Ultra-low temperature millimeter-wave narrow-band passband frequency selective surface filter

Abstract

The present invention discloses an ultra-low temperature millimeter wave narrow-band passband frequency selective surface filter, the filter comprises a first dielectric substrate, a first metal resonance layer, a second dielectric substrate, a second metal resonance layer and a third dielectric substrate stacked from top to bottom, the first metal resonance layer is etched with a first inner slit and a first outer slit surrounding the first inner slit, the second metal resonance layer is etched with a second inner slit and a second outer slit surrounding the second inner slit, the first inner slit and the second inner slit are correspondingly distributed up and down, and the first outer slit and the second outer slit are correspondingly distributed up and down. The filter of the present invention can work at an ultra-low sub-Kelvin temperature, and has the advantages of narrow in-band selection frequency, good out-of-band suppression performance, small size, small mass, easy processing and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of terahertz filters, and in particular relates to an ultra-low temperature millimeter wave narrow-band passband frequency selective surface filter, which can be applied to the fields of ultra-low temperature terahertz security inspection, space aerospace, cosmic ray observation, etc. Background Art

[0002] Frequency Selective Surface (FSS) is a spatial filter that exhibits obvious bandpass or bandstop filtering characteristics when interacting with electromagnetic waves. Frequency selective surfaces have been fully applied to a series of fields such as radar covers, quasi-optical detection systems, cosmic ray detection systems, and medical imaging systems. Due to the bandpass filtering characteristics of frequency selective surfaces, FSS is widely used in millimeter wave, terahertz, and infrared to visible light bands in terms of frequency selection. In the measurement system, the filter frequency selective surface can be used to filter out interference signals or noise signals outside the main signal frequency band, and selectively pass signals within the signal frequency band.

[0003] Compared with traditional microwave filters, the frequency response of terahertz frequency selective surface FSS is not only determined by the frequency range, but also by the incident angle of electromagnetic waves, which is an important factor affecting the frequency response. Traditional bandpass frequency selective surface FSS is generally composed of a single layer of parallel resonance. This design is simple and easy to analyze, but at the cutoff frequency chopping, it will increase the bandwidth and introduce signals of other frequencies into the system. Therefore, this single-layer frequency selective surface may cause the passband signal to be greatly interfered in practical applications.

[0004] With the development of spatial filters based on frequency selective surfaces in the fields of security inspection, aerospace and medicine, the requirements for the system signal-to-noise ratio are extremely high, so the filter is required to filter out the non-bandpass working band to the maximum extent. However, filters based on frequency selective surfaces often form a second harmonic bandpass in the bandpass band, which reduces the cleanliness of the frequency band in the system.

[0005] In addition, with the development of spatial filters based on frequency selective surfaces in the fields of security inspection, aerospace and medicine, detectors are required to operate at ultra-low sub-Kelvin temperatures.

[0006] Therefore, in view of the above technical problems, it is necessary to provide an ultra-low temperature millimeter wave narrow-band passband frequency selective surface filter. Summary of the invention

[0007] In view of this, the purpose of the present invention is to provide an ultra-low temperature millimeter-wave narrow-band passband frequency selective surface filter, which can meet the frequency application range of security inspection, aerospace and medical treatment, and when the incident angle of electromagnetic waves in space changes, the frequency response of the device is relatively stable.

[0008] In order to achieve the above purpose, the technical solution provided by an embodiment of the present invention is as follows:

[0009] An ultra-low temperature millimeter wave narrowband pass frequency selective surface filter, the filter comprises a first dielectric substrate, a first metal resonance layer, a second dielectric substrate, a second metal resonance layer and a third dielectric substrate stacked from top to bottom, a first inner slit and a first outer slit surrounding the first inner slit are etched in the first metal resonance layer, a second inner slit and a second outer slit surrounding the second inner slit are etched in the second metal resonance layer, the first inner slit and the second inner slit are correspondingly distributed up and down, and the first outer slit and the second outer slit are correspondingly distributed up and down.

[0010] In one embodiment, the first inner slit and the second inner slit are inner cross slits, and the first outer slit and the second outer slit are outer cross slits.

[0011] In one embodiment, the first inner slit and the second inner slit are circular slits, and the first outer slit and the second outer slit are outer cross slits.

