An integrated passive filter circuit

Abstract

This application provides an integrated passive filter circuit, including two first filter units, two second filter units, and a third filter unit. Each filter unit includes a main path and a grounding element connected to the main path. The two second filter units are symmetrical with respect to the third filter unit. The two first filter units are symmetrical with respect to the two second and third filter units. The end of the main path of the first filter unit serves as the port of the integrated passive filter circuit. The third filter unit includes two parallel and different grounding elements. The solution provided in this application employs a semi-symmetrical structure design. The symmetrical structure on both sides effectively improves the consistency at both ends of the filter and simplifies the adjustment of the reflection characteristics on both sides of the device. The asymmetrical structure in the middle improves out-of-band rejection on both sides, reduces the number of devices, and lowers device insertion loss.

Description

Technical Field

[0001] This application relates to the field of filter circuit technology, specifically to an integrated passive filter circuit. Background Technology

[0002] With the continuous upgrading and iteration of communication technologies, signal transmission rates are also constantly improving. In wireless communication, from the early 2G era to the current 5G era, communication frequencies have entered the GHz range, and bandwidth has also increased rapidly. New communication technologies have also placed new demands on the overall communication link, and the miniaturization and high performance of components in the link have become the mainstream development trend.

[0003] In the process of transmitting signals using specific frequency bands, higher frequency bands have wider frequency bandwidths, which can transmit signals over a wider frequency range and increase the information transmitted by the signal. Therefore, wide bandwidth has become a core element in radio frequency links.

[0004] In radio frequency (RF) transmission, interference from other noise is inevitable. Filters, which select signals within a specific frequency range to ensure effective signal transmission, are a crucial component of the link. Filters come in many different types and structures, commonly including acoustic filters and LC (inductor-capacitor) filters.

[0005] Acoustic filters filter through material resonance with specific thickness and structure, and have a high roll-off characteristic (the rate at which the amplitude response of the filter transitions from the passband to the stopband near the cutoff frequency). However, due to the limitations of its material properties and manufacturing process, it cannot have a wide bandwidth characteristic.

[0006] Currently, in applications requiring wide bandwidth, LC filters are typically chosen. Inductors in LC filters have the characteristic of passing low frequencies and blocking high frequencies, while capacitors have the characteristic of passing high frequencies and blocking low frequencies. Series / parallel combinations of capacitors and inductors can achieve various filter characteristics. How to develop a bandpass filter circuit with wide bandwidth, high out-of-band rejection, and low insertion loss (the additional power loss caused by inserting the signal into the filter) using the LC architecture is a problem that needs to be solved. Summary of the Invention

[0007] To address or improve the problems existing in the prior art, this application provides an integrated passive filter circuit, which includes two first filter units, two second filter units, and a third filter unit. Each of the first, second, and third filter units includes a main circuit and a grounding element connected to the main circuit. The main circuits of the two second filter units are respectively connected to both ends of the main circuit of the third filter unit, and the two second filter units are symmetrical with respect to the third filter unit. The main circuits of the two first filter units are respectively connected to the main circuits of the two second filter units, and the two first filter units are symmetrical with respect to the two second and third filter units. The end of the main circuit of the first filter unit serves as a port of the integrated passive filter circuit. The third filter unit includes two parallel grounding elements of different types.

[0008] In the aforementioned scheme, the two sides of the circuit structure, namely the two first filter units and the two second filter units, are symmetrical structures, which is beneficial to achieving better roll-off characteristics and out-of-band rejection. At the same time, as a reciprocal device (signal transmission characteristics are independent of direction), the aforementioned symmetrical structure allows the ports at the main end of the two first filter units to be interchanged.

[0009] The third filter unit includes two parallel and different grounding elements. Therefore, the third filter unit has an asymmetrical circuit structure. Since the third filter unit is located in the middle part of the circuit structure, its asymmetrical structure can avoid occupying too much space and also avoid the mutual interference between the two inductors that may exist in the symmetrical structure.

