阅读说明：本技术 微带低通滤波器 (Microstrip low-pass filter ) 是由 陈荣斌 于 2020-12-31 设计创作，主要内容包括：本发明公开了一种微带低通滤波器,包括介质基板；微带传输线,微带传输线设于介质基板的第一面上；多个谐振单元,谐振单元蚀刻在介质基板的第二面上,第二面与第一面为对立面,多个谐振单元呈对数周期阵列排列在介质基板上,呈锯齿形的相邻两个谐振单元的顶点处形成一个夹角。本发明采用了对数周期锯齿形的缺陷地结构,并作为谐振单元设置在介质基板上形成微带低通滤波器,通过设置锯齿形的呈对数周期阵列排列的谐振单元,使得滤波器在通带内的插入损耗低,通带外具有超宽带抑制性以及从通带到阻带的急剧转换特性,具有高性能、宽阻带、良好的回波损耗和低插入损耗等特点。(The invention discloses a microstrip low-pass filter, which comprises a dielectric substrate; the microstrip transmission line is arranged on the first surface of the dielectric substrate; the resonant units are etched on the second surface of the dielectric substrate, the second surface and the first surface are opposite surfaces, the resonant units are arrayed on the dielectric substrate in a log periodic mode, and an included angle is formed at the top point of two adjacent zigzag resonant units. The invention adopts a log periodic sawtooth-shaped defected ground structure, is used as a resonance unit and arranged on a medium substrate to form a microstrip low-pass filter, and the sawtooth-shaped resonance units arranged in a log periodic array are arranged, so that the filter has low insertion loss in a pass band, has ultra-wideband inhibition outside the pass band and sharp conversion characteristic from the pass band to a stop band, and has the characteristics of high performance, wide stop band, good return loss, low insertion loss and the like.)

1. A microstrip low-pass filter comprising:

a dielectric substrate;

the microstrip transmission line is arranged on the first surface of the dielectric substrate;

the resonant units are etched on the second surface of the dielectric substrate, the second surface and the first surface are opposite surfaces, the resonant units are arrayed on the dielectric substrate in a log periodic manner, and an included angle is formed at the top points of two adjacent zigzag resonant units.

2. The microstrip low pass filter according to claim 1, wherein the microstrip transmission line is located in the middle of the resonant units, and the resonant units are periodically distributed on the microstrip transmission line.

3. The microstrip low-pass filter according to claim 2, wherein the resonant units include a first resonant unit, a second resonant unit and a third resonant unit that are consecutive, a distance between an included angle of two adjacent resonant units and the microstrip transmission line is a height, a distance between a first included angle formed by the first resonant unit and the second resonant unit and the microstrip transmission line is a first height, a distance between a second included angle formed by the second resonant unit and the third resonant unit and the microstrip transmission line is a second height, a ratio of the first height to the second height is a first scale factor value, and the heights of two adjacent resonant units increase in proportion according to the first scale factor value.

4. The microstrip low pass filter according to claim 3, wherein two vertices of the resonant cells are spaced apart, two vertices of the first resonant cell are spaced apart by a first distance, two vertices of the second resonant cell are spaced apart by a second distance, a ratio between the first distance and the second distance is a second scale factor value, and the distances between two adjacent resonant cells are increased in proportion to the second scale factor value.

5. The microstrip low pass filter according to claim 4, wherein the first scale factor value is equal to the second scale factor value.

6. The microstrip low pass filter according to claim 5, wherein the first scale factor value and the second scale factor value take on a value between 0.7 and 0.9.

7. The microstrip low pass filter according to claim 4, wherein the input impedance of the microstrip transmission line has a value between 30 and 70 ohms.

8. The microstrip low pass filter according to claim 1, wherein a gap is provided at a corner of two adjacent resonance units.

9. The microstrip low pass filter according to claim 1, wherein SMA joints are respectively provided at both ends of the dielectric substrate.

