CN103187603A - Wide-stopband LTCC (low temperature co-fired ceramic) band-pass filter based on magnetoelectric coupling counteraction technology - Google Patents

Abstract

The invention discloses a wide stopband LTCC bandpass filter based on magnetoelectric coupling cancellation technology, which includes two quarter-wavelength resonators, a metal floor and a pair of feed structures. The resonators and feed patches are distributed over four conductor layers. The first layer is the feed layer with large feed patches and CPW feed ports, the second and fourth layers distribute two quarter-wavelength resonators, and the third layer is the ground layer. The feed patch uses broadside coupling to transfer energy to the resonator. Energy is transmitted between the resonators through side coupling. There are both magnetic coupling and electrical coupling between the two resonators. Mainly, adjusting the strength of magnetic coupling and electrical coupling can easily adjust the position of filter transmission zero. The invention has multiple transmission zero points, excellent selectivity and stop band suppression performance, and compact structure.

Description

A Wide Stopband LTCC Bandpass Filter Based on Magnetoelectric Coupling Cancellation Technology

technical field

The invention relates to a wide-stop-band band-pass filter based on LTCC technology, in particular to a band-pass filter which can be applied to a radio frequency front-end circuit by using magnetoelectric hybrid coupling to generate a plurality of transmission zero points.

Background technique

With the rapid development of the information industry, various communication systems continue to emerge, the rapid development of wireless communication technology and the increasingly tense global communication frequency bands put forward stricter requirements for microwave filters. Modern filters require high performance, small size, wide stop band, and low cost. Among them, small size and wide stopband are important indicators of single passband filter performance.

There are many methods for existing filters to achieve stop-band suppression. The first method is to use the multipath transmission of electromagnetic signals. At a certain frequency point, the phases of electromagnetic fields transmitted by multipath are opposite, cancel each other, and generate zero points. This method This can be achieved with cross-coupling or with a source-load couple; the second approach is to use a stepped impedance resonator (SIR), which pushes the second harmonic of the filter back To the frequency of about 2.5-3 times the passband center frequency, the ratio of the second harmonic center frequency to the passband center frequency depends on the structure of the SIR, using multiple step impedances with the same passband center frequency of different structures The resonators can be connected in series to suppress the stop band; the third method is to use the quarter-wavelength inversion of the transmission line. When a quarter-wavelength transmission line with one end open is connected to the input and output ports, the open end is equivalent to The input and output ports are short-circuited, so that all the electromagnetic waves are radiated back, so a transmission zero point is generated. The spur line is one of the applications. When the electrical wavelength of the spur line is equal to a quarter of the wavelength, the spur line is connected to the I/O port. The position is short-circuited, and a transmission zero point is generated at this frequency point; other methods include using an elliptic function filter, etc.

However, the existing stop-band suppression filters all have relatively complex structures, or have problems such as large size and large insertion loss.

Contents of the invention

In order to overcome the design contradiction between multiple transmission zeros of the filter mentioned above and the complex structure and large volume, the present invention provides a wide stopband LTCC bandpass filter based on magnetoelectric coupling cancellation technology. The filter adopts LTCC (Low Temperature Co-Fired Ceramic) technology, which greatly reduces the size of the bandpass filter. In addition to the advantages of miniaturization and light weight, the filter of LTCC multi-layer structure also has the characteristics of low cost, favorable for mass production, good high-frequency performance, and small insertion loss, etc. that traditional microstrip filters do not have.

The present invention adopts following technical scheme to realize:

A wide stopband LTCC bandpass filter based on magnetoelectric coupling cancellation technology, which includes four dielectric substrates and four conductor layers, the four dielectric substrates are the first dielectric plate, the second dielectric plate, and the third dielectric plate from top to bottom. A dielectric plate and a fourth dielectric plate, the four-layer dielectric substrates are all LTCC ceramic dielectric substrates; the first conductor layer is printed on the upper surface of the first dielectric substrate, and the second conductor layer is printed on the second dielectric substrate On the surface, the third conductor layer is printed on the upper surface of the third dielectric substrate, and the fourth conductor layer is printed on the upper surface of the fourth dielectric substrate; the printing adopts LTCC printing process.

Further, the first conductor layer is composed of a pair of feed structures with the same structure, and the pair of feed structures with the same structure are mirror images, and each feed structure includes a feed patch, a CPW feed port and An L-shaped metal microstrip line, the L-shaped metal microstrip line is connected to the side of the feed patch close to the symmetrical center of the aforementioned mirror image, and forms a source-load coupling with the L-shaped metal microstrip line on the other side of the symmetrical center, and the source load The coupling creates a transmission zero to the left of the filter passband; the CPW feed is connected to the third conductor layer through a ground metallized via.

