Cartridge with resonant circuit for aerosol-generating device

Abstract

To provide a means for automatically identifying a cartridge so that an aerosol generating device can appropriately adapt to its aerosolization conditions.SOLUTION: A cartridge (100) for an aerosol-generating device (200), the cartridge (100) comprising an aerosol-forming substrate, an electric heater (120) for heating the aerosol-forming substrate, and a resonance circuit (155), wherein the resonance circuit (155) is configured to resonate at a predetermined resonance frequency, wherein the predetermined resonance frequency is associated with an identity of the cartridge (100), and wherein the resonance circuit (155) is connected in parallel with the electric heater (120).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to cartridges for aerosol generating devices. In particular, the present disclosure relates to cartridges for aerosol generating devices that include a resonant circuit that can be used to identify the cartridge or its contents within the aerosol generating device. The present disclosure also relates to aerosol generating devices for use with the cartridges, and to aerosol generating systems that include both the cartridge and the device. [Background technology]

[0002] Handheld, electrically operated aerosol generating systems can have a modular structure comprising a device and a removable cartridge. In known aerosol generating systems, the device typically comprises a battery and control electronics, and the cartridge comprises a liquid reservoir that holds a supply of liquid aerosol-forming substrate and an electric heater. The heater typically comprises a coil of wire wound around an elongated core that transports the liquid aerosol-forming substrate from the liquid reservoir to the heater. Electric current can be passed through the coil of wire to heat the heater, thereby generating an aerosol from the liquid aerosol-forming substrate. The cartridge also generally comprises a mouthpiece through which a user may draw the aerosol into their mouth.

[0003] Cartridges are typically interchangeable and can contain a variety of aerosol-forming substrates that may differ significantly in composition, flavor, strength, or other properties. Users can interchange cartridges at will. However, the conditions required to aerosolize a particular aerosol-forming substrate or to create a particular user experience may vary from cartridge to cartridge. In particular, the heating profile required for a particular cartridge may depend on the properties of the aerosol-forming substrate. Summary of the Invention [Problem to be solved by the invention]

[0004] It would therefore be desirable to provide a means for automatically identifying cartridges so that the aerosol generating device can appropriately adapt to its aerosolization requirements. [Means for solving the problem]

[0005] According to one embodiment of the present disclosure, there is provided a cartridge for an aerosol generating device. The cartridge may include an aerosol-forming substrate. The cartridge may include an electric heater for heating the aerosol-forming substrate. The cartridge may include a resonant circuit. The resonant circuit may be configured to resonate at a predetermined resonant frequency. The predetermined resonant frequency may be associated with an identity of the cartridge.

[0006] As used herein, the term "resonant circuit" refers to an electrical circuit that exhibits resonance or resonant behavior, i.e., the circuit naturally oscillates with a greater amplitude at one particular frequency, called its resonant frequency, than at other frequencies.

[0007] Advantageously, by configuring the resonant circuit to resonate at a predetermined resonant frequency, the aerosol generating device can unambiguously identify the cartridge or the aerosol-forming substrate contained in the cartridge by determining the frequency at which the resonance occurs. In other words, the resonant frequency serves as a unique characteristic of the cartridge. Different predetermined resonant frequencies can be used for different cartridges to enable differentiation between different cartridges. Once the cartridge is identified, the aerosol generating device can then apply a heating profile appropriate for the aerosol-forming substrate contained in the cartridge.

[0008] Advantageously, the resonant circuit can be constructed from a relatively small number of inexpensive electrical components, making the resonant circuit a simple and cost-effective method of cartridge identification compared to other identification methods such as memory chips or RFID tags.

[0009] An additional advantage of using a resonant circuit to identify cartridges is that the resonant circuit can be used as an anti-counterfeiting measure: if a user attempts to connect an unauthorized cartridge to their aerosol generating device that does not have a resonant circuit, or if a resonant circuit that does not have the expected predetermined resonant frequency is used, the aerosol generating device may be able to identify the cartridge as unauthorized or as a possible counterfeit and may be able to warn the user or shut down operation of the device.

[0010] The resonant circuit may be connected in parallel with the electric heater. The advantage of connecting the resonant circuit in parallel with the electric heater is that it helps reduce energy losses in the resonant circuit during heating by avoiding connecting passive electrical components of the resonant circuit in series with the heater. It is desirable to minimize energy consumption by the resonant circuit during heating so that more energy can be supplied to the heater. If passive components were arranged in series with the heater, the current supplied to the heater would also pass through these components, resulting in energy losses in these components (e.g., in parasitic elements) such as parasitic resistance.

[0011] A further advantage of connecting the resonant circuit in parallel with the electric heater is that the cartridge only requires two electrical contacts to both power the heater and provide an input signal to (and receive an output signal from) the resonant circuit, whereas if the resonant circuit were connected in series, at least one extra connection would be required to receive the output signal from the resonant circuit.

[0012] The resonant circuit may comprise three or fewer components. The resonant circuit may comprise two or fewer components. This reduces the complexity and cost of the circuit and also reduces the size of the circuit, i.e. the circuit requires less printed circuit board area.

[0013] The resonant circuit may comprise a capacitor and an inductor. This is the simplest type of resonant circuit and can be implemented with only two passive components. Advantageously, when the resonant circuit is disposed in parallel with the heater and a direct current (DC) voltage is applied to the cartridge to heat the heater, the capacitor blocks the DC voltage and effectively acts as an open circuit so that no DC current flows through the resonant circuit. Instead, DC flows only through the heater, thus minimizing energy loss in the resonant circuit during heating.

[0014] For a resonant circuit comprising an inductor and a capacitor (a so-called LC circuit), resonance occurs when the circuit receives (or is driven by) an AC or oscillating input AC signal at the resonant frequency. The resonant frequency is the frequency at which the magnitude of the inductive reactance and the magnitude of the capacitive reactance are equal. The resonant frequency of a resonant circuit can be determined by equation (1): JPEG2026026327000002.jpg1432(1) In the formula, f0 is the resonant frequency, L is the inductance of the inductor, and C is the capacitance of the capacitor.

[0015] The capacitor and inductor may be connected in series. The series arrangement of capacitor and inductor may be connected in parallel on either side of the heater. In a series LC circuit, resonance occurs when the capacitive reactance and inductive reactance are equal in magnitude but opposite in phase, causing the two reactances to cancel each other. Therefore, when the series arrangement of capacitor and inductor is resonant, the impedance of the resonant circuit is minimal.

[0016] As mentioned above, when a resonant circuit is disposed in parallel with the heater and a direct current (DC) voltage is applied to the cartridge to heat the heater, the capacitor blocks the DC voltage and effectively acts as an open circuit so that no DC current flows through the resonant circuit. Thus, by connecting an inductor in series with the capacitor, DC current is also prevented from flowing through the inductor, thereby reducing energy loss.

[0017] The predetermined resonant frequency of the resonant circuit may be determined by the capacitance of the capacitor. In this situation, the inductance of the inductor may be constant. While the inductance of the inductor may be set to approximately 1 microhenry (μH), any suitable inductance value may be used to achieve the predetermined resonant frequency. The predetermined resonant frequency may be changed by changing the capacitance of the capacitor. The capacitance of the capacitor may be changed by using a capacitor with a different capacitance value. Advantageously, this simply involves changing a single component of a particular resonant circuit. Any capacitor having an appropriate capacitance value may be used to achieve the predetermined resonant frequency. The capacitance of the capacitor may be in the range of 0.1 nanofarads (nF) to 10 nF. The capacitance of the capacitor may be varied by using a wide range of standard capacitor values. For example, capacitor values ​​of 0.27 nF, 0.39 nF, 0.56 nF, 0.82 nF, 1.2 nF, 1.8 nF, 2.7 nF, 3.9 nF, 5.6 nF, and 8.2 nF may be used. These values ​​are taken from standard capacitor values ​​of the E12 series and are therefore readily available.

[0018] Alternatively, the predetermined resonant frequency of the resonant circuit may be determined by the inductance of the inductor. The resonant frequency may be changed by changing the inductance of the inductor. In this situation, the capacitance of the capacitor may be constant. While the capacitance of the capacitor may be set to 270 nanofarads, any suitable capacitance value may be used to achieve the predetermined resonant frequency. The inductance of the inductor may be varied by using an inductor with a different inductance value. Advantageously, this simply involves changing a single component of the particular resonant circuit. Any inductor with an appropriate inductance value may be used to achieve the predetermined resonant frequency. The inductor inductance may range from 0.1 nanohenry (nH) to 330 nH. For example, inductor values ​​of 1 nH, 1.5 nH, 2.2 nH, 3.3 nH, 4.7 nH, 6.8 nH, 10 nH, 15 nH, 22 nH, and 33 nH may be used. These values ​​are taken from standard inductor values ​​in the E12 series and are therefore readily available.

[0019] Alternatively, the predetermined resonant frequency of the resonant circuit may be determined by both the capacitance of the capacitor and the inductance of the inductor, and any suitable combination of capacitance and inductance values ​​may be used to achieve the predetermined resonant frequency.

[0020] The predetermined resonant frequency may be in the range of 10 kilohertz (kHz) to 100 megahertz (MHz), preferably in the range of 100 kHz to 20 MHz, and more preferably in the range of 1 MHz to 11 MHz. An advantage of using a relatively high resonant frequency, e.g., a frequency in the megahertz range, is that it reduces the measurement time required to detect resonance. The inventors have found that high-frequency frequency sweeps can be performed more quickly than low-frequency frequency sweeps. A further advantage of using frequencies in the MHz range is that it increases the proportion of the measurement signal that passes through the resonant circuit compared to the heater. When an AC signal is input to the cartridge to detect resonance, it is split between the heater and the resonant circuit. In contrast to a DC signal, the AC signal can pass through the capacitor of the resonant circuit. It has been found that at higher frequencies, a lower proportion of the signal flows through the heater than at lower frequencies. Advantageously, this makes detecting the resonant frequency easier and also reduces energy loss in the heater compared to using lower frequencies.

[0021] The resonant circuit may include multiple capacitors arranged in parallel. The combined capacitance of the multiple capacitors may be used to generate resonance. The inventors have found that implementing the capacitor portion of the resonant circuit using two or more capacitors arranged in parallel helps improve the frequency response of the resonant circuit. That is, the parallel arrangement helps improve the signal output from the resonant circuit for a particular input frequency, which aids in detecting the resonant frequency. This is because the parallel arrangement of capacitors helps reduce parasitic series resistance.

