A LTCC-type symmetrical non-reflective low-pass filter based on DGS

Abstract

The invention discloses a LTCC-type symmetrical non-reflection low-pass filter based on DGS, which belongs to the field of microwave technology. The non-reflection low-pass filter is composed of three symmetrical inductors, three capacitors and three resistors. The filter adopts a single shielding layer, and the shielding layer adopts a grid defect ground structure. It is realized by using LTCC process technology, and has the advantages of good stopband non-reflection performance, small component size, component high temperature resistance, low processing cost, good working stability, good material consistency, good environmental protection, etc. It can be widely used in 5G mobile communications in microwave bands, phased array radars, Beidou navigation systems and other satellite communications, and systems and equipment with high requirements on electrical properties, material consistency, thermomechanical properties, temperature stability, processability and anti-interference.

Description

Technical Field

[0001] The invention relates to the field of microwave technology, and in particular to a LTCC type symmetrical non-reflective low-pass filter based on DGS. Background Art

[0002] Filters have the function of filtering fixed frequency signals and are widely used in communication and radio frequency systems. According to the processing method of the filter stopband signal, they can be divided into reflective filters and non-reflective filters. The reflective filter's stopband signal is reflected back to the signal input end, while the non-reflective filter absorbs and consumes the reflected signal through a certain circuit structure.

[0003] LTCC, or low temperature co-fired ceramic, is a thick film process with high stability, high quality factor and high integration. Compared with other materials, ceramic materials have high stability and a wide range of dielectric constants, making them suitable for the manufacture of microwave devices.

[0004] However, compared with the mature research and design of traditional reflective filters, there are few studies on non-reflective filters, and there is a lack of relevant research and design in China. In many practical applications, for example, mixers are very sensitive to all out-of-band signal changes; the stability of high-gain amplifiers is affected by out-of-band signal feedback in the packaging environment; the reliability and stability of high-power transmitters are limited by out-of-band reflection signals.

[0005] There are two types of existing absorption filter designs: one is to use a single-terminal prototype filter as the absorption load, and to form different filters with complementary admittance curves in the working mode of a duplexer or multiplexer to achieve passband and stopband matching; the other is to use a reflection filter and two 3dB directional couplers to cancel out the stopband reflection energy. These two types of filters use a large number of components, a complex design process, and large component size.

[0006] The existing non-reflection design has the following disadvantages:

[0007] (1) Using a duplexer or multiplexer structure to design a reflectionless low-pass filter requires dual high-pass and low-pass paths and complementary phase-frequency curves. The design and debugging are difficult and the components are large;

[0008] (2) Using a reflective filter and two 3dB directional couplers to design a non-reflective low-pass filter has many components, a large volume, and a large insertion loss;

[0009] (3) The symmetrical circuit design based on IPD process is adopted, which has low stability and heat dissipation. Summary of the invention

[0010] In view of the above technical problems existing in the prior art, the present invention provides a DGS-based LTCC-type symmetrical non-reflective low-pass filter with a simple and symmetrical circuit structure, and reduces the influence of the parasitic capacitance of the spiral inductor on the absorption load circuit or component performance.

[0011] The present invention discloses a LTCC type symmetrical non-reflection low-pass filter based on DGS, comprising an input port P1, a first connection port P2, a first grounding port P3, a second grounding port P4, a second connection port P5 and an output port P6, a first spiral inductor L1, a second spiral inductor L2, a third spiral inductor L3, a first capacitor C1, a second capacitor C2, a third capacitor C3, a third connection line Li n3, a defective ground structure shielding layer DGS, a first isolation resistor R1 and a second isolation resistor R2;

[0012] The first spiral inductor L1 has three layers, the first layer is connected to the input port P1, and the third layer is connected to the output port P6;

[0013] The second spiral inductor L2 has two layers, the second layer is connected to the first connection port P2, and the first layer is connected to the first ground port P3;

[0014] The third spiral inductor L3 has two layers, the second layer is connected to the second connection port P5, and the first layer is connected to the second ground port P4;

[0015] The first capacitor C1 has three layers, the second layer is connected to the input port P1, and the first layer and the third layer are respectively connected to the first connection port P2;

[0016] The second capacitor C2 has three layers, the second layer is connected to the output port P6, and the first and third layers are connected to the second connection port P5;

[0017] The third capacitor C3 has two layers, the first layer is connected to the defective ground structure shielding layer DGS;

[0018] The first connection port P2 is connected to the first isolation resistor R1, the first isolation resistor R1 is connected to the third connection line Lin3, and the third connection line Lin3 is connected to the second isolation resistor R2 and the second layer of the third capacitor C3 respectively;

[0019] An outer end of the second isolation resistor R2 is connected to the second connection port P5.

