CN113206387B - Wide-bandwidth terahertz frequency band quasi-optical sum-difference comparator - Google Patents
Wide-bandwidth terahertz frequency band quasi-optical sum-difference comparator Download PDFInfo
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- CN113206387B CN113206387B CN202110434865.9A CN202110434865A CN113206387B CN 113206387 B CN113206387 B CN 113206387B CN 202110434865 A CN202110434865 A CN 202110434865A CN 113206387 B CN113206387 B CN 113206387B
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- 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
- H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B17/00—Systems with reflecting surfaces, with or without refracting elements
- G02B17/02—Catoptric systems, e.g. image erecting and reversing system
- G02B17/06—Catoptric systems, e.g. image erecting and reversing system using mirrors only, i.e. having only one curved mirror
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/10—Beam splitting or combining systems
- G02B27/106—Beam splitting or combining systems for splitting or combining a plurality of identical beams or images, e.g. image replication
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/10—Beam splitting or combining systems
- G02B27/1086—Beam splitting or combining systems operating by diffraction only
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- 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
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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
- H01Q19/185—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 wherein the surfaces are plane
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Abstract
The invention discloses a terahertz quasi-optical sum-difference comparator with wide bandwidth, and belongs to the technical field of quasi-optical single pulse antennas. The sum-difference comparator comprises a sum input port, a difference input port, a grating beam splitter, 4 reflecting mirrors and two output ports. The scheme of the invention can solve the problem of narrow bandwidth of the existing quasi-optical sum-difference comparator due to large path difference, and because the reflection path difference and the transmission path difference are only lambda/4, the beam spots of the two output ports are almost as large, thereby effectively improving the sum-difference radiation characteristic of the sum-difference comparator.
Description
Technical Field
The invention belongs to the technical field of quasi-optical monopulse antennas, and particularly relates to a terahertz frequency band quasi-optical sum-difference comparator with low loss and wide bandwidth characteristics.
Background
With the rapid development of radar technology, the accuracy requirements for detection, positioning and tracking of targets are increasing. As a compact angle measurement technology, the monopulse technology can determine the position information of the target by only analyzing one echo pulse theoretically, and the speed of extracting the position information of the target is greatly increased. The core of the monopulse antenna is the sum-difference comparator. With the continuous improvement of frequency, the traditional structures such as waveguide and microstrip line face the defects of large loss, small bearing power, difficult processing and the like, and the quasi-optical technology utilizes the characteristic of low space bunching propagation loss of electromagnetic waves, thereby providing an effective solution for the research of a sum-difference comparator. Quasi-optical elements (lenses, reflectors and the like) designed by using a quasi-optical technology can better control the transmission of Gaussian beams, and can solve the problems of large loss, insufficient power capacity and difficult processing in the transmission of the traditional structure. In addition, although the quasi-optical and differential comparator structure proposed by Rolf Jakoby has the advantages of simple structure and low loss, the structure still has the disadvantages of narrow bandwidth and poor radiation characteristics, so that a better design scheme is urgently required to be sought.
Disclosure of Invention
The invention aims to provide a terahertz quasi-optical sum-difference comparator with wide bandwidth, which has the advantages of small loss, large bearing power and easiness in processing, solves the problem of narrow bandwidth of the terahertz quasi-optical sum-difference comparator, and effectively improves the sum-difference radiation characteristic of the sum-difference comparator.
In order to realize the purpose, the technical scheme adopted by the invention is as follows:
a wide bandwidth terahertz frequency band quasi-optical sum-difference comparator comprising: the optical fiber grating light source comprises a sum input port, a difference input port, a reflector M1, a reflector M2, a reflector M3, a reflector M4, a grating beam splitter, a first output port and a second output port. After the Gaussian beam vertically enters the input port, the sum effect of the sum and difference comparator is realized by two paths of beams output by the first output port and the second output port; after the Gaussian beam vertically enters the difference input port, the difference effect of the sum and difference comparator is realized by two paths of beams output by the first output port and the second output port.
The reflecting mirror M1, the reflecting mirror M2, the reflecting mirror M3, and the reflecting mirror M4 are plane reflecting mirrors, and are used for controlling the transmission direction of the beam.
