Ultra-miniature substrate integrated waveguide cavity for a dual-resonance atomic clock

Abstract

The application discloses a double-resonance atomic clock ultra-miniature substrate integrated waveguide chamber, comprising: a substrate integrated waveguide annular gap cavity, the substrate integrated waveguide annular gap cavity is formed by longitudinal stacking of a plurality of longitudinal slit substrate integrated waveguides, the longitudinal slit substrate integrated waveguide comprises a metalized through hole and a metal microstrip line, and the longitudinal slit substrate integrated waveguide is provided with a longitudinal slit; a MEMS atomic gas chamber; a mode matching excitation structure for exciting a microwave magnetic field to the substrate integrated waveguide annular gap cavity; and an electromagnetic shielding and heating assembly arranged outside the substrate integrated waveguide annular gap cavity. The application can effectively solve the key problem that the resonant performance of a printed miniature annular gap cavity is extremely sensitive to the size change of subwavelength structure parameters, increase the processing tolerance of the ultra-miniature integrated chamber, reduce the processing difficulty and manufacturing cost of high-precision PCB through holes, and improve product yield.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of atomic frequency measurement and time-frequency microwave technology, and relates to an ultramicro substrate integrated waveguide cavity of a double-resonance atomic clock. BACKGROUND

[0002] The double-resonance atomic clock has been widely concerned and applied in time service, navigation, satellite positioning, real-time synchronization and the like due to its simple system framework and high frequency stability. Since the double-resonance atomic clock needs to realize resonance in the optical frequency band and the microwave frequency band to meet the transition between the atomic fine energy levels, a resonant cavity capable of providing an accurate microwave resonant frequency is required in the physical system. However, the size of the microwave cavity is usually limited to centimeter level due to the working frequency, and the breakthrough of the microwave cavity miniaturization and micromation technology is still the key to realizing the chipization and light weight of the double-resonance atomic clock.

[0003] In the current field of atomic clock dedicated microwave cavity miniaturization technology, the PCB printed micro annular gap cavity technology is very promising. However, the micro annular gap cavity structure adopting the general PCB processing technology is extremely sensitive to the size change of the microwave cavity structure parameters in the size range of less than 15 mm, the depth-diameter ratio of the through hole of the double-layer stacked annular gap cavity is too large, the through hole of the multi-layer stacked annular gap cavity is eccentric, the manual alignment error is large, the processing tolerance is low, the yield of the finished product is low, the processing cost is increased, and it is not conducive to the further development of the ultramicro integrated cavity of the double-resonance atomic clock, and it cannot meet the single slot deployment requirements of high-density equipment. SUMMARY

[0004] The application aims to solve the above-mentioned problems, and provides an ultramicro substrate integrated waveguide cavity of a double-resonance atomic clock.

[0005] To achieve the above technical purposes, the technical scheme adopted by the application is as follows:

[0006] An ultramicro substrate integrated waveguide cavity of a double-resonance atomic clock comprises:

[0007] A substrate integrated waveguide annular gap cavity is formed by longitudinally stacking a plurality of longitudinal slit substrate integrated waveguides, the longitudinal slit substrate integrated waveguide comprises a plurality of periodically arranged metalized through holes, and the upper and lower surfaces of the longitudinal slit substrate integrated waveguide are covered with metal microstrip lines, the metalized through holes between adjacent layers of longitudinal slit substrate integrated waveguides are not connected to each other and are coupled by the metal microstrip lines in a non-contact manner, and each layer of longitudinal slit substrate integrated waveguide is provided with at least one longitudinal slit, and the longitudinal slits of each layer of longitudinal slit substrate integrated waveguide are aligned to form a longitudinal slit-like waveguide structure with at least one longitudinal slit;

[0008] A MEMS atomic cell is arranged in the inner cavity of the substrate integrated waveguide annular gap cavity, and the MEMS atomic cell is provided with a light transmission hole for axial laser transmission above and below the MEMS atomic cell.

[0009] A mode matching excitation structure is arranged for exciting a microwave magnetic field to the substrate integrated waveguide annular gap cavity.

[0010] An electromagnetic shielding and heating assembly is arranged outside the substrate integrated waveguide annular gap cavity for electromagnetic shielding and uniform heating of the substrate integrated waveguide annular gap cavity and the MEMS atomic cell.

[0011] To optimize the above technical solutions, the specific measures taken also include:

[0012] The ultra-miniature substrate integrated waveguide cavity of the dual-resonance atomic clock further comprises a dielectric matching layer arranged above and below the MEMS atomic cell, and the mode matching excitation structure is arranged above the dielectric matching layer or embedded therein.

