Wideband filtering dipole antenna based on eigenmode cancellation

Abstract

The present invention discloses a broadband filtering dipole antenna based on characteristic mode cancellation, belonging to the field of antenna technology. The antenna includes a radiation structure, a feeding structure, and a dielectric substrate. The radiation structure includes a dipole narrow arm, a dipole wide arm, and a folded dipole arm. A coaxial line feeding method is adopted, and the coaxial line core wire and the outer skin are respectively connected to the dipole narrow arm and the dipole wide arm. The present invention realizes the broadband characteristics of the antenna through the simultaneous resonance of the dipole first-order mode and the folded dipole first-order mode and the third-order mode; outside the working frequency band, the dipole first-order mode is used to cancel the characteristic mode between the folded dipole first-order mode and the third-order mode, and the frequency point where the surface current is the minimum value is obtained at low frequency and high frequency, thereby obtaining the radiation zero point. The antenna has both broadband and filtering characteristics, and has the technical advantages of simple structure, wide working bandwidth, and good filtering characteristics.

Description

Technical Field

[0001] The invention belongs to the technical field of antennas, and in particular relates to a broadband filtering dipole antenna based on characteristic mode cancellation. Background Art

[0002] As a basic antenna type, dipole antennas are combined with multi-mode excitation technology and filtering antenna technology to have broadband and filtering characteristics, becoming a hot topic in antenna technology research. Some scholars have achieved broadband characteristics of 2.94 to 2.39 GHz by loading an electric small ring resonant structure to compress the third-order mode resonance point and shift it to the first-order mode resonance point; and introduced a pair of semicircular rings at the zero point of the third-order mode current to compress the third-order mode, and introduced a pair of L-shaped probes at the zero point of the fifth-order mode current to compress the fifth-order mode, thereby exciting the three modes to achieve broadband working characteristics of 2.75 to 7.43 GHz; some scholars have studied the feeding structure of the even mode and combined it with the odd mode feeding structure, which can simultaneously excite the even mode and the odd mode, expanding the broadband research method of the dipole antenna. However, the dipole structures finally constructed in the above studies are relatively complex. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a broadband filtering dipole antenna based on characteristic mode cancellation. The broadband characteristics of the antenna are achieved by the simultaneous resonance of the dipole first-order mode and the folded dipole first-order mode and third-order mode; outside the working frequency band, the dipole first-order mode is used to cancel the characteristic modes between the folded dipole first-order mode and the third-order mode, and the surface current is obtained at low and high frequencies. The frequency point of the current minimum value is obtained, and then the radiation zero point is obtained. The antenna has both broadband and filtering characteristics, and has the technical advantages of simple structure, wide working bandwidth, and good filtering characteristics.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0005] A broadband filtering dipole antenna based on characteristic mode cancellation, the antenna comprising a radiation structure, a feeding structure, and a dielectric substrate, wherein:

[0006] The radiation structure is located on a dielectric substrate, and includes a dipole narrow arm, a dipole wide arm, and a folded dipole arm; the dipole narrow arm and the dipole wide arm form a dipole, and the folded dipole arm is connected to the dipole wide arm to form a folded dipole; the dipole narrow arm and the folded dipole arm are arranged in parallel;

[0007] The feeding structure adopts a coaxial line feeding method, wherein the core wire and the outer sheath of the coaxial line are respectively connected to the narrow arm of the dipole and the wide arm of the dipole.

[0008] Furthermore, the wide dipole arm is rectangular, the narrow dipole arm is L-shaped, and the folded dipole arm is bent; wherein the width of the narrow dipole arm is smaller than the width of the wide dipole arm.

[0009] Furthermore, the L-shaped long side of the dipole narrow arm is close to the dipole wide arm.

[0010] Furthermore, the folded dipole arm is S-shaped or serpentine-shaped.

[0011] Furthermore, the head end of the bent structure of the folded dipole arm is connected to the dipole wide arm, and the tail end is open.

