A tunable slot antenna and a multi-band antenna system

Abstract

The present invention provides a tunable slot antenna and a multi-band antenna system, the multi-band antenna system includes a tunable slot antenna. The tunable slot antenna includes a tuning cavity, a tuning column and a feeding cavity, the tuning cavity, the tuning column and the feeding cavity are all made of metal materials, the tuning cavity includes a first panel, a second panel and a side wall, the first panel, the second panel and the side wall enclose a resonant cavity, the first panel has a radiation slot, the second panel has a feeding slot, the tuning column is connected to the side wall and one end extends into the resonant cavity, the length of the tuning column extending into the resonant cavity can be adjusted, the feeding cavity is connected to the side of the second panel away from the first panel, the feeding cavity surrounds the feeding slot, the feeding cavity is connected to a coaxial feeding terminal, and the central feeding line of the coaxial feeding terminal extends into the feeding cavity. The slot antenna of this scheme has the characteristics of tunability, low loss, high efficiency, high power handling capability and good reliability, and is suitable for multi-band wireless communication systems.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless communications, and in particular relates to a tunable slot antenna and a multi-band antenna system. Background Art

[0002] Reconfigurable microwave circuits and antennas have received extensive attention in the development of modern communication systems due to their multi-band and multi-operating mode characteristics. Among them, the transmission and reception of wireless signals place high demands on reconfigurable antennas. For reconfigurable antennas in related technologies, such as some microstrip antennas and SIW (Substrate integrated waveguide) slot antennas, electronic control devices are required for tuning.

[0003] However, these reconfigurable antennas based on electronic devices often have problems such as low power handling capability, low radiation efficiency, and high noise interference, and still have certain limitations for the construction of multi-band mobile wireless communication systems. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a tunable slot antenna and a multi-band antenna system, which have the characteristics of tunability, low loss, high efficiency, high power handling capability, and good reliability, and are suitable for application in multi-band wireless communication systems.

[0005] To solve the above technical problems, the present invention is implemented as follows: a tunable slot antenna is provided, comprising a tuning cavity, a tuning column and a feeding cavity, wherein the tuning cavity, the tuning column and the feeding cavity are all made of metal materials, the tuning cavity comprises a first panel, a second panel opposite to the first panel and a side wall connected between the first panel and the second panel, the first panel, the second panel and the side wall enclose a resonant cavity, the first panel has a radiation slot, the second panel has a feeding slot, the tuning column is connected to the side wall and one end extends into the resonant cavity, the length of the tuning column extending into the resonant cavity can be adjusted, the feeding cavity is connected to the side of the second panel away from the first panel, the feeding cavity surrounds the feeding slot, the feeding cavity is connected to a coaxial feeding terminal, and the central feeding line of the coaxial feeding terminal extends into the feeding cavity.

[0006] Furthermore, the first panel and the second panel are parallel to each other, the length direction of the radiation slot is parallel to the length direction of the feeding slot, and the length direction of the tuning column is parallel to the plate surface of the first panel and perpendicular to the length direction of the radiation slot.

[0007] Furthermore, the ratio of the length of the radiation slot to the width of the radiation slot is 2.00-6.00, the ratio of the length of the feeding slot to the width of the feeding slot is 3.50-8.00, and the ratio of the length of the radiation slot to the length of the feeding slot is 0.60-0.95.

[0008] Furthermore, the center of the radiation slot and the center of the feeding slot are opposite to each other, and the plane where the center line of the tuning column and the center line of the central feeding line are located passes through the center of the radiation slot and the center of the feeding slot.

[0009] Furthermore, the ratio of the adjustable length of the tuning column extending into the resonant cavity to the width of the resonant cavity in the length direction of the tuning column is 0-0.5.

[0010] Furthermore, the first panel and the second panel are parallel to each other, an angle is formed between the length direction of the radiation slot and the length direction of the feeding slot, an extension direction of the central feed line is perpendicular to the length direction of the feeding slot, a first tuning column and a second tuning column are connected to the side wall, the length directions of the first tuning column and the second tuning column are parallel to the first panel, an angle is formed between the first tuning column and the second tuning column, and an angle is formed between the first tuning column and the second tuning column.

[0011] Furthermore, the ratio of the length of the radiation slot to the width of the radiation slot is 1.50-8.00, the ratio of the length of the feeding slot to the width of the feeding slot is 2-15, and the ratio of the length of the radiation slot to the length of the feeding slot is 0.60-0.95.

[0012] Furthermore, the centers of the radiation slot and the feeding slot are facing each other, the angle between the radiation slot and the feeding slot is 90°, the first tuning column and the second tuning column are perpendicular to each other, and the angle between the first tuning column and the length direction of the radiation slot and the angle between the second tuning column and the length direction of the radiation slot are both 45°.

[0013] Furthermore, the central feed line is parallel to the panel surface of the second panel, and the central feed line is perpendicular to the length direction of the feed slot.

[0014] Furthermore, a multi-band antenna system is provided, comprising any one of the tunable slot antennas described above.

