CN108808269A - Multilayered structure integrating filtering antenna based on filtering balun - Google Patents

Abstract

The invention discloses a multi-layer structure integrated filter antenna based on a filter balun, which mainly solves the problem of large volume of the filter antenna with a traditional single-layer microstrip structure. It includes a dielectric substrate, a filtering part and a radiation unit. The dielectric substrate includes two layers of microstrip dielectric substrate and metal ground; the filter part includes the input port, the filter balun on the left side of the dielectric substrate, and two output ports connected to it; the filter balun includes the etched on the upper dielectric substrate Two face-to-face C-shaped second-order ladder impedance resonators and two back-to-back C-shaped second-order ladder impedance resonators etched on the upper surface of the lower dielectric substrate; the radiation unit is etched on the upper surface of the upper dielectric substrate, which includes two Strip microstrip line, two butterfly printed dipoles and a director. The invention has the advantages of compact structure, wide bandwidth, high frequency edge selectivity and good out-of-band suppression, and can be used for the radio frequency front end of the wireless communication system.

Description

Multi-layer structure integrated filter antenna based on filter balun

technical field

The invention belongs to the technical field of microwave devices, and in particular relates to a multi-layer structure integrated filter antenna, which can be used for a radio frequency front end of a wireless communication system.

Background technique

In recent years, the development of wireless communication technology has become more and more rapid, people have higher and higher requirements for the performance and volume of communication systems, and the performance of microwave communication components is becoming more and more multifunctional and integrated. , The appearance is also more and more towards the direction of miniaturization and portability.

The wireless communication system is composed of three parts: sending equipment, receiving equipment and wireless channels, and uses wireless electromagnetic waves to realize information and data transmission systems. It is classified according to the working frequency band or transmission means, and can be divided into medium wave communication, short wave communication, ultrashort wave communication, microwave communication and satellite communication. Antennas and Filters

It is two indispensable components in the wireless communication system, in which the antenna is responsible for converting high-frequency electrical oscillations into electromagnetic waves to radiate to the transmission medium and converting electromagnetic waves that propagate through space into high-frequency electrical oscillations. The filter is responsible for selecting the frequency band we are interested in from the working frequency band. As the two most important components of the RF front-end circuit, the size and performance of the antenna and filter play a vital role in the communication quality of the entire system.

The original filter antenna design method is to design the filter and the antenna separately, and then add a matching network or structure between the two to make the reflection reduction impedance between the antenna and the filter more matched. However, this method also has many disadvantages, such as increasing the workload of system design, the mismatch may cause the deterioration of system performance, and also increase the system size.

In recent years, many scholars have explored the method of integrated design filter antenna. This comprehensive design method focuses on the overall performance of the antenna and filter. According to the comprehensive method of the band-pass filter, the antenna replaces the last stage resonator and load impedance of the filter, so that the antenna also acts as a filter while radiating. The resonant unit of the device constitutes an integrated filter antenna with compact structure.

In 2015, J.Shi and X.Wu published "A Compact Differential Filtering Quasi-Yagi Antenna With High Frequency Selectivity and Low Cross -PolarizationLevels", the paper proposes a differential quasi-Yagi antenna with filter response, but the radiator does not have a resonator as a filter, which is not conducive to reducing size and reducing loss.

In 2015, C.X.Mao and S.Gao et al published "Integrated Filtering Antenna with Controllable Frequency Bandwidth" in IEEE Transactions Antennas and Propagation journal (Vol.63, No.12, 2015, pp.5492–5499.), in the paper The integrated design of the filter and the antenna widens the bandwidth, improves the frequency selectivity and obtains a flatter gain, however, an additional filter circuit is introduced into the antenna feeding network, resulting in increased insertion loss.

In 2016, Tang.H and Chen J.X et al. published "Integration design of filtering antenna with load-insensitive balun filter" in IEEE Transactions on Components Packaging & Manufacturing Technology (No.6, 2016, pp.1408-1416.). The paper uses a single However, when the working frequency band is low, the size of the designed filter antenna will be relatively large, resulting in a large volume of the entire system, which cannot well meet the increasingly stringent requirements of microwave devices. miniaturization requirements.