[0022] The resonant circuit may be disposed on a printed circuit board (PCB). The resonant circuit may be disposed on its own separate PCB. This allows the resonant circuit to be manufactured as a separate modular part of the cartridge and function as a stand-alone identification or anti-counterfeiting device. Given that the resonant circuit can be implemented using relatively few components, less PCB area is required, which allows the PCB to easily fit within the cartridge of a handheld aerosol generator.

[0023] The inductor may be formed directly on the PCB as a conductive track. This can be easily fabricated during PCB manufacturing and reduces the number of components required for the resonant circuit. Alternatively, the inductor may comprise a separate surface-mounted device mounted on the PCB. The capacitor may also comprise a separate surface-mounted device mounted on the PCB.

[0024] The resonant circuit may comprise a capacitor connected in parallel with the heater, and may be configured to use a parasitic inductance of the resonant circuit in combination with a capacitance of the capacitor to generate resonance.

[0025] As used herein, the term “parasitic inductance” refers to the unavoidable inductance effect of all “real” electronic components, which may result from numerous factors, such as the component’s geometry, the component’s material, or how the component is used in a circuit. For example, a resistor may have parasitic inductance in addition to its resistance, and a capacitor may have parasitic inductance in addition to its capacitance. The term “real” above is used to distinguish actual physical components used in a circuit from ideal components that exist purely theoretically and have a single intended characteristic, such as pure resistance or pure capacitance without any parasitic elements. Generally, parasitic inductance is an undesirable inductance effect. Moreover, its effect is often slight and can be ignored in many applications. However, the inventors surprisingly discovered that in certain applications, parasitic inductance can be an advantage.

[0026] Advantageously, by using the parasitic inductance of the resonant circuit instead of an actual inductor component, the number of components in the resonant circuit can be reduced, which simplifies the circuit and reduces the PCB area required for the circuit.

[0027] Because parasitic inductances are often relatively small compared to the inductance of real inductor components, the resonant frequencies they produce are generally higher. The predetermined resonant frequencies may be in the range of 100 kHz to 100 MHz, and preferably in the range of 1 MHz to 50 MHz. These frequency ranges have the same advantages discussed above when describing resonant circuits using real inductors.

[0028] The predetermined resonant frequency of a resonant circuit may be determined by the capacitance of the capacitor. The predetermined resonant frequency of a resonant circuit may be changed by changing the capacitance of the capacitor. This can be achieved by using capacitors with different capacitance values ​​and involves changing only a single component of a particular resonant circuit. Any capacitor with an appropriate capacitance value may be used to achieve the predetermined resonant frequency. The capacitance of the capacitor may range from 1 nanofarad (nF) to 100 nF. The capacitance of the capacitor may be varied by using a wide range of standard capacitor values. For example, capacitor values ​​of 2.7 nF, 3.9 nF, 5.6 nF, 8.2 nF, 12 nF, 18 nF, 27 nF, 39 nF, 56 nF, and 82 nF may be used. These values ​​are taken from standard capacitor values ​​in the E12 series and are therefore readily available.

[0029] The resonant circuit may be arranged to be connected to a source of AC signals and configured to resonate when a predetermined resonant frequency is substantially equal to the frequency of the AC signal, which allows the resonant circuit to receive or be driven by an input AC signal to determine the resonant frequency.

[0030] The heater may include one or more heating elements. The heating elements may have any suitable shape or geometry. For example, the heating elements may be straight, formed as coils, or have an undulating or serpentine shape. The heating elements may include heating wires or filaments, such as Ni-Cr (nickel-chromium), platinum, tungsten, or alloy wires.

[0031] The heating element may be formed from any material having suitable electrical properties. Suitable materials include, but are not limited to, semiconductors such as doped ceramics, "conductive" ceramics (e.g., molybdenum disilicide), carbon, graphite, metals, alloys, and composites made of ceramic and metallic materials. Such composites may include doped or undoped ceramics. An example of a suitable doped ceramic is doped silicon carbide. Examples of suitable metals include titanium, zirconium, tantalum, and platinum group metals.

[0032] Examples of suitable alloys include stainless steel, constantan, nickel-, cobalt-, chromium-, aluminum-, titanium-, zirconium-, hafnium-, niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-, manganese-, and iron-containing alloys, as well as nickel-, iron-, cobalt-, and stainless steel-based superalloys, Timetal®, iron-aluminum-based alloys, and iron-manganese-aluminum-based alloys. Timetal® is a registered trademark of Titanium Metals Corporation. The filaments may be coated with one or more insulators. Preferred materials for the conductive filaments are stainless steel and graphite, with 300 series stainless steels, such as AISI 304, 316, 304L, and 316L, being more preferred. Additionally, the conductive heating element may include a combination of the above materials. Combinations of materials may be used to improve control of the resistance of the substantially flat heating element. For example, a material with a high resistivity may be combined with a material with a low resistivity. This may be advantageous if one of the materials is more advantageous from other perspectives, such as price, machinability, or other physical and chemical parameters. Advantageously, a heater with a high resistivity allows for more efficient use of battery energy.

[0033] The heating element may be a fluid permeable heating element, which may include a plurality of gaps or openings extending from the first side to the second side of the heating element through which fluid may pass.

[0034] The heating element may comprise a substantially flat heating element to allow for simple manufacturing. Geometrically, the term "substantially flat" heating element is used to refer to a heating element that is in the form of a substantially two-dimensional topological manifold. Thus, a substantially flat heating element extends substantially in two dimensions along a surface rather than in three dimensions. In particular, the dimension of a substantially flat heating element in two dimensions within its surface is at least five times its dimension in the third dimension perpendicular to the surface. An example of a substantially flat heating element is a structure between two substantially parallel imaginary surfaces, the distance between these two imaginary surfaces being substantially less than its extension within the surface. In some embodiments, the substantially flat heating element is planar. In other embodiments, the substantially flat heating element is curved along one or more dimensions, for example, forming a dome or bridge shape.

[0035] The heating element may comprise multiple conductive filaments. The term "filament" is used to refer to an electrical path disposed between two electrical contacts. The filament may arbitrarily branch and diverge into several paths or filaments, respectively, or several electrical paths may merge into one path. The filaments may have a cross section that is round, square, flat, or of any other shape. The filaments may be arranged in a straight or curved manner.

[0036] The heating element may be, for example, an array of filaments arranged parallel to one another. Preferably, the filaments may form a mesh. The mesh may be woven or non-woven. The mesh may be formed using different types of weave or lattice structures. Alternatively, the conductive heating element may consist of an array of filaments or a woven fabric of filaments. A mesh, array, or woven fabric of conductive filaments may also be characterized by its ability to retain liquid.

[0037] In one preferred embodiment, the substantially flat heating element may be constructed of wires formed into a wire mesh. The mesh preferably has a plain weave design. The heating element is preferably a wire grill made from mesh strips.

[0038] The conductive filaments may define gaps between them, which may have a width of 10 micrometers to 100 micrometers. The filaments preferably create capillary action within the gaps so that liquid to be vaporized in use is drawn into the gaps, increasing the contact area between the heating element and the liquid aerosol-forming substrate.

[0039] The conductive filaments may form a mesh with a size of 60 to 240 filaments per centimeter (±10 percent). The mesh density is preferably 100 to 140 filaments per centimeter (±10 percent). More preferably, the mesh density is approximately 115 filaments per centimeter. The gap width may be 100 micrometers to 25 micrometers, preferably 80 micrometers to 70 micrometers, and more preferably approximately 74 micrometers. The open area of ​​the mesh, which is the ratio of the gap area to the total area of ​​the mesh, may be 40 percent to 90 percent, preferably 85 percent to 80 percent, and more preferably approximately 82 percent.

[0040] The conductive filaments may have a diameter of 8 micrometers to 100 micrometers, preferably 10 micrometers to 50 micrometers, more preferably 12 micrometers to 25 micrometers, and most preferably approximately 16 micrometers. The filaments may have a round or flattened cross section.

[0041] The area of ​​the conductive filament mesh, array, or woven fabric may be small, for example, 50 square millimeters or less, preferably 25 square millimeters or less, and more preferably approximately 15 square millimeters. The size is selected to allow the heating element to be incorporated into a handheld system. Sizing the conductive filament mesh, array, or woven fabric to 50 square millimeters or less reduces the total amount of power required to heat the conductive filament mesh, array, or woven fabric while still ensuring that the conductive filament mesh, array, or woven fabric is in sufficient contact with the liquid aerosol-forming substrate. The conductive filament mesh, array, or woven fabric may be rectangular, for example, and may have a length of 2 to 10 millimeters and a width of 2 to 10 millimeters. The mesh preferably has dimensions of approximately 5 millimeters by 3 millimeters.

[0042] Preferably, the filament is made of wire, more preferably the wire is made of metal, most preferably stainless steel.

[0043] The electrical resistance of the mesh, array, or woven conductive filaments of the heating element may be between 0.3 ohms and 4 ohms. Preferably, the electrical resistance is 0.5 ohms or greater. More preferably, the electrical resistance of the mesh, array, or woven conductive filaments is between 0.6 ohms and 0.8 ohms, and most preferably about 0.68 ohms. The electrical resistivity of the mesh, array, or woven conductive filaments is preferably at least one order of magnitude greater, and more preferably at least two orders of magnitude greater, than the electrical resistivity of any conductive contacts. This ensures that heat generated by passing current through the heating element is localized to the mesh or array of conductive filaments. If the system is battery-powered, a low overall resistance to the heating element is advantageous. A low-resistance, high-current system allows for high power delivery to the heating element, allowing the heating element to quickly heat the conductive filaments to the desired temperature.

[0044] Alternatively, the heating element may comprise a heating plate having an array of apertures formed therein. The apertures may be formed, for example, by etching or machining. The plate may be formed of any material having suitable electrical properties, such as those materials described above with respect to the heating element.

[0045] The electrical contact portions may be located on opposite ends of the heating element. The electrical contact portions may comprise two conductive contact pads. The conductive contact pads may be located in the edge areas of the heating element. Preferably, at least two conductive contact pads may be located at the tip of the heating element. The conductive contact pads may be fixed directly to the conductive filaments of the heating element. The conductive contact pads may comprise tin patches. Alternatively, the conductive contact pads may be integral with the heating element.

