CN108987864A - Centre frequency and complete adjustable 1/8th moulds substrate integral wave guide filter of bandwidth - Google Patents

Abstract

The present invention relates to centre frequency and complete adjustable 1/8th moulds substrate integral wave guide filters of bandwidth.The present invention is made of EMSIW filter single-layer medium plate, and the tuning of centre frequency and bandwidth is realized by load varactor.By loading stub on EMSIW chamber, resonance frequency can reduce, while by loading varactor in stub end come tuned frequency, the innovative frequency tuning mode for realizing SIW structure；Two EMSIW chambers are electrically coupled by marginal gap, and gap provides physical space for loading element, by loading varactor in marginal gap come the coefficient of coup between tuning cavity, realize the tuning of SIW fabric bandwidths.Requirement of the modern radio-frequency communication system for miniaturization is catered to by introducing EMSIW, and it is adjustable to solve the problems, such as that traditional cavity body filter is difficult to complete by external load tuned cell.

Description

One-eighth mode substrate integrated waveguide filter with fully adjustable center frequency and bandwidth

technical field

The invention belongs to the field of electronic information technology, and specifically relates to a one-eighth mode substrate integrated waveguide (EMSIW) filter with fully adjustable center frequency and bandwidth. Compact RF filter.

Background technique

In the era of rapid development of communication technology, the most widely used microwave device in the RF front-end is the filter, which can filter out interference signals outside the frequency band and ensure the performance of the receiver. With the continuous development of the communication industry, the spectrum resources that can be used are becoming more and more scarce, and the available frequency bands are also becoming more and more crowded. This phenomenon just highlights the important role of the filter. Its ability to separate useful signals becomes particularly important in the context of scarce spectrum resources. The performance of the filter directly determines the quality of the microwave signal processed by the RF front-end circuit. The advantages and disadvantages of wireless communication systems play an inestimable role.

There are several different mainstream communication standards in mobile communication, such as CDMA2000, WCDMA, TDD-LTE, FDD-LTE and future 5G standards. Usually, a wireless communication system requires a large number of filters, each filter has its own indicators and functions, and different filters are responsible for communication in different frequency bands. Therefore, if filters of different standards are used for frequency selection in each radio frequency front end, the size and complexity of the entire communication system will be greatly increased, and the cost will also be high. Although the multi-frequency structure can work at multiple frequency points, the crosstalk between adjacent frequency bands has always been an unsolvable problem. From this point of view, if the RF filter used can realize the reconfigurability of the center frequency and bandwidth, then the crosstalk problem of adjacent frequency bands and the coverage problem of multiple frequency bands can be effectively solved. In addition, if a radio frequency filter can meet the indicators of different requirements at the same time, then a very small number of reconfigurable radio frequency filters can be used to replace the original large number of fixed non-tunable filters. A sharp reduction in the number of filters can not only greatly reduce the volume and cost of the wireless communication system, but also simplify the design process of the entire wireless communication system circuit.

In the past 10 years, due to the advantages of low loss, high power handling, high performance, and high stability, traditional cavity resonators are still commonly used to design high-performance filters. However, this cavity resonator also has its obvious disadvantages, such as: large volume, fixed and non-adjustable, etc. In today's environment that requires equipment miniaturization and improved spectrum utilization, the disadvantages of cavity resonators are obviously magnified. So the traditional cavity resonator is not suitable for the design of our proposed reconfigurable RF filter.

The emerging substrate-integrated waveguide (SIW) technology represents a very promising candidate for modern wireless communication systems due to its advantages of low cost, low power consumption, relatively high Q, high power handling capability and high density integration , providing an attractive platform for microwave and millimeter wave applications. Compared with cavity filters, the volume of advanced SIW filters is significantly reduced; compared with microstrip line filters, SIW filters have the advantages of lower insertion loss and are suitable for higher frequency bands. SIW technology provides a new technology choice for reconfigurable RF filters. In addition, the SIW structure also has its unique advantages in the miniaturization of the filter. At present, according to the unique electromagnetic propagation characteristics of SIW, half-mode (HMSIW), quarter-mode (QMSIW) and one-eighth mode (mode) technologies have been developed. This miniaturization technique also maintains the same electromagnetic propagation characteristics as the full-mode SIW, reduces the size in half, and maintains good performance.

