An all-space high-scan-rate leaky-wave antenna based on odd-mode sspp

Abstract

This invention discloses a full-space high-scan-rate leaky-wave antenna based on odd-mode SSPP, belonging to the field of microwave antenna technology. The antenna includes a dielectric substrate, odd-mode feed structures disposed at both ends of the dielectric substrate, a gradient transition structure connected to the odd-mode feed structures, a complementary slip-symmetric SSPP transmission line connected between the gradient transition structures, and periodic metallic radiating stubs symmetrically loaded on both sides of the SSPP transmission line. The antenna of this invention uses odd-mode excitation to achieve strong end-direction radiation, combined with a slip-symmetric structure to suppress the stopband and improve the scan rate; by optimizing the modulation period to meet single-harmonic operating conditions, higher-order harmonic sidelobes are eliminated. This invention achieves full-space scanning of -90° to +90° within a 4~4.65GHz bandwidth, with a scan rate of 11.95° / s, an average efficiency of 88%, and an average gain of 8.8dBi. It has a compact structure, is easy to manufacture, and is suitable for systems such as vehicle-mounted radar and microwave imaging.

Description

Technical Field

[0001] This invention belongs to the field of antenna theory analysis and technology, and relates to a full-space high scan rate leaky wave antenna based on odd-mode SSPP. Specifically, it relates to an artificial surface plasmon polariton (SSPP) leaky wave antenna based on complementary slip symmetry structure and odd-mode excitation, which can realize full-space scanning from back-fire to end-fire. Background Technology

[0002] Leaky-wave antennas, as a type of traveling-wave antenna, possess advantages such as simple structure, high gain, and good frequency scanning characteristics, and are widely used in systems such as automotive radar, wireless communication, electromagnetic imaging, real-time spectrum analysis, and analog signal processing. Traditional leaky-wave antennas mostly adopt planar microstrip structures, which can achieve forward and backward beam scanning, but because the dispersion curve is close to that of free-space waves, the scanning range is narrow and it is difficult to cover the entire spatial range from back-fired (-90°) to end-fired (+90°); if a high-dielectric-constant substrate is used to extend the scanning angle, the efficiency will be limited.

[0003] To achieve full-space scanning, existing technologies mainly employ two approaches: one relies on ultra-wideband design, using tens of GHz of ultra-wideband frequency scanning to cover the entire angle, but this results in excessively large antenna electrical dimensions and difficulties in system integration; the other uses miniaturization to reduce volume, but this significantly reduces average radiation efficiency and gain. Furthermore, the above approaches suffer from low scanning rates due to the small beam deflection angle caused by unit frequency changes, making it impossible to simultaneously meet the application requirements of high scanning rates and large scanning ranges.

[0004] Artificial surface plasmon polariton (SSPP) transmission lines possess controllable dispersion characteristics, enabling wide-angle scanning and high scan rates, providing a new approach to overcoming the aforementioned bottlenecks. SSPP is an artificial electromagnetic mode that simulates the characteristics of optical surface plasmon polaritons (SPP) by being excited at the metal-dielectric interface through a periodic subwavelength metal structure in the microwave, millimeter-wave, and terahertz frequency bands. It belongs to the slow-wave transmission mode. Its wave vector is much larger than the free-space wave vector, and the electromagnetic field is highly confined near the structure surface, exhibiting exponential decay. It possesses advantages such as strong dispersion, slow-wave transmission, strong field confinement, and miniaturization. The dispersion characteristics can be flexibly controlled through structural geometric parameters. However, traditional SSPP leaky-wave antennas struggle to simultaneously achieve full-angle continuous scanning, high scan rates, and high radiation efficiency. Furthermore, their poor end-fire radiation performance and the tendency for high-order spatial harmonics to cause sidelobe deterioration limit their engineering applications.

[0005] Therefore, developing a leaky wave antenna that combines full-space scanning, high scanning rate, high efficiency, and low profile has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a full-space high-scan-rate leaky antenna based on odd-mode SSPP, which solves the problems of narrow scanning range, low scanning rate, poor end-fire radiation, and low efficiency of traditional leaky antennas. By adopting complementary sliding symmetrical SSPP transmission lines, dispersion is further enhanced and stopband is suppressed. Combined with odd-mode excitation and periodic modulation, full-space continuous scanning from −90° to +90° is achieved, while maintaining high scanning rate and high radiation efficiency.