[0046] The cartridge may include a liquid storage compartment. The liquid aerosol-forming substrate is held in the liquid storage compartment. The liquid storage compartment may have a first portion and a second portion that communicate with each other. The first portion of the liquid storage compartment may be on an opposite side of the heater from the second portion of the liquid storage compartment. The liquid aerosol-forming substrate is held in the first portion of the liquid storage compartment.

[0047] Advantageously, the first portion of the storage compartment is larger than the second portion of the storage compartment. The cartridge may be configured to allow a user to suck on or draw on the cartridge to inhale the aerosol generated within the cartridge. In use, the mouth-end opening of the cartridge is typically positioned above the heater, and the first portion of the storage compartment is positioned between the mouth-end opening and the heater. Having the first portion of the storage compartment larger than the second portion of the storage compartment ensures that liquid is delivered from the first portion of the storage compartment to the second portion of the storage compartment and to the heater under the influence of gravity during use.

[0048] The cartridge may have a mouth end through which the generated aerosol passes that can be withdrawn by a user, and a connection end configured to connect to an aerosol generating device, with a first side of the heater facing the mouth end and a second side of the heater facing the connection end.

[0049] The cartridge may define an enclosed airflow path or passageway from the air inlet, past the first side of the heater, and to the mouth-end opening of the cartridge. The enclosed airflow passageway may pass through the first or second portion of the liquid storage compartment. In one embodiment, the airflow path extends between the first and second portions of the liquid storage compartment. Additionally, the airflow passageway may extend through the first portion of the liquid storage compartment. For example, the first portion of the liquid storage compartment may have an annular cross-section, with the airflow passageway extending through the first portion of the liquid storage compartment from the heater to the mouth-end opening. Alternatively, the airflow passageway may extend from the heater to the mouth-end opening adjacent the first portion of the liquid storage compartment.

[0050] The cartridge may include a capillary material in contact with a second side of the heater. The capillary material delivers the liquid aerosol-forming substrate to the heater against gravity. By requiring the liquid aerosol-forming substrate to travel against gravity to reach the heater during use, the likelihood of large droplets of liquid entering the airflow passage is reduced.

[0051] A capillary material is a material that allows a liquid to wick from one end of the material to another by capillary action. The capillary material may have a fibrous or spongy structure. Preferably, the capillary material comprises a bundle of capillaries. For example, the capillary material may comprise a plurality of fibers or threads or other fine tubes. The fibers or threads may be generally aligned to transport the liquid aerosol-forming substrate toward the heating element. Alternatively, the capillary material may comprise a spongy or foam-like material. The structure of the capillary material forms a plurality of small holes or tubes through which the liquid aerosol-forming substrate can be transported by capillary action. The capillary material may extend into gaps or openings in the heater. The heater may draw the liquid aerosol-forming substrate into the gaps or openings by capillary action.

[0052] The capillary material may comprise any suitable material or combination of materials. Examples of suitable materials include sponge or foam materials, ceramic or graphite-based materials in the form of fibers or sintered powders, expanded metal or plastic materials, and fibrous materials, such as spun or extruded fibers (cellulose acetate, polyester, or bonded polyolefin, polyethylene, terylene, or polypropylene fibers, nylon fibers, or ceramics). The capillary material may have any suitable capillary action and porosity for use with different liquid physical properties. The liquid aerosol-forming substrate has physical properties, including, but not limited to, viscosity, surface tension, density, thermal conductivity, boiling point, and vapor pressure, that allow the liquid aerosol-forming substrate to be transported through the capillary medium by capillary action.

[0053] Alternatively, or additionally, the cartridge may include a retaining material for retaining the liquid aerosol-forming substrate. The retaining material may be in the first portion of the storage compartment, or in the second portion of the storage compartment, or in both the first and second portions of the storage compartment. The retaining material may be a foam, a sponge, or a collection of fibers. The retaining material may be formed of a polymer or copolymer. In one embodiment, the retaining material is a spun polymer. The liquid aerosol-forming substrate may be released into the retaining material during use. For example, the liquid aerosol-forming substrate may be provided in a capsule.

[0054] The cartridge advantageously contains a liquid aerosol-forming substrate. As used herein, the term "aerosol-forming substrate" refers to a substrate capable of releasing a volatile compound capable of forming an aerosol. The volatile compound may be released by heating the aerosol-forming substrate.

[0055] The aerosol-forming substrate may be liquid at room temperature. The aerosol-forming substrate may contain both liquid and solid components. The liquid aerosol-forming substrate may contain nicotine. The nicotine-containing liquid aerosol-forming substrate may be a nicotine salt matrix. The liquid aerosol-forming substrate may contain plant-derived material. The liquid aerosol-forming substrate may contain tobacco. The liquid aerosol-forming substrate may contain tobacco-containing material containing volatile tobacco flavour compounds that are released from the aerosol-forming substrate on heating. The liquid aerosol-forming substrate may contain homogenised tobacco material. The liquid aerosol-forming substrate may contain non-tobacco-containing material. The liquid aerosol-forming substrate may contain homogenised plant-derived material.

[0056] The liquid aerosol-forming substrate may contain one or more aerosol formers. The aerosol former is any suitable, well-known compound or mixture of compounds that facilitates the formation of a dense, stable aerosol during use and is substantially resistant to thermal decomposition at the operating temperature of the system. Examples of suitable aerosol formers include glycerin and propylene glycol. Suitable aerosol formers are well-known in the art and include, but are not limited to, polyhydric alcohols (e.g., triethylene glycol, 1,3-butanediol, glycerin), esters of polyhydric alcohols (e.g., glycerol monoacetate, diacetate, or triacetate), and aliphatic esters of monocarboxylic, dicarboxylic, or polycarboxylic acids (e.g., dimethyl dodecanedioate, dimethyl tetradecanedioate). The liquid aerosol-forming substrate may contain water, solvents, ethanol, plant extracts, and natural or artificial flavors.

[0057] The liquid aerosol-forming substrate may comprise nicotine and at least one aerosol former. The aerosol former may be glycerin or propylene glycol. The aerosol former may comprise both glycerin and propylene glycol. The liquid aerosol-forming substrate may have a nicotine concentration of about 0.5% to about 10% (e.g., about 2%).

[0058] The cartridge may include a housing. The housing may be formed from a moldable plastic material such as polypropylene (PP) or polyethylene terephthalate (PET). The housing may form some or all of the walls of one or both portions of the liquid storage compartment. The housing and the liquid storage compartment may be integrally formed. Alternatively, the liquid storage compartment may be formed separately from the housing and assembled to the housing.

[0059] According to another embodiment of the present disclosure, there is provided an aerosol generating device. The aerosol generating device may comprise a housing configured to receive the cartridge as described above. The housing may comprise an electrical connection for electrically connecting to the cartridge. The aerosol generating device may further comprise a power source for supplying power to an electric heater of the cartridge. The aerosol generating device may further comprise an AC signal source for inputting an AC signal to a resonant circuit of the cartridge. The aerosol generating device may further comprise a control circuit configured to control the supply of power to the electric heater and to controllably vary the frequency of the AC signal supplied to the resonant circuit. The control circuit may be arranged to receive an output signal from the resonant circuit. The control circuit may be further configured to determine when resonance occurs in the resonant circuit by detecting when the output signal reaches a predetermined threshold. The control circuit may be further configured to determine the frequency at which resonance occurs. The control circuit may be further configured to identify the cartridge based on the determined resonant frequency.

[0060] Advantageously, an aerosol generating device can be used with one of the cartridges described above and can identify the cartridge so as to use the appropriate aerosolization conditions for the particular aerosol-forming substrate contained within the cartridge. Additionally, the aerosol generating device can advantageously detect non-certified or counterfeit cartridges that do not provide the expected resonant frequency for the device.

[0061] The predetermined threshold used to determine when resonance occurs may include a maximum or minimum output signal.

[0062] The control circuit may be configured to sweep the frequency of the AC signal over a predetermined frequency range within a predetermined period of time. Advantageously, sweeping a predetermined frequency range has been found to be an effective way of detecting expected resonant frequencies within a frequency range. The control circuit of the aerosol generating device can be configured to do this quickly and efficiently. The frequency of the AC signal may be swept over the predetermined frequency range within a predetermined period of 5 milliseconds or less. This allows for rapid detection of the resonant frequency and cartridge identification. Furthermore, the 5 millisecond detection time is sufficiently short so that cartridge identification can be performed during a power-off portion of the pulse-width modulated power supply (e.g., a pulse-width modulated power supply having a 10 millisecond period and a 50 percent duty cycle) supplied to the heater.

[0063] As an alternative to continuously sweeping a predetermined frequency range, the control circuitry of the aerosol generating device may be configured to monitor a plurality of predetermined frequencies or frequency bands to determine whether resonance occurs at or within those frequencies or frequency bands. The control circuitry may be configured to continuously move or hop between frequencies or frequency bands to determine the resonant frequency and, therefore, cartridge identity. This may advantageously reduce the time it takes to determine the resonant frequency and may also reduce energy consumption during cartridge identity.

[0064] The peak voltage of the AC signal supplied to the resonant circuit may be 2 volts (V) or less, preferably 1.5 V or less, and more preferably 1 V or less. Advantageously, by using a peak voltage of 2 V or less for the AC signal, any significant heating of the heater can be avoided and thus energy losses can be reduced or kept to a minimum.

[0065] The control circuit may comprise a microprocessor. The microprocessor may be a programmable microprocessor, a microcontroller, or an application specific integrated chip (ASIC) or other electronic circuit capable of providing control. The control circuit may comprise additional electronic components. For example, in some embodiments, the control circuit may comprise a sensor, a switch, or a display element. Power may be supplied to the aerosol generation element continuously after activation of the device, or may be supplied intermittently, such as with each puff. Power may be supplied to the aerosol generation element in the form of current pulses, for example, by pulse width modulation (PWM). The power source may be a battery. The battery may be a lithium iron phosphate battery within the device. Alternatively, the power source may be another form of charge storage device, such as a capacitor.

[0066] The control circuit may include a resonance detection circuit for detecting when resonance occurs. The resonance detection circuit may include a peak detection circuit for detecting when the value of the output signal reaches a peak value or a predetermined threshold. As used herein, the term "peak detection circuit" refers to a circuit that can detect both a maximum value or threshold and a minimum value or threshold.

[0067] In some embodiments, the control circuit is configured to query a look-up table stored in a memory of the control circuit and to compare the determined resonant frequency with one or more reference resonant frequencies stored in the look-up table.