Contents of the invention

Aiming at the deficiencies of the prior art above, the present invention proposes a multi-layer structure integrated filter antenna based on a filter balun, which reduces the volume of the antenna, reduces the insertion loss, and improves the efficiency of the antenna.

In order to achieve the above object, the present invention is based on the filter balun's multi-layer structure integrated filter antenna, including filter part 1, substrate part 2 and radiation unit 3, characterized in that:

The substrate part 2 includes two layers of microstrip dielectric substrates 21, 22 and the bottom metal floor 23;

The filtering part 1 includes an input port microstrip line 11, two output port microstrip lines 12, 13 and a filtering balun 14 etched on the left side of the upper and lower surfaces of the upper dielectric substrate 21;

The radiation unit 3 adopts a quasi-Yagi antenna etched on the right half of the upper surface of the upper dielectric substrate 21. The quasi-Yagi antenna includes: two λ/4 microstrip lines 31, 32, and two butterfly-shaped printed dipoles 33, 34 And a director 35; the right end of the first λ/4 microstrip line 31 is connected with the first butterfly printed dipole 33, and the left end of the first microstrip line 31 is connected with the filter balun output port microstrip line 12; The right end of the second λ/4 microstrip line 32 is connected with the second butterfly printed dipole 34, and the left end of the second λ/4 microstrip line 32 is connected with the microstrip line 13 of the filter balun output port; the director 35 It is located on the right side of the two butterfly-shaped printed dipoles 33, 34 and is horizontally parallel to them.

Compared with the prior art, the present invention has the following advantages:

1. Since the present invention adopts two layers of microstrip dielectric substrates and is tightly pressed together, compared with the filter antenna with a single-layer microstrip structure in the same frequency band, the overall size is smaller, and the volume of the filter antenna is miniaturized and thinner , lower processing cost, easier to integrate with other components of the microwave radio frequency system;

2. The present invention is owing to introducing filtering balun 14 at the feeding end of quasi-Yagi antenna, replaces the feeding structure transitioning to coplanar stripline from microstrip line structure with filtering balun, can convert the unbalanced input signal of single end It can form a balanced output signal and feed the butterfly printed dipole, which is beneficial to the surface current balance of the butterfly printed dipole, which can ensure the antenna directivity and improve the radiation efficiency; and can effectively suppress the The common mode signal plays the role of impedance transformation, realizes the impedance matching of the antenna, and improves the out-of-band suppression of the overall filter antenna;

3. The filter balun of the feeding part of the present invention adopts two face-to-face C-shaped second-order ladder impedance resonators and two back-to-back C-shaped second-order ladder impedance resonators, which are respectively etched on the upper surfaces of the upper and lower dielectric substrates, Make the size of the multi-layer filter balun smaller, effectively reducing the size of the filter antenna;

4. The feeding part of the present invention adopts two layers of high-permittivity microstrip dielectric substrates, which effectively reduces the size of the antenna; at the same time, the electrical coupling between the resonators on the upper and lower layers is enhanced, and the bandwidth of the filter balun is expanded. Increased the bandwidth of the filter antenna;

5. The radiation unit of the present invention uses a butterfly-shaped printed dipole to replace the traditional rectangular structure, which increases the resonant mode of the antenna and expands the bandwidth of the filter antenna;

6. The two output port microstrip lines of the feeding part of the present invention adopt 45-degree chamfering treatment at all outer corners, which reduces the reflection of the signal in the transmission process, reduces the antenna loss, and improves the impedance matching performance of the filter antenna .

