CN203166046U - Ultra-Wideband Filter Based on Double Stub Loaded Resonator - Google Patents

Abstract

The utility model discloses an ultra wide band filter based on a double-branch loading resonator, which comprises a micro-strip substrate, a front part, a back part and an input/output port, wherein the front part and the back part are respectively positioned on two surfaces of the micro-strip substrate, and the back part is used as a metal grounding plate of the filter; the front part comprises a first uniform transmission line unit, a second uniform transmission line unit, a first parallel coupling feeder line, a second parallel coupling feeder line and a double-branch loading resonator. The utility model discloses compact structure, the size is little, and is with low costs, and the characteristic is good.

Description

Ultra-Wideband Filter Based on Double Stub Loaded Resonator

technical field

The utility model relates to the technical field of filters, in particular to an ultra-broadband filter based on double-twig loaded resonators. the

Background technique

Ultra-wideband (UWB) filters have a variety of applications. UWB pulse wireless transmission technology for civilian use (the military started its research as early as the 1970s) is a revolutionary wireless communication technology, which has a much higher communication rate and capacity than 3G communication technology, and its occupation The frequency band is very wide, and its system requires the use of ultra-wideband filters. Ultra-wideband anti-collision radar systems used in automobiles, ultra-wideband imaging systems for imaging, ultra-wideband RFID systems for warehousing, and modern communication signal optimization coverage and repeater systems, etc., also require the use of ultra-wideband filters. Ultra-wideband pulse radar systems in military electronic countermeasures also use ultra-wideband filters. In 2002, the Federal Communications Commission (FCC) of the United States officially passed a proposal to use ultra-wideband (UWB) technology for civilian use. After that, the study of UWB filters has attracted extensive research interest in academia. In fact, there are many schemes for UWB filters. the

An ultra-wideband filter needs to be placed at the front end of the RF module of the ultra-wideband system so that the system can transmit UWB signals that comply with the FCC standard, and minimize interference outside the operating frequency. In addition, a large number of ultra-wideband matching problems need to be solved in the ultra-wideband system. For example, both the input and output of the amplifier need a good matching network to ensure the maximum transmission coefficient. Therefore, the UWB microwave filter is a key passive component in the UWB system, and its characteristics play a very important role in the overall performance of the system. Since the UWB system uses a very wide frequency band: it overlaps with many other wireless communication system frequency bands. The frequency range of UWB is 3.1-10.6GHZ, and the U-NII (Unlicensed national information infrastructure) frequency range has two parts, 5.15GHz to 5.35GHz and 5.75 to 5.85GHz. Although theoretically speaking, the UWB system has a very low transmit power spectrum density and should be able to "quietly coexist" with other systems, but in practical applications, the compatibility of the UWB system with other systems needs to be proved by experiments. In particular, there are still many unclear aspects about the working mechanism and characteristics of UWB systems, such as the out-of-band interference of UWB systems, that is, UWB devices may cause certain interference to wireless systems outside their operating frequency bands. It is difficult to accurately estimate the interference by theoretical calculation methods, such as interference to GPS, interference to personal communication system 900/1800MHzGSM, interference to wireless local area network IEEE802.11, etc., especially when there are many ultra-broadband devices in a certain area , and its concentration interference must be carefully considered. Therefore, it is particularly important to design related filters from the aspect of hardware to eliminate the interference of interference signals to the system. the

Filters are very important in ultra-wideband communication equipment, and various filters have different functional and characteristic requirements. The necessary functions of the band-pass filter at the receiving end are to avoid saturating the receiver front-end due to leakage of the output signal at the transmitting end, remove interfering signals such as image frequencies, and reduce power leakage from the local oscillator at the antenna end. The best performance of the bandpass filter at the receiving end includes high attenuation (to remove interference), and at the same time reduces the bandpass insertion loss that directly affects the sensitivity of the receiving end, so it must have steep out-of-band attenuation, good group delay and other characteristics. The basic function of the bandpass filter at the transmitter is to reduce the stray radiation power from the transmitter to avoid interference to other wireless communication systems. The main components of these useless signals are the second and third harmonics of the frequency of the transmitter signal and local oscillation. Another very important function is to attenuate the noise in the receiving frequency band of the transmitted signal and suppress it below the sensitivity of the receiver. the

