A fully polarization reconfigurable traveling wave series-fed array antenna composed of eccentric circular rings

Abstract

The present invention relates to a fully polarized reconfigurable traveling wave series-fed array antenna composed of eccentric circular rings, and belongs to the field of radio frequency communication technology. The traveling wave series-fed array antenna of the present invention, the dual-port feeding can allow the polarization mode of the antenna to be reconstructed. Through a reasonable feeding form, the full polarization performance of the antenna can be stimulated (full polarization means that through a certain design means, the antenna can achieve left-hand circular polarization (LHCP), right-hand circular polarization (RHCP), and linear polarization (LP) performance, and several polarizations can be converted). The present invention adjusts the polarization mode of the antenna by adjusting the feeding form to achieve full polarization reconfiguration. Next, the eccentric circular ring unit structure will be arranged in a circular array, and the array antenna has a compact physical size and a large bandwidth. The tested transmission coefficient will be less than ‑15dB, and the circular polarization axis ratio will be lower than 3dB.

Description

Technical Field

[0001] The invention relates to a fully polarized reconfigurable traveling wave series-fed array antenna composed of eccentric rings, and belongs to the technical field of radio frequency communications. Background Art

[0002] Currently, wireless communication systems place extremely high demands on the efficiency and polarization characteristics of planar antennas. Multifunctional antennas should feature polarization reconfigurability, compact physical size, and flexible radiation characteristics. Circular polarization functionality is a key research focus in polarization reconfigurability. In recent years, research on circularly polarized antennas has become increasingly extensive, and numerous applications have emerged. Scholar Jin Dong Zhang proposed a dual-band, dual-circularly polarized antenna. In 2015, he proposed a dual-band, circularly polarized microstrip antenna operating at 0.92 / 2.45 GHz. In 2010, he proposed a dual-polarized CPW-fed slot antenna to achieve broadband and high isolation. Circular polarization can also be achieved in the TM10 mode. Zhuoxian Liang proposed an antenna composed of two eccentric rings that can achieve dual circular polarization. Researchers have also proposed numerous circularly polarized antenna designs based on patch antennas. Most of the circularly polarized antennas proposed in these papers use single-point feeding. To achieve polarization reconfigurability, it is best to introduce dual-port feeding to generate traveling wave transmission.

[0003] Traveling-wave transmission array antennas offer wide bandwidth, low insertion loss, and a frequency-sweepable radiation pattern. Around 2010, researchers proposed several traveling-wave circularly polarized antennas based on patch antennas. However, the transmission coefficients of these antennas were relatively high, and the bandwidths were relatively narrow. For the millimeter-wave frequency band, Yu-Hang Yang proposed a single-layer circularly polarized series-fed array antenna. Scholars have also proposed a dual-port traveling-wave series-fed array for CP radiation. The circular array arrangement can create a compact structure. By adjusting the port feeding method, antenna polarization can be adjusted to achieve full polarization. The series-fed traveling-wave antenna was analyzed using periodic leaky-wave antenna theory. Summary of the Invention

[0004] The technical problem solved by the present invention is to overcome the deficiencies of the prior art and propose a fully polarized reconfigurable traveling wave series-fed array antenna composed of eccentric circular rings.

[0005] A fully polarized reconfigurable traveling wave serially fed array antenna composed of eccentric circular rings, the traveling wave serially fed array antenna comprising N unit structures, the N unit structures being serially fed and connected, where N=6-10;

[0006] Each unit structure includes an eccentric ring and a microstrip line. A notch is opened at the narrowest position of the eccentric ring. A microstrip line is connected to each end of the notch. The other end of the microstrip line serves as a feed port. The structure is as follows: Figure 1 shown.

[0007] The eccentric ring is composed of a large circle minus a small circle, the radius of the large circle is R1, the radius of the small circle is R2, R1>R2, the distance between the center of the large circle and the center of the small circle is a, a>0.

[0008] The notch opened at the narrowest position of the eccentric ring is a rectangular notch with a width of W1. One end of the rectangular notch is connected to one end of the first microstrip line M1, and the other end of the rectangular notch is connected to one end of the second microstrip line M1'. The other end of the first microstrip line M1 is connected to one end of the third microstrip line M2, and the other end of the second microstrip line M1' is connected to one end of the fourth microstrip line M2'. The other end of the third microstrip line M2 is set as port 1, and port 1 is fed. The other end of the fourth microstrip line M2' is set as port 2, and port 2 is fed.

[0009] The first microstrip line M1 has a width of W2 and a length of L1;

[0010] The second microstrip line M1' has a width of W2 and a length of L1;

[0011] The third microstrip line M2 has a width of W3 and a length of L2;

[0012] The fourth microstrip line M2' has a width of W3 and a length of L2;

[0013] And 2W2<W1.

