Quantum-based devices including gas cells

Abstract

In one example, the apparatus includes a substrate, antennas (1220, 1222) on the substrate, sealed containers (610A, 610B) enclosing a bipolar gas, waveguides (650A, 650B), and stubs (750A, 750B). The waveguides (650A, 650B) are communicatively coupled between the antennas (1220, 1222) and the sealed containers (610A, 610B). The waveguides (650A, 650B) are separated from the substrate by a gap. The stubs (750A, 750B) are adjacent to the waveguides (650A, 650B) and extend away from the gap.

Description

Technical Field

[0001] A gas cell (or physical cell) can include a sealed container that contains a gas. Depending on the pressure and temperature inside the container, the gas can be in a gaseous state or a vapor state. Gas cells can be useful in many applications, including as part of a chip-scale millimeter-wave atomic clock. The gas in the gas cell can include dipole molecules under relatively low pressure, and the pressure can be selected to provide a narrow signal absorption frequency dip that indicates the quantum rotational transition of the gas molecules detected at the output of the cavity. Electromagnetic (EM) signals can be emitted into and out of the cavity through an aperture in an electromagnetic permeable or substantially transparent cavity. By closed-loop control, the frequency of the signal can be dynamically adjusted to match the molecular quantum rotational transition. The frequency of the quantum rotational transition of the selected dipole molecules can be less variable due to the aging of the chip-scale millimeter-wave atomic clock and temperature or other environmental factors, so as a result, the system is useful for providing a highly accurate clock source with long-term stability. The overall performance of the system can be affected by various factors, such as EM leakage when the EM signal propagates into and out of the cavity.

Summary of the Invention

[0002] In one example, an apparatus includes a gas cell. The gas cell includes a gas cell cavity, an aperture, and a trench. The aperture extends between the gas cell cavity and the external surface of the gas cell enclosure. The first internal surface of the aperture is coated with a first electromagnetic (EM) reflective coating. The trench is on the periphery of the aperture and extends from the external surface. The second internal surface of the trench is coated with a second EM reflective coating.

[0003] In another example, an apparatus includes a substrate, an antenna on the substrate, a sealed container that encloses a bipolar gas, a waveguide, and a stub. The waveguide is communicatively coupled between the antenna and the sealed container. The waveguide is separated from the substrate by a gap. The stub is proximate to the waveguide and extends away from the gap. [Brief explanation of the drawing]

[0004] [Figure 1] This is a schematic diagram illustrating an example quantum transition frequency detector.

[0005] [Figure 2] Figure 1 is a schematic diagram illustrating the components of an example quantum transition frequency detector.

[0006] [Figure 3] This is a cross-sectional top view of one end of an example vial, which can be used as part of the detector shown in Figure 1.

[0007] [Figure 4] This graph shows examples of EM signal absorption by bipolar gases at different EM signal frequencies.

[0008] [Figure 5] Figure 1 is a schematic diagram showing perspective and external views of the example quantum frequency detector system.

[0009] [Figure 6] This is a schematic diagram illustrating the perspective and internal views of the detector system shown in Figure 5.

[0010] [Figure 7] Figure 5 is a schematic diagram showing an illustrative side view of the interface between the antenna and waveguide structure of the detector system.

[0011] [Figure 8] This is a schematic diagram showing a side view of the interface in Figure 7, including the example signal leakage reduction structure.

[0012] [Figure 9] Figure 8 is a schematic diagram illustrating an example of the operation of the signal leakage reduction structure.

[0013] [Figure 10] It is a schematic diagram showing a bird's-eye view of the detector system in FIG. 5.

[0014] [Figure 11] It is a schematic diagram showing a front view of the detector system in FIG. 5.

[0015] [Figure 12] It is a schematic diagram showing a perspective and perspective view of a part of the detector system in FIG. 5 including the signal leakage reduction structure in FIG. 8. [Figure 13] It is a schematic diagram showing a perspective and perspective view of a part of the detector system in FIG. 5 including the signal leakage reduction structure in FIG. 8.

[0016] [Figure 14] It is a schematic diagram showing a perspective and perspective view of a gas cell enclosure part including the signal leakage reduction structure in FIG. 8.

[0017] [Figure 15] It is a schematic diagram showing a perspective view including a circuit board that can be included in the detector system in FIG. 5.

[0018] [Figure 16] It is a schematic diagram showing a perspective view of a gas cell enclosure part including the signal leakage reduction structure in FIG. 8.

[0019] [Figure 17] It is a graph showing an exemplary variation of S parameters at the interface between the waveguide and the antenna of the quantum frequency detector system. [Figure 18] It is a graph showing an exemplary variation of S parameters at the interface between the waveguide and the antenna of the quantum frequency detector system. [Figure 19] It is a graph showing an exemplary variation of S parameters at the interface between the waveguide and the antenna of the quantum frequency detector system. [Figure 20]This graph shows an example of the variation in S-parameters at the interface between the waveguide and the antenna of a quantum frequency detector system.

[0020] In drawings, the same reference number or other reference symbol is used to indicate the same or similar features (functionally and / or structurally). Drawings are not necessarily drawn to a fixed scale. [Modes for carrying out the invention]

[0021] Figure 1 is a block diagram of an exemplary quantum transition frequency detector 100 that can be integrated to provide a clock with an accuracy of, for example, less than one second in several hundred years. In other examples, the frequency detector 100 is useful for creating a magnetic field sensor (magnetometer), an electric field sensor, or a pressure sensor. The detector 100 includes a container 102, or an assembly containing a plurality of such containers. The container 102 is a gas cell (or part thereof) sealed to contain a bipolar gas at a relatively low pressure, the exact pressure depending on the bipolar gas used, and other factors. In some examples, the pressure is lower than sea level atmospheric pressure. In some examples, the pressure is less than 1 / 100th of sea level atmospheric pressure. In some examples, the pressure is less than 1 / 10,000th of sea level atmospheric pressure. Suitable bipolar gases may include water vapor (H2O), acetonitrile (CH3CN), cyanoacetylene (HC3N), ammonia (NH3), carbonyl sulfide (OCS), hydrogen cyanide (HCN), and hydrogen sulfide (H2S). In some examples, the container 102 may be a glass (e.g., borosilicate glass) tube, as will be further explained with reference to Figure 2.