[0012] Furthermore, the bent structure of the folded dipole arm is a concave shape with an opening on the right side.

[0013] Furthermore, the size of the dipole wide arm covers half of the dielectric substrate.

[0014] Furthermore, the antenna includes three characteristic modes, and the characteristic fields corresponding to the three characteristic modes are all dipole standard fields.

[0015] Furthermore, at the resonant frequency, the three characteristic modes of the antenna correspond to the first-order mode of the folded dipole, the first-order mode of the dipole, and the third-order mode of the dipole, respectively.

[0016] On the other hand, the present invention provides an electronic device, comprising the aforementioned broadband filtering dipole antenna based on characteristic mode cancellation.

[0017] The beneficial effects of the present invention are:

[0018] (1) The present invention completes the design of a broadband filtering dipole antenna based on characteristic mode cancellation. On the basis of realizing broadband characteristics by simultaneously resonating three modes, a filtering characteristic design method based on characteristic mode cancellation is proposed, the basic principle of realizing filtering characteristics by characteristic mode cancellation is demonstrated, and the design principle of the antenna is revealed;

[0019] (2) The present invention utilizes the simultaneous resonance of the dipole first-order mode and the folded dipole first-order mode and third-order mode to achieve a wideband characteristic of 590 MHz to 960 MHz;

[0020] (3) The present invention does not require additional circuits. It utilizes the characteristic mode cancellation of the dipole first-order mode and the folded dipole first-order mode at low frequencies to obtain a surface current minimum point of 520 MHz, thereby obtaining a radiation zero point at low frequencies. It utilizes the mode cancellation of the dipole first-order mode and the folded dipole third-order mode at high frequencies to obtain a surface current minimum point of 1080 MHz, thereby obtaining a radiation zero point at high frequencies. The antenna completes the filtering characteristic design while having wide-band characteristics.

[0021] (4) The antenna has the technical advantages of simple structure, wide working bandwidth and good filtering characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The structure diagram of the broadband filtering dipole antenna based on characteristic mode cancellation is shown in FIG.

[0023] Figure 2 Schematic diagram of dipole mode characteristics and characteristic fields;

[0024] Figure 3 It is a schematic diagram of the characteristic current of the first-order mode of the dipole;

[0025] Figure 4 Schematic diagram of the folded dipole mode characteristics and characteristic fields;

[0026] Figure 5 It is a schematic diagram of characteristic current of the first-order mode and the third-order mode of the folded dipole;

[0027] Figure 6 Schematic diagram of antenna mode weight coefficient amplitude and characteristic field of the present invention;

[0028] Figure 7 A phase diagram of antenna mode weight coefficients of the present invention;

[0029] Figure 8 It is a schematic diagram of the first mode and second mode current of the antenna of the present invention at 520MHz;

[0030] Fig. 9 It is a schematic diagram of the second mode and third mode current of the antenna of the present invention at 1080MHz;

[0031] Fig.10 A schematic diagram of simulation of antenna impedance and gain characteristics of the present invention;

[0032] Fig.11 It is a simulation diagram of the E-plane and H-plane radiation patterns of the antenna of the present invention at different frequencies. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0034] The object of the present invention is to provide a broadband filtering dipole antenna based on characteristic mode cancellation, and the broadband characteristics of the antenna are realized by simultaneous resonance of the dipole first-order mode and the folded dipole first-order mode and the third-order mode; by utilizing the mode cancellation of the dipole first-order mode and the folded dipole first-order mode and the third-order mode, the frequency points at which the surface current is the current minimum are obtained at low frequencies and high frequencies respectively, and then the radiation zero point is obtained, and the antenna has both broadband and filtering characteristics.

