Filter device and high-frequency front-end circuit having the same

Abstract

A filter device (100) includes a dielectric substrate (110), an input terminal (T1), an output terminal (T2), a ground terminal (GND), a common electrode (PC), and resonators (RC1-RC4). Each resonator is connected to the common electrode and the ground terminal. The resonators (RC3, RC4) are disposed between the resonators (RC1, RC2). Each resonator includes a capacitor, and a first passage and a second passage connected to the common electrode. The first passage is connected to the ground terminal via the capacitor, and the second passage is directly connected to the ground terminal. In the common electrode, a direction from the first passage to the second passage of the resonator (RC1) is opposite to a direction from the first passage to the second passage of the resonator (RC2). For the resonators (RC3, RC4), a shortest path along the common electrode of each first passage intersects a shortest path along the common electrode of each second passage.

Description

Technical Field

[0001] This disclosure relates to filter devices and high-frequency front-end circuits having the filter devices, and more particularly to techniques for improving the characteristics of filter devices. Background Technology

[0002] International Patent Publication No. 2019 / 097774 (Patent Document 1) discloses a stacked bandpass filter with four LC parallel resonators arranged between the input and output terminals. In the bandpass filter of International Patent Publication No. 2019 / 097774 (Patent Document 1), two capacitors (a first capacitor and a second capacitor) are connected in series between the resonators connected to the input terminal and the resonator connected to the output terminal, and a third capacitor is formed between the connection node of these two capacitors and the ground point. By forming this configuration, the frequency of the attenuation poles on the high-frequency side compared to the passband can change while the frequency of the attenuation poles on the low-frequency side compared to the passband remains almost unchanged. Prior art literature Patent documents

[0003] Patent Document 1: International Publication No. 2019 / 097774 Summary of the Invention The problem that the invention aims to solve

[0004] Typically, it is desirable to have low insertion loss in the passband and high attenuation in the non-passband of a filter device. In a filter device composed of multiple resonators as described above, the insertion loss and attenuation can be adjusted by the coupling state between the resonators. However, since there is usually a trade-off between insertion loss and attenuation, it is sometimes difficult to improve these two characteristics.

[0005] This disclosure is made to solve the aforementioned problems, and its purpose is to improve the attenuation characteristics in the non-passband while reducing the insertion loss in the passband in a filter device composed of multiple resonators. Methods for solving problems

[0006] The filter device disclosed herein includes: a dielectric substrate having a first surface and a second surface; an input terminal, an output terminal, and a ground terminal disposed on the second surface of the dielectric substrate; a common electrode disposed inside the dielectric substrate; and a first resonator to a fourth resonator. Each of the first to fourth resonators is connected to the common electrode and the ground terminal. The first resonator is connected to the input terminal, and the second resonator is connected to the output terminal. A third and fourth resonator are disposed between the first and second resonators. Each of the first to fourth resonators includes a capacitor, a first path, and a second path. One end of the first path is connected to the common electrode, and the other end is connected to the ground terminal via the capacitor. One end of the second path is connected to the common electrode, and the other end is connected to the ground terminal without passing through the capacitor. In the common electrode, the direction of the first resonator from the first path to the second path is opposite to the direction of the second resonator from the first path to the second path. The shortest path along the common electrode from the first path of the third resonator to the first path of the fourth resonator intersects with the shortest path along the common electrode from the second path of the third resonator to the second path of the fourth resonator. The effects of the invention

[0007] According to the filter device disclosed herein, in a filter device comprising four resonators, each resonator is connected to a common electrode. Therefore, compared to a case where the resonators are not interconnected, the resistance between the resonators is reduced, thereby reducing insertion loss in the passband.

[0008] Furthermore, by arranging the paths in the first resonator (first resonator) and the fourth resonator (second resonator) in opposite configurations, the magnetic coupling between the resonators is weakened, thus increasing the attenuation at lower frequencies compared to the passband. Additionally, in the second resonator (third resonator) and the third resonator (fourth resonator), the shortest path along each first path of the common electrode intersects with the shortest path along each second path of the common electrode. This allows for the realization of a resonator with a small inductance and a large capacitance.

[0009] Therefore, in the filter device disclosed herein, it is possible to reduce insertion loss in the passband while improving attenuation characteristics in the non-passband in a filter device composed of multiple resonators. Attached Figure Description

[0010] Figure 1 It is a block diagram of a communication device having a high-frequency front-end circuit that applies the filter device according to Embodiment 1. Figure 2 This is the equivalent circuit diagram of the filter device in Implementation Method 1. Figure 3 This is a perspective view of the filter device according to Embodiment 1. Figure 4 This is an exploded perspective view showing an example of the stacked structure of the filter device in Embodiment 1. Figure 5 This is a top view of the common electrode in the filter device of Embodiment 1. Figure 6 This is a diagram used to illustrate the configuration of the resonators in a comparative filter device. Figure 7 This is a diagram showing the throughput characteristics of the filter device according to Embodiment 1. Figure 8 This is a top view of the common electrode in the filter device of Modified Example 1. Figure 9 This is a top view of the common electrode in the filter device of Modified Example 2. Figure 10 This is a top view of the common electrode in the filter device of Modified Example 3. Figure 11 This is a top view of the common electrode in the filter device of Modified Example 4. Figure 12 This is a perspective view of the common electrode in the filter device of Modified Example 5. Figure 13 This is a perspective view of the common electrode in the filter device of Modified Example 6. Figure 14 This is a perspective view of the shielding electrode in the filter device of Modified Example 7. Figure 15 This is a top view of the common electrode in the filter device according to Embodiment 2. Figure 16 This is a top view of the common electrode in the filter device according to Embodiment 3. Figure 17 This is a top view of the common electrode in the filter device according to Embodiment 4. Detailed Implementation

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Furthermore, identical or equivalent parts in the drawings will be labeled with the same reference numerals, and their descriptions will not be repeated.

[0012] [Implementation Method 1] (Basic components of a communication device) Figure 1 This is a block diagram of a communication device 10 having a high-frequency front-end circuit 20 that applies the filter device of embodiment 1. The communication device 10 is, for example, a mobile phone base station.

