Ka / V band dual-frequency conical beam antenna for millimeter-wave detection

Abstract

This invention provides a Ka / V band dual-frequency conical beam antenna for millimeter-wave detection, comprising an upper square metal structure, a lower square metal structure, a coaxial waveguide, an open circular waveguide, and a feed network. The open circular waveguide is the main radiating part, transitioning from the coaxial waveguide to the open circular waveguide, allowing the open circular waveguide to operate in TM mode to generate a radially symmetrical electric field distribution. By adjusting the size of the open circular waveguide, TM01 and TM02 modes exist within it, respectively generating Ka / V band electromagnetic waves. This invention utilizes a shielded microstrip line to excite the fundamental TEM mode of the coaxial waveguide before transitioning to the TM mode of the circular waveguide, which can suppress other unwanted modes, thereby making the omnidirectional radiation of the antenna more uniform. The coaxial waveguide is a stepped coaxial waveguide with varying radius. The stepped structure of the waveguide inner diameter can achieve good impedance matching. The structure is simple, easy to implement, and has dual-frequency, dual-tilt radiation characteristics.

Description

Technical Field

[0001] This invention pertains to millimeter-wave detection technology, specifically relating to a dual-frequency conical beam antenna for short-range millimeter-wave detection. Background Technology

[0002] With the advancement of radio technology in the information age, modern fuze systems are rapidly developing towards smaller, lighter, thinner designs, higher reliability, higher performance, lower power consumption, and lower cost. Besides meeting the general electrical performance requirements of antennas, such as VSWR and gain, missile-borne fuze antennas also need to consider many special performance characteristics. For example, the main lobe of the missile-borne antenna's radiation pattern must have a certain tilt angle with the missile axis; this angle is related to the missile-target velocity and the missile-target rendezvous attitude.

[0003] Traditional microwave fuses, due to their size and weight, can no longer meet the needs of weapon system development. Compared to microwaves, millimeter-wave systems and components offer advantages such as smaller size, lighter weight, and higher resolution. Currently, 3mm band (W-band) and 8mm band (Ka-band) fuse antennas are relatively mature; however, these bands are within atmospheric windows, where atmospheric attenuation has a relatively small impact, resulting in weak security and anti-interference capabilities. In contrast, the 5mm band (V-band) is outside atmospheric windows, experiencing severe atmospheric attenuation, thus offering extremely strong security and anti-interference capabilities. The 5mm / 8mm (Ka / V-band) composite fuse antenna combines the characteristics of both bands and has promising applications in short-range millimeter-wave detection fields such as missile-borne antennas. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a dual-band conical beam omnidirectional antenna that realizes both Ka-band and V-band frequencies.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is a Ka / V band dual-frequency conical beam antenna for millimeter wave detection, comprising an upper square metal structure, a lower square metal structure, a coaxial waveguide, an open circular waveguide, and a feeding network.

[0006] An open circular waveguide is positioned centrally at the top of the upper half of the metal structure. A metal slot is formed at the bottom of the upper half of the metal structure, within which a shielded microstrip line serving as a feed network is placed. The shielded microstrip line forms a 1-to-4 power divider. A coaxial waveguide is positioned below the open circular waveguide, extending from the upper half of the metal structure to the top of the lower half of the square metal structure. In the lower half of the metal structure, the bottom of the coaxial waveguide is a short-circuit surface, and the inner conductor of the coaxial waveguide is positioned above the short-circuit surface, with the length of the inner conductor being equal to the axial length of the coaxial waveguide. The open circular waveguide is coaxial with the coaxial waveguide.

[0007] The coaxial waveguide transmits the TEM mode to avoid generating unwanted modes; the open circular waveguide is the main radiating part, transitioning to the open circular waveguide via the coaxial waveguide, so that the open circular waveguide operates in TM mode to generate a radially symmetrical electric field distribution. By adjusting the size of the open circular waveguide, the TM mode is present within it. 01 Model and TM 02 The modes are used to generate Ka / V band electromagnetic waves respectively.

[0008] This invention utilizes a shielded microstrip line to excite the fundamental TEM mode of a coaxial waveguide and then transition it to the TM mode of a circular waveguide, which can suppress other unwanted modes, thereby enabling more uniform omnidirectional radiation of the antenna.

[0009] Preferably, the coaxial waveguide is a stepped coaxial waveguide with varying radius, formed by connecting coaxial cylinders of different diameters in series. The structure with a stepped inner diameter of the waveguide can achieve impedance matching well.

