Wide bandwidth and angular scanning open waveguide phased array antenna

Abstract

The present invention belongs to the field of antenna technology, and specifically is an open waveguide phased array antenna with wide bandwidth and wide angle scanning. The array is composed of rectangular open waveguide antenna units arranged in a regular triangle grid. A surface modulation structure is loaded at the array aperture, including a pyramid-shaped dielectric protrusion structure and a conical metal sidewall. The pyramid-shaped dielectric protrusion is used as an impedance gradient structure to achieve wide-angle scanning impedance matching; the conical metal sidewall is used as an electromagnetic bandgap structure to generate a surface wave bandgap and suppress scanning blind spots within the working frequency band. The array can achieve scanning of more than ±65° on the main plane within 40% of the working bandwidth, with a compact structure and high reliability.

Description

Technical Field

[0001] The invention belongs to the technical field of antennas, and in particular relates to an open waveguide phased array antenna. Background Art

[0002] Metal waveguide antennas have been widely used in radar, communication, radio astronomy and other fields due to their simple structure, low loss and high gain, high reliability, large power capacity and easy processing. Waveguide antennas can be used as high-gain fixed-beam array antennas by slitting slots on their metal side walls. They can also form frequency scans in one dimension or form phase scans by arranging multiple waveguides side by side. However, due to their strong resonance characteristics, slot antennas have a narrow working bandwidth and are difficult to form two-dimensional phased scanning.

[0003] Phased array antennas have been widely used in military and civilian fields in recent years due to their advantages such as high data rate and fast and accurate beam agility. Different from the slits on the side wall of the waveguide, the two-dimensional arrangement of the open waveguides can form a two-dimensional phased array antenna. However, after the waveguides are arrayed, the characteristics of the antenna are very different from those of a single antenna due to the mutual coupling effect. On the one hand, the mutual coupling will cause the active impedance of the array to change greatly when scanning at a large angle, resulting in impedance mismatch at the input port, which seriously affects the radiation efficiency. On the other hand, due to the presence of the surface wave mode at the waveguide mouth, the Floquet mode and the surface wave mode are strongly coupled at a certain angle, resulting in a "scanning blind spot", which is manifested as a complete mismatch of the antenna port impedance and an active reflection coefficient close to 1. Over the years, people have tried many methods to improve the wide-bandwidth and angular scanning capability of waveguide arrays, such as the use of metal matching diaphragms, dielectric plug loading, and wide-angle impedance matching layers. These methods can only achieve wide-angle impedance matching of the array within a narrow bandwidth. The use of dielectric coatings will further aggravate the high-frequency surface wave effect, causing the scanning blind spot to move to low frequencies, thereby affecting the scanning performance of the array. Summary of the invention

[0004] In order to solve the deficiencies of the prior art, the present invention provides a wide-bandwidth and wide-angle scanning open waveguide phased array antenna with surface structure modulation, which can simultaneously solve the array wide-angle scanning impedance mismatch problem and the scanning blind spot problem caused by surface waves.

[0005] The wideband wide angle scanning open waveguide phased array antenna provided by the present invention is an M×N two-dimensional array (M and N are equal or unequal) formed by arranging a number of rectangular open waveguide antenna units in the form of an equilateral triangle grid; the array body adopts a metal structure and is filled with dielectric materials. The basic shape of the antenna unit is a rectangular prism, which is composed of three sections, from top to bottom: a surface modulation structure, a rectangular waveguide with a dielectric filling block, and a feeding network. The antenna unit is excited and fed at the bottom through a coaxial connector, and the bottom of the array is fixed by a metal floor.

[0006] The array described in the present invention adopts an equilateral triangle grid arrangement, which means that in the array, in the same row direction, the antenna units are arranged in sequence; and between two adjacent rows, the central axes of three adjacent antenna units are distributed in an equilateral triangle, and the positions of the antenna units in the two alternate rows are aligned; see Figure 5 Such an arrangement of array antennas can maximize the waveguide aperture and reduce the waveguide cutoff frequency without introducing grating lobes.

