CN110011009B - a bandpass filter - Google Patents

Abstract

The invention discloses a band-pass filter, which comprises a first layer of dielectric substrate, a second layer of dielectric substrate, a third layer of dielectric substrate, a fourth layer of dielectric substrate, a fifth layer of dielectric substrate, a first resonator, a second resonator, an input feeder and an output feeder, wherein the first layer of dielectric substrate, the second layer of dielectric substrate, the third layer of dielectric substrate, the fourth layer of dielectric substrate and the fifth layer of dielectric substrate are sequentially stacked; and the input feeder line and the output feeder line are fixedly arranged on the surface of the fifth layer dielectric substrate facing the fourth layer dielectric substrate. The invention is based on the multilayer dielectric plate stacking technology, the first resonator and the second resonator are respectively positioned on different layers, the resonant frequency can be changed by changing the length of the first resonator or the second resonator, and the first resonator and the second resonator are coupled through the slot. And two coupling paths are introduced, so that two transmission zeros can be generated, and the selectivity of the band-pass filter is greatly improved.

Description

a bandpass filter

technical field

The invention belongs to the technical field of microwave communication, and in particular relates to a bandpass filter.

Background technique

With the rapid development of wireless communication systems, communication standards such as GSM, CDMA, WCDMA, WIMAX, and WLAN have been widely used. As an essential and important component of the RF front-end, the filter is mainly used to separate frequencies, that is, to pass signals of a certain frequency and block signals of other frequencies. The ideal filter should satisfy the passband without attenuation and be at the cutoff frequency. Infinitely large internal attenuation requirements.

In traditional filter design, increasing the filter order is often used to achieve high selectivity and high isolation between passbands, but this easily leads to problems such as complex filter circuit structure, too large filter size, and increased manufacturing cost.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a band-pass filter, which aims to solve the problems of too large filter size and low selectivity.

In order to solve the above technical problems, the present invention is implemented in this way, a bandpass filter includes a first layer of dielectric substrate, a second layer of dielectric substrate, a third layer of dielectric substrate, a fourth layer of dielectric substrate, and a fifth layer of dielectric substrate. , a first resonator, a second resonator, an input feeder and an output feeder, the first layer of dielectric substrate, the second layer of dielectric substrate, the third layer of dielectric substrate, the fourth layer of dielectric substrate and the fifth layer of dielectric substrate are stacked in sequence ; Both the input feeder and the output feeder are fixedly arranged on the surface of the fifth-layer dielectric substrate facing the fourth-layer dielectric substrate;

The first resonator is fixedly arranged on the surface of the fourth-layer dielectric substrate facing the third-layer dielectric substrate, and a first feeding point extends from the first resonator;

The second resonator is fixedly arranged on the surface of the second-layer dielectric substrate facing the first-layer dielectric substrate, and a second resonator coupled to the first feeding point extends from the second resonator feed point;

The fourth-layer dielectric substrate is provided with a first metallized via electrically connected to the first feed point, a second metallized via opposite to the second feed point, and the third A third metallized via hole opposite to the second feeding point is opened on the layered dielectric substrate, and a fourth metallized via electrically connected to the second feeding point is opened on the second layered dielectric substrate hole;

The first feed point is electrically connected to the input feed line by connecting the first metallized via, and the second feed point is sequentially connected to the fourth metallized via and the third metallized via. A hole and a second metallized via to be electrically connected to the output feeder; or the first feed point is electrically connected to the output feeder by connecting the first metallized via, the second feed point is electrically connected to the input feeder by sequentially connecting the fourth metallized via, the third metallized via and the second metallized via;

The input feeder is coupled with the output feeder to form a first transmission path to generate a first transmission zero; the input feeder passes through the first resonator and the second resonator or the input feeder passes through the first resonator. The second resonator and the first resonator are coupled with the output feeder to form a second transmission path to generate a second transmission zero.

Further, the sidewalls of the first-layer dielectric substrate, the second-layer dielectric substrate, the third-layer dielectric substrate and the fourth-layer dielectric substrate are all plated with metal. The sidewalls are metallized to allow the bandpass filter to form a closed structure so that electromagnetic energy does not leak out.