[0010] Overall, the integrated passive filter circuit provided by the aforementioned solution features a semi-symmetrical structure design. The symmetrical structure on both sides (the first and second filter units) effectively improves the consistency at both ends of the filter circuit, enhances out-of-band rejection and roll-off characteristics on both sides, and reduces the difference in reflection parameters at the device ports. The asymmetrical structure in the middle (the third unit) improves out-of-band rejection on both sides, reduces the number of devices, and lowers insertion loss, bringing it closer to zero. Furthermore, by adopting the aforementioned semi-symmetrical circuit topology design, subsequent layout design can be carried out symmetrically for further optimization, reducing the difficulty of structural design and electromagnetic simulation.

[0011] Optionally, the first filtering unit includes: a first capacitor, one end of which is connected to a port and the other end is grounded; a first inductor and a second capacitor connected in parallel, which are disposed in the main circuit of the first filtering unit.

[0012] In the aforementioned scheme, the two symmetrically arranged first filter units have higher roll-off and out-of-band rejection, better transmission characteristics in the passband, and stronger signal reflection in the out-of-band frequency band. In addition, the two symmetrical first filter units are also conducive to the consistency of the signal reflection curves at both ports.

[0013] Optionally, the second filter unit includes: a third capacitor, one end of which is connected to the main circuit of the adjacent first filter unit and the other end is grounded; a fourth capacitor, which is disposed in the main circuit of the second filter unit; a fifth capacitor, one end of which is connected to the main circuit of the adjacent third filter unit and the other end is grounded; and a second inductor, one end of which is connected to the main circuit of the adjacent third filter unit and the other end is grounded.

[0014] In the aforementioned scheme, the fourth capacitor on the main circuit of the second filter unit is used to adjust the impedance matching of the main circuit of the unit and reduce insertion loss. Similar to the first filter unit, the second filter unit adopts a symmetrical structure, which is beneficial to increasing the overall roll-off and out-of-band rejection effect.

[0015] Optionally, the third filter unit includes: two sixth capacitors connected in series in the main circuit of the third filter unit; a seventh capacitor, an eighth capacitor, and a third inductor, wherein one end of the seventh capacitor is connected to the connection node of the two sixth capacitors, and the eighth capacitor and the third inductor connected in parallel are connected between the other end of the seventh capacitor and the ground terminal.

[0016] The third filter unit includes two sixth capacitors connected in series on the main line, and a ground branch connected between the two sixth capacitors. The ground branch contains a seventh capacitor connected in series, and an eighth capacitor and a third inductor connected in parallel. This structure adds a new transmission pole in the passband, which is beneficial to increase the passband width and reduce transmission loss.

[0017] Optionally, the capacitance value c1 of the first capacitor and the capacitance value c2 of the second capacitor satisfy the following relationship: 1:1 ≤ c2:c1 < 2:1.

[0018] In the first filtering unit, a high-frequency zero on the right side of the passband is achieved by connecting the second capacitor and the first inductor in parallel. The high-frequency signal is transmitted to the ground plane through the first capacitor on the ground branch, which increases the suppression of the high-frequency signal. Therefore, among all capacitors, the capacitance of the first capacitor is set to be the smallest, equal to the capacitance of the second capacitor, or not less than 1 / 2 of the capacitance of the second capacitor.

[0019] Optionally, the capacitance value c2 of the second capacitor and the capacitance value c4 of the fourth capacitor satisfy the following relationship: c4:c2>4:1.

[0020] In the aforementioned scheme, the fourth capacitor is used to adjust the impedance matching of the main circuit and reduce insertion loss. Therefore, the capacitance value of the fourth capacitor is optimized according to the impedance matching to make its capacitance value as large as possible. For example, compared with the capacitance value of the second capacitor, it has a ratio of c4:c2>4:1.

[0021] Optionally, the capacitance value c1 of the first capacitor and the capacitance value c8 of the eighth capacitor satisfy the following relationship: 0.5≤c8:c1≤2.

[0022] In the aforementioned scheme, the eighth capacitor is mainly used to adjust the high-frequency out-of-band suppression, so its capacitance value is relatively small, usually in the pF level, generally close to that of the first capacitor, and the ratio between the two is generally 0.5 to 2 times, preferably close to 1:1.