[0013] Reference Figure 1The communication device 10 includes an antenna 12, a high-frequency front-end circuit 20, a mixer 30, a local oscillator 32, a D / A converter (DAC) 40, and an RF circuit 50. Furthermore, the high-frequency front-end circuit 20 includes bandpass filters 22 and 28, an amplifier 24, and an attenuator 26. Additionally, in... Figure 1 In this description, the high-frequency front-end circuit 20 includes a transmitting circuit that transmits high-frequency signals from the antenna 12, but the high-frequency front-end circuit 20 may also include a receiving circuit that receives high-frequency signals via the antenna 12.

[0014] The communication device 10 up-converts the transmit signal from the RF circuit 50 into a high-frequency signal and transmits it from the antenna 12. The modulated digital signal output from the RF circuit 50 is converted into an analog signal by the D / A converter 40. The mixer 30 mixes the transmitted signal (converted from digital to analog by the D / A converter 40) with the oscillation signal from the local oscillator 32 and up-converts it into a high-frequency signal. The bandpass filter 28 removes unwanted waves generated during up-conversion, extracting only the transmit signal within the desired frequency band. The attenuator 26 adjusts the strength of the transmitted signal. The amplifier 24 amplifies the power of the transmitted signal after passing through the attenuator 26 to a specified level. The bandpass filter 22 removes unwanted waves generated during amplification and allows only the signal components within the frequency band determined according to the communication standard to pass through. The transmitted signal after passing through the bandpass filter 22 is transmitted from the antenna 12.

[0015] The bandpass filters 22 and 28 in the aforementioned communication device 10 may be filter devices corresponding to this disclosure.

[0016] (Composition of the filter device) Next, use Figures 2-5 The detailed configuration of the filter device 100 in Embodiment 1 is explained.

[0017] Figure 2 This is the equivalent circuit diagram of filter device 100. (Refer to...) Figure 2 The filter device 100 includes an input terminal T1, an output terminal T2, and resonators RC1 to RC4. Each of the resonators RC1 to RC4 is an LC parallel resonator formed by connecting an inductor and a capacitor in parallel.

[0018] The resonator RC1 includes inductors L1A and L1B connected in series between the input terminal T1 and the ground terminal GND, and capacitor C1 connected in parallel with inductors L1A and L1B. The connection node N1A of inductor L1A and capacitor C1 is connected to the input terminal T1. The connection node N1B of inductor L1B and capacitor C1 is connected to the ground terminal GND.

[0019] The resonator RC2 includes inductors L2A and L2B connected in series between the input terminal T2 and the ground terminal GND, and capacitor C2 connected in parallel with inductors L2A and L2B. The connection node N2A of inductor L2A and capacitor C2 is connected to the input terminal T2. The connection node N2B of inductor L2B and capacitor C2 is connected to the ground terminal GND.

[0020] The resonator RC3 includes inductors L3A and L3B connected in series, and capacitor C3 connected in parallel with inductors L3A and L3B. The connection node N3A of inductor L3A and capacitor C3 is connected to the connection node N1A of resonator RC1 (i.e., input terminal T1) via capacitor C13. The connection node N3B of inductor L3B and capacitor C3 is connected to the ground terminal GND.

[0021] The resonator RC4 includes inductors L4A and L4B connected in series, and capacitor C4 connected in parallel with inductors L4A and L4B. The connection point N4A of inductors L4A and capacitor C4 is connected to the connection point N2A of resonator RC2 (i.e., output terminal T2) via capacitor C24. The connection point N4B of inductors L4B and capacitor C4 is connected to the ground terminal GND.

[0022] Additionally, the connection node N1A (input terminal T1) of resonator RC1 and the connection node N2A (output terminal T2) of resonator RC2 are connected via capacitor C12. Furthermore, the connection nodes of the two inductors in each resonator are interconnected. The corresponding parts of the resonators that are commonly connected correspond to... Figure 4 The common electrode PC will be described later.

[0023] Each resonator is magnetically coupled to the others. Thus, the filter device 100 has a configuration with four mutually magnetically coupled resonators arranged between the input terminal T1 and the output terminal T2. By adjusting the resonant frequency of each resonator, the filter device 100 functions as a bandpass filter that allows signals of the desired frequency band to pass through.

[0024] Figure 3 This is a perspective view of the filter device 100. Figure 4 This is an exploded perspective view showing an example of the stacked structure of the filter device 100.

[0025] Reference Figure 3 and Figure 4The filter device 100 includes a cuboid or substantially cuboid dielectric substrate 110 formed by stacking multiple dielectric layers LY1 to LY8 along a stacking direction. The dielectric layers LY1 to LY8 are formed, for example, of ceramics such as low-temperature co-fired ceramics (LTCC) or resin. Inside the dielectric substrate 110, inductors and capacitors of an LC parallel resonator are formed by multiple electrodes disposed in each dielectric layer and multiple pathways disposed between the dielectric layers. Furthermore, in this specification, "pathway" refers to a conductor disposed in a dielectric layer for connecting electrodes disposed in different dielectric layers. The pathways are formed by, for example, conductive paste, plating, and / or metal pins.

[0026] Furthermore, in the following description, the stacking direction of dielectric layers LY1 to LY8 in the dielectric substrate 110 is referred to as the "Z-axis direction", the direction perpendicular to the Z-axis direction and along the long side of the dielectric substrate 110 is referred to as the "X-axis direction", and the direction along the short side of the dielectric substrate 110 is referred to as the "Y-axis direction". In addition, the positive direction of the Z-axis in each figure is sometimes referred to as the upper side and the negative direction as the lower side.

[0027] The upper surface 111 (dielectric layer LY1) of the dielectric substrate 110 is provided with a directional mark DM for determining the orientation of the filter device 100. The lower surface 112 (dielectric layer LY8) of the dielectric substrate 110 is provided with external terminals (input terminal T1, output terminal T2, and ground terminal GND) for connecting the filter device 100 to an external machine. The input terminal T1, output terminal T2, and ground terminal GND are each a flat electrode, which are LGA (Land Grid Array) terminals regularly arranged on the lower surface 112 of the dielectric substrate 110. The "upper surface 111" and "lower surface 112" of Embodiment 1 correspond to the "first surface" and "second surface" in this disclosure, respectively.

