A Bandpass Filter with Multiple Transmission Zeros

Abstract

The invention provides a multi-transmission zero-point bandpass filter, belonging to the field of communication technology, comprising a plurality of π-type filter units with different inductance values ​​and capacitance values; a first π-type filter unit located on an input main path and connected to an input end, a last π-type filter unit located on an output main path and connected to an output end, and a π-type filter unit located in the middle coupled with the first π-type filter unit and the last π-type filter unit through a coupling capacitor; the multi-transmission zero-point bandpass filter achieves high selectivity and high attenuation by introducing three transmission zero points on both sides of a passband, and the invention solves the problem of poor selectivity and fewer transmission zero points of a bandpass filter composed of lumped parameter elements.

Description

Technical Field

[0001] The invention belongs to the field of communication technology, and in particular relates to a multi-transmission zero-point bandpass filter. Background Art

[0002] Bandpass filters with ultra-miniaturized volumes are more suitable for use in wireless terminal devices, as the volume of wireless devices is getting smaller and smaller. Therefore, bandpass filters based on low-temperature co-fired ceramics, complementary oxide semiconductors, and integrated passive technologies are becoming more and more popular. Among them, integrated passive technology has become popular due to its advantages such as low insertion loss, high Q value, and ultra-miniaturized size. In addition to size, high-performance bandpass filters with high selectivity and low loss are also urgently needed. The application of lumped elements enables on-chip bandpass filters to obtain controllable transmission zeros without cross-coupling and hybrid coupling, compared to bandpass filters designed using distributed parameters.

[0003] Although traditional IPD filters have miniaturized size, high-performance bandpass filters with high selectivity and low loss are also urgently needed. Although traditional IPD filters can obtain some controllable transmission zeros through lumped parameters, the stopband suppression level they achieve is relatively limited; in addition, the number of transmission zeros obtained is also limited. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides a multi-transmission zero bandpass filter, which solves the problem of poor selectivity and few transmission zeros of the bandpass filter composed of lumped parameter elements.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: a multi-transmission zero-point bandpass filter, the multi-transmission zero-point bandpass filter includes a plurality of π-type filter units with different inductance values ​​and capacitance values;

[0006] The first π-type filter unit is located on the input main line and connected to the input end, the last π-type filter unit is located on the output main line and connected to the output end, and the middle π-type filter unit is coupled with the first π-type filter unit and the last π-type filter unit through coupling capacitors; the π-type filter unit introduces a transmission pole, and the multi-transmission zero-point bandpass filter achieves high selectivity and high attenuation by introducing transmission zeros on both sides of the passband.

[0007] Furthermore, the π-type filter unit is provided with an inductor L on the input main circuit and the output main circuit. S1 、Inductance L S2 And the inductor L S3 ; In the inductor L S1 A first series resonant circuit L connected to ground is provided on one side of 11 C11 , in the inductor L S1 The other side is provided with a second series resonant circuit L connected to the ground 12 C 12 , in the inductor L S2 A third series resonant circuit L connected to ground is provided on one side of 21 C 21 , in the inductor L S2 The other side is provided with a fourth series resonant circuit L connected to the ground 22 C 22 , in the inductor L S3 A fifth series resonant circuit L connected to ground is provided on one side of 31 C 31 , in the inductor L S3 The other side is provided with a sixth series resonant circuit L connected to the ground 32 C 32 ; Inductance L 12 With inductance L 21 Use capacitor C between p1 For coupling, the inductor L 22 With inductance L 31 Capacitor C is used between p2 To couple.

[0008] Furthermore, the inductor L 11 One end and the inductor L s1 One end of each is connected to the input terminal, and the inductor L 11 The other end of the capacitor C 11 One end of the capacitor C 11 The other end of the inductor L is grounded; s1 The other end of the inductor L 12 One end and capacitor C p1 One end of the inductor is connected to 12 The other end of the capacitor C 12 One end of the capacitor C 12 The other end of the capacitor C p1 The other end of the inductor L 21 One end and the inductor L s2 One end of the inductor is connected to 21 The other end of the capacitor C 21 One end of the capacitor C 21 The other end of the inductor L is grounded; s2 The other end of the inductor L 22 One end and capacitor C p2 One end of the inductor is connected to 22 The other end of the capacitor C 22 One end of the capacitor C 22 The other end of the capacitor Cp2 The other end of the inductor L 31 One end and the inductor L s3 One end of the inductor is connected to 31 The other end of the capacitor C 31 One end of the capacitor C 31 The other end of the inductor L is grounded; s3 The other end of the inductor L 32 One end of the inductor is connected to the output end, and the inductor L 32 The other end of the capacitor C 32 One end of the capacitor C 32 The other end is grounded.