Reconfigurable RF filters are the future development direction of RF filters. The SIW structure has many advantages, and it has received more and more attention and applications in the design of reconfigurable filters. At present, whether it is to realize the adjustable center frequency, the bandwidth can be preset, the bandwidth can be reconfigured, the center frequency is fixed, and even the RF filter with dual passband frequency independently adjustable, there have been many research results, but at present, the center frequency and the frequency can be realized at the same time. There are relatively few research results on fully tunable bandwidth. Fully tunable center frequency and bandwidth filters can realize "tailor-made" communication services of various standards, which is the ultimate design goal of tunable filters. In today's increasingly crowded spectrum, many practical applications have certain requirements for bandwidth, and it is difficult to use tuned filters with uncontrolled bandwidth. There is an urgent need to study fully tunable filters with excellent performance in center frequency and bandwidth.

Contents of the invention

The purpose of the present invention is to provide a compact one-eighth mode substrate integrated waveguide (EMSIW) structure with fully adjustable center frequency and bandwidth band-pass filter for the deficiencies of the prior art.

According to the magnetic symmetry of the substrate integrated waveguide (SIW) cavity, the present invention cuts along the center of the SIW cavity in a "m" shape, takes one eighth of it, and forms a coupling design filter by two EMSIW cavities . EMSIW has similar performance to SIW, but only one-eighth of its size, which meets the miniaturization requirements of modern wireless communication systems. This filter mainly includes two EMSIW resonant cavities, short stubs, input and output feeders, coupling gaps, and varactor diodes for tuning center frequency, bandwidth and external Q value.

The filter is mainly composed of a dielectric board. The top layer of the dielectric board is laid with a top layer metal surface, input and output feeders and variable capacitance diodes; the bottom layer of the dielectric board is laid with a bottom metal surface.

The top metal surface of the filter includes two first and second metal surfaces with the same structure;

The electric wall edge of the first metal surface runs through a row of periodically distributed first metal pillars, and the first metal pillars penetrate the dielectric plate and the bottom metal surface; it is composed of the first metal surface, the first metal pillars and the bottom metal surface The first EMSIW structure;

The first stub line is set at the position with the strongest electric field on the first metal surface, the end of the first stub line is connected to the varactor diode C1 and the first metal patch, the center of the first metal patch runs through a third metal column, and The third metal column penetrates the dielectric plate and the bottom metal surface;

The input feeder is arranged on the virtual magnetic wall of the first EMSIW resonant cavity, and a varactor diode C2 is loaded in the middle of the input feeder;

The length of the first stub affects the resonant frequency of the first EMSIW cavity, the longer the first stub is, the smaller the resonant frequency of the first EMSIW cavity;

The size of the variable capacitance diode C1 is used to adjust the center frequency; the size of the variable capacitance diode C2 is used to adjust the external Q value.

The shortest distance t1 between the input feeder and the electrical wall of the first metal plane affects the external Q value.

The second EMSIW structure is the same as the first EMSIW structure, there is a gap between the two EMSIW resonant cavities, and the centers of the two EMSIW structures are symmetrically arranged and electrically coupled. A varactor diode C5 connected to two EMSIW resonators is loaded in the gap;

The second EMSIW structure is specifically composed of the second metal surface, the second metal pillar and the bottom metal surface. A row of periodically distributed second metal pillars runs through the electric wall of the second metal surface, and the second metal pillars penetrate the dielectric plate and the underlying metal surface;

The second stub line is set at the position with the strongest electric field on the second metal surface, the end of the second stub line is connected to the varactor diode C3 and the second metal patch, the center of the second metal patch runs through a fourth metal column, and The fourth metal column runs through the dielectric plate and the bottom metal surface;

The output feeder is arranged on the virtual magnetic wall of the second EMSIW resonant cavity, and a varactor diode C4 is loaded in the middle of the output feeder;

The length of the second stub affects the resonant frequency of the second EMSIW cavity, the longer the second stub is, the smaller the resonant frequency of the second EMSIW cavity;

The size of the variable capacitance diode C3 is used to adjust the center frequency, and the size of the variable capacitance diode C4 is used to adjust the external Q value.