[0007] To achieve the above objectives, the present invention employs the following technical solutions:

[0008] A full-space high-scan-rate leaky-wave antenna based on odd-mode SSPP, comprising:

[0009] Dielectric substrate;

[0010] Odd-mode feeding structures are set at both ends of the dielectric substrate to introduce differential signals and excite the generation of odd-mode artificial surface plasmons;

[0011] A gradient transition structure connected to the odd-mode feed structure is used to achieve wave vector matching;

[0012] A complementary slip-symmetric SSPP transmission line is connected between the gradient transition structures. The transmission line is composed of a top layer metal unit and a bottom layer metal unit arranged in a complementary slip-symmetric distribution.

[0013] And periodic metallic radiating branches symmetrically loaded on both sides of the complementary slip-symmetric SSPP transmission line.

[0014] Furthermore, the odd-mode feeding structure employs a double-sided parallel stripline, which introduces a 180° phase-shifted signal into the upper and lower layers of the dielectric substrate to excite the odd-mode SSPP mode.

[0015] Furthermore, the gradient transition structure achieves momentum matching through a gradual change in slot depth, efficiently coupling the electromagnetic waves guided by the odd-mode feed structure to the complementary slip-symmetric SSPP transmission line.

[0016] Furthermore, the top and bottom metal units of the complementary slip-symmetric SSPP transmission line are staggered by half a period along the propagation direction to form a slip-symmetric structure, thereby enhancing dispersion characteristics and suppressing the stopband at the cutoff frequency.

[0017] Furthermore, the top metal unit includes a transverse trunk and a bent metal strip extending inward from the trunk with multiple bends, the bent metal strip having an "S"-shaped structure; the bottom metal unit has the same shape as the top metal unit, but is rotated 180° relative to the top unit and translated half a cycle along the propagation direction.

[0018] Furthermore, the SSPP slow wave is periodically modulated by the periodic metallic radiation stubs, allowing electromagnetic wave energy to enter the fast wave region and generate full-space beam scanning.

[0019] Furthermore, the dielectric substrate is made of Rogers 4003 material with a dielectric constant of 3.55, a loss tangent of 0.0027, and a thickness of 0.813 mm.

[0020] Furthermore, by using odd-mode excitation to make the equivalent current perpendicular to the propagation direction, it is equivalent to an electric dipole array placed perpendicularly along the propagation direction, thereby eliminating the radiation zero point in the end-fire direction and enhancing the end-fire radiation performance.

[0021] Compared with the prior art, the advantages of the present invention are as follows:

[0022] (1) This invention achieves periodic modulation by loading metal branches on both sides of the transmission section, thereby converting slow electromagnetic waves into fast waves. By adjusting the modulation period, only the -1st harmonic participates in radiation within the working frequency band, eliminating sidelobe deterioration and beam splitting caused by higher harmonics, making the antenna radiation directivity purer, with stable gain and efficiency. The antenna efficiency is higher than 75%, with an average efficiency of 88% and an average gain of 8.8 dBi.

[0023] (2) The groove depth of the present invention is linearly gradually changing transition section, which connects the odd mode feed and the transmission section to achieve continuous matching of wave vector and momentum, and avoid reflection caused by mode change;

[0024] (3) The present invention uses Rogers 4003 dielectric substrate and surface anti-oxidation metal process. The low dielectric constant and low loss angle of the dielectric substrate reduce dielectric loss and conductor loss, while the anti-oxidation coating stabilizes impedance and reduces contact resistance, ultimately making the antenna low profile, easy to process, and suitable for mass production.

[0025] (4) This invention uses a double-sided parallel stripline differential feed to introduce a 180° phase difference signal between the upper and lower layers of the dielectric substrate. The equivalent current is perpendicular to the transmission direction, and the transmission section is equivalent to an electric dipole array arranged perpendicularly along the propagation direction, which completely eliminates the zero point of radiation in the end-fire direction. Combined with the frequency scanning characteristics of the leaky antenna itself, it realizes full-space beam scanning. Moreover, this design greatly simplifies the structure and significantly reduces the structural complexity while ensuring good performance.

[0026] (5) By arranging multiple antenna elements in the antenna transmission section, the present invention can form an array to achieve higher gain and a wider beam scanning range;

[0027] (6) This invention suppresses the open stopband effect at the side firing frequency by using a sliding symmetric topology, avoids transmission breakpoints, and achieves compatibility between high dispersion and low loss.

[0028] (7) The present invention extends the current path by increasing the groove depth and bending the short stub to form an "S" type unit, which increases the slow wave effect of the unit, reduces the slope of the dispersion curve, and also reduces the operating frequency of the unit (i.e. the cutoff frequency of the dispersion curve). By reducing the slope and cutoff frequency of the dispersion curve, the scanning rate is greatly improved. Attached Figure Description

[0029] Figure 1 This is a top view of the overall structure of the full-space high-scan-rate leaky wave antenna described in this invention.

