Wide angle frequency scanning antenna based on dual-band coupled filters

Abstract

The application discloses a wide-angle frequency scanning antenna based on a dual-band coupling filter, comprising a power divider module, a dual-band filter module and an antenna radiation unit. The power divider module is used for power distribution of an input signal; the dual-band filter module is used for phase modulation of the output signal of the power divider; and the antenna radiation unit is used for signal radiation of the dual-band. The application adopts the dual-band filter to modulate the signal phase, realizes two groups of different phase distributions changing with frequency in the specified two frequency bands respectively, and covers different angle ranges in the positive and negative directions respectively, so that the wide-angle scanning from-60° to 60° is realized finally. The dual-band design reduces the design pressure of the single-band scheme. With the flexible bandwidth design function of the filter, the frequency scanning antenna can be customized according to the actual demand. The wide-angle frequency scanning antenna realized by the application has the advantages of large scanning range, small scanning gain fluctuation and customizable frequency band range.

Description

Technical Field

[0001] This invention belongs to the field of antenna technology, specifically a wide-angle frequency-scanning antenna based on a dual-band coupling filter. Background Technology

[0002] Beam-scanning antennas, due to their beam-scanning capability, have been widely used in radar imaging, target detection, and wireless communication. Electrically scanned antennas control the beam pointing of the antenna array by changing the phase difference between antenna elements using electrical signals. Common methods include phase scanning and frequency scanning. Compared to phase scanning, the beam of a frequency-scanning antenna deflects with the frequency of the excitation signal, eliminating the need for an additional phase shifter. This results in advantages such as high cost-effectiveness and fast beamforming speed, attracting widespread attention.

[0003] Currently, frequency-scanning antennas are mainly implemented using leaky wave antennas or by introducing slow-wave line structures. Leaky wave antennas are highly efficient, but traditional leaky wave antennas can only achieve forward single-sided scanning and suffer from problems such as small scanning range, high sidelobes in the radiation pattern, and large scanning gain variations. Slow-wave line structures, on the other hand, are large in size and have high losses; as the array size increases, the losses gradually accumulate, resulting in low efficiency and limited antenna array size. Therefore, achieving high-performance frequency-scanning antenna arrays with passive low cost, wide-angle scanning, low sidelobes, high efficiency and high gain, and small scanning gain variations has become a research focus in recent years. Summary of the Invention

[0004] The purpose of this invention is to provide a wide-angle frequency-scanning antenna based on a dual-band coupling filter, which is a passive frequency-scanning antenna with a wide scanning angle range, flat gain variation, and flexible frequency band design.

[0005] The technical solution to achieve the purpose of this invention is: a wide-angle frequency-scanning antenna based on a dual-band coupling filter, comprising a power divider module, a dual-band filter module, and an antenna radiating element;

[0006] The power divider module is used to distribute the power of the input signal. In particular, unequal amplitude distribution can be used to achieve low sidelobes.

[0007] The dual-band filter module is used to phase modulate the output signal of the power divider module, achieving two different phase distributions that vary with frequency within two specified frequency bands, thereby realizing dual-band frequency scanning. Specifically, the phase difference between adjacent antenna elements in the two frequency bands has opposite signs, achieving different scanning angle coverage ranges, thus extending the scanning range using both frequency bands.

[0008] The antenna radiating element is used for dual-band signal radiation;

[0009] The power divider module, dual-band filter module, and antenna radiating unit are connected sequentially using microstrip lines or coaxial lines.

[0010] Furthermore, the dual-band filter module includes four independent dual-band substrate integrated waveguide filters with orders of 3rd, 4th, 5th and 6th order, respectively, which are composed of 3, 4, 5 and 6 resonant cavities, respectively.

[0011] Furthermore, the signal input and output ports of the 3rd and 5th order dual-band substrate integrated waveguide filters are centrally symmetrical, used to generate a -180° phase shift in the second frequency band; the signal input and output ports of the 4th and 6th order dual-band substrate integrated waveguide filters are axisymmetric, used to keep the phase of the second frequency band unchanged.