[0028] If passed Figure 2As explained, the filter device 100 has a four-segment LC parallel resonator. More specifically, it includes: a resonator RC1 containing paths V1A, V1B and capacitor electrode P1; a resonator RC2 containing paths V2A, V2B and capacitor electrode P3; a resonator RC3 containing paths V3A, V3B and capacitor electrode P5; and a resonator RC4 containing paths V4A, V4B and capacitor electrode P6. Paths V1A, V1B, V2A, V2B, V3A, V3B, V4A, and V4B are each connected to a common electrode PC disposed on dielectric layer LY2. Additionally, paths V1B, V2B, V3B, and V4B are also connected to a ground electrode PG1 disposed on dielectric layer LY6. Ground electrode PG1 is connected to a ground electrode PG2 disposed on dielectric layer LY7 via multiple paths VG1. Ground electrode PG2 is connected to the ground terminal GND of dielectric layer LY8 via multiple paths VG2. The capacitor electrodes P1, P3, P5, and P6 are disposed on the dielectric layer LY5.

[0029] Input terminal T1 is connected to the planar electrode P0 disposed on dielectric layer LY7 via passage V0. Planar electrode P0 is connected to the common electrode PC disposed on dielectric layer LY2 via passage V1A. Passage V1A is also connected to capacitor electrode P1 disposed on dielectric layer LY5 and capacitor electrode P2 disposed on dielectric layer LY4. As described above, common electrode PC is connected to the ground electrode PG1 of dielectric layer LY6 via passage V1B.

[0030] When the dielectric substrate 110 is viewed from above in the stacking direction (Z-axis direction), a portion of the capacitor electrode P1 overlaps with the ground electrode PG1 of the dielectric layer LY6. The capacitor electrode P1 and the ground electrode PG1 together form a... Figure 2 The capacitor C1 is located within the capacitor. Additionally, it is constructed via pathways V1A and V1B and a common electrode PC. Figure 2 The inductors L1A and L1B are used in the circuit. That is, the resonator RC1 is formed by the capacitor electrode P1, the ground electrode PG1, the circuit V1A and V1B, and the common electrode PC.

[0031] Output terminal T2 is connected to the planar electrode P8 disposed on dielectric layer LY7 via passage V5. Planar electrode P8 is connected to the common electrode PC of dielectric layer LY2 via passage V2A. Passage V2A is also connected to capacitor electrode P3 disposed on dielectric layer LY5 and capacitor electrode P4 disposed on dielectric layer LY4. As described above, common electrode PC is connected to the ground electrode PG1 of dielectric layer LY6 via passage V2B.

[0032] When the dielectric substrate 110 is viewed from above, a portion of the capacitor electrode P3 overlaps with the ground electrode PG1 of the dielectric layer LY6. The capacitor electrode P3 and the ground electrode PG1 together form a... Figure 2 Capacitor C2 is located within this structure. Additionally, it is formed by connecting pathways V2A and V2B and a common electrode PC. Figure 2 The inductors L2A and L2B are used in the circuit. That is, the resonator RC2 is formed by the capacitor electrode P3, the ground electrode PG1, the circuit V2A and V2B, and the common electrode PC.

[0033] When the dielectric substrate 110 is viewed from above, the capacitor electrode P2 disposed on the dielectric layer LY4 and the capacitor electrode P5 disposed on the dielectric layer LY5 partially overlap. The capacitor electrode P2 and the capacitor electrode P5 constitute a... Figure 2 Capacitor C13 in the middle.

[0034] When the dielectric substrate 110 is viewed from above, a portion of the capacitor electrode P5 overlaps with the ground electrode PG1 of the dielectric layer LY6. The capacitor electrode P5 and the ground electrode PG1 together form a... Figure 2 The capacitor C3 is located in the middle. Additionally, capacitor electrode P5 is connected to the common electrode PC of dielectric layer LY2 via passage V3A. As described above, the common electrode PC is connected to the ground electrode PG1 via passage V3B. That is, passages V3A, V3B, and the common electrode PC constitute a... Figure 2 The inductors L3A and L3B are used in the circuit. That is, the resonator RC3 is formed by the capacitor electrode P5, the ground electrode PG1, the circuit V3A and V3B, and the common electrode PC.

[0035] When the dielectric substrate 110 is viewed from above, the capacitor electrode P4 disposed on the dielectric layer LY4 and the capacitor electrode P6 disposed on the dielectric layer LY5 partially overlap. The capacitor electrode P4 and the capacitor electrode P6 constitute a... Figure 2 Capacitor C24 in the middle.

[0036] When the dielectric substrate 110 is viewed from above, a portion of the capacitor electrode P6 overlaps with the ground electrode PG1 of the dielectric layer LY6. The capacitor electrode P6 and the ground electrode PG1 together form a... Figure 2 The capacitor C4 is located in the middle. Additionally, capacitor electrode P6 is connected to the common electrode PC of dielectric layer LY2 via passage V4A. As described above, the common electrode PC is connected to the ground electrode PG1 via passage V4B. That is, passages V4A, V4B, and the common electrode PC constitute a... Figure 2 The inductors L4A and L4B are used in the circuit. That is, the resonator RC4 is formed by the capacitor electrode P6, the ground electrode PG1, the circuit V4A and V4B, and the common electrode PC.

[0037] When the dielectric substrate 110 is viewed from above, capacitor electrodes P2 and P4 of dielectric layer LY4 each partially overlap with capacitor electrode P7 disposed on dielectric layer LY3. The capacitor electrodes P2, P4, and P7 constitute... Figure 2 Capacitor C12 in the middle.

[0038] In the following description, the paths V1A, V2A, V3A, and V4A in each resonator that are connected to the ground terminal GND via a capacitor are referred to as "first paths". In addition, the paths V1B, V2B, V3B, and V4B in each resonator that are connected to the ground terminal GND without passing through a capacitor are referred to as "second paths".