Further, two quarter-wavelength resonators are distributed on the second conductor layer and the fourth conductor layer; a part of each quarter-wavelength resonator is located in the second conductor layer, and the other part is located in the fourth conductor layer Above, the two parts are connected through the second metallized via hole, the metallized via hole passes through the opening on the third conductor layer, and the metallized via hole is not in direct contact with the third conductor layer; quarter-wavelength resonance The short-circuit end of the resonator is located on the second conductor layer and connected to the third conductor layer through the first metallized via hole; the two quarter-wavelength resonators are mirror-image symmetrical on the second conductor layer and the fourth conductor layer Distribution, the quarter-wavelength resonator part on the same conductor layer generates magnetoelectric coupling through side coupling, the coupling part of the quarter-wavelength resonator on the second conductor layer is the short-circuit end of the resonator, and the magnetic coupling is main; the coupling part of the quarter-wavelength resonator on the fourth conductor layer is the open circuit end of the resonator, and is mainly electrically coupled.

Further, the third conductor layer is a metal floor, there are two openings on the third conductor layer for the metallized vias to pass through, and there is a gap between the metallized vias and the metal floor.

The present invention adopts a quarter-wavelength resonator, which effectively reduces the size of the filter compared with a half-wavelength resonator; and adopts the LTCC multi-layer structure process to manufacture, by placing feeders in different layers The chip and the resonator use metal vias to connect the microstrip lines of different layers to make the filter structure more compact; in addition, the present invention also uses different dielectric thicknesses to realize SIR (Stepped-Impedance Resonator step impedance resonance) device), which can reduce the amount of electrical coupling, effectively reduce the electrical coupling distance to achieve the effect of reducing size, and at the same time, it is more convenient to adjust the transmission zero point of the filter.

The two L-shaped metal microstrip lines on the first conductor layer of the filter form a source-load coupling, which creates a zero point on the left side of the passband; on the second conductor layer, the quarter-wavelength resonator is short-circuited In the fourth conductor layer, the open-circuited ends of the quarter-wavelength resonator are coupled to each other, and the electrical coupling is the main force. The electrical coupling and magnetic coupling cancel each other to produce three transmission zero points. The zero point position can be easily adjusted by adjusting the strength of the resonator's electrical coupling and magnetic coupling; the above two coupling methods generate multiple controllable transmission zero points, which improves the passband selectivity of the filter and suppresses the higher harmonics of the filter , a wider stop band is obtained.

Compared with the prior art, the present invention has the following advantages:

1. Adopt LTCC multi-layer technology to make the structure of the filter more compact and effectively reduce the size of the filter;

2. The source-load coupling composed of two L-shaped metal microstrip lines on the first conductor layer produces a zero point on the left side of the passband, which improves the selectivity of the filter;

3. The quarter-wavelength resonators distributed on the second conductor layer and the fourth conductor layer are coupled to each other at the short-circuit end and the open-circuit end. The short-circuit end is mainly magnetically coupled, and the open-circuit end is mainly electrically coupled. The magnetic coupling cancels each other to produce three transmission zero points. By adjusting the electric coupling and magnetic coupling strength of the resonator, the zero point position can be easily adjusted. These zero points effectively suppress the high-order harmonics of the filter, so that the filter obtains an extremely wide impedance. bring;

4. The energy transfer between the feed patch and the resonator is achieved through broadside coupling. The broadside coupling strength determines the external Q value, and the sum of the electrical coupling and magnetic coupling between two quarter-wavelength resonators determines the coupling. Coefficient K, adjusting the two quantities of Q and K can change the bandwidth, which has good flexibility.

Description of drawings

Fig. 1 is the layered schematic diagram of three-dimensional structure of the present invention.

Figure 2 is a schematic top view of the first conductor layer of the present invention.

Figure 3 is a schematic top view of the second conductor layer of the present invention.

Figure 4 is a schematic top view of the third conductor layer of the present invention.

Figure 5 is a schematic top view of the fourth conductor layer of the present invention.

Figure 6 is a graph of the frequency response characteristics of the bandpass filter embodiment of the present invention.

Detailed ways

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the specific implementation of the present invention will be further described below in conjunction with the accompanying drawings, but the implementation of the present invention is not limited thereto.

As shown in Figure 1, the embodiment of the present invention provides a wide stopband LTCC second-order bandpass filter based on magnetoelectric coupling cancellation technology. The whole filter is an LTCC multilayer structure consisting of four dielectric substrates and four layers Conductor layer composition: the first conductor layer is located on the surface of the first dielectric substrate, the second conductor layer is located between the first dielectric substrate 1 and the second dielectric substrate 2, and the third conductor layer is located between the second dielectric substrate 2 and the third dielectric substrate 3 The fourth conductor layer is located between the third dielectric substrate 3 and the fourth dielectric substrate 4; the four dielectric substrates are all LTCC ceramic dielectric substrates, the first conductor layer is printed on the upper surface of the first dielectric substrate 1, and the second The conductor layer is printed on the upper surface of the second dielectric substrate 2 , the third conductor layer is printed on the upper surface of the third dielectric substrate 3 , and the fourth conductor layer is printed on the upper surface of the fourth dielectric substrate 4 .

