Broadband reflection-free filtering antenna

Abstract

The invention discloses a broadband reflection-free filtering antenna which is provided with a stop-band energy absorption structure, a high-low impedance microstrip line and a yagi-like radiator which are connected in sequence. The yagi-like radiator is composed of a pair of dipole arms and two pairs of bilateral parallel parasitic patches. Wherein the stop-band energy absorption structure is composed of two microstrip line band-stop filters, two grounded chip resistors, a section of folded phase line and a section of input microstrip feeder line. The two microstrip band-stop filters are respectively connected with a grounded chip resistor, and the two microstrip band-stop filters are connected through a folding phase line. The antenna is high in structural compactness, and meanwhile, the integrated design of the filter and the antenna and the ultra-wide non-reflection bandwidth are realized.

Description

Technical Field

[0001] The present invention relates to a wireless communication device, and particularly to a broadband reflectionless filtering antenna. Background Art

[0002] With the rapid development of wireless communication, modern radio frequency systems have put forward higher and higher requirements for the performance of antennas. In a wireless communication system, antennas and filters are usually designed as independent modules. The antenna is responsible for radiating or receiving signals, and the filter is used to suppress out-of-band interference. This discrete design often causes a series of problems in practical applications. The interface between the antenna and the filter is prone to impedance mismatch, resulting in return loss, reducing the energy transmission efficiency, affecting the system signal-to-noise ratio; at the same time, discrete components occupy a large space and are difficult to meet the requirements of modern communication devices for miniaturization and integration. To solve the problems of discrete design, the filtering antenna technology is proposed, which directly integrates the filtering function into the antenna structure to achieve the integration of radiation and filtering.

[0003] Traditional filtering antennas reflect most of the incident energy in the stopband. Due to impedance mismatch or complex electromagnetic environment, a part of the input signal may be reflected back to the signal source as a reflected wave, resulting in reduced transmission efficiency, poor signal quality, reduced signal-to-noise ratio, and even causing system instability. To avoid or mitigate this instability problem, isolators, circulators or even attenuators are usually used. However, this method not only makes the antenna system bulky and expensive, but also increases the insertion loss. Summary of the Invention

[0004] Object of the Invention: Aiming at the above-mentioned prior art, a broadband reflectionless filtering antenna device is proposed to achieve the integrated design of the filter and the antenna and an ultra-wide reflectionless bandwidth.

[0005] Technical Solution: A broadband reflectionless filtering antenna includes: a radiator, two band-stop filters and a folded microstrip line; each of the two band-stop filters is respectively connected with a grounded patch resistor, the feeding port of the antenna is directly connected to one of the band-stop filters, and at the same time is connected to the other band-stop filter and the radiator through the folded microstrip line, that is, the two band-stop filters are respectively connected in parallel at the feeding port and the radiator.

[0006] Further, the radiator adopts a Yagi-like radiator, which includes dipole arms, a first double-sided parallel parasitic patch, and a second double-sided parallel parasitic patch that are arranged in sequence along the radiation direction and are mutually coupled.

[0007] Further, one arm of the dipole arms is located on the upper surface of the dielectric plate, and the other arm is located on the lower surface of the dielectric plate, and the arm located on the lower surface is connected to the metal floor.

[0008] Furthermore, both the first bilateral parallel parasitic patch and the second bilateral parallel parasitic patch are respectively composed of rectangular metal patches located on both sides of the dielectric substrate and distributed offset.

[0009] Furthermore, the input microstrip feeder serving as the feeding port is connected to the connection point between the first microstrip band-stop filter and the folded phase line; the free end of the first microstrip band-stop filter is connected to one end of the first patch resistor, and the other end of the first patch resistor is connected to the metal floor through the first metal via; the free end of the second microstrip band-stop filter is connected to one end of the second patch resistor, and the other end of the second patch resistor is connected to the metal floor through the second metal via.

[0010] Furthermore, the antenna further includes a cross-shaped high-low impedance microstrip line disposed between the Yagi-like radiator and one of the band-stop filters; the cross-shaped high-low impedance microstrip line is formed by the intersection of a high-impedance line and a low-impedance line perpendicular to each other, forming a cross-shaped geometric structure.

[0011] Furthermore, in the cross-shaped high-low impedance microstrip line, the length and width of the low-impedance line on one side of the cross center are both smaller than those of the low-impedance line on the other side.

