Oscillator circuit

Abstract

Herein is provided an oscillator circuit (100), comprising a resonator (110) having at least a first resonance mode and a second resonance mode, each resonance mode having a respective resonance frequency, wherein the oscillator circuit (100) comprises a switching network (130) to switch between the respective resonance frequencies, and wherein the oscillator circuit (100) is configured to provide an output signal (OUT) of said respective resonance frequency Herein is further provided a sensor comprising an oscillator circuit, and a use of the oscillator circuit or a sensor comprising said oscillator circuit.

Description

[0001] OSCILLATOR CIRCUIT

[0002] TECHNICAL FIELD

[0003] The present disclosure generally relates to the field of sensor applications. The disclosure relates particularly, though not exclusively, to oscillators and oscillator circuits.

[0004] BACKGROUND

[0005] This section illustrates useful background information without admission of any technique described herein representative of the state of the art.

[0006] Sensors are devices which typically detect or measure parameter(s) and respond to them. Sensors may comprise resonators when the so-called gravimetric sensing principle is utilized. In gravimetric sensing the quantities to be sensed change the frequency of the resonant sensing element, and the frequency is thus a proxy for the sensed quantity. The resonators are typically combined with a driving circuit forming an oscillator circuit. Also, quartz crystal microbalance (QCM) technology can be used in sensors.

[0007] Typically, in sensing applications, the resonator’s frequency change is measured and correlated to the measured parameter (property, quantity, phenomenon). However, the measured property may be dependent on another property, such as surrounding atmosphere.

[0008] To provide reliable information, sensors may require several resonators. Typically, at least one resonator to be used in sensing a parameter of interest, as well as further resonator(s) in sensing other parameters. The parameter of interest may be, for example, dependent on said other parameters. SUMMARY

[0009] The appended claims define the scope of protection. Any examples and technical descriptions of apparatuses, products and / or methods in the description and / or drawings not covered by the claims are presented not as embodiments of the invention but as background art or examples useful for understanding the invention.

[0010] It is an object of certain embodiments of the present disclosure to provide a scheme to solve at least one of the problems related to the prior art, or at least to provide an alternative to existing technology. Accordingly, certain disclosed embodiments provide for an ingenious oscillator circuit solving at least one of the problems related to the prior art.

[0011] According to a first example aspect of the present disclosure there is provided an oscillator circuit, comprising a resonator having at least a first resonance mode and a second resonance mode, each resonance mode having a respective resonance frequency, wherein the oscillator circuit comprises a switching network to switch between the respective resonance frequencies, and wherein the oscillator circuit is configured to provide an output signal of said respective resonance frequency.

[0012] In certain embodiments, the oscillator circuit is configured to provide an output signal of said respective resonance frequency according to said switching.

[0013] In certain embodiments, the oscillator circuit comprises only one resonator. In certain embodiments, the oscillator circuit contains one resonator. In certain embodiments, the resonator has at least two resonance modes, each resonance mode having a respective resonance frequency.

[0014] In certain embodiments, the resonator has at least a first resonance mode and a second resonance mode, each resonance mode having a respective resonance frequency, a first resonance frequency and a second resonance frequency. In certain embodiments, the resonator has at least the first resonance frequency and the second resonance frequency that are different from one another (from each other).

[0015] In certain embodiments, the resonator has a plurality of resonance modes. In certain embodiments, each resonance mode has a respective (different) resonance frequency. In certain embodiments, the respective resonance frequencies of the resonance modes are different from one another (each other). In certain embodiments, each of the at least two resonance modes has a respective resonance frequency. In certain embodiments, the respective resonance frequencies are different (differ, unique, distinct) from one another (from each other).

[0016] In certain embodiments, the oscillator circuit comprises a loop amplifier for sustaining oscillation (resonance mode, resonance frequency). In certain embodiments, the oscillator circuit comprises a loop amplifier configured to sustain (maintain, induce) oscillation.

[0017] In certain embodiments, the switching network comprises at least one switch. In certain embodiments, the switching network comprises at least two switches. In certain embodiments, the switching network comprises a plurality of switches. In certain embodiments, the switches of the switching network are connected to each other. In certain embodiments, the switches of the switching network are configured to work in tandem (nonautonomous, together, jointly, in unison).

[0018] In certain embodiments, the switching network comprises a frequency selecting circuitry. In certain embodiments, the frequency selecting circuitry comprises a route without a frequency selecting network.

[0019] In certain embodiments, the frequency selecting circuitry comprises at least one frequency selective network. In certain embodiments, the frequency selecting circuitry comprises at least two frequency selective networks. In certain embodiments, the frequency selecting circuitry comprises at least one frequency selective network, preferably at least two frequency selective networks.

[0020] In certain embodiments, the frequency selecting circuitry comprises a plurality of frequency selective networks. In certain embodiments, the frequency selecting circuitry comprises a plurality of frequency selective networks, one for each respective resonance frequency.