[0015] Compared with the prior art, the tunable slot antenna and multi-band antenna system of the present invention have the following beneficial effects:

[0016] The signal can be fed into the feeding slot through the coaxial feeding terminal and the feeding cavity. The resonant frequency of the resonant cavity can be tuned by adjusting the length of the tuning column extending into the resonant cavity. Finally, the signal can be radiated through the radiation slot. The tunable slot antenna of this scheme has the characteristics of tunability, low loss, high efficiency, high power handling capability, and good reliability, and is suitable for application in multi-band wireless communication systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a tunable single-frequency antenna in the first implementation of the embodiment of the present invention, (a) three-dimensional view; (b) xz plane side view; (c) yz plane side view;

[0018] Figure 2 The tunable single-frequency antenna in the first implementation of the embodiment of the present invention uses tuning rods of different lengths to simulate "S11";

[0019] Figure 3 1 is the field distribution of the tunable single-frequency antenna in the first implementation of the embodiment of the present invention (E field in the AA' plane and H field in the BB' plane); (a) and (b): E field and H field at 3.595 GHz when L4 = 0; (c) and (d) E field and H field at 3.477 GHz when L4 = 10 mm;

[0020] Figure 4 is an equivalent circuit model of a tunable single-frequency antenna in a first implementation manner of an embodiment of the present invention;

[0021] Figure 5 is the relationship between the resonant frequency of the tunable single-frequency antenna and the length of the metal column in the first implementation manner of the embodiment of the present invention;

[0022] Figure 6 is the relationship between the influence of (a) the radius of the tuning post and (b) the position offset of the tuning post on the resonant frequency of the tunable single-frequency antenna in the first implementation manner of the embodiment of the present invention;

[0023] Figure 7 The following are the effects of the radiation slot and the feeding slot of the tunable single-frequency antenna on the resonant frequency in the first implementation of the embodiment of the present invention: (a) the radiation slot length L1; (b) the feeding slot length L2;

[0024] Figure 8 is a performance simulation result of a tunable single-frequency antenna in the first implementation manner of an embodiment of the present invention;

[0025] Fig. 9 The radiation pattern simulation of the tunable single-frequency antenna in the first implementation of the embodiment of the present invention is as follows: (a) radiation pattern on the xz plane; (b) radiation pattern on the yz plane;

[0026] Fig.10 Schematic diagram of a tunable dual-frequency antenna structure in a second implementation of an embodiment of the present invention: (a) a three-dimensional view; (b) a top view;

[0027] Fig.11 The simulation results of the tunable dual-frequency antenna in the second implementation of the embodiment of the present invention are as follows: (a) the electric field distribution of the |S11| and |S11| modes in the cavity is simulated; (b) the electric field distribution of the TE101 mode radiation slot at 3.553 GHz; (c) the electric field distribution of the TE011 mode radiation slot at 3.876 GHz;

[0028] Fig.12 is an equivalent circuit model of a tunable dual-frequency antenna in a second implementation manner of an embodiment of the present invention;

[0029] Fig.13 It is a simulation "S11" of the first tuning column (a) and the second tuning column (b) with different lengths for the tunable dual-frequency antenna in the second implementation of the embodiment of the present invention;

[0030] Fig.14 The final simulation results of the tunable dual-frequency antenna in the second implementation of the embodiment of the present invention are: (a) |S11|, (b) variable length first tuning column, achieved gain under L4; (c) |S11|, (d) variable length second tuning column, achieved gain under L5;

[0031] Fig.15 1 is the radiation pattern of different frequency bands of the tunable dual-frequency antenna in different directions in the second implementation of the embodiment of the present invention: (a) xz plane of frequency band 1; (b) yz plane of frequency band 1; (c) xz plane of frequency band 2; (d) yz plane of frequency band 2;

[0032] Fig.16 is the initial performance of the tunable broadband slot antenna in the third implementation of the embodiment of the present invention, at which the lengths of the first tuning column and the second tuning column extending into the resonant cavity are both 0;

[0033] Fig.17 The following are photos of the experimental device for testing the tunable slot antenna in the embodiment of the present invention: (a) S parameters; (b) far-zone radiation;

[0034] Fig.18 The simulation and measurement results of the tunable broadband slot antenna in the third implementation of the embodiment of the present invention with different parameter settings of the first tuning column and the second tuning column are as follows: (a) |S11|; (b) achieved gain; (c) total efficiency;

[0035] Fig.191 are the radiation patterns measured and simulated on the E-plane and the H-plane of the tunable broadband slot antenna in the third implementation of the embodiment of the present invention: (a) and (b) are 3.735 GHz for parameter setting I; (c) and (d) are 3.62 GHz for parameter setting II; (e) and (f) are 3.5 GHz for parameter setting III;

[0036] Fig. 20 is a return loss test result of the tunable broadband slot antenna under different parameter settings of the first tuning column and the second tuning column in the third implementation manner of the embodiment of the present invention;

[0037] Fig.21 Table 1 is a result of studying the tunable broadband slot antenna with a constant FBW in the third implementation of the embodiment of the present invention;

[0038] Fig. 22 Table 2 is a result of studying the tunable broadband slot antenna with a constant center frequency in the third implementation of the embodiment of the present invention.