10. The microstrip low pass filter according to claim 1, wherein the dielectric substrate has a dielectric constant between 9 and 10, a loss tangent between 0.002 and 0.004, and a thickness between 0.7 and 0.9 mm.

Technical Field

The invention relates to the technical field of microwave communication, in particular to a microstrip low-pass filter.

Background

Microwave devices and other related components are indispensable both currently and in the future today with ever increasing connectivity in wireless communications and the internet of things. Since such filters are able to suppress wideband noise and spurious signals. The microstrip filter is easy to manufacture and low in cost, so that the cost is reduced while the system performance is improved. Many microstrip-based filters have been developed so far, but importantly, the performance of such filters needs to be further improved to meet all relevant applications. Therefore, performance improvements of filters are continuously required. Low pass filters are important components of today's wireless communication systems that are widely used for noise and intermodulation signal rejection, and in general, low pass band filters with ultra wide band rejection and fast roll-off, as well as low insertion loss in the pass band, are highly desirable in many practical applications. The microstrip low-pass filter in the related art has poor performance due to insufficient wide stopband, poor return loss and high insertion loss.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides a microstrip low-pass filter which has the characteristics of high performance, wide stop band, good return loss, low insertion loss and the like.

The microstrip low-pass filter according to an embodiment of the first aspect of the present invention is characterized by comprising: a dielectric substrate; the microstrip transmission line is arranged on the first surface of the dielectric substrate; the resonant units are etched on the second surface of the dielectric substrate, the second surface and the first surface are opposite surfaces, the resonant units are arrayed on the dielectric substrate in a log periodic manner, and an included angle is formed at the top points of two adjacent zigzag resonant units.

The microstrip low-pass filter according to the embodiment of the invention has at least the following beneficial effects: the embodiment of the invention adopts a log-periodic sawtooth-shaped defect ground structure, and is used as a resonance unit arranged on a medium substrate to form a microstrip low-pass filter, the filter has low insertion loss in a pass band, and has ultra-wideband inhibition and sharp transition characteristic from the pass band to a stop band outside the pass band, and the filter has the characteristics of high performance, wide stop band, good return loss, low insertion loss and the like.

According to some embodiments of the invention, the microstrip transmission line is located in the middle of the resonance unit, and the resonance unit is periodically distributed on the microstrip transmission line.

According to some embodiments of the present invention, the resonant units include a first resonant unit, a second resonant unit, and a third resonant unit that are consecutive, a distance between an included angle of two adjacent resonant units and the microstrip transmission line is a height, a distance between a first included angle formed by the first resonant unit and the second resonant unit and the microstrip transmission line is a first height, a distance between a second included angle formed by the second resonant unit and the third resonant unit and the microstrip transmission line is a second height, a ratio of the first height to the second height is a first scale factor value, and the heights of two adjacent resonant units increase in proportion according to the first scale factor value.

According to some embodiments of the invention, a distance is provided between two vertexes of the resonant units, a first distance is provided between two vertexes of the first resonant unit, a second distance is provided between two vertexes of the second resonant unit, a ratio between the first distance and the second distance is a second scale factor value, and the distances between two adjacent resonant units are increased in proportion according to the second scale factor value.

According to some embodiments of the invention, the first scale factor value is equal to the second scale factor value.

According to some embodiments of the invention, the first scale factor value and the second scale factor value range between 0.7 and 0.9.

According to some embodiments of the invention, the input impedance of the microstrip transmission line has a value between 30 and 70 ohms.

According to some embodiments of the invention, there is a gap at a corner of two adjacent resonator elements.

According to some embodiments of the invention, SMA joints are respectively provided at both ends of the dielectric substrate.