[0012] Advantages: 1) By adopting the distribution design of two microstrip band-stop filters on both sides of the microstrip feeder, compared with the case of one microstrip band-stop filter, the antenna only increases in size by a very small amount and greatly broadens the reflectionless bandwidth of the antenna. 2) Through the structural design of the Yagi-like radiator, the radiation of the antenna has an end-fire characteristic. 3) By adding parasitic patches to the radiator, radiation nulls are introduced, making the radiation of the antenna have obvious filtering characteristics. 4) The present invention provides a broadband reflectionless filtering antenna, which simultaneously realizes the integrated design of the filter and the antenna and an ultra-wide reflectionless bandwidth. The antenna has the advantages of strong compactness, wide reflectionless frequency band, high radiation efficiency, and significant filtering effect. Description of the Drawings

[0013] Figure 1 It is the structural topology diagram of the broadband reflectionless filtering antenna according to the embodiment of the present invention; Figure 2 It is the structural schematic diagram of the broadband reflectionless filtering antenna according to the embodiment of the present invention; Figure 3 It is the structural schematic diagram of the Yagi-like radiator of the broadband reflectionless filtering antenna according to the embodiment of the present invention; Figure 4 It is the structural schematic diagram of the high-low impedance microstrip line of the broadband reflectionless filtering antenna according to the embodiment of the present invention; Figure 5 It is the structural schematic diagram of the stop-band energy absorption structure of the broadband reflectionless filtering antenna according to the embodiment of the present invention; Figure 6 Schematic diagram of the reflection coefficient of the broadband reflectionless filtering antenna according to an embodiment of the present invention; Figure 7 Schematic diagram of the gain of the broadband reflectionless filtering antenna according to an embodiment of the present invention; Figure 8 E-plane radiation pattern of the broadband reflectionless filtering antenna according to an embodiment of the present invention; Figure 9 H-plane radiation pattern of the broadband reflectionless filtering antenna according to an embodiment of the present invention; Reference numerals: 100 - Yagi-like radiator, 101 - dipole arms, 102 - first bilateral parallel parasitic patch, 103 - second bilateral parallel parasitic patch, 200 - high-low impedance microstrip line, 300 - stopband energy absorption structure, 301 - first microstrip band-stop filter, 302 - second microstrip band-stop filter, 303 - folded phase line, 304 - input microstrip feeder, 305 - first patch resistor, 306 - second patch resistor, 307 - first metal via, 308 - second metal via, 400 - metal floor, 500 - dielectric substrate. Detailed implementation manners

[0014] The following further explains the present invention with reference to the accompanying drawings.

[0015] As shown in Figure 1 A broadband reflectionless filtering antenna has a topological structure mainly composed of a radiator, two band-stop filters, and a folded microstrip line. Each of the two band-stop filters is connected to a grounded patch resistor. The feeding port of the antenna is directly connected to one of the band-stop filters, and at the same time is connected to the other band-stop filter and the radiator through a folded microstrip line, that is, the two band-stop filters are respectively connected in parallel at the feeding port and the radiator.

[0016] Specifically, as shown in Figure 2 A broadband reflectionless filtering antenna includes a Yagi-like radiator 100, a cross-shaped high-low impedance microstrip line 200, a stopband energy absorption structure 300, a metal floor 400, and a dielectric substrate 500. The structure from the feeding port to the radiator is successively the stopband energy absorption structure 300, the cross-shaped high-low impedance microstrip line 200, and the Yagi-like radiator 100. The metal floor 400 is located on the lower surface of the dielectric substrate 500, and the main part of the metal floor 400 covers the half region where the stopband energy absorption structure 300 and the cross-shaped high-low impedance microstrip line 200 are located.

[0017] As shown in Figure 3As shown in the figure, the Yagi - like radiator 100 includes dipole arms 101, a first bilateral parallel parasitic patch 102, and a second bilateral parallel parasitic patch 103. Among them, one arm of the dipole arms 101 is located on the upper surface of the dielectric plate 500, and the other arm is located on the lower surface of the dielectric plate 500, and the arm located on the lower surface is connected to the metal floor 400. Along the radiation direction, the first bilateral parallel parasitic patch 102 and the second bilateral parallel parasitic patch 103 are sequentially distributed at the front end of the dipole arms 101. Both the first bilateral parallel parasitic patch 102 and the second bilateral parallel parasitic patch 103 are respectively composed of rectangular metal patches that are offset and distributed on both sides of the dielectric plate 500. There is mutual coupling among the dipole arms 101, the first bilateral parallel parasitic patch 102, and the second bilateral parallel parasitic patch 103.