[0013] The longitudinal slit substrate integrated waveguide is arranged in the dielectric substrate, and the metal microstrip line is arranged on the upper and lower surfaces of the dielectric substrate.

[0014] The electromagnetic shielding and heating assembly comprises:

[0015] A metal shielding layer is wrapped outside the substrate integrated waveguide annular gap cavity.

[0016] A heating wire is embedded in the metal shielding layer or closely attached to the surface of the metal shielding layer.

[0017] The electromagnetic shielding and heating assembly comprises:

[0018] A substrate integrated waveguide outer shielding layer without longitudinal slits is integrated on the dielectric substrate and located outside the longitudinal slit substrate integrated waveguide, and together with the longitudinal slit substrate integrated waveguide forms a double-loop substrate integrated waveguide structure.

[0019] A metal conductor thin layer is arranged at the top and bottom of the double-loop substrate integrated waveguide structure.

[0020] A heating wire is wound outside the double-loop substrate integrated waveguide structure.

[0021] The interior of the MEMS atomic cell is filled with alkali metal atomic gas and inert gas, the cross section of the MEMS atomic cell is circular or polygonal, and the MEMS atomic cell is formed in a "glass layer-silicon layer-glass layer" three-layer bonding or "glass layer-silicon layer-glass layer-silicon layer-glass layer" five-layer bonding mode in the longitudinal direction.

[0022] The alkali metal atomic gas filled in the interior of the MEMS atomic cell is rubidium atomic gas or cesium atomic gas.

[0023] The mode matching excitation structure comprises an excitation structure substrate, a printed metal microstrip conductor and a microwave coaxial line, the excitation structure substrate is arranged above or embedded in a dielectric matching layer, the printed metal microstrip conductor is fixed on the excitation structure substrate, and the microwave coaxial line is connected with the printed metal microstrip conductor.

[0024] The longitudinal stack number of the longitudinal slot substrate integrated waveguide is greater than or equal to three.

[0025] The working mode of the substrate integrated waveguide annular gap cavity is TE 011 The mode is similar, so that a uniform microwave magnetic field is generated in the area where the MEMS atomic gas chamber is located.

[0026] Compared with the prior art, the beneficial effects of the present application are as follows:

[0027] 1、The substrate integrated waveguide annular gap cavity of the present application is stacked by a multi-layer longitudinal slot substrate integrated waveguide structure, the conductor part is similar in shape to a pure metal annular gap cavity, the high-density metalized through holes in each layer are arranged periodically, the through holes between the layers do not need to be connected, and high-precision alignment is not required, thereby avoiding the processing difficulties caused by the "excessive depth-diameter ratio" and "multi-layer through hole eccentricity" of traditional printed annular gap cavities, greatly reducing the processing difficulty of high-precision, large-depth-diameter-ratio printed annular gap cavity metalized through holes, relieving the key problem that the performance of ultra-miniature integrated chambers is extremely sensitive to the size changes of the sub-wavelength structure parameters of printed microwave cavities, and because the processing difficulty of the ultra-miniature printed annular gap cavity is reduced, the yield of finished products is improved, fine tuning structures can be eliminated, the overall structure design is simplified, and the cost of subsequent manual system tuning is saved.

[0028] 2、The metalized through holes in each layer are connected by non-contact coupling through the metal microstrip lines on the upper and lower layers of the dielectric substrate to form a longitudinal slot waveguide structure, which can increase the longitudinal uniformity of the coupling electric field generated by the slot, thereby improving the three-dimensional spatial distribution uniformity of the TE 011 mode magnetic field;

[0029] 3、The hollow design of the longitudinal slot substrate integrated waveguide further reduces the use of dielectric materials for the printed annular gap cavity, reduces the weight of the overall integrated chamber, and realizes the function of a light and portable product.

[0030] 4、The alkali metal atomic gas chamber prepared by the MEMS process can be filled with alkali metal vapors such as rubidium and cesium, and inert gases. The MEMS process not only facilitates the chip-based batch manufacturing of the atomic gas chamber, but also helps to reduce the volume of the entire integrated chamber due to the use of high-dielectric-constant silicon materials.

[0031] 5. Several dielectric matching layers are disposed above and below the MEMS atomic gas cell. These layers can be made of different materials and are used to enhance the electromagnetic field mode matching at the edge of the substrate integrated waveguide annular cavity and reduce the volume of the annular cavity. The dielectric material needs to possess characteristics such as a low temperature coefficient or temperature compensation to compensate for the slight frequency shift caused by temperature drift in the integrated cavity. This invention, due to reduced fabrication difficulty and the inherent high quality factor of the substrate integrated waveguide, expands the range of dielectric loading materials, increases the selectivity of low-cost dielectric materials with temperature compensation capabilities, and reduces dependence on specific expensive materials.

