UHF band subminiature band-pass filter

Abstract

The utility model discloses a UHF frequency band subminiature band-pass filter, which comprises a bottom copper sheet and a top copper sheet, the bottom copper sheet is used as a reference ground, the top copper sheet is provided with a wiring area, and an input feeder line, an output feeder line, a plurality of resonators, a chip capacitor, a metal grounding via hole and the like which are realized by adopting microstrip lines are arranged in the wiring area at two sides of the wiring area. The filter designed by the utility model can be realized on a miniaturized PCB (Printed Circuit Board), has good performance consistency and excellent insertion loss, can be assembled and produced by adopting a common SMT (Surface Mount Technology) process, and is high in efficiency and low in cost.

Description

Technical Field

[0001] The utility model belongs to the technical field of bandpass filter design, and in particular relates to an ultra-small bandpass filter in a UHF frequency band. Background Art

[0002] Since the available electromagnetic spectrum is limited, filters play an important role in many RF / microwave applications to separate or combine signals of different frequencies. RF / microwave filters come in many forms, divided into lumped element (capacitor, inductor) filters and distributed circuit (such as waveguide, coaxial line and microstrip, etc.) filters.

[0003] The integration of printed circuit boards (PCBs) in the current RF communication field is becoming increasingly higher, requiring filters to have the characteristics of easy integration with PCBs, small size, high performance, and low cost. Unlike general RF devices such as broadband amplifiers and broadband mixers, filters have strong customization properties (passband frequency, insertion loss, out-of-band suppression, etc.), and it is often difficult to find off-the-shelf products that fully match application requirements. Therefore, customized filters are often required, and customization directly leads to high costs.

[0004] One solution to the high cost problem is to design filters on PCB. Currently, low-cost filters that are easy to integrate with PCB include lumped components (capacitors, inductors) and microstrip filters. Due to the accuracy of lumped components (capacitors, inductors), the performance consistency of lumped component bandpass filters is poor, and they need to be debugged manually, which brings huge labor and time costs and cannot be mass-produced; microstrip bandpass filters have good consistency and do not require debugging, but their size is related to frequency, and they are larger in the UHF band, and the insertion loss is larger when implemented on conventional FR4 boards. Utility Model Content

[0005] Technical purpose: In order to solve the above technical problems, the utility model proposes a UHF band ultra-small bandpass filter, which can be implemented on a miniaturized PCB. The filter has good performance consistency and excellent insertion loss. It can be assembled and produced using ordinary SMT technology with high efficiency and low cost.

[0006] Technical solution: To achieve the above technical objectives, the utility model adopts the following technical solution:

[0007] A UHF band ultra-small bandpass filter, comprising a bottom copper sheet, a dielectric layer and a top copper sheet arranged from bottom to top, wherein the bottom copper sheet is implemented by a complete copper sheet and serves as a reference ground; a wiring area and a grounding area composed of copper sheets located outside the wiring area are provided on the top copper sheet, and an input feeder, an output feeder and a plurality of resonators implemented by microstrip lines are provided in the wiring areas on both sides of the wiring area;

[0008] The resonators are arranged in parallel in sequence, the input feeder is connected to the first resonator, the output feeder is connected to the last resonator, one end of each resonator is directly connected to the grounding area on one side of the wiring area, and the other end is connected to the grounding area on the other side by setting a patch capacitor;

[0009] A plurality of grounding metal vias are provided at the connection between the grounding area and the chip capacitor, and the grounding metal vias are electrically connected to the bottom copper sheet and the top copper sheet.

[0010] Preferably, the grounding area includes a first grounding area and a second grounding area respectively located at the upper side and the lower side of the wiring area, and the wiring area is provided with five resonators arranged in parallel in sequence, namely, a first resonator, a second resonator, a third resonator, a fourth resonator and a second resonator;

[0011] The input feeder is connected to the first resonator, the output feeder is connected to the fifth resonator, one end of the first resonator, the third resonator and the fifth resonator are directly connected to the first grounding area, and the other end is connected to the second grounding area by setting a patch capacitor, and one end of the second resonator and the fourth resonator are directly connected to the second grounding area, and the other end is connected to the first grounding area by setting a patch capacitor.

[0012] Preferably, the input feed line and the output feed line are both 50 ohm microstrip lines with a width of 1 mm; the input feed line and the output feed line are vertically connected to the microstrip line body of the corresponding resonator and are 8.5 mm away from the grounding point below the connected microstrip line body.