After the U.S. Federal Communications Commission (FCC) freed the 3.1-10.6GHz frequency band for applications in the communication field in 2002, ultra-wideband short-range wireless communication has attracted great attention in the global communication technology field. The filter is an indispensable and widely used passive device in the communication system, and it has become one of the focuses of research. Since the ultra-wideband filter is required to work in a wide frequency range of 3.1-10.6GHz, and the filter is required to have a small size, traditional filter design methods cannot design such a wide-band filter. the

At present, the methods for realizing ultra-wideband include cascading low-pass and high-pass filters or using multi-mode resonator structures. Various transmission line structures such as parallel coupled lines, coplanar waveguides, microstrip lines, and striplines have been used in the design of UWB filters. However, as wireless communication products are becoming lighter, thinner, shorter, and smaller, the filter size is required to be smaller and smaller. Therefore, how to reduce the size of the filter while ensuring the performance of the ultra-wideband filter is also a major challenge in today's ultra-wideband filter design. the

Zhu Lei et al. proposed an ultra-wideband filter based on a multi-mode resonator structure in the article "Ultra-wideband bandpass filter using multiple-mode resonator" published in IEEE Microwave and Wireless Components Letter in 2005. Because of the simple design and better filter characteristics, this article has been cited a lot. However, the circuit size of this structure is large, and the stop band attenuation is slow, and the out-of-band rejection is poor. Zhu Lei and others then published the article "Compact UWB bandpass filter using stub-loaded multiple-mode resonator" in the IEEE Microwave and Wireless Components Letter in 2005, as shown in Figure 2, proposed a multi-mode resonator based on stub loading structure for improving the out-of-band characteristics of the ultra-wideband filter of the above-mentioned multimode structure and reducing the circuit size. Experimental results show that although the structure can reduce the size of the circuit, it does not greatly improve the out-of-band suppression and stop-band attenuation characteristics. the

Short-circuit and open-circuit stub loading have been used in the design of multi-frequency filters long ago, and the stub loading structure is also one of the main methods of UWB filter design. In the document "Development of Packaged Ultra-Wideband Bandpass Filters", a typical structure of loading branches is proposed, which is characterized by a simple structure and a large degree of freedom. This structure is a three-mode SIR structure, and the three resonance modes are independently controllable, which makes it easy to adjust the center resonance point and the entire passband range. We see that its passband is wide and flat, but the insertion loss of the stopband is not large enough, and there is a parasitic passband caused by half-wavelength repeatability. the

Utility model content

The purpose of the utility model is to overcome the shortcomings and deficiencies of the prior art, and provide an ultra-wideband filter based on double-stub loaded resonators. the

In order to achieve the above utility model purpose, the utility model adopts the following technical solutions:

The utility model is an ultra-broadband filter based on a double-twig loaded resonator, comprising a microstrip substrate, a front part, a back part, and an input/output port, and the front part and the back part are respectively located in the microstrip base On the two sides of the sheet, the back part is used as the metal grounding plate of the filter; there are two input/output ports, which are the first input/output port and the second input/output port, and the front part includes the first A uniform transmission line unit, a second uniform transmission line unit, a first parallel coupled feeder, a second parallel coupled feeder, a double stub loaded resonator and a dielectric plate; the first uniform transmission line unit and the second uniform transmission line unit are respectively located on the left and right sides of the front Both ends are on the same horizontal line, the first input/output port is connected to the first uniform transmission line unit, the second input/output port is connected to the second uniform transmission line unit; the first parallel coupling feeder and the second parallel coupling The feeders are connected through double-stub loaded resonators; the non-open end of the first parallel coupled feeder is connected to the first uniform transmission line unit, the non-open end of the second parallel coupled feeder is connected to the second uniform transmission line unit, and the dielectric plate passes through the ground via hole Connected to a grounded metal floor. the

Preferably, the dual-stub-loaded resonator is composed of two multi-mode resonators with open-circuit stubs and two multi-mode resonators with short-circuit stubs. the

Preferably, the electrical length of the two open branches relative to the center frequency of 6.85GHz is about 94.5°, and the electrical length of the two short-circuit branches relative to the center frequency of 6.85GHz is 42.5°. the

