CN101692512A - Ultra wide band bandpass filter based on ground defective grounding structure - Google Patents

Abstract

The invention discloses an ultra-wideband bandpass filter based on a ground defect type grounding structure, which includes a circuit board on the front side of a double-sided copper-clad microstrip board and a grounding board on the back side, and the circuit board includes two parallel first The coupled microstrip line and the second coupled microstrip line, the first coupled microstrip line is connected to the input port through the input transmission line, and the second coupled microstrip line is connected to the output port through the output transmission line; the ground plate includes the first, The second and third inverted "S" type defect structures, wherein the first inverted "S" type defect structure is located in the center of the two parallel first and second coupled microstrip lines on the circuit board and directly below , the second inverted "S"-shaped subsidence structure and the third inverted "S"-type subsidence structure are symmetrically distributed on both sides of the first inverted "S"-type subsidence structure, and are respectively located at the output transmission line and the input end just below the center of the transmission line. It is a DGS ultra-wideband bandpass filter whose bandwidth can cover any ultra-wideband frequency band (within 3.1-10.6GHz).

Description

Ultra-Wideband Bandpass Filter Based on Ground Defect Grounding Structure

technical field

The invention relates to a filter in the microwave communication field, in particular to an ultra-wideband bandpass filter based on a ground defect type grounding structure.

Background technique

With the rapid development of communication technology, people have higher and higher requirements for information transmission system. In this context, ultra-wideband technology has become a research hotspot in the field of communication due to its advantages such as simple system, low cost, low power consumption, fast data transmission speed, and high security. Since the FCC (Federal Communications Commission of the United States) lifted the ban on the spectrum in the 3.1-10.6GHz band in 2002 and enabled it to be applied to ultra-wideband devices, there has been a wave of research on ultra-wideband technology in academia and industrial manufacturing. . The filter plays a very important role in the whole radio frequency UWB circuit system. Its characteristics play a very important role in the overall performance of the system.

Existing broadband bandpass filters mainly include parallel coupled line filters, interdigitated filters, comb line filters, and open or short-circuit stub filters, etc., but their bandwidth is limited. Not more than 50%. And the traditional design method is difficult to realize with any kind of dielectric material because the odd-even mode impedance ratio of the coupled line is too large.

Since the Defected Ground Structure (DGS) can cause special bandstop or bandpass characteristics of the frequency band, people have also begun to think about introducing it into the ultra-wideband design. The traditional ground defect structure is generally "dumbbell" or "rectangular". This structure is characterized by the ability to introduce transmission zeros, but its insertion loss is relatively large and its selectivity is poor. Moreover, the current ultra-wideband filter based on DGS is either complicated in design, or has a large loss, and the structure is not universal, so it is difficult to conveniently design an ultra-wideband filter in any frequency band.

After reviewing the existing literature by the applicant, it was found that the Chinese patent application "ultra-wideband microstrip filter" (application number: 200610117045.2) uses a combination of high-pass and low-pass filters to achieve the ultra-wideband characteristics of the filter. In this invention, 7 A dumbbell-shaped DGS structure and slot unit has a complex structure and many debugging parameters, making it difficult to design; in addition, the "dumbbell" type DGS has a relatively large insertion loss and poor selectivity, so the maximum in-band filter of this type of filter is The insertion loss reaches -1.5dB, and the out-of-band suppression can only reach below -20dB.

Contents of the invention

For the defects or deficiencies in the above-mentioned prior art, the purpose of the present invention is to provide a kind of ultra-wideband bandpass filter based on the ground defect type grounding structure, its structure is simple, and the bandwidth can cover any ultra-wideband frequency band (3.1-10.6GHz section), and can effectively suppress out-of-band signals, so that the attenuation can reach more than 35dB.

In order to realize above-mentioned task, the present invention takes following technical solution:

A kind of ultra-wideband band-pass filter based on ground defect type grounding structure, comprises the circuit board that is arranged on the front side of double-sided copper-clad microstrip board and the grounding plate on the reverse side, is characterized in that:

The circuit board includes two parallel first coupled microstrip lines and second coupled microstrip lines, the first coupled microstrip line is connected to the input port through the input end transmission line, and the second coupled microstrip line is connected through the output end transmission line connected to the output port;

The grounding plate includes first, second and third inverted "S"-shaped recessed structures, and the first, second and third inverted "S"-shaped recessed structures are engraved on the grounding plate Etching away the air unit formed by the corresponding inverted "S" shape; wherein, the first inverted "S"-shaped defect structure is located in the center of the two parallel first and second coupled microstrip lines on the circuit board, The second inverted "S"-shaped subsidence structure and the third inverted "S"-type subsidence structure are symmetrically distributed on both sides of the first inverted "S"-type subsidence structure, and are respectively located at the output end transmission line 3 and the input end just below the center of the transmission line.