[0009] Furthermore, the first π-type filter unit, the last π-type filter unit and the π-type filter unit in the middle all introduce a transmission pole, and simultaneously introduce a transmission zero on both sides of the passband;

[0010] Among them, the three transmission poles include the inductor L S1 、Inductance L S2 And the inductor L S3 ; The three transmission zeros on one side of the passband include the second series resonant circuit L 12 C 12 , the fourth series resonant circuit L 22 C 22 And the fifth series resonant circuit L 31 C 31 The three transmission zeros on the other side of the passband include the first series resonant circuit L 11 C 11 , the third series resonant circuit L 21 C 21 and the sixth series resonant circuit L 32 C 32 .

[0011] Further, the multi-transmission zero-point bandpass filter includes a metal layer M1, a metal layer M2 and a metal layer M3;

[0012] An insulating layer MIM Cap is disposed between the metal layer M1 and the metal layer M2 ; the metal layer M1 , the metal layer M2 and the insulating layer MIM Cap constitute a parallel plate capacitor.

[0013] Furthermore, the inductor L S1 、Inductance L S2 、Inductance L S3 、Inductance L 11 、Inductance L 12 、Inductance L 21 、Inductance L 22 、Inductance L 31 And the inductor L32 Both include a metal layer M2 and a metal layer M3;

[0014] The inductor with the smallest inductance value obtains the Q value through the metal layer M3, and the inductor with the largest inductance value obtains the Q value through the stacking of the metal layer M2 and the metal layer M3.

[0015] Beneficial effects of the present invention:

[0016] The multi-transmission zero bandpass filter provided by the present invention proposes a π-type filter unit, which can introduce two transmission zeros while introducing a transmission pole. More importantly, the two transmission zeros can be flexibly controlled. At the same time, a third-order bandpass filter based on the π-type filter unit is proposed, and the multi-transmission zero bandpass filter achieves high selectivity and high attenuation on both sides of the passband. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the structure of the π-type filtering unit in the present invention.

[0018] Figure 2 This is a circuit schematic diagram of the π-type filter unit in the present invention.

[0019] Figure 3 It is a circuit schematic diagram of the multi-transmission zero-point bandpass filter in the present invention.

[0020] Figure 4 It is a schematic diagram of the structure of the multi-transmission zero-point bandpass filter in the present invention. DETAILED DESCRIPTION

[0021] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0022] Example

[0023] like Figure 3 and Figure 4As shown, the present invention provides a multi-transmission zero-point bandpass filter, which includes a plurality of π-type filter units with different inductance values ​​and capacitance values; a first π-type filter unit located on the input main path and connected to the input end, a last π-type filter unit located on the output main path and connected to the output end, and a π-type filter unit located in the middle coupled with the first π-type filter unit and the last π-type filter unit through a coupling capacitor; the π-type filter unit introduces a transmission pole, and the multi-transmission zero-point bandpass filter achieves high selectivity and high attenuation by introducing transmission zeros on both sides of the passband.

[0024] In this embodiment, the π-type filter unit is provided with an inductor L on the input main circuit and the output main circuit. S1 、Inductance L S2 And the inductor L S3 ; In the inductor L S1 A first series resonant circuit L connected to ground is provided on one side of 11 C 11 , in the inductor L S1 The other side is provided with a second series resonant circuit L connected to the ground 12 C 12 , in the inductor L S2 A third series resonant circuit L connected to ground is provided on one side of 21 C 21 , in the inductor L S2 The other side is provided with a fourth series resonant circuit L connected to the ground 22 C 22 , in the inductor L S3 A fifth series resonant circuit L connected to ground is provided on one side of 31 C 31 , in the inductor L S3 The other side is provided with a sixth series resonant circuit L connected to the ground 32 C 32 ; Inductance L 12 With inductance L 21 Use capacitor C between p1 For coupling, the inductor L 22 With inductance L 31 Capacitor C is used between p2 To couple.

[0025] In this embodiment, the inductor L 11 One end and the inductor L s1 One end of each is connected to the input terminal, and the inductor L 11 The other end of the capacitor C 11 One end of the capacitor C 11 The other end of the inductor L is grounded; s1 The other end of the inductor L 12 One end and capacitor Cp1 One end of the inductor is connected to 12 The other end of the capacitor C 12 One end of the capacitor C 12 The other end of the capacitor C p1 The other end of the inductor L 21 One end and the inductor L s2 One end of the inductor is connected to 21 The other end of the capacitor C 21 One end of the capacitor C 21 The other end of the inductor L is grounded; s2 The other end of the inductor L 22 One end and capacitor C p2 One end of the inductor is connected to 22 The other end of the capacitor C 22 One end of the capacitor C 22 The other end of the capacitor C p2 The other end of the inductor L 31 One end and the inductor L s3 One end of the inductor is connected to 31 The other end of the capacitor C 31 One end of the capacitor C 31 The other end of the inductor L is grounded; s3 The other end of the inductor L 32 One end of the inductor is connected to the output end, and the inductor L 32 The other end of the capacitor C 32 One end of the capacitor C 32 The other end is grounded.