[0020] Preferably, the second layer of the third capacitor C3 is connected to the third connection line Lin3 via the first connection column H1; a first through hole K1 exists on the first layer of the third capacitor C3, and the first connection column H1 passes through the first through hole.

[0021] Preferably, the input port P1 , the first connection port P2 , the first ground port P3 , the second ground port P4 , and the second connection port P5 are 50 ohm impedance ports.

[0022] Preferably, the input port P1 , the first connection port P2 , the first ground port P3 , the second ground port P4 , the second connection port P5 and the output port P6 are external package pins.

[0023] Preferably, the defective ground structure shielding layer DGS is printed inside the filter and adopts a large grid defective ground structure.

[0024] Preferably, the first isolation resistor R1 and the second isolation resistor R2 are of embedded structure.

[0025] Preferably, the impedance of the first isolation resistor R1 and the second isolation resistor R2 is 50 ohms.

[0026] Preferably, the reflection-free low-pass filter is a low-temperature co-fired ceramic component.

[0027] Preferably, the present invention further includes a first connecting line Li n1 and a second connecting line Li n2.

[0028] An outer end of the first connection line Li n1 is connected to the first connection port P2, and an inner end of the first connection line Li n1 is connected to the first isolation resistor R1;

[0029] An inner end of the second connection line Li n2 is connected to an outer end of the second isolation resistor R2 , and an outer end of the second connection line Li n2 is connected to the second connection port P5 .

[0030] Preferably, the input port P1, the first connection port P2, the first ground port P3, the second ground port P4, the second connection port P5 and the output port P6 are distributed on the left and right sides;

[0031] The third capacitor C3 is arranged on the upper side of the defective ground structure shielding layer DGS;

[0032] The first isolation resistor R1 and the second isolation resistor R2 are arranged on the upper side of the third capacitor C3;

[0033] The second spiral inductor L2 and the third spiral inductor L3 are arranged on the upper side of the first isolation resistor R1;

[0034] The first spiral inductor L1 is arranged on the upper side of the second spiral inductor L2;

[0035] The first capacitor C1 and the second capacitor C2 are arranged on the upper side of the first spiral inductor L1;

[0036] Form a layered structure.

[0037] Compared with the prior art, the invention has the following beneficial effects: a symmetrical design is adopted, the circuit structure is simple and symmetrical, and the design and development are convenient; the microwave device manufactured by the LTCC process has good high temperature resistance and can carry a large current; the LTCC process can produce dozens of layers of substrates, and the passive devices are buried, which reduces the interference of other assembled components and improves the integration; under the premise of extremely low reflection loss in both the passband and the stopband, the components have the characteristics of small size, simple structure, good stability, high reliability, high temperature resistance, and good material consistency; a defective ground structure shielding layer is adopted to reduce the influence of the parasitic capacitance of the spiral inductor on the absorption load circuit or component performance; the circuit structure is simple, and a reflection-free filter with any frequency and stopband requirements can be realized by adjusting the combination of the spiral inductor and the capacitor. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a front view of the present invention;

[0039] Figure 2 is a side view of the present invention;

[0040] Figure 3 It is a graph of insertion loss and return loss of performance test;

[0041] Figure 4 It is the standing wave coefficient curve of the performance test;

[0042] Figure 5 It is a schematic diagram of the stacking structure of the present invention.

[0043] Description of the markings in the figure:

[0044] Input port P1, first connection port P2, first ground port P3, second ground port P4, second connection port P5, output port P6; first spiral inductor L1, second spiral inductor L2, third spiral inductor L3, first capacitor C1, second capacitor C2, third capacitor C3, first connecting line Li n1, second connecting line Li n2, third connecting line Li n3; first through hole K1, first connecting column H1, defective ground structure shielding layer DGS; first isolation resistor R1 and second isolation resistor R2. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0047] A LTCC type symmetrical non-reflective low-pass filter based on DGS, such as Figure 1 , Figure 2 and Figure 5 As shown, it includes an input port P1, a first connection port P2, a first grounding port P3, a second grounding port P4, a second connection port P5 and an output port P6, a first spiral inductor L1, a second spiral inductor L2, a third spiral inductor L3, a first capacitor C1, a second capacitor C2, a third capacitor C3, a third connection line Li n3, a defective ground structure shielding layer DGS, a first isolation resistor R1 and a second isolation resistor R2;

[0048] The first spiral inductor L1 has three layers, the first layer is connected to the input port P1, and the third layer is connected to the output port P6;

[0049] The second spiral inductor L2 has two layers, the second layer is connected to the first connection port P2, and the first layer is connected to the first ground port P3;