[0012] Furthermore, the 3rd, 4th, 5th, and 6th order dual-band substrate integrated waveguide filters satisfy the following conditions: In the first frequency band, as the order increases, the phase at the center frequency decreases by 90° sequentially, and the magnitude of the phase slope also gradually increases. By adjusting the bandwidth of each filter, the phase difference between adjacent filters is equalized. In the second frequency band, by utilizing the central symmetry of the 3rd and 5th order ports, the phase at the center frequency increases by 90° sequentially with the order, and the magnitude of the phase slope also increases accordingly. By adjusting the bandwidth of each filter, the phase difference between adjacent filters is equalized.

[0013] Preferably, the four output ports of the power divider module distribute signal power according to a power division ratio of 1:1.5:1.5:1.

[0014] Preferably, the power divider module is composed of a 1-to-2 Wilkinson equal power divider and two identical 1-to-2 Wilkinson unequal power dividers.

[0015] Preferably, the antenna radiating element is a dual-band quasi-Yagi antenna with four sides arranged side by side, maintaining a wide beam in the two required frequency ranges.

[0016] Preferably, the spacing between adjacent dual-frequency quasi-Yagi antenna elements is the same, i.e., d = 0.34λ. f1 / 0.45λ f2 (λ f1 and λ f2 These are the free-space wavelengths of the first and second frequency bands, respectively.

[0017] Compared with the prior art, the significant advantages of this invention are:

[0018] 1) Phase modulation is performed using a dual-band filter to achieve two different frequency-varying phase distributions in two specified frequency bands, thereby realizing dual-band frequency scanning. In particular, the phase difference between adjacent antenna elements in the two frequency bands has opposite signs, enabling wide-angle scanning in the range of -60° to 60°.

[0019] 2) Compared with single-band beam scanning, the proposed dual-band frequency scanning antenna innovatively utilizes two frequency bands to achieve frequency scanning, reducing the design pressure of one frequency band. The gain fluctuation amplitude is smaller when scanning within each frequency band, and the maximum gain fluctuation within the scanning angle range is only 0.95dB, with high gain flatness.

[0020] 3) Since the phase modulation circuit for frequency sweeping is based on a dual-band filter design, and the filter has a flexible bandwidth design function, the frequency sweep antenna can be flexibly customized according to actual needs.

[0021] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a wide-angle frequency-scanning antenna based on a dual-band coupling filter in one embodiment.

[0023] Figure 2 This is a schematic diagram of the structure of a dual-band filter module in one embodiment.

[0024] Figure 3 (a) in the figure is the amplitude response diagram of a dual-band filter module in one embodiment. Figure 3 (b) in the figure is a phase response diagram of a dual-band filter module in one embodiment.

[0025] Figure 4 This is a schematic diagram of the power divider module in one embodiment.

[0026] Figure 5 (a) in the figure is the amplitude response diagram of the power divider module in one embodiment. Figure 5 (b) in the figure is a phase response diagram of the power divider module in one embodiment.

[0027] Figure 6 This is a schematic diagram of the structure of an antenna radiating element in one embodiment.

[0028] Figure 7 This is a simulation result of the radiation pattern of the antenna radiation element in one embodiment.

[0029] Figure 8 This is a simulation layout of a wide-angle frequency-scanning antenna based on a dual-band coupling filter in one embodiment.

[0030] Figure 9 This is a diagram showing the reflection coefficient results of a wide-angle frequency-scanning antenna based on a dual-band coupling filter in one embodiment.

[0031] Figure 10 This is a beam pattern of a wide-angle frequency-scanning antenna based on a dual-band coupling filter, tuned at different frequencies in one embodiment. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0033] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0034] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0035] In one embodiment, combined Figure 1 A wide-angle frequency-scanning antenna based on a dual-band coupling filter is provided, including a power divider module 1, a dual-band filter module 2, and an antenna radiating element 3.

[0036] The power divider module 1 is used to distribute the power of the input signal. In particular, unequal amplitude distribution can be used to achieve low sidelobes;

[0037] Here, the power allocation ratio is not fixed, but is designed according to specific performance indicators.

[0038] The dual-band filter module 2 is used to phase modulate the output signal of the power divider, realizing two different phase distributions that vary with frequency in two specified frequency bands, thereby achieving dual-band frequency scanning. In particular, the phase difference between adjacent antenna elements in the two frequency bands has opposite signs, achieving different scanning angle coverage ranges, thus expanding the scanning range using two frequency bands.