[0039] Figure 5 This is a top view of the common electrode PC disposed on the dielectric layer LY2 in the filter device 100. Viewed from the normal direction (Z-axis direction), the dielectric substrate 110 has a rectangular shape including long sides LL1, LL2 and short sides SL1, SL2. The long sides LL1, LL2 are along the X-axis, and the short sides SL1, SL2 are along the Y-axis. The long sides LL1, LL2 correspond to the "first long side" and "second long side" of this disclosure, respectively. The short sides SL1, SL2 correspond to the "first short side" and "second short side" of this disclosure, respectively.

[0040] The common electrode PC includes: a plate electrode PT1 connected to the pathways V1A and V1B constituting resonator RC1; a plate electrode PT2 connected to the pathways V2A and V2B constituting resonator RC2; and a plate electrode PT3 connected to the pathways V3A, V3B, V4A, and V4B constituting resonators RC3 and RC4. Plate electrodes PT1 and PT2 are strip-shaped electrodes extending along their short sides SL1 and SL2, respectively. Plate electrode PT3 is positioned between plate electrodes PT1 and PT2 and has a generally rectangular shape.

[0041] Plate electrode PT1 is connected to plate electrode PT3 via plate electrode PT4. Plate electrode PT4 extends along the long side LL1 from the negative Y-axis end of plate electrode PT1. Additionally, plate electrode PT2 is connected to plate electrode PT3 via plate electrode PT5. Plate electrode PT5 extends along the long side LL2 from the positive Y-axis end of plate electrode PT2. That is, the common electrode PC is approximately S-shaped, connecting the pathways V1A, V1B, V2A, V2B, V3A, V3B, V4A, and V4B to each other. In this way, the common electrode PC connects the four resonators RC1 to RC4 to each other.

[0042] The open end of the plate electrode PT1, i.e., the end in the positive Y-axis direction, is connected to the first path, or path V1A, of the resonator RC1. Additionally, the negative Y-axis end of the plate electrode PT1 is connected to the second path, or path V1B, of the resonator RC1. The open end of the plate electrode PT2, i.e., the end in the negative Y-axis direction, is connected to the first path, or path V2A, of the resonator RC2. Additionally, the positive Y-axis end of the plate electrode PT2 is connected to the second path, or path V2B, of the resonator RC2.

[0043] The planar electrode PT3 includes a protrusion B1 protruding from the positive Y-axis end of the side opposite to the planar electrode PT1 towards the planar electrode PT1, and a protrusion B2 protruding from the negative Y-axis end of the side opposite to the planar electrode PT2 towards the planar electrode PT1. In the planar electrode PT3, the connecting portion to the planar electrode PT4 is connected to the first path (path V3A) of the resonator RC3, and the protrusion B1 is connected to the second path (path V3B) of the resonator RC3. Furthermore, in the planar electrode PT3, the connecting portion to the planar electrode PT5 is connected to the first path (path V4A) of the resonator RC4, and the protrusion B2 is connected to the second path (path V4B) of the resonator RC4. That is, in the planar electrode PT3, the shortest path LN1 from path V3A to path V4A and the shortest path LN2 from path V3B to path V4B intersect.

[0044] In this way, by forming the paths of resonator RC3 and resonator RC4 in the planar electrode PT3 in opposite configurations, the directions of the electromagnetic fields generated by resonator RC3 and resonator RC4 become opposite. Therefore, compared to the case where the paths of the two resonators are configured the same, the magnetic coupling between resonators RC3 and RC4 is weakened. As a result, the electrical coupling between resonators RC1 and RC2 becomes dominant.

[0045] Typically, in a filter device with four resonators, the coupling between the first and fourth resonators is related to the generation of attenuation poles in the non-passband at a lower frequency side compared to the passband. If the electrical coupling between the resonators is more dominant than the magnetic coupling, there is a tendency for the attenuation at the attenuation poles to increase (deeper). Therefore, by configuring the path of resonator RC3 as opposite to that of resonator RC4, as in filter device 100, the attenuation at a lower frequency side compared to the passband can be increased compared to the case where the path configurations of resonator RC3 and RC4 are the same.

[0046] On the other hand, in a filter device with four resonators, the coupling between the first and third resonators, and between the second and fourth resonators, is related to the generation of attenuation poles in the non-passband at a higher frequency compared to the passband. If the magnetic coupling between the resonators is enhanced, there is a tendency for the attenuation at the attenuation poles to increase. In the filter device 100, the path configuration of resonator RC1 is the same as that of resonator RC4, and the path configuration of resonator RC2 is the same as that of resonator RC3. Therefore, in the coupling between resonators RC1 and RC4, and between resonators RC2 and RC3, magnetic coupling becomes more advantageous than electrical coupling. Thus, it is possible to increase the attenuation at the attenuation poles in the non-passband at a higher frequency compared to the passband.

[0047] Furthermore, in the filter device 100, for resonators RC3 and RC4, the shortest path LN1 from the path V3A of resonator RC3 to the path V4A of resonator RC4 intersects with the shortest path LN2 from the path V3B of resonator RC3 to the path V4B of resonator RC4. That is, the path configuration of resonator RC3 is the opposite of that of resonator RC4. As a result, resonators RC3 and RC4 with small inductance and large capacitance can be realized. In addition, the ratio of inductance and capacitance can be adjusted without changing the hollow core diameter of inductors L3A and L3B formed by paths V3A and V3B and the common electrode PC, and inductors L4A and L4B formed by paths V4A and V4B and the common electrode PC, thus enabling the construction of inductors with high Q values.

[0048] Furthermore, the coupling between the second and third resonators is related to the bandwidth in the passband; it is known that if the magnetic coupling between the resonators is enhanced, the bandwidth in the passband widens. In the filter device 100, since the path configuration of resonator RC3 is opposite to that of resonator RC4, the electromagnetic fields generated by the resonators cancel each other out, thus weakening the magnetic coupling. However, in the filter device 100, since the paths V3B and V4B, which are the second paths, are respectively arranged at the protrusions B1 and B2, the length of the shortest path LN2 between the second paths is greater than the length of the shortest path LN1 between the first paths. Based on this configuration, since magnetic coupling is more advantageous than electrical coupling between resonators RC3 and RC4, the reduction in bandwidth in the passband can be suppressed.