[0014] The specific method of connecting the N unit structures in series is as follows:

[0015] The angle between the third microstrip line M2 of the first unit structure and the first microstrip line M1 is 360 / N°, the fourth microstrip line M2' of the first unit structure coincides with the third microstrip line M2 of the second unit structure, the fourth microstrip line M2' of the second unit structure coincides with the third microstrip line M2 of the third unit structure, the fourth microstrip line M2' of the third unit structure coincides with the third microstrip line M2 of the fourth unit structure, ..., and so on. The fourth microstrip line M2' of the N-1th unit structure coincides with the third microstrip line M2 of the Nth unit structure, and the angle between the fourth microstrip line M2' of the Nth unit structure and the second microstrip line M1' of the Nth unit structure is 360 / N°.

[0016] The angle between the first microstrip line M1 of the i-th unit structure and the third microstrip line M2 of the i-th unit structure is 110-130°;

[0017] The angle between the second microstrip line M1′ of the i-th unit structure and the fourth microstrip line M2′ of the i-th unit structure is 110-130°; i=2, 3, …, (N-1);

[0018] The included angle between the central axes of adjacent unit structures is 360 / N°.

[0019] Feeding different ports can achieve different forms of polarization, specifically:

[0020] (a) Right-hand circular polarization (RHCP): port 2 is fed and port 1 is connected to a matched load.

[0021] (b) Left-hand circular polarization (LHCP): port 1 is fed and port 2 is connected to a matched load;

[0022] (c) Vertical linear polarization (X-LP): Port 1 and port 2 are fed in the same phase;

[0023] (d) Horizontal linear polarization (Y-LP): Port 1 and port 2 are fed with a 180° phase difference.

[0024] The technical solution of the present invention is:

[0025] Beneficial effects

[0026] (1) Compared with concentric circular rings, the traveling wave series-fed array antenna of the present invention can better realize the circular polarization function with the eccentric circular ring, and the axial ratio parameter in the passband is lower than 3dB.

[0027] (2) The dual-port feeding of the traveling wave series-fed array antenna of the present invention allows for reconfiguration of the antenna's polarization mode. A reasonable feeding method can stimulate the generation of full polarization performance of the antenna (full polarization means that, through certain design methods, the antenna can achieve left-hand circular polarization (LHCP), right-hand circular polarization (RHCP), and linear polarization (LP) performance, and the several polarizations can be converted).

[0028] (3) The traveling wave series-fed array antenna of the present invention arranges the eccentric rings in a circular array, which can greatly reduce the antenna's usable area. The array antenna has the characteristics of polarization reconfigurability and high efficiency.

[0029] (4) The traveling wave series-fed array antenna of the present invention is processed and tested to obtain corresponding measured results. Within the passband range, the axial ratio of circular polarization is less than 3dB, and the isolation between the two ports is less than -15dB. The measured results are basically consistent with the simulation results.

[0030] (5) This invention adjusts the polarization of the antenna by adjusting the feed pattern, achieving full polarization reconfiguration. Next, the eccentric ring unit structure will be arranged in a circular array. This array antenna has a compact physical size and a large bandwidth. The tested transmission coefficient will be less than -15dB, and the circular polarization axis ratio will be less than 3dB. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the unit structure;

[0032] Figure 2 Schematic diagram of the composition of the traveling wave series fed array antenna;

[0033] Figure 3 Schematic diagram of the surface current direction of the unit structure: (a) right-hand circular polarization; (b) left-hand circular polarization; (c) X-linear polarization; (d) Y-linear polarization;

[0034] Figure 4 The current intensity trend at the same position of each unit structure;

[0035] Figure 5 Simulation and test results of array antenna S parameters;

[0036] Figure 6. Directional patterns of the array antenna at a frequency of 10 GHz. (a) Directional pattern of right-hand circular polarization (RHCP) (left, phi = 0°; right, phi = 90°); (b) Directional pattern of right-hand circular polarization (LHCP) (left, phi = 0°; right, phi = 90°); (c) Directional pattern of X-linear polarization (X-LP) (left, phi = 0°; right, phi = 90°); (d) Directional pattern of Y-linear polarization (Y-LP) (left, phi = 0°; right, phi = 90°);

[0037] Figure 7. Axial ratio and efficiency of the array antenna. (a) Circular polarization axial ratio; (b) Efficiency of the array antenna.

