A High-Selectivity Filtering Antenna Employing a Slotted Microstrip Patch

Abstract

The present invention relates to a high-selectivity filtering antenna using a slotted microstrip patch, which includes a TE<subgt;101< / subgt> mode substrate integrated waveguide resonator, an upper dielectric substrate, and a slotted TM<subgt;10 mode microstrip patch stacked from bottom to top. The slotted microstrip patch is coupled and fed through the TE<subgt;101 mode substrate integrated waveguide cavity. By opening a pair of long slots on the microstrip patch, the present invention introduces radiation zeros in the upper stopband without adding an additional filtering circuit, obtaining better filtering performance, making the proposed filtering antenna have high frequency selectivity, and compensating for the disadvantage that the substrate integrated waveguide has poor suppression level outside the high frequency band due to its many modes. The simulation results show that the proposed slotted patch filtering antenna has a good impedance bandwidth (|S<subgt;11|< -10 dB) of 2.9%, the radiation zero is located at 10.86 GHz, the peak gain in the band is 6.5 dBi, and the antenna gain is flat in the passband.

Description

Technical Field

[0001] The present invention belongs to the technical field of radio frequency communication, and relates to a highly selective filtering antenna using a slotted microstrip patch. Background Art

[0002] In a wireless communication system, the physical space of a radio frequency front end composed of various microwave components is becoming increasingly limited. As a frequency selection element, a filter is widely used in a microwave radio frequency front end to suppress harmonic or image frequency interference. When an antenna and a filter are separately designed as adjacent components, a standard 50-ohm transmission line is required for transition, which will not only reduce the system performance, increase the circuit area, but also introduce additional losses and loading effects. In the past decade, a new component called a filtering antenna has been proposed and immediately attracted great interest from scholars. Such components have both filtering and radiation functions, meeting the development trend of high functionality and high integration in the radio frequency front end.

[0003] The mainstream design methods of filtering antennas can be mainly divided into three categories. The first method is to separately design a filter and an antenna and then directly connect them together. In this case, the design integration level is low, and the filtering response of the filtering antenna is determined by the filter. The second method is a variation of the first method. The antenna serves as both the last-stage resonator of the filter and the radiator, but to further improve the out-of-band rejection level, it is often necessary to add an additional resonator to achieve cross-coupling to introduce radiation zeros. The third method is to introduce a specific structure into the antenna radiator to achieve a band-pass response of the gain, making the antenna have a filtering function and generate radiation zeros. However, the gain curve based on this method cannot be well predicted and controlled.

[0004] Substrate integrated waveguide has the advantages of low loss, low cost, high quality factor, and easy integration with other planar circuits, and is considered a promising candidate device in future high-integrated circuits. However, due to the high-pass characteristic of the substrate integrated waveguide itself and the large number of modes in the resonator cavity, harmonics are easily generated at high frequencies when constructing a filtering antenna. Therefore, the high-frequency out-of-band rejection level of the filtering antenna based on the substrate integrated waveguide needs to be improved. Radiation zeros are often used to achieve a sharp roll-off of the gain response of the filtering antenna. Radiation zeros can be introduced by introducing patch stacking, shorting pins, metasurfaces, etc., but such methods often lead to a large profile and a complex multi-layer structure. The method of introducing radiation zeros by opening a long slot on the patch has the advantages of simple structure, low cost, and no increase in the number of layers. At the same time, the filtering antenna designed by this method can maintain the original radiation performance of the microstrip patch, and the radiation zeros can be flexibly controlled according to the size of the slot. Summary of the Invention

[0005] The object of the present invention is to solve the deficiencies in the above-mentioned prior art, and propose a high-selectivity filtering antenna using a slotted microstrip patch, which obtains a stable filtering response without introducing an additional filtering structure, improves the original filtering ability of the filtering antenna, and makes the filtering performance better.

