CN114465019A - Cassegrain antenna with transmitting and receiving coaxial functions for terahertz real aperture imaging - Google Patents

Cassegrain antenna with transmitting and receiving coaxial functions for terahertz real aperture imaging Download PDF

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Publication number
CN114465019A
CN114465019A CN202210016939.1A CN202210016939A CN114465019A CN 114465019 A CN114465019 A CN 114465019A CN 202210016939 A CN202210016939 A CN 202210016939A CN 114465019 A CN114465019 A CN 114465019A
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reflecting surface
feed source
main
receiving
main reflecting
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朱凯强
王翊坤
王一帆
张毅
赵国强
孙厚军
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Beijing Institute of Technology BIT
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Beijing Institute of Technology BIT
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q19/00—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic
    • H01Q19/10—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces
    • H01Q19/18—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces having two or more spaced reflecting surfaces
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/50—Structural association of antennas with earthing switches, lead-in devices or lightning protectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/52—Means for reducing coupling between antennas; Means for reducing coupling between an antenna and another structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
    • H01Q15/14—Reflecting surfaces; Equivalent structures
    • H01Q15/16—Reflecting surfaces; Equivalent structures curved in two dimensions, e.g. paraboloidal

Abstract

The invention discloses a transmitting-receiving coaxial Cassegrain antenna for terahertz real aperture imaging, which comprises a main reflecting surface, an auxiliary reflecting surface, a transmitting feed source and a receiving array element feed source array, wherein the main reflecting surface is provided with a plurality of reflecting surfaces; the main reflecting surface is provided with a first opening through which a symmetrical axis passes, the main reflecting surface and the auxiliary reflecting surface are coaxial, the focus of the main reflecting surface is superposed with one focus of the auxiliary reflecting surface, the receiving array element feed source array is positioned on the other side of the main reflecting surface, and a first distance is reserved between the receiving array element feed source array and the first opening. The Cassegrain antenna has the performance of receiving and transmitting, namely, the same antenna can realize both signal transmission and signal reception, has compact structure and easy miniaturization manufacture, can solve the problems of gain reduction and wave beam widening generated when the feed source is in a deflection focus due to the negative feed source forward extension, can obtain high gain and narrow main lobe width, and is beneficial to realizing tasks such as high-precision real-aperture imaging. The terahertz wave imaging device is widely applied to the technical field of antennas and active terahertz wave imaging.

Description

Cassegrain antenna with transmitting and receiving coaxial functions for terahertz real aperture imaging
Technical Field
The invention relates to the technical field of antennas, in particular to a Cassegrain antenna with coaxial transmitting and receiving for terahertz real aperture imaging.
Background
The cassegrain antenna is also called card antenna, is a double-reflector antenna, and can be equivalent to a parabolic antenna with long focal length, and at the same time, the feedforward mode of the parabolic antenna is changed into the feedback mode, and the space attenuation of the cassegrain antenna transmission signal is less than that of the parabolic antenna, so that it can achieve higher efficiency than the parabolic antenna. The Cassegrain antenna has a compact structure and is convenient to manufacture. The Cassegrain antenna can be applied to the fields of microwave and terahertz wave (electromagnetic waves with the frequency within the range of 0.1-10THz and the wavelength between 0.03-3 mm) communication, imaging, detection and the like.
Terahertz waves have the characteristics of short wavelength, narrow beam and good penetrability, and can easily complete tasks such as high-resolution imaging, micro target detection, target detection in a complex environment and the like, and the antenna is required to have higher gain. When the existing Cassegrain antenna is applied to a single detector feed source, a satisfactory effect can be easily obtained, but when the existing Cassegrain antenna is applied to processes such as real aperture imaging and the like, a receiving array element feed source array formed by multiple detectors is often needed, for the existing Cassegrain antenna, high gain, compact size and narrow main lobe are almost contradictory, for example, when high gain is pursued, only a narrower main lobe is often obtained, and the receiving array element feed source array formed by the multiple detectors is difficult to cover.