[0022] The container 102 (or each container in the assembly) can be coated on the outside with an electromagnetically reflective (e.g., conductive) material (e.g., metal), or the container 102 (or each container in the assembly) can be placed in an enclosure (e.g., enclosure 504 in Figure 5) made of or coated with an electromagnetically reflective material, and the outer wall of the container can be adjacent to (e.g., substantially in contact with) the electromagnetically reflective material of the enclosure. For example, the enclosure can be made of metal or metal-coated plastic. For example, the metallization of the container 102 or the enclosure can be carried out by sputtering or vapor deposition. A single container, or multiple containers assembled within an enclosure, can form a gas cell. Transmitter (TX) and receiver (RX) antennas (104, 106) are coupled to the container 102 at an electromagnetically transparent or substantially transparent window or access point at the end of the container, and each emits and receives millimeter-wave electromagnetic radiation into and from the container 102, and the millimeter-wave electromagnetic radiation propagates within the container 102.

[0023] Circuit elements 108 connected to antennas (104, 106) provide a closed loop capable of sweeping the frequency of millimeter-wavelength electromagnetic waves (e.g., approximately 20 GHz to approximately 400 GHz, e.g., approximately 70 GHz to approximately 180 GHz) radiated toward bipolar gas molecules confined within container 102. Absorption of quantum transitions of the bipolar gas molecules at specific frequencies is observable as a decrease in power transmitted between the transmitter and receiver, and specifically as a dip in the transmitted power at a specific frequency (or set of frequencies) within the sweep frequency range. By repeatedly locking onto the bottom of the dip, the quantum transition frequencies of the confined gas molecules are provided, and the transition frequencies can be made relatively stable with respect to aging of the sealed container, temperature, and other environmental factors. This stability allows the detector 100 to be used to create accurate quantum references and clocks whose accuracy does not substantially degrade due to device aging or changes in the operating environment. The circuit element 108 may include, for example, a voltage-controlled oscillator (VCO) or a digitally controlled oscillator (DCO) to generate millimeter waves at a specific frequency, and the frequency is adjusted until it matches a reference peak absorption frequency (frequency location of the transmit power dip).

[0024] Linear dipole molecules exhibit rotational quantum absorption at normal frequencies. As an example, OCS exhibits transitions approximately every 12.16 GHz. Therefore, gas cells such as those described herein can utilize any of the many available quantum transitions within the millimeter-wave frequency range. Circuit element 108 may further include a frequency divider that divides a matching frequency, which may be, for example, tens or hundreds of gigahertz, to a lower output clock frequency, such as about 100 MHz. The use of millimeter waves eliminates (or reduces) the need for a laser as a quantum transition exploration mechanism, reducing the cost and complexity of detector 100 compared to devices requiring a laser. Operation within these frequency ranges allows the transmitter and receiver antennas (104, 106) to be, for example, 10 millimeters, 5 millimeters, or less than 1 millimeter in length, depending on the quantum transition frequency of the selected dipolar gas. Each vessel 102 (or each vessel used in the vessel assembly) may be, for example, about 1 centimeter to about 20 centimeters in length, or about 2 centimeters to about 10 centimeters in length. Each container 102 (or each container used in the container assembly) may have a width and height of less than approximately 1 centimeter. If container 102 is formed in a tubular shape with a circular, elliptical, or rectangular cross-section, its diameter may also be less than approximately 1 centimeter. Since quantum absorption increases proportionally with container length, and longer container lengths provide clearer observed quantum transitions, the length of container 102 may be limited by manufacturing constraints and system package size constraints. Bent or meandering gas cells can provide longer effective container lengths within a more compact system package size by using bent (e.g., U-shaped) containers or by linking multiple containers together.

[0025] Figure 2 illustrates a quantum transition frequency detector 200, which may be an example of such a detector. The detector 200 includes a gas-filled container, which includes container portions 202 and 204, each containing a bipolar gas. In some examples, the container may also include a device 206. In some examples, device 206 may be another container portion containing a bipolar gas. Each of the container portions 202 and 204, and device 206, may include cavities. In some examples, the cavities may be coupled to form an extended U-shaped cavity. In some examples, each of the container portions 202 and 204, and device 206 (if it includes cavities), are sealed, and the cavities are physically sealed from each other. In some examples, device 206 may not contain a bipolar gas or may be solid and may be configured as a waveguide communicatively coupled between container portions 202 and 204. The EM signal can propagate from the transmitting circuit element 516 to the receiving circuit element 218 via the container portion 202, device 206, and container portion 204, as shown by the dotted line 219.

[0026] The gas container portions 202 and 204 and the device 206 are enclosed within a container enclosure 208. The container enclosure 208 is mechanically coupled to a substrate such as a printed circuit board (PCB), or to a package substrate 214 of an integrated circuit on which the circuit elements, including the transmitting circuit element 216 and the receiving circuit element 518, are arranged.

[0027] The container enclosure 208 also has cavities that form (or house) a plurality of signal couplers 220, 222. Signal coupler 220 is coupled between container portion 202 and a first antenna (e.g., TX antenna 104, not shown in Figure 2), and signal coupler 222 is coupled between container portion 204 and a second antenna (e.g., RX antenna 106, not shown in Figure 2). Signal couplers 220 and 222 are each configured as waveguides and capable of supporting vertical emission, so that the EM signal travels vertically (e.g., along the z-axis) between the first antenna and container portion 202, and between the second antenna and container portion 204. In some examples, signal couplers 220, 222 are each hollow cavities whose interiors are lined with an electromagnetically reflective material (e.g., metallized), with electromagnetically transparent or substantially transparent window regions at their top and bottom. In some examples, signal couplers 220 and 222 may each incorporate a solid dielectric material (e.g., plastic) enclosed within an electromagnetically reflective material (e.g., metallized), with electromagnetically transparent or substantially transparent window regions positioned at their top and bottom. In some examples, signal couplers 220 and 222 may also have a solid / hollow configuration using the same material as device 206. Regardless of whether a hollow or solid configuration is used, or a combination thereof, signal couplers 220 and 222 can function as waveguides by guiding the propagation of EM signals through them. First and second antennas (not shown in Figure 2) are communicatively coupled to signal couplers 220 and 222 via interfaces 230 and 232, respectively, of the container enclosure 208.

