A Lumped-Distributed Hybrid Bandpass Filter

Abstract

The present invention discloses a lumped-distributed hybrid bandpass filter, comprising an upper layer, a middle layer, and a bottom layer; the upper and bottom layers are bonded to the middle layer by depositing copper ions, the upper layer comprising metal transmission lines and capacitors; the middle layer is a dielectric substrate; the bottom layer is a grounded metal plate; the upper metal transmission lines comprise a first transmission line, a second transmission line, a first inductor 81, a second inductor, a third inductor, a fourth inductor, a third transmission line, and a fourth transmission line, which are sequentially connected in the order of the first transmission line, the second transmission line, the first inductor, the second inductor, the third inductor, the fourth inductor, the third transmission line, and the fourth transmission line to form a ring. The bandpass filter of the present invention further reduces the size of a dual-mode filter, achieving miniaturization.

Description

Technical Field

[0001] The present invention relates to a lumped-distributed hybrid bandpass filter, belongs to the field of microwave technology, and can be used in 5G wireless communication systems. Background Art

[0002] With the advent of 5G, people are placing higher demands on components in communication systems. Bandpass filters, as an essential component of wireless communication systems, primarily select useful signals and suppress useless ones. Furthermore, with the advent of the 5G era, the communication spectrum is becoming increasingly crowded, creating an urgent need for highly selective bandpass filters in wireless communication systems. Furthermore, out-of-band interference in wireless communication systems is currently an important research area in modern microwave communication systems. Therefore, in addition to high selectivity, filters also require a wide stopband range. Since bandpass filters are widely used in wireless communication systems, they also need to be miniaturized. Summary of the Invention

[0003] The technical problem to be solved by the present invention is that the bandpass filter needs to have the characteristic of miniaturization.

[0004] To solve the above technical problems: the present invention provides a lumped-distributed hybrid bandpass filter, comprising an upper layer, a middle layer and a bottom layer; the upper layer and the bottom layer are bonded to the middle layer by depositing copper ions, the upper layer comprises a metal transmission line 12 and a capacitor; the middle layer is a dielectric substrate 10; and the bottom layer is a grounded metal plate 11;

[0005] The upper metal transmission line 12 includes a first transmission line 21, a second transmission line 31, a first inductor 81, a second inductor 82, a third inductor 83, a fourth inductor 84, a third transmission line 32, and a fourth transmission line 22, and is connected in the order of the first transmission line 21, the second transmission line 31, the first inductor 81, the second inductor 82, the third inductor 83, the fourth inductor 84, the third transmission line 32, and the fourth transmission line 22 to form a ring.

[0006] One end of the second capacitor 4 is connected to the connection between the first transmission line 21 and the fourth transmission line 22 through a short transmission line;

[0007] One end of the third capacitor 51 is connected to the connection point between the second transmission line 31 and the first inductor 81 through a short transmission line;

[0008] One end of the fourth capacitor 52 is connected to the connection point of the third transmission line 32 and the fourth inductor 84 through a short transmission line;

[0009] One end of the fifth capacitor 6 is connected to the second inductor 82 and the third inductor 83 through short transmission lines;

[0010] The sixth capacitor is connected to the first inductor 81 and the second inductor 82 respectively through short transmission lines;

[0011] The seventh capacitor is connected to the third inductor 83 and the fourth inductor 84 respectively through short transmission lines;

[0012] The second capacitor 4 , the third capacitor 51 , the fourth capacitor 52 , the fifth capacitor 6 , the sixth capacitor, and the seventh capacitor are respectively connected to metallized through-holes through a short transmission line. The metallized through-holes pass through the dielectric substrate 10 and are connected to the ground metal plate 11 .

[0013] In the aforementioned lumped-distributed hybrid bandpass filter, each capacitor is a chip capacitor, a parallel plate capacitor or an interdigital capacitor.

[0014] In the aforementioned lumped-distributed hybrid bandpass filter, the first capacitor 1 is connected to the middle point between the first transmission line 21 and the second transmission line 31 , and the first port is connected to the first capacitor 1 .

[0015] In the aforementioned lumped-distributed hybrid bandpass filter, the eighth capacitor 14 is connected to the connection point between the third transmission line 32 and the fourth transmission line 22 , and the second port is connected to the eighth capacitor 14 .

[0016] In the aforementioned lumped-distributed hybrid bandpass filter, the first transmission line 21 , the second transmission line 31 , the third transmission line 32 , and the fourth transmission line 22 are used to load respective capacitors, and their electrical lengths are 15°-20°.