Disclosure of Invention
In view of at least one of the above technical problems, the present invention provides a cassegrain antenna for terahertz real aperture imaging with coaxial transceiving, including:
a main reflective surface; the surface shape of the main reflecting surface is a paraboloid of revolution; a first opening is formed at the passing position of the symmetry axis of the main reflecting surface;
a sub-reflecting surface; the surface shape of one side of the auxiliary reflecting surface, which faces the main reflecting surface, is a hyperboloid of revolution, and the surface shape of the other side of the auxiliary reflecting surface is a paraboloid of revolution;
the main reflecting surface and the auxiliary reflecting surface are coaxial, the auxiliary reflecting surface is positioned on one side of the focus of the main reflecting surface, and the focus of the main reflecting surface is superposed with one focus of the auxiliary reflecting surface;
transmitting a feed source; the transmitting feed source is positioned at the focus of the paraboloid of revolution of the auxiliary reflecting surface;
receiving an array element feed source array; the receiving array element feed source array is located on the other side of the main reflecting surface, a first distance is reserved between the receiving array element feed source array and the first opening, and the receiving array element feed source array can receive signals reflected by the auxiliary reflecting surface through the first opening.
Further, the cassegrain antenna further includes:
a support structure; the supporting structure is used for connecting the main reflecting surface and the auxiliary reflecting surface, so that the relative position between the main reflecting surface and the auxiliary reflecting surface is fixed.
Furthermore, the supporting structure is provided with a plurality of supporting rods, one ends of the supporting rods are connected with the edge of the main reflecting surface, and the other ends of the supporting rods are connected with the edge of the auxiliary reflecting surface.
Further, the magnification of the sub-reflecting surface is 1-10.
Further, the surface shape of the sub-reflecting surface corresponds to a curved surface equation of
Figure BDA0003460098360000021
Further, the cassegrain antenna further includes:
adjusting the structure; the adjusting structure is used for connecting the main reflecting surface and the receiving array element feed source array, so that a first distance is kept between the receiving array element feed source array and the first opening.
Further, the adjusting structure is a gasket; the thickness of the gasket is the first distance; the cushion may be inflated and deflated, and when inflated, the thickness of the cushion increases, and when deflated, the thickness of the cushion decreases.
Furthermore, the adjusting structure is a telescopic rod, and the length of the telescopic rod is the first distance; the length of the telescopic rod is adjustable.
The invention has the beneficial effects that: the Cassegrain antenna in the embodiment has the performance of receiving and transmitting, namely, the same antenna can realize both signal transmission and signal reception, and has compact structure and easy miniaturization and manufacture; the Cassegrain antenna in the embodiment has negative feed source forward extension, and can solve the problems of gain reduction and wave beam widening generated when the feed source is in a deflection focus, so that satisfactory high gain and narrow main lobe width can be obtained when a receiving array element feed source array is applied, and the tasks of high-precision real-aperture imaging and the like are favorably realized; meanwhile, the other side of the auxiliary reflecting surface is used as a transmitting antenna, and the transmitting and receiving antennas have the same rotational symmetry axis, so that the design difficulty of a later imaging algorithm is reduced.
Drawings
FIG. 1 is a block diagram of a Cassegrain antenna in an embodiment;
FIG. 2 is a structural view of a main reflecting surface and a sub reflecting surface in the embodiment;
FIG. 3 is a directional diagram of a single terahertz detector feed source in the embodiment;
FIG. 4 is a schematic diagram of the relative positions of the receiving array element feed source array, the main reflecting surface and the auxiliary reflecting surface in the embodiment;
FIG. 5 is a block diagram of a Cassegrain antenna according to an embodiment;
FIG. 6 is an antenna pattern obtained by performing simulated scanning on the amplification factor of the sub-reflector under the feed offset condition in the embodiment;
fig. 7 and 8 are antenna patterns obtained by simulating a cassegrain antenna by using a bouncing ray method in an embodiment.
Detailed Description
In this embodiment, the cassegrain antenna has a structure as shown in fig. 1, and includes a main reflecting surface, an auxiliary reflecting surface, a transmitting feed source, a receiving array element feed source array, and a supporting structure, where the supporting structure includes a plurality of supporting rods, one end of each supporting rod is connected to an edge of the main reflecting surface, and the other end is connected to an edge of the auxiliary reflecting surface, so that the relative position between the main reflecting surface and the auxiliary reflecting surface is fixed.
The transmitting feed source is positioned on one side of the secondary reflecting surface, which is opposite to the main reflecting surface, namely on one side of the paraboloid of revolution of the secondary reflecting surface, and specifically, the transmitting feed source is positioned at the focus of the paraboloid of revolution of the secondary reflecting surface. Referring to fig. 1, a transmitting waveguide flange may be installed on the main reflective surface, and the transmitting waveguide flange and the transmitting feed source are connected through a transmitting waveguide. The transmitting waveguide flange, the transmitting waveguide, the transmitting feed source and one side of the revolution paraboloid of the subreflector form a signal transmitting structure in the antenna.