[0039] In the accompanying drawings, the reference numerals represent: 1, tuning cavity; 11, radiation slot; 12, feeding slot; 13, side wall; 2, tuning column; 21, first tuning column; 22, second tuning column; 3, feeding cavity; 31, coaxial feeding terminal; 311, center feeding line. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0041] Example:

[0042] In this embodiment, a multi-band antenna system is provided, including a tunable slot antenna, wherein Figure 1 and Fig.10The tunable slot antenna includes a tuning cavity 1, a tuning column 2 and a feeding cavity 3. The tuning cavity 1, the tuning column 2 and the feeding cavity 3 are all made of metal materials. The tuning cavity 1 includes a first panel, a second panel opposite to the first panel and a side wall 13 connected between the first panel and the second panel. The first panel, the second panel and the side wall 13 enclose a resonant cavity. The first panel has a radiation slot 11, and the second panel has a feeding slot 12. The tuning column 2 is connected to the side wall 13 and one end extends into the resonant cavity. The length of the tuning column 2 extending into the resonant cavity can be adjusted. The feeding cavity 3 is connected to the side of the second panel away from the first panel. The feeding cavity 3 surrounds the feeding slot 12. The feeding cavity 3 is connected to a coaxial feeding terminal 31, and the central feeding line 311 of the coaxial feeding terminal 31 extends into the feeding cavity 3.

[0043] The signal can be fed into the feeding slot 12 through the coaxial feeding terminal 31 and the feeding cavity 3. The resonant frequency of the resonant cavity can be tuned by adjusting the length of the tuning column 2 extending into the resonant cavity. Finally, the signal can be radiated through the radiation slot 11. The tunable slot antenna of this solution has the characteristics of tunability, low loss, high efficiency, high power handling capability, and good reliability, and is suitable for application in multi-band wireless communication systems.

[0044] In a first implementation of this embodiment, a tunable single-frequency antenna is provided:

[0045] The first panel and the second panel are parallel to each other, the length direction of the radiation slot 11 is parallel to the length direction of the feeding slot 12, the length direction of the tuning column 2 is parallel to the plate surface of the first panel and perpendicular to the length direction of the radiation slot 11; the ratio of the length of the radiation slot 11 to the width of the radiation slot 11 is 2.00-6.00, the ratio of the length of the feeding slot 12 to the width of the feeding slot 12 is 3.50-8.00, and the ratio of the length of the radiation slot 11 to the length of the feeding slot 12 is 0.60-0.95; the center of the radiation slot 11 and the center of the feeding slot 12 are directly opposite, and the plane where the center line of the tuning column 2 and the center line of the central feed line 311 are located passes through the center of the radiation slot 11 and the center of the feeding slot 12; the ratio of the adjustable length of the tuning column 2 extending into the resonant cavity to the width of the resonant cavity in the length direction of the tuning column 2 is 0-0.5; the central feed line 311 Parallel to the surface of the second panel, the central feeding line 311 is perpendicular to the length direction of the feeding slot 12 .

[0046] Specifically, in the present implementation, preferably, the tuning cavity 1 and the feeding cavity 3 are both rectangular parallelepiped structures and their length directions are parallel, the resonant cavity is rectangular parallelepiped, and the centers of the tuning cavity 1 and the feeding cavity 3 are facing each other, wherein the length a of the resonant cavity is 64 mm, the width b of the resonant cavity is 60 mm, the height c of the resonant cavity is 46 mm, the inner cavity length p of the feeding cavity 3 is 50 mm, the inner cavity width q of the feeding cavity 3 is 32 mm, the inner cavity height s of the feeding cavity 3 is 25 mm, the length L1 of the radiation slot 11 is 35 mm, the width W1 of the radiation slot 11 is 12 mm, and the feeding slot 12 is 16 mm. The length L2=38mm, the width W2=8mm of the feeding slot 12, the length L3=24.5mm of the center feeding line 311 extending into the feeding cavity 3, the distance D1=23mm between the axis of the tuning column 2 and the top of the resonant cavity, the distance D2=7mm between the axis of the center feeding line 311 and the second panel, the radius r=3mm of the tuning column 2, the thickness t1=5mm of the first panel, and the thickness t2=3 of the second panel. It should be understood that the parameters of the aforementioned single-frequency antenna are only an example. In practical applications, in order to obtain a suitable tuning frequency band range, the parameters can be adaptively adjusted as needed: for example, the shapes of the tuning cavity 1 and the feeding cavity 3 can be adjusted simultaneously or separately to a cylindrical shape, a pentagonal prism shape, a hexagonal prism shape, etc., and the inner cavities of the tuning cavity 1 and the feeding cavity 3 can be changed correspondingly with their respective shapes; when the tuning cavity 1 and the feeding cavity 3 are both rectangular parallelepiped structures, the length a of the resonant cavity can be selected within 20mm-150mm, for example, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm, 55mm, 60mm, 65mm, 70mm, 75mm, 80mm, 85mm, 90mm, 95mm, 100mm, 105mm, 110mm, 115mm, 120mm, 125mm, 130mm, 135mm, 140mm, 145mm, etc., and, with reference to the aforementioned preferred scheme, the ratio of the dimensions of the remaining parameters to the length a of the resonant cavity can float up and down, and the floating ratio can be between 0-50%, for example, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, etc., taking the length a of the resonant cavity as 128mm, and the ratio of the width b of the resonant cavity to the length a of the resonant cavity floating by 10% as an example, b can be set to 128*(60 / 64)*(1+10%)=132mm, and other parameters can be adaptively set according to this method, which will not be repeated here.