According to some embodiments of the invention, the dielectric constant of the dielectric substrate is between 9 and 10, the loss tangent value is between 0.002 and 0.004, and the thickness is between 0.7 and 0.9 mm.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The invention is further described with reference to the following figures and examples, in which:

FIG. 1 is a schematic diagram of a microstrip low pass filter according to some embodiments of the present invention;

FIG. 2 is a schematic diagram of a microstrip low pass filter according to another embodiment of the present invention;

FIG. 3 is a schematic diagram of a resonant cell layout according to another embodiment of the present invention;

FIG. 4 is a schematic diagram illustrating an in-band response test of a microstrip low-pass filter according to another embodiment of the present invention;

fig. 5 is a schematic diagram of a test of a broadband rejection response of a microstrip low-pass filter according to another embodiment of the present invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.

In the description of the present invention, it should be understood that the orientation or positional relationship referred to in the description of the orientation, such as the upper, lower, front, rear, left, right, etc., is based on the orientation or positional relationship shown in the drawings, and is only for convenience of description and simplification of description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.

In the description of the present invention, the meaning of a plurality is one or more, the meaning of a plurality is two or more, and the above, below, exceeding, etc. are understood as excluding the present numbers, and the above, below, within, etc. are understood as including the present numbers. If the first and second are described for the purpose of distinguishing technical features, they are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.

In the description of the present invention, unless otherwise explicitly limited, terms such as arrangement, installation, connection and the like should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above terms in the present invention in combination with the specific contents of the technical solutions.

In the description of the present invention, reference to the description of the terms "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Referring to fig. 1 to 3, an embodiment of the present invention provides a microstrip low-pass filter, including a dielectric substrate 110, a microstrip transmission line 120, and a resonant unit 130, where the microstrip transmission line 120 is disposed on a first surface of the dielectric substrate 110, the resonant unit 130 is etched on a second surface of the dielectric substrate 110 to form a slot, the second surface of the dielectric substrate 110 is a ground plane, the first surface and the second surface are opposite surfaces, a plurality of resonant units 130 are arranged on the dielectric substrate 110 in a log-periodic array, and an included angle is formed at a vertex of two adjacent resonant units 130 in a zigzag shape, so as to form a slot array with a certain periodicity. The embodiment of the invention adopts a log-periodic sawtooth-shaped defected ground structure, and the defected ground structure is used as a resonance unit 130 and arranged on a dielectric substrate 110 to form a microstrip low-pass filter, and the sawtooth-shaped resonance unit 130 arranged in a log-periodic array is arranged, so that the filter has low insertion loss in a pass band, has ultra-wideband inhibition outside the pass band and sharp transition characteristics from the pass band to a stop band, and has the characteristics of high performance, wide stop band, good return loss, low insertion loss and the like.

Referring to fig. 3, in some embodiments of the present invention, the microstrip transmission line 120 is located in the middle of the resonant unit 130, the resonant units 130 are periodically distributed on the microstrip transmission line 120, and a plurality of resonant units are periodically distributed around two ends of the microstrip transmission line 120.

Referring to fig. 3, in some embodiments of the present invention, the resonant unit 130 includes a first resonant unit 131, a second resonant unit 132, and a third resonant unit 133, the first resonant unit 131, the second resonant unit 132, and the third resonant unit 133 are three adjacent resonant units 130, the three resonant units 130 sequentially increase according to the length of the formed slot, the first resonant unit 131, the second resonant unit 132, and the third resonant unit 133 may be any three adjacent resonant units 130, the distance from the included angle between the adjacent resonant units 130 to the microstrip transmission line 120 is a height, the distance from the first included angle 134 formed by the first resonant unit 131 and the second resonant unit 132 to the microstrip transmission line 120 is a first height, the distance from the second included angle 135 formed by the second resonant unit 132 and the third resonant unit 133 to the microstrip transmission line 120 is a second height, and the ratio of the first height to the second height is a first scale factor value, the first scale factor value is a preset value, in an embodiment, the first height divided by the second height is equal to the first scale factor, and the value of the first scale factor is taken as the first scale factor value, so that the ratio of the first height to the second height is the first scale factor value, in an embodiment, the first scale factor value is less than 1, so that the groove heights of the first resonant unit 131, the second resonant unit 132, and the third resonant unit 133 are increased in proportion, in an embodiment, the first resonant unit 131, the second resonant unit 132, and the third resonant unit 133 are respectively arranged on the dielectric substrate 110 from left to right, and on the premise that the requirements of the embodiment of the present invention are met, the first resonant unit 131, the second resonant unit 132, and the third resonant unit 133 may also be arranged on the dielectric substrate 110 from other directions, which is not limited in the present invention.