[0049] (Filter characteristics) The filter characteristics of the filter device 100 of Embodiment 1 will now be described with reference to the comparative example. Figure 6This diagram shows the resonator configuration of a comparative filter device 100X. The filter device 100X differs from the filter device 100 in that it lacks the common electrode PC of the dielectric layer LY2 of the filter device 100; otherwise, its configuration is the same as that of the filter device 100.

[0050] More specifically, in the filter device 100X, since there is no common electrode, the resonator RC1 connected to the input terminal T1 and the resonator RC2 connected to the output terminal T2 are not connected to the resonators RC3 and RC4, but are configured separately. In other words, the planar electrodes PT4 and PT5 in the common electrode PC of the filter device 100 are removed. Furthermore, in the filter device 100X, the planar electrode PT3X connected to the resonators RC3 and RC4 does not have protrusions B1 and B2 as in the planar electrode PT3 of the filter device 100, and the distance between the passages V3A and V4A is approximately the same as the distance between the passages V3B and V4B.

[0051] Figure 7 This is a diagram illustrating the transmission characteristics of the filter device 100 according to Embodiment 1. Figure 7 The insertion loss in the filter device 100 of Embodiment 1 and the comparative filter device 100X is shown. Figure 7 In the diagram, the solid line LN10 shows the insertion loss of filter device 100, and the dashed line LN11 shows the insertion loss of the comparative filter device 100X.

[0052] like Figure 7 As shown, in the filter device 100 of Embodiment 1, the bandwidth capable of achieving insertion loss of less than 3dB is wider than that in the case of filter device 100X. Furthermore, in the filter device 100 of Embodiment 1, the attenuation of the attenuation poles on the high-frequency side is significantly greater than that of the passband. This improves the attenuation characteristics on the high-frequency side compared to the passband.

[0053] Furthermore, regarding the attenuation characteristics on the low-frequency side compared to the passband, the frequency ratio of the two attenuation poles is closer to that on the passband side, thereby improving the steepness of the attenuation.

[0054] In this way, by forming the configuration of the filter device 100 of Embodiment 1, compared with the comparative filter device 100X, it is possible to improve the insertion loss and bandwidth in the passband while improving the attenuation characteristics in the non-passband.

[0055] (Modified Example) use Figures 8 to 14 This section describes a variation of the filter device 100 of Embodiment 1.

[0056] (1) Variation Example 1 In Variation 1, the configuration for further expanding the bandwidth of the passband is explained.

[0057] Figure 8 This is a top view of the common electrode PC1 in the filter device 100A of Modified Example 1. In the filter device 100A, the common electrode PC of the filter device 100 is replaced by the common electrode PC1. Elements in the filter device 100A that are repeated in the filter device 100 will not be described again.

[0058] Reference Figure 8 In the common electrode PC1 of filter device 100A, the shape of the planar electrode PT3A connected to the passages V3A, V3B, V4A, and V4B constituting resonators RC3 and RC4 differs from that of the planar electrode PT3 of filter device 100. More specifically, the protrusions B1A and B2A in planar electrode PT3A have an approximately L-shaped form. Protrusion B1A protrudes from the end of the side opposite to planar electrode PT1 in the positive Y-axis direction towards planar electrode PT1 in planar electrode PT3A, and then bends in the negative Y-axis direction. The passage V3B of resonator RC3 is connected to the open end of the bent protrusion B1A.

[0059] Similarly, the protrusion B2A protrudes from the negative Y-axis end of the side opposite to the plate electrode PT2 in the plate electrode PT3A, and then bends in the positive Y-axis direction. The path V4B of the resonator RC4 is connected to the open end of the bent protrusion B2A.

[0060] By forming such a configuration, the length of the shortest path connecting the path V3B of resonator RC3 and the path V4B of resonator RC4 along the plate electrode PT3A can be longer than that of filter device 100. As a result, compared with the case of filter device 100, the magnetic coupling between resonators RC3 and RC4 can be further enhanced, and thus the bandwidth of the passband can be widened.

[0061] (2) Variation Example 2 In Variation Example 2, the degree of coupling between resonators RC1 and RC2 is adjusted by adjusting the common electrode.

[0062] Figure 9 This is a top view of the common electrode PC2 in the filter device 100B of Modified Example 2. In the filter device 100B, the common electrode PC of the filter device 100 is replaced by the common electrode PC2. Elements in the filter device 100B that are repeated in the filter device 100 will not be described again.

[0063] Reference Figure 9In the common electrode PC2 of filter device 100B, the linewidths W1 of plate electrode PT4 and W2 of plate electrode PT5 are wider than those of the common electrode PC of filter device 100. By increasing the linewidths W1 of plate electrode PT4 and / or W2 of plate electrode PT5, the shortest distance (arrow AR1) between the path V1A connected to input terminal T1 and the path V2A connected to output terminal T2 can be shorter than in the case of filter device 100. That is, the magnetic coupling of resonators RC1 and RC2 can be enhanced, thereby adjusting the attenuation poles on the lower frequency side compared to the passband.

[0064] As described above, in the configuration of Embodiment 1, magnetic coupling is reduced by forming a configuration in which the path of resonator RC1 is opposite to that of resonator RC2. However, if it is desired to mitigate the degree of magnetic coupling, the desired magnetic coupling can be adjusted by increasing the linewidth W1 of the plate electrode PT4 and / or the linewidth W2 of the plate electrode PT5.

[0065] In addition, if the linewidth W1 of the planar electrode PT4 and / or the linewidth W2 of the planar electrode PT5 are increased, the inductance of the path from the input terminal T1 to the output terminal T2 becomes smaller, thus enabling adjustment of the return loss in the passband.

[0066] Furthermore, to ensure the symmetry of the filter characteristics, it is preferable that the linewidth W1 of the planar electrode PT4 and the linewidth W2 of the planar electrode PT5 are the same (W1 = W2). Alternatively, if it is desired to reduce magnetic coupling, the linewidth W1 of the planar electrode PT4 and / or the linewidth W2 of the planar electrode PT5 may be narrower than that in the case of the filter device 100.

[0067] (3) Variation Example 3 In Modification 2, the configuration for adjusting the linewidth of the plate electrode PT4 and / or the linewidth of the plate electrode PT5 is described. In Modification 3, the configuration for changing not only the linewidth of the plate electrode PT4 and / or the linewidth of the plate electrode PT5, but also the connection position of the plate electrodes PT4 and / or PT5 is described.