[0012] In one embodiment, the length of the first inner slit and the second inner slit is 90 to 130 μm, and the width is 10 to 13 μm. The outer side length of the first outer slit and the second outer slit is 100 to 140 μm, the inner side length is 80 to 120 μm, and the width is 10 to 13 μm. The distance between the first outer slit and the edge of the first metal resonance layer or the second outer slit and the edge of the second metal resonance layer is 30 to 50 μm.

[0013] In one embodiment, the inner diameter of the first inner slit and the second inner slit is 70-100 μm, and the width is 10-13 μm. The outer side length of the first outer slit and the second outer slit is 100-140 μm, the inner side length is 80-120 μm, and the width is 10-13 μm. The distance between the first outer slit and the edge of the first metal resonance layer or the distance between the second outer slit and the edge of the second metal resonance layer is 30-50 μm.

[0014] In one embodiment, the thicknesses of the first dielectric substrate, the second dielectric substrate, and the third dielectric substrate are equal, which is 50-200 μm. The materials of the first dielectric substrate, the second dielectric substrate, and the third dielectric substrate are the same, and the dielectric constant ε is 1.5-3.

[0015] In one embodiment, the material of the first dielectric substrate, the second dielectric substrate, and the third dielectric substrate is benzocyclobutene, and the dielectric constant ε=2.67.

[0016] In one embodiment, the thickness of the first metal resonance layer and the second metal resonance layer are equal, and are 1-20 μm.

[0017] In one embodiment, the first metal resonance layer and the second metal resonance layer are made of copper or other metals with high electrical conductivity, such as gold, silver, titanium, and aluminum.

[0018] In one embodiment, the first inner slit, the first outer slit, the second inner slit, and the second outer slit are filled with the same material as the first dielectric substrate, the second dielectric substrate, and the third dielectric substrate.

[0019] The present invention has the following beneficial effects:

[0020] The filter of the present invention has the advantages of small insertion loss, small volume, small return loss and small group delay, and meets the requirements of millimeter wave security inspection, aerospace and space exploration;

[0021] The filter of the present invention exhibits very good narrowband selection characteristics and out-of-band suppression characteristics, especially excellent passband second harmonic removal performance;

[0022] The filter structure of the present invention helps to reduce the unit size, thereby reducing the sensitivity to different electromagnetic wave incident angles;

[0023] The present invention uses a metal resonance layer surface etching pattern, and the dielectric substrate is an ultra-low heat absorption material benzocyclobutene. The processing technology is simple, the supporting medium cost is low, the volume is small, the ultra-low temperature use characteristics of the filter can be realized, and large-scale production can be carried out. The assembly between the layers is simple and easy to implement, thereby extending the service life of the frequency selective surface filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 Schematic diagram of the three-dimensional structure of a frequency selective surface (RCC) filter in the first embodiment of the present invention;

[0026] Figure 2 is a schematic diagram of the planar structure of the first metal resonance layer in the first embodiment of the present invention;

[0027] Figure 3 It is a schematic diagram of the three-dimensional structure of a frequency selective surface (RCR) filter in the second embodiment of the present invention;

[0028] Figure 4 is a schematic diagram of the planar structure of the first metal resonance layer in the second embodiment of the present invention;

[0029] Figure 5 is a transmission coefficient and reflection coefficient curve diagram of a frequency selective surface (RCC) in the first embodiment of the present invention;

[0030] Figure 6 is a transmission coefficient and reflection coefficient curve diagram of a frequency selective surface (RCR) in a second embodiment of the present invention;

[0031] Figure 7 Transmission coefficient diagrams of the frequency selective surface (RCC) and the frequency selective surface (RCR) in the first and second embodiments of the present invention;

[0032] Figure 8 is a transmission coefficient diagram corresponding to different incident angles of the frequency selective surface (RCC) in the first embodiment of the present invention;

[0033] Fig. 9 FIG. 4 is a transmission coefficient diagram corresponding to different incident angles of the frequency selective surface (RCR) in the second embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0035] As frequency selective surface spatial filtering structures are increasingly used in security inspection, aerospace, space exploration, and medical imaging, higher requirements are placed on the operating temperature, structure, weight, ease of processing, and suppression outside the working frequency band of the filter. However, most of the existing bandpass frequency selective surfaces are large in size, heavy in weight, and have poor out-of-band selectivity, especially at the dual resonant frequency, showing bandpass characteristics, which greatly affects the use effect of the frequency selective surface. In view of the shortcomings of the prior art, the present invention proposes a bandpass frequency selective surface filter that can operate at ultra-low pressure Kelvin temperature, has a narrow in-band selection frequency, has good out-of-band suppression performance, is small in size, has low mass, and is easy to process.