[0050] The third spiral inductor L3 has two layers, the second layer is connected to the second connection port P5, and the first layer is connected to the second ground port P4;

[0051] The first capacitor C1 has three layers, the second layer is connected to the input port P1, and the first layer and the third layer are respectively connected to the first connection port P2;

[0052] The second capacitor C2 has three layers, the second layer is connected to the output port P6, and the first and third layers are connected to the second connection port P5;

[0053] The third capacitor C3 has two layers, the first layer is connected to the defective ground structure shielding layer DGS;

[0054] The first connection port P2 is connected to the first isolation resistor R1, the first isolation resistor R1 is connected to the third connection line Lin3, and the third connection line Lin3 is connected to the second isolation resistor R2 and the second layer of the third capacitor C3 respectively;

[0055] An outer end of the second isolation resistor R2 is connected to the second connection port P5.

[0056] The present invention adopts a symmetrical design, and the circuit structure is simple and symmetrical, which is convenient for design and development; the microwave device manufactured by the LTCC process has good high temperature resistance and can carry a large current. The LTCC process can produce dozens of layers of substrates, and the passive devices are buried, which reduces the interference of other assembled components and improves the integration; under the premise that both the passband and the stopband have extremely low reflection loss, the components are small in size, simple in structure, good in stability, high in reliability, high in temperature resistance, and good in material consistency; the defective ground structure shielding layer is adopted to reduce the influence of the spiral inductor parasitic capacitance on the absorption load circuit or component performance; the circuit structure is simple, and by adjusting the combination of spiral inductor and capacitor, a non-reflection filter with any frequency and stopband requirements can be realized. It can be widely used in 5G mobile communications, phased array radars, Beidou navigation systems and other satellite communications in the microwave band, and systems and equipment with high requirements for electrical properties, material consistency, thermomechanical properties, temperature stability, processability and anti-interference.

[0057] The second layer of the third capacitor C3 is connected to the third connection line Li n3 through the first connection column H1; there is a first through hole K1 on the first layer of the third capacitor C3, and the first connection column H1 passes through the first through hole K1. The second layer of the third capacitor C3 and the third connection line Li n3 are connected through the structure of the first through hole K1 and the first connection column H1, so that the structure of the present invention is compact, the circuit structure is optimized, and the component volume is reduced.

[0058] The input port P1, the first connection port P2, the first ground port P3, the second ground port P4, and the second connection port P5 are 50 ohm impedance ports. The input port P1, the first connection port P2, the first ground port P3, the second ground port P4, the second connection port P5, and the output port P6 are external package pins. The 6-port external electrode design is adopted to optimize the circuit structure and reduce the component volume.

[0059] The defective ground structure shielding layer DGS is printed inside the non-reflective low filter and adopts a large grid defective ground structure. The first isolation resistor R1 and the second isolation resistor R2 adopt an embedded structure with an impedance of 50 ohms. The use of built-in resistors improves the integration of components.

[0060] The non-reflective low-pass filter of the present invention is a low temperature co-fired ceramic (LTCC) with very high temperature stability and consistency, and also has a certain strength of green tape. The three-dimensional integration and defect structure as well as embedded resistors and packaging are adopted to make the components more integrated, smaller in size and better in stability.

[0061] like Figure 1 and Figure 2As shown, it also includes a first connection line Lin1 and a second connection line Lin2. The outer end of the first connection line Lin1 is connected to the first connection port P2, and the inner end of the first connection line Lin1 is connected to the first isolation resistor R1; the inner end of the second connection line Lin2 is connected to the outer end of the second isolation resistor R2, and the outer end of the second connection line Lin2 is connected to the second connection port P5.

[0062] The input port P1, the first connection port P2, the first ground port P3, the second ground port P4, the second connection port P5 and the output port P6 are arranged on the left and right sides; the third capacitor C3 is arranged on the upper side of the defective ground structure shielding layer DGS; the first isolation resistor R1 and the second isolation resistor R2 are arranged on the upper side of the third capacitor C3; the second spiral inductor L2 and the third spiral inductor L3 are arranged on the upper side of the first isolation resistor R1; the first spiral inductor L1 is arranged on the upper side of the second spiral inductor L2; the first capacitor C1 and the second capacitor C2 are arranged on the upper side of the first spiral inductor L1; forming a stacked structure. The stacked structure of LTCC reduces the volume of the components.