[0047] The following will be a design analysis of the tunable single-frequency antenna solution. Figure 2The simulated return loss |S11| is shown when tuning column 2 is not set and is set. It can be seen that due to the presence of tuning column 2, the resonant frequency of cavity mode TE101 shifts to a lower frequency. In order to clearly understand the influence of tuning column 2, Figure 3 The electric and magnetic field distributions at two frequencies are given. Figure 3 (a) and (b) show that when the tuning column 2 does not extend into the resonant cavity, the electric field (E-field) is completely along the y-axis, and the magnetic field (H-field) is annular in the xz plane, with zero in the middle. Figure 3 As shown in (c) and (d), as the tuning column 2 extends into the resonant cavity, the electric field is still along the y-axis direction, with a small inflection point around the tuning column 2, while the magnetic field in the middle becomes stronger. This means that the tuning column 2 has almost no effect on the electric field, but has a great effect on the magnetic field. Therefore, the tuning column 2 can generate an inductive load on the TE101 mode.

[0048] like Figure 4 As shown, the overall equivalent circuit model of the proposed tunable single-frequency antenna can be established, Cr1 and Lr1 represent the LC resonator model of the original TE101 mode, Cf1 and Cs1 represent the capacitive loads of the feeding slot 12 and the radiation slot 11, and Lp1 represents the inductive load of the tuning column 2. Here, Lp1 can be regarded as a tunable parameter, and the tunable Lp1 can be obtained by adjusting the length of the tuning column 2 extending into the resonant cavity, and its tunable frequency f1 satisfies formula (1):

[0049] (1)

[0050] Figure 5 The resonant frequency of the cavity mode TE101 at different lengths (L4) of the tuning column 2 is shown. The length of the tuning column 2 extending into the resonant cavity increases the inductive load parameter, that is, the inductance Lp1, L4 increases from 0 to 20 mm, which reduces the resonant frequency of the cavity mode TE101 from 3.61 GHz to 2.68 GHz. Therefore, this method has good feasibility in the design of tunable single-frequency antennas.

[0051] The frequency shift increment mainly depends on the load inductance. In addition to the length of the tuning column 2 extending into the resonant cavity, the radius of the tuning column 2 and the offset from the position of the aforementioned exemplary solution will also affect the frequency shift. Figure 6 As shown in (A), the larger radius of the tuning post 2 produces a larger load inductance, thereby producing a larger frequency shift. Figure 6As shown in (b), a larger offset produces a smaller frequency offset, which means that the tuning column 2 placed in the center can produce the largest disturbance. Therefore, the radius of the tuning column 2 can be set adaptively, and the radius r of the tuning column 2 can be set to 1-10mm. In addition to the radius examples shown in the table, the radius r of the tuning column 2 can also be 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, etc.; in this embodiment, the tuning column 2 is cylindrical. In some embodiments, the tuning column 2 can be in the shape of a quadrangular prism, a pentagonal prism, etc. The cross-sectional dimensions of the tuning column 2 set in the above manner are the same. In some embodiments, in order to facilitate tuning, the tuning column 2 can also be set to a cone, a truncated cone, a quadrangular pyramid, a quadrangular pyramid, a pentagonal pyramid, a pentagonal pyramid, etc., that is, the cross-sectional dimension of the tuning column 2 near the end extending into the resonant cavity is smaller than the cross-sectional dimension near the side wall 13.

[0052] According to formula (1), it can be concluded that as the size of the radiation slot 11 and the feeding slot 12 increases, the capacitive loads of Cs1 and Cf1 increase and the resonant frequency f1 decreases. Here, the influence of the length of the radiation slot 11 and the length of the feeding slot 12 is discussed, such as Figure 7 As shown, it can be seen that as the gap length increases, the resonant frequency decreases.

[0053] Then, a tunable single-frequency antenna was designed. In practical applications, impedance matching is the main factor affecting the tuning range. The antenna uses the trial error method to achieve good impedance matching and achievable tuning range. Then, the final simulation results of the single-frequency antenna are obtained, such as Figure 8 As shown, the achievable tuning range for 10db return loss is 3.6 GHz to 3.14 GHz. fH and fL are the highest and lowest center frequencies respectively, and the frequency tuning percentage calculation formula can be:

[0054] (2)

[0055] The frequency tuning percentage of the tunable single-frequency antenna of this solution is 13.6%. Fig. 9 The simulation of the radiation pattern is shown, and it can be seen that the tunable single-frequency antenna of the present scheme has stable radiation performance within the tuning range.