[0036] The present invention discloses an ultra-low temperature millimeter wave narrow-band pass frequency selective surface filter. The filter comprises a first dielectric substrate, a first metal resonance layer, a second dielectric substrate, a second metal resonance layer and a third dielectric substrate which are stacked from top to bottom. A first inner slit and a first outer slit surrounding the first inner slit are etched in the first metal resonance layer. A second inner slit and a second outer slit surrounding the second inner slit are etched in the second metal resonance layer. The first inner slit and the second inner slit are correspondingly distributed up and down, and the first outer slit and the second outer slit are correspondingly distributed up and down.

[0037] Preferably, the first inner slit and the second inner slit are inner cross slits, and the first outer slit and the second outer slit are outer cross slits. The length of the first inner slit and the second inner slit is 90-130 μm, and the width is 10-13 μm. The outer side length of the first outer slit and the second outer slit is 100-140 μm, the inner side length is 80-120 μm, and the width is 10-13 μm. The distance between the first outer slit and the edge of the first metal resonance layer or the second outer slit and the edge of the second metal resonance layer is 30-50 μm.

[0038] Preferably, the first inner slit and the second inner slit are circular slits, and the first outer slit and the second outer slit are outer cross slits. The inner diameter of the first inner slit and the second inner slit is 70-100 μm, the width is 10-13 μm, the outer side length of the first outer slit and the second outer slit is 100-140 μm, the inner side length is 80-120 μm, the width is 10-13 μm, and the distance between the first outer slit and the edge of the first metal resonance layer or the second outer slit and the edge of the second metal resonance layer is 30-50 μm.

[0039] The thickness of the first dielectric substrate, the second dielectric substrate and the third dielectric substrate is equal, which is 50 to 200 μm, and the materials of the first dielectric substrate, the second dielectric substrate and the third dielectric substrate are the same, and the dielectric constant ε is 1.5 to 3. Preferably, the material of the first dielectric substrate, the second dielectric substrate and the third dielectric substrate is benzocyclobutene, and the dielectric constant ε is 2.67.

[0040] The first metal resonance layer and the second metal resonance layer have the same thickness, which is 1-20 μm. Preferably, the first metal resonance layer and the second metal resonance layer are made of copper or other high-conductivity metals, such as gold, silver, titanium, and aluminum.

[0041] Furthermore, the first inner slit and the first outer slit, the second inner slit and the second outer slit are filled with the same material as the first dielectric substrate, the second dielectric substrate and the third dielectric substrate.

[0042] The present invention achieves the performance of enhancing the chopping cut-off frequency by stacking a plurality of single-layer frequency selective surfaces, thereby realizing narrow-band bandpass filtering.

[0043] The present invention not only realizes ultra-narrow in-band selectivity of the filter during structural manufacturing, but also does not generate out-of-band secondary and higher harmonics.

[0044] The present invention adopts the method of benzocyclobutene and air spacing, so that the filter insulating material no longer absorbs electromagnetic radiation heat to increase the thermal load of the measurement system, so that the filter is suitable for use in an ultra-low temperature test environment.

[0045] The present invention is further described below in conjunction with specific embodiments.

[0046] Ginseng Figure 1 , Figure 2 As shown, in the first embodiment of the present invention, an ultra-low temperature millimeter wave narrowband pass frequency selective surface (RCC) filter is provided. The filter comprises a first dielectric substrate 11, a first metal resonance layer 14, a second dielectric substrate 12, a second metal resonance layer 15 and a third dielectric substrate 13 which are stacked from top to bottom. A first inner slit 141 and a first outer slit 142 surrounding the first inner slit are etched in the first metal resonance layer 14. A second inner slit 151 and a second outer slit 152 surrounding the second inner slit are etched in the second metal resonance layer 15. The first inner slit 141 and the second inner slit 151 are correspondingly distributed up and down, and the first outer slit 142 and the second outer slit 152 are correspondingly distributed up and down.