[0023] Optionally, the capacitance value c1 of the first capacitor is equal to the capacitance value c8 of the eighth capacitor.

[0024] Optionally, the inductance value l2 of the second inductor and the inductance value l3 of the third inductor satisfy the following relationship: 1.5:1 ≤ l3:l2 < 4:1.

[0025] Optionally, the inductance values ​​l1 of the first inductor and l2 of the second inductor satisfy the following relationship: 1:0.5≥l1:l2>1:2.

[0026] In summary, the integrated passive filter circuit provided in this application adopts a semi-symmetrical structure design. The symmetrical structure on both sides can effectively improve the consistency at both ends of the filter and simplify the adjustment of the reflection characteristics on both sides of the device. The asymmetrical structure in the middle can improve the out-of-band rejection on both sides, reduce the number of devices, reduce device insertion loss, and make the insertion loss approach 0.

[0027] More specifically, this bandpass filter circuit can effectively achieve bandpass filtering with a center frequency in the GHz range, featuring wide bandwidth, high out-of-band rejection, and high roll-off. This circuit can be widely used in RF transceiver links and communication platforms; its high out-of-band rejection over a wide frequency range effectively filters various types of noise and resonant waves. Furthermore, the fewer circuit components significantly reduce product size, enabling this integrated passive filter circuit to be widely used in various wireless communication scenarios, such as mobile phones, laptops, and other electronic devices. Attached Figure Description

[0028] Figure 1 This is a circuit schematic diagram of the integrated passive filter circuit provided in the embodiments of this application;

[0029] Figure 2 This is a characteristic curve diagram of the integrated passive filter circuit provided in the embodiments of this application;

[0030] Figure 3 This is a characteristic curve diagram of the first filter unit in the integrated passive filter circuit provided in the embodiments of this application;

[0031] Figure 4 This application provides a comparison of the S21 (transmission coefficient between two ports) characteristics of the single-circuit structure and the symmetrical circuit structure of the first filter unit in the integrated passive filter circuit provided in this embodiment.

[0032] Figure 5 This application provides a comparison of the S11 (reflection coefficient of one port) characteristics of the single-circuit structure and the symmetrical circuit structure of the first filter unit in the integrated passive filter circuit.

[0033] Figure 6 This is a characteristic curve diagram of the second filter unit in the integrated passive filter circuit provided in the embodiments of this application;

[0034] Figure 7 This is a characteristic curve of the third filter unit in the integrated passive filter circuit provided in this application embodiment.

[0035] The image is labeled as follows:

[0036] 100: First filtering unit, 200: Second filtering unit, 300: Third filtering unit;

[0037] C1 to C8: First to eighth capacitors; L1 to L3: First to third inductors;

[0038] P1: First port; P2: Second port. Detailed Implementation

[0039] In this specification, it will also be understood that when a component is referred to as being "connected to" other components relative to them, such as "connected to" other components, the component may be directly connected to or directly coupled to the component, or there may be an intermediary third component; in addition, in the embodiments of this application, "connection" mainly refers to circuit connection.

[0040] This application will now be described more fully below with reference to the accompanying drawings. However, this application can be implemented in many different ways and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided herein to make this application more detailed and complete, and to fully convey the scope of this application to those skilled in the art. The same reference numerals denote the same objects throughout the drawings.

[0041] In order to address the problems existing in the prior art, the embodiments of this application aim to provide a bandpass integrated passive filter circuit with wide bandwidth, high out-of-band rejection, and low insertion loss, which includes two first filter units 100, two second filter units 200, and a third filter unit 300.

[0042] by Figure 1 Taking the circuit schematic shown as an example, the middle position of the circuit structure is the third filter unit 300. On both sides of the third filter unit 300, two second filter units 200 are symmetrically arranged, and on the outside of the two second filter units 200, two first filter units 100 are symmetrically arranged.

