A bandwidth reconfigurable end-fire antenna based on switch-loaded coupled dipole

Abstract

The invention discloses a bandwidth reconfigurable end-fire antenna based on switch-loaded coupled oscillators, comprising a front dipole loaded with a PIN diode, a driving dipole, and a bent dipole loaded with a PIN diode, wherein the three dipoles are closely arranged in parallel; the front dipole and the bent dipole are half-wave dipoles working in an odd mode, respectively, and the resonant frequency of the front dipole is greater than the resonant frequency of the bent dipole; there is magnetic coupling between the front dipole and the driving dipole, electromagnetic hybrid coupling between the driving dipole and the bent dipole, and electrical coupling between the front dipole and the bent dipole, the multi-coupling path brings two radiation zero points to the upper and lower edges of the antenna working frequency band, and the dipole resonant frequency and the coupling amount between the dipoles are regulated by controlling the on-off of the PIN diode, thereby realizing variable bandwidth and variable two radiation zero points and their frequencies.

Description

Technical Field

[0001] The invention relates to a microwave communication device, in particular to a bandwidth reconfigurable end-fire antenna. Background Art

[0002] Reconfigurable end-fire antenna refers to an end-fire antenna with reconfigurable function. It can switch between multiple working states through a single antenna, which is conducive to reducing system complexity, volume and cost, improving the compatibility of antenna working state, and is widely used in wireless communication systems. According to the different reconfigurable working states, reconfigurable end-fire antennas can be divided into frequency reconfigurable end-fire antennas, bandwidth reconfigurable end-fire antennas, directional pattern reconfigurable end-fire antennas, and polarization reconfigurable end-fire antennas. Bandwidth reconfigurable end-fire antennas can realize dynamic adjustment of antenna working bandwidth, improve bandwidth compatibility, and enhance antenna bandwidth adaptability. Further incorporating filtering functions on the basis of bandwidth reconfigurability of end-fire antennas is conducive to improving system integration and reducing the number of components.

[0003] At present, there are two main methods for realizing bandwidth reconfigurable end-fire antennas. The first is to connect parallel branches and T-shaped structures to form a driving dipole through negative inductance and varactor diodes, and use non-Foster elements based on negative inductance and the distance between the dipole and the reflection ground to provide a wide range of impedance matching, so as to realize a bandwidth reconfigurable end-fire antenna based on a varactor tube, which has a wide bandwidth and bandwidth tuning range, but is not compatible with filtering functions, and a long distance needs to be maintained between the dipole and the reflection ground, resulting in a large end-to-end size. The second is to integrate a PIN diode-loaded bandpass filter or a limiting wave structure into the feeder slot part of the quasi-Yagi antenna, and realize the bandwidth tuning of the overall antenna by adjusting the working bandwidth of the bandpass filter or the transmission zero point provided by the limiting wave structure, and integrate the filtering function, but the filter or limiting wave structure added to the feed part occupies additional space outside the antenna, resulting in a large end-to-end size of the antenna, and the bandwidth tuning range and minimum bandwidth of some designs are narrow. Therefore, it is necessary to propose a new type of bandwidth reconfigurable end-fire antenna, which is compatible with the filtering function while maintaining a small end-to-end size of the antenna, while taking into account a wider bandwidth tuning range and minimum bandwidth. Summary of the invention

[0004] Purpose of the invention: In view of the above-mentioned prior art, a bandwidth reconfigurable end-fire antenna based on switch-loaded coupled oscillators is proposed to solve the problems of large end-fire size, incompatible filtering function, small bandwidth tuning range and narrow minimum bandwidth.

[0005] Technical solution: A bandwidth reconfigurable end-fire antenna based on switch-loaded coupled oscillators, including a front dipole loaded with a PIN diode, a driving dipole, and a bent dipole loaded with a PIN diode, wherein the three dipoles are arranged in parallel and closely; the front dipole and the bent dipole are half-wave dipoles operating in odd mode, respectively, and the resonant frequency of the front dipole is greater than the resonant frequency of the bent dipole; there is magnetic coupling between the front dipole and the driving dipole, electromagnetic hybrid coupling between the driving dipole and the bent dipole, and electrical coupling between the front dipole and the bent dipole, the multiple coupling paths bring two radiation zeros to the upper and lower edges of the antenna operating frequency band, and the dipole resonant frequency and the coupling amount between the dipoles are regulated by controlling the on-off of the PIN diode, thereby achieving variable bandwidth and variable two radiation zeros and their frequencies.