[0028] Figure 3 illustrates Figure 300 of one end of a container portion 202 (or 204). In this example, the container portion 202 may be in the form of a vial. The end of the illustrated container portion 204 is obtuse or flat and has an outer surface 306 and an inner surface 308. In the example shown in Figure 3, the outer surface 306 and the inner surface 308 are flat. In some other examples, the outer surface 306 may be concave and the inner surface 308 may be convex. The end of the illustrated container portion 202 also has a window region 310 or is located near a window region 310, which typically represents an electromagnetically translucent or substantially transparent access point that can be used for discharging into or receiving from the container portion 202. As will be further described herein with reference to Figures 1 and 2, in some examples the window region 310 may correspond to an opening in an external metal coating applied directly to the vial 302. In some examples, the window region 310 may correspond to an opening in an electromagnetically reflective material (e.g., metallized) coating applied to the inner surface of the enclosure in which the container portion 202 is placed, and when the container portion 202 is installed in the enclosure, the metal is adjacent (e.g., substantially touching) to the outside of the glass wall of the container portion 202, and the window region 310 is located near the illustrated end of the vial 302.

[0029] Figure 4 is a graph 400 showing an example of the absorption of an EM signal by a bipolar gas in a gas cell such as container 102, against the frequency of the EM signal. Absorption is reflected, for example, in the quantum transition frequency detector illustrated in Figure 1, as a function of the transmission frequency, by the ratio of the power received by the RX antenna 106 to the power output by the TX antenna 104 (i.e., P-out / P-in).

[0030] As explained in Figure 1, a millimeter-wavelength EM signal is transmitted from the TX antenna 104 to the dipole gas-filled container 102, and the EM signal propagates within the container 102 to the RX antenna 106. When the frequency of the EM signal is swept, a decrease in power transmitted between the transmitter and receiver can be observed at a specific frequency (or set of frequencies) within the sweep frequency range, specifically as a dip in the transmitted power at a particular frequency (or set of frequencies) where quantum transitions of the dipole gas molecules occur. Referring to Graph 400, a dip in the transmitted power from 100% to 94% can be observed at 121.6 GHz, which can be identified as the quantum transition frequency. The bandwidth of this dip is approximately 1 MHz.

[0031] Figure 5 is a perspective view of an exemplary quantum frequency detector system 500, which may be an example of detectors 100 and 200 in Figures 1 and 2. In this example, the detector system 500 includes a gas cell enclosure 504 that can be mounted on a larger substrate 506 belonging to a larger system. The enclosure 504 may be attached to the substrate 506 by pins or screws (or other fastening devices) 510, or it may be bonded to the substrate. The substrate 506 may be, for example, about 5 mm in length and about 5 mm in width (these are the dimensions shown in the overhead view of Figure 8). The circuit elements 508 may include various integrated circuit components, for example, antennas 104 and 106 in Figure 1. As is more clearly shown in Figure 8, a portion of the circuit elements 508, which may be a packaged integrated circuit, may be formed on or within a package substrate coupled to the substrate 506, and at least a portion of the circuit elements 508 is positioned between the substrate 506 and the enclosure 504.

[0032] Figure 6 is a transparent and transmission view of the detector system 500 of Figure 5, showing the gas cell enclosure 504 transparently and illustrating the features of a specific internal gas cell, including vessels 610A, 610B and signal couplers / waveguides 650A, 650B enclosed within the internal gas cell cavity 620. In this example, vessels 610A, 610B are parallel to each other, arranged along the same plane within the enclosure 504, and aligned parallel to the Y-axis at their respective positions within the cavity 620. Vessels 610A, 610B may be bipolar gas-filled vessels 102 as described with reference to Figure 1. Waveguides 650A, 650B are examples of signal couplers 220 and 222 in Figure 2.

[0033] Each of the containers 610A and 610B can be enclosed in an electromagnetically reflective material by either covering the outside of each container with an electromagnetically reflective (e.g., conductive) material (e.g., metal) or by making or covering the cavity 620 within the enclosure 504 with an electromagnetically reflective material. For example, the metallization of the cavity 620 can be carried out by sputtering or deposition. The cavity 620 may include an interconnection 625 between containers 610A and 610B, which can act as a waveguide by guiding EM signals from container 610A to 610B or vice versa. In this example, the containers 610A and 610B and the cavity 620 collectively form at least a part of a gas cell.

[0034] As more clearly shown in Figures 7-9 and 12-14, each waveguide 650A, 650B may include an opening extending between the gas cell cavity 620 and the outer surface of the gas cell enclosure 504 that interfaces with the PCB 506. The opening may be hollow / void (e.g., filled with air) or filled with solid dielectric material, as previously described. Each waveguide 650A, 650B may be aligned parallel to the Z-axis and located between their respective containers 610A, 610B and the circuit element 508. The inner surfaces of each waveguide 650A, 650B may be made of or covered with an electromagnetically reflective surface to guide the EM signal by restricting the transmission of the EM signal (e.g., in the direction parallel to the z-axis). For example, waveguide 650A can lead the EM signal from TX antenna 104 (e.g., contained within or coupled to circuit element 508) to container 610A, and waveguide 650B can lead the EM signal from container 610B to RX antenna 106 (e.g., contained within or coupled to circuit element 508). In this context, waveguide 650A can be considered to be communicatively coupled to TX antenna 104 and container 610A, and waveguide 650B can be considered to be communicatively coupled to container 610B and RX antenna 106. In some examples, each waveguide 650A, 650B is a hollow pipe with its inner surface covered with an electromagnetically reflective material. In some examples, each waveguide 650A, 650B is a solid dielectric pipe surrounded along its length with an electromagnetically reflective material, as described above.

[0035] Figure 7 is a side view showing part of the detector system 502, its specific features 504, 506, 508, and 510. Figure 7 shows that the waveguide 650A is located between the cavity 620 and the circuit element 508, aligned parallel to the Z-axis, and positioned near one end of the container 610A enclosed within the cavity 620 of the enclosure 504.