[0021] In certain embodiments, the switching network comprises a switch (or switches) for switching between the frequency selective networks. In certain embodiments, the switching network comprises a switch (or switches) for switching between the plurality of frequency selective networks.

[0022] In certain embodiments, the frequency selecting network is selective for a resonance frequency (one resonance frequency each). In certain embodiments, each frequency selective network is configured to run the oscillator circuit using a (one, specific, predetermined) resonance frequency. In certain embodiments, the switching network comprises a frequency selecting circuitry having at least two frequency selective networks, each frequency selective network being selective for a respective resonance frequency.

[0023] In certain embodiments, the oscillator circuit comprises a switching network to switch between the respective resonance modes (the first resonance mode and the second resonance mode).

[0024] In certain embodiments, the oscillator circuit is configured to provide an output signal for the first resonance frequency, when a first frequency selective network is switched on by the switching network. In certain embodiments, the oscillator circuit is configured to provide another output signal for the second resonance frequency, when a second frequency selective network is switched on by the switching network.

[0025] In certain embodiments, the frequency selecting network (frequency selecting circuitry) comprises a filter. In certain embodiments, the filter is a low-pass filter, a band pass filter, a bandstop filter, or a high-pass filter.

[0026] In certain embodiments, the oscillator circuit comprises a buffer amplifier.

[0027] In certain embodiments, the resonator comprises (has, is) a resonating structure. In certain embodiments, the resonator comprises a plurality of beam elements having a length and a width, wherein the plurality of beam elements are positioned adjacent to each other and adjacent beam elements are mechanically connected to each other. In certain embodiments, the resonator is a stacked (ladder-like structure) beam resonator. In certain embodiments, the stacked beam resonator comprises a plurality of beam elements positioned side-by-side in a plane. In certain embodiments, the plurality of beam elements are positions adjacent to each other in a width direction thereof. In certain embodiments, the plurality of beam elements are positioned adjacent to each other in a width direction of the resonator. In certain embodiments, the beam elements are separated from each other by trenches. In certain embodiments, the beam elements are connected to each other by connection elements.

[0028] In certain embodiments, the resonator is a microelectromechanical systems, MEMS, resonator. In certain embodiments, the resonator is a quartz crystal resonator. In certain embodiments, the resonator is a piezoelectric (piezoelectrically actuated) resonator. In certain embodiments, the resonator comprises at least two resonance modes (at the same time, simultaneously). In certain embodiments, the resonator is configured to resonate in at least two resonance modes. In certain embodiments, the resonator comprises at least a first resonance mode and a second resonance mode (third, fourth, etc...). In certain embodiments, one of the resonance modes (e.g. the first resonance mode) is a main resonance mode. In certain embodiments, one or more of the resonance modes (e.g. the second, third, fourth, etc... resonance mode) is a parasitic resonance mode. In certain embodiments, the resonator comprises more than one parasitic resonance mode.

[0029] In certain embodiments, the resonator is configured to resonate (operate, oscillate, vibrate) in an in-plane resonance mode. In certain embodiments, the resonator is configured to resonate in an out-of-plane resonance mode. In certain embodiments, the resonator is configured to resonate in an in-plane resonance mode and in an out-of-plane resonance mode.

[0030] In certain embodiments, the resonator is configured (adapted) to resonate in a length extensional, LE, resonance mode. In certain embodiments, the resonator is configured to resonate in a flexural resonance mode. In certain embodiments, the resonator is configured to resonate in a width-extensional, WE, resonance mode. In certain embodiments, the resonator is configured to resonate in a differential resonance mode, such as a differential overtone length-extensional resonance mode.

[0031] In certain embodiments, the first (the main) resonance mode is an in-plane resonance mode. In certain alternative embodiments, the first resonance mode is an out-of-plane resonance mode. In certain embodiments, the first resonance mode is a length-extensional resonance mode. In certain alternative embodiments, the first resonance mode is a flexural resonance mode.

[0032] In certain embodiments, the second (or third, fourth, etc..., parasitic) resonance mode is an in-plane resonance mode. In certain alternative embodiments, the second resonance mode is an out-of-plane resonance mode. In certain embodiments, the second resonance mode is a length-extensional resonance mode. In certain alternative embodiments, the second resonance mode is a flexural resonance mode.

[0033] In certain embodiments, the first resonance mode is an in-plane resonance mode and the second (or third, fourth, etc..., parasitic) resonance mode is an out-of-plane resonance mode. In certain embodiments, the first resonance mode is an out-of-plane resonance mode and the second resonance mode is an in-plane resonance mode. In certain embodiments, the first resonance mode and the second resonance mode are in-plane resonance modes. In certain embodiments, the first resonance mode and the second resonance mode are out- of-plane resonance modes.