The size of the varactor diode C5 is used to adjust the coupling coefficient between the two EMSIW resonant cavities.

The shortest distance t3 between the output feeder and the electric wall of the second metal plane influences the external Q value.

The filter adopts PCB board technology.

The two EMSIW cavities of the bandpass filter are the same, and the varactors C1 and C3 used to adjust the center frequency can be controlled with the same voltage, and the filter can be adjusted by applying voltage to the varactors C1 and C3 center frequency; by applying a voltage to the varactor diode C5, the coupling coefficient of the filter can be adjusted and the bandwidth of the filter can be changed; the varactor diodes C2 and C4 used to adjust the external coupling can be controlled with the same voltage, by giving the varactor Diodes C2 and C4 apply a voltage that adjusts the external Q of the filter.

The invention innovatively utilizes the EMSIW structure to design the adjustable filter, which solves the problem that the cavity filter is difficult to load tuning elements to realize center frequency and bandwidth tuning, and introduces the EMSIW structure, which greatly realizes the miniaturization of the filter. The present invention loads stubs and varactor diodes in the EMSIW cavity, and innovatively realizes the frequency tuning mode of the SIW structure; two EMSIW cavities are electrically coupled at the edge, and a varactor diode is loaded between the coupling gaps of the EMSIW cavity to tune between the cavities The coupling coefficient innovatively realizes the bandwidth tuning method of the SIW structure; at the same time, the tuning of the external Q value of the filter can be realized by loading a varactor diode on the input and output feeder lines.

The position of the strongest electric field in the EMSIW cavity of the present invention is loaded with a stub, and compared with an unloaded stub, the resonant frequency can be significantly reduced, and the miniaturization of the filter can be further realized.

The filter of the present invention has a compact structure, provides a new idea for the miniaturization of the adjustable cavity filter, has novel central frequency and bandwidth tuning methods, a large bandwidth tuning range, fewer tuning elements, and lower manufacturing process requirements.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 (a), (b) are the top layer schematic diagram and the bottom layer schematic diagram of the present invention respectively;

Figure 3 (a), (b) is the S-parameter simulation diagram of the adjustable filter bandwidth tuning at each frequency point;

Among them, 1 is the first triangular metal surface, 2 is the second triangular metal surface, 3 is the input feeder, 4 is the output feeder, 5 is the first stub, 6 is the second stub, and 7 is the first metal Patch, 8 is the second metal patch, 9 is the first metal post, 10 is the second metal post, 11 is the third metal post, 12 is the fourth metal post, 13 is the bottom metal surface, d is the metal post diameter, P is the distance between adjacent metal columns, and h is the thickness of the dielectric plate.

Detailed ways

The present invention will be further described below in conjunction with accompanying drawing

As shown in Figures 1 and 2, the EMSIW tunable filter of this invention consists of a piece of Rogers with a dielectric constant of 10.2 and a thickness h.