[0036] To improve the accuracy of determining the quantum transition frequency, it may be advantageous for the EM signal transmitted from circuit element 508 (e.g., via antenna 104) to containers 610A and 610B to be as strong as possible. Higher power can increase the absorption of the EM signal (and dips shown in Figure 4) by the dipole gas sealed within containers 610A and 610B. Such an arrangement can increase the signal-to-noise (SNR) ratio by reducing the likelihood of noise that could cause false dip detection, i.e., dip detection that is not actually caused by the absorption of the EM signal. It is also advantageous to reduce potential interference / coupling between the transmitted signal (e.g., in waveguide 650A) and the received signal (e.g., in waveguide 650B).

[0037] Certain features of the circuit elements 508 arranged on the substrate 506 (e.g., antennas 104, 106 in Figure 1 or antennas 1220, 1222 in Figure 12) and the interfaces between them and waveguides 650A, 650B of the enclosure 504 can significantly affect the power of the EM signal transmitted to and received from container 610A. For example, an increase in the air gap at the interface between opposing surfaces of the substrate 506 (including the circuit elements 508) and the enclosure 504 (including the openings and edges of waveguides 650A, 650B) can contribute to signal leakage when the transmitted signal propagates from TX antenna 104 to waveguide 650A and when the received signal propagates from waveguide 650B to RX antenna 106. Signal leakage can contribute to power loss.

[0038] Furthermore, stray transmission of the EM signal within the substrate 506, enclosure 504, or the air gap between them can also contribute to power loss. One example of stray transmission, referred to herein as "crosstalk," is when a portion of the EM signal travels directly from the transmitter (e.g., TX104 in Figure 1 or TX antenna 1220 in Figure 12) to the receiver (e.g., RX antenna 106 in Figure 1 or RX antenna 1222 in Figure 12), in contrast to the EM signal traveling from the transmitter to the receiver via the gas cell.

[0039] As will be further described herein with reference to the following figures, the quantum transition frequency detector may include a leakage signal reduction structure near the interface between waveguide 650A / 650B and each antenna to reduce signal leakage at the interface. The leakage signal reduction structure may include, for example, one or more trenches adjacent to and / or surrounding the waveguide. The trenches are configured as quarter-wavelength stubs and are located away from the waveguide. Leakage signals propagating from the waveguide into the air gap may propagate into the trench and become incident leakage signals. Incident leakage signals may be reflected on the inner surface of the trench. The depth of the trench may be configured to introduce a 180-degree phase shift in the reflected leakage signal so that the reflected leakage signal can destructively interfere with the incident leakage signal. The position of the trench may be positioned so that the reflected leakage signal constructively interferes with the signal in the waveguide as it propagates back into the waveguide, thereby further improving the power of the signals propagating in and out of the waveguide.

[0040] Furthermore, the package substrate of the circuit element 508 may include an electronic bandgap structure, and a portion of the package substrate between adjacent electronic bandgap structures can act as a quarter-wavelength stub, generating phase-shifted reflected leakage signals and reducing leakage signals through destructive interference. Due to the destructive interference, the power of the leakage signal in the air gap can be significantly reduced, thereby preventing crosstalk and increasing the power transmitted to the container 610A via waveguide 650A and increasing the power received from the container 610B via waveguide 650B.

[0041] Figure 8 is a simplified cross-sectional view of a portion of the detector system 502, including the leakage signal reduction structure. This cross-section is taken parallel to the X-axis, passing through the enclosure 504, the container 610A, the cavity 620, the waveguide 650A, the trench 750A (which covers the waveguide 650A), and a portion of the circuit element 508, including the package substrate 752 containing the electron bandgap (EBG) structure 754 on the substrate 506. Each EBG may include metal vias passing through the package substrate 752. The illustrated portion of the circuit element 508 on the substrate 506 faces the opening of the waveguide 650A (at the outer edge of the enclosure 504) and also faces the opposing external surface 850 of the enclosure 504 surrounding the opening of the waveguide 650A. In Figure 8, the trench 750A is shown as part of the enclosure 504. In some other examples, trench 750A can be located outside enclosure 504. For example, trench 750A can be part of a standalone waveguide structure that interfaces between container 610A (which may be surrounded by enclosure 504) and circuit element 508. In some examples, the package substrate of circuit element 508 can be part of a launch-on package, and the antenna of circuit element 508 can be an E-patch antenna.

[0042] Figure 8 shows one representation of the electromagnetic reflective materials 802 and 803 on at least the inner surfaces of waveguide 650A and trench 750A, respectively. In some examples where enclosure 504 is made primarily of non-metallic material (e.g., plastic), the electromagnetic reflective materials 802 and 803 may be metallic coatings applied to their surfaces (e.g., by sputtering or deposition) or to all exposed outer surfaces of enclosure 504 (e.g., including those surfaces indicated by surfaces 802 and 803). In some examples where enclosure 504 is made primarily of metallic material, the electromagnetic reflective materials 802 and 803 may simply represent the external metallic surfaces of enclosure 504.

[0043] Figure 8 also shows exemplary dimensions 804, 806, 808, 810, and 812 that can be used in one example. In this example, dimension 804 indicates a trench wall thickness of approximately 300 μm along a line parallel to the Y-axis, extending between the inner surface of trench 750A and the inner surface of waveguide 650A. Dimension 806 indicates a trench width of approximately 300 μm between opposing inner surfaces of trench 750A along a line parallel to the Y-axis. Dimension 808 indicates a trench depth of approximately 610 μm extending from the trench opening on the outer surface of trench 750A along a line parallel to the Z-axis. The trench depth can be an odd multiple of a quarter wavelength of the EM signal in the trench. Furthermore, dimension 810 indicates that the air gap at the interface between the enclosure 504 and the opposing surfaces of the circuit element 508 is approximately 100 μm (for example, between antennas 1220, 1222 and the respective openings of waveguides 650A and 650B in Figure 12). Dimension 812 indicates the thickness of the substrate contained within the circuit element 508 and having an electromagnetic bandgap structure (EBG), as will be further described herein with reference to Figures 12, 13, and 15. The substrate thickness dimension 812 may also be configured as an odd multiple of a quarter wavelength of the EM signal in the substrate, which may cause a specific impedance effect on the EM signal in the substrate, as will be further described herein with reference to Figure 12. Figure 8 shows the dimensions of a particular example, but any suitable dimensions can be used. Waveguides 650B and trench 750B may be arranged similarly to those shown for waveguides 650A and trench 750A in Figure 8.

