CN104409816A - Planar Bandpass Filter with Ultra-Wide Stopband Rejection - Google Patents

Abstract

The invention discloses a plane band-pass filter for ultra-wide stop band suppression, which is manufactured on a double-sided copper-clad microstrip plate in a printed circuit board mode, wherein an input end feeder head port1 and an output end feeder head port2 for inputting and outputting electromagnetic wave signals, a first port feeder, a second port feeder and at least three microstrip resonators are respectively manufactured on the same side of the double-sided copper-clad microstrip plate, and the microstrip resonators are half-wavelength uniform impedance resonators. By adjusting the coupling position between the microstrip resonators and the port feeder line, the parasitic passband of the planar band-pass filter can be inhibited, the out-of-band characteristic of the resonators is greatly improved, and the ultra-wide stopband inhibition is realized. The plane band-pass filter provided by the invention has the advantages of simple structure and ultra-wide stop band.

Description

Planar Bandpass Filter with Ultra-Wide Stopband Rejection

technical field

The invention relates to the technical field of planar bandpass filters, in particular to a planar bandpass filter for ultra-wide stopband suppression.

Background technique

In recent years, with the rapid development of wireless communication technology, more and more microwave frequency resources are used by communication systems, the space electromagnetic spectrum is becoming increasingly dense, and the interference between wireless communication systems is becoming more and more serious. Bandpass filters As one of the important components in the communication system, its performance determines the working quality of the system to a large extent. In order to effectively suppress the interference signal, the wide stopband filter has become one of the research hotspots in the microwave field.

In order to design a band-pass filter with small size, small in-band loss, fast roll-off, and ultra-wide stop band, scholars have proposed many new resonator structures, some of which do show good performance, such as for To achieve wide stopband suppression characteristics, finger capacitor resonators and step impedance resonators are often used to push up the first spurious frequency, so that the spurious passband is far away from the working passband, thereby increasing the frequency range of the stopband; or using the defective ground structure The transmission zero is introduced to suppress the strength of the parasitic passband, thereby improving the suppression degree in the wide stopband range. However, the above measures perform poorly in suppressing the spurious passband at the multiplier.

The quarter-wavelength stepped impedance resonator shown in the data, the structure diagram of the quarter-wavelength stepped impedance resonator is shown in Figure 1. For details, please refer to 2006, Taiwanese scholar Shih-Cheng Lin et al. in IEEE Trans. Microw.TheoryTec published titled "Wide-stopband microstripbandpass filters using dissimilar quarter-wavelength stepped-impedance resonators". Figure 1 shows that four quarter-wavelength stepped impedance resonators with different structures are used, so that the fundamental frequency fo of each resonator is the same, and the harmonic frequencies fspi (i=1,2,3,…) are distributed in In different places, the spurious passband of the harmonic frequency is suppressed, and the frequency range of the stopband is expanded. Figure 1 also shows the filter structure and its performance.

Contents of the invention

The object of the present invention is to overcome the shortcomings and deficiencies of the prior art, and provide a planar bandpass filter for ultra-wide stopband suppression. The present invention proposes a planar bandpass filter design scheme, by rationally arranging the feeding position of the input and output ports and the coupling position between the resonators, thereby effectively suppressing the spurious passband generated by the periodicity of the frequency response of the transmission line, especially It can realize the suppression of double frequency to ten times frequency, and then expand the stop band of the filter in a large range. The main advantages are: ultra-wide stop band, simple and reliable structure, small size, and low passband loss.

The object of the present invention is achieved through the following technical solutions:

A planar bandpass filter with ultra-wide stopband suppression, fabricated on a double-sided copper microstrip board 1 in the form of a printed circuit board,

On the same surface of the double-sided copper-clad microstrip board 1, an input end feeder port1 for inputting electromagnetic wave signals, an output end feeder port2 for outputting electromagnetic wave signals, a first port feeder 2, and a second port feeder are respectively fabricated. 6 and at least three microstrip resonators, the other side of the double-sided copper clad microstrip board 1 is a copper clad ground plane;

The input end feeder port1 is linearly connected to the first side of the first port feeder 2, the output end feeder port2 is linearly connected to the second side of the second port feeder 6, and the input end feeder port1 and the output feeder head port2 are arranged diagonally on the double-sided copper-clad microstrip board 1, and the microstrip resonators are arranged side by side on their diagonals;

Each of the microstrip resonators includes three sections of microstrips, wherein the first side microstrip and the second side microstrip are located at both ends of the middle microstrip and are vertically connected to it, and the first side microstrip and the second side microstrip The two side microstrips have opposite directions, and the middle microstrip is parallel to the first port feeder and the second port feeder.