[0035] like Figure 1 As shown in the figure, the overall structure of the broadband filtering dipole antenna based on characteristic mode cancellation mainly includes:

[0036] The radiation structure is located on the upper surface of the dielectric substrate, and includes a dipole narrow arm, a dipole wide arm, and a folded dipole arm; wherein the dipole narrow arm and the dipole wide arm form a dipole, and the folded dipole arm is connected to the dipole wide arm to form a folded dipole; the dipole narrow arm and the folded dipole arm are arranged in parallel;

[0037] The feeding structure adopts a coaxial line feeding method, and the core wire and outer sheath of the coaxial line are respectively connected to the narrow arm and wide arm of the dipole;

[0038] The dielectric substrate is used to support the radiation structure. It uses Rogers 5880 with a thickness of 1.6 mm and a dielectric constant of 2.2.

[0039] like Figure 1 As shown, in one embodiment, the length and width of the simple broadband filtering dipole antenna structure are 180mm×25mm; the dipole wide arm covers half of the dielectric substrate; the dipole narrow arm is L-shaped, with a width of 4mm, and the length includes: 78mm in length along the z direction and 12.5mm in length along the -x direction; the dipole wide arm and the dipole narrow arm are arranged at both ends of the feeding structure to form a dipole, and are respectively connected to the coaxial core wire and the outer skin; the folded dipole arm is bent, and is arranged in parallel with the dipole narrow arm at an interval of 3cm, and the folded dipole arm has a width of 2mm, and the length includes: 80mm in length along the z direction, 6mm in length along the x direction, and 74mm in the -z direction; the folded dipole arm is connected to the dipole wide arm to form a folded dipole;

[0040] like Figure 2-Figure 3 As shown, the dipole has a resonant mode in the frequency range of 400MHz to 1200MHz, the resonant frequency of this mode is 730MHz, and the corresponding characteristic field is the standard dipole field; the characteristic current corresponding to the dipole resonant mode is sinusoidally distributed, and there is a current maximum and a current minimum on the narrow arm of the dipole, which shows that this mode is the first-order mode of the dipole, that is, the half-wave oscillator mode;

[0041] like Figure 4 As shown in the figure, within the frequency range of 400MHz to 1200MHz, the equivalent dipole has two resonance modes, with corresponding resonance frequencies of 590MHz and 920MHz respectively. The characteristic fields corresponding to the two resonance modes are both standard dipole fields. Figure 5 As shown in (a), the characteristic current of the first resonant mode of the folded dipole is sinusoidally distributed, and there is a current maximum and a current minimum on the folded dipole arm. This characteristic mode is the first-order mode of the folded dipole, that is, the half-wave oscillator mode. Figure 5As shown in (b), the characteristic current of another resonant mode of the folded dipole has two zero points and two maximum values ​​on the folded dipole arm, so the characteristic mode is the third-order mode of the folded dipole;

[0042] like Figure 6 As shown, the antenna of the present invention has three characteristic modes excited simultaneously, which are respectively recorded as the first mode, the second mode, and the third mode. The characteristic fields corresponding to the three characteristic modes are all dipole standard fields; the first mode of the antenna is the first-order mode of the folded dipole, the second mode is the first-order mode of the dipole, and the third mode is the third-order mode of the folded dipole; by combining the above three modes, the antenna can achieve wide-band characteristics;

[0043] According to the characteristic mode theory, the surface current of the antenna can be expressed as:

[0044]

[0045] in, The antenna The mode weight coefficient of the characteristic mode; The antenna The characteristic current of each characteristic mode; is the characteristic mode number of the antenna; |·| is the amplitude; i· is the phase;

[0046] like Figure 6 As shown, when the frequency is lower than 720 MHz, the amplitude of the mode weight coefficient of the 3rd mode approaches to 0, that is, the contribution of the 3rd mode to the surface current of the antenna approaches to 0. Therefore, in the frequency range lower than 600 MHz, the surface current of the antenna is mainly composed of the characteristic currents of the 1st mode and the 2nd mode; when the frequency is higher than 720 MHz, the amplitude of the mode weight coefficient of the 1st mode approaches to 0, that is, the contribution of the 1st mode to the surface current of the antenna approaches to 0. Therefore, in the frequency range higher than 900 MHz, the surface current of the antenna is mainly composed of the characteristic currents of the 2nd mode and the 3rd mode.