[0044] The amount of air gap (indicated as dimension 810) at the interface between the opposing surfaces of the enclosure 504 and the circuit element 508 is variable and can be caused by any of a number of factors, such as mechanical tolerances. A significant air gap at that same interface can lead to losses in energy transmission and may cause undesirable crosstalk problems between adjacent TX and RX antennas (e.g., between antennas 104 and 106 in Figure 1, or between antennas 1220 and 1222 in Figure 12). Trenches 750A and 750B can be configured to minimize the adverse effects of a variable air gap (indicated as dimension 810) at the interface between the opposing surfaces of the enclosure 504 and the circuit element 508. In some examples, trenches 750A and 750B can be used in combination with EBGs, as further described herein with reference to EBGs 1210A and 1210B in Figure 12.

[0045] Specifically, each of the trenches 750A and 750B, and the portion of the package substrate 752 between adjacent EBGs (e.g., package substrate portion 752A), are configured as quarter-wavelength stubs. Leakage signals propagating into the trenches / package substrate as incident signals can be reflected and propagated back into the air gap. The trenches / package substrate can introduce a 180-degree phase shift between the incident and reflected signals in the air gap directly below or above the trenches 750A / 750B or package substrate portion 752A, causing destructive interference that prevents leakage signals from propagating outward from the waveguide through the air gap, or at least reduces the power of such leakage signals. Alternatively, the trenches can be positioned away from the waveguide so that when reflected signals propagate back into the waveguide, the phase shift between the reflected signals and the signals in the waveguide becomes a multiple of 360 degrees, allowing the reflected signals to constructively interfere with the signals in the waveguide and increase the power of the signals in the waveguide. This configuration can improve the power of signals transmitted to and from the waveguide.

[0046] Figure 9 shows exemplary leakage signal reduction achieved at least partially by trenches 750A, 750B and package substrate 752 containing EBG. In some examples, to optimize constructive and destructive interference caused by trenches 750A, 750B, each trench 760A, 750B may have a depth 908 which is an odd multiple of λ1 / 4, where λ1 represents the wavelength of an EM signal such as that transmitted through the trench. Package substrate 752 may also have a thickness 909 which is an odd multiple of λ2 / 4, where λ2 represents the wavelength of an EM signal such as that transmitted through the package substrate. The depth 908 can be defined as the distance between the base surface 915 of trenches 750A, 750B and the opposing openings 919 of trenches 750A, 750B at the edge of enclosure 504. Dimension 910 indicates the distance between one of the central axes 912 of waveguides 650A and 650B and the corresponding central axis 914 of trenches 750A and 750B. Dimension 910 can similarly be an odd multiple of λ / 4. The width of trenches 750A and 750B (dimension 806 in Figure 8) can be λ / 8. Trenches 750A and 750B may be substantially similar to each other in terms of material.

[0047] As shown in Figure 9, a portion of the EM signal traveling through the air along path 918 (in the air gap between enclosure 504 and substrate 506) may enter the base surface 915 through opening 919. If dimensions 908 and 910 are both λ / 4, the distance the EM signal travels to reach the base surface 915 can be expressed as 2 × λ / 4 = λ / 2. Similarly, the path returning towards the central axis 912 of waveguide 650A can also be expressed as 2 × λ / 4 = λ / 2. Therefore, the EM signal reflected along path 916 at opening 919 of trench 750A is in phase (i.e., 2 × λ / 2) with the incident EM signal reaching the same base of trench 750A along path 918. This can consequently cause constructive interference of the EM signal, contributing to maximizing the power of the EM signal transmitted to container 610A via waveguide 650A. Such an arrangement of trench 750A also results in the creation of high-impedance points that reduce the transmission of EM signals beyond trench 750A (e.g., beyond base 915 along the Z-axis and beyond the sidewall of trench 750B). On the other hand, the phase difference between the incident EM signal and the reflected EM signal at aperture 919 can be 2 × λ / 4 = λ / 2, so they may be phase-shifted and destructively interfere with each other. Similarly, the EM signal may propagate from location 911 in the air gap to the package substrate, be guided by the EBG, and reflected at the bottom surface of the package substrate, and the reflected EM signal and the incident signal at location 911 may also be phase-shifted and destructively interfere with each other. Therefore, leakage signals propagating outward away from the trenches and waveguides may be attenuated or eliminated.

[0048] Figure 10 is a top view showing certain features 504, 506, 508, 510, 610A, 610B, and 620 of the detector system 502, in which waveguides 650A and 650B are at least partially obscured by the respective ends of containers 610A and 610B.

[0049] Figure 11 is a front view showing certain features 504, 506, 508, 510, 610A, 610B, 620, and 650 of the detector system 502. Figure 11 shows waveguide 650A having a trench 750A extending around the periphery of waveguide 650A, and waveguide 650B having a trench 750B extending around the periphery of waveguide 650B.

[0050] Figure 12 is an enlarged perspective view of a portion of the detector system 502, including the enclosure 504, the substrate 506, the circuit element 508, the containers 610A and 610B, the cavity 620, the waveguides 650A and 650B, and the trenches 750A and 750B. Figure 12 also shows EBGs 1210A and 1210B, which can be part of the package substrate 752 of the circuit element 508, and are positioned around the periphery of the TX and RX antennas 1220 and 1222, respectively. The TX and RX antennas 1220 and 1222 may be similar in terms of material to the TX and RX antennas 104 and 106 in Figure 1, respectively. The arrangement shown in Figure 12 can provide near-field coupling between the TX antenna 1220 and waveguide 650A, and between the RX antenna 1222 and waveguide 650B.