Description of drawings

Fig. 1 is a three-dimensional structural diagram of the present invention;

Fig. 2 is a front structural view of the upper part of the upper dielectric substrate in Fig. 1;

Fig. 3 is a partial enlarged front view of the filter balun on the upper part of the lower dielectric substrate in Fig. 1;

Fig. 4 is a partially enlarged front structural view of the upper part of the lower dielectric substrate in Fig. 1;

Fig. 5 is a left view structure diagram of Fig. 1;

Fig. 6 is the reflection coefficient S ₁₁ graph of the embodiment of the present invention;

Fig. 7 is the XOY plane and the YOZ plane direction diagram of the embodiment of the present invention;

FIG. 8 is a gain curve diagram of an embodiment of the present invention.

Detailed ways

Embodiment and effect of the present invention are described in detail below in conjunction with accompanying drawing:

Embodiment 1, a multi-layer structure integrated filter antenna based on a filter balun working at 2.45 GHz.

Referring to FIG. 1 , this example includes a filtering part 1 , a substrate part 2 and a radiation unit 3 . Among them: the substrate part 2 is composed of two layers of dielectric substrates 21, 22, and a metal floor 23; the radiation unit 3 is composed of two λ/2 microstrip lines 31, 32, two butterfly-shaped printed dipoles 33, 34 and a director 35 composition. Filter part 1 is made up of input port microstrip line 11, output port microstrip line 12, 13 and filtering balun 14, and this filtering balun 14 is made up of two face-to-face C-shaped λ/2 second-order ladder impedance resonators 141, 142 and two back-to-back C-shaped λ/2 second-order ladder impedance resonators 143 and 144.

Input port microstrip line 11, output port microstrip line 12, 13, two half-wavelength microstrip lines 31, 32, first C-shaped λ/2 second-order ladder impedance resonator 141, first reverse C-shaped λ/2 The second-order ladder impedance resonator 142, the two butterfly dipoles 33, 34 and the director 35 are all etched on the upper surface of the upper dielectric substrate 21; the second reverse C-shaped λ/2 second-order ladder impedance resonator 143, The second C-shaped λ/2 second-order ladder impedance resonator 144 is etched on the upper surface of the lower dielectric substrate 22, the second reverse C-shaped λ/2 second-order ladder impedance resonator 143, the second C-shaped λ/2 second-order ladder Impedance resonators 144 are respectively located below the first C-shaped λ/2 second-order ladder impedance resonator 141 and the first reverse C-shaped λ/2 second-order ladder impedance resonator 142, and are parallel to them up and down; the bottom of the lower dielectric substrate 22 The surface is plated with copper to form a metal floor 23 .

The left end of the first λ/4 microstrip line 31 is connected to the upper end of the first inverted C-shaped λ/2 second-order ladder impedance resonator 142, and the right end is connected to the first butterfly-shaped printed dipole 33; the second λ/4 microstrip The left end of the line 32 is connected to the lower end of the first inverted C-shaped λ/2 second-order ladder impedance resonator 142, and the right end is connected to the second butterfly-shaped printed dipole 34, and the two butterfly-shaped printed dipoles are replaced by a butterfly-shaped structure The traditional rectangular structure expands the bandwidth of the filter antenna; the director 35 is placed on the right side of the two butterfly-shaped printed dipoles 33 and 34 and parallel to the two butterfly-shaped printed dipoles.

The lower end of the input port microstrip line 11 is connected to the upper end of the first C-shaped λ/2 second-order ladder impedance resonator 141; the left end of the first output port microstrip line 12 is connected to the first reverse C-shaped λ/2 second-order ladder impedance resonator 142 upper end is connected, and the right end is connected with the first λ/4 microstrip line 31; Two λ/4 microstrip lines 32 are connected.