Preferably, the microstrip resonators are uniform impedance half-wavelength microstrip resonators.

Preferably, there are three microstrip resonators, which are the first microstrip resonator 3 , the second microstrip resonator 4 and the third microstrip resonator 5 .

Preferably, the first microstrip resonator 3 includes a first microstrip 3-1, a second microstrip 3-2, and a third microstrip 3-3, wherein the first microstrip and the third microstrip The strips are located at both ends of the second microstrip and are vertically connected thereto, and the orientation of the first microstrip and the third microstrip are opposite, the second microstrip is parallel to the feeder line of the first port, and the two Adjacent and there is a first coupling gap 7 between them;

The second microstrip resonator 4 includes a fourth microstrip 4-1, a fifth microstrip 4-2, and a sixth microstrip 4-3, wherein the fourth microstrip and the sixth microstrip are located at the The two ends of the fifth microstrip are vertically connected to it, and the orientation of the fourth and sixth microstrips is opposite, and the fifth and second microstrips are parallel, adjacent and There is a second coupling gap 8 between them;

The third microstrip resonator 5 includes a seventh microstrip 5-1, an eighth microstrip 5-2, and a ninth microstrip 5-3, wherein the seventh microstrip and the ninth microstrip are located at the The two ends of the eighth microstrip are vertically connected to it, and the seventh microstrip and the ninth microstrip are facing oppositely, the eighth microstrip is parallel to the fifth microstrip, and the two are adjacent and There is a third coupling gap 9 between them; the eighth microstrip is also parallel to the feeder line of the second port, the two are adjacent and there is a fourth coupling gap 10 therebetween.

Preferably, the port on the side where the second microstrip is connected to the first microstrip is flush with the first side of the first port feeder; the port on the side where the eighth microstrip is connected to the ninth microstrip and The second side of the second port feeder line is flush; the fifth microstrip is flush with the second side of the first port feeder line on the side where the fifth microstrip is connected to the fourth microstrip; the fifth microstrip is flush with The port on one side of the sixth microstrip connection is flush with the first side of the feeder line of the second port.

Preferably, the length values of the first side microstrip and the second side microstrip of any microstrip resonator are respectively equal to any value in each of the following nine sets of data, wherein the nine sets of data Respectively (λ/8, 3λ/8), (λ/12, λ/4, 5λ/12), (λ/16, 3λ/16, 5λ/16, 7λ/16), (λ/20, 3λ/16) /20, 7λ/20, 7λ/20), (λ/24, λ/8, 5λ/24, 3λ/8, 11λ/24), (λ/28, 3λ/28, 5λ/28, λ/4 , 9λ/28, 11λ/28, 13λ/28), (λ/32, 3λ/32, 5λ/32, 7λ/32, 9λ/32, 11λ/32, 13λ/32, 15λ/32), (λ /36, λ/12, 5λ/36, 7λ/36, 11λ/36, 13λ/36, 5λ/12, 17λ/36), (λ/40, 3λ/40, λ/8, 7λ/40, 9λ /40, 11λ/40, 13λ/40, 3λ/8, 17λ/40, 19λ/40), where λ is the wavelength of the planar bandpass filter for ultra-wide stopband suppression.

Preferably, the length L ₂ of the first microstrip, the length L ₄ of the third microstrip, the length L ₅ of the fourth microstrip, the length L ₇ of the sixth microstrip, the length of the first microstrip The length L ₈ of the seven microstrips and the length L ₁₀ of the ninth microstrip are respectively equal to any value in each of the following six sets of data, wherein the nine sets of data are respectively, wherein The above six sets of data are (λ/8), (λ/12), (λ/16, 3λ/16, 5λ/16, 7λ/16), (λ/20, 3λ/20, 7λ/20, 7λ /20), (λ/28, 3λ/28, 5λ/28, λ/4, 9λ/28, 11λ/28, 13λ/28), (λ/32, 3λ/32, 5λ/32, 7λ/32 , 9λ/32, 11λ/32, 13λ/32, 15λ/32), where λ is the wavelength of the planar bandpass filter suppressed by the ultra-wide stopband.