[0017] In the aforementioned lumped-distributed hybrid bandpass filter, the first inductor 81 and the second inductor 82 , and the third inductor 83 and the fourth inductor 84 are coupled in pairs through spatial coupling.

[0018] In the aforementioned lumped-distributed hybrid bandpass filter, the dielectric substrate 10 is a single-layer substrate or a multi-layer substrate, wherein the multi-layer substrate can be laminated by a traditional PCB process.

[0019] The beneficial effects achieved by the present invention are as follows: the lumped-distributed hybrid bandpass filter of the present invention further reduces the size of the dual-mode filter by using lumped units to perform equivalent operations on longer transmission lines, and the side lengths of the final physical dimensions are all less than 0.1 λ. g , so it has the characteristics of miniaturization.

[0020] At the same time, the filter proposed by the present invention has a transmission zero point on each side of the passband. The two transmission zero points make the filter highly selective. There is also a transmission zero point near the 2nd harmonic of the passband, which suppresses the double harmonic of the filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1An axonometric diagram of a first embodiment of a lumped-distributed hybrid bandpass filter according to the present invention;

[0022] Figure 2 A top view of a first embodiment of a lumped-distributed hybrid bandpass filter according to the present invention;

[0023] Figure 3 1 is an equivalent circuit diagram of a lumped-distributed hybrid bandpass filter according to a first embodiment of the present invention;

[0024] Figure 4 This is an EM simulation S-parameter curve diagram of Example 1 of the present invention;

[0025] Figure 5 This is the circuit schematic diagram of the dual-mode filter;

[0026] Figure 6 The circuit simulation S parameter curve of the dual-mode filter;

[0027] Figure 7 Schematic diagram of lumped parameter elements replacing transmission lines.

[0028] In the figure: 1. First capacitor, 21. First transmission line, 22. Fourth transmission line, 31. Second transmission line, 32. Third transmission line, 4. Second capacitor, 51. Third capacitor, 52. Fourth capacitor, 6. Fifth capacitor, 71. Sixth capacitor, 72. Seventh capacitor, 8. Inductor, 9. Spatial coupling, 10. Dielectric substrate, 11. Grounded metal plate, 13. Metallized through hole, 14. Eighth capacitor. Implementation Method

[0029] The present invention will be described in further detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto. Example

[0030] like Figure 1 As shown, the embodiment of the present invention discloses a lumped-distributed hybrid bandpass filter, which includes an upper layer, a middle layer and a bottom layer; the upper layer and the bottom layer are bonded to the middle layer by depositing copper ions, the upper layer includes a metal transmission line 12 and a capacitor; the middle layer is a dielectric substrate 10; and the bottom layer is a grounded metal plate 11;

[0031] The upper metal transmission line 12 includes a first transmission line 21, a second transmission line 31, a first inductor 81, a second inductor 82, a third inductor 83, a fourth inductor 84, a third transmission line 32, and a fourth transmission line 22. The first transmission line 21, the second transmission line 31, the first inductor 81, the second inductor 82, the third inductor 83, the fourth inductor 84, the third transmission line 32, and the fourth transmission line 22 are connected in sequence to form a ring. The filter is bilaterally symmetrical about the center.

[0032] One end of the second capacitor 4 is connected to the connection between the first transmission line 21 and the fourth transmission line 22 through a short transmission line;

[0033] One end of the third capacitor 51 is connected to the connection point between the second transmission line 31 and the first inductor 81 through a short transmission line;

[0034] One end of the fourth capacitor 52 is connected to the connection point of the third transmission line 32 and the fourth inductor 84 through a short transmission line;

[0035] One end of the fifth capacitor 6 is connected to the second inductor 82 and the third inductor 83 through short transmission lines;

[0036] The sixth capacitor is connected to the first inductor 81 and the second inductor 82 respectively through short transmission lines;

[0037] The seventh capacitor is connected to the third inductor 83 and the fourth inductor 84 respectively through short transmission lines;

[0038] The second capacitor 4, the third capacitor 51, the fourth capacitor 52, the fifth capacitor 6, the sixth capacitor, and the seventh capacitor are respectively connected to the metallized through-holes through a short transmission line. The metallized through-holes pass through the dielectric substrate 10 and are connected to the grounding metal plate 11. The function of the metallized through-holes is to ground the upper circuit.

[0039] Each capacitor is a chip capacitor, a parallel plate capacitor or an interdigital capacitor.

[0040] The first capacitor 1 is connected to the middle point of the first transmission line 21 and the second transmission line 31, and the first port is connected to the first capacitor 1; the first capacitor can be used to adjust the external Q value of the filter, thereby adjusting the return loss within the band;

[0041] The eighth capacitor 14 is connected to a connection point between the third transmission line 32 and the fourth transmission line 22 , and the second port is connected to the eighth capacitor 14 .