[0026] In this embodiment, the first π-type filter unit, the last π-type filter unit and the middle π-type filter unit all introduce a transmission pole, and simultaneously introduce transmission zeros on both sides of the passband;

[0027] Among them, the three transmission poles include the inductor L S1 、Inductance L S2 And the inductor L S3 ; The three transmission zeros on one side of the passband include the second series resonant circuit L 12 C 12 , the fourth series resonant circuit L 22 C 22 And the fifth series resonant circuit L 31 C 31 The three transmission zeros on the other side of the passband include the first series resonant circuit L 11 C 11 , the third series resonant circuit L 21 C 21 and the sixth series resonant circuit L32 C 32 .

[0028] In this embodiment, a total of three π-type filter units are cascaded, so a total of three transmission poles and six transmission zeros are introduced. The three transmission poles are connected by the inductor L S1 、Inductance L S2 And the inductor L S3 The three transmission zeros on the left side of the passband are formed by the second series resonant circuit L 12 C 12 , the fourth series resonant circuit L 22 C 22 And the fifth series resonant circuit L 31 C 31 The three transmission zeros on the right side of the passband are formed by the first series resonant circuit L 11 C 11 , the third series resonant circuit L 21 C 21 and the sixth series resonant circuit L 32 C 32 Introduction.

[0029] In this embodiment, the multi-transmission zero-point bandpass filter includes metal layers M1, M2 and M3; an insulating layer MIM Cap is provided between the metal layers M1 and M2; the metal layers M1, M2 and the insulating layer MIM Cap constitute a parallel plate capacitor.

[0030] In this embodiment, the inductor L S1 、Inductance L S2 、Inductance L S3 、Inductance L 11 、Inductance L 12 、Inductance L 21 、Inductance L 22 、Inductance L 31 And the inductor L 32 Both include a metal layer M2 and a metal layer M3; wherein the inductor with the smallest inductance value obtains the Q value through the metal layer M3, and the inductor with the largest inductance value obtains the Q value through the stacking of the metal layer M2 and the metal layer M3.

[0031] In this embodiment, Figure 1 and Figure 2 As shown, the proposed π-type filter unit has an inductor L2 on the input and output main circuits, and has a grounded LC series resonant circuit (C1L1 and C2L3) on both sides of the main circuit inductor. Figure 2 In the equation, C01, C0 and C02 represent the parasitic capacitances of the three inductors respectively, and k represents the mutual inductance between the two inductors. Finally, the equivalent circuit of the filter unit can be simplified to a π-type filter unit. Figure 3As shown, in order to achieve a higher selectivity and suppression level, three π-type filter units with different inductance values ​​and capacitance values ​​are used, namely, the π-type filter unit (1), the π-type filter unit (2) and the π-type filter unit (3), wherein the π-type filter unit (1) is the first π-type filter unit, the π-type filter unit (2) is the π-type filter unit located in the middle, and the π-type filter unit (3) is the last π-type filter unit. Coupling capacitors are used to couple them, that is, coupling capacitors C are used between the π-type filter units (1) and (2). P1 , a coupling capacitor C is used between the π-type filter unit (2) and the π-type filter unit (3). P2 .exist Figure 1 In the process used in the present invention, three layers of metal are used, namely metal layer M1, metal layer M2 and metal layer M3 (M1, M2 and M3 all represent metal layers), where metal layer M1 is the first layer of metal. The capacitor in this process is a parallel plate capacitor composed of two layers of metal, metal layer M1 and metal layer M2, and MIM Cap is an insulating layer between these two layers of metal (metal layer M1 and metal layer M2). Metal layer M1, metal layer M2 and insulating layer MIM Cap together constitute a parallel plate capacitor.

[0032] In this embodiment, the proposed π-type filter unit can introduce two transmission zeros on both sides of a transmission pole while introducing a transmission pole, so as to improve the selectivity and suppression level of the stop band.

[0033] In this embodiment, the inductor is composed of a metal layer M2 and a metal layer M3. The inductor with a smaller inductance value uses the metal layer M3 to obtain a higher Q value; and the inductor with a larger inductance value is composed of the metal layers M2 and M3.