[0007] In the present invention, the rectangular open waveguide antenna unit is a single-line polarization working antenna, and the main mode is TE 10 model.

[0008] The material of the dielectric filling block in the rectangular waveguide is a low-loss dielectric material with a dielectric constant greater than 1, which can reduce the cutoff frequency of the main mode of the waveguide and broaden its working bandwidth in the array.

[0009] In the present invention, the surface modulation structure is the core of the present invention, and includes a pyramid-shaped dielectric protrusion structure and a triangular metal sidewall. Here, the so-called pyramid-shaped dielectric protrusion structure is actually a tetrahedron, and the bottom of the tetrahedron is a rectangle that matches the rectangular waveguide; the metal sidewall on the wide side of the tetrahedron is two isosceles triangles of the same structure arranged side by side (the base length of the waist triangle is 1 / 2 of the length of the wide side of the tetrahedron), and the metal sidewall on the narrow side of the tetrahedron is an isosceles triangle (the base length of the waist triangle is the same as the length of the narrow side of the tetrahedron).

[0010] In the surface modulation structure, the heights of the pyramid-shaped dielectric protrusion structure and the triangular metal sidewall are approximately the same and are approximately half the wavelength of the center frequency.

[0011] The pyramid-shaped dielectric protrusion is used as an impedance gradient structure to achieve wide-angle scanning impedance matching; the triangular metal sidewall is used as an electromagnetic bandgap structure to generate a surface wave bandgap and suppress the scanning blind spot within the working frequency band. The height of the pyramid-shaped dielectric protrusion structure and the triangular metal sidewall is crucial. When the height is approximately the same and about half the wavelength of the center frequency, the array can achieve the best performance.

[0012] In the present invention, the feeding network comprises three parts: a coaxial input section, a mode conversion section and an impedance transformation section. The coaxial input section can be realized by a standard SMP coaxial connector; the mode conversion section comprises a circular coaxial line inner conductor, a square coaxial line inner conductor and a ridge adapter section, which is used to realize the transformation of the TEM mode in the circular coaxial line to the TEM mode in the square coaxial line, and further realizes the transformation to TE through the ridge adapter section. 10 The impedance matching section is realized by a fourth-order Chebyshev impedance transformer.

[0013] In the present invention, the various sections of the antenna unit are interconnected structures, which are simple and compact and are conducive to large-scale deployment.

[0014] In the present invention, the dielectric filling structure and the pyramid dielectric protrusion structure in the rectangular waveguide can be made into an integrated dielectric filling block and filled inside the waveguide by physical limiting. For ease of assembly, the square coaxial line and the ridge adapter section are both filled with air as the filling dielectric material, but no dielectric material is actually filled.

[0015] In the present invention, the metal floor is used to reflect electromagnetic waves, reduce backward radiation, and avoid mutual influence between rear-end electronic devices and front-end array antennas.

[0016] The open waveguide array provided by the present invention can avoid scanning blind spots in the entire desired working frequency band and achieve perfect scanning impedance matching over 65°. 10 The cut-off frequency is the frequency at which the array grating lobe appears. The antenna structure including the feed network is tuned as a whole by electromagnetic simulation software, and the array can finally achieve a 40% operating bandwidth while scanning more than ±65° in the main plane. With the help of the surface modulation structure, the array achieves excellent wide-bandwidth angular scanning performance with a compact structure and high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is an oblique view of the open waveguide antenna unit structure.

[0018] Figure 2 Broadside view of the open waveguide antenna unit structure.

[0019] Figure 3 This is a narrow side view of the open waveguide antenna unit structure.

[0020] Figure 4 A structural diagram of a medium filling block.

[0021] Figure 5 Schematic diagram of the 11×11 array structure.