[0043] In the embodiments, two filter units that are topologically symmetrical to each other, such as two first filter units 100 or two second filter units 200, have symmetrical elements, or in other words, they are mirror images of each other.

[0044] Specifically, the first filter unit 100, the second filter unit 200, and the third filter unit 300 each include a main path and a grounding element connected to the main path. In another embodiment, the first filter unit 100, the second filter unit 200, and the third filter unit 300 each include a main path and a grounding branch connected to the main path, which includes the aforementioned grounding element.

[0045] like Figure 1 As shown, the main circuits of the first filter unit 100, the second filter unit 200, and the third filter unit 300 are connected in series to form a... Figure 1 The horizontal line between the first port P1 and the second port P2 in the middle has at least one capacitor connected in series on the main line of each filter unit.

[0046] In another description, multiple capacitors C2, C4, and C6 are connected in series between the first port P1 and the second port P2, forming a main circuit. In an embodiment, the capacitors connected in series in the main circuit may also be connected in parallel with other components, such as... Figure 1 As shown, an inductor L1 is connected in parallel with capacitor C2 in the first filter unit 100.

[0047] The main paths of the two second filter units 200 are respectively connected to both ends of the main path of the third filter unit 300. The two second filter units 200 are symmetrical with respect to the third filter unit 300, as shown below. Figure 1 In the circuit topology shown, two second filter units 200 are symmetrically arranged on the left and right sides of the third filter unit 300.

[0048] The main paths of the two first filter units 100 are respectively connected to the main paths of the two second filter units 200, and the two first filter units 100 are symmetrical with respect to the two second filter units 200 and the third filter unit 300; for example Figure 1 In the circuit topology shown, two first filter units 100 are symmetrically arranged on the left and right outermost sides of the overall circuit structure, and the main path of the first filter unit 100 is connected to the main path of the second filter unit 200 on the same side.

[0049] The main output terminal of the first filter unit 100 serves as the port for an integrated passive filter circuit; specifically, as shown below... Figure 1 As shown in the figure, the left end of the main path of the first filter unit 100 on the left is the first port P1, and the right end of the main path of the first filter unit 100 on the right is the second port P2.

[0050] In the embodiment, the first port P1 and the second port P2 are reciprocal, that is, the first port P1 can be used as the input terminal of the circuit, and the corresponding second port P2 can be used as the output terminal of the circuit; or conversely, the second port P2 can be used as the input terminal of the circuit, and the corresponding first port P1 can be used as the output terminal of the circuit.

[0051] The third filter unit 300 includes two parallel and different grounding elements. For example Figure 1 As shown, the third filter unit 300 is provided with an eighth capacitor C8 and a third capacitor L3 connected between the seventh capacitor C7 and GND, and the eighth capacitor C8 and the third capacitor L3 are connected in parallel, which makes the third filter unit 300 have an asymmetrical topology.

[0052] In the aforementioned embodiments, the symmetrical design of the two first filter units 100 and the two second filter units 200 is beneficial for the actual manufacturing and use of filter products with reciprocal structures.

[0053] In a preferred embodiment, such as Figure 1 As shown, the first filter unit 100 specifically includes: a first capacitor C1, a first inductor L1, and a second capacitor C2. The first capacitor C1 is a grounding element, with one end connected to the first port P1 or the second port P2, and the other end grounded to GND. The first inductor L1 and the second capacitor C2 connected in parallel form a resonant unit, which is located in the main circuit of the first filter unit 100.

[0054] Based on the internal circuit structure of the first filter unit 100, the circuit characteristic curve of the first filter unit 100 is as follows: Figure 3 As shown, the second capacitor C2 and the first inductor L1 in the first filter unit 100 are connected in parallel to achieve the high-frequency zero on the right side of the passband, that is... Figure 3 The S21 curve has a dip on the right side of the passband; and the first capacitor C1, located in the grounding branch, can ground the high-frequency signal, thus enhancing the suppression of the high-frequency signal.