[0006] Furthermore, the length of the front dipole is between 0.293 and 0.297 λ0, and a pair of PIN diodes are symmetrically embedded on both sides, and the distance between the PIN diodes and the two ends is between 0.018 and 0.022 λ0; the length of the driving dipole is between 0.36 and 0.4 λ0; the bent dipole includes a horizontal part and a bent vertical short line part located at both ends, the length of the horizontal part is between 0.39 and 0.394 λ0, the length of the bent vertical short line part is between 0.033 and 0.037 λ0, and a pair of PIN diodes are symmetrically embedded in the bent vertical short line part, and the distance between the PIN diodes and the open end of the bent vertical short line is between 0.025 and 0.029 λ0.

[0007] Furthermore, the three dipoles are closely arranged in parallel and are overall symmetrically distributed, wherein the driving dipole falls into the enclosure of the bent dipole, half of the front dipole falls into the enclosure of the bent dipole, and the other half is located outside the enclosure.

[0008] Furthermore, the antenna includes a top metal structure, an intermediate dielectric substrate, and a bottom metal structure; the front end dipole and the driving dipole loaded by the PIN diode are located on the top metal structure, and the bent dipole loaded by the PIN diode is located on the bottom metal structure; and a plurality of bias branches are respectively provided on the top metal structure and the bottom metal structure for providing a DC bias loop for the PIN diode.

[0009] Beneficial effects: Existing bandwidth-reconfigurable end-fire antennas generally have the problem of large end-to-end dimensions, and have one or more of the following problems: incompatibility with filtering functions, small bandwidth tuning range, narrow minimum bandwidth, etc. In the structure of the present invention, the projections of the three dipoles in the vertical direction form a parallel and close arrangement, two of which are loaded with PIN diodes, and the magnetic coupling, electromagnetic hybrid coupling and electrical coupling between the three dipoles are used to form multiple coupling paths between the dipoles, and the PIN diodes regulate the dipole resonance points and the coupling amount between the dipoles to achieve variable bandwidth, two radiation zero points and variable frequencies, and the contribution of the reflection of the bent dipole to reducing the size to form a bandwidth-reconfigurable end-fire antenna with small end-to-end dimensions and filtering functions, while having a large bandwidth tuning range and a large minimum bandwidth.

[0010] Specifically, the front-end dipole is a half-wave dipole working in odd mode with a high resonant frequency. A pair of PIN diodes are symmetrically embedded on both sides. The distance between the PIN diodes and the two ends is between 0.018 and 0.022 λ0. The whole is closely arranged in front of the driving dipole. By controlling the on-off of the PIN diode pair, the resonant frequency of the front-end dipole and its coupling with the driving dipole and the bent dipole can be changed, thereby achieving control of the working bandwidth and the radiation zero point.

[0011] The bent dipole is a half-wave dipole working in odd mode with a low resonant frequency. A pair of PIN diodes are symmetrically embedded in the bent vertical short line. The distance between the PIN diodes and the open end of the bent vertical short line is between 0.025 and 0.029 λ0. The whole is closely arranged behind the driving dipole. By controlling the on and off of the PIN diode pair, the resonant frequency of the bent dipole and the coupling amount with the driving dipole and the front dipole can be changed, thereby achieving control of the working bandwidth and the radiation zero point. On the other hand, the bent dipole acts as a partial reflector, adjusting the reflection phase of the backward wave, which is beneficial to reducing the end-to-end size of the overall antenna.

[0012] The bias branch is formed by multiple short lines connected to each other through inductors and resistors, forming a DC bias network that provides a DC loop for the PIN diode. The inductors and resistors provide choking and current limiting functions respectively, greatly reducing the impact of the bias branch on the antenna operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic diagram of the cross-sectional structure of the antenna of the present invention;

[0014] Figure 2 is a schematic diagram of the top metal structure of the antenna of the present invention;

[0015] Figure 3 is a schematic diagram of the underlying metal structure of the antenna of the present invention;

[0016] Figure 4 It is the matching simulation curve of the antenna of the present invention in different working states;

[0017] Figure 5 The gain simulation curves of the antenna of the present invention in different working states;

[0018] Figure 6 The antenna of the present invention at 2.49 GHz, 3 GHz and 3.79 GHz E Face to face H Surface simulation radiation pattern, where (a) corresponds to 2.49 GHz, (b) corresponds to 3 GHz, and (c) corresponds to 3.79 GHz. DETAILED DESCRIPTION

[0019] The present invention will be further explained below in conjunction with the accompanying drawings.