The top layer of the dielectric board mainly includes the first and second triangular metal surfaces 1 and 2, the input and output feeders 3 and 4, the first and second stub lines 5 and 6, the first and second metal stickers Sheets 7, 8 and varactors C1-C5. A row of periodically distributed first metal columns 9 runs through the edge of the first right-angled side 14 of the first triangular metal surface 1, and the first metal columns 9 penetrate the dielectric plate and the underlying metal surface. The first triangular metal surface 1 , the first metal pillar 9 and the underlying metal surface 13 constitute the first EMSIW structure, the end of the second right-angled side 15 of the first triangular metal surface 1 is connected to a section of the first stub 5, the length of the first stub 5 It will affect the resonance frequency of the first EMSIW cavity. The longer the first stub 5, the lower the resonance frequency of the first EMSIW cavity. The end of the first stub 5 is connected to the varactor diode C1 and the first metal patch 7. The center of the first metal patch 7 runs through a third metal post 11, and the third metal post 11 runs through the dielectric plate and the bottom metal surface 13. Adjusting the size of the varactor diode C1 is used to adjust the first EMSIW cavity The resonant frequency realizes the electrical adjustment of the center frequency. The input feeder 3 is placed on the side of the second right-angled side 15, and the shortest distance t1 between the input feeder 3 and the first right-angled side 14 of the first triangular metal surface 1 can be adjusted. External Q value, the middle of the input feeder 3 is loaded with a varactor diode C2, adjusting the size of the varactor diode C2 is used to tune the external Q value, and realize the electrical adjustment of the external Q value; the first right angle of the second triangular metal surface 2 A row of periodically distributed second metal pillars 10 runs through the edge of the edge 16. At the same time, the second metal pillars 10 penetrate the dielectric plate, the bottom metal surface 13, the second triangular metal surface 2, the second metal pillar 10 and the bottom metal surface 13 forms the second EMSIW structure, the end of the second right-angled side 17 of the second triangular metal surface 2 is connected to a second stub 6, the length of the second stub 6 will affect the resonance frequency of the second EMSIW cavity , the longer the second stub 6, the lower the resonance frequency of the second EMSIW cavity, the end of the second stub 6 is connected to the varactor diode C3 and the second metal patch 8, and the center of the second metal patch 8 runs through A fourth metal column 12, and the fourth metal column 12 penetrates the dielectric plate and the bottom metal surface 13, and adjusting the size of the varactor diode C3 is used to adjust the resonant frequency of the second EMSIW cavity to realize the electrical adjustment of the center frequency, The output feeder is placed on the side of the second right-angled side 17, the shortest distance t3 between the output feeder 4 and the first right-angled side 16 of the second triangular metal surface 2 can adjust the external Q value, and the middle load of the output feeder 4 is changed. Capacitance diode C4, adjusting the size of the varactor diode C4 is used to tune the external Q value to realize the electrical adjustment of the external Q value.

As shown in Figures 1 and 2, the first and second triangular metal surfaces 1 and 2 are placed opposite each other with a gap g along their hypotenuses. The size of the gap g affects the coupling coefficient of the filter, and at the same time the gap g provides the loading element physical space. The middle of the hypotenuses of the first and second triangular metal surfaces 1 and 2 is loaded with a varactor diode C5. Adjusting the size of the varactor diode C5 is used to tune the coupling coefficient of the filter to realize the electrical adjustment of the coupling coefficient.

Table 1 shows the specific values of the structural parameters of the filter.

Table 1 Filter structure design parameters, unit: mm

W1/W2/W3 L1/L2/L3/L4 t1/t2/t3/t4 P d g h 0.58/1.5/0.5 7.4/8.7/1.2/2 3.5/5.35/3.5/5.35 0.8 0.6 1.4 0.635

By adjusting the applied voltage of varactor diodes C1 and C3, the filter realizes the frequency-selective tuning range of the center frequency from 2.17GHz to 2.72GHz. At the same time, by adjusting the applied voltage of varactor diodes C2, C4 and C5, the The bandwidth of each frequency point within the center frequency tuning range is tuned. The processed filter is tuned with a 3dB bandwidth of 140MHz to 208MHz at 2.17GHz and a 3dB bandwidth of 231MHz to 355MHz at 2.45GHz by using a network vector analyzer. 3dB bandwidth tuning from 314MHz to 435MHz at 2.72GHz.

Accompanying drawing 3 as can be seen, the present invention has preferably realized adjustable bandwidth and center frequency, has wider center frequency and bandwidth tuning range, in the whole tuning range, insertion loss (S21) is 1.59-4dB, echo The loss (S11) is greater than 10dB, and the adjustable performance is good.