[0068] In other words, the control circuit may include a memory that stores one or more reference resonant frequency values, each reference resonant frequency value being associated with a particular cartridge identity. The control circuit is configured to compare the determined resonant frequency value measured from the resonant circuit with the reference resonant frequency values ​​stored in the lookup table. If the determined resonant frequency value matches a reference resonant frequency value stored in the lookup table, the cartridge identity is determined to be the cartridge identity associated with the matched reference resonant frequency value.

[0069] Of course, the ranges of reference frequency values ​​may be stored in a look-up table, and each range of reference resonant frequency values ​​may be associated with a particular cartridge identity. The determined resonant frequency value is compared to the range of resonant frequency values, and when the determined resonant frequency value falls within the range of reference resonant frequency values, the cartridge identity is determined to be the cartridge identity associated with the range of reference frequency values ​​within which the determined resonant frequency value falls.

[0070] The control circuitry may be configured to control the supply of power from the aerosol generating device's power supply to the cartridge's electric heater based on the determined identity of the cartridge.

[0071] In some examples, the control circuitry may be configured to prevent power from being supplied from the power source to the electric heater if the identity of the cartridge is not recognized. In other words, the control circuitry may be configured to prevent power from being supplied from the power source to the electric heater if the determined resonant frequency does not equal an expected resonant frequency value. In embodiments in which a look-up table of reference resonant frequency values ​​is stored in the controller's memory, the control circuitry may be configured to prevent power from being supplied to the electric heater when the determined resonant frequency does not match any of the stored reference resonant frequency values. Advantageously, preventing power from being supplied to the electric heater when the determined resonant frequency does not match an expected resonant frequency may prevent or deter unauthorized cartridges from being used with the aerosol generating device.

[0072] In some embodiments, the control circuitry may be configured to adjust the power supplied from the power source to the electric heater based on the determined identity of the cartridge, which may enable the aerosol-generating device to heat different aerosol-forming substrates contained in different cartridges to different temperatures.

[0073] Advantageously, configuring the control circuit to adjust the power supplied to the electric heater based on the determined cartridge identity may enable the aerosol generating device to be used with different types of cartridges containing different aerosol-forming substrates. Because different aerosol-forming substrates may require heating to different temperatures to achieve an aerosol with desired properties, adjusting the power supplied to the heater based on the determined cartridge identity may ensure that the aerosol generating device is configured to generate optimal aerosols from different cartridges containing different aerosol-forming substrates.

[0074] In some examples, the control circuit may be configured to supply a first power to the electric heater when an identity of a first cartridge is determined, and the control circuit may be further configured to supply a second power, different from the first power, to the electric heater when an identity of a second cartridge, different from the identity of the first cartridge, is determined.

[0075] The power source may be a DC power source. The power source may be a battery. The battery may be a lithium-based battery, such as a lithium cobalt battery, a lithium iron phosphate battery, a lithium titanate battery, or a lithium polymer battery. The battery may be a nickel-metal hydride battery or a nickel-cadmium battery. The power source may be another form of charge storage device, such as a capacitor. The power source may be rechargeable and configured for numerous charge-discharge cycles. The power source may have a capacity that allows for storage of energy sufficient for one or more user experiences; for example, the power source may have a capacity sufficient to allow continuous generation of aerosol for approximately six minutes, corresponding to the typical time it takes to smoke one conventional cigarette, or a multiple of six minutes. In another embodiment, the power source may have a capacity sufficient to allow for a predetermined number of puffs or for discontinuous activation of the atomization assembly.

[0076] The aerosol generating device may include a housing. The housing may be elongated. The housing may comprise any suitable material or combination of materials. Examples of suitable materials include metals, alloys, plastics, or composites containing one or more of these materials, or thermoplastics suitable for food or pharmaceutical applications, such as polypropylene, polyetheretherketone (PEEK), or polyethylene. Preferably, the material is light and not brittle.

[0077] According to another embodiment of the present disclosure, there is provided an aerosol generation system, which may comprise the aerosol generator described above and the cartridge described above.

[0078] The aerosol generation system may be a handheld aerosol generation system configured to allow a user to draw on the mouthpiece to draw aerosol through the mouth-end opening. The aerosol generation system may have a size comparable to a conventional cigar or cigarette. The aerosol generation system may have an overall length of about 30 mm to about 150 mm. The aerosol generation system may have an outer diameter of about 5 mm to about 30 mm.

[0079] The present invention is defined in the claims. However, the following provides a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of any other example, embodiment, or aspect described herein.

[0080] Example 1: A cartridge for an aerosol generating device, comprising an aerosol-forming substrate and a resonant circuit, the resonant circuit configured to resonate at a predetermined resonant frequency, the predetermined resonant frequency being associated with the identity of the cartridge. Example 2: A cartridge as described in Example 1, further comprising an electric heater for heating the aerosol-forming substrate. Example 3: A cartridge as described in example 2, wherein the resonant circuit is connected in parallel with the electric heater. Example 4: A cartridge according to any one of Examples 1 to 3, wherein the resonant circuit comprises a capacitor and an inductor. Example 5: A cartridge as described in Example 4, wherein the capacitor and inductor are connected in series. Example 6: The cartridge of example 4 or example 5, wherein the predetermined resonant frequency of the resonant circuit is determined by the capacitance of the capacitor, and the predetermined resonant frequency can be changed by changing the capacitance of the capacitor. Example 7: The cartridge according to any one of Examples 1 to 6, wherein the predetermined resonance frequency is in the range of 10 kHz to 100 MHz, preferably in the range of 100 kHz to 20 MHz, and more preferably in the range of 1 MHz to 11 MHz. Example 8: The cartridge according to any one of Examples 4 to 7, wherein the capacitance of the capacitor is in the range of 0.1 nF to 10 nF. Example 9: A cartridge according to any of Examples 4 to 8, wherein the resonant circuit comprises a plurality of capacitors arranged in parallel, and the combined capacitance of the plurality of capacitors is used to generate the resonance. Example 10: A cartridge according to any of Examples 4 to 9, wherein the resonant circuit is disposed on a printed circuit board (PCB) and the inductor is formed as a conductive track directly on the PCB. Example 11: A cartridge described in any of Examples 1 to 3, wherein the resonant circuit comprises a capacitor connected in parallel with the heater, and the resonant circuit is configured to generate resonance using the parasitic inductance of the resonant circuit in combination with the capacitance of the capacitor. Example 12: The cartridge according to Example 11, wherein the predetermined resonance frequency is in the range of 100 kHz to 100 MHz, and preferably in the range of 1 MHz to 50 MHz. Example 13: The cartridge according to Example 11 or Example 12, wherein the capacitance of the capacitor is in the range of 1 nF to 300 nF. Example 14: A cartridge according to any one of Examples 1 to 5, wherein the predetermined resonant frequency of the resonant circuit is determined by the inductance of the inductor, and the resonant frequency can be changed by changing the inductance of the inductor. Example 15: The cartridge according to Example 14, wherein the inductor has an inductance in the range of 0.1 nH to 330 nH. Example 16: A cartridge described in any of Examples 1 to 15, wherein the resonant circuit is arranged to be connected to an AC signal source and is configured to resonate when the predetermined resonant frequency is substantially equal to the frequency of the AC signal. Example 17: The cartridge of any of Examples 1 to 16, wherein the electric heater is a fluid permeable heater, and preferably a mesh heater. Example 18: An aerosol generating device comprising: a housing configured to receive a cartridge described in any of Examples 1 to 17, the housing having electrical connections for electrically connecting to the cartridge; a power source for supplying power to an electric heater of the cartridge; an AC signal source for inputting an AC signal to a resonant circuit of the cartridge; and a control circuit configured to control the supply of power to the electric heater and to controllably vary the frequency of the AC signal supplied to the resonant circuit, the control circuit being arranged to receive an output signal from the resonant circuit and further configured to determine when resonance occurs in the control circuit by detecting when the output signal reaches a predetermined threshold, and to determine the frequency at which resonance occurs, and to identify the cartridge based on the determined resonant frequency. Example 19: An aerosol generating device as described in Example 18, wherein the control circuit is configured to sweep the frequency of the AC signal over a predetermined frequency range within a predetermined period of time, the predetermined period being 5 milliseconds or less. Example 20: An aerosol generating device according to Example 18 or Example 19, wherein the peak voltage of the AC signal supplied to the resonant circuit is 2 V or less, preferably 1.5 V or less, and more preferably 1 V or less. Example 21: An aerosol generating device according to any one of Examples 18 to 20, wherein the predetermined threshold comprises a maximum or minimum output signal. Example 22: An aerosol generating device described in any of Examples 18 to 21, wherein the control circuitry of the aerosol generating device may be configured to monitor a plurality of predetermined frequencies or frequency bands in the frequency range to determine whether resonance occurs at those frequencies or within those frequency bands.

[0081] The embodiments will now be further described with reference to the following figures: [Brief explanation of the drawings]