[0034] In certain embodiments, the first resonance mode is an extensional resonance mode and the second (or third, fourth, etc..., parasitic) resonance mode is a flexural resonance mode. In certain embodiments, the first resonance mode is a flexural resonance mode and the second resonance mode is an extensional resonance mode. In certain embodiments, the first resonance mode and the second resonance mode are extensional resonance modes. In certain embodiments, the first resonance mode and the second resonance mode are flexural resonance modes.

[0035] In certain embodiments, the first resonance mode is an in-plane extensional resonance mode and the second (or third, fourth, etc..., parasitic) resonance mode is an out-of-plane flexural resonance mode. In certain embodiments, the first resonance mode is an out-ofplane flexural resonance mode and the second resonance mode is an in-plane extensional resonance mode. In certain embodiments, the first resonance mode and the second resonance mode are in-plane extensional resonance modes. In certain embodiments, the first resonance mode and the second resonance mode are out-of-plane flexural resonance modes.

[0036] In certain embodiments, the first (main) resonance mode is a length extensional resonance mode and the second (or third, fourth, etc..., parasitic) resonance mode is an out-of-plane flexural mode resonance mode. In certain embodiments, the first resonance mode is a length-extensional resonance mode and the second resonance mode is width extensional resonance mode.

[0037] In certain embodiments, the first resonance mode and the second resonance mode have different respective linear temperature coefficients of frequency, TCFs (from one another, from each other, between each other).

[0038] In certain embodiments, the first resonance mode and the second resonance mode have respective linear temperature coefficients of frequency, TCF, differentiating from one another by a difference of 0.5 ppm / °C - 5 ppm / °C. In certain embodiments, the first resonance mode and the second resonance mode have respective linear temperature coefficients of frequency, TCF, differentiating from one another by at least a difference of 2 ppm / °C. In certain embodiments, one of the at least two resonance modes is a resonance mode having a linear temperature coefficient of frequency, TCF, zero, or essentially zero. In certain embodiments, one of the at least two resonance modes is a main resonance mode having a linear temperature coefficient of frequency, TCF, zero, or essentially zero. In certain embodiments, the first resonance mode has a linear temperature coefficient of frequency, TCF, zero, or essentially zero.

[0039] In certain embodiments, one of the at least two resonance modes is a resonance mode having a linear temperature coefficient of frequency, TCF, different from zero (non-zero). In certain embodiments, one of the at least two resonance modes is a parasitic resonance mode having a linear temperature coefficient of frequency, TCF, different from zero (nonzero). In certain embodiments, the second resonance mode has a linear temperature coefficient of frequency, TCF, different from zero (non-zero).

[0040] In certain embodiments, the oscillator circuit is configured to provide an output signal. In certain embodiments, the oscillator circuit is configured to provide an output signal of said (each) respective resonance frequency. In certain embodiments, the oscillator circuit is configured to provide an output signal of each respective resonance frequency individually.

[0041] In certain embodiments, the oscillator circuit is configured to provide an output signal of said respective resonance frequency, representing a parameter (measurable quantity, physical quantity, phenomenon, property). In certain embodiments, the oscillator circuit is configured to provide output signals of said respective resonance frequencies, each output signal of the respective resonance frequency representing one measured parameter.

[0042] In certain embodiments, the output signal of the oscillator circuit is a resonance frequency reading (value). In certain embodiments, the output signal of the oscillator circuit is a resonance frequency reading, representing a parameter (a value, a number, a quantity, an amount of a parameter).

[0043] In certain embodiments, the oscillator circuit comprises a switching network to switch between the respective resonance frequencies. In certain embodiments, the oscillator circuit comprises a switching network to switch between the periods of the respective resonance frequencies.

[0044] In certain embodiments, the oscillator circuit comprises the switching network to switch between the respective resonance frequencies based on a period of time (based on periods of time, based on different time periods, sequence). In certain embodiments, the oscillator circuit comprises the switching network to switch between the respective resonance frequencies based on a predetermined period of time (predetermined periods of times). In certain embodiments, the oscillator circuit comprises the switching network to switch subsequently between (the periods of) the respective resonance frequencies.

[0045] In certain embodiments, the oscillator circuit is configured such that during a first period of time, the switching network is configured to provide an output signal of the first (main) resonance mode, and subsequently during a second period of time to provide an output signal of the second (parasitic) resonance mode.

[0046] In certain embodiments, the oscillator circuit comprises the switching network to switch between the periods of respective resonance frequencies by an external input. In certain embodiments, the output signal of the oscillator circuit is configured to switch between the periods of respective resonance frequencies by an external input, for selecting the resonance frequency.

[0047] In certain embodiments, the oscillator circuit is configured to implement (accommodate) a sleep period between periods of respective resonance frequencies. In certain embodiments, the oscillator circuit comprises the switching network to switch between the periods of respective resonance frequencies and a sleep period. In certain embodiments, the output signal of the oscillator circuit is configured to switch between the periods of respective resonance frequencies and a sleep period by the switching network. In certain embodiments, during the sleep period the oscillator circuit is configured to provide no output signal. In certain embodiments, in the sleep mode none of the frequency selective networks is switched on.