[0047] In this embodiment, the length and width of the first dielectric substrate 11, the second dielectric substrate 12 and the third dielectric substrate 13 are all 297.82 μm, the thickness is all 121 μm, and the material is benzocyclobutene, and its relative dielectric constant ε = 2.67. The length and width of the first metal resonance layer 14 and the second metal resonance layer 15 are all 297.82 μm, the thickness is all 2 μm, and the material is metal copper.

[0048] Ginseng Figure 2 As shown, in this embodiment, the first inner slit 141 and the second inner slit 151 are inner cross slits, and the first outer slit 142 and the second outer slit 152 are outer cross slits. The first inner slit 141 and the second inner slit 151 and the first outer slit 142 and the second outer slit 152 are all filled with benzocyclobutene.

[0049] Taking the first inner slit 141 and the first outer slit 142 as an example, the length l of the first inner slit 141 is 1-1 110.0μm, width w 1-1 is 11.6 μm, and the outer side length l of the first outer slit 142 is 1-2 126μm, l 1-3 is 46.71 μm, and the inner side length is l 1-4 102.2μm, l 1-5 is 46.71μm, width w1-2 is 11.9 μm, and the distance d between the first outer slit and the edge of the first metal resonance layer is 1-1 The size of the second inner slit 151 and the second outer slit 152 is completely the same as the size of the first inner slit 141 and the first outer slit 142, and will not be described again.

[0050] Ginseng Figure 3 , Figure 4 As shown, in the second embodiment of the present invention, an ultra-low temperature millimeter wave narrow-band pass frequency selective surface (RCR) filter is provided. The filter comprises a first dielectric substrate 21, a first metal resonance layer 24, a second dielectric substrate 22, a second metal resonance layer 25 and a third dielectric substrate 23 which are stacked from top to bottom. A first inner slit 241 and a first outer slit 242 surrounding the first inner slit are etched in the first metal resonance layer 24. A second inner slit 251 and a second outer slit 252 surrounding the second inner slit are etched in the second metal resonance layer 25. The first inner slit 241 and the second inner slit 251 are correspondingly distributed up and down, and the first outer slit 242 and the second outer slit 252 are correspondingly distributed up and down.

[0051] In this embodiment, the length and width of the first dielectric substrate 21, the second dielectric substrate 22 and the third dielectric substrate 23 are all 297.6 μm, the thickness is all 121 μm, and the material is benzocyclobutene, and its relative dielectric constant ε = 2.67. The length and width of the first metal resonance layer 24 and the second metal resonance layer 25 are all 297.6 μm, the thickness is all 2 μm, and the material is metal copper.

[0052] Ginseng Figure 4 As shown, the first inner slit 241 and the second inner slit 251 in this embodiment are inner annular slits, and the first outer slit 242 and the second outer slit 252 are outer cross slits. The first inner slit 241 and the second inner slit 251 and the first outer slit 242 and the second outer slit 252 are all filled with benzocyclobutene.

[0053] Taking the first inner slit 241 and the first outer slit 242 as an example, the inner diameter l of the first inner slit 241 is 2-1 is 86.8μm, width w 2-1 is 11.6 μm, and the outer side length l of the first outer slit 242 is 2-2 126μm, l 2-3 44.6μm, inner side length l 2-4 102.2μm, l 2-5 is 44.6μm, width w 2-2 is 11.9 μm, and the distance d between the first outer slit and the edge of the first metal resonance layer is 2-1The sizes of the second inner slit 251 and the second outer slit 252 are exactly the same as the sizes of the first inner slit 241 and the first outer slit 242, and will not be described again.

[0054] Ginseng Figure 5 , Figure 6 The transmission coefficient and reflection coefficient curves of the frequency selective surface in the first embodiment and the second embodiment of the present invention are shown respectively. It can be seen from the figure that the insertion loss of the filter in the working frequency band of 275GHz is close to 0dB, the working bandwidth is controlled between 15-25%, and the resonance at the second harmonic frequency of 550GHz is completely suppressed.

[0055] Ginseng Figure 7 The transmission coefficient diagram of the frequency selective surface in the first embodiment and the second embodiment of the present invention is shown. It can be seen that both embodiments have excellent passband second harmonic removal performance, especially the second embodiment has a narrower frequency selective filtering function.