[0056] In a second implementation of this embodiment, a tunable dual-frequency antenna is provided:

[0057] The first panel and the second panel are parallel to each other, there is an angle between the length direction of the radiation slot 11 and the length direction of the feeding slot 12, the extension direction of the central feed line 311 is perpendicular to the length direction of the feeding slot 12, the side wall 13 is connected with the first tuning column 21 and the second tuning column 22, the length directions of the first tuning column 21 and the second tuning column 22 are parallel to the first panel, there is an angle between the first tuning column 21 and the second tuning column 22, and there is an angle between the first tuning column 21 and the second tuning column 22. Preferably, the ratio of the length of the radiation slot 11 to the width of the radiation slot 11 is 1.50-8.00, the ratio of the length of the feeding slot 12 to the width of the feeding slot 12 is 2-15, and the ratio of the length of the radiation slot 11 to the length of the feeding slot 12 is 0.60-0.95; the centers of the radiation slot 11 and the feeding slot 12 are directly opposite, the angle between the radiation slot 11 and the feeding slot 12 is 90°, the first tuning column 21 and the second tuning column 22 are perpendicular to each other, and the angle between the first tuning column 21 and the length direction of the radiation slot 11 and the angle between the second tuning column 22 and the length direction of the radiation slot 11 are both 45°; the central feed line 311 is parallel to the board surface of the second panel, and the central feed line 311 is perpendicular to the length direction of the feeding slot 12.

[0058] Specifically, in the present implementation, preferably, the tuning cavity 1 and the feeding cavity 3 are both rectangular parallelepiped structures and their length directions are perpendicular to each other, the resonant cavity is rectangular parallelepiped, and the centers of the tuning cavity 1 and the feeding cavity 3 are facing each other, wherein the length a of the resonant cavity is 74 mm, the width b of the resonant cavity is 56 mm, the height c of the resonant cavity is 48 mm, the inner cavity length p of the feeding cavity 3 is 50 mm, the inner cavity width q of the feeding cavity 3 is 25 mm, the inner cavity height s of the feeding cavity 3 is 25 mm, the length L1 of the radiation slot 11 is 31 mm, the width W1 of the radiation slot 11 is 15 mm, the length L2 of the feeding slot 12 is 37 mm, the width W2 of the feeding slot 12 is 4 mm, and the central feed line 311 extends into the feeding cavity 3. The inner length L3=21mm, the distance D1=23mm between the axis of the tuning column 2 and the top of the resonant cavity, the distance D2=14mm between the axis of the central feed line 311 and the second panel, the radius of the first tuning column 21 and the second tuning column 22 are both r=3mm, the thickness of the first panel t1=5mm, the thickness of the second panel t2=3, the angle α1=45° between the radiation slot 11 and the length direction of the tuning cavity 1, the angle α2=45° between the feeding slot 12 and the length direction of the tuning cavity 1, the extension direction of the first tuning column 21 is parallel to the width direction of the tuning cavity 1, and the extension direction of the second tuning column 22 is parallel to the length direction of the tuning cavity 1.It should be understood that the parameters of the aforementioned dual-band antenna are only a preferred example. In practical applications, in order to obtain a suitable tuning frequency band range, the parameters can be adaptively adjusted as needed: for example, the shapes of the tuning cavity 1 and the feeding cavity 3 can be adjusted simultaneously or separately to a cylindrical shape, a pentagonal prism shape, a hexagonal prism shape, etc., and the inner cavities of the tuning cavity 1 and the feeding cavity 3 can be changed accordingly with their respective shapes; when the tuning cavity 1 and the feeding cavity 3 are both rectangular structures, the sum of the angle α1 between the radiation slot 11 and the tuning cavity 1 in the length direction and the angle α2 between the feeding slot 12 and the tuning cavity 1 in the length direction is maintained at 90°, and α1 can be 25°, 30°, 35°, 40°, 50°, 55°, 60°, 65°, 70°, etc., and the length a of the resonant cavity can be selected within 20mm-150mm, for example 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm, 55mm, 60mm, 65mm, 70mm, 75mm, 80mm, 85mm, 90mm, 95mm, 100mm, 105mm, 110mm, 115mm, 120mm, 125mm, 130mm, 135mm, 140mm, 145mm, etc., and, with reference to the aforementioned preferred scheme, the ratios of the sizes of the remaining parameters and the length a of the resonant cavity can float up and down, and the floating ratio can be between 0-50%, for example, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, etc., taking the length a of the resonant cavity as 148mm and the ratio of the width b of the resonant cavity to the length a of the resonant cavity floating down by 10% as an example, b can be set to 148*(56 / 74)*(1-10%)=100.8mm, and other parameters can be adaptively set according to this method, which will not be repeated here.