[0055] In the foregoing embodiments, the S21 curve of a single first filter unit is as follows: Figure 4 As shown by the dashed line, the S21 curves of the two first filter units arranged symmetrically and in series are as follows: Figure 4 As shown by the solid line in the figure, it can be seen that the S21 curves of the two symmetrical first filter units have a higher slope and stronger out-of-band suppression.

[0056] like Figure 5The figure shows the S11 curves of a single first filter unit and two first filter units symmetrically connected in series. It can be seen that the S11 characteristic of the symmetrical structure, represented by the solid line, exhibits a significant dip within the passband range of 1.6 GHz to 2.0 GHz in this embodiment, indicating good input port matching and better transmission characteristics within the passband. Outside the passband (high-frequency region, right side of the figure), the S11 of the symmetrical structure is closer to 0 dB than that of the single circuit, resulting in stronger signal reflection in the out-of-passband frequency band. Furthermore, the symmetrical structure of the two first filter units also contributes to the consistency of the signal reflection curves at ports P1 and P2.

[0057] In a preferred embodiment, such as Figure 1 As shown, the second filter unit 200 includes a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, and a second inductor L2. The fourth capacitor C4 is located in the main circuit of the second filter unit 200, while the third capacitor C3, the fifth capacitor C5, and the second inductor L2 are all grounded. Specifically, one end of the third capacitor C3 is connected to the main circuit of the adjacent first filter unit 100, and the other end is grounded; in other words, one end of the grounded branch containing the third capacitor C3 is connected to the connection node between the first filter unit 100 and the second filter unit 200, and the other end is grounded. One end of the fifth capacitor C5 is connected to the main circuit of the adjacent third filter unit 300, and the other end is grounded; one end of the second inductor L2 is connected to the main circuit of the adjacent third filter unit 300, and the other end is grounded.

[0058] In other representations, a ground branch is provided with a fifth capacitor C5, one end of which is connected to the connection node between the second filter unit 200 and the third filter unit 300, and the other end is grounded; a ground branch is provided with a second inductor L2, one end of which is connected to the connection node between the second filter unit 200 and the third filter unit 300, and the other end is grounded; or, the fifth capacitor C5 and the second inductor L2 are connected in parallel between the connection node between the second filter unit 200 and the third filter unit 300 and the ground terminal GND.

[0059] In the aforementioned embodiment, the main capacitor of the second filter unit 200 is the fourth capacitor C4, which is used to adjust impedance matching and reduce insertion loss. The arrangement of the third capacitor C3, the fifth capacitor C5, and the second inductor L2 in the three ground-connected branches of the second filter unit 200 can enhance the out-of-band rejection characteristics on both sides of the passband, and at the same time form a transmission pole at the center of the passband at 1.8 GHz. Figure 6 At the peak of the dashed line in S21, the signal transmission loss is relatively small at the transmission pole, which helps to reduce insertion loss within the passband. Similarly, using a symmetrical structure helps to increase the overall slope of the curve and the out-of-band suppression effect.

[0060] In a preferred embodiment, such as Figure 1As shown, the third filter unit 300 includes two sixth capacitors C6, a seventh capacitor C7, an eighth capacitor C8, and a third inductor L3. The two sixth capacitors C6 are connected in series in the main circuit of the third filter unit 300. The third filter unit 300 has a ground branch, which includes a capacitor connected in series in the branch, and a set of capacitors and inductors connected in parallel, specifically as follows: Figure 1 As shown, the ground branch of the third filter unit 300 includes a seventh capacitor C7, an eighth capacitor C8, and a third inductor L3. One end of the seventh capacitor C7 is connected to the connection node between the two sixth capacitors C6. The eighth capacitor C8 and the third inductor L3 are connected in parallel between the other end of the seventh capacitor C7 and the ground terminal. In other words, the ground branch of the third filter unit 300 includes a seventh capacitor C7 connected in series and a resonant unit, which is composed of the eighth capacitor C8 and the third inductor L3 connected in parallel.