[0082] [Figure 1]FIG. 1 is a schematic diagram of an exemplary aerosol generation system including a cartridge and an aerosol generator. [Figure 2] FIG. 2 is a block diagram illustrating the major electrical and electronic components of an exemplary aerosol generation system. [Figure 3A] FIG. 3A shows a schematic circuit diagram of an example cartridge with a resonant circuit, in which the example cartridge is connected to a DC voltage source. [Figure 3B] FIG. 3B shows a schematic circuit diagram of the cartridge of FIG. 3A, where the cartridge is connected to an AC signal source. [Figure 4] FIG. 4 is a graph of frequency versus voltage showing the frequency response of the resonant circuit of FIG. 3B when using different capacitor values. [Figure 5] 5 is a schematic diagram of an exemplary circuit for an aerosol generation system for determining the resonant frequency of the resonant circuit of a cartridge, the cartridge being the exemplary cartridge of FIGS. 3A and 3B. [Figure 6A] FIG. 6A is a graph of voltage versus time showing the detection of resonance for different values ​​of capacitor in a resonant circuit. [Figure 6B] FIG. 6B is a graph of voltage versus time showing the detection of resonance for different values ​​of capacitor in a resonant circuit. [Figure 6C] FIG. 6C is a graph of voltage versus time showing the detection of resonance for different values ​​of capacitor in a resonant circuit. [Figure 7] FIG. 7 is a plan view of a printed circuit board having a resonant circuit thereon. [Figure 8] FIG. 8 shows a schematic circuit diagram of another example cartridge with another resonant circuit, in which the example cartridge is connected to an AC signal source. [Figure 9] FIG. 9 is a graph of frequency versus voltage showing the frequency response of the resonant circuit of FIG. 8 when using different capacitor values. [Figure 10] FIG. 10 shows a schematic circuit diagram of yet another example cartridge with another resonant circuit, in which the example cartridge is connected to an AC signal source. [Figure 11] FIG. 11 is a graph of frequency versus voltage showing the frequency response of the resonant circuit of FIG. 10 when using different capacitor values. [Figure 12] 12 is a schematic diagram of an exemplary circuit for an aerosol generation system for determining the resonant frequency of a resonant circuit of a cartridge, the cartridge being the exemplary cartridge of FIG. [Figure 13A] FIG. 13A is a graph of voltage versus time illustrating the detection of resonance for different values ​​of capacitor in the resonant circuit of FIG. [Figure 13B] FIG. 13B is a graph of voltage versus time illustrating the detection of resonance for different values ​​of capacitor in the resonant circuit of FIG. [Figure 13C] FIG. 13C is a graph of voltage versus time illustrating the detection of resonance for different values ​​of capacitor in the resonant circuit of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0083] FIG. 1 is a schematic diagram of an exemplary aerosol generation system 10. The aerosol generation system 10 comprises two main components: a cartridge 100 and a main body or aerosol generation device 200. A connecting end 115 of the cartridge 100 is removably connected to a corresponding connecting end 205 of the aerosol generation device 200. The connecting end 115 of the cartridge 100 and the connecting end 205 of the aerosol generation device 200 each have electrical contacts or connections (not shown) arranged to cooperate to provide electrical connection between the cartridge 100 and the aerosol generation device 200. The aerosol generation device 200 includes a power source in the form of a battery 210 (which in this embodiment is a rechargeable lithium-ion battery) and a control circuit 220. The aerosol generation system is portable and has a size comparable to that of a conventional cigar or cigarette. A mouthpiece 125 is disposed at the end of the cartridge 100 opposite the connecting end 115.

[0084] The cartridge 100 includes a housing 105 containing an electric heater 120 and a liquid storage compartment having a first portion 130 and a second portion 135. A liquid aerosol-forming substrate is held in the liquid storage compartment. Although not shown in FIG. 1 , the first portion 130 of the liquid storage compartment is connected to the second portion 135 of the liquid storage compartment so that liquid in the first portion 130 can move to the second portion 135. The electric heater 120 receives liquid from the second portion 135 of the liquid storage compartment. In this embodiment, the electric heater 120 includes a fluid-permeable heating element (e.g., a mesh heater). The cartridge 100 further includes a resonant circuit 155 implemented on a printed circuit board (PCB), disposed on a side of the second portion 135 of the liquid storage compartment, and connected in parallel to the heater 120 via a conductor (not shown).

[0085] Airflow passages 140, 145 extend through the cartridge 100 from an air inlet 150 formed in the side of the housing 105, past the heater 120, and from the heater 120 to a mouthpiece opening 110 formed in the housing 105 at the end of the cartridge 100 opposite the connecting end 115.

[0086] The components of the cartridge 100 are arranged so that the first portion 130 of the liquid storage compartment is between the heater 120 and the mouthpiece opening 110, and the second portion 135 of the liquid storage compartment is positioned on the side of the heater 120 opposite the mouthpiece opening 110. In other words, the heater 120 is positioned between the two portions 130 and 135 of the liquid storage compartment and receives liquid from the second portion 135. The first portion 130 of the liquid storage compartment is closer to the mouthpiece opening 110 than the second portion 135 of the liquid storage compartment. Airflow passages 140, 145 extend past the heater 120 and between the first portion 130 and the second portion 135 of the liquid storage compartment.

[0087] The aerosol generation system 10 is configured to allow a user to inhale or suck on the cartridge mouthpiece 125, drawing aerosol into their mouth through the mouthpiece opening 110. In operation, when a user inhales on the mouthpiece 125, air is drawn from the air inlet 150, through the airflow passages 140, 145, past the heater 120, and into the mouthpiece opening 110. A control circuit 220 controls the supply of power from the battery 210 to the cartridge 100 when the system is activated, which in turn controls the amount and characteristics of the vapor produced by the heater 120. The control circuit 220 may include an airflow sensor (not shown), and may supply power to the heater 120 when the airflow sensor detects the user's drawing on the cartridge 100. This type of control arrangement is well established in aerosol generation systems such as inhalers and e-cigarettes. Thus, when a user draws on mouthpiece opening 110 of cartridge 100, heater 120 is activated to generate a vapor that is entrained in the airflow passing through airflow passage 140. The vapor cools within the airflow in passage 145 to form an aerosol, which is then drawn through mouthpiece opening 110 into the user's mouth.

[0088] In operation, the mouthpiece opening 110 is typically the highest point in the system. The construction of the cartridge 100, and in particular the placement of the heater 120 between the first portion 130 and the second portion 135 of the liquid storage compartment, is advantageous because it utilizes gravity to ensure that the liquid substrate is delivered to the heater 120 even when the liquid storage compartment is beginning to empty, yet prevents oversupply of liquid to the heater 120, which may lead to leakage of liquid into the airflow passage 140.

[0089] 2 is a block diagram illustrating the major electrical and electronic components of an exemplary aerosol generation system 10, including a cartridge 100 and an aerosol generation device 200. The cartridge 100 includes an electric heater 120 and a resonant circuit 155. The resonant circuit 155 is configured to resonate at a predetermined resonant frequency that is associated with the identity of the cartridge 100 or the aerosol-forming substrate (not shown) contained within the cartridge 100. By determining the resonant frequency of the resonant circuit 155, the aerosol generation device 200 can identify the cartridge 100 and its contents and apply appropriate aerosolization conditions. For example, the aerosol generation device 200 may apply a heating profile appropriate for the particular liquid aerosol-forming substrate contained within the cartridge 100.

[0090] The resonant circuit 155 is connected in parallel on both sides of the electric heater 120. By connecting the resonant circuit 155 in parallel with the heater 120, only two electrical connections 242 are required to connect the cartridge 100 to the aerosol generation device 200. The two electrical connections 242 can be used to power the heater 120, to provide an input AC signal to the resonant circuit 155, and to receive an output signal from the resonant circuit 155. Different exemplary resonant circuits of the present disclosure are described in more detail below.

[0091] The aerosol generating device 200 includes a battery 210 serving as a power source and a microcontroller (MCU) 230 forming part of the control circuitry of the aerosol generating device 200. The microcontroller 230 is configured to control the supply of power to the electric heater 120. The microcontroller 230 controls the supply of a DC voltage source 236 to the heater 120. The microcontroller 230 modulates the DC voltage source 236 by pulse width modulation (PWM) to provide power to the electric heater 120 as a series of pulses. The DC voltage source 236 can be selectively connected to the electric heater 120 by a switch 240, which may be a transistor or other suitable electronic switch. No passive components (such as resistors or inductors) capable of generating heat are connected in series between the DC voltage source and the electric heater 120. This helps to reduce energy losses.

[0092] The microcontroller 230 also controls the provision of an AC signal source or AC source 234 to the cartridge 100, particularly as an input signal to the resonant circuit 155. The microcontroller 230 can vary or sweep the frequency of the AC signal provided to the resonant circuit 155 over a frequency range that includes the resonant frequency of the resonant circuit 155. A resistor 238 is disposed within the aerosol generator so as to be connected in series between the AC signal source 234 and the resonant circuit 155 within the cartridge 100. The resistor 238 forms part of a voltage divider with the components of the resonant circuit 155, allowing a measured voltage to be taken from the circuit at point X between the resistor 238 and the resonant circuit 155.

[0093] 2 shows the alternating current signal source or AC source 234 and the DC voltage source 236 as separate blocks in the diagram, this is shown for clarity purposes only, and in reality both of these sources are provided by the microcontroller 230, potentially with a few auxiliary components such as transistors to source higher currents, but it will be appreciated that in other embodiments separate AC and DC sources may be provided.

[0094] The aerosol generation device 200 further comprises a peak detection circuit 232 that forms a further part of the control circuitry of the aerosol generation device 200. The peak detection circuit 232 receives the output signal from the resonant circuit 155 and provides an output of the peak detection circuit to the microcontroller 230. In receiving the output signal from the resonant circuit 155, the peak detection circuit 232 measures the voltage at point X between resistor 238 and the resonant circuit 155. The peak detection circuit 232 can determine or measure peak amplitudes that occur in the output signal from the resonant circuit 155 or when the output signal reaches a predetermined threshold. As mentioned above, when the resonant circuit resonates at its resonant frequency, the output signal oscillates with a larger amplitude than at other frequencies. Thus, the microcontroller 230 varies or sweeps the frequency of the AC signal supplied to the resonant circuit 155 over a predetermined frequency range within which the resonant frequency is expected to fall, and the microcontroller 230 monitors the frequency at which the output signal has its maximum amplitude to determine the resonant frequency of the resonant circuit 155 and identify the cartridge 100.

[0095] Depending on the configuration of resonant circuit 155 and the point at which the output signal is measured, it is possible that the output signal may have a minimum amplitude at resonance. Therefore, peak detect circuit 232 can also measure the minimum amplitude that occurs in the output signal to determine the resonant frequency.

[0096] FIG. 3A shows a schematic diagram of an exemplary cartridge 100 including a resonant circuit 155. The resonant circuit 155 includes a capacitor C1 connected in series with an inductor L1. The resonant circuit 155 is arranged in parallel with the heater 120. The heater is a resistive heater and is therefore represented in FIG. 3A as a resistor RH. The resistance of the heater 120 is 0.69 ohms. The cartridge 100 is connected to a DC voltage source V1, which provides a pulse-width modulated DC voltage across the parallel arrangement of the heater 120 and the resonant circuit 155. The pulse-width modulation is controlled by a microcontroller (not shown). In the illustrated embodiment, the pulse-width modulated DC voltage has an amplitude of 3.6 volts, a period of 10 milliseconds, and a duty cycle of 50 percent. This results in a pulsed current of approximately 5.2 amps through the heater 120.

[0097] When cartridge 100 is connected to DC voltage source V1, current flows only in resistive heater 120. Because resonant circuit 155 is arranged in parallel with heater 120, no current flows in resonant circuit 155, and capacitor C1 in the resonant circuit blocks the DC voltage, effectively acting as an open circuit for the DC voltage. Therefore, power is dissipated only in heater 120 and not in resonant circuit 155, making this arrangement energy efficient.