[0051] As more clearly shown in Figure 15, each EBG 1210A, 1210B may include an array of metal vias extending completely through the substrate portion of the circuit element 508 (indicated by the thickness dimension 812 in Figure 8). The metal vias of each EBG 1210A, 1210B may be formed, for example, using laser-induced deep etching (LIDE). Once formed, each via is at least partially filled, or otherwise its interior is covered with one or more layers of material. The material may be selected, for example, to improve the electromagnetic field (EMF) rejection achieved by EBG 1210A, 1210B. Each metal via may be cylindrical and have a diameter of approximately 50 micrometers, but any suitable shape and width may be used. Each metal via of EBG 1210A, 1210B may be electrically connected to a ground terminal, and each metal via may be capacitively coupled to at least one other adjacent metal via. Each metal via can be configured as a resonator having a resonant frequency based on the frequency of the EM signal in the substrate.

[0052] In some examples, the metal vias of EBG 1210A and 1210B may each have a thickness corresponding to the substrate thickness dimension 812 in Figure 8, in which case each metal via has a length corresponding to an odd multiple of the wavelength of the EM signal in the substrate.

[0053] In some examples, the metal vias of EBG 1210A and 1210B are spaced apart by a distance of λ' / 4, where λ' is the wavelength of the EM signal transmitted in the solid dielectric material of the substrate 506 in the volume between the metal vias of EBG 1210A and 1210B. In some examples, spacing the metal vias by a distance of λ' / 4 may increase the destructive interference of EMF propagation across the volume defined by EBG 1210A and 1210B. In some examples, the metal vias of EBG 1210A and 1210B are spaced apart by a distance of λ / 4, where λ represents the wavelength of the EM signal transmitted through air (e.g., across the air gap between the enclosure 504 and the circuit 508 on the substrate 506). Such alternative spacings (according to λ / 4) can similarly increase the destructive interference of EMF propagation across the volume defined by EBG 1210A and 1210B.

[0054] As described above, the metal vias of EBG 1210A and 1210B can be collectively configured to create a high-impedance path that reduces lateral crosstalk transmission of EMF between antennas 1220 and 1222 (e.g., parallel to the X-axis and along the substrate 506) by introducing destructive interference, for example. Such crosstalk transmission may reduce the power of the EM signal transmitted within the gas cell enclosure 504 (e.g., within waveguides 650A and 650, cavity 620, and containers 610A and 610B).

[0055] Figure 13 is an enlarged perspective view of a portion of the detector system 502, showing only a portion of the enclosure 504, along with the substrate 506, circuit element 508, container 610B, cavity 620, waveguide 650B, and corresponding portions of trench 750B. The illustrated portion of circuit element 508 includes EBG 1210B positioned around the periphery of the RX antenna 1222. In this example, trench 750B has a rectangular annular shape with rounded corners, forming a continuous gap that extends to the edge of the enclosure 504 around the periphery of waveguide 650B. By using rounded corners as opposed to right angles, for example, trenches 750A and 750B have a more uniform width dimension along their entire length, including their corners. Trenches 750A and 750B having more uniform dimensions along their entire length may result in trenches that have a more uniform effect on EM signals along their entire length. However, trenches 750A and 750B may have any suitable shape that provides the specific constructive and destructive interference characteristics described herein. Although not shown in Figure 13, trench 750A may be positioned substantially similarly to trench 750B with respect to waveguide 650A.

[0056] Figure 14 is a magnified perspective view of only a portion of the enclosure 504 that can be used for the detector system 502. Figure 14 shows the cavity 620, which is not enclosed within the vessel 610B. By omitting the illustrated portion of the enclosure 504 and all other features of the vessel 610B and the detector system 502, the exemplary arrangement of the trench 750B relative to the waveguide 650B, and the opening at the edge of the enclosure 540 defined by the trench 750B are more clearly shown.

[0057] Figure 15 is an enlarged perspective view of a portion of the circuit element 508, including an EBG 1210B which can be positioned around the periphery of the RX antenna 1222. A similar EBG 1210A can be positioned around the periphery of the TX antenna 1220, as shown in Figure 12. Figure 15 also more clearly shows the RX antenna 1222, which will be further described herein with reference to Figure 13.

[0058] Figure 16 is a perspective view of a portion of enclosure 504, rotated (relative to Figure 14, for example) to show the external surface 1610 of enclosure 504, and enclosure 504 includes openings extending through it, corresponding to waveguide 650B and trench 750B. Another opening corresponding to cavity 620 is also shown.

[0059] In this example, trench 750B is a rounded rectangular annular shape located around the periphery of waveguide 650. While Figure 15 shows trench 750B as having a continuous rectangular annular shape, in some examples multiple unconnected trenches or stubs may be collectively located around the periphery of waveguide 650B, and similar unconnected trenches or stubs may be similarly located around the periphery of waveguide 650A.

[0060] As will be further described herein with reference to Figures 8 and 9, in some examples the trench 750B may have a depth dimension 808 which is an odd multiple of λ / 4, and the distance between the central axis 912 of waveguide 650B and the central axis 914 of trench (indicated by dimension 910) may also be an odd multiple of λ / 4. In some examples the distance between the central axis 912 of waveguide 650B and the central axis 914 of trench 750B (indicated by dimension 910) may be based on an odd multiple of the wavelength λ of a given EM signal (such as one transmitted through air) and the depth dimension 808 of trench 750B through which the EM signal is transmitted across the air gap between surface 1610 and the opposing surfaces of the circuit element 508 on substrate 506.

[0061] Figure 17 is graph 1700 showing the s-parameters of the waveguide-antenna interface resulting from the virtually gapless interface between antennas 1220, 1222 and the respective apertures of waveguides 650A, 650B. Data plot 1702 shows that the majority of the energy (i.e., -1 dB) at the target frequency (e.g., indicated by point 1703 at approximately 121.6 GHz) is successfully transmitted from TX antenna 1220 through waveguide 650A to containers 610A, 610B in gas cell enclosure 504. Data plots 1704 and 1706 show that a relatively small proportion of the energy is reflected under the same gapless conditions, where plot 1706 shows the reflection at TX antenna 1220 and plot 1704 shows the reflection at RX antenna 1222. In plot 1704, the peak reflectance at point 1705 is approximately -12 dB, and in plot 1706, the peak reflectance at point 1707 is approximately -19 dB.