The ultra-wideband band-pass filter based on the ground defect type grounding structure of the present invention realizes the ultra-wideband performance of the filter while ensuring high selectivity outside the filter band. It is a DGS ultra-wideband bandpass filter whose bandwidth can cover any ultra-wideband frequency band (within 3.1-10.6GHz).

Description of drawings

Fig. 1 is the overall structure schematic diagram of the ultra-wideband band-pass filter based on the ground defect type grounding structure of the present invention;

Fig. 2 is the schematic diagram of the front circuit board structure of the ultra-wideband bandpass filter based on the ground defect type grounding structure of the present invention;

Fig. 3 is the structural schematic diagram of the back grounding plate of the UWB bandpass filter based on the ground defect type grounding structure of the present invention;

Fig. 4 is the structural schematic diagram of the middle part of the UWB bandpass filter based on the ground defect type grounding structure of the present invention;

Fig. 5 is the equivalent circuit diagram of the middle part structure of the UWB bandpass filter based on the ground defect type grounding structure of the present invention;

Fig. 6 is a schematic diagram of the frequency characteristics of the middle part structure of the UWB bandpass filter based on the ground defect type grounding structure of the present invention;

7 is a schematic diagram of the structure of the two sides of the front circuit board of the ultra-wideband bandpass filter based on the ground defect type grounding structure of the present invention;

Fig. 8 is the equivalent circuit diagram of the structure on both sides of the UWB bandpass filter based on the ground defect type grounding structure of the present invention;

9 is a schematic diagram of the frequency characteristics of the structure on both sides of the UWB bandpass filter based on the ground defect type grounding structure of the present invention;

Figure 10 is a comparison diagram of transmission responses of two structures;

FIG. 11 is a schematic diagram of measured frequency characteristics of the UWB bandpass filter based on the ground defect type grounding structure of the present invention.

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

Detailed ways

Referring to the accompanying drawings, the ultra-wideband bandpass filter based on the ground defect type grounding structure of the present invention includes a circuit board 11 arranged on the front side of a double-sided copper-clad microstrip board and a grounding plate 10 on the reverse side;

The circuit board 11 includes two parallel first coupled microstrip lines 1 and second coupled microstrip lines 2, the first coupled microstrip line 1 is connected to the input port 9 through the input transmission line 4, and the second coupled microstrip line 2 Connect to the output port 8 through the output transmission line 3;

The ground plate 10 includes first, second and third inverted "S"-shaped recessed structures (5, 6, 7), and the above-mentioned first, second and third inverted "S"-shaped recessed structures (5, 6, 7) are the air units formed by etching the corresponding inverted "S" shape on the ground plate 10; wherein, the first inverted "S"-shaped defect structure (5) is located on both sides of the circuit board 11. In the center directly below the parallel first and second coupled microstrip lines (1, 2), the second inverted "S"-shaped defect structure 6 and the third inverted "S"-shaped defect structure 7 are symmetrically distributed On both sides of the first inverted "S"-shaped depression structure 5, and in the center directly below the output transmission line 3 and the input transmission line 4 respectively.

The size of the inverted "S" shape area of the first inverted "S" type defect structure 5 is used to determine the center frequency of the ultra-wideband bandpass filter; the second inverted "S" type defect structure 6 and the third inverted The size of the inverted "S" shape of the "S"-shaped ground defect structure 7 affects the out-of-band selectivity of the ultra-wideband bandpass filter.

The first coupled microstrip line 1 and the second coupled microstrip line 2 are uniform transmission lines, or zigzag or other meander-shaped lines. The length and width of the first coupled microstrip line 1 and the second coupled microstrip line 2 are used to determine the high-end cutoff frequency of the ultra-wideband bandpass filter;

The width of the transmission line 3 at the output end and the transmission line 4 at the input end can affect the in-band and out-of-band selectivity of the UWB bandpass filter.

The transmission line 3 at the output end and the transmission line 4 at the input end are uniform transmission lines.

The inverted "S"-shaped recessed structures (5, 6, 7) on the reverse side are etched on the ground plane of the ground plane 10.

This shows, because the bandwidth of the UWB band-pass filter based on the ground defect type grounding structure of the present invention is by the area of first, second and the 3rd inverted " S " type ground defect structure (5,6,7) It is determined by the parallel first and second coupled microstrip lines (1, 2) and the output transmission line 3 and the input transmission line 4 connecting the input port 9 and the output port 8, so an ultra-wideband filter with any bandwidth can be designed as required device.

As shown in Figures 4, 5, and 6, the structure of the middle part of the ultra-wideband bandpass filter has ultra-wideband characteristics. The equivalent circuit diagram of the middle part structure of the UWB bandpass filter based on the ground defect type grounding structure of the present invention is as shown in Figure 5, including inductance L1, L2 and L3, capacitance C1, Ca and C3, wherein L1 and C1 are connected in series to form A branch, C3 and L3 are connected in parallel to form a branch, and L2 and Ca are at both ends. Fig. 6 has provided the circuit simulation result of the middle part structure of the UWB bandpass filter based on the ground defect type grounding structure of the present invention and the ANSOFT HFSS physical modeling simulation result, and the two coincide very well.