[0013] Preferably, each chip capacitor uses a 0402 package ceramic capacitor with the same capacitance value, with a capacitance value of 24pF and a capacitance accuracy of ±1%;

[0014] Each resonator 3 is implemented by a microstrip line with a width of 0.7 mm, and the center distance between two adjacent resonators is 1.5 mm.

[0015] Preferably, on the top copper sheet, the gap between the copper sheets of the first grounding area and the second grounding area and the microstrip line bodies of the input feeder and the output feeder is 0.5 mm, and the distance between each resonator is 2 mm.

[0016] Preferably, the bottom copper layer, the dielectric layer and the top copper layer are made of FR4 board material.

[0017] Beneficial effects: Due to the adoption of the above technical solution, the utility model has the following beneficial effects:

[0018] The filter designed by the utility model is realized by using 5 0402 package ceramic capacitors with the same capacitance value and ordinary FR4 board material. The overall size of the filter is small, making it possible to realize a UHF band bandpass filter on a miniaturized PCB. It can be assembled by ordinary SMT process, has good performance consistency, and does not require debugging of the filter. The production efficiency is high and it has an incomparable extremely low cost. At the same time, the filter has excellent insertion loss, and the typical value is less than 2.4dB. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the UHF band ultra-small bandpass filter proposed by the utility model;

[0020] Figure 2 It is a schematic diagram of the simulation results of the UHF band ultra-small bandpass filter designed in Example 1;

[0021] Among them, 1-input feed line, 2-chip capacitor, 3-resonator, 4-ground metal via, 5-bottom copper sheet, 6-top copper sheet, 7-output feed line. DETAILED DESCRIPTION

[0022] The embodiments of the present utility model are described in detail below in conjunction with the accompanying drawings.

[0023] Embodiment 1

[0024] The utility model proposes a UHF band ultra-small bandpass filter, which realizes the UHF band ultra-small bandpass filter on an ordinary FR4 plate by adopting a microstrip (PCB copper sheet) and a 0402 packaged ceramic capacitor, and achieves excellent insertion loss, out-of-band suppression and return loss indicators by adjusting the length of the microstrip resonator, the position of the 50-ohm microstrip line relative to the microstrip resonator, the distance between the microstrip resonators and the capacitance value.

[0025] The UHF band ultra-small bandpass filter proposed by the utility model includes a bottom copper sheet, a dielectric layer and a top copper sheet arranged from bottom to top, the bottom copper sheet is implemented by a complete copper sheet as a reference ground; a wiring area and a grounding area composed of copper sheets located outside the wiring area are provided on the top copper sheet, and input feeders, output feeders and multiple resonators implemented by microstrip lines are provided in the wiring areas on both sides of the wiring area. Among them, each resonator is arranged in parallel in sequence, the input feeder is connected to the first resonator, the output feeder is connected to the last resonator, one end of each resonator is directly connected to the grounding area on one side of the wiring area, and the other end is connected to the grounding area on the other side by setting a patch capacitor.

[0026] Example 1: Figure 1As shown, the UHF band ultra-small bandpass filter designed in this example includes: an input feeder 1 and an output feeder 7 implemented by a 50-ohm microstrip line, five chip capacitors 2, five resonators 3, a plurality of grounded metal vias 4, a bottom copper sheet 5 and a top copper sheet 6, wherein the input feeder 1 is connected to the first resonator, the output feeder 7 is connected to the last resonator, the five chip capacitors 2 use five 0402 packaged ceramic capacitors with the same capacitance value, which are welded between the five resonators and the top grounded copper sheet; the five microstrip resonators 3 have different lengths; a plurality of grounded metal vias 4 connect the top copper sheet 6 and the bottom copper sheet 5; the bottom copper sheet 5 is the reference ground of the microstrip circuit.

[0027] Its specific parameters are as follows:

[0028] An ordinary FR4 circuit board with a thickness of 0.6mm is used. The input feed line 1 and the output feed line 7 both use 50 ohm microstrip lines with a width of 1mm and a distance of 8.5mm from the grounding point below the connected resonator; the capacitors connected to each resonator are 5 0402 packaged ceramic capacitors with the same capacitance value, and muRata's GJM series high-Q capacitors are used, with a capacitance of 24pF and a capacitance accuracy of ±1%; resonator 3 uses a microstrip line resonator, and the width of the 5 microstrip resonators is uniformly 0.7mm, the length is about 10mm, and the center distance of the coupler is about 1.5mm; the grounding metal via 4 needs to be placed close to the 0402 package ceramic capacitor; the bottom copper sheet 5 needs to be set as a complete copper sheet; the top copper sheet 6 has a gap of 0.5mm with the microstrip lines of the input feed line 1 and the output feed line 7, and a distance of 2mm from the resonator.