The grating beam splitter is a transmission type metal grating beam splitter and is used for equally dividing power of incident beams and generating a 90-degree phase difference, namely the amplitudes of transmission beams and reflection beams are equal, and the phase of the transmission beams = the phase of the reflection beams +90 degrees.
After the Gaussian beam is input and input into the input port, the Gaussian beam is reflected by the reflector M1 and then reaches the grating beam splitter, part of the Gaussian beam reflected by the grating beam splitter is a beam A1, and part of the Gaussian beam transmitted by the grating beam splitter is a beam A2; the beam A1 is output from a first output port after being reflected twice by a reflector M4 and a reflector M3 in sequence; the beam A2 is reflected by the mirror M2 and then output from the second output port.
After the Gaussian beam B is input into the difference input port, part of the transmitted beam passing through the grating beam splitter is a beam B1, and the reflected part of the beam is a beam B2; the beam B1 is output from a first output port after being reflected twice by a reflector M4 and a reflector M3 in sequence; the beam B2 is reflected by the mirror M2 and then output from the second output port.
Further, the reflection of the beam in the sum and difference comparator is both 90 degree reflection.
Furthermore, the reflector M1, the grating beam splitter and the reflector M2 are sequentially arranged in parallel and form an included angle of 45 degrees with the input port; the reflector M3 and the reflector M4 are placed in parallel, an included angle between the reflector M3 and the reflector M1 is 90 degrees, and an included angle between the reflector M4 and the grating beam splitter is 90 degrees.
Further, the distance between the reflecting mirror M1 and the grating beam splitter is h, and the distance between the reflecting mirror M2 and the grating beam splitter is h- λ/4, wherein λ is the working wavelength. The reduced lambda/4 path leads the phase of the beam through this path by 90 degrees.
Furthermore, the incident aperture of the sum input port is a square, the side length of the incident aperture is h, the incident aperture of the difference input port is also a square, the side length of the incident aperture is h-lambda/4, and h is greater than the radius R when the edge level of the double Gaussian beam is 30dB lower than the central level.
Furthermore, the grating radius of the grating beam splitter is 0.1mm, and the period is 0.245mm. The grating beam splitter is made of molybdenum wires plated with gold, and the purpose of the material is to reduce the loss of Gaussian beams when the beams pass through the beam splitter.
Further, the center frequency of the Gaussian beam is greater than 100GHz.
To achieve the sum and difference comparator effect, when the beam a enters from the sum input port and passes through the grating beam splitter, the beam is divided into a transmission beam A2 and a reflection beam A1, where the transmission beam A2 and the reflection beam A1 have the same amplitude, and the phase of the transmission beam A2 = the phase of the reflection beam A1 +90 °. Since the distance between the mirror M1 and the grating beam splitter is h, and the distance L between the mirror M2 and the grating beam splitter is L = h- λ/4, that is, the phase of the transmission beam A2 at the second output port will lead 90 °, the beam phases and amplitudes of the two output ports will be equal, and thus a sum beam is formed.
To achieve the poor effect of the sum and difference comparator, when the beam B is incident from the difference input port and passes through the grating beam splitter, the beam is divided into a transmitted beam B1 and a reflected beam B2, where the transmitted beam B1 and the reflected beam B2 have equal amplitude, and the transmitted beam B1 is phase = the reflected beam B2 is phase +90 °. Since the distance between the mirror M1 and the grating beam splitter is h, and the distance L between the mirror M2 and the grating beam splitter is L = h- λ/4, that is, the phase of the reflected beam B2 at the second output port will lead 90 °, the phases of the beams at the two output ports will differ by 180 ° and the amplitudes are equal, thereby forming a difference beam.
The scheme of the invention can solve the problem that the quasi-optical sum-difference comparator provided by Rolf Jakoby has a narrow bandwidth due to large distance difference. And because the reflection path difference and the transmission path difference are only lambda/4, the beam spots of the two output ports are almost as large, and the sum-difference radiation characteristic of the sum-difference comparator is effectively improved.
Drawings
Fig. 1 is a structural schematic diagram of a wide bandwidth terahertz quasi-optical sum-difference comparator.
Fig. 2 shows a far-field pattern of the sum beam obtained by feeding a gaussian beam to the input port a, the center frequency of which is 340GHz, and a comparison graph of 330GHz and 350GHz is shown.