[0039] Here, the dual-band filter module 2 includes four independent dual-band filters, each with output phases of φ1, φ2, φ3, and φ4, respectively; within the first and second frequency bands, the phase differences between adjacent antenna elements are α1 and α2, respectively, satisfying:

[0040] φ2-φ1=φ3-φ2=φ4-φ3=α1 (frequency band 1)

[0041] φ2-φ1=φ3-φ2=φ4-φ3=α2 (frequency band 2)

[0042] The scanning angle θ of the frequency-scanning antenna can be calculated based on the phase difference α1 / α2 between adjacent antenna elements and the element spacing d. The calculation formula is:

[0043]

[0044] As can be seen from the formula, since the phase differences α1 and α2 are opposite in sign, the beam scanning angles θ1 and θ2 of the first frequency band are also opposite in sign. By using two frequency bands, the scanning angle coverage of the positive half-plane or the negative half-plane can be achieved respectively, thus expanding the beam scanning range.

[0045] The antenna radiating element 3 is used for dual-band signal radiation.

[0046] Here, the bandwidth of antenna radiating element 3 needs to cover the required dual-band bandwidth, the beamwidth within the required dual-band range must be greater than the designed scanning angle range, and the impedance matching must be good. The specific structure of antenna radiating element 3 can be any structure that meets the above conditions.

[0047] The power divider module 1, the dual-band filter module 2, and the antenna radiating unit 3 are connected in sequence using microstrip lines or coaxial lines.

[0048] Furthermore, in one embodiment, the dual-band filter module includes four independent dual-band substrate integrated waveguide filters with orders of 3rd, 4th, 5th and 6th, respectively, which are composed of 3, 4, 5 and 6 resonant cavities, respectively.

[0049] Furthermore, in one embodiment, the signal input and output ports of the 3rd and 5th order dual-band substrate integrated waveguide filters are centrally symmetric, used to generate a -180° phase shift in the second frequency band; the signal input and output ports of the 4th and 6th order dual-band substrate integrated waveguide filters are axisymmetric, used to keep the phase of the second frequency band unchanged.

[0050] Furthermore, in one embodiment, the 3rd, 4th, 5th, and 6th order dual-band substrate integrated waveguide filters satisfy the following conditions:

[0051] Within the first frequency band, as the order increases, the phase at the center frequency decreases by 90° sequentially, and the magnitude of the phase slope also gradually increases. By adjusting the bandwidth of each dual-band substrate integrated waveguide filter, the phase difference between adjacent filters is made equal.

[0052] In the second frequency band, by using the 3rd and 5th order ports to be centrally symmetrical, the phase at the center frequency increases by 90° with the increase of the order, and the magnitude of the phase slope also increases accordingly. By adjusting the bandwidth of each dual-band substrate integrated waveguide filter, the phase difference between adjacent filters is made equal.

[0053] Furthermore, in one embodiment, the power divider module includes four output ports and distributes signal power according to a power division ratio of 1:1.5:1.5:1, outputting it to four dual-band substrate integrated waveguide filters respectively.

[0054] Furthermore, in one embodiment, the power divider module is composed of a 1-to-2 Wilkinson equal power divider and two identical 1-to-2 Wilkinson unequal power dividers.

[0055] Furthermore, in one embodiment, the antenna radiating element includes four dual-band quasi-Yagi antennas arranged side by side, maintaining a wide beam within the required dual-band range, i.e., maintaining a beamwidth greater than the designed scanning angle range within the dual-band range.

[0056] Furthermore, in one embodiment, the spacing between adjacent dual-band quasi-Yagi antenna elements is the same, with a spacing d = 0.34λ. f1 / 0.45λ f2 , where λ f1 and λ f2 The free space wavelengths of the first and second frequency bands, respectively.

[0057] As a specific example, in one embodiment, the wide-angle frequency-scanning antenna based on a dual-band coupling filter of the present invention is further verified and explained.

[0058] In this embodiment, both the filter module and the power divider module are implemented using an F4B dielectric substrate with a relative permittivity of 2.2 and a thickness of 1.5 mm. The antenna radiating element is implemented using a Rogers4003C dielectric substrate with a relative permittivity of 3.55 and a thickness of 0.803 mm.

[0059] Combination Figure 2 The dual-band filter module in this embodiment includes four independent dual-band substrate integrated waveguide filters with orders of 3rd, 4th, 5th, and 6th order, respectively. The third-order filter 4 consists of three directly coupled resonant cavities, the fourth-order filter 5 consists of four directly coupled resonant cavities, the fifth-order filter 6 consists of five directly coupled resonant cavities, and the sixth-order filter 7 consists of six directly coupled resonant cavities.

