Microwave resonant cavity of miniature rubidium atomic clock and implementation method of microwave resonant cavity

Abstract

The invention belongs to the technical field of atomic clocks, and particularly relates to a microwave resonant cavity of a miniature rubidium atomic clock and an implementation method of the microwave resonant cavity. The microwave cavity is manufactured by adopting a printed board process, has the characteristics of miniaturization and even chip formation, is low in production cost, can be produced in a quantized manner, has a TE011 resonance mode suitable for rubidium atoms, can ensure the performance of the atomic clock while a physical system of the rubidium atomic clock is miniaturized, overcomes the defect that a traditional rubidium atomic clock is limited by the size of the microwave cavity, and has a wide application prospect. And miniaturization is difficult. The rubidium atomic clock based on the miniature microwave cavity is expected to realize chip design, and has wide application prospects in the fields of communication, navigation, network, electric power and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of atomic clocks, and in particular relates to a microwave resonant cavity of a miniature rubidium atomic clock and a realization method thereof. Background Art

[0002] Accurate time signals are the basis for the normal operation of many precision instruments and electronic equipment, and are closely related to people's daily life, scientific research, and national defense construction. Currently, the most precise timing tool is the atomic clock based on atomic transition frequency discrimination. Traditional atomic clocks include hydrogen atomic clocks, cesium atomic clocks, and rubidium atomic clocks, which have been widely used in communication, network, satellite navigation and other systems. Among them, the rubidium atomic clock is the smallest and most widely used, but due to the limitation of the size of the microwave cavity, the rubidium atomic clock is difficult to achieve miniaturization and chip design like the CPT atomic clock, which greatly limits the application of the rubidium atomic clock. Summary of the invention

[0003] In order to solve the problem that the size of the traditional rubidium atomic clock microwave cavity is large and it is difficult to achieve miniaturization under the premise of ensuring the resonance mode of the microwave cavity, the present invention proposes a miniature rubidium atomic clock microwave cavity using a printed circuit board process, which can achieve miniaturization or even a chip-level microwave resonator. At the same time, its resonance mode is the TE011 mode, and the magnetic lines are parallel to the optical axis, which is beneficial to the magnetic resonance transition of the rubidium atoms and ensures the signal-to-noise ratio of the atomic clock frequency discrimination signal.

[0004] The technical solution of the present invention is:

[0005] A microwave resonant cavity of a miniature rubidium atomic clock, characterized in that:

[0006] The microwave resonant cavity comprises a rubidium atom gas chamber 1, a pole piece 2 and a cylindrical cavity 3;

[0007] The rubidium atom gas chamber 1, the pole piece 2 and the cylindrical cavity 3 are all hollow cylinders;

[0008] The rubidium atom gas chamber 1 is installed in the pole piece 2, and the pole piece 2 is installed in the cylindrical cavity 3;

[0009] The sides of the pole piece 2 and the cylindrical cavity 3 are both provided with holes for the passage of the action light of the rubidium atomic clock.

[0010] The pole piece 2 is made in the conductor layer of the multi-layer printed circuit board, and pole pieces of different layers are connected by through holes.

[0011] The space between the pole piece 2 and the cylindrical cavity 3 is filled with a circuit board.

[0012] The dielectric constant of the circuit board is selected according to actual needs. By selecting a board with a larger dielectric constant as the filling material, the distance between the pole piece 2 and the cylindrical cavity 3 or the thickness of the pole piece can be reduced, further reducing the size of the microwave cavity.

[0013] A method for realizing a microwave resonant cavity of a miniature rubidium atomic clock, wherein the cylindrical cavity 3 is made of metal material or made by printed circuit board technology;

[0014] The thickness and outer diameter of the cylindrical cavity 3 are determined according to the size requirements of the microwave cavity of the micro atomic clock;

[0015] The inner diameter of the cylindrical cavity 3 is the same as the outer diameter of the pole piece 2;

[0016] The cylindrical cavity 3 is used to install the pole piece 2 .

[0017] The rubidium atom gas chamber 1 is cylindrical and filled with alkali metal rubidium and an inert buffer gas. The inert buffer gas is a combined gas, including nitrogen, argon and neon. The gas component ratio and pressure are controlled to obtain a narrower discrimination spectrum line width and good temperature characteristics.

[0018] The pole piece 2 is manufactured by printed circuit board technology and has a multi-layer stacked structure;

[0019] The circuit board substrate is made of a material with a certain dielectric constant and is in the shape of a ring. The inner diameter of the ring is slightly larger than the outer diameter of the rubidium atom gas chamber 1 to ensure that the rubidium atom gas chamber 1 can be installed inside the pole piece.