Preferably, the length L ₂ =λ/8 of the first microstrip, the length L ₄ =λ/16 of the third microstrip, the length L ₅ =λ/20 of the fourth microstrip, the The length of the sixth microstrip is L ₇ =λ/28, the length of the seventh microstrip is L ₈ =λ/32, and the length of the ninth microstrip is L ₁₀ =λ/12.

Compared with the prior art, the present invention has the following advantages and effects:

1. The present invention realizes the suppression of multiple frequency multiplications by adjusting the coupling position between the port feeder and the resonator to the voltage zero point of the spurious frequency.

2. The present invention adjusts the coupling position between the resonators to the voltage zero point of the spurious frequency, and also realizes suppression of multiple frequency multiplications, thereby realizing an ultra-wide stop band.

3. The present invention utilizes a uniform impedance resonator to realize an ultra-wide stop band, thereby reducing design difficulty.

Description of drawings

FIG. 1 is a schematic structural view of a quarter-wavelength stepped impedance resonator in the prior art;

Fig. 2 is the structural representation of the planar bandpass filter that ultra-wide stopband suppresses among the present invention;

Fig. 3 is the dimensional figure of the planar bandpass filter that ultra-wide stopband suppresses among the present invention;

Fig. 4 is the scattering parameter simulation result figure of the planar bandpass filter that ultra-wide stopband suppresses among the present invention;

Fig. 5 is the local enlargement figure of the scattering parameter simulation result figure of the planar bandpass filter that ultra-wide stopband suppresses among the present invention;

In the figure, reference signs are: 1-double-sided copper track microstrip board, 2-first port feeder, 3-first microstrip resonator, 3-1-first microstrip, 3-2-second microstrip Strip, 3-3-third microstrip, 4-second microstrip resonator, 4-1-fourth microstrip, 4-2-fifth microstrip, 4-3-sixth microstrip, 5-th Three microstrip resonators, 5-1-seventh microstrip, 5-2-eighth microstrip, 5-3-ninth microstrip, 6-second port feeder, 7-first coupling gap, 8-the first The second coupling gap, 9-the third coupling gap, 10-the fourth coupling gap.

Detailed ways

In order to make the object, technical solution and advantages of the present invention more clear and definite, the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

Example

The structural schematic diagram and size diagram of the planar bandpass filter for ultra-wide stopband suppression proposed in this embodiment are shown in Fig. 2 and Fig. 3 respectively. Copper dielectric substrates can be easily fabricated using techniques such as mechanical engraving, laser engraving, and circuit board corrosion.

On the same surface of the double-sided copper-clad microstrip board 1, an input feeder port1 for inputting electromagnetic wave signals, an output feeder port2 for outputting electromagnetic wave signals, a first port feeder 2, a second port feeder 6 and There are at least three microstrip resonators, and the other side of the double-sided copper-clad microstrip board 1 is a copper-clad grounding board. Among them, the microstrip resonators are uniform impedance half-wavelength microstrip resonators; the input end feeder head port1 and the output end feeder head port2 both have a matching impedance of 50 ohms.

The input end feeder head port1 is linearly connected to the first side of the first port feeder 2, and the output end feeder head port2 is linearly connected to the second side of the second port feeder 6, and they are diagonally formed on the double-sided copper-clad microstrip board 1 line arrangement, the microstrip resonators are arranged side by side on their diagonals.

The microstrip resonators used in the planar bandpass filter design of ultra-wide stopband suppression include three sections of microstrips, and the composition structure is as follows: the first side microstrip and the second side microstrip of any microstrip resonator are both Located at both ends of the middle microstrip and vertically connected to it, and the first side microstrip and the second side microstrip face opposite, and the middle microstrip is connected to the first port feeder and the second port The feeders are parallel.

As shown in FIG. 2 , three microstrip resonators are used in this embodiment, which are the first microstrip resonator 3 , the second microstrip resonator 4 , and the third microstrip resonator 5 .