[0020] like Figures 1 to 3 As shown, a bandwidth reconfigurable end-fire antenna based on a switch-loaded coupled oscillator includes a top metal structure 1, an intermediate dielectric substrate 2, a bottom metal structure 3, and also includes PIN diodes 41-44 and choke inductors 51-56.

[0021] The top metal structure 1 includes a front dipole 11, a driving dipole 12, a coplanar coupling line 13, a parallel feed line 14, and bias branches 15-18. The length of the horizontally arranged front dipole 11 is between 0.293 and 0.297 λ0, and a PIN diode-loaded front dipole is formed by symmetrically embedding PIN diodes 41 and 42. The distance between the PIN diode and the two ends is between 0.018 and 0.022 λ0, and λ0 is the free space wavelength corresponding to the center frequency. The length of the driving dipole 12 is between 0.36 and 0.4 λ0, and it is arranged in parallel with the front dipole 11, and the two are closely adjacent but not connected. The coplanar coupling line 13 is arranged vertically, with a thin upper end and a wide lower end, and the upper end is connected to the driving dipole 12, and the lower end is connected to the parallel feed line 14. One end of the bias branches 15 and 16 is connected to the two ends of the front dipole 11 through the choke inductors 51 and 53 respectively, and the bias branch 18 is connected to the center position of the front dipole 11 through the choke inductor 52 .

[0022] The bottom metal structure 3 includes a bent dipole 31, a metal ground 32, and bias branches 33-37. The bent dipole 31 includes a horizontal portion and a bent vertical short line portion at both ends. The length of the horizontal portion is between 0.39 and 0.394 λ0, and the length of the bent vertical short line portion is between 0.033 and 0.037 λ0. The projection of the driving dipole 12 in the vertical antenna direction falls within the encirclement of the bent dipole 31 and is closely adjacent to the horizontal portion of the bent dipole 31; half of the projection of the front dipole 11 in the vertical antenna direction falls within the encirclement of the bent dipole 31, and the other half is located outside the encirclement. PIN diodes 43 and 44 are symmetrically embedded in the bent vertical short line portion of the bent dipole 31 to form a PIN diode loaded bent dipole. The distance between the PIN diodes 43 and 44 and the open end of the vertical short line is between 0.025 and 0.029 λ0. One end of the bias branch 34, 37 is connected to the open end of the vertical short line of the bent dipole 31 through the choke inductor 54, 56 respectively; one end of the bias branch 33 is connected to the other end of the bias branch 15 through a metallized through hole; one end of the bias branch 36 is connected to the other end of the bias branch 16 through a metallized through hole; the other ends of the bias branches 33, 34, 36, 37 are connected to the metal ground 32. One end of the bias branch 35 is connected to the lower side of the bent dipole 31 through the choke inductor 55, and the other end of the bias branch 35 is connected to the bias branch 17 through a metallized through hole. The bias branches 15, 16, 18, 33 and 36 provide a DC bias loop for the PIN diodes 41, 42; the bias branches 17, 34, 35 and 37 provide a DC bias loop for the PIN diodes 43, 44; the bias branches 17, 18 serve as DC input ends. The parallel feed line 14, the dielectric substrate 2 and the metal ground 32 form a coupled microstrip line. The antenna structure is symmetrically distributed as a whole except for the bias branch.