[0048] In certain embodiments, the oscillator circuit comprises the switching network to switch between the periods of the respective resonance frequencies and a sleep period based on a (predetermined) period of time (based on periods of time, based on different time periods, sequence).

[0049] In certain embodiments, the oscillator circuit comprises the switching network to switch between the respective resonance frequencies (and a sleep period) to measure at least two (different) parameters. In certain embodiments, the oscillator circuit is configured to measure at least two (different) parameters. In certain embodiments, the parameters are different (unique, distinct, not same) from one another. In certain embodiments, a dualfunction oscillator circuit is provided. According to a second example aspect of the present disclosure there is provided a sensor comprising a housing for the sensor, a reference oscillator, and an oscillator circuit according to the first aspect or any of its embodiments.

[0050] In certain embodiments, the housing encapsulates the sensor. In certain embodiments, the housing is configured to enclose (package, protect, capsulate) the sensor. In certain embodiments, the housing is a packaging for the sensor. In certain embodiments, the housing comprises an opening (at least one opening). In certain embodiments, the opening is configured to provide an exchange of substance (gas, liquid) to the sensor.

[0051] In certain embodiments, the housing comprises a plurality of (such as two) openings, to provide a passage for substance through the sensor. In certain embodiments, said substance is gas and / or liquid. In certain embodiments, the substance is particulate matter (solid).

[0052] In certain embodiments, the sensor comprises a reference oscillator circuit. In certain embodiments, the sensor comprises a plurality of reference oscillator circuits. In certain embodiments, the reference oscillator circuit is configured to provide a reference output signal (in comparison to the output signal provided by the oscillator circuit according to the first aspect). In certain embodiments, the reference oscillator circuit is hermetically sealed (no exchange of substance, such as gas or liquid).

[0053] In certain embodiments, the sensor comprises at least one oscillator circuit according to the first aspect (or any of its embodiments). In certain embodiments, the sensor comprises a plurality of oscillator circuits according to the first aspect, such as five, ten or twenty oscillator circuits according to the first aspect (or any of its embodiments).

[0054] In certain embodiments, the sensor comprises a matrix of oscillators (oscillator circuits). In certain embodiments, the sensor is configured to measure at least two (different) parameters (simultaneously, at once, at the same time). In certain embodiments, the sensor is configured to measure a plurality of (different) parameters.

[0055] In certain embodiments, the sensor is a dual-function sensor. In certain embodiments, the sensor is a dual-function gas sensor (configured to measure the gas and another parameter). In certain embodiments, the sensor is a dual- function liquid sensor (configured to measure the liquid and another parameter). In certain embodiments, the sensor is a dual- function biosensor. In certain embodiments, the sensor is a dual-function particulate matter, PM, sensor.

[0056] According to a third example aspect of the present disclosure there is provided a use of an oscillator circuit according to the first aspect or any of its embodiments, or a sensor of the second aspect or any of its embodiments in a gas sensing, a liquid sensing, a biosensing and / or a particulate matter sensing application.

[0057] In certain embodiments, the oscillator circuit comprises a resonator having at least a first resonance mode and a second resonance mode, each resonance mode having a respective resonance frequency (at least a first resonance frequency and a second resonance frequency), wherein the oscillator circuit comprises a switching network to switch between the respective resonance frequencies, and wherein the oscillator circuit is configured to provide an output signal of said resonance frequency.

[0058] In certain embodiments, a dual-function oscillator circuit is provided. In certain embodiments, the first resonance mode (having the first resonance frequency) of the oscillator circuit is used for sensing a first parameter (a parameter of interest), and the second resonance mode ((having the second resonance frequency) of the oscillator circuit is used for sensing a second parameter (another parameter). In certain embodiments, the first and the second parameters are different from one another.

[0059] In certain embodiments, the oscillator circuit is configured to provide the output signal of the first parameter when using the first resonance mode. In certain embodiments, the oscillator circuit is configured to provide the output signal of the second parameter when using the second resonance mode (the same applies for third, fourth... etc resonance modes and parameters).

[0060] In certain embodiments, the first resonance mode of the oscillator circuit is used for said sensing application to sense (detect, measure, determine) a parameter of interest, and the second resonance mode of the oscillator circuit is used for sensing another parameter (the same applies for third, fourth... etc resonance modes and parameters). In certain embodiments, the first resonance mode of the oscillator circuit having the first resonance frequency is used for said sensing application to sense a parameter of interest, and the second resonance mode of the oscillator circuit having the second resonance frequency is used for sensing another parameter. In certain embodiments, the first resonance mode of the oscillator circuit is used for said sensing application to sense a parameter of interest, and the second resonance mode of the oscillator circuit is used for sensing another parameter, wherein the parameter is interest is dependent on the another parameter.