[0042] The first transmission line 21, the second transmission line 31, the third transmission line 32, and the fourth transmission line 22 are used to load respective capacitors, and their electrical lengths are 15°-20°.

[0043] The first inductor 81 and the second inductor 82 , and the third inductor 83 and the fourth inductor 84 are coupled in pairs through spatial coupling.

[0044] The lumped-distributed hybrid bandpass filter design method of the present invention is as follows:

[0045] 1) First, create the following in the circuit simulation software ADS Figure 5 The circuit schematic diagram of the dual-mode filter is shown in Figure 5The electrical length of the first transmission line 21, the second transmission line 31, the third transmission line 32 and the fourth transmission line 22 is 18°, and the electrical length of the fifth transmission line 101 and the sixth transmission line 102 is 42°;

[0046] 2) Debug the circuit diagram and obtain the performance diagram, such as Figure 6 As shown;

[0047] 3) Perform lumped parameter equivalence on the fifth and sixth transmission lines. Usually, capacitors and inductors are considered as lumped parameter elements, and transmission lines are considered as distributed elements. Figure 5 In the embodiment, the electrical length of the fifth transmission line 101 and the sixth transmission line 102 is 42°. Figure 7 The equivalent model of the transmission line with an electrical length of 42° is equivalent through circuit simulation software. Figure 5 The circuit diagram in the equivalent Figure 3 The circuit diagram reduces the size of the circuit and further miniaturizes the filter structure. Figure 3 That is the circuit principle diagram of the lumped-distributed hybrid bandpass filter provided by the present invention, and all component values ​​of the circuit diagram are obtained after fine-tuning.

[0048] 4) Based on all component values ​​in the circuit diagram, high-frequency simulation software HFSS is used to build a model. The specific physical dimensions are calculated based on the electrical length and impedance value of the transmission line. The inductance value is extracted using high-frequency simulation software HFSS. The corresponding datasheet is imported into the model established by high-frequency simulation software HFSS. In the specific test, the dielectric substrate uses a ceramic substrate with a dielectric constant of 9.9 and a thickness of 0.254 mm. The capacitor specification is 01005 chip capacitor. High-frequency simulation software HFSS is used to model, simulate, and debug the circuit, and finally the specific physical dimensions and performance diagram of the filter are obtained. The physical structure of the filter is shown in the figure. Figure 1 and Figure 2 Figure 4 is a simulated S-parameter diagram of the proposed filter. The simulation results show that the center frequency of the filter is 3.5 GHz, the 20-dB return loss relative bandwidth (3.4 GHz-3.6 GHz) is 5.7%, the maximum insertion loss in the band is 1.5 dB, the stopband can be extended to 7 GHz, and the filter size is 2.6 mm × 2.66 mm, that is, 0.093λ g ×0.095 λ g ,λ g is the waveguide wavelength corresponding to the center frequency of the filter.

[0049] The simulation results show that the proposed filter has a transmission zero on each side of the passband, which gives the filter high selectivity. Furthermore, there is a transmission zero near the second harmonic of the passband, which suppresses the second harmonic of the filter.

[0050] The present invention uses lumped units to perform equivalent operations on longer transmission lines. Loading capacitance on the transmission line can reduce the length of the transmission line, and the lumped elements loaded with capacitance or inductance can destroy the periodicity of the transmission line, thereby further reducing the size of the dual-mode filter. The side length of the final physical size of the filter is less than 0.1 λ. g ,Therefore, the lumped-distributed hybrid type bandpass filter has the characteristics of miniaturization and wide stopband. Based on the above characteristics, the lumped-distributed hybrid type bandpass filter can meet the needs of wireless communication systems. Example

[0051] A lumped-distributed hybrid bandpass filter comprises an upper layer, a middle layer, and a bottom layer; the upper layer and the bottom layer are bonded to the middle layer by depositing copper ions, the upper layer comprises a metal transmission line 12 and a capacitor; the middle layer is a dielectric substrate 10; and the bottom layer is a grounded metal plate 11.

[0052] The upper metal transmission line 12 includes a first transmission line 21, a second transmission line 31, a first inductor 81, a second inductor 82, a third inductor 83, a fourth inductor 84, a third transmission line 32, and a fourth transmission line 22. The first transmission line 21, the second transmission line 31, the first inductor 81, the second inductor 82, the third inductor 83, the fourth inductor 84, the third transmission line 32, and the fourth transmission line 22 are connected in sequence to form a ring. The filter is bilaterally symmetrical about the center.