[0029] In this example, the above design can realize an excellent UHF band ultra-small bandpass filter with a center frequency of 500MHz and a relative bandwidth of about 15%. Figure 2 From the simulation results shown, it can be seen that the insertion loss S21 of the filter is about -2dB, which is smaller than the loss directly realized on the FR4 board (the loss on the FR4 board is about -5dB); the input return loss S11 and the output return loss S22 can be guaranteed to be below -10dB without debugging, and the production efficiency is high. Moreover, the size of the filter can be reduced to 1cm*1cm, which can be reduced by 90% compared with the conventional UHF band microstrip filter, so it has huge advantages in performance, size, cost and manufacturability.

[0030] In the UHF band ultra-small bandpass filter designed by the utility model, the number of resonators is not limited to 5, but is determined by the technical indicators of the filter. The higher the technical indicator requirements, the greater the number of resonators.

[0031] The above shows and describes the basic principle, main features and advantages of the utility model. Those skilled in the art should understand that the above embodiments do not limit the utility model in any form, and any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the utility model.

Claims

1. A UHF band ultra-small bandpass filter, characterized in that: The invention comprises a bottom copper sheet (5), a dielectric layer and a top copper sheet (6) arranged from bottom to top, wherein the bottom copper sheet (5) is implemented by a complete copper sheet and serves as a reference ground; a wiring area and a grounding area composed of copper sheets and located outside the wiring area are provided on the top copper sheet (6); an input feed line (1) implemented by a microstrip line, an output feed line (7) and a plurality of resonators (3) are provided in the wiring areas on both sides of the wiring area; The resonators (3) are arranged in parallel in sequence, the input feeder (1) is connected to the first resonator, the output feeder (7) is connected to the last resonator, one end of each resonator is directly connected to the grounding area on one side of the wiring area, and the other end is connected to the grounding area on the other side by setting a patch capacitor (2); A plurality of grounding metal vias (4) are provided at the connection between the grounding area and the patch capacitor (2), and the grounding metal vias (4) are electrically connected to the bottom copper sheet (5) and the top copper sheet (6).

2. The UHF band ultra-small bandpass filter according to claim 1, characterized in that: The grounding area comprises a first grounding area and a second grounding area respectively located at the upper side and the lower side of the wiring area, and the wiring area is provided with five resonators (3) arranged in parallel in sequence, namely a first resonator, a second resonator, a third resonator, a fourth resonator and a second resonator; The input feeder (1) is connected to the first resonator, the output feeder (7) is connected to the fifth resonator, one end of the first resonator, the third resonator and the fifth resonator are directly connected to the first grounding area, and the other end is connected to the second grounding area by setting the patch capacitor (2), and one end of the second resonator and the fourth resonator are directly connected to the second grounding area, and the other end is connected to the first grounding area by setting the patch capacitor (2).

3. The UHF band ultra-small bandpass filter according to claim 2, characterized in that: The input feeder (1) and the output feeder (7) are both 50 ohm microstrip lines with a width of 1 mm; the input feeder (1) and the output feeder (7) are vertically connected to the microstrip line body of the corresponding resonator and are 8.5 mm away from the grounding point below the connected microstrip line body.

4. The UHF band ultra-small bandpass filter according to claim 3, characterized in that: Each chip capacitor (2) uses a 0402 package ceramic capacitor with the same capacitance value, the capacitance value is 24pF, and the capacitance accuracy is ±1%; Each resonator (3) is realized by using a microstrip line with a width of 0.7 mm and a length of 10 mm, and the center distance between two adjacent resonators is 1.5 mm.

5. The UHF band ultra-small bandpass filter according to claim 4, characterized in that: On the top copper sheet (6), the gap between the copper sheets of the first grounding area and the second grounding area and the microstrip line bodies of the input feeder (1) and the output feeder (7) is 0.5 mm, and the distance between each resonator is 2 mm.

6. The UHF band ultra-small bandpass filter according to claim 1, characterized in that: The bottom copper sheet (5), dielectric layer and top copper sheet (6) are made of FR4 board material.

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