CN114374063B - Miniaturized patch type balanced band-pass filter with high common-mode rejection - Google Patents
Miniaturized patch type balanced band-pass filter with high common-mode rejection Download PDFInfo
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- CN114374063B CN114374063B CN202111505532.7A CN202111505532A CN114374063B CN 114374063 B CN114374063 B CN 114374063B CN 202111505532 A CN202111505532 A CN 202111505532A CN 114374063 B CN114374063 B CN 114374063B
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Abstract
A miniaturized patch type balanced band-pass filter with high common-mode rejection comprises a dielectric substrate, wherein two semicircular patch resonators with the same structure are symmetrically arranged on the dielectric substrate, the two semicircular patch resonators are mutually coupled through first gaps which are arranged at intervals, each semicircular patch resonator is provided with a groove, a connected feed slot line is arranged in each groove, and the feed slot line and the vertical wall of the groove of each semicircular patch resonator form a symmetrical second gap; the invention has simple structure and novel and unique design, effectively solves the problems of the common mode rejection characteristic of the balanced filter and the poor frequency selectivity of the differential mode passband, and has remarkable social and economic benefits.
Description
Technical Field
The invention relates to the technical field of communication, in particular to a miniaturized patch type balanced band-pass filter with high common-mode rejection.
Background
Filters play an essential role in communication devices as a frequency selective device. With the rapid development of wireless communication technology, the requirements for the quality, capacity, speed and the like of information transmission in a communication system are increasing day by day. Meanwhile, the electromagnetic environment in which wireless communication systems operate is becoming more and more complex, and people put higher demands on the rate, accuracy and real-time performance of information transmission. In order to ensure the stability of the useful signal during the transmission process of the communication system, it is necessary to effectively suppress or eliminate the electromagnetic interference and noise occurring in the communication device, i.e. the communication device is required to have a strong anti-noise capability. However, due to structural defects, the conventional single-ended input/output filter cannot meet the requirement, and compared with the conventional filter, the balanced filter can achieve a frequency selection function and can also suppress common-mode noise signals, that is, has the capability of resisting electromagnetic interference, improving the transmission efficiency of a transmitter in a system and reducing the noise of a receiver. The better the common mode rejection of the balanced filter, the stronger its immunity to noise and electromagnetic interference. In addition, the patch filter has the advantages of small conductor loss, light weight, low cost, high power tolerance, easy processing and the like, and for the patch balance filter, the patch balance filter has a filtering function, and can improve the power tolerance and the anti-electromagnetic interference capability of a communication system, so that signals can be transmitted in the system more stably and accurately, and the performance of the filter is greatly improved. In recent years, various structures have been proposed for microstrip balanced filters, however, balanced filters designed by adopting a patch structure are few, and the common-mode rejection effect and the differential-mode rejection-band rejection effect are not particularly good. Therefore, designing a miniaturized patch type balanced band-pass filter with high common-mode rejection for improving the quality and stability of information transmission in a communication system has become a technical problem to be solved seriously.
Disclosure of Invention
In view of the above, to overcome the defects in the prior art, the present invention provides a miniaturized patch type balanced band-pass filter with high common-mode rejection, which can effectively solve the problem of poor common-mode rejection characteristics and poor frequency selectivity of the differential-mode passband of the balanced filter.
In order to achieve the purpose, the technical scheme includes that the miniaturized patch type balanced band-pass filter with high common-mode rejection comprises a dielectric substrate, two semicircular patch resonators with the same structure are symmetrically installed on the dielectric substrate, the two semicircular patch resonators are mutually coupled through first gaps which are arranged at intervals, a groove is formed in each semicircular patch resonator, a feed slot line connected with the feed slot line is installed in each groove, and the feed slot line and the vertical wall of the groove of each semicircular patch resonator form a symmetrical second gap.
The invention has simple structure and novel and unique design, effectively solves the problems of poor common mode rejection characteristic of the balanced filter and poor frequency selectivity of the differential mode passband, and has remarkable social and economic benefits.