[0061] In certain embodiments, the first resonance mode of the oscillator circuit is used for said sensing application, and the second resonance mode of the oscillator circuit is used for temperature sensing. In certain embodiments, the first resonance mode of the oscillator circuit is used for gas sensing, and the second resonance mode of the oscillator circuit is used for temperature sensing.

[0062] In certain embodiments, the sensor comprises a reference oscillator and at least one oscillator circuit according to the first aspect, or any of its embodiments. In certain embodiments, the reference oscillator has a reference resonance frequency. In certain embodiments, the reference oscillator is configured to provide a reference reading. In certain embodiments, the at least one oscillator circuit is configured to provide a first reading that correlates with one parameter (indicative of one parameter, a first parameter, a parameter of interest), and a second reading that correlates with another parameter (indicative of another parameter, a second parameter). In certain embodiments, the sensor is configured to provide a reference reading, a first reading and a second reading, the first reading and the second reading being indicative of different parameters.

[0063] In certain example embodiments, the reference oscillator is configured to provide a reference reading, indicative of a zero-level gas concentration (no analyte gas). In certain example embodiments, the at least one oscillator circuit is configured to provide a first reading that correlates with a gas concentration (analyte gas provided into the oscillator circuit and into the resonator), and a second reading that correlates with a temperature (since the gas concentration is dependent on said temperature).

[0064] In certain example embodiments, the reference reading is correlated with the first reading and the second reading to provide the gas concentration (the analyte gas).

[0065] In certain embodiments, the sensor comprises a resonator (a sensing device) having at a first resonance frequency that varies with respect to a first parameter (a parameter of interest), and a second resonance frequency that varies with respect to a second parameter (another parameter).

[0066] In certain embodiments, the sensor comprises a control unit. In certain embodiments, the control unit comprises a frequency detector. In certain embodiments, the frequency detector is configured to detect the first resonance frequency and / or the second resonance frequency of the resonator.

[0067] In certain embodiments, the control unit comprises a processing circuitry. In certain embodiments, the processing circuitry is configured to provide (correlate, calculate) a sensor output (data) based on the reference resonance frequency, the reference the first resonance frequency and / or the second resonance frequency. In certain embodiments, the processing circuitry comprises a calibrator (calibration circuit). In certain embodiments, the calibrator is configured to generate sensor calibration data based on the first resonance frequency and / or the second resonance frequency (based on the operation of the resonator). In certain embodiments, the calibrator is configured to calibrate the sensor output (data) based on the reference resonance frequency, the first resonance frequency and / or the second resonance frequency.

[0068] In certain embodiments, the control unit comprises a data storage configured to store initial (calibration) data generated at a time of manufacturing the sensor. In certain embodiments, the data storage is configured to store current sensor data, such as sensor calibration data.

[0069] In certain embodiments, all parts of the sensor are mounted on a driving circuit chip.

[0070] Different non-binding example aspects and embodiments have been illustrated in the foregoing. The embodiments in the foregoing are used merely to explain selected aspects or steps that may be utilized in different implementations. Some embodiments may be presented only with reference to certain example aspects. It should be appreciated that corresponding embodiments may apply to other example aspects as well. In particular, the embodiments described in the context of the first aspect are applicable to each further aspect. Any appropriate combinations of the embodiments may be formed.

[0071] BRIEF DESCRIPTION OF THE FIGURES

[0072] Some example embodiments will be described with reference to the accompanying figures, in which:

[0073] Fig. 1 schematically shows an oscillator circuit according to an example embodiment;

[0074] Fig. 2A schematically shows an oscillator circuit according to an example embodiment;

[0075] Fig. 2B schematically shows the oscillator circuit having according to the example embodiment, switched to another mode; Fig. 3 schematically shows the oscillator circuit according to the example embodiment, switched to sleep mode; and

[0076] Fig. 4 schematically shows a sensor assembly layout according to an example embodiment.

[0077] DETAILED DESCRIPTION

[0078] In the following description, like reference signs denote like elements or steps.

[0079] As used herein, the term resonator or oscillator means a device that works on the principles of resonance or oscillation. A resonator or an oscillator typically is used to provide a signal using a certain resonance frequency. Typically, a resonator or an oscillator is combined with a driving circuit to form an oscillator circuit.

[0080] As used herein, the term parameter means a measurable unit. Synonyms of the term parameter include, but are not limited to, the terms property, quantity, and phenomenon. Herein, a parameter is used to refer to a physical, measurable parameter. Examples of such parameters include, but are not limited to, atmospheric conditions such as gas concentration, moisture / humidity, pressure, or temperature.

[0081] Fig. 1 schematically shows an oscillator circuit 100 according to an example embodiment. As shown in Fig. 1 , the oscillator circuit 100 comprises one resonator 110. In certain embodiments, the resonator 110 has at least a first resonance mode and a second resonance mode, each resonance mode having a respective resonance frequency. The oscillator circuit 100 comprises a switching network 130 to switch between the respective resonance frequencies. The oscillator circuit 100 is configured to provide an output signal OUT-1 of said respective resonance frequency.