[0006] To achieve the object of the present invention, the high-selectivity filtering antenna using a slotted microstrip patch provided by the present invention is characterized in that it includes a TE 101 mode substrate integrated waveguide resonator, an upper dielectric substrate, and a TM 10 mode microstrip patch, which are stacked from bottom to top; the TE 101 mode substrate integrated waveguide resonator is composed of an upper metal floor, a lower dielectric substrate, a lower metal floor, and a silver-plated slot; the TM 10 mode microstrip patch and the upper dielectric substrate form a TM 10 mode microstrip patch resonator; the upper metal floor is provided with a coupling slot at a place where the magnetic field of the TE 101 mode substrate integrated waveguide resonator is stronger, and the TM 10 mode microstrip patch is arranged above the coupling slot, and is characterized in that: the TM 10 mode microstrip patch is provided with a pair of symmetric long slots along the X direction, and the long slots are distributed on both sides of the projection of the coupling slot on the TM 10 mode microstrip patch.

[0007] This filtering antenna uses the traditional fitting method for designing filters, regarding the antenna as both a radiator and the last-stage resonator of the filter. The gain curve of the antenna is almost the same as the filtering response of the reference filter. At the same time, by means of opening a pair of long slots in the microstrip patch, a high-frequency radiation zero point is obtained without adding an additional filtering circuit and without increasing the number of circuit layers, compensating for the disadvantage of the poor out-of-band suppression level of the substrate integrated waveguide itself due to its many modes. By integrating the design methods of the two filtering antennas, a stable filtering response is obtained without introducing an additional filtering structure, improving the original filtering ability of the filtering antenna and making the filtering performance better.

[0008] In addition, the present invention also proposes a design method for a high-selectivity filtering antenna using a slotted microstrip patch, which is characterized by including the following steps:

[0009] Step 1: Calculate the low-pass prototype lumped parameters according to the performance indexes required by the filtering antenna, and calculate the coupling coefficient K, the external quality factor Q es of the input port, and the radiation quality factor Q r ;

[0010] Step 2: Establish a model of the high-selectivity filtering antenna using a slotted microstrip patch as described in claim 1 according to the parameters determined in step 1, and adjust the first-stage TE101 The width w1 and length l1 of the coupling slot between the mold substrate integrated waveguide resonator and the second-stage TM 10 mode slotted microstrip patch resonator are such that the coupling between the first-stage TE 101 mode substrate integrated waveguide resonator and the second-stage TM 10 mode slotted microstrip patch resonator meets the design requirements;

[0011] Step 3. Adjust the width w 101 of the slots opened on both sides of the input feeder of the first-stage TE g mode substrate integrated waveguide resonator and the length l g , so that the external quality factor Q es of the input port (S) obtained by calculation in Step 1 is satisfied;

[0012] Step 4. Adjust the side length l c of the microstrip patch resonator and the relative dielectric constant of the upper dielectric substrate (2) so that the radiation quality factor Q r of the slotted microstrip patch resonator is equal to the external quality factor Q es of the input port;

[0013] Step 5. Adjust the length, width of the long slot of the microstrip patch and the distance between them to introduce a radiation zero point in the upper stopband. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be further described below in conjunction with the accompanying drawings;

[0015] Figure 1 is a three-dimensional view of the slotted microstrip patch filter antenna of the present invention.

[0016] Figure 2 is a top view of the slotted microstrip patch filter antenna of the present invention.

[0017] Figure 3 is the extraction curve of the external quality factor Q es and the coupling coefficient K of the slotted microstrip patch filter antenna of the present invention.

[0018] Figure 4 is the parameter scan of the radiation zero point with respect to the long slot l s when other parameters of the slotted microstrip patch filter antenna of the present invention are fixed.

[0019] Figure 5 is a comparison chart of the simulation reflection coefficient (S 11 ) and the gain curve of the slotless / slotted microstrip patch filter antenna.

[0020] Figure 6These are the simulated radiation E-plane and H-plane patterns of the slotted microstrip patch filtering antenna of the present invention at the frequency points of 10.14 GHz and 10.34 GHz.