[0022] Figure 6 It is the standing wave diagram of E surface under periodic boundary conditions.

[0023] Figure 7 It is the standing wave diagram of H surface under periodic boundary conditions.

[0024] Figure 8 This is the 10 GHz scanning pattern of the E plane of the 11×11 array.

[0025] Fig. 9 This is the 10 GHz scanning pattern of the H-plane of the 11×11 array.

[0026] Numbers in the figure: 1 is a circular coaxial line, 2 is an inner conductor of the circular coaxial line, 3 is a square coaxial line, 4 is an inner conductor of the square coaxial line, 5 is a ridge adapter section, 6 is a fourth-order Chebyshev transformer, 7 is a dielectric filling block in the waveguide, 8 is a wide-side tapered metal side wall, 9 is a narrow-side tapered metal side wall, 10 is a pyramid-shaped dielectric protrusion structure, 11 is a narrow-side side wall of the waveguide, 12 is a matching groove, 13 is a metal floor, and 14 is a wide-side side wall of the waveguide. DETAILED DESCRIPTION

[0027] like Figure 1 The figure shows the unit structure diagram of the open waveguide array antenna. The antenna is composed of two materials. The outer wall of the waveguide and the inner circular coaxial line conductor 2, the square coaxial line conductor 4, the ridge adapter section 5, and the fourth-order Chebyshev transformer 6 are all metal structures. The dielectric filling block 7 and the pyramid-shaped dielectric protrusion structure 10 in the waveguide are made of polytetrafluoroethylene with a dielectric constant of 2.2. Both the metal structure and the dielectric structure are processed by CNC machine tools. In actual use, each antenna unit is excited by the SMP coaxial connector, and the electromagnetic energy is converted into the TE mode in the rectangular waveguide through the circular coaxial line 1, the square coaxial line 3, the ridge adapter section 5, and the fourth-order Chebyshev transformer 6 in turn, and radiates outward through the waveguide mouth. The excitation phase of each waveguide unit can be adjusted at the input, so that the array as a whole can achieve beam scanning.

[0028] Since the array is arranged in a regular triangle grid, the triangular metal parts 8 and 9 are difficult to be processed and formed integrally with the waveguide array. In the expected operating frequency band of 8 GHz to 12 GHz, the thickness of the narrow side wall of the waveguide is only about 0.6 mm to 1 mm, and the height of the tapered metal side walls 8 and 9 is consistent with the pyramid-shaped dielectric protrusion structure 10, which is about 14 mm. The processing of the entire array adopts the method of block processing and assembly molding. The processed parts mainly include metal floor 13, integrated internal metal block (including square coaxial line inner conductor 4, ridge adapter section 5, fourth-order Chebyshev transformer 6), integrated dielectric filling block (including waveguide inner dielectric filling block 7 and pyramid-shaped dielectric protrusion structure 10), waveguide narrow side wall metal sheet (including narrow side tapered metal side wall 9 and waveguide narrow side wall 11) and waveguide wide side wall metal sheet 14.

[0029] like Figure 2 He Ru Figure 3 As shown, the wide side of the waveguide includes two triangular metal side walls 8, and the narrow side of the waveguide includes a triangular metal side wall 9. Figure 3 The narrow tapered metal side wall 9 and the waveguide narrow side wall 11 are integrated metal sheet structures. Figure 5The waveguide wide side wall metal sheet 14 is a whole row of sheet metal structures. The narrow side metal sheet structures (9 and 11) are located between multiple rows of wide side wall metal sheets 14 through grooves, and the wide side wall metal sheets 14 are fixed to the metal floor 13 by screws.

[0030] Figure 4 The integrated dielectric filling block shown includes a dielectric filling block 7 in a waveguide and a pyramid-shaped dielectric protrusion structure 10, and a matching groove 12 is provided at the bottom for matching with a fourth-order Chebyshev transformer 6. For ease of processing, the matching groove 12 and the fourth-order Chebyshev transformer 6 are both chamfered.