[0030] Figure 2 This is a schematic diagram of the complementary slip-symmetric SSPP unit structure in a full-space high-scan-rate leaky wave antenna.

[0031] Figure 3 The dispersion curve is for a complementary slip-symmetric SSPP unit structure;

[0032] Figure 4 This is a top view of the overall structure of the full-space high-scan-rate leaky antenna before modulation, as described in this invention, wherein region I: odd-mode feeding structure, region II: gradient transition structure, and region III: SSPP transmission line;

[0033] Figure 5 In the middle (a), the S-parameters are before modulation by the full-space high-scan-rate leaky-wave antenna; (b) are after modulation by the full-space high-scan-rate leaky-wave antenna.

[0034] Figure 6 It is the radiation pattern of a high-scan-rate leaky-wave antenna in all space;

[0035] Figure 7 It is the gain curve of a full-space high-scan-rate leaky-wave antenna;

[0036] Figure 8 It is the efficiency curve of a full-space high-scan-rate leaky-wave antenna. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail with reference to specific examples and accompanying drawings. However, the present invention is not limited to these embodiments.

[0038] like Figure 1As shown, the present invention provides a full-space high-scan-rate leaky antenna based on odd-mode SSPP, including a dielectric substrate, an odd-mode feeding structure, a gradient transition structure, a complementary slip-symmetric SSPP transmission line, and periodic metallic radiating stubs.

[0039] The dielectric substrate is made of Rogers 4003 material with a dielectric constant of [missing information]. =3.55, loss tangent =0.0027, thickness 0.813mm; the odd-mode power supply structure is matched with an SMA connector. Impedance is introduced through a double-sided parallel stripline to introduce a differential signal, achieving a 180° phase shift up and down on the transmission line to excite the odd-mode SSPP.

[0040] The gradient transition structure achieves wave vector matching through a gradual change in slot depth, connecting the feed structure and the SSPP transmission line.

[0041] The complementary slip-symmetric SSPP transmission line is composed of periodically arranged upper and lower slip-symmetric SSPP units; the structural diagram of the SSPP unit is shown below. Figure 2 As shown, its dispersion curve is as follows Figure 3 As shown, the smaller the slope, the lower the cutoff frequency, indicating that the unit can achieve a higher scanning rate. The slope of the dispersion curve and the cutoff frequency can be adjusted by adjusting the groove depth h. Finally, a groove depth of 6mm and a cutoff frequency of 4.74GHz were selected.

[0042] The periodic metallic radiation stubs are symmetrically loaded on both sides of the SSPP transmission line, and their period is adjusted to modulate the SSPP unit so that the slow wave on the transmission line can be radiated.

[0043] The antenna has a total length of 7.63 wavelengths and features a low profile; the antenna operates with a bandwidth of 4~4.65GHz and a scanning rate of 11.98° / ; the antenna has an average radiation efficiency of 88% and an average gain of 8.8dBi.

[0044] In the above technical solution, by controlling the modulation period, the -1st harmonic in the fast wave region is ensured to work independently, and the overlap of the -2nd harmonic is avoided to prevent the sidelobe from being caused.

[0045] In the above technical solution, a bimodal excited two-conductor transmission line is used, with the upper and lower electric fields out of phase and the equivalent current perpendicular to the transmission direction. This is equivalent to an electric dipole array placed perpendicularly along the propagation direction, achieving efficient radiation in the end-fire direction and avoiding the zero-point radiation problem in the end-fire direction of the bimodal excited line.

[0046] In the above technical solution, the complementary slip-symmetric structure excites a strong dispersive fundamental mode, thereby increasing the scanning rate; the slip-symmetric characteristics suppress the stopband at the cutoff frequency, achieving compatibility between high dispersion and low loss.

[0047] like Figure 1 , 2 As shown, the specific parameters of the structure of this invention are as follows: dielectric substrate width W = 60 mm, length L = 280.8 mm, metal thickness hm = 0.035 mm, dielectric substrate h = 0.813 mm. The top metal layer of the odd-mode feeding structure has a width W0 = 1.9 mm, the bottom metal layer has a width W1 = 10.3 mm, and a length L0 = 11 mm. The total length L of the gradient transition structure is... v = L1 + L2 + L3 = 29.4mm, SSPP transmission structure L4 = 200mm. Unit structure w0 = 2mm, h = 6mm, w1 = 1mm, w2 = 1mm, w3 = 1mm, w4 = 1mm, w5 = 1mm, h0 = 3mm, h2 = 2mm, period p = 4mm. Modulation period P p =20mm, metal branch width W pp =1.5mm, length L pp =13mm.