[0032] 6. This invention precisely excites and stabilizes the TE waveguide, which is most suitable for atomic clock operation, through a "quasi-longitudinal slot waveguide structure". 011 The model, through "interlayer non-contact coupling", ensures the high uniformity of the model in three-dimensional space, thereby making the magnetic field direction inside the cavity consistent and the field rotation factor (FOF) high.

[0033] 7. This invention can reduce the volume of a micro microwave resonant cavity to the millimeter level (<1cm). 3 The diameter can meet the single-slot deployment requirements of high-density equipment, thereby reducing the volume of the micro dual-resonance atomic clock microwave subsystem. Attached Figure Description

[0034] Figure 1 This is a cross-sectional structural diagram of the first embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram of the conductor portion structure of the substrate integrated waveguide annular cavity in the first embodiment of the present invention;

[0036] Figure 3 This is a schematic diagram of the structure of a single-layer longitudinal slot substrate integrated waveguide integrated on a dielectric substrate in the first embodiment of the present invention;

[0037] Figure 4 This is a schematic diagram of the pattern matching excitation structure of the present invention;

[0038] Figure 5 This is a schematic diagram of the structure of a MEMS atomic gas cell;

[0039] Figure 6 This is a schematic diagram of the dielectric matching layer structure;

[0040] Figure 7 This is a cross-sectional structural diagram of the second embodiment of the present invention;

[0041] Figure 8 This is a schematic diagram of the conductor portion structure of the double-loop substrate integrated waveguide annular cavity in the second embodiment of the present invention;

[0042] Figure 9 Figure 2 is a schematic diagram of a single-layer structure of a double-ring substrate integrated waveguide annular gap cavity in a second embodiment of the present application.

[0043] In the figure, the reference signs are: MEMS atomic cell 1, glass layer 2, silicon layer 3, substrate integrated waveguide annular gap cavity 4, metallized via 5, dielectric substrate 6, metal microstrip line 7, longitudinal slit 8, dielectric matching layer 9, mode-matched excitation structure 10, light-through hole 11, excitation structure substrate 12, printed metal microstrip conductor 13, microwave coaxial line 14, heating wire 15, metal shielding layer 16, substrate integrated waveguide outer ring shielding layer 17, and metal conductor thin layer 18. DETAILED DESCRIPTION

[0044] In order to make the purposes, technical solutions and advantages of the present application clearer, the present application is described and explained below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application. Based on the embodiments provided in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0045] Obviously, the drawings described below are only some examples or embodiments of the present application, and for those of ordinary skill in the art, the present application can also be applied to other similar scenarios without creative labor on the basis of these drawings. In addition, it can also be understood that although the efforts made in this development process can be complex and lengthy, for those of ordinary skill in the art related to the content disclosed in the present application, some design, manufacture or production changes based on the technical content disclosed in the present application are only routine technical means and should not be understood as insufficient disclosure of the present application.

[0046] First embodiment:

[0047] Reference Figures 1 to 6 The present embodiment provides an ultraminiature substrate integrated waveguide cavity for a double-resonance atomic clock, which has a structure mainly including five parts from inside to outside: a MEMS atomic cell 1, a substrate integrated waveguide annular gap cavity 4, a dielectric matching layer 9, a mode-matched excitation structure 10, and an electromagnetic shielding and heating assembly.

[0048] The MEMS atomic cell 1 is arranged at the center of the entire cavity, and its structure is as shown in Figure 5 The cell is formed by a five-layer bonding structure of “glass layer-silicon layer-glass layer-silicon layer-glass layer”, and is filled with alkali metal vapor such as rubidium or cesium atoms and inert gas. The structure of the MEMS atomic cell 1 is highly axisymmetric, and the cross section can be circular, quadrilateral or octagonal.

[0049] The substrate integrated waveguide annular gap cavity 4 is nested outside the MEMS atomic gas cell 1 and is the core of the embodiment. As shown in Figure 2 and Figure 3 , the cavity is stacked in the longitudinal direction by multiple layers of identical longitudinal slit substrate integrated waveguides. Each layer of structure is fabricated on a dielectric substrate 6, which is covered with metal microstrip lines 7 on its upper and lower surfaces, and is provided with multiple rows of periodically arranged metallized vias 5 around the periphery. The key is that the metallized vias 5 between adjacent layers are not connected to each other, but are realized by non-contact electromagnetic coupling through the metal microstrip lines 7 on the upper and lower surfaces. Each layer of structure is provided with two longitudinal slits (one or more according to design requirements), and the longitudinal slits of each layer are aligned in the vertical direction to form a longitudinal slit-like waveguide structure with two longitudinal slits 8. This design greatly reduces the aspect ratio of the vias and the alignment accuracy between layers.