[0018] As Figure 4 shown in the figure, the cross - shaped high - low impedance microstrip line 200 is located on the upper surface of the dielectric plate 500 and is formed by the intersection of mutually perpendicular high - impedance lines (narrow line widths) and low - impedance lines (wide line widths), forming a cross - shaped geometric structure. In this embodiment, the length and width of the low - impedance line on one side of the cross center are both smaller than those of the low - impedance line on the other side.

[0019] As Figure 5 shown in the figure, the stop - band energy absorption structure 300 is located on the upper surface of the dielectric plate 500 and includes a first microstrip band - stop filter 301, a second microstrip band - stop filter 302, a folded phase line 303, an input microstrip feeder 304, a first patch resistor 305, and a second patch resistor 306. The first microstrip band - stop filter 301 and the second microstrip band - stop filter 302 are connected by the folded phase line 303, and the input microstrip feeder 304 is connected to the connection point between the first microstrip band - stop filter 301 and the folded phase line 303. The free end of the first microstrip band - stop filter 301 is connected to one end of the first patch resistor 305, and the other end of the first patch resistor 305 is connected to the metal floor 400 through the first metal via 307. Similarly, the free end of the second microstrip band - stop filter 302 is connected to one end of the second patch resistor 306, and the other end of the second patch resistor 306 is connected to the metal floor 400 through the second metal via 308.

[0020] The cross - shaped high - low impedance microstrip line 200 connects the Yagi - like radiator 100 and the stop - band energy absorption structure 300. Specifically, one low - impedance line of the cross - shaped high - low impedance microstrip line 200 is connected to one arm of the Yagi - like radiator 100, and the other low - impedance line is connected to the connection point between the second microstrip band - stop filter 302 and the folded phase line 303.

[0021] In the above structure, the Yagi - like radiator 100 introduces radiation nulls, making the gain of the antenna show an obvious filtering phenomenon. The stop - band energy absorption structure 300 absorbs the stop - band energy of the Yagi - like radiator 100 through a patch resistor, making the antenna show a reflection - free phenomenon within a wide band.

[0022] Specifically, the dipole arms 101 of the Yagi - like radiator 100 introduce the first resonance point. The first double - sided parallel parasitic patch 102 and the second double - sided parallel parasitic patch 103 excite additional resonance modes through near - field coupling, introducing the second and third resonance points. Superimposed on the main patch resonance frequency, the gain bandwidth of the antenna is broadened. Specifically, since one of the dipole arms 101 is directly connected to the metal floor 400, a radiation null can be introduced at the low - frequency part of the antenna operating frequency band. At the same time, the introduction of two groups of double - sided parallel parasitic patches introduces a second radiation null at the high - frequency part of the antenna operating frequency band. Therefore, the radiation of the antenna has obvious filtering characteristics.

[0023] Since the reflection - free bandwidth of the antenna includes the second - harmonic frequency band of the antenna radiation bandwidth, the influence of the second - harmonic on the antenna performance must be considered. At the second - harmonic of the antenna, both the S - parameter and the gain of the antenna will deteriorate. The S - parameter will be lower than - 10 dB, and the gain will increase significantly, that is, the antenna will radiate outward at the second - harmonic, which does not meet the design requirements. In the structure of the cross - shaped high - low impedance microstrip line 200, the high - impedance line (such as above 50 Ω) and the low - impedance line (such as below 20 Ω) achieve impedance step through the width difference, playing the role of a low - pass filter, thus achieving the effect of harmonic suppression on the antenna and having a significant effect on the out - of - band suppression of the antenna gain.