Drawings
Fig. 1 is a schematic diagram of the structures of a conventional circular patch resonator and a semicircular patch resonator (where a is the circular patch resonator and b is the semicircular patch resonator).
Fig. 2 is a graph comparing the frequency responses of the circular and semicircular patch resonators of fig. 1 at a radius of 8mm according to the present invention (wherein a solid line indicates the frequency response curve of the semicircular patch resonator and a dotted line indicates the frequency response curve of the circular patch resonator).
Fig. 3 is a schematic structural diagram of the present invention.
Fig. 4 is a coupling topology of the present invention.
FIG. 5 shows the coupling coefficient and resonator spacing under differential mode excitationgGraph of the relationship of (c).
FIG. 6 is a graph of external Q-factor versus differential mode excitation for the present inventionL 1 Andw 1 graph of the change in (c).
FIG. 7 illustrates the patch type balanced band-pass filter of the present invention at different spacingsgFrequency response curve of (wherein: S) dd 11 For return loss, S dd 21 As insertion loss).
FIG. 8 shows the embedding lengths of the patch-type balanced band-pass filter in different feeder linesL 1 Frequency response curve of (wherein: S) dd 11 For return loss, S dd 21 As insertion loss).
FIG. 9 is a simulation and test frequency response curve diagram of the SMD balanced band-pass filter (S) dd 11 For differential mode return loss, S dd 21 For differential mode insertion loss, S cc 21 Common mode insertion loss).
Detailed Description
The following detailed description of the embodiments of the invention is provided in connection with the accompanying drawings and the detailed description.
The small patch type balanced band-pass filter with high common mode rejection comprises a dielectric substrate, wherein two semicircular patch resonators 2 with the same structure are symmetrically arranged on the dielectric substrate 1, the two semicircular patch resonators 2 are mutually coupled through first gaps 5 which are arranged at intervals, a groove is arranged on each semicircular patch resonator 2, a feed slot line 3 which is connected with each other is arranged in each groove, and the feed slot line 3 and the vertical walls of the grooves of the semicircular patch resonators 2 form symmetrical second gaps 4.
In order to ensure better implementation effect, 4 symmetrical feeder slot lines 3 are arranged, and 2 symmetrical feeder slot lines 3 are connected to each patch resonator 2.
The feed slot line 3 is strip-shaped, and the width of the feed slot line 3 is the same as that of a second gap 4 between two side walls of the groove of the semicircular patch resonator 2.
The radius a of the patch resonator 2 is 8mm.
The width g of the first gap 5 is 0.3mm, the width w1 of the second gap 4 is 1.3mm, and the length L1 of the feed slot line 3 embedded in the groove of the patch resonator 2 is 3.98mm.
The dielectric substrate 1 is an FR4 dielectric substrate with the thickness of 0.5mm, the relative dielectric constant of 4.4 and the loss tangent of 0.025.
The invention provides a novel miniaturized patch balanced band-pass filter with high common-mode rejection based on a semicircular patch resonator. By analyzing the resonance characteristics of the circular and semicircular patch resonators and comparing their frequency responses, it was found that the main mode resonance frequencies of the two structures were substantially the same. Therefore, the invention designs the filter by adopting the semicircular resonator, which is beneficial to the miniaturization of the device. In addition, the resonance characteristic of the semicircular patch resonator is analyzed, and the difference mode resonance frequency and the common mode resonance frequency are far different, so that the structure has the frequency dispersion characteristic and is favorable for realizing higher common mode rejection degree. A balance filter is designed by adopting a semicircular patch resonator, and the common mode rejection characteristic of the balance filter and the frequency selectivity of a differential mode passband are improved under the condition of not adding additional components.
The invention designs a balance band-pass filter prototype by two identical semicircular patch resonators through slot coupling. The external coupling adopts an embedded slot line feed structure, and the structure aims to enhance the impedance matching under the differential mode band pass. A higher degree of common mode rejection is achieved in the differential pass band because the common mode signal is not excited. The results show that the filter has good differential mode frequency response, and the experimental data are as follows.