[0020] The pole piece adopts a circular PCB conductor design and is made of copper foil. The copper foil, circuit board substrate and prepreg are pressed together under high temperature and pressure through pressing technology to form a multi-layer structure.

[0021] The thickness and number of each layer of the multilayer structure are determined based on the size of the rubidium atomic gas chamber 1, the resonant frequency and quality factor of the microwave resonant cavity, and the size requirements of the microwave cavity for the micro rubidium atomic clock;

[0022] The length of the atomic gas chamber is the same as the thickness of the multilayer structure, and the smaller the thickness of each layer of the multilayer structure and the more layers there are, the better the performance of the microwave resonant cavity.

[0023] The present invention has the following beneficial effects

[0024] The present invention provides a micro-rubidium atomic clock microwave cavity and an implementation method. It is manufactured by printed circuit board technology, has excellent characteristics such as small size, good resonance mode, low cost, and is conducive to mass production. It can realize a micro-microwave cavity of TE011 mode, which solves the technical problem that the traditional rubidium atomic clock cannot be miniaturized due to the limitation of microwave cavity size. It has important application prospects in the field of micro-rubidium atomic clocks, and has important value for miniaturization and even chipization of rubidium atomic clocks, as well as market promotion. The microwave cavity proposed by the present invention is manufactured by printed circuit board technology, has the characteristics of miniaturization and even chipization, and has low production cost and can be quantified. It has a TE011 resonance mode suitable for rubidium atoms, and can ensure the performance of the atomic clock while miniaturizing the physical system of the rubidium atomic clock, and overcomes the disadvantage that the traditional rubidium atomic clock is limited by the size of the microwave cavity and is difficult to miniaturize. The rubidium atomic clock based on the micro-microwave cavity is expected to realize chip design, and has broad application prospects in the fields of communication, navigation, network, electricity, etc.

[0025] The present invention relates to a microwave cavity of a miniature rubidium atomic clock and an implementation method thereof, and belongs to the field of atomic clocks. A microwave cavity design and implementation method suitable for a miniature rubidium atomic clock is provided, comprising: a cylindrical outer cavity, a pole piece structure and an atomic gas chamber. The pole piece structure is composed of a metal pole piece copper foil, a pole piece gap, a circuit board substrate, a prepreg and a conductive through hole, and is manufactured by a printed circuit board process, and a TE011 resonance mode is formed under the joint action of the metal pole piece, the pole piece gap and the metal inner wall of the cylindrical outer cavity. The microwave cavity can realize miniaturization design, and has the advantages of low cost, short production cycle, and batch production, etc., which is of great significance to the miniaturization and even chipization of rubidium atomic clocks, as well as market promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The overall composition diagram of the microwave cavity of the micro-rubidium atomic clock, where the left picture is a plane view in the direction of the optical axis, and the right picture is a side cross-sectional view), 1. Atomic gas chamber, 2. Pole structure, 3. Cylindrical outer cavity;

[0027] Figure 2 The diagram of the composition of the microwave cavity pole piece of a micro-rubidium atomic clock, where the drawing is a plane view in the direction of the optical axis, and the right figure is a side cross-sectional view). The diagram of the composition of the microwave cavity pole piece of a micro-rubidium atomic clock (left: plane view in the direction of the optical axis, right: side cross-sectional view), where 2.1 pole piece gap, 2.2 circuit board substrate, 2.3 metal pole piece, 2.4 metal through hole, 2.5 prepreg;

[0028] Figure 3 Schematic diagram of the embodiment and simulation results;

[0029] Figure 4 It is a plan view of the optical axis direction of the embodiment. DETAILED DESCRIPTION

[0030] The present invention will be described below in conjunction with the accompanying drawings.

[0031] A microwave resonant cavity of a miniature rubidium atomic clock adopts a magnetron microwave cavity structure design and is cylindrical in shape. The microwave cavity has holes on both sides of the cylindrical cavity along the central axis for the action light of the rubidium atomic clock to pass through. A rubidium atomic gas chamber is embedded in the cavity. The basic composition structure is as follows: Figure 1 As shown, it is mainly composed of a rubidium atom gas chamber 1, a pole piece structure 2 and a cylindrical cavity 3. The outer contours of the three components are all cylindrical, and the rubidium atom gas chamber 1 is installed in the pole piece structure 2, and the pole piece structure 2 is installed in the cylindrical cavity 3.

