Harmonic suppression filter

Abstract

The utility model discloses a harmonic suppression filter, which comprises a dielectric substrate, a metal microstrip layer and a metal grounding plate are respectively arranged on the front surface and the back surface of the dielectric substrate, the metal microstrip layer comprises feed tap microstrip lines, open-circuit microstrip lines and a central microstrip line, the feed tap microstrip lines are arranged at the left end and the right end of the central microstrip line, and the open-circuit microstrip lines are arranged at the left end and the right end of the central microstrip line. The open-circuit microstrip lines are arranged on the upper side and the lower side of the center microstrip line and connected with the center microstrip line through the feed tap microstrip lines, and through the arrangement, due to the fact that the antenna is achieved through the microstrip lines, the antenna has the advantages of being simple in circuit structure, small in size, low in cost, easy to manufacture and integrate and the like.

Description

Technical Field

[0001] The utility model relates to the technical field of microwave communications, in particular to a harmonic suppression filter. Background Art

[0002] In recent years, with the rapid development of wireless communication technologies such as radar technology and mobile communication technology, spectrum resources have become increasingly tight and scarce. Therefore, the requirements of wireless communication technology standards for transmitter modules have become increasingly stringent. In general, signal transmitter modules mostly use oscillator circuits to generate low-frequency, stable baseband signals, which are then up-converted by mixers, amplified by power amplifiers, and finally sent out by antennas. Due to the influence of nonlinear devices such as mixers and power amplifiers, the transmitting circuit often generates large second harmonics, which pollute the surrounding electromagnetic environment, interfere with the operation of other radio equipment, do not meet wireless communication technology standards, and also affect the transmission of their own transmission signals. How to effectively suppress the harmonic components of the transmitting module and reduce the pollution to the electromagnetic environment is one of the problems that must be solved in the current wireless communication field. Utility Model Content

[0003] The utility model aims to solve the technical problems existing in the background technology and proposes a harmonic suppression filter, comprising a dielectric substrate, wherein a metal microstrip layer and a metal ground plate are respectively arranged on the top end surface and the bottom end surface of the dielectric substrate, the metal microstrip layer comprises a feed tap microstrip line, an open microstrip line and a center microstrip line connected to each other, the feed tap microstrip line is arranged at the left and right ends of the center microstrip line, the open microstrip line is arranged on the upper and lower sides of the center microstrip line, and is connected to the center microstrip line through the feed tap microstrip line.

[0004] Furthermore, the feed tap microstrip line includes an input tap and an output tap, the open microstrip line includes an upper open line and a lower open line, the input tap is connected to one end of the upper open line and the center microstrip line respectively, and the output tap is connected to the other end of the lower open line and the center microstrip line respectively.

[0005] Furthermore, the input tap is provided with a first connection unit and a second connection unit at one end, the first connection unit and the second connection unit are arranged at an angle to each other, the first connection unit is used to connect to the upper open line, and the second connection unit is used to connect to the central microstrip line.

[0006] Furthermore, the output tap is provided with a third connection unit and a fourth connection unit at one end, the third connection unit and the fourth connection unit are arranged at an angle to each other, the third connection unit is used to connect to the central microstrip line, and the fourth connection unit is used to connect to the lower open line.

[0007] Furthermore, the upper open line and the lower open line are arranged parallel to the central microstrip line to form two coupling branches.

[0008] Furthermore, both the upper open route and the lower open route are 1 / 8 wavelength microstrip lines with consistent thickness.

[0009] Further, the metal microstrip layer is centrally symmetric about the central microstrip line.

[0010] Furthermore, the dielectric constant of the dielectric substrate is 4.6, the thickness is 0.2 mm, and the loss tangent is 0.015.

[0011] Further, as an implementation method, the thickness of the metal microstrip layer is 0.035 mm.

[0012] Further, as an implementation mode, the thickness of the feed tap microstrip line is 0.36 mm, the thickness of the open microstrip line is 0.2 mm, the length of the open microstrip line is 3.5 mm, and the spacing between the open microstrip line and the center microstrip line is 0.2 mm.

[0013] Compared with the prior art, the utility model has the following beneficial technical effects: First, the utility model is implemented by a microstrip line, and has the characteristics of simple circuit structure, small size, low cost, easy manufacturing and integration. Second, the utility model adopts a 1 / 8 wavelength open microstrip line to achieve effective suppression of the second harmonic component. At the same time, the open microstrip line and the center microstrip line form two coupling branches, introducing two transmission zeros in the stop band, greatly widening the width of the stop band and increasing the stop band attenuation. Third, the open microstrip line and the center microstrip line used in the utility model are parallel to each other, making the filter structure compact and further reducing the area. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a cross-sectional view of the utility model;

[0015] Figure 2 A schematic diagram of the structure of a metal microstrip layer;

[0016] Figure 3 A schematic diagram showing the structural dimensions of the metal microstrip layer;

[0017] Figure 4 A simulation result diagram after the utility model establishes a graphical model in the ADS software;

[0018] Figure 5 This is another simulation result diagram after the utility model establishes a graphical model in the ADS software. DETAILED DESCRIPTION

[0019] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0020] In the description of the present utility model, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present utility model. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more features. In the description of the present utility model, unless otherwise specified, "multiple" means two or more.