The invention innovatively utilizes the EMSIW structure to design an adjustable filter, realizes full tunability of the center frequency and bandwidth of the filter, and solves the problem that it is difficult to load a tuning element on a cavity filter to realize center frequency and bandwidth tuning. The introduction of the EMSIW loaded stub structure greatly realizes the miniaturization of the filter, and the tunable filter of the present invention requires few tuning elements and has relatively low manufacturing process requirements.

Claims (9)

1. centre frequency and complete adjustable 1/8th moulds substrate integral wave guide filter of bandwidth, it is characterised in that main includes being situated between Top-level metallic face, input and output feeder line and the varactor that scutum, two EMSIW resonant cavities and dielectric-slab top layer are laid with； The underlying metal face that dielectric-slab bottom is laid with；

The top-level metallic face includes identical first and second metal covering of two block structures；

The electric wall edge of first metal covering runs through several first metal columns for having row's periodic distribution, while first metal column Through dielectric-slab, underlying metal face；First EMSIW resonance is constituted by the first metal covering, the first metal column and underlying metal face Cavity configuration；

The electric field of first metal covering most strong position be arranged the first stub, the first stub end connection varactor C1 and First metal patch, third metal column is run through at the center of the first metal patch, while the third metal column runs through dielectric-slab, bottom Metal covering；

Incoming feeder is arranged on the virtual magnetic wall of first EMSIW resonant cavity, and varactor is loaded among incoming feeder C2；

Second EMSIW cavity resonator structure is identical as first EMSIW cavity resonator structure, there are gap between two EMSIW resonant cavities, And two EMSIW structure be electrically coupled；The varactor C5 of two EMSIW resonant cavities of connection is loaded in gap；

Second EMSIW cavity resonator structure is specifically made of the second metal covering, the second metal column and underlying metal face；Second metal The electric wall in face runs through several second metal columns for having row's periodic distribution, while second metal column runs through dielectric-slab, bottom Metal covering；

The electric field of second metal covering most strong position be arranged the second stub, the second stub end connection varactor C3 and Second metal patch, the 4th metal column is run through at the center of the second metal patch, and the 4th metal column runs through dielectric-slab, underlying metal Face；

Output feeder is arranged on the virtual magnetic wall of the 2nd EMSIW resonant cavity, and varactor C4 is loaded among output feeder.

2. centre frequency as described in claim 1 and complete adjustable 1/8th moulds substrate integral wave guide filter of bandwidth, It is characterized in that the resonance frequency of first EMSIW chamber of effect length of the first stub.

3. centre frequency as described in claim 1 and complete adjustable 1/8th moulds substrate integral wave guide filter of bandwidth, It is characterized in that the size of varactor C1 for adjusting centre frequency；The size of varactor C2 is for adjusting External Q.

4. centre frequency as described in claim 1 and complete adjustable 1/8th moulds substrate integral wave guide filter of bandwidth, It is characterized in that the shortest distance t1 between incoming feeder and the electric wall of the first metal covering influences External Q.

5. centre frequency as described in claim 1 and complete adjustable 1/8th moulds substrate integral wave guide filter of bandwidth, It is characterized in that the resonance frequency of second EMSIW chamber of effect length of the second stub.

6. centre frequency as described in claim 1 and complete adjustable 1/8th moulds substrate integral wave guide filter of bandwidth, The size of varactor C3 is characterized in that for adjusting centre frequency, the size of varactor C4 is for adjusting External Q.

7. centre frequency as described in claim 1 and complete adjustable 1/8th moulds substrate integral wave guide filter of bandwidth, It is characterized in that the size of varactor C5 is used to adjust the coefficient of coup between two EMSIW resonant cavities.

8. centre frequency as described in claim 1 and complete adjustable 1/8th moulds substrate integral wave guide filter of bandwidth, It is characterized in that the shortest distance t3 between output feeder and the electric wall of the second metal covering influences External Q.

9. centre frequency as described in claim 1 and complete adjustable 1/8th moulds substrate integral wave guide filter of bandwidth, It is characterized in that the filter uses pcb board technique.