Wherein, the first microstrip resonator 3 includes a first microstrip, a second microstrip, and a third microstrip, wherein the first microstrip and the third microstrip are located at both ends of the second microstrip, perpendicular to the second microstrip connected, and the first microstrip and the third microstrip are parallel to each other, facing oppositely; the second microstrip is parallel to the first port feeder, and there is a first coupling gap 7 between them;

Wherein, the second microstrip resonator 4 includes the fourth microstrip, the fifth microstrip, and the sixth microstrip, wherein the fourth microstrip and the sixth microstrip are located at the two ends of the fifth microstrip, respectively connected to the fifth microstrip vertically connected, and the fourth microstrip and the sixth microstrip are parallel to each other, facing oppositely; the fifth microstrip is parallel to the second microstrip, and there is a second coupling gap 8 between them;

Wherein, the 3rd microstrip resonator 5 comprises the 7th microstrip, the 8th microstrip, the 9th microstrip, wherein the 7th microstrip and the 9th microstrip are positioned at the two ends of the 8th microstrip, respectively with the 8th microstrip vertically connected, and the seventh microstrip and the ninth microstrip are parallel to each other, facing oppositely; the eighth microstrip is parallel to the fifth microstrip, and there is a third coupling gap 9 between them; the eighth microstrip Parallel to the fifth microstrip, adjacent to each other with a third coupling gap 9 therebetween; the eighth microstrip is also parallel to the second port feeder line, adjacent to them with a fourth coupling gap 10 therebetween .

It should also be noted that, in this embodiment, the port on the side where the second microstrip is connected to the first microstrip is flush with the first side of the first port feeder line; The port on the side where the ninth microstrip is connected is flush with the second side of the feeder line of the second port; the port on the side where the fifth microstrip is connected to the fourth microstrip is flush with the second side of the feeder line at the first port flush; the fifth microstrip is flush with the port on one side of the sixth microstrip and the first side of the feeder line of the second port.

For the half-wavelength resonator in this embodiment, the voltage distribution at the fundamental frequency and other spurious frequencies is very different. Specifically, the distribution positions of the voltage maximum point and the voltage zero point are different. If the wavelength is λ, the fundamental frequency is f ₀ , then 2f ₀ , 3f ₀ , 4f ₀ , ...nf ₀ are other spurious frequencies respectively. According to the voltage distribution of the transmission line, the distribution of voltage zero points on the transmission line at each frequency can be calculated separately, as follows:

In order to suppress the spurious frequency of the filter, the design of this filter innovatively moves the coupling position to near the voltage zero point of the spurious frequency, thereby effectively attenuating the spurious frequency.

The length value rules of the microstrip on the first side and the microstrip on the second side of the specific microstrip resonator are as follows:

The length values of the first-side microstrip and the second-side microstrip of any microstrip resonator are respectively equal to any value in each of the following nine sets of data, and it must be ensured that the values of each set of data have a corresponding relationship , wherein the nine sets of data are (λ/8, 3λ/8), (λ/12, λ/4, 5λ/12), (λ/16, 3λ/16, 5λ/16, 7λ/16) , (λ/20, 3λ/20, 7λ/20, 7λ/20), (λ/24, λ/8, 5λ/24, 3λ/8, 11λ/24), (λ/28, 3λ/28, 5λ/28, λ/4, 9λ/28, 11λ/28, 13λ/28), (λ/32, 3λ/32, 5λ/32, 7λ/32, 9λ/32, 11λ/32, 13λ/32, 15λ/32), (λ/36, λ/12, 5λ/36, 7λ/36, 11λ/36, 13λ/36, 5λ/12, 17λ/36), (λ/40, 3λ/40, λ/ 8, 7λ/40, 9λ/40, 11λ/40, 13λ/40, 3λ/8, 17λ/40, 19λ/40), wherein λ is the wavelength of the planar bandpass filter suppressed by the ultra-wide stopband.

In this embodiment, for the case of using three microstrip resonators, the length L ₂ of the first microstrip, the length L ₄ of the third microstrip, the length L ₅ of the fourth microstrip, the The length values of the length L ₇ of the sixth microstrip, the length L ₈ of the seventh microstrip, and the length L ₁₀ of the ninth microstrip are respectively equal to any value in each of the following six sets of data , wherein the nine sets of data are respectively, wherein the six sets of data are (λ/8), (λ/12), (λ/16, 3λ/16, 5λ/16, 7λ/16), (λ /20, 3λ/20, 7λ/20, 7λ/20), (λ/28, 3λ/28, 5λ/28, λ/4, 9λ/28, 11λ/28, 13λ/28), (λ/32 , 3λ/32, 5λ/32, 7λ/32, 9λ/32, 11λ/32, 13λ/32, 15λ/32), where λ is the wavelength of the planar bandpass filter suppressed by the ultra-wide stopband.