Referring to Figure 2, the parameters of the radiation unit in this example are set as follows

The two λ/4 microstrip lines 31 and 32 of the radiating unit have the same size and the length is λ _g /4, where λ is the working wavelength. In this example, the length of the first λ/4 microstrip line 31 is l ₁₁ =16mm, the width is w ₁₁ =3.5mm, the length of the second λ/4 microstrip line 32 is l ₁₂ =16mm, The width is w ₁₂ =3.5mm, the first λ/4 microstrip line 31 and the second λ/4 microstrip line 32 are separated by a gap with an interval s ₂ =0.8mm; two butterfly-shaped printed dipoles 33, 34 have the same size, the short side width w ₁₅ of the first butterfly-shaped printed dipole 33 = 5 mm, the long side width w ₁₇ = 9.6 mm, and the length l ₁₅ = 24 mm; the short side of the second butterfly-shaped printed dipole 34 Width w ₁₆ = 5mm, long side width w ₁₈ = 9.6mm, length l ₁₆ = 24mm; the director is on the right side of the two butterfly-shaped printed dipoles, width w ₁₉ = 8mm, length l ₁₇ = 29mm, spaced from it It is d=9mm.

Referring to Figure 5, the parameters of the dielectric substrate in this example are set as follows

The two-layer microstrip dielectric substrates 21 and 22 adopt a dielectric material with a dielectric constant ε _r of 3.5 and a thickness h of 0.508 mm, wherein the value of ε _r ranges from 3.5 to 7.5, because A high dielectric constant ε _r means a smaller dielectric wavelength, and the increase of the dielectric constant will lead to a decrease in the operating frequency of the antenna without changing the size of the antenna. In this example, only ε _r is taken as 3.5, and the lower surface of the lower dielectric substrate is a copper-clad metal ground plate 23;

The overall dimensions of the filter balun-based multilayer integrated filter antenna implemented in this embodiment are: length 80 mm, width 72 mm, height 1.016 mm.

Referring to Figure 2, Figure 3 and Figure 4, the parameters of the filtering part in this example are set as follows:

The length t ₀ of the input port microstrip line 11 = 15mm, and the width w ₀ = 2.4mm; the shape and size of the two symmetrical output port microstrip lines 12 and 13 are the same, and the first output port microstrip line 12 circumference length l ₁₁ =39.8mm, width w ₁₁ =2.4mm; second output port microstrip line 13 perimeter l ₁₂ =39.8mm, width w ₁₂ =2.4mm. Each of the two output port microstrip lines includes 3 outer corners and 3 inner corners, a total of 6 corners, and all outer corners are cut at 45 degrees.

The first layer of the filter balun is two face-to-face C-shaped λ/2 second-order ladder impedance resonators 141, 142, which are symmetrical along the center line. They are respectively the first C-shaped λ/2 second-order ladder impedance resonator 141 and the first reverse C-shaped λ/2 second-order ladder impedance resonator 142 . The first C-shaped λ/2 second-order ladder impedance resonator 141 has a shape similar to a letter C and is symmetrical along the center line, and is composed of five-order microstrip lines. The length l ₁ and width w ₁ of the first stage are the same as the length l ₅ and width w ₅ of the fifth stage, that is, l ₁ =l ₅ =4.6mm, w ₁ =w ₅ =2.5mm; the length of the second stage l ₂ and width w ₂ are the same as the length l ₄ and width w ₄ of the fourth stage, that is, l ₂ =l ₄ =4.6mm, w ₂ =w ₄ =0.5mm; the length l ₃ of the third stage =9mm, Width w ₃ =2.5mm. The first C-shaped λ/2 second-order ladder impedance resonator 141 is matched from 100 Ω to the input port microstrip line 11 of 50 Ω through a gradient line.

The first reverse C-shaped λ/2 second-order ladder impedance resonator 142 is similar to the reverse letter C, symmetrical along the center line, and also composed of fifth-order microstrip lines. The length l ₆ and width w ₆ of the first stage are the same as the length l ₁₀ and width w ₁₀ of the fifth stage, that is, l ₆ =l ₁₀ =4.6mm, w ₆ =w ₁₀ =3.2mm; the length of the second stage l ₇ and width w ₇ are the same as the length l ₉ and width w ₉ of the fourth stage, that is, l ₇ =l ₉ =5.5mm, w ₇ =w ₉ =0.5mm; the length of the third stage l ₈ =9mm, w ₈ =3.2mm;

The first C-shaped λ/2 second-order ladder impedance resonator 141 is separated from the first inverse C-shaped λ/2 second-order ladder impedance resonator 142 by a gap with an interval of s ₁ =0.2mm.