[0062] Figure 18 is graph 1800, showing the interface s-parameters resulting from a 100 μm gap and the absence of trenches 750A, 750B or EBG features 1210A, 1210B at the interface between antennas 1220, 1222 and the respective apertures of waveguides 650A, 650B. Data plot 1802 shows that the portion of the transmitted power is -4.2 dB at the target frequency (e.g., shown at point 1803 at approximately 121.6 GHz). The transmitted power at the target frequency at point 1803 is less than the transmitted power at the same target frequency at point 1703 in data plot 1702. This difference in transmitted power is at least in part due to the 100 μm air gap and the absence of trenches 750A, 750B at the air gap interface between antennas 1220, 1222 and the apertures of enclosure 504 corresponding to waveguides 650A, 650B. Data plots 1804 and 1806 show that a larger proportion of the energy is reflected under a 100 μm air gap compared to data plots 1704 and 1706, where plot 1806 shows the reflection at TX1220 and plot 1804 shows the reflection at RX antenna 1222.

[0063] Figure 19 is graph 1900, showing the s-parameters of the interface obtained by using trenches 750A, 750B and EBG 1210A, 1210B in combination. These features collectively act to at least partially counteract the effect of the 100 μm air gap at the interface between antennas 1220, 1222 and the respective openings of waveguides 650A, 650B. In this example, the data shown in graph 1900 represents enclosure 504 including trenches 750A, 750B, each having a depth of approximately 610 μm (dimension 808 in Figure 8), a trench width of approximately 300 μm (dimension 806 in Figure 8), and a wall thickness of approximately 300 μm (dimension 804 in Figure 8).

[0064] Data plot 1902 shows that the majority of the energy at the target frequency (e.g., approximately 121.6 GHz, indicated at point 1803) (i.e., -2.0 dB) is successfully transmitted from the TX antenna 1220 through waveguide 650A to containers 610A and 610B within the gas cell enclosure 504. Data plots 1904 and 1906 show that a relatively small proportion of the energy is reflected under the same 100 μm gap conditions, where plot 1906 shows the reflection at the TX antenna 1220 and plot 1904 shows the reflection at the RX antenna 1222. In plot 1904, the portion of energy reflected back to the gas cell at point 1905 is approximately -12 dB, and in plot 1906, the portion of energy reflected back to the TX antenna 1220 at point 1907 is approximately -32 dB. Points 1905 and 1907 show a reduction in EM signal reflection for the corresponding points 1705 and 1707 in Figure 17. Data plot 1902 shows that using trenches 750A and 750B in combination with EBGs 1210A and 1210B can result in an increase in the portion of power successfully transmitted to vessels 610A and 610B via waveguide 650A and TX antenna 1220, which includes reducing certain reflections that can attenuate the transmitted power.

[0065] Figure 20 is a graph 2000 of s-parameters showing a comparison between the crosstalk between antennas 1220 and 1222 (plot 2002) arising from an exemplary detector system 502 having both trenches 750A, 750B and EBGs 1210A, 1210B, and the crosstalk between the TX and RX antennas of an alternative detector that is otherwise identical but does not have trenches or electromagnetic bandgap structures (plot 2004). In this example, the data shown in plot 2002 represents an enclosure 504 containing trenches materially similar to trenches 750A and 750B, each trench having a depth of approximately 610 μm (dimension 808 in Figure 8), a trench width of approximately 300 μm (dimension 806 in Figure 8), and a wall thickness of approximately 300 μm (dimension 804 in Figure 8). EBG 1210A and 1210B are examples of devices that can exhibit the effects shown in plot 2002. This comparison shows that for detector system 502, including trenches 750A and 750B and EBG 1210A and 1210B, the transmit power at approximately 30 dB is improved at approximately 121.6 GHz compared to a detector that lacks such features but is otherwise identical.

[0066] In some examples, a second trench may be located near the periphery of a first trench. For example, trenches 750A and 750B may each have a rounded rectangular annular trench located near their periphery. Also, in some examples, a third trench may be located near the periphery of a second trench.

[0067] In this specification, “or” is inclusive and non-exclusive unless explicitly indicated otherwise or by context. Thus, in this specification, “A or B” means “A, B, or both” unless explicitly indicated otherwise or by context. Also, “and” means both jointly and each of them unless explicitly indicated otherwise or by context. Thus, in this specification, “A and B” means “A and B, jointly or each of them” unless explicitly indicated otherwise or by context. To assist readers of the Patent Office and any patents issued pursuant to this application in interpreting the claims attached to this application, the applicant should note that, unless explicitly used in the language of the claims, the phrases “means for” or “processes for” are not intended to evoke Section 112(f) of the United States Patent Act as of the filing date of this application.

[0068] In this specification, the term “coupled” may encompass connections, communications, or signaling paths that enable a functional relationship consistent with this specification. For example, if device A generates a signal to control device B to perform a certain operation, then (a) in the first example, device A is coupled to device B by a direct connection, or (b) in the second example, device A is coupled to device B via an intermediary component C, provided that the intermediary component C does not alter the functional relationship between device A and device B, so that device B is controlled by device A via a control signal generated by device A.

[0069] Furthermore, in this specification, the phrase "based on ~" means "based at least partially on ~". Therefore, if X is based on Y, X can be a function of Y and any number of other factors.

[0070] A device “configured” to perform a certain task or function may be configured by the manufacturer at the time of manufacture to perform that function (e.g., by programming and / or by wired connection), and / or may be configured (or reconfigurable) by the user after manufacture to perform that function and / or other additional or alternative functions. Such configurations may be achieved through the device’s firmware and / or software programming, through the construction and / or layout of the device’s hardware components and interconnections, or through a combination thereof.

[0071] As used herein, the terms “terminal,” “node,” “interconnection,” “pin,” and “lead” are interchangeable. Unless otherwise specified, these terms are generally used to mean the interconnection or termination between device elements, circuit elements, integrated circuits, devices, or other electronic or semiconductor components.