[0060] Combination Figure 3 The resonant modes of the four dual-band filters in the first frequency band are all TE. 101 The mode has a center frequency of 3.4 GHz and a relative bandwidth (FBW) of 7.6%. In terms of phase, as the order increases, the center frequency phase decreases by 90° sequentially, and the magnitude of the phase slope gradually increases. The phase slope is then adjusted by changing the bandwidth to achieve equal phase difference between adjacent filters. At 3.25 GHz, the four dual-band filters have equal phase and a beam direction of 0°. Figure 10 As shown; at a frequency of 3.51 GHz, the phase difference between adjacent dual-band filters is equal and 113°, and the beam direction is 60°, as... Figure 10 As shown, the maximum insertion losses for the 3rd, 4th, 5th, and 6th order filters are 0.83, 0.98, 1.69, and 1.98 dB, respectively. Insertion loss is directly proportional to the order and inversely proportional to the bandwidth. By utilizing a dual-band design to extend the scanning range, the first band only needs to achieve a 0–60° scanning range, which can be achieved with a smaller order and a larger bandwidth, thus offering the advantage of low insertion loss.

[0061] Furthermore, the positions of the input and output ports of each filter were designed to achieve a -180° phase shift (i.e., phase inversion) in the second frequency band for the odd-order dual-band filter. The resonant modes of the four dual-band filters in the second frequency band are all TE. 201 The module has a center frequency of 4.5 GHz and a relative bandwidth (FBW) of 7.6%. Combined with... Figure 2 The signal input and output ports of 3rd and 5th order dual-band filters are centrally symmetric, while the signal input and output ports of 4th and 6th order dual-band filters are axisymmetric. In TE... 201When the phase is constant, the output current directions of the centrosymmetric and axisymmetric structures are opposite. Therefore, the phases of the 4th and 6th order dual-band filters remain unchanged in the second frequency band, while the phases of the 3rd and 5th order dual-band filters experience a -180° phase shift. The phase difference between the center frequencies of the 4th and 6th order dual-band filters in the second frequency band is 360°, which is equivalent to 0°.

[0062] Finally, the phase distribution of the second frequency band is as follows: Figure 3 As shown, in terms of phase, as the order increases, the center frequency phase increases by 90° sequentially, and the magnitude of the phase slope also gradually increases. The phase slope is then adjusted by changing the bandwidth to achieve equal phase differences between adjacent filters. Specifically, at 4.36 GHz, the phase difference between the four dual-band filters is 146°, and the beam direction is -60°. In terms of amplitude, the maximum insertion losses of the 3rd, 4th, 5th, and 6th order filters are 0.87, 1.26, 1.3, and 1.84 dB, respectively.

[0063] Figure 4 A schematic diagram of the power divider module 1 is given. Power divider module 1 is composed of a single Wilkinson equal power divider 8 (1 / 2 split) and two Wilkinson unequal power dividers 9 (1 / 2 split), with a power ratio of 1:1.5:1.5:1 to achieve low sidelobes in the antenna array. The ends of the power dividers are bent to fit the overall structure. Simulation results of the amplitude and phase response of the power divider module are shown below. Figure 5 As shown in the figure, the power division ratio basically meets the requirements, the port matching and isolation are good, and the four output ports are in phase.

[0064] The structure of antenna radiating element 3 is as follows Figure 6 As shown, this antenna is a dual-band quasi-Yagi antenna, arranged side-by-side in a four-element linear array. The spacing between adjacent dual-band quasi-Yagi antenna elements is the same, d = 30 mm, or d = 0.34λ. f1 / 0.45λ f2 (λ f1 and λ f2 These are the free space wavelengths for frequency band one and frequency band two, respectively. Figure 7 The radiation patterns of the antenna elements at center frequencies f1 and f2 are shown. Due to the use of a dual-band quasi-Yagi antenna, the gain variation of ±60° beamwidth within a single frequency band does not exceed 0.7 dBi, demonstrating excellent gain flatness.

