High-frequency high-suppression low-pass filter

Abstract

The utility model discloses a high-frequency high-suppression low-pass filter, which comprises a porcelain body, a first inductor, a second inductor, a third inductor, a fourth inductor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor and a fifth capacitor, a first inductor, a second inductor, a third inductor and a fourth inductor which are electrically connected in sequence are arranged in the left side of the porcelain body to form a series inductor middle layer, and a first capacitor, a third capacitor and a fifth capacitor are arranged above the inductor middle layer and electrically connected with the series inductor middle layer. The second capacitor and the fourth capacitor are arranged below the inductor middle layer and electrically connected with the series inductor middle layer, the capacitor and the inductor on the left side form a first filter circuit, a second filter circuit symmetrical to the first filter circuit is arranged on the right side of the porcelain body and electrically connected with the first filter circuit, and the first inductor is connected to an input pin. The output end of the second filter circuit is connected to the output pin, and the input pin and the output pin are arranged on the upper surface of the porcelain body. According to the utility model, two filters are cascaded, so that high suppression can be realized.

Description

Technical Field

[0001] The utility model relates to a high-frequency high-inhibition low-pass filter, belonging to the technical field of LTCC low-temperature co-fired ceramic filters. Background Art

[0002] A low-pass filter is an electronic filtering device that allows signals below the cutoff frequency to pass, but blocks signals above it. Conventional low-pass filter assembly utilizes a reflow soldering process, which can lead to contamination and the risk of over-reflowing the entire board. Assembly is achieved by connecting surface electrodes to the circuit board using bonding techniques.

[0003] In addition, conventional filters are difficult to achieve high suppression, and debugging is very difficult using high-order filters. Summary of the Invention

[0004] The technical problem to be solved by the utility model is to provide a high-frequency high-inhibition low-pass filter, which can meet the requirements of high inhibition and bonding process and does not require reflow soldering.

[0005] The technical solution adopted by the present invention is: a high-frequency, high-suppression, low-pass filter, including a porcelain body, a first inductor, a second inductor, a third inductor, a fourth inductor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor and a fifth capacitor. The first inductor, the second inductor, the third inductor and the fourth inductor are arranged in sequence through silver electrodes on the left side of the porcelain body to form a series inductor. The first capacitor, the third capacitor and the fifth capacitor are arranged below the inductor layer to form a grounding capacitor with the ground. The second capacitor and the fourth capacitor are arranged above the inductor middle layer and are connected in parallel with the second inductor and the third inductor. The capacitors and inductors on the left side form a first filter circuit. A second filter circuit symmetrical to the first filter circuit is arranged on the right side of the porcelain body and is electrically connected to the first filter circuit. The first inductor is connected to the input pin, and the second filter circuit is connected to the output pin after mirroring. The input pin and the output pin are arranged on the upper surface of the porcelain body, and the low-pass filter is connected to the circuit board through a gold wire mesh cable.

[0006] Furthermore, the above-mentioned first capacitor, third capacitor and fifth capacitor include three first upper electrode plates and a common lower electrode plate arranged in gaps, and the common lower electrode plate is connected to the common ground plane on the bottom surface of the porcelain body through a silver electrode column. The second capacitor and the fourth capacitor both include a second upper electrode plate and a first lower electrode plate.

[0007] Furthermore, the common lower electrode plate is connected to four test ground terminals through a plurality of inner electrodes. The four test ground terminals are arranged on the top surface of the porcelain body and are located at two on each side of each input pin and output pin.

[0008] Furthermore, the second inductor and the third inductor are arranged in a front-to-back staggered manner in the ceramic body.

[0009] The beneficial effects of the present invention are as follows: compared with the prior art, the first filter circuit and the second filter circuit cascaded in the present invention can achieve high frequency and high suppression, reduce the difficulty of debugging, and are connected to the product circuit board by a gold wire mesh connection method to reduce pollution. The capacitor structure is arranged with a compact structure, and the upper pole capacitor is far away from the ground terminal to avoid parasitic interference from the ground terminal and improve the stability of the filter. Through simulation data, the two seventh-order low-pass filters cascaded in the present invention can meet the design requirements of passband frequency DC-13.48GHz, stopband 14GHz, and loss greater than 20dB. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a schematic diagram of the three-dimensional structure of a low-pass filter;

[0011] Figure 2 This is a schematic diagram of the three-dimensional structure of the low-pass filter from another perspective;

[0012] Figure 3 It is a schematic diagram of the forward-looking structure of the low-pass filter;

[0013] Figure 4 It is a schematic diagram of the left-view structure of the low-pass filter;