[0072] A circuit or device described herein as including certain components may instead be adapted to be coupled to those components in order to form the circuit element or device described. For example, a structure described as including one or more semiconductor elements (such as transistors), one or more passive elements (such as resistors, capacitors, and / or inductors), and / or one or more power sources (such as voltage sources and / or current sources) may instead include only the semiconductor elements within a single physical device (e.g., a semiconductor die and / or integrated circuit (IC) package), and may also be adapted, for example, by an end user and / or a third party, either during or after manufacturing, to be coupled to at least some of the passive elements and / or power sources in order to form the structure described.

[0073] The circuits described herein are reconfigurable to include additional or different components in order to provide functionality that is at least partially similar to the functionality available prior to the replacement of components. Unless otherwise stated, components indicated as resistors generally represent any one or more elements connected in series and / or parallel to provide the impedance amount represented by the indicated resistors. For example, a resistor or capacitor is shown and described herein as a single component, but instead, each may be multiple resistors or capacitors connected in parallel between the same nodes. For example, a resistor or capacitor is shown and described herein as a single component, but instead, each may be multiple resistors or capacitors connected in series between the same two nodes as a single resistor or capacitor.

[0074] While certain elements in the described examples may be included in the integrated circuit and other elements may exist outside the integrated circuit, additional or fewer features may be incorporated into the integrated circuit in other examples. Also, some or all of the features illustrated as being outside the integrated circuit may be included in the integrated circuit, and / or some of the features illustrated as being inside the integrated circuit may be incorporated outside the integrated circuit. As used herein, the term “integrated circuit” means one or more circuits that are (1) incorporated in / on a semiconductor substrate, (2) incorporated in a single semiconductor package, (3) incorporated in the same module, and / or (4) incorporated in / on the same printed circuit board.

[0075] In this document, unless otherwise stated, “approximately,” “about,” or “substantially” preceding a parameter means that it is within ±10% of that parameter, or, if the parameter is zero, within a reasonable range of values ​​near zero.

[0076] The preceding description provides many specific details in one or more examples for illustrative purposes. However, as will be obvious to those skilled in the art, this description can be implemented without some or all of these specific details. In other cases, well-known processes or structures are not described in detail so as not to unnecessarily obscure this description. Also, although this description is written in relation to several examples, this description is not limited to the examples described. On the contrary, this description covers substitutes, modifications, and equivalents that may fall within the spirit and scope of this description as defined by the appended claims. Modifications are possible in the described embodiments within the claims, and other embodiments are also possible.

Claims

1. It is a device, Includes a gas cell enclosure, The aforementioned gas cell enclosure, It includes a gas cell cavity, an opening, and a trench. The opening extends between the gas cell cavity and the outer surface of the gas cell enclosure, and the first inner surface of the opening is covered with a first electromagnetic (EM) reflective coating. The trench is located on the periphery of the opening and extends from the outer surface, and the second inner surface of the trench is covered with a second EM reflective coating. Device.

2. The apparatus according to claim 1, The substrate facing the aforementioned external surface, The antenna on the substrate facing the opening, The antenna is configured to transmit signals, The depth of the trench from the opening is based on an odd multiple of the wavelength of the signal in the trench. Device.

3. The apparatus according to claim 1, wherein the trench surrounds the opening.

4. The apparatus according to claim 3, wherein the trench has rounded corners or a circular footprint.

5. The apparatus according to claim 2, wherein the outer surface is separated from the substrate by a gap, The aforementioned wavelength is the first wavelength, The distance between the trench and the opening is an odd multiple of the second wavelength of the signal in the gap, and is based on the depth of the trench. Device.

6. The apparatus according to claim 2, wherein the wavelength is a first wavelength, and the thickness of the substrate is based on an odd multiple of the second wavelength of the signal in the substrate. Device.

7. The apparatus according to claim 2, wherein the substrate includes an array of metal vias configured as a resonator having a resonant frequency based on the frequency of the signal.

8. The apparatus according to claim 7, wherein the array of metal vias is part of an electromagnetic bandgap structure.

9. The apparatus according to claim 1, further comprising a gas cell in the gas cell cavity, wherein the gas cell contains a bipolar gas.

10. The apparatus according to claim 9, wherein the opening is a first opening near the first end of the gas cell, The aforementioned gas cell enclosure, A second opening extending between the gas cell cavity and the gas cell enclosure near the second end of the gas cell, wherein the third inner surface of the opening is covered with a third electromagnetic (EM) reflective coating, and A second trench located on the periphery of the opening and extending from the outer surface, wherein the fourth inner surface of the second trench is covered with a fourth EM reflective coating, A device including a device.

11. It is a device, circuit board and The antenna on the aforementioned substrate, A sealed container that encloses a bipolar gas, A waveguide is communicatively coupled between the antenna and the sealed container, wherein the waveguide is separated from the substrate by a gap, A stub, which is adjacent to the waveguide and extends away from the gap, A device including a device.

12. The apparatus according to claim 11, wherein the waveguide is surrounded by a structure having a trench extending away from the gap, the trench including a stub.

13. The apparatus according to claim 12, wherein the trench surrounds the waveguide.

14. The apparatus according to claim 13, wherein the trench has rounded corners or a circular footprint.

15. The apparatus according to claim 11, wherein the antenna is configured to transmit a signal into the sealed container via the waveguide, and the length of the stub is based on an odd multiple of the wavelength of the signal in the stub.

16. The apparatus according to claim 15, wherein the wavelength is a first wavelength, and the stub is separated from the waveguide by a distance based on the second wavelength of the signal in the gap and the length of the stub.

17. The apparatus according to claim 12, further comprising a container enclosure enclosing the sealed container and the waveguide, wherein the structure is part of the container enclosure.

18. The apparatus according to claim 15, wherein the wavelength is a first wavelength, and the thickness of the substrate is based on an odd multiple of the second wavelength of the signal in the substrate.

19. The apparatus according to claim 15, wherein the substrate includes an array of metal vias configured as a resonator having a resonant frequency based on the frequency of the signal.

20. The apparatus according to claim 19, wherein the array of metal vias is part of an electromagnetic bandgap structure.

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