[0059] The following is a design analysis of the tunable dual-frequency antenna scheme. Combined with the introduction of the above-mentioned single-frequency antenna, it can be understood that the cavity mode is affected by the tuning column 2 placed parallel to the electric field, where the electric fields of the tuning column 2 and the TE101 mode are both along the y-axis. In the rectangular tuning cavity 1, there is another cavity mode in which the electric field is distributed along the x-axis, namely the TE011 mode. These two modes can be used to design a dual-frequency slot antenna. As mentioned above, as shown in Figure 10, a tunable dual-frequency antenna can be formed by introducing a second tuning column 22 and a first tuning column 21 along the x-axis and y-axis, respectively. Both the feed slot 12 and the radiation slot 11 are rotated to simultaneously excite the TE101 and TE011 modes for radiation. Here, the rotation angle of the radiation slot 11 is set to -45° (or +45°) to keep the radiation patterns of the electric field E and the magnetic field H at -45° and +45°, while the rotation angle of the feed slot 12 can be finally determined after optimization.

[0060] like Fig.11(a) shows the simulated |S11| of the dual-frequency antenna when the tuning column 2 is not set. The figure also shows the electric field distribution of the two resonant modes in the cavity. It can be seen that the first mode is TE101 and the second mode is TE011, which shows that they have orthogonal polarization. In fact, these two modes can only be radiated through the same radiation slot 11. The rotating radiation slot 11 can radiate these two modes at the same time. The electric field distribution of the two modes at the radiation slot is shown as follows: Fig.11 As shown in (b) and (c), it can be seen that they have the same electric field direction. Since the electric field at the radiation slot 11 plays a dominant role in the far-field radiation characteristics, the radiation patterns of the two modes have the same polarization.

[0061] Although the feeding slot 12 and the radiation slot 11 affect both modes at the same time, they produce different degrees of disturbance to the two modes. In addition, the first tuning column 21 along the y-axis only affects the TE101 mode, while the second tuning column 22 along the x-axis only affects the TE011 mode. According to the above similar analysis, Fig.12 As shown, the equivalent circuit model of the reconfigurable dual-band antenna can be established. In order to simplify the analysis in this paper, each mode corresponds to one branch. The resonant frequency of the TE101 mode is expressed as formula (1). Similarly, the resonant frequency of the TE011 mode can be expressed as:

[0062] (3)

[0063] According to formula (1) and formula (3), it can be known that the resonant frequencies of modes TE101 and TE011 can be tuned independently by changing the inductances Lp1 and Lp2. Here, the load inductances of Lp1 and Lp2 are determined by the lengths of the first tuning column 21 and the second tuning column 22 extending into the resonant cavity, respectively. In order to prove that the two modes can be tuned independently with the help of the two tuning columns 2, as shown in Fig.13 As shown in Figure 2, the resonant frequencies of the two modes under different L4 and L5 are shown. It can be seen that the two modes can indeed be tuned independently without affecting the other mode. As a convenient method for independent tuning mechanism, the cavity mode with the same direction of electric field distribution is determined only by the tuning column 2 parallel to its electric field.

[0064] To this end, a tunable dual-band antenna was proposed and designed. The final simulation results are as follows: Fig.14As shown, adjusting the length of the first tuning column 21 extending into the resonant cavity can produce a tunable frequency of the first frequency band, and will slightly affect the second frequency band. The tuning range of 10db return loss of the first frequency band is 3.56ghz~3.15ghz, and the tuning rate is 11.5%. At the same time, adjusting the length of the second tuning column 22 extending into the resonant cavity can produce a tunable frequency of the second frequency band, and has little effect on the first frequency band. The tuning range of 10db return loss of the second frequency band is 3.88ghz~3.23ghz, and the tuning rate is 18.3%. It can also be seen that the tuning frequency of the second frequency band changes on the first frequency band, as shown in FIG. Fig.14 (c) and (d), which well demonstrates the working stability of the proposed tunable dual-frequency antenna based on cavity mode. The radiation pattern of the tunable dual-frequency antenna within the tuning range is shown in Fig.15 As shown, this also shows that the tunable dual-band antenna has a stable radiation pattern.

[0065] In a third implementation, a tunable broadband slot antenna is provided:

[0066] The antenna structure of this implementation can refer to the dual-frequency antenna of the third implementation, in which the two modes can resonate in the same frequency band, thereby forming a dual-mode wide operating frequency band due to the disappearance of the radiation zero point between the two resonant frequencies. The specific parameters of the antenna are as follows: the length of the resonant cavity a = 80mm, the width of the resonant cavity b = 66mm, the height of the resonant cavity c = 51mm, the inner cavity length of the feeding cavity 3 p = 52mm, the inner cavity width of the feeding cavity 3 q = 25mm, the inner cavity height of the feeding cavity 3 s = 25mm, the length of the radiation slot 11 L1 = 42mm, the width of the radiation slot 11 W1 = 10mm, the length of the feeding slot 12 L2 = 52mm, the width of the feeding slot 12 W2 = 12mm, the center The length L3 of the feed line 311 extending into the feed cavity 3 is 18 mm, the distance D1 between the axis of the tuning column 2 and the top of the resonant cavity is 26 mm, the distance D2 between the axis of the central feed line 311 and the second panel is 6 mm, the radius of the first tuning column 21 and the second tuning column 22 are both r=3 mm, the thickness t1 of the first panel is 3 mm, the thickness t2 of the second panel is 3, the angle α1 between the radiation slot 11 and the length direction of the tuning cavity 1 is 45°, the angle α2 between the feed slot 12 and the length direction of the tuning cavity 1 is 60°, the extension direction of the first tuning column 21 is parallel to the width direction of the tuning cavity 1, and the extension direction of the second tuning column 22 is parallel to the length direction of the tuning cavity 1. This scheme is only an example, and it should be understood that according to the ratio relationship of each parameter in this scheme, the parameter adjustment method listed in the second implementation method can be referred to to adaptively adjust the broadband slot antenna of this implementation method to obtain an appropriate tuning frequency range.