[0014] Figure 5 It is a schematic diagram of the low-pass filter structure from a top view;

[0015] Figure 6 This is a schematic diagram of the simulation structure of the low-pass filter forward-looking circuit;

[0016] Figure 7 It is the insertion loss and rejection curve of the low-pass filter. DETAILED DESCRIPTION

[0017] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0018] Example 1: Figure 1-7A high-frequency, high-rejection, low-pass filter comprises a ceramic body 1, a first inductor 2, a second inductor 3, a third inductor 4, a fourth inductor 5, a first capacitor 6, a second capacitor 7, a third capacitor 8, a fourth capacitor 9, and a fifth capacitor 10. The left side of the ceramic body 1 is provided with the first inductor 2, the second inductor 3, the third inductor 4, and the fourth inductor 5, which are electrically connected in sequence to form a series inductor intermediate layer. The first capacitor 6, the third capacitor 8, and the fifth capacitor 10 are arranged above the inductor intermediate layer and are electrically connected to the series inductor intermediate layer. The second capacitor 7 and the fourth capacitor 9 are arranged below the inductor intermediate layer and are electrically connected to the series inductor intermediate layer. It is electrically connected to the middle layer of the series inductor, and the capacitor and inductor on the left form a first filter circuit. A second filter circuit symmetrical to the first filter circuit is arranged on the right side of the porcelain body 1 and is electrically connected to the first filter circuit. The first inductor 2 is connected to the input pin 15, and the output end of the second filter circuit is connected to the output pin 16. The input pin 15 and the output pin 16 are arranged on the upper surface of the porcelain body 1 and are respectively connected to the input end of the first filter and the output end of the second filter through the input internal electrode 17 and the output internal electrode 18. The low-pass filter is connected to the circuit board through a gold wire mesh cable.

[0019] Usually the input and output terminals of a product are led out from the side. The utility model introduces the input and output terminals from the top surface, and welding can be achieved through micro-assembly. Structurally, the input and output are led to the surface of the product by designing long through holes, thereby achieving lead-out and meeting the welding process requirements of gold wire bonding.

[0020] In order to save space and increase the grounding effect, the first capacitor 6, the third capacitor 8 and the fifth capacitor 10 include three first upper electrode plates and a common lower electrode plate arranged in gaps. The common lower electrode plate is connected to the common grounding surface 12 on the bottom surface of the porcelain body 1 through a short terminal 11. The second capacitor 7 and the fourth capacitor 9 both include a second upper electrode plate and a first lower electrode plate. This structure can improve the grounding effect.

[0021] The low-pass filter circuit includes a first filter circuit and a second filter circuit connected in series. The first filter circuit includes an input terminal, a first inductor 2, a second inductor 3, a third inductor 4 and a fourth inductor 5 electrically connected in sequence. One end of the first capacitor 6, the third capacitor 8 and the fifth capacitor 10 are electrically connected between the first inductor 2 and the second inductor 3, between the second inductor 3 and the third inductor 4 and between the third inductor 4 and the fourth inductor 5, respectively, and the other end is grounded. One end of the second capacitor 7 and the fourth capacitor 9 are both electrically connected between the second inductor 3 and the third inductor 4, and the other end is electrically connected between the first inductor 2 and the second inductor 3 and between the second inductor 2 and the third inductor 3, respectively. The second filter circuit is symmetrical with the first filter circuit and is connected to the output terminal.

[0022] To facilitate testing, the common lower electrode plate is connected to four test ground terminals 14 through multiple internal electrodes 13. The four test ground terminals 14 are arranged on the top surface of the porcelain body 1 and are located on each side of each input pin 15 and output pin 16. The ground terminals are led to the upper side of the porcelain body to facilitate wiring during testing and improve test efficiency.

[0023] In order to achieve adjustable inductance, the second inductor 3 and the third inductor 4 are arranged in a front-to-back staggered manner in the porcelain body 1. The front-to-back staggered arrangement can free up more space for adjusting the inductance. Because the inductance value of the inductor is related to the length, the larger the space, the more convenient it is to adjust.