Fig. 3 is a far-field pattern of the difference beam obtained by feeding a gaussian beam into the difference input port B, the center frequency is 340GHz, and a comparison graph of 330GHz and 350GHz is given.
The reference numbers illustrate: 1. mirrors M1,2, M2,3, M3,4, M4,5, grating beam splitter, 6, sum input port, 7, difference input port, 8, first output port, 9, second output port.
Detailed Description
The following describes embodiments of the present invention with reference to the drawings.
Fig. 1 is a schematic structural diagram of a terahertz quasi-optical and difference comparator of the present embodiment, as shown in fig. 1, the quasi-optical and difference comparator includes: the optical fiber grating light source comprises a sum input port, a difference input port, a reflector M1, a reflector M2, a reflector M3, a reflector M4, a grating beam splitter 5, a first output port and a second output port. Wherein, the reflector M1, the reflector M2, the reflector M3 and the reflector M4 are plane reflectors; the grating beam splitter is a transmission type metal grating, the radius of the grating is 0.1mm, the period is 0.245mm, and the material is molybdenum wire plated with gold.
The side length of the caliber of the sum input port is 25mm, and the side length of the caliber of the difference input port is 24.78mm. The reflector M1, the grating beam splitter and the reflector M2 are sequentially arranged in parallel and form an included angle of 45 degrees with the input port; the spacing between mirror M1 and the grating beam-splitter is 25mm and the spacing between mirror M2 and the grating beam-splitter is 24.78mm, i.e. reduced by λ/4 relative to the former.
The reflector M3 and the reflector M4 are arranged in parallel, an included angle between the reflector M3 and the reflector M1 is 90 degrees, and an included angle between the reflector M4 and the grating beam splitter is 90 degrees. The reflection of the beam in the sum and difference comparator is both a 90 degree reflection.
The incident gaussian beam is generated by a gaussian horn with an operating frequency of 340GHz and a beam waist radius of 5mm.
In order to realize the sum and difference comparator, after the gaussian beam a is input into the sum and input port, it is reflected by the mirror M1 and reaches the grating beam splitter, and then passes through the grating beam splitter and is divided into the transmission beam A2 and the reflection beam A1, at this time, the amplitude of the transmission beam A2 is equal to that of the reflection beam A1, and the phase of the transmission beam A2 = the phase of the reflection beam A1 +90 °. The reflected beam A1 is output from a first output port after being reflected twice by a reflector M4 and a reflector M3 in sequence; the transmitted beam A2 is reflected by the mirror M2 and then output from the second output port. Since the distance between the mirror M1 and the grating beam splitter is h, and the distance L between the mirror M2 and the grating beam splitter is L = h- λ/4, that is, the phase of the transmission beam A2 is advanced by 90 ° when being output from the second output port, the phases and amplitudes of the beams of the two output ports are equal finally, and thus a sum beam is formed.
In order to realize the poor effect of the sum and difference comparator, the gaussian beam B is input into the difference input port, passes through the grating beam splitter, and is divided into the transmission beam B1 and the reflection beam B2, at this time, the transmission beam B1 and the reflection beam B2 have the same amplitude, and the phase of the transmission beam B1 = the phase of the reflection beam B2 +90 °. The transmission beam B1 is output from a first output port after being reflected twice by the reflector M4 and the reflector M3 in sequence; the reflected beam B2 is reflected by the mirror M2 and then output from the second output port. Since the distance between the mirror M1 and the grating beam splitter is h, and the distance L between the mirror M2 and the grating beam splitter is L = h- λ/4, that is, the phase of the reflected beam B2 at the second output port will lead 90 °, the phases of the beams at the two output ports will differ by 180 ° and the amplitudes are equal, thereby forming a difference beam.
As shown in FIG. 2, in the frequency of 330GHz-350GHz, the sum beam has no obvious difference from the sum beam pattern obtained by the central frequency of 340GHz, and the excellent working performance can still be maintained under the bandwidth of 20 GHz.
As shown in FIG. 3, in the frequency range of 330GHz-350GHz, the difference beam has no obvious difference from the difference beam pattern obtained by the central frequency of 340 GHz. It is proved that the excellent working performance can still be maintained under the bandwidth of 20 GHz.