[0032] The microwave cavity pole piece is made on the conductor layer of the multilayer printed circuit board, and the pole pieces of different layers are connected by through holes. The pole piece and the external cavity are filled with a circuit board. The dielectric constant of the circuit board can be selected according to actual needs. Compared with air directly used as a filling material, the dielectric constant can be selected more selectively. According to the magnetron microwave cavity resonance formula (1), by selecting a plate with a larger dielectric constant as the filling material, the distance between the pole piece and the external cavity or the thickness of the pole piece can be reduced, and the size of the microwave cavity can be further reduced. In the formula, n represents the number of pole pieces inside the microwave resonant cavity, t is the gap width between the pole pieces, w is the thickness of the pole piece, R represents the cavity radius of the cylindrical microwave cavity, r is the pole piece radius, and h is the pole piece length;

[0033]

[0034] The magnetron microwave cavity structure is designed, which is cylindrical in shape. The microwave cavity has holes on both sides of the cylindrical cavity along the central axis for the action light of the rubidium atomic clock to pass through. The rubidium atomic gas chamber is embedded in the cavity. The basic structure is as follows: Figure 1 As shown, it is mainly composed of a rubidium atom gas chamber 1, a pole piece structure 2 and a cylindrical cavity 3;

[0035] A method for realizing a microwave cavity of a miniature rubidium atomic clock, wherein a cylindrical cavity 3 is made of metal material or made by printed circuit board technology, wherein the thickness and outer diameter of the cylindrical cavity 3 are determined according to the size requirements of the miniature atomic clock for the microwave cavity, and the inner diameter is the same as the outer diameter of a pole piece structure 2, and is used for installing the pole piece structure 2. When the cylindrical cavity 3 is made by printed circuit board technology, the inner ring thereof is realized by a through hole of the printed circuit board.

[0036] The rubidium atom gas chamber 1 is cylindrical and filled with alkali metal rubidium and inert buffer gas, wherein the inert buffer gas is a combination gas, including nitrogen, argon, neon, etc., and the gas component ratio and pressure are controlled to obtain a narrower discrimination spectrum line width and good temperature characteristics;

[0037] The pole piece structure 2 is manufactured by printed circuit board technology and is a multi-layer stacked structure. Figure 2As shown. The circuit board substrate is made of a material with a certain dielectric constant and is in the shape of a ring. The inner diameter of the ring is slightly larger than the outer diameter of the atomic gas chamber 1 to ensure that the atomic gas chamber can be installed inside the pole piece. The metal pole piece 2.3 is designed with a circular PCB conductor and is made of copper foil. The multiple sets of metal pole piece copper foil 2.3, the circuit board substrate 2.2 and the prepreg 2.5 are pressed together under high temperature and pressure through a pressing technology to form a multi-layer structure.

[0038] The thickness and number of each layer of the multilayer structure are determined based on the size of the atomic gas chamber, the resonant frequency of the microwave resonant cavity, the quality factor, and the size requirements of the microwave cavity for the micro-rubidium atomic clock. Usually, the length of the atomic gas chamber is the same as the thickness of the multilayer structure, and the smaller the thickness of each layer of the multilayer structure and the more layers, the better the performance of the microwave resonant cavity. According to the outer diameter of the atomic gas chamber, a through hole is made with the center of the ring of the metal pole piece 2.3 as the center of the circle for the installation of the atomic gas chamber;

[0039] A slot is designed on each layer of metal pole piece 2.3, namely a pole piece gap 2.1, and a metal through hole 2.4 is made on the metal pole piece 2.3 to connect the metal pole pieces of different layers to form an integrated resonant pole piece.

[0040] The circular metal pole piece 2.3, the pole piece gap 2.1 and the inner wall of the metal cylindrical cavity 3 form a resonance of mode TE011 under the joint action.

[0041] The cylindrical cavity 3 can be realized by using metal materials and mechanical processing technology, or it can be made by using printed circuit board technology. When the cylindrical cavity 3 is made by using printed circuit board technology, its inner ring is realized by the through hole of the printed circuit board. The metal pole piece copper foil is designed with multiple layers, and grooves are designed on each layer of metal pole piece 2.3 to form a pole piece gap 2.1, and conductive through holes 2.4 are made on the metal pole piece 2.3 to connect the metal pole pieces of different layers to form an integrated resonant pole piece.

[0042] The circular metal pole piece 2.3, the pole piece gap 2.1 and the inner wall of the metal cylindrical cavity 3 form a resonance of mode TE011 under the joint action.

[0043] The atomic gas chamber 1 is filled with alkali metal rubidium and inert buffer gas for generating magnetic resonance transition of rubidium atoms.

[0044] like Figure 3 As shown, an embodiment and simulation results of a micro rubidium atomic clock microwave cavity and its implementation method are as follows:

[0045] The cylindrical outer cavity is made of metal aluminum, with an outer wall radius of 4 mm, an inner wall radius of 3.45 mm, and a length of 5 mm.