[0023] For the proposed bandwidth reconfigurable end-fire antenna, the differential mode signal is fed from the coupled microstrip line and transmitted to the driven dipole 12 via the coplanar coupled line 13. Under the joint action of the PIN diode loaded front dipole, the driven dipole 12, the PIN diode loaded bent dipole, the metal ground and the bias branch, a bandwidth reconfigurable planar end-fire antenna with filtering function is formed. Among them, the on-off control of the PIN diode divides the antenna into four working states. State one corresponds to the PIN diodes 41 and 42 being turned off, and the PIN diodes 43 and 44 being turned on. At this time, the front dipole works in an odd mode with a reduced equivalent length, and the resonant frequency is relatively high. The bent dipole works in an odd mode with a normal equivalent length. Since the bent dipole has the longest length, the resonant frequency is the lowest. At the same time, since the front dipole and the two ends of the driving dipole are far apart, which is greater than the parallel spacing between the front dipole and the driving dipole, the two are generally magnetically coupled, and the on-off change of the front dipole loading the PIN diode will change the coupling amount of this magnetic coupling; since the distance between the driving dipole and the two ends of the bent dipole in the horizontal direction is moderate, the projection of the driving dipole in the vertical direction is close to the bent dipole, and the two are generally electromagnetically mixed coupling, and the coupling amount is not affected by the on-off of the PIN diode in the front dipole; since the projection of the front dipole in the vertical direction is far apart from the bent dipole, the distance between the two ends of the front dipole and the bent dipole in the horizontal direction is moderate, and since the magnetic coupling rapidly weakens with distance, the two are generally electrical coupled, and the on-off change of the front dipole loading the PIN diode will change the coupling amount. Combined with the influence of the on-off of the PIN diode on the resonant frequency and the coupling amount, the working bandwidth of state one is the widest. In addition, the magnetic coupling, electromagnetic hybrid coupling and electric coupling between the three dipoles form multiple coupling paths between the dipoles, which can bring two radiation zero points to the upper and lower edges of the antenna working frequency band, thereby improving the frequency selectivity of the antenna, that is, forming a filtering function.

[0024] State two corresponds to PIN diodes 41 and 42 being turned on, and PIN diodes 43 and 44 being turned off. At this time, the front-end dipole operates in an odd-mode mode of normal equivalent length, and the resonant frequency is reduced; the bent dipole operates in an odd-mode mode of reduced equivalent length, and the resonant frequency is increased. At the same time, the coupling type between the three dipoles remains unchanged, but the coupling amount between the bent dipole and the driving dipole and the front-end dipole respectively changes. The changes in the resonance point and the coupling amount make the antenna have the narrowest bandwidth in state two. Since multiple coupling paths still exist, only the coupling amount changes, there are still two radiation zero points, but the positions have changed.

[0025] State three corresponds to the PIN diodes 41, 42, 43 and 44 being turned on, and state four corresponds to the PIN diodes 41, 42, 43 and 44 being turned off. Some of the dipole resonance points in the two states change, the multi-coupling paths still exist, and the coupling amount changes, so there are two new working bandwidths, the bandwidths are between the bandwidths of states one and two, and the two radiation zero points still exist, but the corresponding frequency points change.

[0026] In addition, the bent dipole at the bottom layer has the longest electrical length and is located at the bottom of the three dipoles. It has a certain reflector effect, which adjusts the reflection phase of the backward wave and helps to reduce the end-to-end size of the overall antenna. In vertical projection, the three dipoles are closely arranged, and the overall coupling coefficient is large, which can keep the minimum working bandwidth in the four states still wide. The four states affect the working bandwidth in steps, which can maintain a wide adjustable bandwidth range.

[0027] Compared with the prior art, the bandwidth reconfigurable end-fire antenna proposed by the present invention has the advantages of small end-to-end size, and can take into account filtering function, a larger bandwidth tuning range and a larger minimum bandwidth.