[0098] DC voltage source V1 can be controlled to control the heating profile applied to a particular cartridge. Once the cartridge 100 is identified according to the procedure described below, a heating profile appropriate for the particular liquid aerosol-forming substrate contained in the cartridge 100 can be applied. For different cartridges, the heating profile can be varied by changing the characteristics of the pulse-width-modulated DC voltage applied to the cartridge. For example, the duty cycle of the pulse-width-modulated DC voltage or the length of time the pulse-width-modulated DC voltage is applied can be varied.

[0099] FIG. 3B shows a schematic circuit diagram of the cartridge 100 of FIG. 3A, in which the cartridge is connected to an AC voltage source or AC signal source V2, which inputs an AC signal to the resonant circuit 155. The AC signal source V2 is controlled by a microcontroller (not shown) and has an amplitude of 1 volt peak. The microcontroller can vary, or sweep, the frequency of the AC signal of the AC signal source V2 to detect resonance and thus determine the identity of the cartridge. The frequency can be swept within a range of 1 megahertz to 13 megahertz, and due to the relatively high frequency used, it has been found that the frequency sweep can be performed within a relatively short period of time, i.e., 240 microseconds. When the frequency of the input AC signal is equal to the natural resonant frequency of the resonant circuit 155, the resonant circuit 155 resonates.

[0100] The resonant circuit 155 is configured to resonate at a predetermined resonant frequency to allow the cartridge 100 to be identified. As presented in equation (1) above, the resonant frequency is a function of the capacitance of the capacitor C1 and the inductance of the inductor L1. In the described embodiment, the predetermined resonant frequency of the resonant circuit 155 is determined by the capacitance of the capacitor C1. Different capacitors with different capacitance values ​​can be used to generate different resonant frequencies for different cartridges. The inductance of the inductor L1 is set to 1 microhenry. Ten different capacitor values ​​taken from the E12 series of capacitor values ​​were used for the capacitor C1 to generate different resonant frequencies. The C1 capacitance values ​​and the resulting resonant frequencies are shown in Table 1. [Table 1] Table 1

[0101] As can be seen from Table 1, the inventors were able to achieve ten different resonant frequencies with sufficient spacing between them to clearly distinguish between ten different cartridges, but of course, more resonant frequencies can be achieved by using more capacitor values.

[0102] FIG. 4 is a frequency vs. voltage graph showing the frequency response of resonant circuit 155 of FIG. 3B. In FIG. 4, there is a frequency response curve for each of the different capacitor values ​​in Table 1. The output signal of resonant circuit 155 was measured at point X in the circuit of FIG. 3B, between resistor R1 and resonant circuit 155. Resistor R1 forms part of a voltage divider with resonant circuit 155, allowing the voltage to be measured at point X. Resonance occurs when the reactance of C1 and the reactance of L1 are equal in magnitude but opposite in phase, so that the two reactances cancel each other. Therefore, at resonance, the impedance of the resonant circuit is at a minimum, and therefore the voltage measured at point X is at a minimum at resonance. For each of the frequency response curves in FIG. 4, it can be seen that a voltage minimum, Vmin, occurs at each of the resonant frequencies in Table 1, corresponding to the different capacitor values ​​used. The voltage minimum occurs over a relatively small section of the overall length of the frequency response curve, and is therefore easily identifiable and detectable.

[0103] The minimum voltage can be detected by a peak detection circuit. The frequency at which the minimum voltage is detected provides an indication of the resonant frequency of the resonant circuit and the identity of the cartridge. Alternatively, the resonant frequency can be determined by configuring the aerosol generating device to detect when the output signal falls below a threshold voltage Vth, shown by the horizontal dashed line in FIG. 4.

[0104] Referring again to FIG. 3B, when AC signal source V2 is connected to cartridge 100 to detect resonance and determine cartridge identification, the AC signal is divided between heater 120 and resonant circuit 155. In contrast to a DC voltage, the AC signal can be passed through capacitor C1 of the resonant circuit. During cartridge identification, the peak current flowing through heater 120 was measured to be approximately 100 milliamps. As noted above, AC signal source V2 has an amplitude of 1 volt peak. Therefore, the power consumed by heater 120 during cartridge identification can be determined from equation (2) below: P=I RMS ×V RMS (2) where P is the power and I RMS is the root mean square current, which is equal to 0.707 times the peak current, and V RMS is the root mean square voltage, which is equal to 0.707 times the peak voltage.

[0105] Furthermore, the energy consumed by the heater 120 during cartridge identification can be determined from equation (3) below: E=P×t (3) where E is energy, P is power, and t is the time or duration of the operation.

[0106] Therefore, based on a peak current of 100 milliamps and a peak voltage of 1 volt, the power consumed by the heater 120 during cartridge identification can be calculated to be 50 milliwatts. Furthermore, based on an actuation time for cartridge identification of 240 microseconds, the energy consumed by the heater 120 during cartridge identification can be calculated to be 12 microjoules. Such a small amount of energy does not heat the heater to any appreciable degree, and thus the energy efficiency of cartridge identification is improved by avoiding energy loss in the heater 120.

[0107] Due to the short period required to perform cartridge identification, cartridge identification can be performed during the voltage-off time of the pulse-width modulated DC voltage used to power the heater. The pulse-width modulated DC voltage of DC voltage source V1 (see FIG. 3A) has a period of 10 milliseconds and a 50 percent duty cycle. Therefore, the voltage-off time is 5 milliseconds, and cartridge identification takes only 240 microseconds, which is sufficient time to perform cartridge identification.

[0108] Figure 5 is a schematic diagram of an exemplary circuit for the aerosol generation system 10 for determining the resonant frequency of the resonant circuit 155 of the cartridge 100. The cartridge 100 is the exemplary cartridge of Figures 3A and 3B. The lower part of the circuit of Figure 5 shows the cartridge with the resonant circuit 155 and heater 120 connected to an AC signal source V2 to identify the cartridge 100. The arrangement and operation of this portion of the circuit of Figure 5 is the same as the circuit shown in Figure 3B and will not be repeated here for brevity.

[0109] 5 further includes a peak detector circuit 232 for detecting the maximum or minimum amplitude of the output signal from the resonant circuit 155. The peak detector circuit 232 is disposed within the aerosol generating device 200 of the aerosol generating system 10. The peak detector circuit 232 includes an operational amplifier U5 for amplifying the signal input to the peak detector circuit 232, a forward-biased diode D1 for half-rectifying the input AC signal, and a capacitor C2 for holding or storing the voltage of the signal received from the diode. The non-inverting input (+) of the operational amplifier serves as the input to the peak detector circuit 232, and the output from the peak detector circuit 232 is taken from the upstream terminal of the capacitor C2, i.e., the terminal of the capacitor C2 connected to the diode D1. The peak detector circuit 232 further includes a resistor R2 having a value of 10 ohms for discharging the capacitor to ground.

[0110] Any suitable operational amplifier may be used. For example, the described embodiment uses an LTC6244 operational amplifier manufactured by Analog Devices of Massachusetts, USA. The operational amplifier U5 is powered by a DC voltage source V3 that supplies 3.1 volts. Two resistors R3 and R4 are provided as part of the negative feedback loop of the operational amplifier, having values ​​of 150 kOhms and 10 kOhms, respectively. The gain of the amplifier can be determined according to equation (4) below: Gain = 1 + R3 / R4 (4)

[0111] In use, the output signal from resonant circuit 155 is taken at point X in the circuit, i.e., the midpoint of the voltage divider formed by resistor R1 and resonant circuit 155, and provided as an input to the non-inverting input of operational amplifier U5 in peak detection circuit 232. The signal is half-wave rectified by diode D1 to form a series of positive pulses, and the voltage of the successive pulses is held or stored by capacitor C2. The output of peak detection circuit 232, i.e., the voltage stored by capacitor C2, is provided to the input of an analog-to-digital converter in microcontroller 230 of aerosol generation device 200, which periodically measures or samples the voltage stored by capacitor C2. Once the voltage is sampled, capacitor C2 is discharged to electrical ground in preparation for taking the next sample.

[0112] The microcontroller 230 samples the output from the peak detector circuit over the period taken to sweep the frequency of the AC signal across the desired frequency range, which in this case is from 1 MHz to approximately 10.6 MHz, taking approximately 240 microseconds. In this manner, the microcontroller 230 obtains a profile of the amplitude of the output signal from the resonant circuit across the sweep frequency range. The samples are analyzed by the microcontroller 230 to determine a minimum value. Because the microcontroller 230 also controls the frequency of the AC signal provided to the AC signal source V2 and the resonant circuit 155 of the cartridge 100, the microcontroller 230 can determine the frequency at which a minimum value in the output from the peak detector circuit 232 is detected. This frequency is the frequency at which resonance occurs within the resonant circuit 155 and is indicative of the cartridge's identity.

[0113] Figures 6A-6C are graphs of voltage versus time illustrating the detection of resonance for different values ​​of capacitor in resonant circuit 155 in cartridge 100 of Figure 5. The graphs show two curves: curve X, which corresponds to the output signal from resonant circuit 155 measured at point X of the circuit of Figure 5, and curve Y, which corresponds to the output from peak detector circuit 232 at point Y of the circuit of Figure 5.

[0114] FIG. 6A shows the output signals from resonant circuit 155 (curve X) and peak detector circuit 232 (curve Y) when a capacitor value of 8.2 nanofarads is used in resonant circuit 155. As shown in Table 1 above, this capacitance value produces a resonant frequency of 1.76 megahertz. The graph in FIG. 6A shows a voltage minimum, V, of curve Y that occurs relatively early, approximately 20 microseconds into the frequency sweep. The voltage minimum indicates the onset of resonance, and the detection time coincides with the resonant frequency being 1.76 megahertz and the frequency being swept over a range from 1 megahertz to approximately 10.6 megahertz over a period of 240 microseconds.

[0115] FIG. 6B shows the output signals from resonant circuit 155 (curve X) and peak detector circuit 232 (curve Y) when a capacitor value of 0.82 nanofarads is used in resonant circuit 155. As shown in Table 1 above, this capacitance value produces a resonant frequency of 5.57 megahertz. The graph in FIG. 6B shows a voltage minimum, V, occurring around the midpoint of curve Y, approximately 120 microseconds into the frequency sweep. The voltage minimum indicates the occurrence of resonance, and the detection time coincides with the resonant frequency being 5.57 megahertz and the frequency being swept over a range from 1 megahertz to approximately 10.6 megahertz over a period of 240 microseconds.