[0021] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or a specific connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

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

[0023] like Figure 1-Figure 4 As shown, the utility model proposes a harmonic suppression filter, based on an FR4 plate, comprising a dielectric substrate 2, wherein a metal microstrip layer 3 and a metal ground plate 1 are respectively arranged on the top end surface and the bottom end surface of the dielectric substrate 2, and the metal microstrip layer 3 comprises a feed tap microstrip line 31, an open microstrip line 32 and a center microstrip line 33 connected to each other. Specifically, the feed tap microstrip line 31 is arranged at the left and right ends of the center microstrip line 33, and the open microstrip line 32 is arranged at the upper and lower sides of the center microstrip line 33, and is connected to the center microstrip line 33 through the feed tap microstrip line 31, so that the metal microstrip layer 3 is symmetrical about the center of the center microstrip line 33.

[0024] Specifically, in some embodiments, the feed tap microstrip line 31 includes an input tap 311 and an output tap 312, the open microstrip line 32 includes an upper open line 321 and a lower open line 322, the input tap 311 is connected to the upper open line 321 and one end of the center microstrip line 33, respectively, the output tap 312 is connected to the lower open line 322 and the other end of the center microstrip line 33, the input tap 311 and the output tap 312 are used for signal input and output, and at the same time achieve 50 ohm impedance matching, the upper open line 321 and the lower open line 322 are arranged parallel to the center microstrip line 33 to form two coupling branches.

[0025] In some embodiments, the upper open line 321 and the lower open line 322 are both 1 / 8 wavelength microstrip lines of uniform thickness. For fundamental wave signals, the 1 / 8 wavelength upper open line 321 and the 1 / 8 wavelength lower open line 322 can be equivalent to capacitors, and the center microstrip line 33 can be equivalent to inductors. The three constitute a low-pass filter. The fundamental wave signal is within its passband and can pass through the filter smoothly.

[0026] It should be noted that the wavelength in the 1 / 8 wavelength involved in the above embodiment is the wavelength corresponding to the fundamental wave signal in the plate, which is only used as a standard for measurement. Different plates at the same frequency correspond to different wavelengths.

[0027] In some embodiments, for the second harmonic component, the 1 / 8 wavelength upper open line 321 and the 1 / 8 wavelength lower open line 322 can be correspondingly set to the 1 / 4 wavelength upper open line 321 and the 1 / 4 wavelength lower open line 322, which are equivalent to two series resonators. Harmonics will produce strong reflections on the two microstrip lines and are difficult to pass through the filter. Since the upper open line 321, the lower open line 322, and the center microstrip line 33 are parallel to each other and the spacing is small, the electromagnetic fields of the three microstrip lines will be coupled with each other. According to the coupling filter theory, a transmission zero point can be generated for each additional coupling branch. The center microstrip line 33 forms two coupling branches with the upper open line 321 and the lower open line 322, respectively, and the filter generates two transmission zero points in the stop band. The addition of two coupling branches makes the transfer function of the filter approximate to an elliptic function, and the filter is transformed into an elliptic function filter. At the same time, the transmission zero introduced by the coupling branch not only expands the width of the stopband, but also further increases the attenuation of the stopband, so that the filter has a steeper transition band and greater stopband attenuation, thereby achieving good suppression of harmonic components.

[0028] Further, in some embodiments, as a specific connection method between the feeding tap microstrip line 31, the open microstrip line 32 and the center microstrip line 33, the input tap 311 is provided with a first connection unit 3111 and a second connection unit 3112 at one end, the first connection unit 3111 and the second connection unit 3112 are arranged at an angle to each other, the first connection unit 3111 is used to connect to the upper open line 321, and the second connection unit 3112 is used to connect to the center microstrip line 33, and the output tap 312 is provided with a third connection unit 3121 and a fourth connection unit 3122 at one end, the third connection unit 3121 and the fourth connection unit 3122 are arranged at an angle to each other, the third connection unit 3121 is used to connect to the center microstrip line 33, and the fourth connection unit 3122 is used to connect to the lower open line 322.

[0029] Furthermore, in some embodiments, the dielectric constant of the dielectric substrate 2 is 4.6, the thickness is 0.2 mm, and the loss tangent is 0.015.

[0030] Furthermore, in some embodiments, the thickness of the metal microstrip layer 3 is 0.035 mm.

[0031] Further, in some embodiments, the thickness of the feed tap microstrip line 31 is 0.36 mm, the thickness of the open microstrip line 32 is 0.2 mm, the length of the open microstrip line 32 is 3.5 mm, and the distance between the open microstrip line 32 and the center microstrip line 33 is 0.2 mm.