For example, in order to suppress 2f ₀ , in this filter design, the coupling position of the first port feeder 2 and the first microstrip resonator 3 is adjusted to the voltage zero point of the resonator at 2f ₀ frequency, that is, L ₂ =λ/8 or 3λ/8. If L ₂ =λ/8 is selected, at 6f ₀ , L ₂ =λ/8 is also the voltage zero point, that is, while 2f ₀ is suppressed, 6f ₀ is also suppressed, and at 10f ₀ , L2=λ/8 is the same Also for the voltage zero point, that is, 10f ₀ is also suppressed.

To suppress 3f ₀ , the coupling position of the second port feeder 6 and the third microstrip resonator 5 is adjusted to the voltage zero point of the resonator at the frequency of 3f ₀ , that is, L ₁₀ =λ/12 or λ/4 or 5λ/12 . If L ₁₀ =λ/12 is selected, at 9f ₀ , L ₁₀ =λ/12 is also the voltage zero point, that is, 9f ₀ is also suppressed while 3f ₀ is suppressed.

To suppress 4f ₀ , adjust the coupling position of the first microstrip resonator 3 and the second microstrip resonator 4 to the voltage zero point of the resonator at the frequency of 4f ₀ , that is, L ₄ =λ/16 or 3λ/16 or 5λ /16 or 7λ/16, in order to reduce the size of the resonator, choose λ/16.

To suppress 5f ₀ , adjust the coupling position of the first microstrip resonator 3 and the second microstrip resonator 4 to the voltage zero point of the resonator at the frequency of 5f ₀ , that is, L ₅ =λ/20 or 3λ/20 or λ /4 or 7λ/20 or 9λ/20, in order to reduce the size of the resonator, choose λ/20.

In order to suppress 7f ₀ , adjust the coupling position of the second microstrip resonator 4 and the third microstrip resonator 5 to the voltage zero point of the resonator at the frequency of 7f ₀ , that is, L ₇ =λ/28 or 3λ/28 or 5λ /28 or λ/49λ/28 or 11λ/28 or 13λ/28, in order to reduce the resonator size, choose λ/28.

In order to suppress 8f ₀ , adjust the coupling position of the second microstrip resonator 4 and the third microstrip resonator 5 to the voltage zero point of the resonator at the frequency of 8f ₀ , that is, L ₈ =λ/32 or 3λ/32 or 5λ /32 or 7λ/32 or 9λ/32 or 11λ/32 or 13λ/32 or 15λ/32, in order to reduce the resonator size, choose λ/32.

As shown in the dimension diagram of the planar bandpass filter of ultra-wide stopband suppression in Fig. 3, the lengths of the input end feeder head port1 and the output end feeder head port2 in this planar bandpass filter are both L ₁₂ =3mm, and the widths are L ₁₃ =2.2mm, the length of the first port feeder and the second port feeder are both L ₁ =L ₁₁ =23.5mm, and the width is W ₁ =0.5mm. The base frequency of the corresponding planar bandpass filter for ultra-wide stopband suppression is f ₀ =2 GHz, and the wavelength λ=103 millimeters.

The lengths of the first microstrip, the second microstrip, the third microstrip, the fourth microstrip, the fifth microstrip, the sixth microstrip, the seventh microstrip, the eighth microstrip and the ninth microstrip are L ₂ =14.2mm, L ₃ =34.9mm, L ₄ =3.3mm, L ₅ =7.6mm, L ₆ =39.4mm, L ₇ =6.3mm, L ₈ =5.3, L ₉ =35.3mm, L ₁₀ =11.3mm , and the width is W ₂ =1 mm. At the same time, the corresponding dielectric constant of the microstrip line is ε _r =2.55, and the dielectric height h=0.8mm.

The distance values of the first coupling gap, the second coupling gap, the third coupling gap, and the fourth coupling gap are respectively S ₁ =0.3 mm, S ₂ =0.9 mm, S ₃ =0.8 mm, and S ₄ =0.3 mm.

In order to define the positional relationship between the three microstrip resonators, the distance L ₁₄ between the fourth microstrip and the seventh microstrip = 27.9 mm, the distance L ₁₅ between the third microstrip and the sixth microstrip = 27.1 mm, the distance L ₁₆ between the sixth microstrip and the seventh microstrip = 16.6 mm, the distance L ₁₇ between the sixth microstrip and the ninth microstrip = 23.8 mm.