Further, the first-layer dielectric substrate, the second-layer dielectric substrate, the third-layer dielectric substrate, and the fourth-layer dielectric substrate are identical in shape and size, and the four are stacked concentrically.

Further, the area of the fifth layer of dielectric substrate is larger than that of the fourth layer of dielectric substrate, the fourth layer of dielectric substrate is arranged at the center of the fifth layer of dielectric substrate, the input feeder and the output feeder They are respectively located on both sides of the fourth layer of dielectric substrate. The feed of the band-pass filter adopts a coplanar waveguide mode and is located on both sides of the same layer of dielectric plate, which facilitates the integration of the band-pass filter with other components.

Further, both the input feeder and the output feeder are microstrip lines with a characteristic impedance of 50 ohms.

Further, both the first resonator and the second resonator are helical structures with gaps.

Further, the helical structure is formed in a rectangular wrapping manner.

Further, the surrounding directions of the first resonator and the second resonator are opposite.

Further, on the surface of the fifth layer of dielectric substrate facing the fourth layer of dielectric substrate, metal is plated on the outside corresponding to the input feeder and the output feeder to form a first metal layer, the input feeder and the There is a gap between the output feed line and the first metal layer.

Further, two sides of the surface of the third layer of dielectric substrate facing the second layer of dielectric substrate are plated with metal to form a second metal layer, and the gap between the second metal layer is for transmission signals to pass through to allow all the The first feed point is coupled with the second feed point.

Compared with the prior art, the present invention has the beneficial effects that: the present invention is based on the multi-layer dielectric plate stacking technology, the first resonator and the second resonator are respectively located on different layers, and by changing the length of the first resonator or the second resonator The resonant frequency can be changed, and the first resonator and the second resonator are coupled through a slit, and this structure has the advantages of small size and simplicity. In addition, two coupling paths are introduced, which can generate two transmission zeros, which greatly improves the selectivity of the band-pass filter.

Description of drawings

1 is a schematic perspective view of an overall structure of a filter according to an embodiment of the present invention;

2 is a schematic top view of the overall structure of a filter according to an embodiment of the present invention;

3 is a schematic left view of the overall structure of a filter according to an embodiment of the present invention;

4 is a schematic front view of a fifth-layer dielectric substrate according to an embodiment of the present invention;

5 is a schematic rear view of a fifth-layer dielectric substrate according to an embodiment of the present invention;

6 is a schematic front view of a fourth-layer dielectric substrate according to an embodiment of the present invention;

7 is a schematic rear view of a fourth-layer dielectric substrate according to an embodiment of the present invention;

8 is a schematic front view of a third-layer dielectric substrate according to an embodiment of the present invention;

9 is a schematic rear view of a third-layer dielectric substrate according to an embodiment of the present invention;

10 is a schematic front view of a second-layer dielectric substrate according to an embodiment of the present invention;

FIG. 11 is a schematic rear view of a second-layer dielectric substrate according to an embodiment of the present invention;

FIG. 12 is a schematic front view of a first-layer dielectric substrate according to an embodiment of the present invention;

FIG. 13 is a frequency response curve diagram of an embodiment of the present invention.

In the drawings, each reference sign denotes:

1, the first layer of dielectric substrate; 2, the second layer of dielectric substrate; 3, the third layer of dielectric substrate; 4, the fourth layer of dielectric substrate; 5, the fifth layer of dielectric substrate; 6, the first resonator; 7, the first 2. Resonator; 8. Input feeder; 9. Output feeder; 21. Fourth metallized via; 31, third metallized via; 32, intermediate gap; 41, first metallized via; 42, second Metallized vias; 61, the first feeding point; 71, the second feeding point.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

It is to be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top" , "bottom", "inside", "outside", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, only for the convenience of describing the application and simplifying the description, rather than indicating or implying the indicated A device or element must have a particular orientation, be constructed and operate in a particular orientation, and therefore should not be construed as a limitation of the present application.