The scheme of the invention can solve the problem of narrow bandwidth of the existing quasi-optical sum-difference comparator due to large distance difference, and has the advantages of low loss, large power capacity and easiness in processing. And because the reflection path difference and the transmission path difference are only lambda/4, the beam spots of the two output ports are almost as large, and the sum-difference radiation characteristic of the sum-difference comparator is effectively improved.
Claims (5)
1. The utility model provides a wide bandwidth's terahertz frequency channel quasi-optical sum difference comparator which characterized in that includes: the system comprises a sum input port, a difference input port, a reflector M1, a reflector M2, a reflector M3, a reflector M4, a grating beam splitter, a first output port and a second output port; after the Gaussian beam vertically enters the input port, the sum effect of the sum and difference comparator is realized by two paths of beams output by the first output port and the second output port; after the Gaussian beam vertically enters the difference input port, the difference effect of the sum and difference comparator is realized by two paths of beams output by the first output port and the second output port;
the reflector M1, the reflector M2, the reflector M3 and the reflector M4 are plane reflectors;
the grating beam splitter is a transmission type metal grating beam splitter and is used for equally dividing power of incident beams and generating a phase difference of 90 degrees;
after the Gaussian beam is input and input into the input port, the Gaussian beam is reflected by the reflector M1 and then reaches the grating beam splitter, part of the Gaussian beam reflected by the grating beam splitter is a beam A1, and part of the Gaussian beam transmitted by the grating beam splitter is a beam A2; the beam A1 is output from a first output port after being reflected twice by a reflector M4 and a reflector M3 in sequence; the beam A2 is reflected by a reflector M2 and then output from a second output port;
after the Gaussian beam B is input into the difference input port, part of the transmitted beam passing through the grating beam splitter is a beam B1, and the reflected part of the beam is a beam B2; the beam B1 is output from a first output port after being reflected twice by a reflector M4 and a reflector M3 in sequence; the beam B2 is reflected by a reflector M2 and then is output from a second output port;
the reflector M1, the grating beam splitter and the reflector M2 are sequentially placed in parallel, the distance between the reflector M1 and the grating beam splitter is h, the distance between the reflector M2 and the grating beam splitter is h-lambda/4, and lambda is the working wavelength;
the reflector M1, the grating beam splitter and the reflector M2 form an included angle of 45 degrees with the input port; the reflector M3 and the reflector M4 are placed in parallel, an included angle between the reflector M3 and the reflector M1 is 90 degrees, and an included angle between the reflector M4 and the grating beam splitter is 90 degrees.
2. The wide bandwidth terahertz frequency band quasi-optical sum and difference comparator as claimed in claim 1, wherein the reflection of the beam in the sum and difference comparator is 90 degree reflection.
3. The wide bandwidth terahertz frequency band quasi-optical sum and difference comparator as claimed in claim 1, wherein the input aperture of the sum input port is square, the side length thereof is h, the input aperture of the difference input port is also square, the side length thereof is h- λ/4, and h is larger than the diameter R when the gaussian beam edge level is 30dB lower than the center level.
4. The wide bandwidth terahertz frequency band quasi-optical sum-difference comparator as claimed in claim 3, wherein said grating beam splitter has a grating radius of 0.1mm, a period of 0.245mm, and is made of gold-plated molybdenum wire.
5. The wide bandwidth terahertz frequency band quasi-optical sum and difference comparator of claim 3, wherein the center frequency of the gaussian beam is greater than 100GHz.
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CN113703156A (en) * | 2021-08-23 | 2021-11-26 | 电子科技大学 | Quasi-optical monopulse antenna based on reflective phase correction mirror |
CN115425422A (en) * | 2022-07-22 | 2022-12-02 | 电子科技大学 | Terahertz quasi-optical sum-difference network based on medium beam splitting and polarization torsion grating |
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US7245432B2 (en) * | 2001-03-28 | 2007-07-17 | Main Street Ventures, Llc | Dual diffraction-grating device |
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US7609392B2 (en) * | 2006-06-28 | 2009-10-27 | California Institute Of Technology | Harmonically matched diffraction grating pair |
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CN105784634A (en) * | 2016-03-31 | 2016-07-20 | 电子科技大学 | Terahertz time domain spectrograph capable of measuring transmission and reflection simultaneously under vertical incidence |
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CN109884600A (en) * | 2018-10-11 | 2019-06-14 | 北京遥感设备研究所 | A kind of sum-difference network test macro and method suitable for terahertz wave band |
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