[0082] In certain embodiments, an output of the resonator 110 is coupled via the loop amplifier 121 to the switching network 130. In certain embodiments, the switching network 130 is coupled to the input of the resonator 110. In certain embodiments, buffer amplifier 122 is coupled to an output of the oscillator circuit 100. In certain embodiments, the buffer amplifier 122 is configured to start oscillation. In certain embodiments, the buffer amplifier 122 is configured to support oscillation (resonance mode(s)). In certain embodiments, the buffer amplifier 122 is implemented on an integrated circuit (not shown). In certain alternative embodiments, the buffer amplifier 122 is implemented based on discrete circuit (not shown). In certain embodiments, the resonator 110 having at least a first resonance mode and a second resonance mode, has at least the first respective resonance frequency and the second respective resonance frequency that are different from one another. In certain embodiments, the resonator 110 has more than two, a plurality of, resonance modes. In certain embodiments, each resonance mode has a respective resonance frequency, different from the other resonance frequencies.

[0083] In certain embodiments, one of the resonance modes (e.g. the first resonance mode) is a main resonance mode, and one or more of the resonance modes (e.g. the second, third, fourth, etc... resonance mode) is a parasitic resonance mode.

[0084] In certain embodiments, the first (the main) resonance mode is an in-plane lengthextensional, LE, resonance mode, and the second (or third, fourth, etc..., parasitic) resonance mode is an out-of-plane flexural resonance mode. In certain alternative embodiments, the first resonance mode is a length-extensional resonance mode and the second resonance mode is width extensional resonance mode.

[0085] In certain embodiments, the first resonance mode and the second resonance mode have different respective linear temperature coefficients of frequency, TCF, from one another. In certain embodiments, the respective linear TCFs differentiate from one another by at least a difference of 2 ppm / °C. In certain embodiments, the first resonance mode has the linear temperature coefficient of frequency, TCF, zero or essentially zero, and the second resonance mode has the linear temperature coefficient of frequency, TCF, different from zero (non-zero).

[0086] As shown in Fig. 1 , in certain embodiments, the switching network 130 comprises two switches 131 , 132. In certain embodiments, the switching network 130 is configured to control the switches 131 , 132. In certain embodiments, the switches 131 , 132 are configured to operate in unison.

[0087] In certain embodiments, the switching network 130 comprises a frequency selecting circuitry. In certain embodiments, the switches 131 , 132 are configured to switch between the modes of frequency selecting circuitry.

[0088] In certain embodiments, the frequency selecting circuitry comprises a route 140 without a frequency selecting network. In certain embodiments, the frequency selecting circuitry comprises a frequency selective network 140’. In certain embodiments, the resonator 110 is configured to operate in a first resonance frequency, when operated (driven, used) via the route 140 without a frequency selecting network. In certain embodiments, the frequency selecting network 140’ is configured to operate in (via, by, using) a second resonance frequency. In certain embodiments, the first resonance frequency and the second resonance frequency are different from one another (not equal).

[0089] In certain embodiments, the frequency selecting circuitry is configured to force (make) the resonator 110 to oscillate at a desired frequency. In certain embodiments, the frequency selective network 140’ is configured to eliminate unwanted resonance mode(s). In certain embodiments, the frequency selective network 140’ is configured to eliminate the first resonance mode of the resonator 110. This prevents the resonator 110 from oscillating (resonating, locking into) at undesired resonance frequencies.

[0090] By way of an example, in certain embodiments, the resonator 110 is configured to operate in a main (first) resonance mode, when operated via the route 140 without a frequency selecting network. When the switches 131 , 132 switch to the other mode of the frequency selective circuitry, in certain embodiments, the resonator 110 is configured to operate in a parasitic (second) resonance mode, when operated by frequency selecting network 140’. In this example embodiment, the frequency selective network 140’ is configured to kill the main resonance mode of the resonator 110.

[0091] Fig. 2A schematically shows an oscillator circuit 100 according to an example embodiment. As shown in Fig. 2A, in certain embodiments, the switching network 130 comprises at least two frequency selective networks 141 , 142. In certain alternative embodiments, the switching network 130 comprises a frequency selecting circuitry, comprising a plurality of frequency selective networks 141 , 142.