In addition, the terms "first" and "second" are only used for descriptive purposes, and should not be construed as indicating or implying relative importance or implying the number of indicated technical features. Thus, a feature defined as "first", "second" may expressly or implicitly include one or more of that feature. In the description of the present application, "plurality" means two or more, unless otherwise expressly and specifically defined.

As shown in FIG. 1-FIG. 12, a bandpass filter provided in this embodiment includes a first layer of dielectric substrate 1, a second layer of dielectric substrate 2, a third layer of dielectric substrate 3, a fourth layer of dielectric substrate 4, The fifth layer of dielectric substrate 5, the first resonator 6, the second resonator 7, the input feeder 8 and the output feeder 9, the first layer of dielectric substrate 1, the second layer of dielectric substrate 2, the third layer of dielectric substrate 3, The fourth layer of dielectric substrate 4 and the fifth layer of dielectric substrate 5 are stacked in sequence; the input feeder 8 and the output feeder 9 are fixedly arranged (fixed by embedding, but not limited to embedding, and other fixing methods are also possible, It will not be described in detail here) on the surface of the fifth-layer dielectric substrate 5 facing the fourth-layer dielectric substrate 4; the band-pass filter of this embodiment has a structure compared with a filter that achieves the same function. The advantage of smaller size effectively solves the problem of miniaturization of the integrated filter size.

As shown in FIG. 6 , the first resonator 6 is fixedly arranged on the surface of the fourth-layer dielectric substrate 4 facing the third-layer dielectric substrate 3 , and a first feeder extends from the first resonator 6 . electric point 61;

As shown in FIG. 10 , the second resonator 7 is fixedly disposed on the surface of the second layer of dielectric substrate 2 facing the first layer of dielectric substrate 1 , and the second resonator 7 extends out from the a second feeding point 71 coupled to the first feeding point;

As shown in FIG. 6 to FIG. 11 , the fourth-layer dielectric substrate 4 is provided with a first metallized via 41 electrically connected to the first feed point 61 , and a position of the second feed point 71 . Opposite the second metallized via hole 42 , the third layer of dielectric substrate 3 is provided with a third metallized via hole 31 opposite to the second feed point 71 , and the second layer of dielectric substrate 2 A fourth metallized via hole 21 electrically connected to the second feeding point 71 is opened;

In this embodiment, the first feed point 61 is electrically connected to the input feed line 8 by connecting the first metallized via 41 , and the second feed point 71 is connected to the fourth metal in sequence The vias 21 , the third vias 31 and the second vias 42 are electrically connected to the output feed line 9 . The input feeder 8 is coupled with the output feeder 9 to form a first transmission path to generate a first transmission zero, and the input feeder 8 is connected to the The output feeder 9 is coupled to form a second transmission path to create a second transmission zero. In this embodiment, two transmission zeros are generated by introducing multiple coupling paths, which effectively solves the problem of low frequency selectivity of the filter. In other embodiments, the first feed point 61 may also be electrically connected to the output feed line 9 by connecting the first metallized vias 41 , and the second feed point 71 may be connected to the output feed line 9 sequentially by connecting the The fourth metallized via hole 21 , the third metallized via hole 31 and the second metallized via hole 42 are electrically connected to the input feed line 8 . The input feeder 8 is coupled with the output feeder 9 to form a first transmission path to generate a first transmission zero, the input feeder 8 is connected with the second resonator 7 and the first resonator 6 through the second resonator 7 and the first resonator 6 The output feeder 9 is coupled to form a second transmission path to create a second transmission zero.

In this embodiment, the external quality factor of the filter is changed by changing the positions of the first feeding point 61 and the second feeding point 71, and the external quality factor is determined according to the fractional bandwidth of the filter, so that by changing the first feeding point 61 and the relative position of the second feeding point 71 to achieve the best effect.

In this embodiment, the sidewalls of the first-layer dielectric substrate 1 , the second-layer dielectric substrate 2 , the third-layer dielectric substrate 3 and the fourth-layer dielectric substrate 4 are all plated with metal. The sidewalls are metallized to allow the bandpass filter to form a closed structure so that electromagnetic energy does not leak out.