The receiving array element feed source array, the main reflecting surface and one side of the rotating hyperboloid surface of the auxiliary reflecting surface form a signal receiving structure in the antenna.
By arranging the signal transmitting structure and the signal receiving structure, the integrated Cassegrain antenna for transmitting and receiving is realized, and the integrated Cassegrain antenna is compact in structure and easy to manufacture in a miniaturized mode.
Referring to fig. 2, the surface shape of the main reflecting surface is a paraboloid of revolution, the surface shape of one side of the sub reflecting surface facing the main reflecting surface is a hyperboloid of revolution, the surface shape of the other side of the sub reflecting surface is a paraboloid of revolution, the main reflecting surface and the sub reflecting surface are coaxial, that is, the rotating shaft of the main reflecting surface and the rotating shaft of the sub reflecting surface are in the same straight line, the sub reflecting surface is located on one side where the focus of the main reflecting surface is located, and the focus of the main reflecting surface coincides with one focus of the sub reflecting surface.
The main reflecting surface and the auxiliary reflecting surface are respectively formed by rotating a parabola and a hyperboloid around an axis F1F2, the parabola and the hyperboloid have a common focus F1, and the feed source is positioned at the other focus F2 of the hyperboloid. According to the properties of the hyperboloid and the paraboloid, rays emitted from the feed source F2 are reflected by the hyperboloid and the paraboloid, and reach the caliber of the paraboloid in the same phase, and the reflected rays are parallel to the axis to form plane waves.
When the design and analysis of the Cassegrain antenna are carried out, the double reflecting surfaces are equivalent to a single paraboloid with a real focus F2 as a focus, and the equivalent focal length F of the paraboloid is focused by the main reflecting surface of the original Cassegrain antennaDistance fmAnd the sub-reflecting surface magnification M:
f＝Mfm
the geometric design parameters of the main reflection paraboloid are as follows: major surface caliber dmFocal length of principal plane fmAnd half opening angle theta of main surfacem1Determining two parameters to determine the geometric dimension of the main reflecting surface, wherein the relationship between the geometric parameters of the main surface is as follows:
Figure BDA0003460098360000031
firstly, the caliber d of the main reflecting surface can be determined according to actual requirementsmFocal length to focal length ratio f of main reflecting surfacem/dmGeneral principal surface focal length ratio fm/dmThe value is 0.3-0.5, and the main surface focal distance f can be obtained according to a formulamAnd half opening angle theta of main surfacem1。
The geometric design parameter of the secondary reflection hyperboloid is the caliber d of the secondary reflection surfacesFocal length f of subreflectorsMagnification M and half opening angle thetam2And the geometrical size of the secondary surface can be uniquely determined by arbitrarily determining two parameters, and the relation between the geometrical parameters of the secondary reflecting surface is as follows:
Figure BDA0003460098360000041
Figure BDA0003460098360000042
the geometric design parameter of the secondary reflection hyperboloid is the caliber d of the secondary reflection surfacesFocal length f of subreflectorsMagnification M and half opening angle thetam2The geometric dimension of the secondary surface can be uniquely determined by arbitrarily determining two parameters.
Considering the diffraction effect of the sub-reflector, the noise temperature of the antenna and the aperture shielding effect, the aperture d of the sub-reflector is generally setsAt (0.1-0.2) dmI.e. 20mm to 40 mm. The vertex of the sub-reflecting surfaceToo large a curvature of (2) causes a large cross polarization component, and the secondary reflection surface magnification M is usually set to 3.5 to 15. Determining the aperture d of the subreflector according to actual requirementssAfter the magnification ratio M is added, the focal length f of the sub-reflecting surface can be calculated by the formulasAnd half opening angle thetam2。
The larger the aperture of the main surface, the higher the gain of the antenna, and the smaller the beam width. According to the embodiment, the aperture of the terahertz antenna is 200 mm. When the main surface caliber is 200mm, the antenna gain G and the main lobe 3dB beam width HPBW are as follows:
Figure BDA0003460098360000043
Figure BDA0003460098360000044
wherein e isAFor antenna aperture utilization efficiency, generally eAIf the value is 0.5-0.75, the antenna gain G is 54-55.8 dBi; k0.5The value is 65-70 degrees, and the main lobe 3dB wave beam width HPBW is 0.28-0.31 degrees.