As shown in fig. 1 and 2, fig. 1 is a schematic structural diagram of a conventional circular and semicircular patch resonator, and a radius thereof is denoted by a. Fig. 2 is a graph comparing frequency responses of a circular patch resonator and a semicircular patch resonator at a radius a of 8mm, a solid line indicating a frequency response curve of the semicircular patch resonator, and a dotted line indicating a frequency response curve of the circular patch resonator. It can be seen from the figure that the main mode resonance frequencies of the circular and semicircular patch resonators are almost the same, and therefore, the filter is designed by using the semicircular patch resonator instead of the conventional circular patch resonator, not only can the miniaturization of the circuit size be realized, but also the coupling between the resonators is facilitated.
Fig. 3 is a schematic structural diagram of a miniaturized patch-type balanced band-pass filter with high common-mode rejection according to the present invention. The input and output are connected to the patch resonators by embedded slot line feeder lines.
Fig. 4 is a coupling topology diagram of a patch type balanced band-pass filter. S and L represent source and load, respectively, R1 and R2 represent two semicircular patch resonators, m 12 Representing the coupling coefficient, Q, between two resonators e I Representing an external quality parameter.
FIG. 5 shows the coupling coefficient m under differential mode excitation 12 Graph with resonator pitch g. The coupling coefficient between the two resonators is controlled by the spacing g, i.e. the width of the first slot 5, from fig. 5 it can be seen that the coupling coefficient m increases when the spacing g increases 12 A downward trend is exhibited. By optimizing the resonators, a coupling gap g of 0.3mm between the two resonators is obtained.
FIG. 6 is a graph showing the external figure of merit Q as a function of embedded feed line size (L1 and w 1) under differential mode excitation. It can be seen that Q gradually increases with increasing L1, while Q gradually decreases with decreasing w 1. The parameters L1 and w1 can be obtained to mainly control the external quality factor Q of the filter, so that the impedance matching of the filter is realized. Therefore, by adjusting the length L1 and the width w1 of the insertion slot line, the external quality factor Q of the differential-mode passband can be controlled, thereby producing a good filter passband. The finally obtained parameter values may be determined as: l1=3.95mm and w1=1.3mm.
Fig. 7 shows frequency response curves of the patch type balanced band-pass filter at different pitches g. From fig. 7, it can be seen that the bandwidth of the differential-mode passband of the filter gradually narrows as the distance g increases, and at the same time, due to the influence of source-load coupling, a transmission zero is introduced to the right side of the passband, thereby improving the selectivity of the differential-mode passband. Therefore, as can be derived from fig. 5, the bandwidth of the passband can be controlled by adjusting the magnitude of the coupling coefficient.
Fig. 8 shows a frequency response curve of the patch type balanced band-pass filter under different feeder line embedding lengths L1, and it can be seen from fig. 8 that the center frequency of the filter can be effectively controlled by changing the length L1, which is beneficial to realizing circuit miniaturization.
The overall size of the filter is 16.3mm x 16.3mm (excluding the feeder slot line portion, i.e., the circumscribed square size of the 2 semicircular patch resonators), i.e., 0.5 λ g x 0.5 λ g, where λ g is the guided wavelength that balances the center frequency of the differential mode passband of the filter.
The microstrip feeder used by the filter is 0.96mm of microstrip feeder with 50 omega impedance.
Fig. 9 is a graph showing simulation and test frequency response of the patch type balanced band-pass filter. In the figure, the solid line is a simulation curve, and the dotted line is a test curve. Wherein S is dd 11 For differential mode return loss, S dd 21 For differential mode insertion loss, S cc 21 Common mode insertion loss (common mode rejection). When the central frequency of the filter is 5.25 GHz, the relative bandwidth is 12.5%, the differential mode return loss is about 20dB, the differential mode insertion loss is 1.89dB, the common mode rejection in the differential mode passband reaches about 40dB, and the FBW = BW/f is calculated according to the relative bandwidth 0 (where BW is the 3dB bandwidth of the passband, f 0 Is the center frequency) it can be concluded that the relative bandwidth of the common mode rejection is 181% below 20 dB.