[0032] Furthermore, in order to verify the performance of the filter manufactured by the utility model, a Figure 2 The harmonic suppression filter microstrip line model takes the fundamental frequency as 5.8GHz. The filter size parameters are simulated and optimized, combined with Figure 3 The parameters marked in , the final filter size parameters are shown in Table 1.

[0033] Table 1 Filter size parameters

[0034] L S W1 W2 3.5mm 0.2mm 0.2mm 0.36mm

[0035] Figure 4 , Figure 5The S parameter simulation results. In the low passband, the -3dB passband width is 0-8.645GHz, of which the insertion loss at the 5.8GHz fundamental frequency is -0.143dB, indicating that the harmonic suppression filter has little effect on the fundamental signal. In the stopband, there is a large stopband attenuation in the frequency range of 10.39-13.27GHz, all reaching 20dB. Among them, the insertion loss at the second harmonic frequency of 11.6GHz reaches -22.988dB, indicating that the filter has a good suppression effect on the second harmonic component. The two transmission zeros introduced by the coupling branch are located at 10.88GHz and 12.78GHz, and the insertion losses are -40.739dB and -37.184dB respectively.

[0036] In summary, the utility model has the following beneficial effects: First, the utility model is implemented by a microstrip line, and has the characteristics of simple circuit structure, small size, low cost, easy manufacturing and integration. Second, the utility model adopts a 1 / 8 wavelength open microstrip line to achieve effective suppression of the second harmonic component. At the same time, the open microstrip line and the center microstrip line form two coupling branches, and two transmission zeros are introduced in the stop band, which greatly widens the width of the stop band and increases the stop band attenuation. Third, the open microstrip line and the center microstrip line used in the utility model are parallel to each other, which makes the filter structure compact and further reduces the area.

[0037] The above are one or more implementation methods provided in combination with specific content, and it is not intended that the specific implementation of the utility model is limited to these descriptions. Any method, structure, etc. similar to or identical to the method, structure, etc. of the utility model, or any technical deduction or replacement based on the concept of the utility model, shall be deemed to be within the protection scope of the utility model.

Claims

1. A harmonic suppression filter, characterized in that: The invention comprises a dielectric substrate (2), wherein a metal microstrip layer (3) and a metal grounding plate (1) are respectively arranged on the top end surface and the bottom end surface of the dielectric substrate (2), wherein the metal microstrip layer (3) comprises a feed tap microstrip line (31), an open microstrip line (32) and a center microstrip line (33), wherein the feed tap microstrip line (31) is arranged at the left and right ends of the center microstrip line (33), and the open microstrip line (32) is arranged at the upper and lower sides of the center microstrip line (33), and is connected to the center microstrip line (33) through the feed tap microstrip line (31).

2. A harmonic suppression filter according to claim 1, characterized in that: The feed tap microstrip line (31) comprises an input tap (311) and an output tap (312); the open microstrip line (32) comprises an upper open line (321) and a lower open line (322); the input tap (311) is connected to one end of the upper open line (321) and the central microstrip line (33) respectively; the output tap (312) is connected to the other end of the lower open line (322) and the central microstrip line (33) respectively.

3. A harmonic suppression filter according to claim 2, characterized in that: The input tap (311) comprises a first connection unit (3111) and a second connection unit (3112), wherein the first connection unit (3111) and the second connection unit (3112) are arranged at an angle to each other, the first connection unit (3111) is used to connect to the upper open line (321), and the second connection unit (3112) is used to connect to the central microstrip line (33).

4. A harmonic suppression filter according to claim 3, characterized in that: The output tap (312) comprises a third connection unit (3121) and a fourth connection unit (3122), wherein the third connection unit (3121) and the fourth connection unit (3122) are arranged at an angle to each other, the third connection unit (3121) is used to connect to the central microstrip line (33), and the fourth connection unit (3122) is used to connect to the lower open line (322).

5. The harmonic suppression filter according to claim 2, characterized in that: The upper open line (321) and the lower open line (322) are arranged parallel to the central microstrip line (33) to form two coupling branches.

6. A harmonic suppression filter according to claim 2, characterized in that: The upper open line (321) and the lower open line (322) are both 1 / 8 wavelength microstrip lines with consistent thickness.

7. The harmonic suppression filter according to claim 1, characterized in that: The metal microstrip layer (3) is centrally symmetrical about the central microstrip line (33).

8. The harmonic suppression filter according to claim 1, characterized in that: The dielectric constant of the dielectric substrate (2) is 4.6, the thickness is 0.2 mm, and the loss tangent is 0.

015.

9. The harmonic suppression filter according to claim 1, characterized in that: The thickness of the metal microstrip layer (3) is 0.035 mm.

10. The harmonic suppression filter according to claim 1, characterized in that: The thickness of the feed tap microstrip line (31) is 0.36 mm, the thickness of the open microstrip line (32) is 0.2 mm, the length of the open microstrip line (32) is 3.5 mm, and the distance between the open microstrip line (32) and the central microstrip line (33) is 0.2 mm.

Images