[0061] In the aforementioned embodiments, the eighth capacitor C8 and the third inductor L3 connected in parallel in the ground branch of the third filter unit 300 give the circuit structure of the third filter unit 300 itself an asymmetrical characteristic. On the other hand, unlike the first filter unit 100 and the second filter unit 200, the aforementioned embodiments only include one third filter unit 300. Therefore, a single third filter unit 300 does not have the characteristic of mirror symmetry between two first filter units 100 or two second filter units 200. Combined with the asymmetry of the third filter unit 300 itself, the integrated passive filter circuit as a whole has a semi-symmetrical (or partially symmetrical) characteristic.

[0062] Based on the foregoing, the single third filter unit 300 in this embodiment, compared to the scheme of setting two mirrored third filter units 300, can avoid mutual interference between the two inductors and occupy more space.

[0063] In the foregoing embodiments, such as Figure 7 As shown, the circuit structure of the third filter unit 300 adds a new transmission pole in the passband, namely the peak of the dashed curve S21 in the figure, which is beneficial to increase the passband width and reduce transmission loss.

[0064] In a preferred embodiment, since the high-frequency zero on the right side of the passband is achieved in the first filtering unit through the parallel connection of the second capacitor C2 and the first inductor L1, and the high-frequency signal is transmitted to the ground plane through the first capacitor C1 in the ground branch, the capacitance value c1 of the first capacitor C1 is relatively minimal, and preferably does not exceed the capacitance value c2 of the second capacitor C2. Specifically, the capacitance value c1 of the first capacitor C1 and the capacitance value c2 of the second capacitor satisfy the following relationship:

[0065] 1:1≤c2:c1<2:1.

[0066] For the second filter unit 200, the fourth capacitor C4 needs to be adjusted for main circuit impedance matching to reduce insertion loss. Therefore, the capacitance value c4 of the fourth capacitor C4 is maximized according to impedance matching optimization. In a preferred embodiment, the capacitance value c2 of the second capacitor C2 and the capacitance value c4 of the fourth capacitor C4 satisfy the following relationship:

[0067] c4:c2>4:1.

[0068] In a preferred embodiment, the eighth capacitor C8 in the third filter unit 300 is used to adjust high-frequency out-of-band suppression, therefore its capacitance value is relatively small, typically in the pF range, generally close to the capacitance value c1 of the first capacitor C1, and the ratio between the two is generally 0.5 to 2 times, which can be close to or equal to 1:1. That is, the capacitance value c1 of the first capacitor C1 and the capacitance value c8 of the eighth capacitor C8 satisfy the following relationship:

[0069] 0.5≤c8:c1≤2.

[0070] More preferably, the capacitance value c1 of the first capacitor C1 is equal to or approximately equal to the capacitance value c8 of the eighth capacitor C8.

[0071] In a preferred embodiment, the inductor in the ground branch of the third filter unit 300, namely the third inductor L3, has a larger inductance value, approximately double that of other inductors in the circuit. Specifically, the inductance values ​​l2 of the second inductor L2 and l3 of the third inductor L3 satisfy the following relationship:

[0072] 1.5:1 ≤ l3:l2 < 4:1.

[0073] In a preferred embodiment, the inductance value l1 of the first inductor L1 and the inductance value l2 of the second inductor L2 are similar or equal, satisfying the following relationship:

[0074] 1:0.5≥l1:l2>1:2.

[0075] In the aforementioned embodiment, the third inductor L3 adds an additional transmission zero in the low-frequency region of the passband, which increases out-of-band rejection in the low-frequency band.

[0076] In a typical embodiment, the integrated passive filter circuit is a bandpass filter circuit with a center frequency of 1.8 GHz and a bandwidth of 400 MHz.

[0077] The following is a specific example to disclose the technical solution of this application.

[0078] Example

[0079] An integrated passive filter circuit is disclosed. This bandpass filter circuit is designed with a center frequency of 1.8 GHz and a passband of 400 MHz. It includes 14 capacitors and 5 inductors, such as... Figure 1 As shown, capacitors C1 to C6 and inductors L1 and L2 are all symmetrical structures.