[0067] Fig.16The simulation results of this dual-mode broadband slot antenna are shown, where the bandwidth (BW) of the dual-mode antenna is approximately given as the frequency difference between f1 (TE101 mode) and f2 (TE011 mode). At the same time, the fractional bandwidth (FBW) is defined as the ratio of BW / fc, where fc represents the center frequency of the operating band. As shown in equations (1) and (3), f1 and f2 can be modified independently, so that BW, FBW and fc can all be flexibly controlled.

[0068] Originally, it is difficult to control the BW using conventional reconstruction techniques because the resonant frequencies of these modes cannot be independently controlled. However, in this scheme, the two modes of the proposed antenna can be independently adjusted by modifying the length of their respective tuning posts 2 extending into the resonant cavity. Therefore, this attractive property can be effectively used to design a frequency-tunable slot antenna with a constant FBW and a bandwidth-tunable slot antenna with a constant center frequency.

[0069] A. Constant FBW frequency reconfigurable antenna

[0070] First, we start with the design of a frequency reconfigurable constant FBW slot antenna. Since f1 and f2 are tuned by modifying the length of the first tuning post 21 and the second tuning post 22 extending into the resonant cavity, all BW, FBW, and fc can be manipulated as a function of L4 and L5 (starting from the initially obtained antenna performance, such as Fig.16 Here, FBW is given by the initial performance, e.g., Fig.16 The FBW of the antenna shown is 5.8%. fc is the target center frequency during frequency tuning. Once the FBW and fc are given, the FBW can be calculated by using equation (4) The target reconfigurable frequencies f1 and f2 are determined, and the specified f1 and f2 can be obtained by appropriately adjusting the lengths of the first tuning column 21 and the second tuning column 22 extending into the resonant cavity.

[0071] For proof of concept, we built and tested an antenna prototype after the design was completed. Fig.17 (b) provides photos of the experimental setup for S parameters and far-field radiation. Two tuning metal screws (the first tuning column 21 and the second tuning column 22) are used as tuning elements, and the tuning process is performed by twisting the metal screws. Fig.18 The measured and simulated |S11|, achieved gain and total efficiency are shown. The three states show that the center frequency is adjustable, the FBW is constant at 5.8%, the lengths of the two tuning posts 2 and the simulation / measurement results for these three states are shown in Table 1 ( Fig.21). The tuning range of the broadband slot antenna is 3.735GHz to 3.5GHz, the return loss is 10dB, and the tuning percentage is about 6.5%. The measured total efficiency of the antenna in all three states is higher than 88%, while the simulated total efficiency is higher than 90%. The simulated and measured radiation patterns of the center frequencies of the three states are shown in Figure 2. Fig.19 As shown in the figure, their co-polarization in these three states hardly changes, showing a stable radiation pattern. The cross-polarization is better than 20dB. The simulation results are in good agreement with the measured results.

[0072] B. FBW reconfigurable antenna with constant center frequency

[0073] Next, we further utilize the proposed design concept to design a bandwidth reconfigurable antenna with a constant center frequency. In this design, the center frequency fc is given, and the FBW is adaptively set during the tuning process. According to formula (4), the specified frequencies f1 and f2 can be obtained by appropriately adjusting the lengths of the first tuning column 21 and the second tuning column 22 extending into the resonant cavity. In particular, a variable bandwidth is obtained by twisting the two metal columns in opposite directions (i.e., increasing (or decreasing) the length of the first tuning column 21 (L4) and decreasing (or increasing) the length of the second tuning column 22 (L5)). Fig. 20 The simulated and measured |S11| of the tunable operating bandwidth with a constant center frequency of 3.62GHz are shown. Good agreement is obtained between them over the frequency range. The measured bandwidth can be flexibly tuned from 294MHz to 142MHz with a return loss of 10db. The detailed results are shown in Table II ( Fig. 22 ). In fact, by further increasing L4 and reducing L5, the BW or FBW can be made as small as possible.

[0074] The above three antenna structures achieve tuning by adjusting the length of the tuning column 2 extending into the resonant cavity, and have the characteristic of low tuning speed. The length of the resonance extending into the resonant cavity can be adjusted by manual adjustment of a threaded connection, or by a motor-controlled extension of the tuning column 2. Although the tuning speed is low, it can bring the characteristics of low power consumption, high antenna efficiency and good reliability. In addition, the antenna under this concept can realize a dual-mode broadband antenna with reconfigurable frequency and bandwidth.

[0075] In the above-mentioned various conceptual schemes, in order to obtain higher gain and maintain reconfigurable characteristics, a plurality of radiation slots 11 may be provided on the first panel, and the length directions of the radiation slots 11 are parallel to each other.