[0068] Figure 10 This is a top view of the common electrode PC3 in the filter device 100C of Modified Example 3. In the filter device 100C, the common electrode PC of the filter device 100 is replaced by the common electrode PC3. Elements in the filter device 100C that are repeated in the filter device 100 will not be described again.

[0069] Reference Figure 10In the common electrode PC3 of the filter device 100C, not only are the linewidths of the plate electrodes PT4 and PT5 changed, but the connection positions of the plate electrode PT1 from the negative Y-axis end to the plate electrode PT4 and / or the connection positions of the plate electrode PT2 from the positive Y-axis end to the plate electrode PT5 are also changed.

[0070] In this way, by changing the linewidth and connection position of the planar electrodes PT4 and PT5, the magnetic coupling between resonators RC1 and RC2, and the inductance value of the path from input terminal T1 to output terminal T2, can be individually adjusted. Therefore, the echo characteristics and attenuation poles on the lower frequency side compared to the passband can be adjusted.

[0071] (4) Variation Example 4 In Variation Example 4, the configuration of adjusting the distance between the paths in resonators RC3 and RC4 is explained.

[0072] Figure 11 This is a top view of the common electrode PC4 in the filter device 100D of Modified Example 4. In the filter device 100D, the common electrode PC of the filter device 100 is replaced by the common electrode PC4. Elements in the filter device 100D that are repeated in the filter device 100 will not be described again.

[0073] Reference Figure 11 In the common electrode PC4 of the filter device 100D, in the planar electrode PT3D connected to the resonators RC3 and RC4, cut-off portions NC1 to NC4 are provided along each edge of the dielectric substrate 110. More specifically, a cut-off portion NC1 is provided between the passage V3A and the passage V4B along the long side LL1 of the planar electrode PT3D. Additionally, a cut-off portion NC2 is provided between the passage V3B and the passage V4A along the long side LL2 of the planar electrode PT3D.

[0074] Similarly, in the planar electrode PT3D, a cut-off portion NC3 is provided between the passages V3A and V3B along the short side SL1, and a cut-off portion NC4 is provided between the passages V4A and V4B along the short side SL2.

[0075] By setting the cut-off section as described above, the path lengths between the resonators RC3 and RC4 in the planar electrode PT3D can be adjusted, thereby adjusting the inductance between the paths and the magnetic coupling between the resonators. Therefore, the bandwidth of the passband and / or the attenuation characteristics in the non-passband can be adjusted.

[0076] (5) Variation Example 5 In Modification 5, an example is shown where the common electrode is composed of a planar electrode disposed in multiple dielectric layers.

[0077] Figure 12 This is a partial perspective view of the common electrode PC5 in the filter device 100E of Modified Example 5. Furthermore, Figure 12 The dielectric substrate 110 is omitted in the text.

[0078] Reference Figure 12 The common electrode PC5 in the filter device 100E includes electrode PC53 disposed in the first layer and electrodes PC51 and PC52 disposed in the second layer. Electrode PC51 corresponds to the planar electrodes PT1 and PT4 in the common electrode PC of the filter device 100. Electrode PC52 corresponds to the planar electrodes PT2 and PT5 in the common electrode PC. Electrode PC53 corresponds to the planar electrode PT3 in the common electrode PC.

[0079] Electrodes PC51 and PC53 are connected via path V3A of resonator RC3. Additionally, electrodes PC52 and PC53 are connected via path V4A of resonator RC4.

[0080] By forming such a configuration, the magnetic coupling between resonators RC1 and RC2, between resonators RC1 and RC4, and between resonators RC2 and RC3 can be weakened because the path between resonators RC1 and RC2 increases the length of the path between electrodes PC51 and PC53 and between electrodes PC52 and PC53.

[0081] (6) Variation Example 6 In Modification 6, another example is described where the common electrode is composed of a planar electrode disposed in multiple dielectric layers.

[0082] Figure 13 This is a partial perspective view of the common electrode PC6 in the filter device 100F of Modified Example 6. Furthermore, Figure 13 The dielectric substrate 110 is omitted in the text.

[0083] Reference Figure 13 The common electrode PC6 in the filter device 100F includes electrode PC61 disposed in the first layer and electrodes PC62 and PC63 disposed in the second layer. Electrode PC61 corresponds to the portion of the common electrode PC excluding protrusions B1 and B2. Electrode PC62 corresponds to the portion of protrusion B1 in the common electrode PC, and electrode PC63 corresponds to the portion of protrusion B2 in the common electrode PC.

[0084] One end of electrode PC62 is connected to electrode PC61 via passage V3B1. The other end of electrode PC62 is connected to ground terminal GND via passage V3B2. One end of electrode PC63 is connected to electrode PC61 via passage V4B1. The other end of electrode PC63 is connected to ground terminal GND via passage V4B2.

[0085] By forming this configuration, the path length from the connection point of resonator RC3 and ground terminal GND to the connection point of resonator RC4 and ground terminal GND is increased, thereby improving the magnetic coupling between resonators RC3 and RC4. Therefore, the bandwidth of the passband can be expanded.

[0086] (7) Variation Example 7 In Modification 7, a configuration is described that reduces the influence of other machines located outside the filter device by arranging a shielding electrode on the upper surface side of the common electrode.

[0087] Figure 14 This is a perspective view of the shielding electrode PG3 portion in the filter device 100G of Modified Example 7. Furthermore, Figure 14 The dielectric substrate 110 is omitted in the text.

[0088] Reference Figure 14 In the filter device 100G, a shielding electrode PG3 is disposed on the upper surface 111 side compared to the dielectric layer LY2 on which the common electrode PC is disposed. The shielding electrode PG3 has a rectangular shape and overlaps with the common electrode PC when viewed from the normal direction of the dielectric substrate 110. The shielding electrode PG3 is connected to vias V1B, V2B, V3B, and V4B. That is, the shielding electrode PG3 is at the same potential as the ground terminal GND and the ground electrode PG1.