[0080] like Figure 1 The integrated passive filter circuit, as defined by the dashed box, includes two first filter units 100, two second filter units 200, and a third filter unit 300. Each of the first filter units 100, second filter units 200, and third filter units 300 includes a main circuit and a grounding element connected to the main circuit. The main circuits of the two second filter units 200 are respectively connected to both ends of the main circuit of the third filter unit 300, and the two second filter units 200 are symmetrical with respect to the third filter unit 300. The main circuits of the two first filter units 100 are respectively connected to the main circuits of the two second filter units 200, and the two first filter units 100 are symmetrical with respect to the two second filter units 200 and the third filter unit 300. The end of the main circuit of the first filter unit 100 serves as the port P1 / P2 of the integrated passive filter circuit.

[0081] The first filter unit 100 includes: a first capacitor C1, one end of which is connected to a port and the other end is grounded; a first inductor L1 and a second capacitor C2 connected in parallel are disposed in the main circuit of the first filter unit 100.

[0082] The second filter unit 200 includes: a third capacitor C3, one end of which is connected to the main circuit of the adjacent first filter unit 100, and the other end is grounded; a fourth capacitor C4, which is disposed in the main circuit of the second filter unit 200; a fifth capacitor C5, one end of which is connected to the main circuit of the adjacent third filter unit 300, and the other end is grounded; and a second inductor L2, one end of which is connected to the main circuit of the adjacent third filter unit 300, and the other end is grounded.

[0083] The third filter unit 300 includes: two sixth capacitors C6, which are connected in series in the main circuit of the third filter unit 300; a seventh capacitor C7, an eighth capacitor C8 and a third inductor L3, wherein one end of the seventh capacitor C7 is connected to the connection node of the two sixth capacitors C6, and the eighth capacitor C8 and the third inductor L3 connected in parallel are connected between the other end of the seventh capacitor C7 and the ground terminal.

[0084] The capacitance values ​​c1 of the first capacitor C1 and c2 of the second capacitor C2 satisfy the following relationship: 1:1 ≤ c2:c1 < 2:1.

[0085] The capacitance value c2 of the second capacitor C2 and the capacitance value c4 of the fourth capacitor C4 satisfy the following relationship: c4:c2>4:1.

[0086] The capacitance value c1 of the first capacitor C1 and the capacitance value c8 of the eighth capacitor C8 satisfy the following relationship: 0.5≤c8:c1≤2.

[0087] The inductance value l2 of the second inductor L2 and the inductance value l3 of the third inductor L3 satisfy the following relationship: 1.5:1≤l3:l2<4:1.

[0088] The inductance values ​​l1 of the first inductor L1 and l2 of the second inductor L2 satisfy the following relationship: 1:0.5≥l1:l2>1:2.

[0089] The circuit characteristics of the aforementioned examples are as follows: Figure 2 As shown in the figure, the dashed line S21 illustrates the circuit's low insertion loss in the passband, exhibiting a -30dB characteristic at frequencies below 1.05GHz, with better out-of-band rejection at lower frequencies. In the high-frequency range, it demonstrates high overall out-of-band rejection, consistently remaining below -40dB, effectively suppressing high-frequency harmonics. The solid line S11 in the figure shows the circuit's return loss characteristics. Within a specific frequency band, a higher return loss value indicates a lower ratio of reflected signal power to incident signal power, better impedance matching performance, and significantly improved forward transmission power efficiency. The S11 curve shows that S11 can exceed -25dB in the passband, indicating good impedance matching.

[0090] The bandpass filter circuit provided in the example operates at a relatively high frequency, in the GHz range, and therefore can be applied in the radio frequency (RF) field. Furthermore, choosing a symmetrical circuit design can effectively reduce debugging issues after converting the circuit structure to a layout, reduce the number of simulation optimizations, and help shorten the product design cycle.

[0091] In summary, compared with existing technologies, the beneficial effects of the technical solution provided in this application are as follows:

[0092] 1. This bandpass filter circuit can effectively achieve bandpass filtering with a center frequency in the GHz range, featuring wide bandwidth, high out-of-band rejection, and high roll-off. This circuit can be widely used in RF transceiver links and communication platforms. Its high out-of-band rejection over a wide frequency range can effectively filter various noise and resonant waves. Fewer circuit components effectively reduce device size, making it widely applicable in various wireless communication scenarios, such as mobile phones, laptops, and other electronic devices.