[0024] Embodiment: A method for preparing a low-pass filter, the method comprising the following steps:

[0025] S1. Ingredients: The dielectric constant of the material selected for the product is 5.1, and the powder is ball-milled to the set particle size (0.3-0.5μm);

[0026] S2, tape casting: the milled ingredients are prepared into slurry, and the tape casting technology is used to obtain high-precision green porcelain tapes of different thicknesses (the key film thickness is 45μm);

[0027] S3. Cutting: Cutting the raw porcelain tape into raw porcelain tapes of various thicknesses of a set size (usually 6 inches long);

[0028] S4. Drilling: according to the prepared drilling pattern, use a laser drilling machine to drill holes on the raw porcelain strip where holes need to be drilled;

[0029] S5. Printing: The printing method is screen printing. The designed three-dimensional graphics are prepared on film. After exposure, the product's inductors and capacitors are transferred to a 400-mesh steel screen covered with photosensitive adhesive to form a printing jig. The thickness of the photosensitive adhesive coating is controlled to be 32μm~55μm; the printing GAP value is controlled to be 0.5mm~3mm; the printing scraper pressure is controlled to be 0.05MPa~0.20MPa; the scraper step speed is 0.01m / s~0.10m / s; each layer of the design model containing the inductor or capacitor pattern is printed on a green porcelain tape of corresponding thickness. The printed inductor line width error is within 2μm, the inductor thickness is 12-15μm, and the printed capacitor length and width error is within 5μm, and the capacitor thickness is 8-10μm.

[0030] S6. Lamination: Lamination of the printed green ceramic tapes according to the design sequence using special equipment (such as a fully automatic alignment lamination machine);

[0031] S7, Isostatic Pressing: Final pressing is performed on the laminated diaphragm by isostatic pressing. The maximum isostatic pressing temperature is 70℃~75℃; the holding time is 600s~900s; the holding pressure is 5100psi~8300psi to form a bar block.

[0032] S8, cutting: split the bar block into 6.95mm*3.24mm, with an error of ±0.1mm and independent product units;

[0033] S9, debinding: Debinding the split product for 36 hours according to the debinding curve with a dielectric constant of 5.1;

[0034] S10, sintering: the debinding product is sintered in a tunnel furnace; the tunnel furnace belt speed is 45mm / min, there are 12 sintering temperature zones, the sintering temperature is 875℃, and the holding time is 50min~60min;

[0035] S11, chamfering: chamfering the sintered product;

[0036] S12, Silver Dipping: Use the fully automatic terminal electrode silver dipping machine to coat the external terminal electrodes of the chamfered products;

[0037] S13, Silver Burning: Silver burning process is performed on the silver-coated product; silver burning is performed using a tunnel furnace; there are 6 sintering temperature zones, sintering temperature: 715℃, holding time: 20min~25min;

[0038] S14, electroplating: electroplating the silver-sintered product into the final product.

[0039] The above is only a specific implementation method of the present invention, but the scope of protection of the present invention is not limited to this. Any technician familiar with the technical field can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A high-frequency, high-suppression low-pass filter, characterized in that: The invention comprises a ceramic body (1), a first inductor (2), a second inductor (3), a third inductor (4), a fourth inductor (5), a first capacitor (6), a second capacitor (7), a third capacitor (8), a fourth capacitor (9) and a fifth capacitor (10); the first inductor (2), the second inductor (3), the third inductor (4) and the fourth inductor (5) are arranged on the left side of the ceramic body (1) to form a series inductor middle layer; the first capacitor (6), the third capacitor (8) and the fifth capacitor (10) are arranged above the inductor middle layer and are electrically connected to the series inductor middle layer. The second capacitor (7) and the fourth capacitor (9) are arranged below the inductor middle layer and are electrically connected to the series inductor middle layer. The capacitors and inductors on the left side form a first filter circuit. A second filter circuit symmetrical to the first filter circuit is arranged on the right side of the porcelain body (1) and is electrically connected to the first filter circuit. The first inductor (2) is connected to the input pin (15). The output end of the second filter circuit is connected to the output pin (16). The input pin (15) and the output pin (16) are arranged on the upper surface of the porcelain body (1). The low-pass filter is connected to the circuit board through a gold wire mesh cable.

2. The low-pass filter according to claim 1, wherein: The first capacitor (6), the third capacitor (8) and the fifth capacitor (10) include three first upper electrode plates and a common lower electrode plate arranged at intervals. The common lower electrode plate is connected to a common ground plane (12) on the bottom surface of the porcelain body (1) through a short terminal (11). The second capacitor (7) and the fourth capacitor (9) both include a second upper electrode plate and a first lower electrode plate.

3. The low-pass filter according to claim 1, wherein: The common lower electrode plate is connected to four test ground terminals (14) through a plurality of inner electrodes (13). The four test ground terminals (14) are arranged on the top surface of the porcelain body (1) and are located at two on each side of each input pin (15) and output pin (16).

4. The low-pass filter according to claim 1, wherein: The second inductor (3) and the third inductor (4) are arranged in a staggered manner in front and back in the porcelain body (1).

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