[0047] like Figure 7 As shown, in the frequency range below 550 MHz, the mode weight coefficients of the first mode and the second mode of the antenna are in anti-phase; in the frequency range above 1050 MHz, the mode weight coefficients of the second mode and the third mode of the antenna are in phase;

[0048] like Figure 8 As shown in (a), at a frequency of 520 MHz, the characteristic current of the first mode of the antenna is mainly distributed on the folded dipole arm; Figure 8 As shown in (b), at a frequency of 520 MHz, the characteristic current of the second mode of the antenna is mainly distributed on the folded dipole arm;

[0049] At a frequency of 520 MHz, the characteristic currents of the first mode and the second mode of the antenna are mainly distributed on the folded dipole arm, and the two characteristic currents are in phase; at this time, the characteristic current of the first mode of the antenna is the characteristic current of the first-order characteristic mode of the folded dipole, and the characteristic current of the second mode is the characteristic current of the first-order characteristic mode of the dipole coupled to the first-order characteristic mode of the folded dipole;

[0050] According to the characteristic mode theory, in the frequency range below 550 MHz, by substituting the mode weight coefficients of the first mode and the second mode of the antenna and the phase relationship of the characteristic current, the surface current of the antenna can be expressed as:

[0051]

[0052] When the mode weight coefficients and characteristic current amplitudes of the first mode and the second mode make the surface current of the antenna have a minimum value at a certain frequency point lower than 550 MHz, the antenna can form a radiation zero point at this frequency point;

[0053] like Fig. 9 As shown in (a), at a frequency of 1080 MHz, the characteristic current of the second mode of the antenna is mainly distributed on the folded dipole arm; Fig. 9 As shown in (b), at a frequency of 1080 MHz, the characteristic current of the third mode of the antenna is mainly distributed on the folded dipole arm;

[0054] At a frequency of 1080 MHz, the characteristic currents of the second mode and the third mode of the antenna are mainly distributed on the folded dipole arm, and the two characteristic currents are in antiphase; at this time, the characteristic current of the second mode of the antenna is the characteristic current of the first-order characteristic mode of the dipole coupled to the third-order characteristic mode of the folded dipole, and the characteristic current of the third mode is the characteristic current of the third-order characteristic mode of the folded dipole;

[0055] According to the characteristic mode theory, in the frequency range above 1050 MHz, by substituting the mode weight coefficients of the second mode and the third mode of the antenna and the phase relationship of the characteristic current, the surface current of the antenna can be expressed as:

[0056] ,

[0057] When the mode weight coefficients and characteristic current amplitudes of the second mode and the third mode make the surface current of the antenna have a minimum value at a certain frequency point higher than 1050 MHz, the antenna can form a radiation zero point at this frequency point;

[0058] In summary, within the frequency range below 550 MHz, the characteristic currents of the first mode and the second mode of the antenna are mainly distributed on the folded dipole arm, and both appear as characteristic currents of the first-order characteristic mode of the folded dipole, and the two characteristic currents have the same phase, and the mode weight coefficients of the first mode and the second mode of the antenna have opposite phases; combined with the relationship between the characteristic currents and the amplitude of the mode weight coefficients of the first mode and the second mode, the antenna has the condition of a minimum surface current at a certain frequency point below 550 MHz, and a radiation zero point can be generated; within the frequency range above 1050 MHz The characteristic currents of the second and third modes of the antenna are mainly distributed on the folded dipole arms, and both are characterized by the characteristic currents of the third-order characteristic mode of the folded dipole, and the two characteristic currents are in opposite phases. The mode weight coefficients of the second and third modes of the antenna are in the same phase. Combined with the characteristic currents of the second and third modes and the amplitude relationship of the mode weight coefficients, the antenna has the condition of a minimum surface current at a certain frequency point higher than 1050MHz, and a radiation zero point can be generated; combined with the two radiation zero points of high frequency and low frequency, the antenna can achieve filtering characteristics based on a wide working frequency band;

