306b: Short circuits 106: Second resonator 108: Third Resonator 110: Fourth Resonator 112: Fifth Resonator 114: The Sixth Resonator 116: Output segment 118: Through hole 200, 210, 220, 302, 304, 306: Resonators 300: Three-section structure C1, C2, C3: Coupling G1: First gap G2: Second gap G3: Third gap

Claims

1. A printed filter comprising: a first resonator; a second resonator; and a third resonator; wherein each of the first, second, and third resonators includes an open-circuit segment and two short-circuit segments, each of the short-circuit segments of the first, second, and third resonators being grounded; the two short-circuit segments of each of the first and second resonators being connected to form an L-shape; the open-circuit segments of each of the first and second resonators being connected to their respective L-shapes to form an arrow; the two short-circuit segments of the third resonator being connected to form a straight line; the open-circuit segment of the third resonator being connected to the straight line of the third resonator to form a T-shape; one of the short-circuit segments of each of the first and second resonators being parallel to the straight line of the third resonator; and the first, second, and third resonators being configured to energy couple to each other via their respective two short-circuit segments.

2. The printed filter as claimed in claim 1, further comprising: a fourth resonator; a fifth resonator; and a sixth resonator; wherein each of the fourth, fifth, and sixth resonators comprises an open-circuit segment and two short-circuit segments, and each of the short-circuit segments of the fourth, fifth, and sixth resonators is grounded; the two short-circuit segments of each of the fourth and fifth resonators are connected to form an L-shape; the open-circuit segments of each of the fourth and fifth resonators are connected to their respective L-shapes to form an arrow; the two short-circuit segments of the sixth resonator are connected to form a straight line; the open-circuit segment of the sixth resonator is connected to the straight line of the sixth resonator to form a T-shape; and one of the short-circuit segments of each of the first, second, fourth, and fifth resonators is parallel to the respective straight lines of the third and sixth resonators.

3. The printed filter as claimed in claim 2, wherein the first resonator, the second resonator, the third resonator, the fourth resonator, the fifth resonator, and the sixth resonator are physically separated from each other.

4. The printed filter as claimed in claim 2, wherein the fourth resonator, the fifth resonator and the sixth resonator are configured to be energy-coupled to each other via their respective two short-circuit sections.

5. The printed filter as claimed in claim 2, wherein the third resonator and the sixth resonator are configured to perform energy coupling via their respective open sections.

6. The printed filter as claimed in claim 1, wherein the two short-circuit segments of the first resonator have the same length, the two short-circuit segments of the second resonator have the same length, and the length of the two short-circuit segments of the first resonator is different from the length of the two short-circuit segments of the second resonator.

7. The printed filter as claimed in claim 2, wherein the open-circuit segment of the third resonator has a length, the open-circuit segment of the sixth resonator has a length, and the length of the open-circuit segment of the third resonator is different from the length of the open-circuit segment of the sixth resonator.

8. The printed filter as claimed in claim 2, wherein the open-circuit segment of the third resonator has a width, the open-circuit segment of the sixth resonator has a width, and the width of the open-circuit segment of the third resonator is different from the width of the open-circuit segment of the sixth resonator.

9. The printed filter as claimed in claim 1, wherein a first gap is provided between the first resonator and the second resonator, a second gap is provided between the second resonator and the third resonator, and a third gap is provided between the first resonator and the third resonator, wherein: The minimum value of the first gap is different from the minimum value of the second gap; the minimum value of the first gap is different from the minimum value of the third gap; Or the minimum value of the second gap is different from the minimum value of the third gap.

10. The printed filter as described in claim 1, wherein the L-shape has an angle of 90 degrees.

11. The printed filter as claimed in claim 1, wherein the first resonator has a resonant frequency, and the open-circuit segment and the two short-circuit segments of the first resonator have the same length, which is equal to one-eighth of a wavelength corresponding to the resonant frequency.

12. The printed filter as claimed in claim 2, further comprising: an input segment; and an output segment; wherein the input segment is separate from the first resonator entity and is configured to be energy-coupled with the first resonator; and the output segment is separate from the fourth resonator entity and is configured to be energy-coupled with the fourth resonator.

13. The printed filter as claimed in claim 12, wherein the input segment surrounds at least a portion of the open-circuit segment of the first resonator, and the output segment surrounds at least a portion of the open-circuit segment of the fourth resonator.

14. The printed filter as claimed in claim 13, wherein the input segment and the output segment each include a branch segment, a portion of the branch segment of the input segment being configured to energy couple to the two short-circuit segments of the first resonator, and a portion of the branch segment of the output segment being configured to energy couple to the two short-circuit segments of the fourth resonator.

15. The printed filter as claimed in claim 1, wherein the impedance of each of the two short-circuit segments of the first resonator, the second resonator, or the third resonator is twice the impedance of the open-circuit segment.

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