The focal length of the main surface is determined by the focal length ratio f of the main reflecting surfacem/dmDetermining that the focal diameter ratio of the antenna is small, the axial size of the antenna is small, and the feed source blocks the subreflector little; the focal ratio is large, the depth of the paraboloid is small, the cross polarization component is small, and the working performance of the feed source in the deflection of focus is improved. Using empirical values fm/dm0.4, i.e. fm80mm, half opening angle theta of main surfacem1＝2arctan(dm/4fm)＝64°。
The design of parameters of the secondary reflecting surface needs to consider the aperture shielding effect of the secondary surface. In order to make the sub-reflector of the cassegrain antenna receive as much electromagnetic radiation as possible and have as small aperture shielding as possible, the opening angle 2 theta of the sub-reflector is generally setm2Equal to-10 dB beamwidth of the feed. The pattern (normalized response curve) according to the current single terahertz detector feed is shown in fig. 3.
In this embodiment, the array of receiving array elements feed source mayIs a 16 × 16 or N × N detector receiving array element feed source array, i.e. 256 or N2The detector feed sources are uniformly arranged on a plane in a 16 multiplied by 16 or N multiplied by N mode, and the detector receiving array element feed source array is vertical to the rotating shafts of the main reflecting surface and the auxiliary reflecting surface. By using the receiving array element feed source array, functions such as high-precision aperture imaging and focal plane imaging can be realized. The detector feed source is a waveguide feed source manufactured by adopting a diffusion welding process.
As can be seen from fig. 2, the-10 dB beamwidth of the detector unit is 18 °. If the feed source of the Cassegrain antenna is a single detector feed source, the opening angle of the secondary surface is made to be 2 theta according to the design principlem218 ° is set. However, when a 16 x 16 or other size detector is used to receive the array of array element feeds, detector feeds that are further from the axis of rotation of the primary and secondary reflectors will be out of focus.
Referring to fig. 4, when the feed source is not on the axis of the reflecting surface (the feed source is in a horizontal focus), the edge irradiation level of the feed source entering the sub-reflecting surface is changed compared with the positive feed condition, and the opening angle 2 theta of the sub-reflecting surface is required to be adjustedm2>And 18 degrees, when the feed source is in a transverse focusing state, the auxiliary reflecting surface can receive and reflect most of the radiation electromagnetic waves of the focusing feed source. However, when the opening angle of the sub-reflecting surface is increased, the size of the sub-reflecting surface is increased, the shielding of the sub-reflecting surface is increased, the gain of the antenna is reduced, and the main lobe is widened.
In order to deal with the situations of antenna gain reduction and main lobe broadening, in this embodiment, referring to fig. 5, a slide is used to bear the receiving array element feed source array, referring to fig. 5 and fig. 4, a spacer is used to be padded between the receiving array element feed source array and the main reflecting surface, the slide is overlapped with the spacer, when the thickness of the spacer is a first distance, a first distance is kept between the receiving array element feed source array and a first opening of the main reflecting surface, a second opening is arranged on the spacer, and the receiving array element feed source array can transmit signals to the auxiliary reflecting surface through the first opening and the second opening. In some technologies, the distance between the feed source and the center of the main reflecting surface is called feed source protrusion, and in the prior art, the feed source is positioned on one side of the focus of the main reflecting surface in a rotating paraboloid shape, and positive numbers are used for expressing the feed source protrusion. In this embodiment, the feed source is located on the other side of the side where the focus of the main reflecting surface is located, and accordingly, the feed source forward extension amount in this embodiment is a negative number. By using the negative feed forward extension, the Cassegrain antenna can still obtain high antenna gain and narrow main lobe when a receiving array element feed array is used.
In this embodiment, an adjusting structure may be disposed between the main reflection surface of the cassegrain antenna and the receiving array element feed array, so that the main reflection surface and the receiving array element feed array are connected together by the adjusting structure, and the receiving array element feed array and the first opening are separated by a first distance.
In this embodiment, a gasket made of rubber or the like may be used as the adjustment structure, and the gasket may be processed to have a structure capable of being inflated and deflated. The thickness of the spacer is a first distance, so that when the spacer is arranged between the main reflecting surface and the receiving array element feed source array, the first distance is kept between the receiving array element feed source array and the first opening. When the cushion is inflated, the thickness of the cushion is increased, and when the cushion is deflated, the thickness of the cushion is decreased. The size of the first distance can be changed by inflating and deflating the gasket, so that the antenna gain and the width of the main lobe can be adjusted, and a proper value can be easily obtained in the field installation or the later maintenance.