[0089] Without the shielding electrode PG3, the current flowing through the common electrode PC propagates through the shield of a machine or component located outside the filter device, potentially becoming noise in the filter device's transmitted signal. By configuring the shielding electrode PG3, coupling between the common electrode PC and the external machine is prevented, thus suppressing noise generation.

[0090] [Implementation Method 2] In Embodiment 2, the configuration of the first and second paths in resonators RC3 and RC4 is described as the opposite of that in the filter device 100 of Embodiment 1.

[0091] Figure 15 This is a top view of the common electrode PC in the filter device 100H according to Embodiment 2. The common electrode PC in the filter device 100H has the same shape as the common electrode in the filter device 100.

[0092] In the filter device 100H, the path V3A of the resonator RC3 is disposed in the protrusion B1, and the path V3B of the resonator RC3 is disposed in the connection portion of the plate electrode PT3 that connects to the plate electrode PT4. Furthermore, the path V4A of the resonator RC4 is disposed in the protrusion B2, and the path V4B of the resonator RC4 is disposed in the connection portion of the plate electrode PT3 that connects to the plate electrode PT5.

[0093] In filter device 100H, the shortest path from path V3A to path V4A and the shortest path from path V3B to path V4B also intersect, but Figure 15 In the configuration of the paths of resonators RC3 and RC4, the shortest path from path V3A to path V4A is longer than the shortest path from path V3B to path V4B. Therefore, the magnetic coupling between resonators RC3 and RC4 is enhanced compared to the filter device 100. Furthermore, when it is necessary to reduce the magnetic coupling between resonators RC3 and RC4, path V3B is positioned after moving along the plate electrode PT4 towards the resonator RC1 side, and path V4B is positioned after moving along the plate electrode PT5 towards the resonator RC2 side. By adjusting the positions of paths V3B and V4B in this way, the magnetic coupling between resonators RC3 and RC4 can be adjusted.

[0094] Furthermore, since the path V1B of resonator RC1 and the path V3B of resonator RC3 are arranged adjacent to each other along the plate electrode, it is also possible to... Figure 15 The paths V1B and V3B can be shared as shown by the dashed path V13B. By moving path V1B towards the plate electrode PT3, the inductance of resonator RC1 can be increased. Similarly, the paths V2B and V4B of resonator RC2 and resonator RC4 can also be shared as shown by the dashed path V24B.

[0095] In filter device 100H, the paths of resonators RC1 and RC4 are configured opposite to each other, and the paths of resonators RC2 and RC3 are configured opposite to each other. Therefore, the magnetic coupling between resonators RC1 and RC4 and the magnetic coupling between resonators RC2 and RC3 are weaker than those in filter device 100 of Embodiment 1.

[0096] In filter device 100H, the paths of resonators RC1 and RC3 are configured identically, and the paths of resonators RC2 and RC4 are also configured identically. Therefore, the magnetic coupling between resonators RC1 and RC3, and between resonators RC2 and RC4, becomes stronger than that of filter device 100 in Embodiment 1. Generally, the magnetic coupling between the first and second resonators, and between the third and fourth resonators, is related to the steepness of attenuation on the low-frequency side of the passband. Therefore, the configuration of filter device 100H is suitable for situations where a high attenuation steepness near the low-frequency side of the passband is desired.

[0097] [Implementation Method 3] In Embodiment 3, the configuration of the first and second paths in resonators RC1 and RC2 is described as the opposite of that in the filter device 100 of Embodiment 1.

[0098] Figure 16 This is a top view of the common electrode PC in the filter device 100J according to Embodiment 3. The common electrode PC in the filter device 100J has the same shape as the common electrode of the filter device 100.

[0099] In the filter device 100J, the path V1B of resonator RC1 is disposed on the open end side of the plate electrode PT1, and the path V1A of resonator RC1 is disposed at the connection portion connected to the plate electrode PT4. Additionally, the path V2B of resonator RC2 is disposed on the open end side of the plate electrode PT2, and the path V2A of resonator RC2 is disposed at the connection portion connected to the plate electrode PT5.

[0100] In the configuration of filter device 100J, the resonators RC3 and RC4 are configured the same as in filter device 100 of Embodiment 1. Therefore, the same effect can be achieved in terms of bandwidth as filter device 100. Furthermore, the path V1A connected to the input terminal T1 and the path V2A connected to the output terminal T2 are positioned at the ends opposite to the open ends of the planar electrodes PT1 and PT2. Therefore, the path length from the input terminal T1 to the output terminal T2 is shorter than that of filter device 100. Thus, the insertion loss in the bandwidth can be reduced compared to filter device 100.

[0101] Furthermore, in filter device 100J, similarly to filter device 100H of Embodiment 2, the configurations of the paths for resonators RC1 and RC4, and the paths for resonators RC2 and RC3, are reversed. However, the configurations of the paths for resonators RC1 and RC3, and the paths for resonators RC2 and RC4, are the same. Therefore, compared to filter device 100 of Embodiment 1, the magnetic coupling between resonators RC1 and RC4, and the magnetic coupling between resonators RC2 and RC3, are weakened, but the magnetic coupling between resonators RC1 and RC3, and the magnetic coupling between resonators RC2 and RC4, become stronger than those in filter device 100 of Embodiment 1. The configuration of filter device 100J is suitable for situations where a steeper attenuation near the low-frequency side of the passband is desired compared to filter device 100H of Embodiment 2.

[0102] [Implementation Method 4] In Embodiment 4, a configuration is described in which no protrusion is provided in the planar electrode connected to the passages V3A, V3B, V4A, V4B constituting the resonators RC3 and RC4 in the common electrode.

[0103] Figure 17 This is a top view of the common electrode PC7 in the filter device 100K according to Embodiment 4. In the common electrode PC7 of the filter device 100K, the flat plate electrode PT3K connected to the resonators RC3 and RC4 has a rectangular shape and does not have protrusions B1 and B2 as in the filter device 100 of Embodiment 1.

[0104] In the common electrode PC7, path V3B is positioned at the positive Y-axis end along the short side SL1 of the dielectric substrate 110, and path V4B is positioned at the negative Y-axis end along the short side SL2 of the dielectric substrate 110. In the filter device 100K, the shortest path LN1K from path V3A to path V4A and the shortest path LN2K from path V3B to path V4B along the planar electrode PT3K intersect.