[0021] The reference numerals in the figure are illustrated as follows: 1 - microstrip patch; 2 - upper dielectric substrate; 3 - upper metal ground; 4 - lower dielectric substrate; 5 - lower metal ground; 6 - long slot, 7 - coupling slot; 8 - silver-plated slot, 9 - breakpoint, 10 - input feeder. Detailed implementation manners

[0022] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0023] Figure 1 and Figure 2 respectively show the three-dimensional and planar geometric structures of the slotted microstrip patch filtering antenna coupled and fed by a TE 101 mode substrate integrated waveguide resonator, including a TE 101 mode substrate integrated waveguide resonator, an upper dielectric substrate 2, and a TM 10 mode microstrip patch 1 with a long slot 6 stacked from bottom to top; the TE 101 mode substrate integrated waveguide resonator is composed of an upper metal floor 3, a lower dielectric substrate 4, a lower metal floor 5, and a silver-plated slot 8. The lower metal floor 5 is provided with an input feeder 10 with slots on both sides. The silver-plated slot 8 is provided with breakpoints 9 filled with dielectric on both sides of the input feeder 10 and on both sides of the TE 101 mode substrate integrated waveguide resonator, for ensuring circuit manufacturing. The antenna in this embodiment also has an antenna input port S for inputting energy into the TE 101 mode substrate integrated waveguide resonator. The antenna input port S is connected to the end of the input feeder 10.

[0024] The upper metal floor 3 is provided with a coupling slot 7 at a position where the magnetic field of the TE 101 mode substrate integrated waveguide resonator is relatively strong, and the microstrip patch 1 is correspondingly arranged above the coupling slot 7. The TM 10 mode microstrip patch is provided with a pair of symmetric long slots 6 along the X direction. The long slots 6 are distributed on both sides of the projection of the coupling slot 7 on the TM 10 mode microstrip patch. As a preference, in this embodiment, the distance from the coupling slot 7 to the side where the notch of the long slot 6 is located is not less than the length of the long slot 6. The TE 101 mode substrate integrated waveguide cavity serves as the first-stage resonator of the filter, and the TM 10 mode microstrip patch 1 with a long slot 6 serves as the second-stage resonator of the filter and also serves as the radiator of the filtering antenna. The long slot 6 opened on the TM 10 mode microstrip patch enables the filtering antenna to obtain radiation null points in the upper stopband, so as to obtain stronger frequency selectivity in the upper stopband.

[0025] The length and width of the substrate integrated waveguide resonator can be easily determined by classical formulas. Port S represents the input, and a 50Ω grounded coplanar waveguide (GCPW) feeder is used to excite the TE 101 mode in the substrate integrated waveguide resonator. Both layers of the substrate of the proposed filtering antenna use Rogers 5880, with a relative dielectric constant of 2.2, a loss tangent of 0.0009, and a thickness of 10 mils.

[0026] After determining the initial dimensions of the microstrip patch antenna and the substrate integrated waveguide cavity according to the frequency, the filtering antenna is designed using the fitting method of a traditional bandpass filter. First, calculate the important parameters, the input external quality factor Q es , the radiation quality factor Q ri , and the coupling coefficient K, and determine the corresponding key dimensions in the proposed filtering antenna. Among them, the coupling between the two-stage resonators is realized through a coupling slot, and the width and length of the coupling slot are w1 and l1 respectively. The input external quality factor Q es is mainly determined by the feeding length of the feeder and the slit between the feeder and the cavity, that is, by the width w 101 of the slots opened on both sides of the input feeder of the TE g mode substrate integrated waveguide resonator and the length l g . As Figure 3 shows the extraction curves of the input external quality factor Q es and the coupling coefficient K of the proposed filtering antenna varying with the key parameters. It can be seen that the value of Q e decreases with the increase of w g and l g , and the value of K increases with the increase of w1 and l1. Finally, the final dimensions of the proposed filtering antenna can be determined after fine-tuning.