[0038] Figure 8. Gain diagrams of the antenna array. (a) Circular polarization gain; (b) Linear polarization gain. DETAILED DESCRIPTION

[0039] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0040] A fully polarization reconfigurable traveling wave series-fed array antenna composed of eccentric rings Figure 2 As shown, the traveling wave serial fed array antenna includes seven unit structures, which are respectively a first unit structure, a second unit structure, a third unit structure, a fourth unit structure, a fifth unit structure, a sixth unit structure, and a seventh unit structure;

[0041] Each unit structure includes an eccentric ring and a microstrip line. The eccentric ring is composed of a large circle minus a small circle. The radius of the large circle is R1, the radius of the small circle is R2, R1>R2, the distance between the center of the large circle and the center of the small circle is a, a>0, a rectangular notch is opened at the narrowest position of the eccentric ring, the width of the rectangular notch is W1, one end of the rectangular notch is connected to one end of the first microstrip line M1, the other end of the rectangular notch is connected to one end of the second microstrip line M1', the other end of the first microstrip line M1 is connected to one end of the third microstrip line M2, the other end of the second microstrip line M1' is connected to one end of the fourth microstrip line M2', the other end of the third microstrip line M2 is set as port 1, port 1 is fed, and the other end of the fourth microstrip line M2' is set as port 2, and port 2 is fed;

[0042] The first microstrip line M1 has a width of W2 and a length of L1;

[0043] The second microstrip line M1' has a width of W2 and a length of L1;

[0044] The third microstrip line M2 has a width of W3 and a length of L2;

[0045] The fourth microstrip line M2' has a width of W3 and a length of L2;

[0046] 2W2<W1;

[0047] The seven unit structures are connected in series, specifically:

[0048] The included angle between the third microstrip line M2 of the first unit structure and the first microstrip line M1 is 45°, the fourth microstrip line M2′ of the first unit structure coincides with the third microstrip line M2 of the second unit structure, the fourth microstrip line M2′ of the second unit structure coincides with the third microstrip line M2 of the third unit structure, the fourth microstrip line M2′ of the third unit structure coincides with the third microstrip line M2 of the fourth unit structure, the fourth microstrip line M2′ of the fourth unit structure coincides with the third microstrip line M2 of the fifth unit structure, the fourth microstrip line M2′ of the fifth unit structure coincides with the third microstrip line M2 of the sixth unit structure, the fourth microstrip line M2′ of the sixth unit structure coincides with the third microstrip line M2 of the seventh unit structure, and the included angle between the fourth microstrip line M2′ of the seventh unit structure and the second microstrip line M1′ of the seventh unit structure is 45°;

[0049] The angle between the first microstrip line M1 of the second unit structure and the third microstrip line M2 of the second unit structure is 110-130°;

[0050] The included angle between the second microstrip line M1' of the second unit structure and the fourth microstrip line M2' of the second unit structure is 110-130°;

[0051] The angle between the first microstrip line M1 of the third unit structure and the third microstrip line M2 of the second unit structure is 110-130°;

[0052] The included angle between the second microstrip line M1' of the third unit structure and the fourth microstrip line M2' of the second unit structure is 110-130°;

[0053] The included angle between the first microstrip line M1 of the fourth unit structure and the third microstrip line M2 of the second unit structure is 110-130°;

[0054] The included angle between the second microstrip line M1' of the fourth unit structure and the fourth microstrip line M2' of the second unit structure is 110-130°;

[0055] The angle between the first microstrip line M1 of the fifth unit structure and the third microstrip line M2 of the second unit structure is 110-130°;

[0056] The included angle between the second microstrip line M1' of the fifth unit structure and the fourth microstrip line M2' of the second unit structure is 110-130°;

[0057] The angle between the central axes of adjacent unit structures is 45°;

[0058] The center frequency of the traveling wave series-fed array antenna is 10 GHz, and the operating passband range is 9.4-10.7 GHz.

[0059] Example

[0060] The proposed unit structure is as follows Figure 1 As shown, the main structure includes an eccentric ring and a microstrip line. Figure 1 For the eccentric ring unit structure, W1 = 1.6 mm, W2 = 0.3 mm, W3 = , L1 = 4.6 mm, L2 = 7.3 mm, R1 = 6.4 mm, R2 = 3.0 mm; Figure 3 Instantaneous current distribution on a unit structure with different port feeding. (a) Right-hand circular polarization (RHCP): Port 2 is fed, and Port 1 is connected to a matched load; (b) Left-hand circular polarization (LHCP): Port 1 is fed, and Port 2 is connected to a matched load; (c) Vertical linear polarization (X-LP): Ports 1 and 2 are fed in phase; (d) Horizontal linear polarization (Y-LP): Ports 1 and 2 are fed 180° out of phase.

