CN206564311U - The plane bandpass filter that a kind of Wide stop bands suppress - Google Patents

Abstract

The utility model discloses a planar bandpass filter with wide stopband suppression, which comprises an input port, an output port and four sequentially cascaded resonators, which are respectively the first, second, third and fourth resonators, Wherein the first and fourth resonators are uniform impedance one-half wavelength resonators, the second and third resonators are uniform impedance one-quarter wavelength resonators, and the four sequentially cascaded resonators pass parallel Coupling, the parasitic passband is suppressed by means of the transmission zero point generated by the coupled line and the stub line; the feeder of the input port is coupled in parallel to one side of the first resonator, and the feeder of the output port is coupled in parallel to the fourth resonator side. The utility model can suppress multiple parasitic frequency bands at the same time, and then realize the characteristics of ultra-wide stop band, has the advantages of simple and reliable structure, low production cost, more flexible selectivity, etc., and can meet the requirements of small size, fast roll-off, ultra-wide The design requirements of a bandpass filter with good performance and wide stopband.

Description

A Planar Bandpass Filter with Wide Stopband Rejection

technical field

The utility model relates to the technical field of high-frequency devices, in particular to a planar bandpass filter for 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, and the space electromagnetic spectrum is becoming more and more dense, which makes the frequency interference between different wireless communication systems more and more serious. In wireless communication systems, bandpass filters are an important component. The performance of its stop band determines the degree of frequency interference in the entire communication system. 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 some parasitic passbands.

Contents of the invention

The purpose of the utility model is to overcome the deficiencies of the prior art, and propose a planar bandpass filter with wide stopband suppression, which can simultaneously suppress multiple spurious frequency bands, and then realize the characteristics of ultra-wide stopband; it has a structure Simple and reliable, low manufacturing cost, more flexible selectivity, etc., can meet the design requirements of a band-pass filter with small size, fast roll-off, and ultra-wide stop band with good performance, and is suitable for various communication systems and industrialized production.

In order to achieve the above purpose, the technical solution provided by the utility model is: a planar bandpass filter with wide stopband suppression, including an input port, an output port and four sequentially cascaded resonators, respectively the first and the second 2. The third and fourth resonators, wherein the first and fourth resonators are one-half wavelength resonators with uniform impedance, and the second and third resonators are one-quarter wavelength resonators with uniform impedance. Four sequentially cascaded resonators are coupled in parallel, and the parasitic passband is suppressed by means of the transmission zero point generated by the coupled line and the stub; the feed line of the input port is coupled in parallel on one side of the first resonator, and the output The feed lines of the ports are coupled in parallel on one side of the fourth resonator.

One end of the uniform impedance half-wavelength resonator is bent into an L shape, and the other end is bent into a U shape, and the coupling characteristics are mainly determined by the L-shaped stub line and the length of the coupling line and the coupling position; the uniform impedance four One end of the one-half-wavelength resonator is bent into an L shape, and the other end is a short-circuit line. The coupling characteristics are mainly determined by the length of the L-shaped stub line, the length of the coupling line, and the coupling position; the feeder lines of the input port and the output port are not connected with the The open ends are phase-fed and coupled to each other in the middle of the resonator.

Both the input port and the output port are 50 ohm impedance matched.

Compared with the prior art, the utility model has the following advantages and beneficial effects:

1. The utility model sets multiple transmission zero points by adjusting the lengths of parallel coupling lines and stub lines between each resonator, thereby realizing the characteristic of ultra-wide stop band.

2. The structure of the utility model adopts a half-wavelength open line and a quarter-wavelength short-circuit line to realize a uniform impedance resonator. In addition, the size of the filter is greatly compressed by multiple folding and bending. The entire design has simple structure, good characteristics, low production cost, can be effectively used in various communication systems, and is suitable for industrialized mass production.

Description of drawings

Fig. 1 is a schematic structural diagram of a planar bandpass filter of the present invention.

Fig. 2 is a simulation result diagram of scattering parameters of the planar bandpass filter of the present invention.

FIG. 3 is a partial schematic diagram of FIG. 2 .

detailed description

Below in conjunction with specific embodiment the utility model is further described.