[0027] Specifically, a design method of a high-selectivity filtering antenna using a slotted microstrip patch includes the following steps:

[0028] Step 1: Calculate the lumped parameters of the low-pass prototype according to the performance indexes required by the filtering antenna, and calculate the coupling coefficient K and the input port external quality factor Q es , and the radiation quality factor Q r . The lumped elements of the low-pass prototype include g0, g1, and g2; the external quality factor coupling coefficient

[0029] Step 2: Establish a model of the high-selectivity filtering antenna using a slotted microstrip patch according to the parameters determined in Step 1, and adjust the first-stage TE 101 mode substrate integrated waveguide resonator and the second-stage TM 10The width w1 and length l1 of the coupling slot between the grooved microstrip patch resonators are such that the coupling between the first-order TE 101 mode substrate integrated waveguide resonator and the second-order TM 10 mode grooved microstrip patch resonators meets the design requirements.

[0030] Step 3. Adjust the width w 101 and length l g of the slots opened on both sides of the input feeder of the first-order TE g mode substrate integrated waveguide resonator so that it meets the external quality factor Q es of the input port S calculated in Step 1. When other parameters are fixed, increasing the width w g and length l g of the slit between the feeder and the substrate integrated waveguide cavity can effectively reduce the external quality factor. The final calculation results show that the Q r of the grooved microstrip patch resonator and the Q es of the input port are equal.

[0031] Step 4. Adjust the side length l c of the microstrip patch resonator and the relative permittivity of the upper dielectric substrate (2) so that the radiation quality factor Q r of the grooved microstrip patch resonator is equal to the external quality factor Q es of the input port.

[0032] Step 5. Adjust the length, width and the spacing between them of the long slot of the microstrip patch so as to introduce a radiation zero point in the upper stopband. Due to the introduction of the radiation zero point, the upper stopband obtains strong frequency selectivity. As Figure 4 shown, the position of the radiation zero point is mainly affected by the length of the long slot of the microstrip patch. The longer the l s , the closer the radiation zero point is to the passband.

[0033] For demonstration, a grooved microstrip patch filter antenna as Figure 1 shown is designed. The specific dimensions are as follows:

[0034] Parameter d p h w l <![CDATA[w l > <![CDATA[w0]]> <![CDATA[w1]]> Value (mm) 0.4 0.2 0.508 20 32.4 14.4 1.5 1.2 Parameter <![CDATA[w s > <![CDATA[w g > <![CDATA[l g > <![CDATA[l1]]> <![CDATA[l s > <![CDATA[l c > <![CDATA[s1]]> Value (mm) 0.3 0.5 2.5 2.3 4.2 8.8 3

[0035] d is the width of the silver-plated slot, p is the width at the breakpoint of the silver-plated slot, h is the height of the substrate, w is the width of the dielectric substrate, l is the length of the dielectric substrate, w l is the side length of the substrate integrated waveguide cavity, w0 is the width of the 50-ohm microstrip line, w1 is the coupling slot width, w s is the width of the long slot on the patch, w g is the width of the input feed coupling slot, l g is the length of the input feed coupling slot, l1 is the coupling slot length, ls is the length of the long slot on the patch, l c is the side length of the patch, s1 is the spacing between a pair of long slots on the patch. By changing the length l, width w and spacing of a pair of long slots, the position of the radiation null of the filtering antenna can be adjusted.

[0036] The slotted microstrip patch filtering antenna S of this embodiment 11 and the simulation results of the gain are shown in Figure 5 , the center frequency is f0 = 10.28 GHz, and the maximum gain obtained by simulation at 10.28 GHz is 6.5 dB. Compared with the filtering antenna without slots, a radiation null can be observed at 10.86 GHz in the upper stopband of the proposed filtering antenna in the gain response. The passband edge is steep and has high frequency selectivity. The E and H plane radiation patterns of the filtering antenna at 10.14 and 10.34 GHz are shown in Figure 6 . The measured cross polarization is at least 20 dB lower than the main polarization.

[0037] In addition to the above embodiments, the present invention may also have other embodiments. All technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope required by the present invention.