[0061] The surface instantaneous current distributions of the four polarizations are as follows Figure 3 (a)-(d) When port 1 is connected to a matched load and port 2 is fed, the main direction of the current is recorded from 0, T / 4, T / 2 to 3T / 4, with each T / 4 as a time unit, as shown in Figure 3As shown in (a), according to the record from top to bottom, then to right and finally to top in the small figure, the direction of the current rotates counterclockwise, thus generating right-hand circular polarization.

[0062] When port 2 is connected to a matched load and port 1 is fed, the main direction of the current is recorded from 0, T / 4, T / 2 to 3T / 4, with each T / 4 as a time unit, such as Figure 3 As shown in (b), according to the record from top to bottom, then to right and finally to top in the small figure, the direction of the current rotates clockwise, thus generating left-hand circular polarization.

[0063] When port 1 and port 2 are fed in the same phase, the main direction of the current from 0 to T / 2 is recorded with each T / 2 as a time unit, such as Figure 3 As shown in (c), as recorded from left to right in the small figure, the direction of the current is vertical, thus generating X-polarization.

[0064] like Figure 3 As shown in (d), when port 1 and port 2 are fed with a phase angle difference of π, the main direction of the current from 0 to T / 2 is recorded with each T / 2 as a time unit, as shown in Figure 3 As shown in (d), according to the recording from left to right in the small figure, the direction of the current is horizontal, thus generating Y-polarization.

[0065] Seven unit structures form an array antenna structure as follows Figure 2 As shown;

[0066] The seven-unit structure achieves full polarization reconfigurable performance by adjusting the feeding method. Fully polarized array antennas can be designed using these units. Figure 2 As shown in the figure, an array consisting of seven patch elements, a two-port microstrip feed, and a ground plane was designed and constructed. The angle between the patches was 45°. The ends of the array were connected to a microstrip line with a length of L3 and a width of W4, which was connected to a feed line with a length of L4 and a width of W3. The structure was simulated using the full-wave software Ansoft HFSS to verify the numerical results. The antenna was fabricated on a 1.5mm thick F4B dielectric board with a relative dielectric constant εr = 2.65 and a loss tangent tanδ = 0.0009. The array antenna pattern was fabricated on the upper layer of the dielectric board, and the lower layer was a full metal layer.

[0067] The radiated power P of each unit structure can be expressed as

[0068]

[0069] Among them, |S 11 | is a parameter in the scattering matrix [S], representing the reflection coefficient of port 1 when port 2 is matched, |S21 | is a parameter in the scattering matrix [S], representing the forward transmission coefficient from port 1 to port 2 when port 2 is matched;

[0070] When |S11| is small enough, formula (1) can be transformed into

[0071] P∝1-|S 21 | 2 (2)

[0072] From the above two formulas, it can be seen that the value of the power radiated by the unit is related to |S 21 | is related to the value of |. When |S 21 If the value of | is small enough, the radiation power of the unit structure will be very large. 21 |, improving the radiation efficiency of the unit structure is what needs to be done now. Therefore, we selected seven unit structures and connected them end to end, so that energy can be transmitted from one port to another. 21 | will decrease as the length of the antenna structure increases. This can be illustrated by the simulated surface current density on the microstrip line at the same point on each patch. The transmission coefficient |S between the two ports of the antenna 21 |will gradually decrease. Figure 4 The simulated magnitude of the surface current density at the same point on each unit cell;

[0073] Summary of array antenna test results:

[0074] (1) Antenna S parameters:

[0075] The antenna has been fabricated and tested to verify the simulation results. The measured and simulated S parameters of the array antenna are as follows: Figure 5 As shown. The relative bandwidth of the array antenna is 13%. In the frequency range of 9.4-10.7GHz, the reflection coefficient |S 11 | will be less than -10dB, the transmission coefficient |S 21 | will be less than -15dB. This indicates that the two ports of the array antenna have high isolation performance. The measured results of the antenna are in good agreement with the simulation results.

[0076] (2) Antenna pattern:

[0077] Figure 6(a), Figure 6(b), Figure 6(c), and Figure 6(d) show the array antenna at a frequency of 10 GHz. and Figure 6(a) RHCP, Figure 6(b) LHCP, Figure 6(c) X-LP, Figure 6(d) Y-LP. and On a plane, the measured 3dB beamwidths of the array antenna are 32° and 29° when circularly polarized (RHCP and LHCP) are formed. The sidelobe level is less than -10dB, which meets the general application requirements of modern communication systems. The main polarization is approximately 15dB higher than the cross-polarization. The simulation results are in good agreement with the measured results. and In the plane, the array antenna forms linear polarizations (X-LP and Y-LP), with measured 3dB beamwidths of approximately 25° and 36°. The main polarization is approximately 10dB higher than the cross-polarization. Due to the use of a power divider and some lossy transmission line feeds during testing, the measured results differ slightly from the simulation results.