[0010] By employing a shielded microstrip line feeding method, radiation loss of high-frequency electromagnetic waves is reduced. Furthermore, the rectangular patch forming probe can effectively excite the TEM mode of the coaxial waveguide and transition to the TM mode of the circular waveguide.

[0011] The advantages of this invention are: simple structure, easy to implement, and dual-frequency dual-tilt radiation characteristics. Attached Figure Description

[0012] Figure 1 This is an overall view of the dual-band omnidirectional antenna;

[0013] Figure 2 This is an exploded view of the upper and lower metal structures of a dual-band omnidirectional antenna;

[0014] Figure 3 This is a schematic diagram of the lower surface of the upper half of the metal structure of a dual-band omnidirectional antenna.

[0015] Figure 4 This is a schematic diagram of the upper surface of the lower half of the metal structure of a dual-frequency omnidirectional antenna.

[0016] Figure 5 This is a side view of a dual-band omnidirectional antenna;

[0017] Figure 6 This is a front view of a dual-band omnidirectional antenna;

[0018] Figure 7 Port S of the dual-band omnidirectional antenna in the embodiment 11 And the gain curve;

[0019] Figure 8 This is the radiation pattern of the dual-frequency omnidirectional antenna in the embodiment. Detailed Implementation

[0020] The Ka / V band dual-band omnidirectional antenna consists of three parts: a coaxial waveguide, an open circular waveguide, and a feed network. The coaxial waveguide transmits the TEM mode to avoid generating unwanted modes. The open circular waveguide is the main radiating element. The transition from the coaxial waveguide to the circular waveguide allows the circular waveguide to operate in TM mode, generating a radially symmetrical electric field distribution. By adjusting the dimensions of the circular waveguide, TM mode can be achieved within it. 01 Model and TM 02 The modes are divided to generate two different frequency bands. The coaxial waveguide is designed as a stepped type with varying radius to achieve better impedance matching. The feed network consists of a 1-to-4 power divider made of shielded microstrip lines.

[0021] like Figure 1 , 2 The Ka / V dual-band omnidirectional antenna shown in Figures 3 and 4 consists of a square metal structure divided into upper and lower parts and a printed circuit board (PCB) in the middle. An open circular waveguide 6 is centrally located at the top of the upper metal structure 1, and a metal groove 8 is opened at the bottom of the upper metal structure 1, in which a shielded microstrip line 3 is placed. The upper surface of the lower metal structure 5 is provided with a printed circuit board (PCB) as a dielectric substrate 4, and the shielded microstrip line 3 is placed on the dielectric substrate. A cylindrical coaxial waveguide inner conductor 2 is centrally located in the lower metal structure 5.

[0022] To more clearly illustrate the waveguide structure of the antenna, such as Figure 5 and 6 As shown, the waveguide structure includes an open circular waveguide 6 that opens from the upper surface of the upper metal structure 1, and a stepped coaxial waveguide 7 formed by connecting coaxial cylindrical structures of different diameters, located below the open circular waveguide 6 and extending through the upper metal structure 1 to the upper part of the upper metal structure 5. The bottom 9 of the coaxial waveguide in the lower metal structure 5 is a waveguide short-circuit surface. The inner conductor 2 of the coaxial waveguide is positioned above the waveguide short-circuit surface and its length is the axial length of the entire stepped coaxial waveguide 7. The centers of the open circular waveguide 6, the stepped coaxial waveguide 7, and the inner conductor 2 of the coaxial waveguide are coaxial.

[0023] A shielded microstrip line 3 is used as the feed structure, and the shield is constructed of a metal cavity. Four rectangular patches at the end of the microstrip power divider in the shielded microstrip line 3 extend into the coaxial waveguide, forming a perimeter around which the dominant TEM mode in the coaxial waveguide is excited by four probes. The antenna structure consists of a circular waveguide open at one end and a coaxial waveguide connected to it. The end of the coaxial waveguide is blocked by a metal body, forming a short-circuit surface. Electromagnetic waves are reflected here and form in-phase superposition at the probe locations, propagating along the path in the direction of the opening, and then entering the circular waveguide in their higher-order TM mode. 01 and TM 02As the mode propagates forward, the similarity in field distribution between the fundamental TEM mode in the coaxial waveguide and the TM mode in the circular waveguide makes the conversion between them easy.