The telescopic rod can also be used as an adjusting structure. The length of telescopic link is first distance, is connected with the main reflecting surface when telescopic link one end, and the other end is connected with receiving array element feed array, can make between receiving array element feed array and the first opening apart from first distance. The length of telescopic link is adjustable, and when the telescopic link extension, first distance increase shortens when the telescopic link, and first distance reduces. The first distance can be changed by stretching the telescopic rod, so that the antenna gain and the width of the main lobe can be adjusted, and a proper value can be easily obtained in the field installation or the later maintenance and other occasions.
When the feed is off focus, the antenna gain decreases. In order to ensure that the antenna gain is ensured when the feed source offset is maximum and simultaneously the feed source forward extension amount meets the project requirement, the size of the subreflector is calculated and optimized, the magnification M of the subreflector is swept in the design, M is respectively 4, 5, 6, 7 and 8, under the condition of feed source offset feed, the directional diagram of the antenna is simulated and calculated, and the directional diagram of the antenna is respectively obtained as shown in figure 6.
Referring to fig. 6, a solid line indicates an offset pattern when M is 6, and in this case, the offset pattern belongs to an optimal solution among M4, 5, 6, 7, and 8, that is, when the amplification factor of the sub-reflecting surface is 6, a high gain and a narrow beam can be obtained. According to the analysis result shown in FIG. 6, a set of sub-reflecting surface size parameters is obtained, and the surface equation corresponding to the surface shape of the sub-reflecting surface is
Figure BDA0003460098360000061
Wherein x is the element (-d)s/2,ds/2) in the present embodiment, the aperture d of the sub-reflecting surfaces38mm, the magnification M of the secondary reflecting surface is 6, the eccentricity e is 1.4, and the half-opening angle thetam2A feed reach of-12.35 mm, i.e. a first distance of 12.35mm, 12.7 °, enables higher gain and narrower beams to be obtained.
A simulation experiment was performed on the cassegrain antenna in this example. Because the working frequency of the antenna is high (340GHz), the wavelength is only 0.88mm, the electrical length of the main surface of the antenna reaches 227 lambda, wherein lambda is the working wavelength of the antenna, the traditional full-wave simulation algorithm needs large computing hardware resources and long computing time, and the optimal design of the antenna is difficult to carry out. The card antenna can be simulated by adopting a CST built-in improved physical optical method (PO) -bounce ray method (SBR). The card antenna directional pattern obtained by simulation is shown in fig. 7, and the simulation result is as follows: the gain of the antenna is 56dBi, the 3dB main lobe beam width is 0.26 degrees, and the simulation is consistent with the theoretical calculation result, namely, higher antenna gain and narrower main lobe beams are obtained.
In implementation, a receiving array element feed array of the card antenna is a 16 × 16 mixing detector array, the unit spacing in the receiving array element feed array, that is, the distance between adjacent detector feeds, is 2mm, and then the lateral offset δ of the feeds is (-15mm) - (15 mm). Since the card antenna has a rotationally symmetric structure and the feed offset δ (-15mm) - (-1mm) is symmetric to the pattern δ (1mm) - (15mm), only the off-focus characteristic of the antenna at the offset δ (1mm) - (15mm) is given below. By using the CST SBR method, the offset focus model of the card antenna feed source is simulated, and an antenna directional pattern obtained by simulation is shown in figure 8.
According to theoretical calculation and simulation results of the influence of the feed source offset on the beam pointing direction, the feed source is deflected by 1mm in each transverse direction, and the beam pointing deflection is about 0.12 degrees. However, the feed source is off-focus, which causes the gain of the antenna to be reduced, and the 3dB main lobe width is widened, but simulation verification proves that: when the feed source offset is maximum (delta is 15mm), the antenna gain is 54dBi, namely for the feed source which is far away from the rotating shaft of the main reflecting surface and the auxiliary reflecting surface in the receiving array element feed source array, even if the feed source is in a deflected focus, the higher antenna gain can be obtained, and the problem of large reduction of the antenna gain caused by the deflected focus of the feed source in the prior art is solved.
In summary, the cassegrain antenna in this embodiment has the following features: the transceiver is coaxial, so that the occupied space can be effectively reduced; the effect of high gain and narrow beam can be achieved at least under the high frequency of 340GHz, and the terahertz wave tunable filter can be applied to the environment of terahertz waves; through the negative feed source forward extension, the problems of gain reduction and wave beam widening generated when the feed source is in a deflection focus can be solved, so that satisfactory high gain and narrow main lobe width can be obtained when the receiving array element feed source array is applied, and the high-precision aperture imaging task and the like can be realized.