[0048] Figure 4 This is a diagram of the basic transmission line structure before modulation. Figure 1 exist Figure 4 Based on this, metal branches are periodically added to the SSPP transmission line section to modulate the SSPP slow wave and enable its radiation; the S-parameters before and after modulation are as follows: Figure 5 As shown, before modulation, S11 rises rapidly and S21 falls rapidly at the cutoff frequency of 4.74 GHz; after modulation, S11 < -10 dB and S21 < -10 dB in the 4~4.65 GHz band, proving that the leaky antenna radiates.

[0049] Figure 6 The radiation pattern of the antenna of this invention achieves full-space scanning in the 4~4.65GHz frequency band, with a scanning rate of 11.98° / .

[0050] Figure 7 and Figure 8 The figures show the gain and efficiency curves of the antenna of this invention, with an average efficiency of 88% and an average gain of 8.8 dBi.

[0051] The design steps of this invention are as follows: First, a complementary slip-symmetric SSPP unit is designed, and the structure is adjusted as much as possible to reduce the slope of its dispersion curve and the cutoff frequency in order to improve its scanning rate; Second, metal stubs are loaded, and the period of the metal stubs is adjusted to achieve single harmonic radiation in the fast wave region, and then combined with odd-mode excitation of parallel double-sided strip lines to achieve full-space scanning; Finally, the structural parameters are optimized to maximize gain and efficiency.

[0052] The above description is merely one embodiment of the present invention, intended only to aid in understanding the method and core ideas of the invention. The unit structure design concept proposed in this invention can also be applied to other types of leaky antennas. It should be noted that those skilled in the art can make improvements to the invention without departing from its principles, and these improvements will also fall within the scope of protection of the claims. The present invention is not limited to the specific embodiments described. For those skilled in the art, any changes within the spirit and scope of the invention as defined and determined by the appended claims are obvious, and all inventions utilizing the concept of this invention are protected.

Claims

1. A full-space high-scan-rate leaky-wave antenna based on odd-mode SSPP, characterized in that, include: Dielectric substrate; Odd-mode feeding structures are set at both ends of the dielectric substrate to introduce differential signals and excite the generation of odd-mode artificial surface plasmons; A gradient transition structure connected to the odd-mode feed structure is used to achieve wave vector matching; A complementary slip-symmetric SSPP transmission line is connected between the gradient transition structures. The transmission line is composed of a top layer metal unit and a bottom layer metal unit arranged in a complementary slip-symmetric distribution. And periodic metallic radiating branches symmetrically loaded on both sides of the complementary slip-symmetric SSPP transmission line.

2. The all-space high scan rate leaky antenna based on odd-mode SSPP according to claim 1, characterized in that, The odd-mode feeding structure uses a double-sided parallel stripline, and introduces a 180° phase-shifted signal into the upper and lower layers of the dielectric substrate to excite the odd-mode SSPP mode.

3. The all-space high scan rate leaky antenna based on odd-mode SSPP according to claim 1, characterized in that, The gradient transition structure achieves momentum matching through a gradual change in slot depth, efficiently coupling the electromagnetic waves guided by the odd-mode feed structure to the complementary slip-symmetric SSPP transmission line.

4. The all-space high scan rate leaky antenna based on odd-mode SSPP according to claim 1, characterized in that, The top and bottom metal units of the complementary slip-symmetric SSPP transmission line are staggered by half a period along the propagation direction to form a slip-symmetric structure.

5. The all-space high scan rate leaky antenna based on odd-mode SSPP according to claim 4, characterized in that, The top metal unit includes a transverse trunk and a bent metal strip extending inward from the trunk with multiple bends, the bent metal strip having an "S"-shaped structure; the bottom metal unit has the same shape as the top metal unit, but is rotated 180° relative to the top unit and translated half a cycle along the propagation direction.

6. The all-space high scan rate leaky antenna based on odd-mode SSPP according to claim 1, characterized in that, The SSPP slow wave is periodically modulated by the periodic metallic radiation stubs, allowing electromagnetic wave energy to enter the fast wave region and generate full-space beam scanning.

7. The all-space high scan rate leaky antenna based on odd-mode SSPP according to claim 1, characterized in that, The dielectric substrate is made of Rogers 4003 material with a dielectric constant of 3.55, a loss tangent of 0.0027, and a thickness of 0.813 mm.

8. The all-space high scan rate leaky antenna based on odd-mode SSPP according to any one of claims 1-7, characterized in that, By using odd-mode excitation to make the equivalent current perpendicular to the propagation direction, it is equivalent to an array of electric dipoles placed perpendicularly along the propagation direction, thereby eliminating the radiation zero point in the end-fire direction and enhancing the end-fire radiation performance.

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