As shown in Figure 2, the first layer of metal conductors consists of a pair of feed structures with the same structure, which are placed symmetrically in a mirror image. Each feed structure consists of a feed patch 5, a CPW feed port 6 and an L-shaped The L-shaped metal microstrip line 7 is connected to the side of the feed patch 5 close to the center of symmetry, and forms a source-load coupling with the L-shaped metal microstrip line 7 on the other side of the symmetry center. The source-load coupling A transmission zero point is generated on the left side of the passband. Adjusting the coupling distance between the two can change the strength of the source-load coupling, thereby changing the position of the zero point on the left side of the passband; ; In addition, the feeding patch 5 realizes the energy transmission between the feeding terminal and the resonator through broadside coupling, changing the size and position of the feeding patch can change the size of the external Q value, the external Q value and the resonance The filter coupling coefficient K together determines the filter bandwidth.

As shown in Figure 3, the short-circuit ends of the two quarter-wavelength resonators are symmetrically arranged on the second layer of metal conductors, and one end of the resonators on this layer is connected to the fourth conductor layer through the second metallized via hole 13 , the fourth conductor layer is the layer where the open circuit end of the resonator is located, and the second metallized via hole 13 passes through the opening 14 above the floor layer, without direct physical contact with the floor; the short circuit end of the resonator passes through the second metallized via hole 14 Hole 13 connects to the floor. The short-circuit ends of the two resonators form side coupling, and the electromagnetic coupling strength can be adjusted by adjusting the length L13 of the metal microstrip line of the coupling part and the coupling width W3 between them. Since the coupling part is the short-circuit end of the resonator, the electromagnetic coupling is as follows: The magnetic coupling is the main effect, and the rectangle dotted circle in Figure 3 is the edge magnetic coupling area.

As shown in FIG. 4, the third conductor layer is a metal floor 9 with two openings 14 above, and the second metallized via hole 13 connecting the second layer conductor and the fourth layer conductor passes through these two openings, The radii of these two openings are larger than the second metallized via hole 13 , so as to ensure that the metallized via hole will not be physically connected to the metal floor 9 . Also connected to the metal floor are two first metallized via holes 12 connected to the short-circuit end of the second conductor layer resonator, and four ground metallized via holes 11 connected to the CPW feed port of the first conductor layer .

As shown in FIG. 5 , the open-circuit ends of the two quarter-wavelength resonators are arranged symmetrically on the fourth conductor layer, and one end of the resonators on this layer is connected to the second conductor layer through the second metallized via hole 13 . The open-circuit ends of the two resonators constitute side coupling. The length L16 of the metal microstrip line in the coupling part and the coupling width W5 between them can adjust the electromagnetic coupling strength. The rectangle dotted circle in Fig. 5 is the edge electric coupling area.

In this embodiment, the central frequency of the passband is determined by the length of the quarter-wavelength resonator, the position of the zero point on the left side of the passband is mainly determined by the source-load coupling strength, and the positions of the three zero points on the right side of the passband are mainly determined by the magnetoelectric coupling characteristics , the electrical coupling end and the magnetic coupling end of the resonator cancel each other at these three frequency points to form a transmission zero point; the external Q value of the filter is determined by the size of the feed patch, and the coupling coefficient K is determined by the electrical coupling and magnetic coupling strength of the resonator The sum of the decision, the external Q value and the coupling coefficient K jointly determine the passband bandwidth. By adjusting the resonator length, source-load coupling, and magnetoelectric coupling indicated above, this embodiment obtains the required passband and stopband characteristics.

The parameters of this embodiment are described below (only as an example, and the implementation of the present invention is not limited thereto):

As shown in Figure 2, L1 is 0.4mm, L2 is 1012 mm, L4 is 0.65mm, L5 is 0.5mm, L7 is 0.6mm, L8 is 1.27mm, W1 is 0.1mm, and W2 is 0.1mm; as shown in Figure 3 and As shown in Figure 5, L10 is 0.154mm, L11 is 0.3mm, L12 is 0.4mm, L13 is 1.8mm, L14 is 1.45mm, L15 is 0.34mm, L16 is 1.57mm, L17 is 0.44mm, W4 and W6 are the same 0.2mm, W3 is 0.23mm, W5 is 0.36mm; the thickness of the first layer of dielectric is 0.15mm, the thickness of the second layer of dielectric is 0.3mm, the thickness of the third layer of dielectric is 0.15mm, and the thickness of the fourth layer of dielectric is 0.1mm. The conductor layer is made of metallic silver, the dielectric substrate material is ceramic, the relative permittivity Er is 7.6, the dielectric loss tangent tan is 0.005, and the volume of the whole device is 3.2mm×2.8mm×0.7mm.