As shown in FIG. 1 to FIG. 3 , the first-layer dielectric substrate 1 , the second-layer dielectric substrate 2 , the third-layer dielectric substrate 3 and the fourth-layer dielectric substrate 4 are identical in shape and size, and these four are stacked concentrically. . Preferably, the area of the fifth-layer dielectric substrate 5 is larger than that of the fourth-layer dielectric substrate 4 , the fourth-layer dielectric substrate 4 is disposed at the center of the fifth-layer dielectric substrate 5 , and the input feeder 8 and the The output feed lines 9 are respectively located on both sides of the fourth-layer dielectric substrate 4 . In other embodiments, the first-layer dielectric substrate 1 , the second-layer dielectric substrate 2 , the third-layer dielectric substrate 3 , and the fourth-layer dielectric substrate 4 may not be particularly limited in shape and size. In this embodiment, the feeding of the bandpass filter is implemented in a coplanar waveguide manner, and the input feeder 8 and the output feeder 9 are located on both sides of the same layer of dielectric plate, which facilitates the integration of the bandpass filter with other components.

In this embodiment, the input feeder 8 and the output feeder 9 are both microstrip lines with a characteristic impedance of 50 ohms.

As shown in FIG. 6 and FIG. 10 , both the first resonator 6 and the second resonator 7 are helical structures with gaps. Preferably, the helical structures are all formed in a rectangular wrapping manner. More preferably, the surrounding directions of the first resonator 6 and the second resonator 7 are opposite.

In this embodiment, the center frequency of the bandpass filter is mainly determined by the lengths of the metal wires of the first resonator 6 and the second resonator 7, and the center frequency of the filter can be easily adjusted by changing the length of the spiral metal wires. By adjusting the distance between the first resonator 6 and the second resonator 7 and the position of the input and output ports, the coupling coefficient and external quality factor of the filter are adjusted respectively.

As shown in FIG. 4 , the fifth-layer dielectric substrate 5 faces the surface of the fourth-layer dielectric substrate 4 , and metal is plated on the outside corresponding to the input feeder 8 and the output feeder 9 to form a first metal layer, There are gaps between the input feed line 8 and the output feed line 9 and the first metal layer.

As shown in FIG. 8 , two sides of the surface of the third-layer dielectric substrate 3 toward the second-layer dielectric substrate 2 are plated with metal to form a second metal layer, and the gap 32 in the middle of the second metal layer is for transmission Signals pass through to couple the first feed point 61 with the second feed point 71 . In this embodiment, the coupling of signals can be controlled by changing the size of the intermediate gap 32 .

As shown in Figures 1 to 3, in order to process the bandpass filter, first, the circuit structure of each layer is printed, then each layer is stacked, and the first layer of dielectric substrate 1, the second layer of dielectric The sidewalls of the substrate 2 , the third-layer dielectric substrate 3 and the fourth-layer dielectric substrate 4 are plated with metal, and the first resonator 6 , the second resonator 7 and the input feeder 8 and the output feeder 9 are connected by through holes. In this embodiment, the characteristic impedance of the coplanar waveguide transmission line of the fifth-layer dielectric substrate 5 is 50 ohms, and there are two feeding ports, which are respectively connected to two SMA heads for feeding.

In this embodiment, all plating metals are but not limited to copper cladding, which will not be described in detail here.

13 is a frequency response curve of the bandpass filter in this embodiment, which includes two curves S11 and S21. Curve S11 is the reflection characteristic curve of the signal port, and curve S21 is the signal transmission characteristic curve. It can be seen from the analysis of the figure that there are two transmission zeros, which are located at 0.31GHZ and 0.57GHZ respectively. These two transmission zeros greatly improve the frequency selectivity of the bandpass filter.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (7)