[0059] like Fig.10 As shown in (a), the antenna is in the frequency range of 590MHz to 960MHz, |S 11 |Less than -10dB; Fig.10 As shown in (b), the antenna has a gain greater than 2.9dBi and a gain fluctuation less than 1.1dB in the frequency range of 590MHz to 960MHz; at the frequencies of 520MHz and 1080MHz, the radiation zero-point gain is as low as -20.7dBi;

[0060] like Fig.11 As shown in (a), within the frequency range of 590 MHz to 960 MHz, the antenna has a good "∞"-shaped E-plane radiation pattern, with a radiation zero point at 520 MHz and 1080 MHz respectively; Fig.11 As shown in (b), within the frequency range of 590 MHz to 960 MHz, the antenna has a good "o"-shaped H-plane radiation pattern, and has a radiation zero point at a frequency of 520 MHz and 1080 MHz, respectively.

[0061] On the other hand, the present invention provides an electronic device, comprising the aforementioned broadband filtering dipole antenna based on characteristic mode cancellation.

[0062] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A broadband filtering dipole antenna based on characteristic mode cancellation, characterized in that: The antenna comprises a radiation structure, a feeding structure, and a dielectric substrate, wherein: The radiation structure is located on a dielectric substrate, and includes a dipole narrow arm, a dipole wide arm, and a folded dipole arm; the dipole narrow arm and the dipole wide arm form a dipole, and the folded dipole arm is connected to the dipole wide arm to form a folded dipole; the dipole narrow arm and the folded dipole arm are arranged in parallel; The feeding structure adopts a coaxial line feeding method, in which the core wire of the coaxial line is connected to the narrow arm of the dipole, and the outer sheath of the coaxial line is connected to the wide arm of the dipole; The antenna includes three characteristic modes, which correspond to the folded dipole first-order mode, the dipole first-order mode, and the folded dipole third-order mode respectively. The dipole first-order mode cancels out the characteristic mode of the folded dipole first-order mode at a low frequency to obtain a surface current minimum point of 520 MHz, and then obtains a radiation zero point at a low frequency; the dipole first-order mode cancels out the characteristic mode of the folded dipole third-order mode at a high frequency to obtain a surface current minimum point of 1080 MHz, and then obtains a radiation zero point at a high frequency.

2. A broadband filtering dipole antenna based on characteristic mode cancellation according to claim 1, characterized in that: The wide dipole arm is rectangular, the narrow dipole arm is L-shaped, and the folded dipole arm is bent; wherein the width of the narrow dipole arm is smaller than the width of the wide dipole arm.

3. A broadband filtering dipole antenna based on characteristic mode cancellation according to claim 1, characterized in that: The L-shaped long side of the dipole narrow arm is close to the dipole wide arm.

4. A broadband filtering dipole antenna based on characteristic mode cancellation according to claim 1, characterized in that: The folded dipole arm is S-shaped or serpentine-shaped.

5. A broadband filtering dipole antenna based on characteristic mode cancellation according to claim 1, characterized in that: The bent structure of the folded dipole arm has a head end connected to the dipole wide arm and an open-circuit tail end.

6. A broadband filtering dipole antenna based on characteristic mode cancellation according to claim 5, characterized in that: The bent structure of the folded dipole arm is in a concave shape with an opening on the right side.

7. A broadband filtering dipole antenna based on characteristic mode cancellation according to claim 1, characterized in that: The dipole wide arm has a size covering half of the dielectric substrate.

8. The broadband filtering dipole antenna based on characteristic mode cancellation according to claim 1, characterized in that: The characteristic fields corresponding to the three characteristic modes are all dipole standard fields.

9. An electronic device, characterized in that: It comprises a broadband filtering dipole antenna based on characteristic mode cancellation as described in any one of claims 1 to 8.

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