It should be noted that, unless otherwise specified, when a feature is referred to as being "fixed" or "connected" to another feature, it may be directly fixed or connected to the other feature or indirectly fixed or connected to the other feature. Furthermore, the descriptions of upper, lower, left, right, etc. used in the present disclosure are only relative to the mutual positional relationship of the constituent parts of the present disclosure in the drawings. As used in this disclosure, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. In addition, unless defined otherwise, all technical and scientific terms used in this example have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in the description of the embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this embodiment, the term "and/or" includes any combination of one or more of the associated listed items.
It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element of the same type from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present disclosure. The use of any and all examples, or exemplary language ("e.g.," such as "or the like") provided with this embodiment is intended merely to better illuminate embodiments of the invention and does not pose a limitation on the scope of the invention unless otherwise claimed.
The above description is only a preferred embodiment of the present invention, and the present invention is not limited to the above embodiment, and any modifications, equivalent substitutions, improvements, etc. within the spirit and principle of the present invention should be included in the protection scope of the present invention as long as the technical effects of the present invention are achieved by the same means. The invention is capable of other modifications and variations in its technical solution and/or its implementation, within the scope of protection of the invention.

Claims (8)

1. A transmitting and receiving coaxial Cassegrain antenna for terahertz real aperture imaging is characterized by comprising:
a main reflective surface; the surface shape of the main reflecting surface is a paraboloid of revolution; a first opening is formed at the passing position of the symmetry axis of the main reflecting surface;
a sub-reflecting surface; the surface shape of one side of the auxiliary reflecting surface, which faces the main reflecting surface, is a hyperboloid of revolution, and the surface shape of the other side of the auxiliary reflecting surface is a paraboloid of revolution;
the main reflecting surface and the auxiliary reflecting surface are coaxial, the auxiliary reflecting surface is positioned on one side of the focus of the main reflecting surface, and the focus of the main reflecting surface is superposed with one focus of the auxiliary reflecting surface;
transmitting a feed source; the transmitting feed source is positioned at the focus of the paraboloid of revolution of the auxiliary reflecting surface;
receiving an array element feed source array; the receiving array element feed source array is located on the other side of the main reflecting surface, a first distance is reserved between the receiving array element feed source array and the first opening, and the receiving array element feed source array can receive signals reflected by the auxiliary reflecting surface through the first opening.
2. A cassegrain antenna according to claim 1, characterised in that it further comprises:
a support structure; the supporting structure is used for connecting the main reflecting surface and the auxiliary reflecting surface, so that the relative position between the main reflecting surface and the auxiliary reflecting surface is fixed.
3. The cassegrain antenna of claim 2 wherein the support structure is a plurality of struts, one end of the struts connecting to the edge of the primary reflector and the other end of the struts connecting to the edge of the secondary reflector.
4. A cassegrain antenna according to claim 1, characterised in that the magnification of the sub-reflecting surface is 1-10.
5. The Cassegrain antenna of claim 4, wherein the sub-reflector has a surface shape corresponding to a surface equation of
Figure FDA0003460098350000011
6. A cassegrain antenna according to claim 1, characterized in that it further comprises:
adjusting the structure; the adjusting structure is used for connecting the main reflecting surface and the receiving array element feed source array, so that a first distance is kept between the receiving array element feed source array and the first opening.
7. The cassegrain antenna of claim 6, wherein the adjustment structure is a spacer; the thickness of the gasket is the first distance; the cushion may be inflated and deflated, and when inflated, the thickness of the cushion increases, and when deflated, the thickness of the cushion decreases.
8. The cassegrain antenna of claim 6, wherein the adjustment structure is a telescoping rod having a length that is the first distance; the length of the telescopic rod is adjustable.
CN202210016939.1A 2022-01-07 2022-01-07 Cassegrain antenna with transmitting and receiving coaxial functions for terahertz real aperture imaging Pending CN114465019A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115313063A (en) * 2022-05-30 2022-11-08 南京星航通信技术有限公司 Reflective surface antenna

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115313063A (en) * 2022-05-30 2022-11-08 南京星航通信技术有限公司 Reflective surface antenna
CN115313063B (en) * 2022-05-30 2023-10-10 南京星航通信技术有限公司 Reflection type surface antenna

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