FIG. 4 is a diagram showing simulation results of scattering parameters of the planar bandpass filter for ultra-wide stopband suppression proposed in this embodiment. The center frequency of the filter is 2GHz, the horizontal axis represents the signal frequency of the bandpass filter of the present invention, and the vertical axis represents the magnitude, including the magnitude of the insertion loss _S21 and the magnitude of the return loss _S11 , where _S11 represents the echo of Port1 Loss, S ₂₁ represents the insertion loss of Port1 and Port2. Insertion loss represents the relationship between the input power of a signal and the output power of another port signal, and its corresponding mathematical function is: output power/input power (dB)=20*log|S ₂₁ |. During the signal transmission process of the planar bandpass filter with ultra-wide stopband suppression proposed in this embodiment, part of the power of the signal is reflected back to the signal source, and the reflected power becomes reflected power. Return loss represents the relationship between the input power of the port signal and the reflected power of the signal, and the corresponding mathematical function is as follows: reflected power/incident power (dB) = 20*log|S ₁₁ |. As can be seen from Fig. 4 and Fig. 5, the center frequency of the planar bandpass filter of ultra-wide stopband suppression proposed by the present embodiment is 2GHz, the absolute value of insertion loss in the passband is less than 1.7dB, and the absolute value of return loss is greater than 22dB. The in-band characteristics are very good. The 20dB stopband rejection starts at 2.2GHz and goes up to 17GHz, while the 18dB stopband rejection exceeds 20GHz. The spurious passband of the 10-fold frequency is suppressed, and the out-of-band characteristics are satisfactory.

FIG. 5 is a partially enlarged schematic diagram of FIG. 4 .

In the embodiments of the present invention, in order to overcome the shortcomings and deficiencies of the prior art, a planar bandpass filter design scheme for ultra-wide stopband suppression is provided. A structure comprising a half-wavelength cascaded resonator, an input end feeder for feeding in electromagnetic wave signals, and an output end feeder for feeding out electromagnetic wave signals is adopted. The feeder at the input end and the feeder at the output end are coupled on both sides of the half-wavelength resonator in parallel, and the ports of the feeder at the input end and the feeder at the output end are both located at 1/4 wavelength and 1 /20 between wavelengths.

By adopting the above-mentioned structure, the present invention realizes the effective suppression of double frequency and decadal frequency at the same time, and further realizes the characteristic of ultra-wide stop band. On the other hand, the present invention has multiple folds and bends, so that the volume of the filter is reduced. Generally speaking, the invention is simple and reliable, has low production cost, is suitable for industrial mass production, and is applicable to various communication systems.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (8)