Preferably, the impedances of the stub sections and the transmission lines are the same. the

Further, the impedance is 130.5 ohms. the

Preferably, the via hole in the center of the short-circuit stub is connected to the metal ground plate through metal. the

Preferably, the microstrip substrate has a dielectric constant of 2.55 and a thickness of 0.8 mm. the

Preferably, the reverse part includes a first defective unit, a second defective unit and a grounded metal floor; the first defective unit and the second defective unit are formed by etching and removing corresponding structural shapes on the metal floor Air unit; the first defective ground unit is located under the first parallel coupled feeder, and the second defective ground unit is located under the second parallel coupled feeder; the first input/output port and the second input/output port are also connected to the grounded metal floor. the

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

1. Utilize the four modes of the dual-stub-loaded resonator to form a unified broadband, which can cover the ultra-wideband communication frequency band 3.1-10.6GHz. Among them, two odd modes and two even modes can be controlled independently, and it is easy to form a unified passband. the

2. By using two pairs of stubs (short-circuit stub and open-circuit stub) to load, a transmission zero point can be generated on both sides of the passband, so that the squareness is well improved. the

3. Both pairs of stubs (short-circuit stub and open-circuit stub) can generate transmission zeros in the upper stop band, which can well improve out-of-band suppression. the

4. By bending the two pairs of branches separately, the UWB filter is further miniaturized, with small size, low cost, more compact structure, and easier integration with other circuits. the

Description of drawings

Fig. 1 is the overall structural representation of the utility model UWB filter;

Fig. 2 is the front part structural representation of the utility model ultra-wideband filter;

Fig. 3 is the structural representation of the reverse part of the ultra-wideband filter of the present invention;

Fig. 4 is the electromagnetic simulation and test curve of the frequency response of the UWB filter with notch characteristics. the

Detailed ways

The utility model will be further described in detail below in conjunction with the embodiments and accompanying drawings, but the implementation of the utility model is not limited thereto. the

Example

As shown in Figure 1, it consists of a microstrip substrate, a front part, a back part and input/output ports; the front part and the back part are respectively located on two faces of the microstrip substrate, and the back part is The metal grounding plate of the filter; there are two input/output ports, namely input/output port 1 and input/output port 6. the

As shown in Figure 2, the front part includes: a first uniform transmission line unit 2, a second uniform transmission line unit 5, a first parallel coupled feeder 3, a second parallel coupled feeder 4, a double stub loaded resonator 7, a dielectric plate 8. The first uniform transmission line unit 2 and the second uniform transmission line unit 5 are respectively located at the left and right ends of the front and on the same horizontal line, and the first input/output port 1 is connected to the first uniform transmission line unit 2, The second input/output port 6 is connected to the second uniform transmission line unit 5; the first parallel coupled feeder 3 and the second parallel coupled feeder 4 are connected through a double stub loaded resonator 7; the non-open end of the first parallel coupled feeder 3 and The first uniform transmission line unit 2 is connected, the non-open end of the second parallel coupled feeder 4 is connected to the second uniform transmission line unit 5; the double-stub loaded resonator 7 is composed of two open-circuit stubs (the electrical length relative to the center frequency of 6.85 GHz is about 94.5°), two short-circuit stubs (about 42.5° with respect to the electrical length of the center frequency 6.85GHz) multimode resonator; the impedance of each branch and the transmission line is the same, both are 130.5 ohms; the via hole in the center of the short-circuit stub passes through the metal Connect to metal ground plane. The dielectric constant of the microstrip substrate is 2.55 and the thickness is 0.8mm. the

As shown in Figure 3, the reverse part includes: the first defective ground unit 9, the second defective ground unit 10, the ground via hole 11 and the grounded metal floor 12; the first defective ground unit 9, the second defective ground unit 10 All are air units formed by etching and removing corresponding structural shapes on the metal floor; the first defective ground unit 9 is located below the first parallel coupled feeder 3, and the second defective ground unit 10 is located below the second parallel coupled feeder 4; The first input/output port 1 and the second input/output port 6 are also connected to the grounded metal floor 12 . the