The second layer of the filtering balun is two C-shaped λ/2 second-order ladder impedance resonators 143 and 144 back-to-back and of the same size, which are symmetrical along the center line. They are the second inverted C-shaped λ/2 stepped impedance resonator 143 and the second C-shaped λ/2 stepped impedance resonator 144 respectively. The second inverted C-shaped λ/2 stepped impedance resonator 143 is similar in shape to an inverted letter C, and is composed of fifth-order microstrip lines. The length k ₁ and width q ₁ of the first stage are the same as the length k ₅ and width q ₅ of the fifth stage, that is, k ₁ =k ₅ =5mm, q ₁ =q ₅ =0.6mm; the length k of the second stage _2. The width q ₂ is the same as the length k ₄ and width q ₄ of the fourth stage, that is, k ₂ =k ₄ =3mm, q ₂ =q ₄ =0.3mm; the length k ₃ of the third stage =13mm, width q ₃ =0.3 mm; the second C-shaped λ/2 stepped impedance resonator 144 has the same size and opposite shape as the second reverse C-shaped λ/2 stepped impedance resonator 143 , separated by a gap with a width of s ₀ =0.3 mm.

Embodiment 2, a multi-layer structure integrated filter antenna based on a filter balun working at 2.16 GHz.

With reference to Fig. 1, the structure of this example is identical with the structure of embodiment 1, and its parameter setting is as follows:

The dielectric constant ε _r =4.5, the vertical length of the butterfly printed dipole is 26mm, the length of the short side is 5.2mm, and the length of the long side is 10mm. The two λ/4 microstrip lines 31 and 32 of the radiation unit have the same size, and their width is the same as the width parameter given in Embodiment 1, and their lengths are λ _g /4, where λ is the working wavelength.

The input port microstrip lines constituting the filter part, two output port microstrip lines, two face-to-face C-shaped λ/2 second-order ladder impedance resonators and two back-to-back C-shaped λ/2 second-order ladders of the filter balun The dimensions of the impedance resonators are the same as the parameters given in Embodiment 1.

The size of the director constituting the radiation unit is the same as in Embodiment 1.

Embodiment 3, a multi-layer structure integrated filter antenna based on a filter balun working at 1.68 GHz.

With reference to Fig. 1, the structure of this example is identical with the structure of embodiment 1, and its parameter setting is as follows:

The dielectric constant ε _r =7.5, the vertical length of the butterfly-shaped printed dipole is 28 mm, the length of the short side is 5.4 mm, and the length of the long side is 10.4 mm. The two λ/4 microstrip lines 31 and 32 of the radiation unit have the same size, the width is the same as the width parameter given in Embodiment 1, and the lengths are λ _g /4, where λ is the working wavelength.

The input port microstrip line that constitutes the filtering part, two output port microstrip lines and two face-to-face C-shaped λ/2 second-order ladder impedance resonators and two back-to-back C-shaped λ/2 second-order ladders of the filter balun The dimensions of the impedance resonators are the same as the parameters given in Embodiment 1.

The size of the director constituting the radiation unit is the same as in Embodiment 1.

Effect of the present invention can be further illustrated by following simulation:

Simulation 1 is to simulate the reflection characteristic of the antenna in Embodiment 1 of the present invention, and the result is shown in FIG. 5 , where the reflection coefficient curve of port 1 represents the reflection characteristic curve of the input port.

It can be seen from FIG. 6 that in the frequency range of 2.344GHz to 2.845GHz, the reflection characteristic curve of the present invention is less than -15dB, indicating that the energy reflected by the input port is small, the frequency edge selectivity is high, and the out-of-band suppression is good.

Simulation 2 is to simulate the radiation pattern of the XOY plane and YOZ plane of the antenna of Embodiment 1, and the result is shown in Figure 6, wherein the solid line is the XOY plane pattern, and the dotted line is the YOZ plane pattern.