Referring to Fig. 1, the planar bandpass filter provided by this embodiment is integrally fabricated on a double-sided copper-clad microstrip dielectric board 7, and the same surface of the dielectric board 7 is respectively provided with input ports Port1 for feeding in electromagnetic wave signals , the output port Port2 is used to feed out the electromagnetic wave signal, and four resonators cascaded in sequence are the first, second, third, and fourth resonators 2, 3, 4, and 5 respectively. The other side of the dielectric board 7 is a copper-clad grounding board. Wherein the first and fourth resonators 2 and 5 are uniform impedance one-half wavelength resonators, the second and third resonators are uniform impedance one-quarter wavelength resonators 3 and 4, and the four are successively The connected resonators are coupled in parallel, and the parasitic passband is suppressed by means of the transmission zero point generated by the coupled line and the stub line. One end of the uniform impedance half-wavelength resonator is bent into an L shape, and the other end is bent into a U shape. The coupling characteristics are mainly determined by the length and coupling position of the L-shaped stub and coupling line; the uniform impedance quarter wavelength One end of the resonator is bent into an L-shape, and the other end is a short-circuit line. The coupling characteristics are mainly determined by the length of the L-shaped stub line, the length of the coupling line, and the coupling position; 8 and 9 in the figure are ground vias, which need to be soldered and covered. The copper ground plate is connected to the short circuit terminal. The feeder 1 of the input port Port1 is coupled in parallel to one side of the first resonator 2, the feeder 6 of the output port Port2 is coupled in parallel to one side of the fourth resonator 5, and the feeder 2 of the input port Port1 and the feeder 6 of the output port Port2 are not connected. Feed with the open circuit end, couple with the middle part of the resonator, and both the input port Port1 and the output port Port2 are 50 ohm impedance matched.

Referring to Fig. 2, it shows the simulation results of the scattering parameters of the above-mentioned planar bandpass filter of the present embodiment, its center frequency is 1Ghz, the horizontal axis represents the signal frequency of the planar bandpass filter, and the vertical axis represents the amplitude, including the insertion loss S The magnitude of ₂₁ and the magnitude of return loss S ₁₁ , where S ₁₁ represents the return loss of Port1, and 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 of this embodiment, part of the power of the signal is reflected back to the signal source, and the reflected power becomes reflected power. The 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 |. It can be seen from Fig. 2 and Fig. 3 that the center frequency of the planar bandpass filter of this embodiment is 1Ghz, the absolute value of the insertion loss in the passband is less than 3dB, the absolute value of the return loss is greater than 15dB, and the characteristics in the passband are very good. The -20dB stopband suppression starts from 1.1Ghz, the highest exceeds 16.5Ghz, and the -19.6dB stopband suppression exceeds 20dB. The spurious passband is well suppressed, and the out-of-band characteristics are satisfactory.

The above-described embodiment is only a preferred embodiment of the utility model, not to limit the scope of implementation of the utility model, so all changes made according to the shape and principle of the utility model should be covered by the protection of the utility model within range.

Claims (3)

1. A planar bandpass filter suppressed by a wide stop band, characterized in that: comprise an input port, an output port and four successively cascaded resonators, respectively the first, second, third and fourth resonators , wherein the first and fourth resonators are uniform impedance one-half wavelength resonators, the second and third resonators are uniform impedance one-quarter wavelength resonators, and the four sequentially cascaded resonators pass Parallel coupling, the parasitic passband is suppressed by means of the transmission zero point generated by the coupled line and the stub; the feeder of the input port is coupled in parallel to one side of the first resonator, and the feeder of the output port is coupled in parallel to the fourth resonator side of the device. 2. The planar bandpass filter of a kind of wide stopband suppression according to claim 1, characterized in that: one end of the uniform impedance 1/2 wavelength resonator is bent into an L shape, and the other end is bent into a U shape ; One end of the uniform impedance quarter-wavelength resonator is bent into an L shape, and the other end is a short circuit; the feeders of the input port and the output port are not fed with the open end, and are coupled with the middle part of the resonator . 3. A planar bandpass filter with wide stopband suppression according to claim 1, characterized in that: said input port and output port are both 50 ohm impedance matching.