[0056] Ginseng Figure 8 , Fig. 9 The transmission coefficient diagrams of the frequency selective surface at different incident angles of the first embodiment and the second embodiment of the present invention are shown respectively. Both embodiments can work within the working range of the incident angle from 0-45°, and the 275GHz working frequency band does not receive any local interference.

[0057] It should be understood that the above embodiments are described by taking inner slits and outer slits of specific sizes as examples. In other embodiments, the structures and sizes of the inner slits and outer slits are not limited to those in the above embodiments.

[0058] It can be seen from the above technical solutions that the present invention has the following advantages:

[0059] The filter of the present invention has the advantages of small insertion loss, small volume, small return loss and small group delay, and meets the requirements of millimeter wave security inspection, aerospace and space exploration;

[0060] The filter of the present invention exhibits very good narrowband selection characteristics and out-of-band suppression characteristics, especially excellent passband second harmonic removal performance;

[0061] The filter structure of the present invention helps to reduce the unit size, thereby reducing the sensitivity to different electromagnetic wave incident angles;

[0062] The present invention uses a metal resonance layer surface etching pattern, and the dielectric substrate is an ultra-low heat absorption material benzocyclobutene. The processing technology is simple, the supporting medium cost is low, the volume is small, the ultra-low temperature use characteristics of the filter can be realized, and large-scale production can be carried out. The assembly between the layers is simple and easy to implement, thereby extending the service life of the frequency selective surface filter.

[0063] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0064] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. An ultra-low temperature millimeter wave narrow-band pass frequency selective surface filter, characterized in that: The filter comprises a first dielectric substrate, a first metal resonance layer, a second dielectric substrate, a second metal resonance layer and a third dielectric substrate stacked from top to bottom, a first inner slit and a first outer slit surrounding the first inner slit are etched in the first metal resonance layer, a second inner slit and a second outer slit surrounding the second inner slit are etched in the second metal resonance layer, the first inner slit and the second inner slit are correspondingly distributed up and down, and the first outer slit and the second outer slit are correspondingly distributed up and down; The first inner slit and the second inner slit are inner cross slits, the first outer slit and the second outer slit are outer cross slits, the length of the first inner slit and the second inner slit is 90-130 μm, the width is 10-13 μm, the outer side length of the first outer slit and the second outer slit is 100-140 μm, the inner side length is 80-120 μm, the width is 10-13 μm, and the distance between the first outer slit and the edge of the first metal resonance layer or the second outer slit and the edge of the second metal resonance layer is 30-50 μm; Or, the first inner slit and the second inner slit are circular slits, the first outer slit and the second outer slit are outer cross slits, the inner diameters of the first inner slit and the second inner slit are 70-100 μm, the widths are 10-13 μm, the outer side lengths of the first outer slit and the second outer slit are 100-140 μm, the inner side lengths are 80-120 μm, the widths are 10-13 μm, and the distances between the first outer slit and the edge of the first metal resonance layer or between the second outer slit and the edge of the second metal resonance layer are 30-50 μm; The thickness of the first dielectric substrate, the second dielectric substrate and the third dielectric substrate are equal, which is 50 to 200 μm. The materials of the first dielectric substrate, the second dielectric substrate and the third dielectric substrate are the same, and the dielectric constant ε is 1.5 to 3; The first inner slit and the first outer slit, the second inner slit and the second outer slit are filled with the same material as the first dielectric substrate, the second dielectric substrate and the third dielectric substrate.

2. The ultra-low temperature millimeter wave narrow-band pass frequency selective surface filter according to claim 1, characterized in that: The material of the first dielectric substrate, the second dielectric substrate and the third dielectric substrate is benzocyclobutene, and the dielectric constant ε=2.

67.

3. The ultra-low temperature millimeter wave narrow-band pass frequency selective surface filter according to claim 1, characterized in that: The thickness of the first metal resonance layer and the second metal resonance layer are equal, and are 1-20 μm.

4. The ultra-low temperature millimeter wave narrow-band pass frequency selective surface filter according to claim 1, characterized in that: The material of the first metal resonance layer and the second metal resonance layer is metal, including at least one of copper, gold, silver, titanium and aluminum.

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