[0028] The substrate used in this embodiment is Rogers RO4003C, and the size of the antenna in the end-fire direction, that is, the distance between the front end of the radiator and the metal ground, is only 0.22 λ0. Under the conditions shown in Table 1, the simulated matching response and gain response are as follows: Figure 4 , Figure 5As shown. When the antenna works in state 1, it can achieve the widest working bandwidth, and the 10-dB matching bandwidth covers 2.49 GHz~3.79 GHz, that is, the relative bandwidth can reach 41.4%, and the gain curve has two radiation zeros, corresponding to 1.9 GHz and 4.6 GHz, and the gain range in the band is 2.42~3.5 dBi. When the antenna works in state 2, it can achieve the narrowest working bandwidth, and the 10-dB matching bandwidth covers 2.61 GHz~3.39 GHz, that is, the relative bandwidth can reach 26%, and the gain curve has two radiation zeros, corresponding to 2.1 GHz and 4.2 GHz, and the gain range in the band is 2.6~3.47 dBi. When the antenna works in state three, the 10-dB matching bandwidth covers 2.41 GHz~3.41 GHz, that is, the relative bandwidth is 34.3%. There are two radiation zeros in the gain curve, corresponding to 1.9 GHz and 4.3 GHz, and the gain range in the band is 3.1~3.87 dBi. When the antenna works in state four, the 10-dB matching bandwidth covers 2.63 GHz~3.73 GHz, that is, the relative bandwidth is 34.6%. There are two radiation zeros in the gain curve, corresponding to 2.1 GHz and 4.7 GHz, and the gain range in the band is 3.35~3.96 dBi. The bandwidth tuning range that can be achieved by this antenna can reach 15.4%. Three radiation zeros can be achieved in all four working states, and the out-of-band suppression level is greater than 17dB, which realizes bandwidth adjustment while being compatible with filtering functions.

[0029] Table 1

[0030] state PIN diodes 41, 42 PIN diodes 43, 44 Status 1 Shutdown Conductivity Status 2 Conductivity Shutdown State three Conductivity Conductivity State 4 Shutdown Shutdown

[0031] Figure 6 The embodiment is shown in Figure 2 at 2.49 GHz, 3 GHz, and 3.79 GHz. E Face to face H Surface simulation pattern. Figure 6 As can be seen in (a), at 2.49 GHz E Face to face H The 3-dB beamwidth ranges of the two planes are 70° and 165.1° respectively. E Face to face H The cross-polarization level of the plane is low. Figure 6 As can be seen in (b), at 3 GHz E Face to face H The 3-dB beamwidth ranges of the two planes are 72.5° and 182.5° respectively. E Face to face H The cross-polarization level of the plane is low. Figure 6 As can be seen from (c), at 3.79 GHz E Face to faceH The 3-dB beamwidth ranges of the two planes are 88.5° and 210.9° respectively. E Face to face H The cross-polarization level of the surface is low.

[0032] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A bandwidth reconfigurable end-fire antenna based on a switch-loaded coupled dipole, characterized in that: The invention comprises a front dipole loaded by a PIN diode, a driving dipole, and a bent dipole loaded by a PIN diode, and the three dipoles are arranged in parallel and closely; the front dipole and the bent dipole are half-wave dipoles working in odd mode respectively, and the resonant frequency of the front dipole is greater than the resonant frequency of the bent dipole; there is magnetic coupling between the front dipole and the driving dipole, electromagnetic hybrid coupling between the driving dipole and the bent dipole, and electrical coupling between the front dipole and the bent dipole, and the three coupling paths bring two radiation zero points to the upper and lower edges of the antenna working frequency band, and the dipole resonant frequency and the coupling amount between the dipoles are regulated by controlling the on and off of the PIN diode, so as to realize variable bandwidth and variable two radiation zero points and their frequencies; The length of the front dipole is between 0.293 and 0.297 λ0, where λ0 is the free space wavelength corresponding to the center frequency. A pair of PIN diodes are symmetrically embedded on both sides, and the distance between the PIN diodes and the two ends is between 0.018 and 0.022 λ0; the length of the driving dipole is between 0.36 and 0.4 λ0; the bent dipole includes a horizontal part and a bent vertical short line part at both ends, the length of the horizontal part is between 0.39 and 0.394 λ0, the length of the bent vertical short line part is between 0.033 and 0.037λ0, a pair of PIN diodes are symmetrically embedded in the bent vertical short line part, and the distance between the PIN diodes and the open end of the bent vertical short line is between 0.025 and 0.029 λ0; The three dipoles are closely arranged in parallel and are symmetrically distributed as a whole, wherein the driving dipole falls into the enclosure of the bent dipole, half of the front dipole falls into the enclosure of the bent dipole, and the other half is located outside the enclosure; The antenna comprises a top metal structure (1), an intermediate dielectric substrate (2), and a bottom metal structure (3); a front dipole and a driving dipole loaded by the PIN diode are located on the top metal structure (1), and a bent dipole loaded by the PIN diode is located on the bottom metal structure (3); and a plurality of bias branches are respectively provided on the top metal structure (1) and the bottom metal structure (3) for providing a DC bias circuit for the PIN diode.

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