Referring to fig. 3, in some embodiments of the present invention, a plurality of resonant units 130 form a slot array, each slot is elongated and has two vertices, two adjacent slots are connected together by one vertex, a distance is formed between the two vertices of the resonant units 130, a first distance is formed between the two vertices of a first resonant unit 131, a second distance is formed between the two vertices of a second resonant unit 132, a ratio of the first distance to the second distance is a second scale factor value, and the second scale factor value is a predetermined value, in one embodiment, the first distance is divided by the second distance and is equal to the second scale factor, and the second scale factor value is the second scale factor value, so that the ratio of the first distance to the second distance is the second scale factor value, in one embodiment, the second scale factor value is less than 1, so that the first resonant unit 131, The slot widths of the second resonant cell 132 and the third resonant cell 133 are increased in proportion. It should be noted that in some embodiments of the invention, the height and spacing together determine the length of the slot.

In some embodiments of the invention, to simplify the design, the first scale factor value is equal to the second scale factor value such that an array of slots with a certain periodicity is formed.

In some embodiments of the present invention, the values of the first scale factor and the second scale factor are between 0.7 and 0.9, the first scale factor and the second scale factor are performed by a sweep parameter, the sweep parameter ranges from 0.7 to 0.9, the shortest slot has the highest suppression frequency, and can also be determined by the scale factor, the initial height, the initial periodicity, and a specific periodicity number, and based on these initial values, the microstrip low pass filter of the embodiments of the present invention can be developed only by using a full-wave electromagnetic simulator, and in one embodiment, the values of the first scale factor and the second scale factor are 0.8352, and at this time, the microstrip low pass filter of the embodiments of the present invention has the characteristics of the highest performance, wide stop band, good return loss, low insertion loss, and the like.

In some embodiments of the present invention, the input impedance of the microstrip transmission line 120 is between 30 and 70 ohms, in an embodiment, the input impedance of the microstrip transmission line 120 is 50 ohms, when the input impedance is about 70 ohms, the transmission loss is minimum, and when the input impedance is about 30 ohms, the power consumption is maximum, and the standard microstrip transmission line 120 with the input impedance of 50 ohms is selected, which can simultaneously take into account both the performance and the transmission loss and the power consumption, so that the microstrip low-pass filter in the embodiments of the present invention has the optimal performance.

In some embodiments of the present invention, there is a gap between two adjacent resonant cells 130 at the included angle, and referring to fig. 3, there is a gap between the first included angle 134 and the second included angle 135. in order to separate the slots between two adjacent vertices of the zigzag, in the embodiments of the present invention, a small gap is introduced at the top of each vertex, and in the limit, when the period of the resonant cells 130 approaches negative infinity, the slot array converges to the leftmost side of the dielectric substrate 110, and when the period of the resonant cells 130 approaches positive infinity, the slot array becomes an infinite array, and in one embodiment, the size of the gap is determined by the height and the spacing.

Referring to fig. 2, in some embodiments of the present invention, SMA joints 140 are respectively disposed at two ends of a dielectric substrate 110, a microstrip transmission line 120 is matched with a coaxial joint of the SMA joint 140, the SMA joint 140 is in a microwave region of a frequency range from dc to 26.5GHz, the SMA joint 140 is a widely applied small-sized screw-connected coaxial connector, and has the characteristics of excellent frequency bandwidth performance, long service life, and excellent frequency bandwidth performance and long service life by disposing the SMA joint 140, and is suitable for connecting the microstrip transmission line 120.