[0031] Figure 1 The integrated internal metal block shown comprises a square coaxial line inner conductor 4, a ridge adaptor section 5, and a fourth-order Chebyshev transformer 6. After the integrated internal metal block is assembled with the integrated dielectric filling block, it is physically confined in the waveguide.

[0032] Figure 6 It is the standing wave diagram of the E-plane under periodic boundary conditions. It can be seen from the figure that the standing wave of the antenna is less than 2.3 within the 65° scanning range of the E-plane in the entire working frequency band (8 GHz to 12 GHz).

[0033] Figure 7 It is the standing wave diagram of the H-plane under periodic boundary conditions. It can be seen from the figure that the standing wave of the antenna is lower than 2.0 within the 65° scanning range of the H-plane in the entire working frequency band (8 GHz to 12 GHz).

[0034] Figure 8 and Fig. 9 These are the beam scanning patterns of the E-plane and H-plane of the 11×11 array at the center frequency of 10 GHz. The results show that the array can scan up to 65°.

Claims

1. A wideband angular scanning open waveguide phased array antenna, characterized in that: An M×N two-dimensional array formed by a number of rectangular open waveguide antenna units arranged in a regular triangle grid; wherein the antenna unit is in the shape of a rectangular prism and consists of three sections, from top to bottom: a surface modulation structure, a rectangular waveguide with a dielectric filling block, and a feeding network; the antenna unit is excited and fed at the bottom through a coaxial connector, and the bottom of the array is fixed by a metal floor; The array is arranged in an equilateral triangle grid, which means that in the array, in the same row direction, the antenna units are arranged in sequence; and between two adjacent rows, the central axes of three adjacent antenna units are distributed in an equilateral triangle, and the positions of the antenna units in the two alternate rows are aligned; The material of the dielectric filling block in the rectangular waveguide is a low-loss dielectric material with a dielectric constant greater than 1; The rectangular open waveguide antenna unit is a single-line polarization working antenna, and the main mode is TE 10 model; The surface modulation structure comprises a pyramid-shaped dielectric protrusion structure and a triangular metal sidewall; the so-called pyramid-shaped dielectric protrusion structure is a quadrangular pyramid, the bottom of which is a rectangle matching the rectangular waveguide; the metal sidewall on the wide side of the quadrangular pyramid is two isosceles triangles of the same structure arranged in parallel, and the metal sidewall on the narrow side of the quadrangular pyramid is an isosceles triangle; The height of the pyramid-shaped dielectric protrusion structure and the triangular metal side wall is the same and is half the wavelength of the center frequency; The waveguide outer wall and the inner circular coaxial line conductor, the square coaxial line inner conductor, the ridge adapter section, and the fourth-order Chebyshev converter are made of metal structures, and the dielectric filling block and the pyramid-shaped dielectric protrusion structure in the waveguide are made of polytetrafluoroethylene material with a dielectric constant of 2.

2.

2. The wide bandwidth and angle scanning open waveguide phased array antenna according to claim 1, characterized in that: The feeding network comprises three parts: a coaxial input section, a mode conversion section and an impedance transformation section; the coaxial input section is realized by a standard SMP coaxial connector; the mode conversion section comprises a circular coaxial line inner conductor, a square coaxial line inner conductor and a ridge adapter section, which is used to realize the transformation of the TEM mode in the circular coaxial line to the TEM mode in the square coaxial line, and further realizes the transformation to the TE mode through the ridge adapter section. 10 The impedance matching section is realized by a fourth-order Chebyshev impedance transformer.

3. The wide bandwidth and angle scanning open waveguide phased array antenna according to claim 2, characterized in that: The dielectric filling structure and the pyramid-shaped dielectric protrusion structure in the rectangular waveguide are made into an integrated dielectric filling block, which is filled inside the waveguide by means of physical limitation; the square coaxial line and the ridge adapter section are both air.

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