1. a planar band-pass filter suppressed by an ultra-wide stop band is fabricated on a double-sided copper microstrip board (1) in the mode of a printed circuit board, and is characterized in that: On the same side of the double-sided copper-clad microstrip board (1), an input end feeder port1 for inputting electromagnetic wave signals, an output end feeder port2 for outputting electromagnetic wave signals, a first port feeder (2), The second port feeder (6) and at least three microstrip resonators, the other side of the double-sided copper-clad microstrip board (1) is a copper-clad grounding board; The input end feeder port1 is linearly connected to the first side of the first port feeder (2), the output end feeder port2 is linearly connected to the second side of the second port feeder (6), the The input feeder port1 and the output feeder port2 are arranged diagonally on the double-sided copper-clad microstrip board (1), and the microstrip resonators are arranged side by side on their diagonals; Each of the microstrip resonators includes three sections of microstrips, wherein the first side microstrip and the second side microstrip are located at both ends of the middle microstrip and are vertically connected to it, and the first side microstrip and the second side microstrip The two side microstrips have opposite directions, and the middle microstrip is parallel to the first port feeder and the second port feeder. 2. The planar bandpass filter for ultra-wide stopband suppression according to claim 1, characterized in that: said microstrip resonators are uniform impedance half-wavelength microstrip resonators. 3. according to claim 1 and 2 described planar band-pass filters of ultra-wide stop band suppression, it is characterized in that: the quantity of described microstrip resonator is three, is respectively the first microstrip resonator (3) , the second microstrip resonator (4), and the third microstrip resonator (5). 4. the planar band-pass filter that any ultra-wide stopband suppresses according to claim 3 is characterized in that: The first microstrip resonator (3) includes a first microstrip (3-1), a second microstrip (3-2), and a third microstrip (3-3), wherein the first microstrip and The third microstrip is located at both ends of the second microstrip and is vertically connected thereto, and the orientation of the first microstrip and the third microstrip are opposite, and the second microstrip and the first port The feeders are parallel, and the two are adjacent with a first coupling gap (7) between them; The second microstrip resonator (4) includes a fourth microstrip (4-1), a fifth microstrip (4-2), and a sixth microstrip (4-3), wherein the fourth microstrip and The sixth microstrip is located at both ends of the fifth microstrip and vertically connected thereto, and the orientation of the fourth and sixth microstrips is opposite, and the fifth and second microstrips are The strips are parallel, adjacent to each other with a second coupling gap (8) between them; The third microstrip resonator (5) includes a seventh microstrip (5-1), an eighth microstrip (5-2), and a ninth microstrip (5-3), wherein the seventh microstrip and The ninth microstrip is located at both ends of the eighth microstrip and vertically connected thereto, and the orientation of the seventh microstrip and the ninth microstrip are opposite, and the eighth microstrip and the fifth microstrip The strips are parallel, the two are adjacent and there is a third coupling gap (9) between them; the eighth microstrip is also parallel to the second port feeder, the two are adjacent and there is a fourth coupling gap (10) between them . 5. The planar bandpass filter of ultra-wide stopband suppression according to claim 4, characterized in that: said second microstrip connects the port on one side with the first microstrip and the first port feeder of said first port one side is flush; the port on the side where the eighth microstrip is connected to the ninth microstrip is flush with the second side of the second port feeder; the side where the fifth microstrip is connected to the fourth microstrip The port is flush with the second side of the feeder line of the first port; the port on the side where the fifth microstrip is connected to the sixth microstrip is flush with the first side of the feeder line of the second port. 6. the planar bandpass filter of ultra-wide stopband suppression according to claim 1, is characterized in that: the first side microstrip of described any microstrip resonator and the length value of the second side microstrip are respectively Corresponds to any value in each of the following nine sets of data, where the nine sets of data are (λ/8, 3λ/8), (λ/12, λ/4, 5λ/12), (λ /16, 3λ/16, 5λ/16, 7λ/16), (λ/20, 3λ/20, 7λ/20, 7λ/20), (λ/24, λ/8, 5λ/24, 3λ/8 , 11λ/24), (λ/28, 3λ/28, 5λ/28, λ/4, 9λ/28, 11λ/28, 13λ/28), (λ/32, 3λ/32, 5λ/32, 7λ /32, 9λ/32, 11λ/32, 13λ/32, 15λ/32), (λ/36, λ/12, 5λ/36, 7λ/36, 11λ/36, 13λ/36, 5λ/12, 17λ /36), (λ/40, 3λ/40, λ/8, 7λ/40, 9λ/40, 11λ/40, 13λ/40, 3λ/8, 17λ/40, 19λ/40), where λ is all The ultra-wide stopband suppresses the wavelength of the planar bandpass filter. 7. The planar bandpass filter of ultra-wide stopband suppression according to claim 4, characterized in that: the length L ₂ of the first microstrip, the length L ₄ of the third microstrip, the first The length L ₅ of the four microstrips, the length L ₇ of the sixth microstrip, the length L ₈ of the seventh microstrip, and the length L ₁₀ of the ninth microstrip respectively correspond to the following six sets of data Any value in each group is equal, wherein the nine groups of data are respectively, and the six groups of data are (λ/8), (λ/12), (λ/16, 3λ/16, 5λ /16, 7λ/16), (λ/20, 3λ/20, 7λ/20, 7λ/20), (λ/28, 3λ/28, 5λ/28, λ/4, 9λ/28, 11λ/28 , 13λ/28), (λ/32, 3λ/32, 5λ/32, 7λ/32, 9λ/32, 11λ/32, 13λ/32, 15λ/32), where λ is the ultra-wide stopband suppression The wavelength of the planar bandpass filter. 8. The planar bandpass filter of ultra-wide stopband suppression according to claim 7, characterized in that: the length L ₂ of the first microstrip=λ/8, the length L ₄ of the third microstrip = λ/16, the length L ₅ of the fourth microstrip = λ/20, the length L ₇ of the sixth microstrip = λ/28, the length L ₈ of the seventh microstrip = λ/32, The length of the ninth microstrip is L ₁₀ =λ/12.