As shown in FIG. 4 , the frequency characteristics of this embodiment include: S21 (insertion loss) parameters, S11 (return loss) parameters, and group delay. The abscissa represents the frequency variable, the unit is GHz, and the left ordinate represents the amplitude variable, the unit is dB. The ordinate on the right is the group delay, and the unit is ns. As can be seen from Fig. 4, the 3dB bandwidth of the ultra-wideband filter of the present invention is 2.9-10.8GHz, the group delay of the frequency is less than 0.6ns, and the insertion loss of the upper stopband is greater than 20dB in the range of 18GHz. In this example, two shorted stubs and two open stubs are located on either side of a section of transmission line. The two groups of stubs can generate transmission zeros at the required frequency, thereby suppressing the spurious mode of the upper stop band and forming a wider stop band characteristic. By changing the electrical length of the two groups of branches, the mode of ultra-wideband can be controlled, thereby adjusting the bandwidth to form ultra-wideband characteristics of 3.1-10.6GHz. the

The above-described embodiment is a preferred embodiment of the present utility model, but the embodiment of the present utility model is not limited by the above-mentioned embodiment, and any other changes, modifications, and substitutions made without departing from the spirit and principles of the present utility model , combination, and simplification, all should be equivalent replacement methods, and are all included in the protection scope of the present utility model. the

Claims (8)

1. A kind of ultra-broadband filter based on double stub loaded resonator, comprising microstrip substrate, front part, back part and input\output port, it is characterized in that, described front part and back part are respectively positioned at described On both sides of the microstrip substrate, the opposite part is used as the grounded metal floor of the filter; there are two input/output ports, which are the first input/output port (1) and the second input/output port (6 ), the front part includes a first uniform transmission line unit (2), a second uniform transmission line unit (5), a first parallel coupled feeder (3), a second parallel coupled feeder (4), a double stub loaded resonator (7 ) and a dielectric plate (8); the first uniform transmission line unit (2) and the second uniform transmission line unit (5) are respectively located at the left and right ends of the front and on the same horizontal line, and the first input/output port (1) is connected to the first uniform transmission line unit (2), and the second input/output port (6) is connected to the second uniform transmission line unit (5); the first parallel coupled feeder (3) and the second parallel coupled feeder ( 4) Connected by double-twig loaded resonators (7); the non-open end of the first parallel coupled feeder (3) is connected with the first uniform transmission line unit (2), and the non-open end of the second parallel coupled feeder (4) is connected with the first uniform transmission line unit (2). The two uniform transmission line units (5) are connected to each other, and the dielectric plate (8) is connected to the grounded metal floor through the ground via hole (11). the 2. The ultra-wideband filter based on dual-stub loaded resonators according to claim 1, characterized in that, the dual-stub loaded resonator (7) consists of two open-circuit stub multimode resonators and two short-circuit stub of multimode resonators. the 3. The ultra-wideband filter based on dual-stub loaded resonators according to claim 2, wherein the electrical length of the two open-circuit stubs relative to the center frequency of 6.85 GHz is 94.5°, and the two short-circuit stubs are relative to The electrical length of the center frequency 6.85GHz is 42.5°. the 4. The ultra-wideband filter based on double-stub loaded resonators according to claim 2 or 3, characterized in that the impedances of each segment of stubs and transmission lines are the same. the 5. The ultra-wideband filter based on dual-stub loaded resonators according to claim 4, wherein the impedance is 130.5 ohms. the 6 . The ultra-wideband filter based on dual stub loaded resonators according to claim 4 , wherein the via hole in the center of the short-circuit stub is connected to the metal ground plate through metal. 7 . the 7. The ultra-wideband filter based on dual stub loaded resonators according to claim 1, wherein the microstrip substrate has a dielectric constant of 2.55 and a thickness of 0.8mm. the 8. The ultra-wideband filter based on double stub loaded resonators according to claim 1, characterized in that, the reverse part includes a first defective ground unit (9), a second defective ground unit (10) and a grounded metal floor ( 12); the first defective ground unit (9) and the second defective ground unit (10) are air units formed by etching and removing the corresponding structural shapes on the grounded metal floor (12); the first defective ground unit ( 9) Located below the first parallel coupled feeder (3), the second defective ground unit (10) located below the second parallel coupled feeder (4); the first input/output port (1), the second input/output port (6 ) is also connected to the grounded metal floor (12). the

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