[0053] One end of the second capacitor 4 is connected to the connection between the first transmission line 21 and the fourth transmission line 22 through a short transmission line;

[0054] One end of the third capacitor 51 is connected to the connection point between the second transmission line 31 and the first inductor 81 through a short transmission line;

[0055] One end of the fourth capacitor 52 is connected to the connection point of the third transmission line 32 and the fourth inductor 84 through a short transmission line;

[0056] One end of the fifth capacitor 6 is connected to the second inductor 82 and the third inductor 83 through short transmission lines;

[0057] The sixth capacitor is connected to the first inductor 81 and the second inductor 82 respectively through short transmission lines;

[0058] The seventh capacitor is connected to the third inductor 83 and the fourth inductor 84 respectively through short transmission lines;

[0059] The second capacitor 4, the third capacitor 51, the fourth capacitor 52, the fifth capacitor 6, the sixth capacitor, and the seventh capacitor are respectively connected to the metallized through-holes through a short transmission line. The metallized through-holes pass through the dielectric substrate 10 and are connected to the grounding metal plate 11. The function of the metallized through-holes is to ground the upper circuit.

[0060] The dielectric substrate 10 is a single-layer substrate or a multi-layer substrate. The multi-layer substrate can be laminated by a traditional PCB process. The effect of the multi-layer substrate is miniaturization.

[0061] Other technical features are the same as those in Example 1.

[0062] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A lumped-distributed hybrid bandpass filter, characterized in that: It comprises an upper layer, a middle layer and a bottom layer; the upper layer and the bottom layer are bonded to the middle layer by depositing copper ions, the upper layer comprises a metal transmission line (12) and a capacitor; the middle layer is a dielectric substrate (10); and the bottom layer is a grounding metal plate (11); The upper metal transmission line (12) includes a first transmission line (21), a second transmission line (31), a first inductor (81), a second inductor (82), a third inductor (83), a fourth inductor (84), a third transmission line (32), and a fourth transmission line (22), and is connected in sequence in the order of the first transmission line (21), the second transmission line (31), the first inductor (81), the second inductor (82), the third inductor (83), the fourth inductor (84), the third transmission line (32), and the fourth transmission line (22) to form a ring; One end of the second capacitor (4) is connected to the connection point between the first transmission line (21) and the fourth transmission line (22) through a short transmission line; One end of the third capacitor (51) is connected to the connection point between the second transmission line (31) and the first inductor (81) through a short transmission line; One end of the fourth capacitor (52) is connected to the connection point of the third transmission line (32) and the fourth inductor (84) through a short transmission line; One end of the fifth capacitor (6) is connected to the second inductor (82) and the third inductor (83) via a short transmission line; The sixth capacitor is connected to the first inductor (81) and the second inductor (82) respectively via a short transmission line; The seventh capacitor is connected to the third inductor (83) and the fourth inductor (84) respectively via short transmission lines; The second capacitor (4), the third capacitor (51), the fourth capacitor (52), the fifth capacitor (6), the sixth capacitor, and the seventh capacitor are respectively connected to the metallized through-holes via a short transmission line, and the metallized through-holes pass through the dielectric substrate (10) and are connected to the ground metal plate (11).

2. The lumped-distributed hybrid bandpass filter according to claim 1, characterized in that: Each capacitor is a chip capacitor, a parallel plate capacitor or an interdigital capacitor.

3. The lumped-distributed hybrid bandpass filter according to claim 1, characterized in that: The first capacitor (1) is connected to a connection middle point between the first transmission line (21) and the second transmission line (31), and the first port is connected to the first capacitor (1).

4. The lumped-distributed hybrid bandpass filter according to claim 1, characterized in that: The eighth capacitor (14) is connected to the connection point between the third transmission line (32) and the fourth transmission line (22), and the second port is connected to the eighth capacitor (14).

5. The lumped-distributed hybrid bandpass filter according to claim 1, characterized in that: The first transmission line (21), the second transmission line (31), the third transmission line (32), and the fourth transmission line (22) are used for loading the respective capacitors, and their electrical lengths are 15°-20°.

6. The lumped-distributed hybrid bandpass filter according to claim 1, characterized in that: The first inductor (81) and the second inductor (82), and the third inductor (83) and the fourth inductor (84) are coupled in pairs through spatial coupling.

7. The lumped-distributed hybrid bandpass filter according to claim 1, characterized in that: The dielectric substrate (10) is a single-layer substrate or a multi-layer substrate, wherein the multi-layer substrate can be formed by lamination using a traditional PCB process.

Images