[0024] The stop - band energy absorption structure 300 converts the stop - band energy of the Yagi - like radiator 100 into heat energy through two pairs of microstrip band - stop filters and a patch resistor, thereby achieving reflection - free in a wide band. Outside the operating frequency band of the antenna, the microstrip band - stop filter is in the on - state, and its impedance can be approximately regarded as 50 Ω. However, when the S - parameter of the antenna is approximately 0, its impedance is not always close to infinity. When the impedance of the antenna is large enough, after connecting the microstrip band - stop filter in parallel, the overall impedance will approach 50 Ω, thus achieving impedance matching. However, when the impedance of the antenna is very small, even 0, after connecting the microstrip band - stop filter in parallel, the overall impedance will only become smaller and cannot achieve the effect of impedance matching. Therefore, one - way microstrip band - stop filters can often only achieve a relatively narrow reflection - free bandwidth. In this embodiment, after connecting one - way microstrip band - stop filters in parallel, a folded phase line 303 is connected in series to shift the overall phase by 180°, so that the impedance of the frequency band with a very small impedance after connecting the single - way microstrip filter in parallel becomes very large after experiencing the phase shift. At this time, connecting the second - way microstrip band - stop filter in parallel can match the impedance of this part of the frequency band, thus achieving a wider reflection - free bandwidth. It should be noted that in addition toFigure 5 In addition to the shown shape, other existing forms of microstrip band-stop filters can also be adopted. As long as the microstrip band-stop filter satisfies the frequency characteristics of the corresponding antenna, that is, the band-pass frequency band of the antenna corresponds to the band-stop frequency band of the microstrip band-stop filter, the effect of no reflection can be achieved.

[0025] In this embodiment, the dielectric plate 500 is made of Rogers RT / duroid 5880 material with a dielectric constant of 2.2 and a loss tangent value of 0.0009. The first patch resistor 305 and the second patch resistor 306 are both 50 Ω. As Figure 6 shown, the non-reflection bandwidth of the antenna in this embodiment is 1 - 10 GHz, and the absolute bandwidth is 164%. The antenna proposed by the present invention has an ultra-wide non-reflection bandwidth. As Figure 7 shown, the maximum gain of the antenna in this embodiment is 6 dBi, and the 3 dB gain bandwidth is 2.8 - 4.7 GHz, with significant out-of-band rejection effect. As Figure 8 、 Figure 9 shown, the radiation pattern of the antenna in this embodiment at 4 GHz shows good end-fire characteristics.

[0026] The broadband non-reflection filtering antenna of the present invention adjusts the operating frequency band by magnifying or reducing the size, so that it operates in the microwave, millimeter-wave or terahertz frequency band.

[0027] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A broadband reflectionless filtering antenna, characterized in that, Comprising: A radiator, two band-stop filters, and a folded microstrip line; each of the two band-stop filters is respectively connected to a grounded patch resistor. The feed port of the antenna is directly connected to one of the band-stop filters, and at the same time is connected to the other band-stop filter and the radiator through the folded microstrip line, that is, the two band-stop filters are respectively connected in parallel at the feed port and the radiator.

2. The broadband reflectionless filtering antenna according to claim 1, characterized in that, The radiator adopts a Yagi-like radiator (100), which includes dipole arms (101), a first double-sided parallel parasitic patch (102), and a second double-sided parallel parasitic patch (103) that are arranged in sequence along the radiation direction and are mutually coupled.

3. The broadband reflectionless filtering antenna according to claim 2, wherein One arm of the dipole arms (101) is located on the upper surface of the dielectric plate (500), and the other arm is located on the lower surface of the dielectric plate (500), and the arm located on the lower surface is connected to the metal floor (400).

4. The broadband reflectionless filtering antenna according to claim 3, wherein The first double-sided parallel parasitic patch (102) and the second double-sided parallel parasitic patch (103) are respectively composed of rectangular metal patches that are located on both sides of the dielectric plate (500) and are offset.

5. The broadband reflectionless filtering antenna according to any one of claims 2-4, characterized in that The input microstrip feed line (304) serving as the feed port is connected to the connection point between the first microstrip band-stop filter (301) and the folded phase line (303); the free end of the first microstrip band-stop filter (301) is connected to one end of the first patch resistor (305), and the other end of the first patch resistor (305) is connected to the metal floor (400) through the first metal via (307); the free end of the second microstrip band-stop filter (302) is connected to one end of the second patch resistor (306), and the other end of the second patch resistor (306) is connected to the metal floor (400) through the second metal via (308).

6. The broadband reflectionless filtering antenna according to any one of claims 2-4, characterized in that, The antenna further includes a cross-shaped high-low impedance microstrip line (200) disposed between the Yagi-like radiator (100) and one of the band-stop filters; the cross-shaped high-low impedance microstrip line (200) is formed by the intersection of a high-impedance line and a low-impedance line that are perpendicular to each other, forming a cross-shaped geometric structure.

7. The broadband reflectionless filtering antenna according to claim 6, wherein In the cross-shaped high-low impedance microstrip line (200), the length and width of the low-impedance line on one side of the cross center are smaller than those of the low-impedance line on the other side.

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