[0024] In this embodiment, the dielectric substrate 4 is made of Rogers 5880 material with a dielectric constant of 2.2 and a thickness of 0.127 mm. The distance between the plane containing the shielded microstrip line 3 and the short-circuit surface 9 of the coaxial waveguide is 1.72 mm, the axial length of the open circular waveguide 6 is 3.25 mm, and the axial length of the stepped coaxial waveguide 7 is 5.47 mm.

[0025] When the antenna is excited, energy is coupled from the shielded microstrip line 3 through the probe to the stepped coaxial waveguide 7 with a short-circuit surface 9 at one end. First, the dominant TEM mode is excited in the coaxial waveguide. The distance between the rectangular microstrip probe 3 and the short-circuit surface 9 of the coaxial waveguide is one-quarter of the wavelength, causing the reflected electromagnetic wave to superimpose with another electromagnetic wave propagating towards the open circular waveguide 6. The electromagnetic wave transitions from the coaxial waveguide 7 to the open circular waveguide 6, exciting the TM mode of the open circular waveguide 6, exhibiting a radially symmetrical electric field distribution. Finally, it radiates into free space, forming an omnidirectional radiation pattern with a certain tilt angle in the elevation plane, as shown below. Figure 8 As shown.

[0026] Figure 7 The S11 curves of this Ka / V band dual-band omnidirectional antenna are described, showing good reflection coefficients. The impedance bandwidth with dB(S(1,1)) below -10 in the Ka band is 29.61 GHz to 38.83 GHz, and the impedance bandwidth with dB(S(1,1)) below -10 in the V band is 58.13 GHz to 64.87 GHz. In the Ka band, the gain is greater than 7.5 dBi, with a maximum gain of 9.55 dBi; in the V band, the antenna gain is greater than 6.5 dBi, with a maximum gain of 8.69 dBi.

[0027] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A Ka / V band dual-frequency conical antenna, characterized in that, It includes a square metal structure in the upper part, a square metal structure in the lower part, a coaxial waveguide, an open circular waveguide, and a feed network. An open circular waveguide is positioned at the center of the upper part of the upper metal structure; a metal groove is opened at the lower part of the upper metal structure, and a shielded microstrip line serving as a feed network is placed inside the metal groove. The shielded microstrip line forms a 1-to-4 power divider; the coaxial waveguide is placed below the open circular waveguide, extending from the upper square metal structure to the upper part of the lower square metal structure, and is a stepped structure formed by connecting coaxial cylindrical structures of different diameters; in the lower square metal structure, the bottom of the coaxial waveguide is the waveguide short-circuit surface, and the inner conductor of the coaxial waveguide is placed above the waveguide short-circuit surface, with the length of the inner conductor being the axial length of the coaxial waveguide; the open circular waveguide is coaxial with the coaxial waveguide; The coaxial waveguide transmits the TEM mode to avoid generating unwanted modes; the open circular waveguide is the main radiating part, transitioning to the open circular waveguide via the coaxial waveguide, so that the open circular waveguide operates in TM mode to generate a radially symmetrical electric field distribution. By adjusting the size of the open circular waveguide, the TM mode is present within it. 01 Model and TM 02 The modes are used to generate Ka / V band electromagnetic waves respectively.

2. The antenna as described in claim 1, characterized in that, A coaxial waveguide is a stepped coaxial waveguide with varying radius formed by connecting coaxial cylindrical tubes of different diameters in series.

3. The antenna as described in claim 1, characterized in that, The upper surface of the lower half of the square metal structure is provided with a PCB dielectric substrate, and the shielded microstrip line is placed on the dielectric substrate within the metal groove of the upper half of the square metal structure.

4. The antenna as described in claim 1, characterized in that, The shielded microstrip line contains a rectangular microstrip probe; when the antenna is excited, energy is coupled from the shielded microstrip line through its rectangular microstrip probe to a coaxial waveguide with a short-circuit surface at one end.

5. The antenna as described in claim 1, characterized in that, The distance between the plane containing the shielded microstrip line and the short-circuit surface of the waveguide is one-quarter of the wavelength.

6. The antenna as described in claim 5, characterized in that, The dielectric substrate is made of Rogers 5880 with a dielectric constant of 2.2 and a thickness of 0.127 mm. The distance between the plane containing the shielded microstrip line and the short-circuit surface of the waveguide is 1.72 mm. The axial length of the open circular waveguide is 3.25 mm, and the axial length of the stepped coaxial waveguide is 5.47 mm.

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