[0116] FIG. 6C shows the output signals from resonant circuit 155 (curve X) and peak detector circuit 232 (curve Y) when a capacitor value of 0.27 nanofarads is used in resonant circuit 155. As shown in Table 1 above, this capacitance value produces a resonant frequency of 9.71 megahertz. The graph in FIG. 6C shows a voltage minimum, V, occurring relatively late in curve Y, approximately 220 microseconds into the frequency sweep. The voltage minimum indicates the onset of resonance, and the detection time coincides with the resonant frequency being 9.71 megahertz and the frequency being swept over a range from 1 megahertz to approximately 10.6 megahertz over a period of 240 microseconds.

[0117] FIG. 7 is a plan view of a printed circuit board 160 having a resonant circuit 155 disposed thereon. The resonant circuit 155 comprises an inductor L1 and a capacitor C2 connected in series. The inductor L1 is formed directly on the printed circuit board 160 as a conductive track. The inductor can be formed by any suitable method, such as by printing a conductive material on the printed circuit board 160 or by etching a copper-clad board to form the pattern for the inductor L1. The inductor L1 has 15 turns (the number of turns has been omitted from FIG. 7 for clarity), and the printed circuit board 160 is double-sided, with half of the turns formed on one side of the printed circuit board 160 and the other half of the turns formed on the other side. Conductive vias 164 connect the ends of the turns printed on each side of the printed circuit board 160. Conductive contact pads 162 are formed on opposite ends of the printed circuit board 160, which can be used to connect the resonant circuit 155 in parallel to both sides of an electric heater and to an AC signal source. One end of inductor L1 is connected to one of the contact pads 162, and the terminal of capacitor C2 is connected to the other contact pad 162. The dimensions of printed circuit board 160 are 9 x 7 x 0.6 mm, so that it can easily fit within the cartridge or mouthpiece of an aerosol generation system.

[0118] FIG. 8 shows a schematic circuit diagram of another exemplary cartridge 300 with another resonant circuit 355. The cartridge 300 is connected to an AC signal source V2 to identify the cartridge 300. The arrangement and operation of the circuit of FIG. 8 is the same as the circuit of FIG. 3B, except that the resonant circuit 355 of FIG. 8 uses two capacitors C1 and C2 in parallel instead of using a single capacitor C1 in the resonant circuit 155. The parallel arrangement of capacitors C1 and C2 serves to improve the frequency response of the resonant circuit 355.

[0119] As mentioned above, all real electronic components have parasitic elements, or unavoidable characteristics, in addition to the intended characteristics of the component. For example, capacitor C1 and inductor L1 in the circuit of Figure 3B have parasitic resistances equivalent to a 0.1 ohm resistor in series with capacitor C1 and a 1 ohm resistor in series with inductor L1, respectively. These parasitic elements result in energy losses in the circuit and therefore should be minimized.

[0120] The inventors have found that using two capacitors C1 and C2 in parallel reduces parasitic elements in the resonant circuit 355. In particular, the capacitor equivalent series resistance is reduced to 0.05 ohms. Furthermore, when capacitors are added in parallel, their capacitances add up. Therefore, by using two identical capacitors in parallel, the inductance can be halved at the same resonant frequency. As a result, a smaller inductor can be used, which saves printed circuit board area. The resonant circuit 355 uses an inductor with an inductance of 0.5 microhenries.

[0121] To produce the same resonant frequency as achieved in the circuit of Figure 3B, the parallel arrangement of capacitors C1 and C2 in resonant circuit 355 of Figure 8 uses two of the capacitor values ​​shown in Table 1 above, respectively, so that the capacitance is doubled as shown in Table 1. The capacitance values ​​and resulting resonant frequencies are shown in Table 2 below. [Table 2] Table 2

[0122] As can be seen from Table 2, the parallel arrangement of two capacitors C1 and C2 achieves the same resonant frequency as Table 1 when using a 0.5 microhenry inductor.

[0123] When connected to a DC voltage source (not shown), cartridge 300 of Figure 8 functions similarly to cartridge 100 of Figure 3A: capacitors C1 and C2 block the DC voltage so that current passes only through heater 320.

[0124] FIG. 9 is a frequency versus voltage graph showing the frequency response of resonant circuit 355 of FIG. 8. In FIG. 9, there is a frequency response curve for each of the different capacitance values ​​from Table 2. The output signal of resonant circuit 355 was measured at point X in the circuit of FIG. 8, i.e., between resistor R1 and resonant circuit 355. The graph is very similar to the graph of FIG. 4 and shows voltage minimums Vmin at the same frequencies as FIG. 4, corresponding to the resonant frequencies of the different capacitance values ​​from Table 2.

[0125] However, Figure 9 shows the improved frequency response of resonant circuit 355 of Figure 8 compared to the frequency response of resonant circuit 155 of Figure 3B shown in Figure 4. That is, the magnitude of the output signal from resonant circuit 355 is improved in resonant circuit 355 compared to resonant circuit 155. As can be seen in Figure 9, the frequency response curve has a lower voltage minimum Vmin than the frequency response curve in Figure 4 for a particular resonant frequency.

[0126] FIG. 10 shows a schematic circuit diagram of another example cartridge 400 with another resonant circuit 455. The cartridge 400 is connected to an AC signal source V2 to identify the cartridge 400. The arrangement and operation of the circuit of FIG. 10 is the same as the circuits of FIGS. 3B and 8, except that the resonant circuit 455 does not use an inductor, and in particular does not use an actual discrete inductor component. Instead, the resonant circuit 455 uses the resonant circuit's parasitic inductance L1 in combination with a capacitor C1 to generate resonance. The parasitic inductance L1 is shown in FIG. 10 as a dotted line to emphasize that it is not an actual component, but instead is a characteristic of the resonant circuit 455.

[0127] The parasitic inductance L1 arises as a result of the geometry of the resonant circuit 455, which forms a half loop or half turn when placed in parallel with the heater 420. The half loop creates a small parasitic inductance L1. As shown in Figure 10, the parasitic inductance is equivalent to an inductance of 10 nanohenries placed in series with the capacitor C1.

[0128] The parasitic inductance is relatively small compared to the inductance of the actual inductor component, and as a result, the resonant frequencies it generates are generally higher than in previous examples. The resonant frequencies are in the range of 1 MHz to 50 MHz, and higher capacitor values ​​are used to generate resonant frequencies within this range. Ten different capacitor values ​​from the E12 series of capacitor values ​​were used for capacitor C1 to generate different resonant frequencies. The C1 capacitance values ​​and resulting resonant frequencies are shown in Table 3 below. [Table 3] Table 3

[0129] As can be seen from Table 3, the inventors were able to achieve 10 different resonant frequencies to distinguish between 10 different cartridges.

[0130] When connected to a DC voltage source (not shown), cartridge 400 of Figure 10 functions similarly to cartridge 100 of Figure 3A: capacitor C1 blocks the DC voltage so that current passes only through heater 420.

[0131] FIG. 11 is a frequency versus voltage graph showing the frequency response of resonant circuit 455 of FIG. 10. In FIG. 11, there is a frequency response curve for each of the different capacitance values ​​from Table 3. The output signal of resonant circuit 355 was measured at point X in the circuit of FIG. 10, i.e., between resistor R1 and resonant circuit 455. For each of the frequency response curves in FIG. 11, it can be seen that a voltage minimum, Vmin, occurs at each of the resonant frequencies from Table 3, corresponding to the different capacitor values ​​used. The voltage minimums occur over a relatively small section of the overall length of the frequency response curve and are therefore easily identifiable and detectable.

[0132] The minimum voltage can be detected by a peak detection circuit. The frequency at which the minimum voltage is detected provides an indication of the resonant frequency of the resonant circuit and the identity of the cartridge. Alternatively, the resonant frequency can be determined by configuring the aerosol generating device to detect when the output signal falls below a threshold voltage Vth, shown by the horizontal dashed line in FIG. 11.

[0133] Figure 12 is a schematic diagram of an exemplary circuit for the aerosol generation system 10 for determining the resonant frequency of the resonant circuit 455 of the cartridge 400. The circuit of Figure 12 is the same as the circuit of Figure 5, except that the cartridge 400 is the exemplary cartridge of Figure 10. The lower part of the circuit of Figure 12 shows the cartridge with the resonant circuit 455 and heater 420 connected to an AC signal source V2 to identify the cartridge 400. The arrangement and operation of this portion of the circuit of Figure 12 is the same as the circuit shown in Figure 10 and will not be repeated here for brevity.

[0134] The circuit of Figure 12 also includes a peak detector circuit 232 for detecting the maximum or minimum amplitude of the output signal from the resonant circuit 455. The arrangement and operation of the peak detector circuit 232 is identical to that of Figure 5 and therefore will not be repeated here for the sake of brevity.

[0135] The microcontroller 230 samples the output from the peak detector circuit over the period taken to sweep the frequency of the AC signal across the desired frequency range, which in this case is from 1 MHz to approximately 40 MHz, taking approximately 1 millisecond. In this manner, the microcontroller 230 obtains a profile of the amplitude of the output signal from the resonant circuit across the sweep frequency range. The samples are analyzed by the microcontroller 230 to determine a minimum value. Because the microcontroller 230 also controls the frequency of the AC signal provided to the AC signal source V2 and the resonant circuit 455 of the cartridge 400, the microcontroller 230 can determine the frequency at which a minimum value in the output from the peak detector circuit 232 is detected. This frequency is the frequency at which resonance occurs within the resonant circuit 455 and is indicative of the cartridge's identity.

[0136] Figures 13A-13C are graphs of voltage versus time illustrating the detection of resonance for different values ​​of capacitor in resonant circuit 455 in cartridge 400 of Figure 12. The graphs show two curves: curve X, which corresponds to the output signal from resonant circuit 455 measured at point X of the circuit of Figure 12, and curve Y, which corresponds to the output from peak detector circuit 232 at point Y of the circuit of Figure 12.