[0046] The outer wall radius of the pole piece structure is 3.45mm, the inner wall radius is 2.8mm, and the length is 5mm. The pole piece structure adopts a 10-layer stacked structure design. Each layer of the circuit board substrate is laminated with single-sided copper foil. The distance from the inner edge of the circular copper foil to the inner edge of the circuit board substrate is the same as the distance from the outer edge of the circular copper foil to the outer edge of the circuit board substrate. The width of the ring is 0.25mm. The thickness of the circuit board substrate is 0.43mm, and the thickness of the copper foil is 0.07mm. 8 copper through-holes are evenly distributed on the metal copper foil ring, connecting the 10 layers of copper foil into a whole, such as Figure 4 As shown, the line connecting two adjacent through holes and the center of the circle is 45 degrees. Two symmetrical gaps are set on each layer of copper foil, and the line connecting the gap and the center of the circle is 22.5 degrees to the line connecting the adjacent through hole and the center of the circle.

[0047] The circuit board substrate is FR4 with a relative dielectric constant of 4.4.

[0048] The atomic gas chamber is cylindrical and made of glass, with a relative dielectric constant of 5.5, a radius of 2.8 mm and a length of 5 mm.

[0049] The above design is simulated by HFSS simulation software to obtain the resonance frequency of TE011 mode is 6836MHz, which is close to the magnetic resonance transition frequency of rubidium atoms and can be used for micro rubidium atomic clocks. The magnetic field line distribution is as follows: Figure 3 shown.

[0050] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A microwave resonant cavity of a miniature rubidium atomic clock, characterized in that: The microwave resonant cavity comprises a rubidium atom gas chamber, a pole piece and a cylindrical cavity; The rubidium atom gas chamber, the pole piece and the cylindrical cavity are all hollow cylinders; The rubidium atom gas chamber is installed in the pole piece, and the pole piece is installed in the cylindrical cavity; The pole piece and the side of the cylindrical cavity are both provided with holes for the passage of the action light of the rubidium atomic clock.

2. The microwave resonant cavity of a miniature rubidium atomic clock according to claim 1, characterized in that: The pole piece is made in the conductor layer of the multi-layer printed circuit board, and the pole pieces of different layers are connected by through holes.

3. The microwave resonant cavity of a miniature rubidium atomic clock according to claim 1, characterized in that: The space between the pole piece and the cylindrical cavity is filled with a circuit board.

4. The microwave resonant cavity of a micro rubidium atomic clock according to claim 3, characterized in that: The dielectric constant of the circuit board is selected according to actual needs. By selecting a board with a larger dielectric constant as the filling material, the distance between the pole piece and the cylindrical cavity or the thickness of the pole piece can be reduced, further reducing the size of the microwave cavity.

5. A method for realizing a microwave resonant cavity of a miniature rubidium atomic clock, characterized in that: The cylindrical cavity is made of metal material or printed circuit board technology; The thickness and outer diameter of the cylindrical cavity are determined according to the size requirements of the microwave cavity for the miniature atomic clock; The inner diameter of the cylindrical cavity is the same as the outer diameter of the pole piece; The cylindrical cavity is used to mount the pole piece.

6. The method for realizing a microwave resonant cavity of a miniature rubidium atomic clock according to claim 5, characterized in that: The rubidium atom gas chamber is cylindrical and filled with alkali metal rubidium and an inert buffer gas. The inert buffer gas is a combined gas, including nitrogen, argon and neon. The gas component ratio and pressure are controlled to obtain a narrower discrimination spectrum line width and good temperature characteristics.

7. The method for realizing a microwave resonant cavity of a miniature rubidium atomic clock according to claim 5, characterized in that: The pole piece structure is made by printed circuit board technology and is a multi-layer stacked structure; The circuit board substrate is made of a material with a certain dielectric constant and is in the shape of a ring. The inner diameter of the ring is slightly larger than the outer diameter of the rubidium atomic gas chamber to ensure that the rubidium atomic gas chamber can be installed inside the pole piece.

8. The method for realizing a microwave resonant cavity of a miniature rubidium atomic clock according to claim 7, characterized in that: The pole piece adopts a circular PCB conductor design and is made of copper foil. The copper foil, circuit board substrate and prepreg are pressed together under high temperature and pressure through pressing technology to form a multi-layer structure.

9. The method for realizing a microwave resonant cavity of a micro rubidium atomic clock according to claim 5, characterized in that: The thickness and number of each layer of the multilayer structure are determined based on the size of the rubidium atomic gas chamber, the resonant frequency of the microwave resonant cavity, the quality factor, and the size requirements of the microwave cavity for the micro-rubidium atomic clock; The length of the atomic gas chamber is the same as the thickness of the multilayer structure, and the smaller the thickness of each layer of the multilayer structure and the more layers there are, the better the performance of the microwave resonant cavity.

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