[0076] The tunable slot antenna proposed in this scheme has the characteristics of independent continuous tuning capability, high power handling capability, low loss, high efficiency, unidirectional radiation and stable radiation pattern, and has the performance of low loss, high efficiency, high power handling capability and high long-term reliability. These advantages make the proposed tunable slot antenna suitable for multi-band mobile wireless communication systems.

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A tunable slot antenna, characterized in that: The invention comprises a tuning cavity (1), a tuning column (2) and a feeding cavity (3), wherein the tuning cavity (1), the tuning column (2) and the feeding cavity (3) are all made of metal materials, the tuning cavity (1) comprises a first panel, a second panel opposite to the first panel and a side wall (13) connected between the first panel and the second panel, the first panel, the second panel and the side wall (13) enclose a resonant cavity, the first panel has a radiation slot (11), and the second panel has a A feeding slot (12) is provided, the tuning column (2) is connected to the side wall (13) and one end thereof extends into the resonant cavity, the length of the tuning column (2) extending into the resonant cavity is adjustable, the feeding cavity (3) is connected to the side of the second panel facing away from the first panel, the feeding cavity (3) surrounds the feeding slot (12), the feeding cavity (3) is connected to a coaxial feeding terminal (31), and a central feeding line (311) of the coaxial feeding terminal (31) extends into the feeding cavity (3); The first panel and the second panel are parallel to each other, the length direction of the radiation slot (11) is parallel to the length direction of the feeding slot (12), and the length direction of the tuning column (2) is parallel to the plate surface of the first panel and perpendicular to the length direction of the radiation slot (11); The ratio of the length of the radiation slot (11) to the width of the radiation slot (11) is 2.00-6.00, the ratio of the length of the feeding slot (12) to the width of the feeding slot (12) is 3.50-8.00, and the ratio of the length of the radiation slot (11) to the length of the feeding slot (12) is 0.60-0.95; The center of the radiation slot (11) and the center of the feeding slot (12) are directly opposite to each other, and the plane where the center line of the tuning column (2) and the center line of the central feeding line (311) are located passes through the center of the radiation slot (11) and the center of the feeding slot (12); The ratio of the adjustable length of the tuning column (2) extending into the resonant cavity to the width of the resonant cavity in the length direction of the tuning column is 0-0.

5.

2. The tunable slot antenna according to claim 1, characterized in that: The central feed line (311) is parallel to the surface of the second panel, and the central feed line (311) is perpendicular to the length direction of the feed slot (12).

3. A tunable slot antenna, characterized in that: The invention comprises a tuning cavity (1), a tuning column (2) and a feeding cavity (3), wherein the tuning cavity (1), the tuning column (2) and the feeding cavity (3) are all made of metal materials, the tuning cavity (1) comprises a first panel, a second panel opposite to the first panel and a side wall (13) connected between the first panel and the second panel, the first panel, the second panel and the side wall (13) enclose a resonant cavity, the first panel has a radiation slot (11), and the second panel has a A feeding slot (12) is provided, the tuning column (2) is connected to the side wall (13) and one end thereof extends into the resonant cavity, the length of the tuning column (2) extending into the resonant cavity is adjustable, the feeding cavity (3) is connected to the side of the second panel facing away from the first panel, the feeding cavity (3) surrounds the feeding slot (12), the feeding cavity (3) is connected to a coaxial feeding terminal (31), and a central feeding line (311) of the coaxial feeding terminal (31) extends into the feeding cavity (3); The first panel and the second panel are parallel to each other, an angle is formed between the length direction of the radiation slot (11) and the length direction of the feeding slot (12), the extension direction of the central feeding line (311) is perpendicular to the length direction of the feeding slot (12), the side wall (13) is connected with a first tuning column (21) and a second tuning column (22), the length directions of the first tuning column (21) and the second tuning column (22) are parallel to the first panel, an angle is formed between the first tuning column (21) and the second tuning column (22), and an angle is formed between the first tuning column (21) and the second tuning column (22); The ratio of the length of the radiation slot (11) to the width of the radiation slot (11) is 1.50-8.00, the ratio of the length of the feeding slot (12) to the width of the feeding slot (12) is 2-15, and the ratio of the length of the radiation slot (11) to the length of the feeding slot (12) is 0.60-0.

95.

4. The tunable slot antenna according to claim 3, characterized in that: The centers of the radiation slot (11) and the feeding slot (12) are directly opposite, the angle between the radiation slot (11) and the feeding slot (12) is 90°, the first tuning column (21) and the second tuning column (22) are perpendicular to each other, and the angle between the first tuning column (21) and the radiation slot (11) in the length direction and the angle between the second tuning column (22) and the radiation slot (11) in the length direction are both 45°.

5. The tunable slot antenna according to any one of claims 3 to 4, characterized in that: The central feed line (311) is parallel to the surface of the second panel, and the central feed line (311) is perpendicular to the length direction of the feed slot (12).

6. A multi-band antenna system, characterized in that: Comprising the tunable slot antenna as described in any one of claims 1-5.

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