[0105] In filter device 100K, since no protrusion is provided on the planar electrode PT3K, the shortest path LN2K from path V3B to path V4B is shorter than the shortest path LN2 from path V3B to path V4B in filter device 100. Therefore, since the magnetic coupling between resonators RC3 and RC4 is enhanced compared to filter device 100, although the bandwidth of the passband is slightly narrower, the insertion loss of the passband can be reduced due to the absence of the protrusion.

[0106] It should be considered that all aspects of the embodiments disclosed herein are merely illustrative and not limiting. The scope of the invention is not shown by the above description of the embodiments, but is indicated by the claims, which are intended to include all modifications in the same sense and scope as the claims. Explanation of the label

[0107] 10 Communication device; 12 Antenna; 20 High-frequency front-end circuit; 22, 28 Bandpass filters; 24 Amplifier; 26 Attenuator; 30 Mixer; 32 Local oscillator; 40 D / A converter; 50 RF circuit; 100, 100A~100H, 100J, 100K, 100X filter devices; 110 Dielectric substrate; 111 Upper surface; 112 Lower surface; B1, B1A, B2, B2A protrusions; C1~C4, C12, C13, C24 Capacitors; DM Directional mark; GND ground terminal; L1A~L4A, L1B~L4B Inductors; LL1, LL2 Long sides; LY1~LY8 Dielectric layers; N 1A~N4A, N1B~N4B connection nodes; NC1~NC4 cut-off sections; P0, P8, PT1~PT5, PT3A, PT3D, PT3K, PT3X plate electrodes; P1~P7 capacitor electrodes; PC1~PC7 common electrodes; PC51~PC53, PC61~PC63 electrodes; PG1, PG2 ground electrodes; PG3 shielding electrode; RC1~RC4 resonators; SL1, SL2 short sides; T1 input terminal; T2 output terminal; V0, V1A~V4A, V1B~V4B, V3B1, V3B2, V3A, V3B1, V13B, V24B, VG1, VG2 pathways.

Claims

1. A filter device comprising: A dielectric substrate having a first surface and a second surface; An input terminal, an output terminal, and a ground terminal are disposed on the second side of the dielectric substrate; A common electrode disposed inside the dielectric substrate; as well as The first resonator, the second resonator, the third resonator, and the fourth resonator are each connected to the common electrode and the grounding terminal. The first resonator is connected to the input terminal. The second resonator is connected to the output terminal. The third resonator and the fourth resonator are disposed between the first resonator and the second resonator. The first resonator, the second resonator, the third resonator, and the fourth resonator each comprise: Capacitor; The first path has one end connected to the common electrode and the other end connected to the ground terminal via the capacitor. as well as The second path has one end connected to the common electrode, and the other end connected to the ground terminal without passing through the capacitor. In the common electrode, the direction of the first resonator from the first path to the second path is opposite to the direction of the second resonator from the first path to the second path. The shortest path along the common electrode from the first path of the third resonator to the first path of the fourth resonator intersects with the shortest path along the common electrode from the second path of the third resonator to the second path of the fourth resonator.

2. The filter device according to claim 1, wherein, The common electrode includes: The first electrode is connected to the first path and the second path of the first resonator; The second electrode is connected to the first and second paths of the second resonator; A third electrode connected to the first and second paths of the third and fourth resonators; A fourth electrode connecting the first electrode and the third electrode; and The fifth electrode connects the second electrode and the third electrode. The third electrode comprises: The first protrusion protruding towards the first electrode; and A second protrusion extending toward the second electrode. The second path of the third resonator is connected to the first protrusion. The second path of the fourth resonator is connected to the second protrusion.

3. The filter device according to claim 2, wherein, The shortest path along the common electrode from the first path of the third resonator to the first path of the fourth resonator is shorter than the shortest path along the common electrode from the second path of the third resonator to the second path of the fourth resonator.

4. The filter device according to claim 1, wherein, The common electrode includes: The first electrode is connected to the first path and the second path of the first resonator; The second electrode is connected to the first and second paths of the second resonator; A third electrode connected to the first and second paths of the third and fourth resonators; A fourth electrode connecting the first electrode and the third electrode; and The fifth electrode connects the second electrode and the third electrode. The third electrode comprises: The first protrusion protruding towards the first electrode; and A second protrusion extending toward the second electrode. The first path of the third resonator is connected to the first protrusion. The first path of the fourth resonator is connected to the second protrusion.

5. The filter device according to any one of claims 2 to 4, wherein, The first protrusion and the second protrusion are approximately L-shaped.

6. The filter device according to any one of claims 2 to 4, wherein, The fourth electrode is connected in the first electrode at a position between the first path and the second path of the first resonator.

7. The filter device according to any one of claims 2 to 4, wherein, Viewed from the first surface, the dielectric substrate has a rectangular shape including a first short side, a second short side, a first long side, and a second long side. The first electrode is a strip-shaped electrode arranged along the first short side. The second electrode is a strip-shaped electrode arranged along the second short side. The fourth electrode extends along the first long side and connects to the end of the first electrode on the first long side. The fifth electrode extends along the second long side and is connected to the end of the second electrode on the second long side.

8. The filter device according to claim 7, wherein, At least one of the portions of the third electrode along the first short side, the second short side, the first long side, and the second long side is formed with a cut-off portion.

9. The filter device according to any one of claims 2 to 4, wherein, The third electrode is disposed at a position different from the first electrode, the second electrode, the fourth electrode, and the fifth electrode in the extension direction of each passage in the dielectric substrate.

10. The filter device according to any one of claims 2 to 4, wherein, The first protrusion and the second protrusion are positioned at locations different from other portions of the third electrode in the extension direction of each passage in the dielectric substrate.

11. The filter device according to any one of claims 1 to 4, wherein, It also includes a shielding electrode, which, compared to the common electrode, is disposed on the first surface side of the dielectric substrate and connected to the grounding terminal. When viewed from the first surface of the dielectric substrate, the shielding electrode overlaps with the common electrode.

12. The filter device according to any one of claims 1 to 4, wherein, The filter device is a bandpass filter.

13. A high-frequency front-end circuit comprising the filter device according to any one of claims 1 to 12.

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