In some embodiments of the present invention, the dielectric constant of the dielectric substrate 110 is between 9 and 10, the loss tangent is between 0.002 and 0.004, and the thickness is between 0.7 and 0.9 mm, in one embodiment, the dielectric constant of the dielectric substrate 110 is 9.6, the loss tangent is 0.003, and the thickness is 0.8 mm, the size of the circuit design can be strictly controlled by selecting the dielectric substrate 110 with a high dielectric constant, the insertion loss in the whole pass band is low, two transmission zeros are generated in a high frequency band, good out-of-band characteristics are effectively ensured, the notch depth of the filter is sufficiently large, and the requirement of narrow-band notch is met, and meanwhile, the microstrip low-pass filter of the embodiments of the present invention has the advantages of small overall storage, adjustable notch, compact structure, convenient processing, and easy integration with other circuits.

It should be noted that, in some embodiments of the present invention, the microstrip low-pass filter of the embodiments of the present invention has a high broadband suppression effect by using the dielectric substrate 110 having a relative dielectric constant of 9.6, a tangent of 0.003, and a thickness of 0.8 mm, so that the microstrip low-pass filter has a cutoff frequency fc of 2GHz and a desired suppression band 24GHz, that is, 12fc, and the longest slot length is about 24 mm when the slot is used as a half-wavelength resonator at fc on the substrate.

It should be noted that, in some embodiments of the present invention, the initial slot is used as a half-wave resonator with a fundamental resonance frequency of 2GHz, the initial height is 16 mm, and the first scale factor value and the second scale factor value are 0.7 to 0.9, the initial spacing is set to 8 mm, and the sweep range is from 7 mm to 9 mm, based on these initial values, the microstrip low-pass filter in the embodiments of the present invention may be developed only with a full-wave electromagnetic simulator.

It should be noted that, in some embodiments of the present invention, through a comprehensive scan study and a full-wave electromagnetic optimization, the suppression level in the suppression band of the microstrip low-pass filter in the embodiments of the present invention is 20dB, and the in-band return loss is 10 dB. In one embodiment, a total of 10 slot line resonators (i.e., a cycle number of 10) are used. The longest slot has a height of 16 mm and a scale factor of 0.8352, so that the height of the first slot is 3.164 mm, the pitch of the first slot is 1.999 mm, the slot width is 1.213 mm, and the gap at the apex of the two slots is fixed at 0.45 mm, so that the area of the dielectric substrate 110 is 40.65 × 29.546 mm square.

Referring to fig. 4 and 5, it should be noted that in some embodiments of the present invention, the cutoff frequency of the microstrip low pass filter in the embodiments of the present invention is found to be about 1.96GHz through testing, and a simulated response is given for comparison, the simulated cutoff frequency is about 2.14GHz, and the in-band response is as shown in fig. 4, and the insertion loss is better than 1dB when the direct current reaches about 1.85GHz, and is less than 0.7dB when the direct current reaches 1.54GHz in particular. It should be noted that the losses include the conductor loss of the microstrip transmission line 120 and the conductor loss of the two SMA joints 140 at both ends, and the transition between the connection end and the microstrip transmission line 120. In general, the measured in-band group delay is 0.4ns, and simulation and measurement results show that the microstrip low-pass filter in the embodiment of the present invention has a sharp transition from the pass band to the stop band, and the broadband rejection response is shown with reference to fig. 5. The microstrip low-pass filter in the embodiment of the invention reaches the out-of-band inhibition level of 20dB from 2.6GHz to over 26.5GHz, so that the microstrip low-pass filter has the high inhibition characteristic of a broadband.

The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention. Furthermore, the embodiments of the present invention and the features of the embodiments may be combined with each other without conflict.