It can be seen from FIG. 7 that at 2.45 GHz, the present invention can maintain good directivity in a wide frequency band, that is, radiate toward the Y-axis direction, and is a typical end-fire antenna.

Simulation 3 is to simulate the gain of the antenna in Embodiment 1, and the result is shown in FIG. 7 , where the curve is the gain curve.

It can be seen from Figure 8 that in the frequency range of 2.344GHz to 2.845GHz, the frequency edge selectivity is high, the filtering effect is obvious, and the gain is greater than 4dB in a wider frequency band, which has a relatively high gain and the gain changes smoothly.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (8)

1. a kind of multilayered structure integrating filtering antenna based on filtering balun, including filtering part (1), substrate portion (2) and spoke Penetrate unit (3) it is characterized in that：

The substrate portion (2) includes two layers of microstrip dielectric substrate (21,22) and undermost metal floor (23)；

The filtering part (1) includes input port microstrip line (11), and two output port microstrip lines (12,13) and etching are upper Filtering balun (14) on the left of layer medium substrate (21) upper and lower surface；

The radiating element (3) is using etching in the Quasi-Yagi antenna of upper layer medium substrate (21) upper surface right half part, the standard Yagi aerial includes：Two microstrip lines (31,32), two butterfly printed dipoles (33,34) and a director (35)；First The right end of microstrip line (31) is connected with the first butterfly printed dipole (33), and the left end and filtering balun of the first microstrip line (31) are defeated Exit port microstrip line (12) is connected；The right end of second microstrip line (32) is connected with the second butterfly printed dipole (34), and second is micro- Left end with line (32) is connected with filtering balun output port microstrip line (13)；Director (35) is located at two butterfly printed dipoles The right side of sub (33,34) and with its horizontal parallel；

The filtering balun (14), including two aspectant C-shaped second order step electric impedance resonators (141,142) and two lean against The C-shaped second order step electric impedance resonator (143,144) of the back of the body.

2. antenna according to claim 1, which is characterized in that two aspectant C-shaped second order step electric impedance resonators (141,142) etching is in upper layer medium substrate (21) upper surface, two back-to-back C-shaped second order step electric impedance resonators (143, 144) etching is in layer dielectric substrate (22) upper surface；Two back-to-back C-shaped second order step electric impedance resonators (143,144) are respectively Positioned at the lower section of two face-to-face C-shaped second order step electric impedance resonators (141,142), and with two face-to-face C-shaped second order ladders Electric impedance resonator (141,142) is parallel up and down.

3. antenna according to claim 1, which is characterized in that the upper end of the first C-shaped second order step electric impedance resonator (141) It is connected with the lower end of input port microstrip line (11)；Second C-shaped second order step electric impedance resonator (142) is parallel to be placed in the first C-shaped The right side of second order step electric impedance resonator (141)；Second C-shaped second order step electric impedance resonator (142) upper end and output port are micro- Left end with line (12) is connected, and lower end is connected with the left end of output port microstrip line (13).

4. antenna according to claim 1, which is characterized in that two layers of microstrip dielectric substrate (21,22) is to be situated between The high dielectric constant material that electric constant is.

5. antenna according to claim 1, which is characterized in that undermost metal floor (23) is to cover copper metal ground connection Plate.

6. antenna according to claim 1, which is characterized in that two butterfly printed dipole (33,34) structures Identical, each butterfly printed dipole vertical length is that short side is long, the long length of side.

7. antenna according to claim 1, which is characterized in that two class S-shaped output port microstrip lines (12,13) are along center Horizontal axis is symmetrically placed, and each microstrip line includes 3 exterior angles and 3 interior angles totally 6 turnings, and all outer turnings are using 45 degree Corner cut processing.

8. antenna according to claim 1, which is characterized in that two microstrip line (31,32) sizes are identical, and length is, Wherein, it is operation wavelength.