The response result of the filter is shown in Figure 6, which contains two curves S(1,2) and S(2,1). Due to the symmetry of the filter structure, the other two response curves S( 2, 2) and S (1, 2) are the same as S (1, 2) and S (2, 1) respectively, the filter works at 2.4Ghz, the minimum insertion loss of the passband is 1.8dB, and the echo in the passband The loss is about 30dB, and there is a transmission zero point close to the upper side frequency of the passband and the lower side frequency of the passband, which makes the filter have very good selectivity. There are two transmission zero points at 6.4Ghz and 9.1Ghz, effectively The stop band is suppressed to a large extent, and the stop band is completely suppressed below -25dB between 2.6Ghz and 9.4Ghz. It can be seen that the filter has very good selectivity and wide stop band suppression, and has good in-band characteristics.

In summary, the wide stopband LTCC bandpass filter based on the magnetoelectric coupling cancellation technology provided by the present invention has the excellent performance of small size, wide stopband, and small insertion loss, and can be processed into a chip component, which is easy to integrate with other circuit modules , can be widely used in the radio frequency front end of the wireless communication system.

The embodiment described above is a preferred embodiment of the present invention, and is not intended to limit the present invention. Based on the embodiments of the present invention, any modifications, equivalent replacements, and other embodiments obtained by those skilled in the art without creative work based on the present invention all belong to the protection scope of the embodiments of the present invention .

Claims (4)

1. based on the wide stopband LTCC band pass filter of magneto-electric coupled cancellation technology, it is characterized in that comprising four layers of medium substrate and four layers of conductor layer, four layers of medium substrate are followed successively by first dielectric-slab (1), second dielectric-slab (2), the 3rd dielectric-slab (3) and the 4th dielectric-slab (4) from top to bottom, and described four layers of medium substrate are LTCC ceramic dielectric substrate; Described first conductor layer is printed on first medium substrate (1) upper surface, second conductor layer is printed on second medium substrate (2) upper surface, the 3rd conductor layer is printed on the 3rd medium substrate (3) upper surface, and the 4th conductor layer is printed on the 4th medium substrate (4) upper surface; The LTCC typography is adopted in described printing.

2. the wide stopband LTCC band pass filter based on magneto-electric coupled cancellation technology according to claim 1, described first conductor layer is made up of the identical feed structure of a pair of structure, this is the mirror image symmetry to the identical feed structure of structure, each feed structure comprises a feed paster (5), a CPW feed mouth (6) and a L type metal micro-strip line (7), L type metal micro-strip line (7) is connected feed paster (5) near a side of aforementioned mirror image symmetrical centre, and constituting source load coupling with the L type metal micro-strip line (7) of symmetrical centre opposite side, the source load is coupling in the filter passband left side and has produced a transmission zero; CPW feed mouth is connected to the 3rd conductor layer (9) by ground metallization via hole (11).

3. the wide stopband LTCC band pass filter based on magneto-electric coupled cancellation technology according to claim 1 is characterized in that being distributed with on second conductor layer and the 4th conductor layer two quarter-wave resonance devices; All some is positioned at second conductor layer to each quarter-wave resonance device, another part is positioned on the 4th conductor layer, these two parts link to each other by the second metallization via hole (13), metallization via hole (13) passes the perforate (14) that is positioned on the 3rd conductor layer, and metallization via hole (13) does not directly contact with the 3rd conductor layer; The short-circuit end of quarter-wave resonance device is positioned at second conductor layer and is connected to the 3rd conductor layer by the first metallization via hole (12); Described two quarter-wave resonance devices all are mirror image and are symmetrically distributed on second conductor layer and the 4th conductor layer, the quarter-wave resonance device part that is positioned on the same conductor layer produces magneto-electric coupled by the limit coupling, the coupling unit of quarter-wave resonance device on second conductor layer is the resonator short-circuit end, based on magnetic coupling; The coupling unit of quarter-wave resonance device on the 4th conductor layer is the resonator open end, based on electric coupling.

4. the wide stopband LTCC band pass filter based on magneto-electric coupled cancellation technology according to claim 3, described the 3rd conductor layer is metal floor (9), there are two perforates (14) to pass for described metallization via hole (13) on the 3rd conductor layer, and leave the gap between metallization via hole (13) and the metal floor.

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