From the above, the miniaturized patch balance filter with high common mode rejection of the invention has the advantages of simple structure, novel and unique design, easy production and manufacture, low cost and small loss, and compared with the prior art, the miniaturized patch balance filter with high common mode rejection has the following advantages:
(1) The realized filter has better characteristics, effectively reduces the size of the filter, has miniaturized circuit and improves the quality and stability of information transmission in a high-pass communication system;
(2) The wide-range high-power-consumption differential mode broadband wireless sensor network has high common-mode rejection degree and wide common-mode rejection bandwidth, is suitable for WiFi,5G and other applications, is wide in application range, return loss in a differential mode passband is superior to 20dB, common-mode rejection in the differential mode passband reaches about 40dB, relative bandwidth of common-mode rejection below 20dB reaches 181%, the common-mode rejection bandwidth is wide, and remarkable social and economic benefits are achieved.
Claims (4)
1. A miniaturized surface-mounted balanced band-pass filter with high common-mode rejection comprises a dielectric substrate and is characterized in that two semicircular surface-mounted resonators (2) with the same structure are symmetrically arranged on the dielectric substrate (1), the two semicircular surface-mounted resonators (2) are mutually coupled through first gaps (5) which are alternately opened, a groove is formed in each semicircular surface-mounted resonator (2), a feed slot line (3) which is connected with the feed slot line is arranged in each groove, and the feed slot line (3) and the vertical wall of the groove of each semicircular surface-mounted resonator (2) form a symmetrical second gap (4); the feed slot line (3) is provided with 4 mutually symmetrical feed slot lines, and each patch resonator (2) is connected with 2 symmetrical feed slot lines (3); the feed slot line (3) is long, and the width of the feed slot line (3) is the same as that of a second gap (4) between two side walls of the groove of the semicircular patch resonator (2).
2. A high common-mode rejection, miniaturized patch-balanced bandpass filter according to claim 1, characterized in that the radius a of the patch resonator (2) is 8mm.
3. A high common-mode rejection miniaturized patch-balanced bandpass filter according to claim 1, characterized in that the width g of the first slot (5) is 0.3mm, the width w1 of the second slot (4) is 1.3mm, and the length L1 of the feed slot line (3) embedded in the groove of the patch resonator (2) is 3.98mm.
4. A miniaturized patch-type balanced band-pass filter with high common-mode rejection according to claim 1, characterized in that the dielectric substrate (1) is an FR4 dielectric substrate with a thickness of 0.5mm, a relative dielectric constant of 4.4 and a loss tangent of 0.025.
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| CN112072224A (en) * | 2020-09-08 | 2020-12-11 | 中国人民解放军战略支援部队信息工程大学 | Balanced band-pass filter based on substrate integrated waveguide |
| CN113708030A (en) * | 2021-08-19 | 2021-11-26 | 西安电子科技大学 | Balance ultra-wideband band-pass filter based on multimode slot line resonator |
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| CN103199323B (en) * | 2013-03-29 | 2015-04-01 | 南通大学 | Dual-layer dual-mode and dual-passband band-pass filter |
| CN106159393A (en) * | 2015-04-08 | 2016-11-23 | 中兴通讯股份有限公司 | A kind of wave filter |
| CN113381141B (en) * | 2021-05-19 | 2023-02-28 | 南京智能高端装备产业研究院有限公司 | Double-passband balance power division filter adopting double-layer circular patch |
| CN113328223B (en) * | 2021-06-29 | 2022-08-30 | 展讯通信（上海）有限公司 | Third-order band-pass filter |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112072224A (en) * | 2020-09-08 | 2020-12-11 | 中国人民解放军战略支援部队信息工程大学 | Balanced band-pass filter based on substrate integrated waveguide |
| CN113708030A (en) * | 2021-08-19 | 2021-11-26 | 西安电子科技大学 | Balance ultra-wideband band-pass filter based on multimode slot line resonator |
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