1. The band-pass filter is characterized by comprising a first layer of dielectric substrate (1), a second layer of dielectric substrate (2), a third layer of dielectric substrate (3), a fourth layer of dielectric substrate (4), a fifth layer of dielectric substrate (5), a first resonator (6), a second resonator (7), an input feeder (8) and an output feeder (9), wherein the first layer of dielectric substrate (1), the second layer of dielectric substrate (2), the third layer of dielectric substrate (3), the fourth layer of dielectric substrate (4) and the fifth layer of dielectric substrate (5) are stacked in sequence; the side walls of the first layer of dielectric substrate (1), the second layer of dielectric substrate (2), the third layer of dielectric substrate (3) and the fourth layer of dielectric substrate (4) are plated with metal;

the input feeder line (8) and the output feeder line (9) are fixedly arranged on the surface of the fifth layer dielectric substrate (5) facing the fourth layer dielectric substrate (4), the surface of the fifth layer dielectric substrate (5) facing the fourth layer dielectric substrate (4) is plated with metal outside the corresponding input feeder line (8) and the output feeder line (9) to form a first metal layer, and gaps are formed between the input feeder line (8) and the first metal layer and between the output feeder line (9) and the first metal layer;

the first resonator (6) is fixedly arranged on the surface, facing the third layer dielectric substrate (3), of the fourth layer dielectric substrate (4), and a first feeding point (61) extends out of the first resonator (6);

the second resonator (7) is fixedly arranged on the surface, facing the first layer dielectric substrate (1), of the second layer dielectric substrate (2), a second feeding point (71) coupled with the first feeding point (61) extends out of the second resonator (7), two sides of the surface, facing the second layer dielectric substrate (2), of the third layer dielectric substrate (3) are plated with metal to form a second metal layer, and a transmission signal passes through a middle gap (32) of the second metal layer to enable the first feeding point (61) to be coupled with the second feeding point (71);

a first metalized via hole (41) electrically connected with the first feeding point (61) and a second metalized via hole (42) opposite to the second feeding point (71) are formed in the fourth layer of dielectric substrate (4), a third metalized via hole (31) opposite to the second feeding point (71) is formed in the third layer of dielectric substrate (3), and a fourth metalized via hole (21) electrically connected with the second feeding point (71) is formed in the second layer of dielectric substrate (2);

the first feeding point (61) is electrically connected with the input feed line (8) by connecting the first metalized via (41), and the second feeding point (71) is electrically connected with the output feed line (9) by connecting the fourth metalized via (21), the third metalized via (31), and the second metalized via (42) in sequence; or the first feeding point (61) is electrically connected with the output feeder (9) by connecting the first metalized via (41), and the second feeding point (71) is electrically connected with the input feeder (8) by sequentially connecting the fourth metalized via (21), the third metalized via (31), and the second metalized via (42);

the input feeder (8) and the output feeder (9) are coupled to form a first transmission path to generate a first transmission zero point; the input feed line (8) is coupled to the output feed line (9) via the first resonator (6) and the second resonator (7) or the input feed line (8) is coupled to the output feed line (9) via the second resonator (7) and the first resonator (6) to form a second transmission path to create a second transmission zero.

2. The bandpass filter according to claim 1, wherein the first dielectric substrate (1), the second dielectric substrate (2), the third dielectric substrate (3) and the fourth dielectric substrate (4) are identical in shape and size and are concentrically stacked.

3. A bandpass filter according to claim 1 or 2, characterized in that the fifth layer dielectric substrate (5) is larger in area than the fourth layer dielectric substrate (4), the fourth layer dielectric substrate (4) is arranged in the center of the fifth layer dielectric substrate (5), and the input feed line (8) and the output feed line (9) are respectively located on both sides of the fourth layer dielectric substrate (4).

4. A bandpass filter according to claim 3, characterized in that the input feed line (8) and the output feed line (9) are microstrip lines with a characteristic impedance of 50 ohms.

5. A bandpass filter as claimed in claim 1, characterized in that the first resonator (6) and the second resonator (7) are each a spiral structure with gaps.

6. The bandpass filter according to claim 5, wherein the spiral structure is formed in a rectangular surround.

7. A band-pass filter according to claim 5 or 6, characterized in that the first resonator (6) and the second resonator (7) have opposite winding directions.

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