[0065] Figure 8 This is a simulation layout of a wide-angle frequency-scanning antenna based on a dual-band coupling filter in this embodiment. The power divider module and the dual-band filter are printed as a single unit. The dual-band filter and the antenna unit are connected by a coaxial line, and the antenna unit is fixed by a support column. Figure 9 This embodiment demonstrates the wide-angle frequency-scanning antenna based on a dual-band coupling filter within the frequency band S. 11All values ​​were below -14dB, indicating good matching. Figure 10 The image shows the measured radiation pattern of the wide-angle frequency-scanning antenna based on the dual-band coupling filter in this embodiment. It can be seen that the beam can scan within the dual-band range of -60° to +60°, and the measured gain range is 7.63dBi to 8.58dBi, with a gain fluctuation of only 0.95dBi, achieving a large-angle, flat-gain scanning.

[0066] This invention employs a dual-band filter to modulate the signal phase, achieving two different frequency-varying phase distributions within two specified frequency bands to realize dual-band frequency scanning. Specifically, the phase difference between adjacent antenna elements in the two frequency bands has opposite signs, enabling wide-angle scanning from -60° to 60°. The dual-band frequency-scanning antenna innovatively utilizes two frequency bands to achieve a wide beam coverage range, reducing the design pressure of traditional single-band antennas. Gain fluctuations are smaller within each band, with a maximum gain fluctuation of only 0.95 dBi within the scanning angle range, exhibiting high gain flatness. Since the phase modulation circuit for frequency scanning is based on a dual-band filter design, which has flexible bandwidth design capabilities, the frequency range of this frequency-scanning antenna can be flexibly customized according to actual needs.

[0067] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A wide-angle frequency-scanning antenna based on a dual-band coupled filter, characterized in that, Includes a power divider module, a dual-band filter module, and an antenna radiating unit; The power divider module is used to distribute the power of the input signal; The dual-band filter module is used to perform phase modulation on the output signal of the power divider module, and realize two different phase distributions that vary with frequency in two specified frequency bands, so as to achieve frequency scanning in dual bands. The antenna radiating element is used for dual-band signal radiation; The power divider module, dual-band filter module, and antenna radiating unit are connected sequentially using microstrip lines or coaxial lines. The dual-band filter module includes four independent dual-band substrate integrated waveguide filters with orders of 3rd, 4th, 5th and 6th, respectively, which are composed of 3, 4, 5 and 6 resonant cavities, respectively. The signal input and output ports of the 3rd and 5th order dual-band substrate integrated waveguide filters are centrally symmetrical and are used to generate a -180° phase shift in the second frequency band; the signal input and output ports of the 4th and 6th order dual-band substrate integrated waveguide filters are axisymmetric and are used to keep the phase of the second frequency band unchanged. The 3rd, 4th, 5th, and 6th order dual-band substrate integrated waveguide filters satisfy the following conditions: Within the first frequency band, as the order increases, the phase at the center frequency decreases by 90° sequentially, and the magnitude of the phase slope also gradually increases. By adjusting the bandwidth of each dual-band substrate integrated waveguide filter, the phase difference between adjacent filters is made equal. In the second frequency band, by using the 3rd and 5th order ports to be centrally symmetrical, the phase at the center frequency increases by 90° with the increase of the order, and the magnitude of the phase slope also increases accordingly. By adjusting the bandwidth of each dual-band substrate integrated waveguide filter, the phase difference between adjacent filters is made equal.

2. The wide-angle frequency-scanning antenna based on a dual-band coupling filter according to claim 1, characterized in that, The power divider module includes four output ports and distributes signal power according to a power ratio of 1:1.5:1.5:1, outputting the power to four dual-band substrate integrated waveguide filters respectively.

3. The wide-angle frequency-scanning antenna based on a dual-band coupling filter according to claim 2, characterized in that, The power divider module is composed of a 1-to-2 Wilkinson equal power divider and two identical 1-to-2 Wilkinson unequal power dividers.

4. The wide-angle frequency-scanning antenna based on a dual-band coupling filter according to claim 1, characterized in that, The antenna radiating element includes four dual-band quasi-Yagi antennas arranged side by side, which maintain a wide beam within the required dual-band range, i.e., the beamwidth within the dual-band range is greater than the designed scanning angle range.

5. The wide-angle frequency-scanning antenna based on a dual-band coupling filter according to claim 4, characterized in that, The spacing between adjacent dual-band quasi-Yagi antenna elements is the same, with a spacing d = 0.34λ. f1 / 0.45λ f2 , where λ f1 and λ f2 These are the free-space wavelengths of the first and second frequency bands, respectively.

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