[0050] The dielectric matching layer 9 is provided above and below the MEMS atomic gas cell 1, and its structure is shown in Figure 6 . The dielectric matching layer 9 is made of a dielectric material with low temperature coefficient or temperature compensation characteristics, which is used to optimize the electromagnetic field mode matching at the edge of the cavity, and to assist in reducing the cavity volume while compensating for the cavity resonance frequency drift caused by temperature changes.

[0051] The mode matching excitation structure 10 is provided above the dielectric matching layer 9 (or can be embedded therein), and its structure is shown in Figure 4 . It includes an excitation structure substrate 12, a printed metal microstrip conductor 13 fabricated thereon, and a microwave coaxial line 14 connected to the microstrip conductor. The outer diameter of the printed metal microstrip conductor 13 is approximately the same as the outer diameter of the substrate integrated waveguide annular gap cavity 4 to achieve effective magnetic coupling excitation. The mode matching excitation structure 10 is provided with a light passing hole 11.

[0052] The electromagnetic shielding and heating assembly is provided on the outermost layer. As shown in Figure 1 , it includes a metal shielding layer 16 wrapped around the outside of the substrate integrated waveguide annular gap cavity 4, and a heating wire 15 embedded in the shielding layer or closely attached to the surface thereof. The top and bottom of the metal shielding layer 16 are also provided with light passing holes 11, so that the pump light and probe light can pass through the entire structure along the axial direction of the cavity.

[0053] Second embodiment:

[0054] Referring to Figures 4 to 9 , this embodiment provides another ultra-miniature substrate integrated waveguide cavity structure. The main difference between this embodiment and the first embodiment is the implementation of the electromagnetic shielding and heating assembly.

[0055] The MEMS atomic gas cell 1, dielectric matching layer 9 and mode matching excitation structure 10 in this embodiment are the same as in the first embodiment and will not be described again.

[0056] The core of the embodiment is that the independent metal shielding layer 16 is removed, and a double-ring substrate integrated waveguide structure is used to realize electromagnetic shielding. Specifically, an outer ring shielding layer 17 of substrate integrated waveguide without longitudinal slits is additionally added on the same dielectric substrate 6 as the substrate integrated waveguide ring gap cavity 4. The substrate integrated waveguide ring gap cavity 4 in the inner ring and the substrate integrated waveguide outer ring shielding layer 17 in the outer ring jointly constitute a complete double-ring substrate integrated waveguide ring gap cavity, and the conductor part structure is as shown in Figure 8 The single-layer structure is as shown in Figure 9 .

[0057] The top and bottom of the double-ring structure are closed by metal conductor thin layers 18, which can also be made by PCB process, so that the entire cavity (except the light hole 11) forms a complete shielding body. The heating wire 15 is directly wound on the outside of the double-ring substrate integrated waveguide structure for heating.

[0058] Similarly, the top and bottom of the embodiment are provided with light holes 11 for the laser to pass axially.

[0059] Working principle summary: in operation, first, the cavity is heated by the heating wire 15, so that the alkali metal in the MEMS atomic cell 1 becomes vapor. Then, the mode matching excitation structure 10 couples the microwave signal into the substrate integrated waveguide ring gap cavity 4, and excites a highly uniform TE 011 mode magnetic field in the MEMS atomic cell 1 region. At the same time, the laser beam axially passes through the light holes 11 at the top and bottom, interacts with the atoms, and realizes the locking of the atomic clock through the optical-microwave double resonance principle.

[0060] The above embodiment is the preferred embodiment of the present application, but the embodiment of the present application is not limited by the above-mentioned embodiment, and any change, modification, replacement, combination, simplification made without departing from the spirit and principle of the present application shall be an equivalent replacement mode, and shall be included in the protection scope of the present application.