[0093] 2. This bandpass filter circuit adopts a semi-symmetrical structure design. The symmetrical structure on both sides can effectively improve the consistency at both ends of the filter, enhance the out-of-band rejection and roll-off characteristics on both sides, and reduce the difference in reflection parameters at the device ports. The asymmetrical structure in the middle can further improve the out-of-band rejection on both sides, reduce the number of devices, and reduce device insertion loss, making it close to zero.

[0094] 3. By adopting a semi-symmetrical circuit topology design, the layout and optimization can be carried out in a symmetrical manner during subsequent product layout design, which reduces the difficulty of structural design and simulation.

[0095] The above are merely some specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An integrated passive filter circuit, characterized by, It includes two first filter units (100), two second filter units (200), and a third filter unit (300); each of the first filter unit (100), the second filter unit (200), and the third filter unit (300) includes a main circuit and a grounding element connected to the main circuit; The main paths of the two second filter units (200) are respectively connected to the two ends of the main path of the third filter unit (300), and the two second filter units (200) are symmetrical with respect to the third filter unit (300); The main paths of the two first filter units (100) are respectively connected to the main paths of the two second filter units (200), and the two first filter units (100) are symmetrical with respect to the two second filter units (200) and the third filter unit (300); the end of the main path of the first filter unit (100) serves as the port of the integrated passive filter circuit. The third filter unit (300) includes two parallel grounding elements of different types.

2. The integrated passive filter circuit of claim 1, wherein, The first filtering unit (100) includes: A first capacitor, one end of which is connected to the port, and the other end of which is grounded; The first inductor and the second capacitor, connected in parallel, are disposed in the main circuit of the first filter unit (100).

3. The integrated passive filter circuit of claim 2, wherein, The second filtering unit (200) includes: The third capacitor has one end connected to the main circuit of the adjacent first filter unit (100) and the other end grounded. A fourth capacitor is disposed in the main circuit of the second filter unit (200); A fifth capacitor, one end of which is connected to the main circuit of the adjacent third filter unit (300), and the other end is grounded; and, The second inductor has one end connected to the main circuit of the adjacent third filter unit (300), and the other end grounded.

4. The integrated passive filter circuit of claim 3, wherein, The third filtering unit (300) includes: Two sixth capacitors are connected in series in the main circuit of the third filter unit (300); A seventh capacitor, an eighth capacitor, and a third inductor are provided, wherein one end of the seventh capacitor is connected to the connection node of the two sixth capacitors, and the eighth capacitor and the third inductor, which are connected in parallel, are connected between the other end of the seventh capacitor and the ground terminal.

5. The integrated passive filter circuit of claim 2, wherein, The capacitance value c1 of the first capacitor and the capacitance value c2 of the second capacitor satisfy the following relationship: 1:1 ≤ c2:c1 < 2:

1.

6. The integrated passive filter circuit of claim 3 or 4, wherein, The capacitance value c2 of the second capacitor and the capacitance value c4 of the fourth capacitor satisfy the following relationship: c4:c2>4:

1.

7. The integrated passive filter circuit of claim 4, wherein, The capacitance value c1 of the first capacitor and the capacitance value c8 of the eighth capacitor satisfy the following relationship: 0.5≤c8:c1≤2.

8. The integrated passive filter circuit of claim 7, wherein, The capacitance value c1 of the first capacitor is equal to the capacitance value c8 of the eighth capacitor.

9. The integrated passive filter circuit of claim 4, wherein, The inductance value l2 of the second inductor and the inductance value l3 of the third inductor satisfy the following relationship: 1.5：1≤l3：l2＜4：1。 10. The integrated passive filter circuit of claim 3 or 4, wherein, The inductance value l1 of the first inductor and the inductance value l2 of the second inductor satisfy the following relationship: 1：0.5≥l1：l2＞1：2。

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