[0092] In certain embodiments, the switching network 130 comprises at least two frequency selective networks 141 , 142 to force the resonator 110 to oscillate at a desired frequency. In certain embodiments, each frequency selective network 141 , 142 is configured to eliminate (kill, remove) unwanted resonance mode(s). This prevents the resonator 110 from oscillating at undesired resonance frequencies. In certain embodiments, the frequency selective networks 141 , 142 are selectively activated (during switching by the switching network 130). In certain embodiments, the frequency selecting network 141 is configured to operate in (via, by, using) a first resonance frequency. In certain embodiments, the frequency selecting network 142 is configured to operate in a second resonance frequency. In certain embodiments, the first resonance frequency and the second resonance frequency are different from one another (not equal). In certain embodiments, the frequency selective network 141 is configured to eliminate the second resonance mode of the resonator 110. In certain embodiments, the frequency selective network 142 is configured to eliminate the first resonance mode of the resonator 110.

[0093] In an embodiment shown in Fig. 2A, the oscillator circuit 100 is configured to provide the output signal OUT-1 for the first resonance frequency, as the first frequency selective network 141 is switched on by the switching network 130.

[0094] Fig. 2B schematically shows the oscillator circuit according to the example embodiment, switched to another mode. In this embodiment, the oscillator circuit 100 is configured to provide another output signal OUT-2 for the second resonance frequency, as the second frequency selective network 142 is switched on by the switching network 130.

[0095] In certain embodiments, the oscillator circuit 100 comprises the switching network 130 to switch between the respective resonance frequencies (the respective frequency selective networks 141 , 142) based on a predetermined time period sequence. In certain embodiments, a time division oscillator circuit is provided.

[0096] In certain embodiments, the oscillator circuit 100 is configured to operate alternately in the first resonance mode (the first resonance frequency) and in the second resonance mode (the second resonance frequency). In certain embodiments, the switching network 130 is configured to switch between the respective resonance frequencies alternately.

[0097] In an example embodiment, the switching network 130 is configured to switch between the periods of the respective resonance frequencies such that the first respective resonance frequency is used for 50-100 ms time period, followed by the second respective resonance frequency is used for another 50-100 ms time period. In this example embodiment, the oscillator circuit 100 is switched off briefly in between the first and the second resonance frequencies.

[0098] In certain embodiments, the switching network 130 is configured to switch between the periods of the respective resonance frequencies such that the first respective resonance frequency is used for 50-100 ms time period, followed by the second respective resonance frequency is used for another 500-600 ms time period. In this example embodiment, the oscillator circuit 100 is switched off for an extended period of time in between the first and the second resonance frequencies.

[0099] In certain alternative embodiments, the oscillator circuit 100 comprises the switching network 130 to switch between the periods of the respective resonance frequencies (the respective frequency selective networks 141 , 142) based by an external input, such as an operator selecting the resonance frequency.

[0100] Fig. 3 schematically shows the oscillator circuit according to the example embodiment, switched to sleep mode. In certain embodiments, the oscillator circuit 100 is configured to implement a sleep period between the periods of the respective resonance frequencies.

[0101] In the embodiment shown in Fig. 3, the oscillator circuit 100 is configured to provide no output signal OUT, as the switching network 130 is switched to a sleep mode (sleep position, switched off) and none of the frequency selective networks 141 , 142 is switched on. This is illustrated in Fig. 3 as OUT being crossed out. In certain embodiments, the oscillator circuit 100 comprises the switching network to switch between the periods of the respective resonance frequencies and a sleep period based on a predetermined sequence, or based by an external input.

[0102] In certain embodiments, the resonator comprises a strong first (main) resonance mode and a weak, or at least weaker, second (parasitic) resonance mode. In certain embodiments, the second resonance mode is too weak to lock (the equivalent series resistance, ESR, is too high to successfully lock). In this embodiment, the respective resonance frequency of the second resonance mode is determined by (via, using) measuring an impedance around the second resonance mode and by detecting a resonance peak. In certain embodiments, the resonator 110 having at least the first resonance mode and the second resonance mode, each resonance mode having a respective resonance frequency, comprises two terminals (not shown). In certain embodiments, the oscillator circuit 100 further comprises a circuit switching system. In certain embodiments, the circuit switching system is configured to disconnect the resonator 110 from the oscillator circuit, and connect a separate integrated circuit to the resonator terminals (not shown). In certain embodiments, the separate integrated circuit is configured to measure the second resonance frequency. Fig. 4 schematically shows a sensor assembly layout according to an example embodiment. As shown in Fig. 4, a sensor 200 comprises a housing 210 for the sensor 200. The sensor further comprises a reference oscillator 201 , and an oscillator circuit 100 according to the first aspect, or any of its embodiments.

[0103] In certain embodiments, the housing 210 is configured to package the sensor 200. In certain embodiments, the housing 210 comprises at least one opening 211. In certain embodiments, the at least one opening 211 is configured to provide an exchange of substance in and out of the sensor 200. The substance is gas according to certain embodiments. The substance is liquid according to certain other embodiments. The substance is particulate matter according to yet other embodiments. In certain embodiments, the housing 210 comprises a plurality (such as two) openings 211 , to provide a passage for substance through the sensor housing 210 (not shown).