[0034] In this embodiment, Figure 4 As shown, there are three inductors (L s1 , L s2 and L s3 ), in the inductor L s1 One side has a series resonant circuit to ground (L 11 C 11 ), while the other side has a series resonant circuit to ground (L 12 C 12 ); in the inductor L s2 One side has a series resonant circuit to ground (L 21 C 21 ), while the other side has a series resonant circuit to ground (L 22 C 22 ); in the inductor L s3 One side has a series resonant circuit to ground (L 31 C31 ), while the other side has a series resonant circuit to ground (L 32 C 32 ). And the inductance L 12 With inductance L 12 Capacitor C is used between p1 For coupling, the inductor L 22 With inductance L 31 Capacitor C is used between p2 Finally, the bandpass filter achieves high selectivity and high attenuation by introducing three transmission zeros on both sides of the passband.

Claims

1. A multi-transmission zero bandpass filter, characterized in that: The multi-transmission zero-point bandpass filter includes a plurality of π-type filter units with different inductance values ​​and capacitance values; A first π-type filter unit is located on the input main path and connected to the input end, a last π-type filter unit is located on the output main path and connected to the output end, and a π-type filter unit located in the middle is coupled with the first π-type filter unit and the last π-type filter unit through a coupling capacitor; the π-type filter unit introduces a transmission pole, and the multi-transmission zero-point bandpass filter achieves high selectivity and high attenuation by introducing transmission zeros on both sides of the passband; The π-type filter unit is provided with an inductor L on the input main circuit and the output main circuit. S1 、Inductance L S2 And the inductor L S3 ; In the inductor L S1 A first series resonant circuit L connected to ground is provided on one side of 11 C 11 , in the inductor L S1 The other side is provided with a second series resonant circuit L connected to the ground 12 C 12 , in the inductor L S2 A third series resonant circuit L connected to ground is provided on one side of 21 C 21 , in the inductor L S2 The other side is provided with a fourth series resonant circuit L connected to the ground 22 C 22 , in the inductor L S3 A fifth series resonant circuit L connected to ground is provided on one side of 31 C 31 , in the inductor L S3 The other side is provided with a sixth series resonant circuit L connected to the ground 32 C 32 ; Inductance L 12 With inductance L 21 Use capacitor C between p1 For coupling, the inductor L 22 With inductance L 31 Capacitor C is used between p2 To couple; The multi-transmission zero-point bandpass filter comprises a metal layer M1, a metal layer M2 and a metal layer M3; An insulating layer MIM Cap is disposed between the metal layer M1 and the metal layer M2; the metal layer M1, the metal layer M2 and the insulating layer MIM Cap constitute a parallel plate capacitor; Inductance L S1 、Inductance L S2 、Inductance L S3 、Inductance L 11 、Inductance L 12 、Inductance L 21 、Inductance L 22 、Inductance L 31 And the inductor L 32 Both include a metal layer M2 and a metal layer M3; The inductor with the smallest inductance value obtains the Q value through the metal layer M3, and the inductor with the largest inductance value obtains the Q value through the stacking of the metal layer M2 and the metal layer M3.

2. The multi-transmission zero bandpass filter according to claim 1, characterized in that: Inductance L 11 One end and the inductor L s1 One end of each is connected to the input terminal, and the inductor L 11 The other end of the capacitor C 11 One end of the capacitor C 11 The other end of the inductor L is grounded; s1 The other end of the inductor L 12 One end and capacitor C p1 One end of the inductor is connected to 12 The other end of the capacitor C 12 One end of the capacitor C 12 The other end of the capacitor C p1 The other end of the inductor L 21 One end and the inductor L s2 One end of the inductor is connected to 21 The other end of the capacitor C 21 One end of the capacitor C 21 The other end of the inductor L is grounded; s2 The other end of the inductor L 22 One end and capacitor C p2 One end of the inductor is connected to 22 The other end of the capacitor C 22 One end of the capacitor C 22 The other end of the capacitor C p2 The other end of the inductor L 31 One end and the inductor L s3 One end of the inductor is connected to 31 The other end of the capacitor C 31 One end of the capacitor C 31 The other end of the inductor L is grounded; s3 The other end of the inductor L 32 One end of the inductor is connected to the output end, and the inductor L 32 The other end of the capacitor C 32 One end of the capacitor C 32 The other end is grounded.

3. The multi-transmission zero bandpass filter according to claim 2, characterized in that: The first π-type filter unit, the last π-type filter unit and the π-type filter unit in the middle all introduce a transmission pole, and simultaneously introduce transmission zeros on both sides of the passband; Among them, the three transmission poles include the inductor L S1 、Inductance L S2 And the inductor L S3 ; The three transmission zeros on one side of the passband include the second series resonant circuit L 12 C 12 , the fourth series resonant circuit L 22 C 22 And the fifth series resonant circuit L 31 C 31 The three transmission zeros on the other side of the passband include the first series resonant circuit L 11 C 11 , the third series resonant circuit L 21 C 21 and the sixth series resonant circuit L 32 C 32 .

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