[0137] FIG. 12A shows the output signals from resonant circuit 455 (curve X) and peak detector circuit 232 (curve Y) when a capacitor value of 82 nanofarads is used in resonant circuit 455. As shown in Table 3 above, this capacitance value produces a resonant frequency of 5.6 megahertz. The graph in FIG. 12A shows a voltage minimum, Vmin, occurring relatively early in curve Y, approximately 0.1 milliseconds into the frequency sweep. The voltage minimum indicates the onset of resonance, and the detection time coincides with the resonant frequency being 5.6 megahertz and the frequency being swept over a range from 1 megahertz to approximately 40 megahertz in a 1 millisecond period.

[0138] FIG. 12B shows the output signals from resonant circuit 455 (curve X) and peak detector circuit 232 (curve Y) when a capacitor value of 8.2 nanofarads is used in resonant circuit 455. As shown in Table 3 above, this capacitance value produces a resonant frequency of 17.6 megahertz. The graph in FIG. 12B shows a voltage minimum, Vmin, occurring around the midpoint of curve Y, approximately 0.4 to 0.5 milliseconds into the frequency sweep. The voltage minimum indicates the occurrence of resonance, and the detection time coincides with the resonant frequency being 17.6 megahertz and the frequency being swept over a range from 1 megahertz to approximately 40 megahertz in a 1 millisecond period.

[0139] FIG. 12C shows the output signals from resonant circuit 455 (curve X) and peak detector circuit 232 (curve Y) when a capacitor value of 2.7 nanofarads is used in resonant circuit 455. As shown in Table 3 above, this capacitance value produces a resonant frequency of 30.7 megahertz. The graph in FIG. 12C shows a voltage minimum, Vmin, occurring relatively late in curve Y, approximately 0.7 to 0.8 milliseconds into the frequency sweep. The voltage minimum indicates the onset of resonance, and the detection time coincides with the resonant frequency being 30.7 megahertz and the frequency being swept over a range from 1 megahertz to approximately 40 megahertz in a 1 millisecond period.

[0140] For purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing amounts, quantities, percentages, and the like should be understood in all instances to be modified by the term "about." Also, all ranges include the disclosed maximum and minimum points, and include any intermediate ranges therebetween, which may or may not be specifically recited herein. Accordingly, in this context, the number A is understood as A ± 5 percent. Within this context, the number A may be considered to include a numerical value that is within the typical standard error for the measurement of the property that the number A modifies. In some cases, as used in the appended claims, the number A may deviate by the percentages recited above, provided that the amount by which A deviates does not materially affect the basic and novel property(ies) of the claimed invention. Also, all ranges include the disclosed maximum and minimum points, and include any intermediate ranges therebetween, which may or may not be specifically recited herein.

[0141] 1. A cartridge for an aerosol generating device, comprising an aerosol-forming substrate, an electric heater for heating the aerosol-forming substrate, and a resonant circuit, the resonant circuit being configured to resonate at a predetermined resonant frequency, the predetermined resonant frequency being associated with an identity of the cartridge, and the resonant circuit being connected in parallel with the electric heater. 2. The cartridge of 1, wherein the resonant circuit comprises a capacitor and an inductor. 3. The cartridge according to 2, wherein the capacitor and inductor are connected in series. 4. A cartridge as described in 2 or 3, wherein the predetermined resonant frequency of the resonant circuit is determined by the capacitance of the capacitor, and the predetermined resonant frequency can be changed by changing the capacitance of the capacitor. 5. The cartridge according to any one of 1 to 4, wherein the predetermined resonance frequency is in the range of 10 kHz to 100 MHz, preferably in the range of 100 kHz to 20 MHz, and more preferably in the range of 1 MHz to 11 MHz. 6. The cartridge according to any one of 2 to 5, wherein the capacitance of the capacitor is in the range of 0.1 nF to 10 nF. 7. A cartridge according to any one of 2 to 6, wherein the resonant circuit comprises a plurality of capacitors arranged in parallel, and the combined capacitance of the plurality of capacitors is used to generate resonance. 8. A cartridge according to any one of 2 to 7, wherein the resonant circuit is disposed on a printed circuit board (PCB) and the inductor is formed as a conductive track directly on the PCB. 9. The cartridge described in 1, wherein the resonant circuit comprises a capacitor connected in parallel with the heater, and the resonant circuit is configured to generate resonance using a parasitic inductance of the resonant circuit in combination with the capacitance of the capacitor. 10. The cartridge according to 9, wherein the predetermined resonance frequency is in the range of 100 kHz to 100 MHz, preferably in the range of 1 MHz to 50 MHz. 11. The cartridge according to 9 or 10, wherein the capacitance of the capacitor is in the range of 1 nF to 300 nF. 12. A cartridge described in any one of 1 to 11, wherein the resonant circuit is arranged to be connected to an AC signal source and is configured to resonate when the predetermined resonant frequency is substantially equal to the frequency of the AC signal. 13. An aerosol generating device comprising: a housing configured to receive a cartridge described in any one of 1 to 12, the housing having an electrical connection for electrically connecting to the cartridge; a power source for supplying power to the electric heater of the cartridge; an AC signal source for inputting an AC signal to the resonant circuit of the cartridge; and a control circuit configured to control the supply of power to the electric heater and to controllably vary the frequency of the AC signal supplied to the resonant circuit, wherein the control circuit is arranged to receive an output signal from the resonant circuit, and the control circuit is further configured to determine when resonance occurs in the resonant circuit by detecting when the output signal reaches a predetermined threshold, to determine the frequency at which resonance occurs, and to identify the cartridge based on the determined resonant frequency. 14. The aerosol generating device of claim 13, wherein the control circuit is configured to sweep the frequency of the AC signal over a predetermined frequency range within a predetermined period of time, the predetermined period being 5 milliseconds or less. 15. An aerosol generating device as described in 13 or 14, wherein the peak voltage of the AC signal supplied to the resonant circuit is 2 V or less, preferably 1.5 V or less, and more preferably 1 V or less. 16. An aerosol generation system comprising: a cartridge; and an aerosol generation device, wherein the cartridge comprises an aerosol-forming substrate, an electric heater for heating the aerosol-forming substrate, and a resonant circuit configured to resonate at a predetermined resonant frequency, the predetermined resonant frequency being associated with an identity of the cartridge, and the resonant circuit being connected in parallel with the electric heater; and the aerosol generation device comprises: a housing configured to receive the cartridge, the housing comprising an electrical connection for electrically connecting to the cartridge; and a resonant circuit for supplying power to the electric heater of the cartridge. An aerosol generation system comprising: a power source; an AC signal source for inputting an AC signal to the resonant circuit of the cartridge; and a control circuit configured to control the supply of power to the electric heater and to controllably vary the frequency of the AC signal supplied to the resonant circuit, wherein the control circuit is arranged to receive an output signal from the resonant circuit, and the control circuit is further configured to determine when resonance occurs in the resonant circuit by detecting when the output signal reaches a predetermined threshold, to determine the frequency at which resonance occurs, and to identify the cartridge based on the determined resonant frequency.

Claims

1. A cartridge for an aerosol generating device, comprising: an aerosol-forming substrate; an electric heater for heating the aerosol-forming substrate; a resonant circuit; The resonant circuit is configured to resonate at a predetermined resonant frequency, the predetermined resonant frequency is associated with an identity of the cartridge; and The cartridge, wherein the resonant circuit is connected in parallel with the electric heater.

2. The cartridge of claim 1 , wherein the resonant circuit comprises a capacitor and an inductor.

3. The cartridge of claim 2 , wherein the capacitor and inductor are connected in series.

4. 4. A cartridge according to claim 2 or claim 3, wherein the predetermined resonant frequency of the resonant circuit is determined by the capacitance of the capacitor, and the predetermined resonant frequency can be changed by changing the capacitance of the capacitor.

5. 5. The cartridge according to claim 1, wherein the predetermined resonance frequency is within a range of 10 kHz to 100 MHz.

6. 5. The cartridge according to claim 2, wherein the capacitance of the capacitor is in the range of 0.1 nF to 10 nF.

7. A cartridge according to any one of claims 2 to 6, wherein the resonant circuit comprises a plurality of capacitors arranged in parallel, and the combined capacitance of the plurality of capacitors is used to generate resonance.

8. 8. A cartridge according to claim 2, 3, 4, 6 or 7, wherein the resonant circuit is disposed on a printed circuit board (PCB) and the inductor is formed as a conductive track directly on the PCB.

9. 9. A cartridge according to any one of claims 1 to 8, wherein the resonant circuit is arranged to be connected to an AC signal source and configured to resonate when the predetermined resonant frequency is substantially equal to the frequency of the AC signal.

10. An aerosol generating device, comprising: a housing configured to receive a cartridge according to any one of claims 1 to 9, the housing comprising an electrical connection for electrically connecting to said cartridge; a power source for supplying power to the electric heater of the cartridge; an AC signal source for inputting an AC signal to the resonant circuit of the cartridge; a control circuit configured to control the supply of power to the electric heater and to controllably vary the frequency of the AC signal supplied to the resonant circuit; the control circuit is arranged to receive an output signal from the resonant circuit; and The control circuit determining when resonance occurs within the resonant circuit by detecting when the output signal reaches a predetermined threshold; to determine the frequency at which resonance occurs, and The aerosol generating device is further configured to identify the cartridge based on the determined resonant frequency.

11. 11. The aerosol generating device of claim 10, wherein the control circuit is configured to sweep the frequency of the AC signal over a predetermined frequency range within a predetermined period of time, the predetermined period being 5 milliseconds or less.

12. 12. The aerosol generating device according to claim 10, wherein the peak voltage of the AC signal supplied to the resonant circuit is 2 V or less.

13. An aerosol generating system comprising a cartridge and an aerosol generating device, the cartridge comprising: an aerosol-forming substrate; an electric heater for heating the aerosol-forming substrate; a resonant circuit configured to resonate at a predetermined resonant frequency, the predetermined resonant frequency being associated with an identity of the cartridge, the resonant circuit being connected in parallel with the electric heater; The aerosol generating device comprises: a housing configured to receive the cartridge, the housing comprising an electrical connection for electrically connecting to the cartridge; a power source for supplying power to the electric heater of the cartridge; an AC signal source for inputting an AC signal to the resonant circuit of the cartridge; a control circuit configured to control the supply of power to the electric heater and to controllably vary the frequency of the AC signal supplied to the resonant circuit; the control circuit is arranged to receive an output signal from the resonant circuit; and The control circuit determining when resonance occurs within the resonant circuit by detecting when the output signal reaches a predetermined threshold; to determine the frequency at which resonance occurs, and The aerosol generation system is further configured to identify the cartridge based on the determined resonant frequency.

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