Claims

1. A sub-micron scale substrate integrated waveguide cavity for a dual-resonator atomic clock, characterized in that, The application relates to a microwave atomic clock, which comprises the following parts: a substrate integrated waveguide annular gap cavity (4) formed by longitudinally stacking a plurality of longitudinally slotted substrate integrated waveguides, wherein each longitudinally slotted substrate integrated waveguide comprises a plurality of periodically arranged metalized through holes (5), the upper and lower surfaces of each longitudinally slotted substrate integrated waveguide are covered with metal microstrip lines (7), the metalized through holes (5) of adjacent longitudinally slotted substrate integrated waveguides are not connected with each other and are coupled by the metal microstrip lines (7) in a non-contact mode, and each longitudinally slotted substrate integrated waveguide is provided with at least one longitudinal slot, and the longitudinal slots of the longitudinally slotted substrate integrated waveguides are aligned to form a longitudinally slotted waveguide structure with at least one longitudinal slot (8); a MEMS atomic cell (1) arranged in the inner cavity of the substrate integrated waveguide annular gap cavity (4), wherein the upper and lower surfaces of the MEMS atomic cell (1) are provided with light transmission holes (11) for the axial transmission of laser beams; a mode matching excitation structure (10) for exciting a microwave magnetic field to the substrate integrated waveguide annular gap cavity (4); and an electromagnetic shielding and heating assembly arranged outside the substrate integrated waveguide annular gap cavity (4) and used for shielding and uniformly heating the substrate integrated waveguide annular gap cavity (4) and the MEMS atomic cell (1). The microwave atomic clock further comprises a dielectric matching layer (9) arranged above and below the MEMS atomic cell (1), and the mode matching excitation structure (10) is arranged above the dielectric matching layer (9) or embedded in the dielectric matching layer (9). The longitudinally slotted substrate integrated waveguide is arranged in a dielectric substrate (6), and the metal microstrip lines (7) are arranged on the upper and lower surfaces of the dielectric substrate (6). The electromagnetic shielding and heating assembly comprises a metal shielding layer (16) wrapped outside the substrate integrated waveguide annular gap cavity (4) and a heating wire (15) embedded in the metal shielding layer (16) or closely attached to the surface of the metal shielding layer (16). The electromagnetic shielding and heating assembly comprises a longitudinally slotted substrate integrated waveguide outer shielding layer (17) integrated on the dielectric substrate (6) and located outside the longitudinally slotted substrate integrated waveguide, and the longitudinally slotted substrate integrated waveguide outer shielding layer (17) and the longitudinally slotted substrate integrated waveguide jointly form a double-circle substrate integrated waveguide structure; a metal conductor thin layer (18) arranged on the top and bottom of the double-circle substrate integrated waveguide structure; and a heating wire (15) wound outside the double-circle substrate integrated waveguide structure.

2. A subminiature substrate integrated waveguide chamber of a dual-resonance atomic clock according to claim 1, characterized in that, The interior of the MEMS atomic cell (1) is filled with alkali metal atomic gas and inert gas, the cross section of the MEMS atomic cell (1) is circular or polygonal, and the MEMS atomic cell (1) is formed by three-layer bonding of "glass layer-silicon layer-glass layer" or five-layer bonding of "glass layer-silicon layer-glass layer-silicon layer-glass layer" in the longitudinal direction.

3. A sub-micron waveguide cavity for a dual-resonance atomic clock according to claim 2, wherein, The alkali metal atomic gas filled in the interior of the MEMS atomic cell (1) is rubidium atomic gas or cesium atomic gas.

4. A sub-micron waveguide cavity for a dual-resonance atomic clock according to claim 3, wherein, ​ ​ ​ 5. A subminiature waveguide cavity for a dual-resonance atomic clock according to claim 3, characterized in that, ​ ​ ​ ​ 6. A sub-micron waveguide cavity for a dual-resonance atomic clock according to claim 4 or 5, characterized in that, ​ 7. A sub-micron waveguide cavity for a dual-resonance atomic clock according to claim 6, wherein, ​ 8. A subminiature waveguide cavity for a dual-resonance atomic clock according to claim 2, characterized in that, The mode-matched excitation structure (10) comprises an excitation structure substrate (12), a printed metal microstrip conductor (13) and a microwave coaxial line (14), the excitation structure substrate (12) is arranged above or embedded in the dielectric matching layer (9), the printed metal microstrip conductor (13) is fixed on the excitation structure substrate (12), and the microwave coaxial line (14) is connected with the printed metal microstrip conductor (13).

9. A subminiature substrate integrated waveguide chamber of a dual-resonance atomic clock according to claim 2, characterized in that, The longitudinal stack number of the longitudinal slot substrate integrated waveguide is greater than or equal to three.

10. The ultra-compact substrate integrated waveguide chamber of a dual-resonance atomic clock of claim 1, wherein, The substrate integrated waveguide annular gap cavity (4) works in TE 011 Class mode to generate a uniform microwave magnetic field in the area where the MEMS atomic cell (1) is located.

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