As shown in Figures 7, 8, and 9, the structures on both sides of the UWB bandpass filter have low-pass characteristics. Among them, the equivalent circuit diagram of the structure on both sides of the UWB bandpass filter based on the ground defect type grounding structure of the present invention includes inductors L1, L2, capacitors C1, C2, wherein L1 and C1 are connected in series to form a branch, and C2 forms a circuit. One branch, L2 at both ends. Figure 9 shows the circuit simulation results of the structure on both sides of the UWB bandpass filter based on the ground defect type grounding structure of the present invention and the simulation results of ANSOFT HFSS physical modeling, and the two are in good agreement.

As shown in Figure 10, compared with the dumbbell-shaped structure, the inverted "S"-shaped in-band response is very flat, and the out-of-band attenuation is very fast.

Through actual production and testing, the obtained transmission parameters are shown in Figure 11. The bandwidth can reach 3.3-10GHz, the maximum insertion loss is 0.8dB, the maximum passband return loss is -10dB, and the out-of-band attenuation is below -35dB.

The UWB bandpass filter based on the ground defect type grounding structure in the present invention can be other special-shaped structures other than the inverted "S" type, such as "E" type, "concave" type, etc.

The parallel coupled lines in the present invention can also be changed to zigzag or other bent structures.

The transmission line 3 at the output end and the transmission line 4 at the input end in the present invention may also be non-uniform transmission lines with step transformation.

The above embodiment is only a preferred embodiment of the present invention, which is used to further illustrate the present invention, and can not limit the scope of the present invention with this embodiment. Equivalent changes and modifications should still belong to the scope covered by the patent of the present invention.

Claims (6)

1. ultra wide band bandpass filter based on ground defective grounding structure comprises circuit board (11) on the front that is arranged on the little band plate of two-sided deposited copper and the ground plate (10) on the reverse side, it is characterized in that:

Described circuit board (11) comprises two parallel first coupled microstrip lines (1) and second coupled microstrip line (2), first coupled microstrip line (1) is connected with input port (9) by input transmission line (4), and second coupled microstrip line (2) is connected with output port (8) by output transmission line (3);

Described ground plate (10) comprises that first, second and the 3rd " S " type that falls lack earth subsidence structure (5,6,7), and it is that etching is gone the formed air element of the shape of falling the serpentine accordingly on ground plate (10) that described first, second lacks earth subsidence structure (5,6,7) with the 3rd " S " type that falls; Wherein, first " S " type that falls lack earth subsidence structure (5) be positioned at (11) two first, second parallel coupled microstrip lines of circuit board (1,2) under the center, second " S " type that falls lacks earth subsidence structure (6) and the 3rd " S " type that falls and lacks earth subsidence structure (7) and be symmetrically distributed in first and fall the both sides of the scarce earth subsidence structure (5) of " S " type, and lay respectively at output transmission line (3) and input transmission line (4) under the center.

2. the ultra wide band bandpass filter based on ground defective grounding structure as claimed in claim 1, it is characterized in that the size that described first " S " type that falls lacks the shape of falling the serpentine area of earth subsidence structure (5) is used to determine the centre frequency of ultra wide band bandpass filter; Second " S " type that falls lacks the big or small outer selectivity of band that influences ultra wide band bandpass filter of the shape of falling the serpentine that earth subsidence structure (6) and the 3rd " S " type that falls lacks earth subsidence structure (7).

3. the ultra wide band bandpass filter based on ground defective grounding structure as claimed in claim 1 is characterized in that, it is that " E " type or " recessed " type or other are abnormally-structured that described first, second and the 3rd " S " type that falls lack earth subsidence structure (5,6,7).

4. the ultra wide band bandpass filter based on ground defective grounding structure as claimed in claim 1 is characterized in that, described first coupled microstrip line (1) and second coupled microstrip line (2) are uniform transmission lines, or sawtooth pattern or other bending shape molded lines.

5. the ultra wide band bandpass filter based on ground defective grounding structure as claimed in claim 1, it is characterized in that the length of described first coupled microstrip line (1) and second coupled microstrip line (2) and width are used to determine the high-end cut-off frequency of ultra wide band bandpass filter; The width of described output transmission line (3) and input transmission line (4) can influence the interior and outer selectivity of band of band of ultra wide band bandpass filter.

6. the ultra wide band bandpass filter based on ground defective grounding structure as claimed in claim 1 is characterized in that, described output transmission line (3) and input transmission line (4) are the transmission lines of the inhomogeneous form of uniform transmission line or step conversion.

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