[0063] In a specific embodiment, a symmetrical non-reflective low-pass filter with a size of 2.5 mm × 1.6 mm × 0.94 mm was prepared and tested. Figure 3 and Figure 4 shown. Figure 3 The horizontal axis is the frequency, and the vertical axis is the decibel ratio; Figure 4 In the figure, the horizontal axis is frequency and the vertical axis is standing wave ratio. From the test data and the figure, it can be concluded that the passband distribution is DC to 2.45GHz, the insertion loss of the input port is better than -1.3dB, and the attenuation of the stopband range of 4GHz to 12GHz is less than -15dB; in the frequency range of DC to 12GHz, the return loss of the incident port is less than -20dB, and the standing wave ratio is better than 1.26.

[0064] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A LTCC type symmetrical non-reflective low-pass filter based on DGS, characterized in that: The invention comprises an input port (P1), a first connection port (P2), a first ground port (P3), a second ground port (P4), a second connection port (P5), an output port (P6), a first spiral inductor (L1), a second spiral inductor (L2), a third spiral inductor (L3), a first capacitor (C1), a second capacitor (C2), a third capacitor (C3), a third connection line (Lin3), a defective ground structure shielding layer (DGS), a first isolation resistor (R1), and a second isolation resistor (R2); The first spiral inductor (L1) has three layers, the first layer is connected to the input port (P1), and the third layer is connected to the output port (P6); The second spiral inductor (L2) has two layers, the second layer is connected to the first connection port (P2), and the first layer is connected to the first ground port (P3); The third spiral inductor (L3) has two layers, the second layer is connected to the second connection port (P5), and the first layer is connected to the second ground port (P4); The first capacitor (C1) has three layers, the second layer is connected to the input port (P1), and the first layer and the third layer are respectively connected to the first connection port (P2); The second capacitor (C2) has three layers, the second layer is connected to the output port (P6), and the first layer and the third layer are connected to the second connection port (P5); The third capacitor (C3) has two layers, the first layer is connected to the defective ground structure shielding layer (DGS); The first connection port (P2) is connected to the first isolation resistor (R1), the first isolation resistor (R1) is connected to the third connection line (Lin3), and the third connection line (Lin3) is respectively connected to the second isolation resistor (R2) and the second layer of the third capacitor (C3); The outer end of the second isolation resistor (R2) is connected to the second connection port (P5); The input port (P1), the first connection port (P2), the first ground port (P3), the second ground port (P4), the second connection port (P5) and the output port (P6) are arranged on the left and right sides; The third capacitor (C3) is arranged on the upper side of the defective ground structure shielding layer (DGS); The first isolation resistor (R1) and the second isolation resistor (R2) are arranged on the upper side of the third capacitor (C3); The second spiral inductor (L2) and the third spiral inductor (L3) are arranged on the upper side of the first isolation resistor (R1); The first spiral inductor (L1) is arranged on the upper side of the second spiral inductor (L2); The first capacitor (C1) and the second capacitor (C2) are arranged on the upper side of the first spiral inductor (L1); Form a layered structure; The first isolation resistor (R1) and the second isolation resistor (R2) are of embedded structure.

2. The LTCC type symmetrical non-reflective low-pass filter according to claim 1, characterized in that: The second layer of the third capacitor (C3) is connected to the third connection line (Lin3) through the first connection column (H1); the first layer of the third capacitor (C3) is provided with a first through hole (K1), and the first connection column (H1) passes through the first through hole.

3. The LTCC type symmetrical non-reflective low-pass filter according to claim 1, characterized in that: The input port (P1), the first connection port (P2), the first ground port (P3), the second ground port (P4), and the second connection port (P5) are 50 ohm impedance ports.

4. The LTCC type symmetrical non-reflective low-pass filter according to claim 1, characterized in that: The input port (P1), the first connection port (P2), the first ground port (P3), the second ground port (P4), the second connection port (P5) and the output port (P6) are external package pins.

5. The LTCC type symmetrical non-reflective low-pass filter according to claim 1, characterized in that: The defective ground shielding layer (DGS) is printed inside the non-reflective low filter and adopts a large grid defective ground structure.

6. The LTCC type symmetrical non-reflective low-pass filter according to claim 1, characterized in that: The impedance of the first isolation resistor (R1) and the second isolation resistor (R2) is 50 ohms.

7. The LTCC type symmetrical non-reflective low-pass filter according to claim 1, characterized in that: The non-reflective low-pass filter is a low-temperature co-fired ceramic component.

8. The LTCC type symmetrical non-reflective low-pass filter according to claim 1, characterized in that: Also includes a first connecting line (Lin1) and a second connecting line (Lin2), The outer end of the first connecting line (Lin1) is connected to the first connecting port (P2), and the inner end of the first connecting line (Lin1) is connected to the first isolation resistor (R1); The inner end of the second connecting line (Lin2) is connected to the outer end of the second isolation resistor (R2), and the outer end of the second connecting line (Lin2) is connected to the second connecting port (P5).

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