Claims

1. A highly selective filtering antenna using a slotted microstrip patch, characterized by: Including TE stacking from bottom to top 101 The module substrate integrates the waveguide resonant cavity, the upper dielectric substrate (2) and the TM 10 mode microstrip patch (1); the TE 101 The module-substrate integrated waveguide resonant cavity is composed of an upper metal floor (3), a lower dielectric substrate (4), a lower metal floor (5) and a silver coating groove (8), wherein the silver coating groove (8) is arranged on the lower dielectric substrate (4); the TM 10 The microstrip patch (1) and the upper dielectric substrate (2) form the TM 10 Mode microstrip patch resonator; the upper metal floor (3) is provided with a TE 101 The coupling slot (7) where the magnetic field of the mode-substrate integrated waveguide resonant cavity is stronger, TM 10 The TM microstrip patch (1) is arranged above the coupling slot (7), and is characterized in that: the TM 10 The mode microstrip patch is provided with a pair of symmetrical long slots (6) along the X direction to obtain a high-frequency radiation zero point, wherein the long slots (6) are distributed in the coupling slot (7) in the TM 10 The lower metal floor (5) is provided with an input feeder (10) with slots on both sides, and the silver-coated groove (8) is provided on both sides of the input feeder (10) and the TE 101 Breakpoints (9) for connecting the inner and outer media of the substrate integrated waveguide resonant cavity are respectively provided on both sides of the substrate integrated waveguide resonant cavity.

2. The highly selective filtering antenna using a slotted microstrip patch according to claim 1, wherein: The silver coating grooves (8) are replaced by metal through holes arranged at intervals.

3. The highly selective filtering antenna using a slotted microstrip patch according to claim 1, characterized in that: There is also a device for inputting energy into TE 101 Antenna input port of the substrate integrated waveguide resonator ( S ), the antenna input port ( S ) is connected to the end of the input feeder (10).

4. The highly selective filtering antenna using a slotted microstrip patch according to claim 3, wherein: The distance from the coupling slot (7) to the side of the slot opening of the long slot (6) is not less than the length of the long slot (6).

5. The highly selective filtering antenna using a slotted microstrip patch according to claim 1, characterized in that: The TE 101 The TM substrate integrated waveguide cavity is used as the first resonator of the filter, with a long slot (6) 10 The microstrip patch (1) serves as a second-stage resonator of the filter and also as a radiator of the filtering antenna, which has a radiation null in the upper stop band.

6. The design method of a highly selective filtering antenna using a slotted microstrip patch according to claims 1-5, characterized in that The following steps are involved: Step 1: Calculate the low-pass prototype lumped parameters based on the performance indicators required by the filtering antenna, and calculate the coupling coefficient accordingly K , input port external quality factor Q es , radiation quality factor Q r ; Step 2: Establish a model of a highly selective filtering antenna using a slotted microstrip patch as claimed in claim 1 based on the parameters determined in step 1, and adjust the first stage TE 101 Module-substrate integrated waveguide resonator with 2nd stage TM 10 The width of the coupling slot between the microstrip patch resonators w 1 and the length of the coupling slot l 1, making the first level TE 101 Module-substrate integrated waveguide resonator with 2nd stage TM 10 The coupling between the slotted microstrip patch resonators meets the design requirements; Step 3: Adjust the load on the first level TE 101 The width of the slots on both sides of the input feed line of the substrate integrated waveguide resonator w g and length l g , so that it satisfies the input port calculated in step 1 ( S ) of the external quality factor Q es ; Step 4: Adjust the side length of the microstrip patch resonator l c The relative dielectric constant of the upper dielectric substrate (2) makes the radiation quality factor of the slotted microstrip patch resonator Q r Equal to the external quality factor of the input port Q es ; Step 5: Adjust the length, width and spacing between the long slots of the microstrip patch to introduce a radiation zero point in the upper stopband.

7. The method for designing a highly selective filtering antenna using a slotted microstrip patch according to claim 6, wherein: The lumped parameters of the low-pass prototype include g 0, g 1 and g 2. External quality factor , coupling coefficient .

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