[0078] (3) Axis ratio, efficiency, and gain of the array antenna;

[0079] Typically, axial ratio (AR) measurements are used to examine circular polarization characteristics. Figure 7(a) shows the simulated and tested axial ratios for the circular array in the aforementioned frequency bands. The 3dB axial ratio bandwidth ranges from 9.4 to 10.7 GHz (13%). The simulations accounted for losses in the metal surface and dielectric material to determine antenna efficiency. Figure 7(b) shows the simulated radiation efficiency averaged 91.4% across the circular array antenna bandwidth.

[0080] Figures 8(a) and 8(b) show the simulated and measured gains of the antenna for circular and linear polarization. In Figure 8(a), the measured actual gain for circular polarization at a center frequency of 10 GHz is 11.5 dB; in Figure 8(b), the measured actual gain for linear polarization at 10 GHz is 11 dB. Within the passband, the actual gain is greater than 6 dB for all polarization modes.

[0081] This paper proposes a fully polarization-reconfigurable, high-efficiency traveling-wave series-fed array antenna. First, a polarization-reconfigurable eccentric circular ring unit structure is proposed. Through appropriate port excitation, fully polarization-reconfigurable performance can be achieved. The unit structures are then arranged into a circular array. Within the passband, the transmission coefficient is below -15 dB, and the measured axial ratio is below 3 dB. Simulation results agree well with measured results, validating the design.

Claims

1. A fully polarized reconfigurable traveling-wave series-fed array antenna composed of eccentric rings, characterized by: The traveling wave serially fed array antenna comprises N unit structures, which are serially fed and connected, where N=6~10; Each unit structure includes an eccentric ring and a microstrip line. A notch is opened at the narrowest position of the eccentric ring. The two ends of the notch are connected to a microstrip line, and the other end of the microstrip line serves as a feeding port. The eccentric ring is composed of a large circle minus a small circle, the radius of the large circle is R1, the radius of the small circle is R2, R1>R2, the distance between the center of the large circle and the center of the small circle is a, a>0; The notch opened at the narrowest position of the eccentric ring is a rectangular notch, the width of the rectangular notch is W1, one end of the rectangular notch is connected to one end of the first microstrip line M1, the other end of the rectangular notch is connected to one end of the second microstrip line M1', the other end of the first microstrip line M1 is connected to one end of the third microstrip line M2, the other end of the second microstrip line M1' is connected to one end of the fourth microstrip line M2', the other end of the third microstrip line M2 is set as port 1, port 1 is fed, and the other end of the fourth microstrip line M2' is set as port 2, port 2 is fed; The first microstrip line M1 has a width of W2 and a length of L1; The second microstrip line M1' has a width of W2 and a length of L1; The third microstrip line M2 has a width of W3 and a length of L2; The fourth microstrip line M2' has a width of W3 and a length of L2; And 2W2<W1; The specific method of connecting N unit structures in series is: The angle between the third microstrip line M2 of the first unit structure and the first microstrip line M1 is 360° / N. The fourth microstrip line M2' of the first unit structure coincides with the third microstrip line M2 of the second unit structure. The fourth microstrip line M2' of the second unit structure coincides with the third microstrip line M2 of the third unit structure. The fourth microstrip line M2' of the third unit structure coincides with the third microstrip line M2 of the fourth unit structure. By analogy, the fourth microstrip line M2' of the N-1th unit structure coincides with the third microstrip line M2 of the Nth unit structure. The angle between the fourth microstrip line M2' of the Nth unit structure and the second microstrip line M1' of the Nth unit structure is 360° / N. The angle between the first microstrip line M1 of the i-th unit structure and the third microstrip line M2 of the i-th unit structure is 110°~130°; The angle between the second microstrip line M1′ of the i-th unit structure and the fourth microstrip line M2′ of the i-th unit structure is 110° to 130°; i=2, 3, …, N-1; The angle between the central axes of adjacent unit structures is 360° / N; Feeding different ports can achieve different forms of polarization, specifically: (a) Right-hand circular polarization: port 2 is fed and port 1 is connected to a matched load; (b) Left-hand circular polarization: port 1 is fed and port 2 is connected to a matched load; (c) Vertical linear polarization: Port 1 and Port 2 are fed in the same phase; (d) Horizontal linear polarization: Port 1 and Port 2 are fed with a 180° phase difference.

Images