[0104] In certain embodiments, the reference oscillator circuit 201 is configured to provide a reference output signal (in comparison to the output signal provided by the oscillator circuit 100). As shown in Fig. 4, in certain embodiments, the reference oscillator circuit 201 is sealed, enabling no exchange of substance therein (or thereout).

[0105] In certain embodiments, the oscillator circuit 100 comprises at least one opening 150 each. In certain embodiments, the at least one opening 150 is configured to provide an exchange of substance in and out of the oscillator circuit 100. In certain embodiments, the at least one opening 150 is configured to provide an exchange of substance to the surface of the resonator 110. The substance is gas according to certain embodiments, or liquid according to other embodiments, or particulate matter according to yet other embodiments. In certain embodiments, the oscillator circuit 100 comprises a plurality (such as two) openings 150, to provide a passage for substance through the oscillator circuit 100 (or along the surface of the resonator 110).

[0106] In certain embodiments, the sensor comprises a control unit 202. In certain embodiments, the oscillator circuit(s) 100 is / are coupled to the control unit 202. In certain embodiments, the control unit 202 comprises a frequency detector, a processing circuitry having a calibrator, a data storage (not shown). In certain embodiments, the control unit 202 is configured to provide the sensor output data OUT. In certain embodiments, all components of the sensor 200 are coupled to (attached to) driving circuit chip (not shown). In certain embodiments, a dual-function sensor 200 comprising said oscillator circuit 100 is provided. In certain embodiments, the oscillator circuit 100 comprises the switching network to switch between the periods of the respective resonance frequencies, representing one parameter each. In certain embodiments, the oscillator circuit 100 or the sensor 200 comprising said oscillator circuit 100 are configured to measure at least two parameters (at the same time, at once, simultaneously). In certain embodiments, the at least two parameters are different from one another.

[0107] In certain embodiments, the first resonance mode of the oscillator circuit 100 is used for sensing (measuring, detecting, determining) a first parameter, and the second resonance mode is used for sensing a second parameter. In certain embodiments, the oscillator circuit 100 comprises the switching network 130 to switch between the periods of the respective resonance frequencies (and the sleep period) to measure at least two different parameters. In certain embodiments, the oscillator circuit is configured to provide output signals of said respective resonance frequencies, each output signal representing a measured parameter.

[0108] In certain embodiments, the oscillator circuit 100 or a sensor 200 comprising said oscillator circuit 100 is used in environmental sensing application. In certain embodiments, the oscillator circuit 100 or a sensor 200 comprising said oscillator circuit 100 is used in a gas sensing, a liquid sensing, a biosensing and / or a particulate matter sensing application. In certain embodiments, the first resonance mode of the oscillator circuit 100 is used for said sensing application, and the second resonance mode of the oscillator circuit 100 is used for temperature sensing.

[0109] In certain embodiments, the first resonance mode having the first resonance frequency is used for said sensing application to sense a parameter of interest (a first parameter), and the second resonance mode having the second resonance frequency is used for sensing another parameter (a second parameter), wherein the parameter is interest is dependent on the another parameter. Accordingly, in certain embodiments, the same is applied to the third, fourth... etc parameters and resonance modes.

[0110] In an example embodiment, the sensor 200 is a gravimetric sensor configured to measure at least two parameters. Gravimetric sensors may be used for example in gas sensing, liquid sensing, biosensing or particulate matter (PM) applications. Gas sensing is merely used herein as an example. In this example embodiment, the sensor 200 is a gas sensor configured to measure gas concentration and temperature (two different parameters). In certain embodiments, the first resonance mode of the oscillator circuit 100 is used for gas sensing, and the second resonance mode of the oscillator circuit 100 is used for temperature sensing.

[0111] In gravimetric gas sensing, molecules of an analyte gas typically adhere to a surface of a resonator, depending on the concentration of the analyte gas and the material on the resonator. This results in a change in the mass of the resonator. As a result of the resonator mass changing, the frequency of the resonator changes, too. The change in resonator frequency correlates with the concentration of the analyte gas. However, the concentration of a gas is typically dependent on the temperature. Typically, in order to reliably determine the gas concentration, a separate temperature sensor is needed.

[0112] In an example embodiment, a resonator having a first resonance mode (main resonance mode) having a linear TCFs of essentially zero, or close to zero, such as TCF1 = 0 ppm / °C is provided. In this example embodiments, the first resonance mode has a first resonance frequency of approximately 32 MHz. In this example embodiment, the resonator has a second resonance mode (parasitic resonance mode) having a linear TCFs of other than zero, such as approximately TCF2 = -10 ppm / °C. In this example embodiments, the second resonance mode has a second resonance frequency of approximately 110 MHz.

[0113] In an example embodiment, the first resonance mode is used in gas sensing. In an example embodiment, the second resonance frequency is used as a proxy for the temperature sensing. According to an example embodiment, utilization of both said first and resonance modes of a one, single resonator eliminates the need for a separate temperature sensor. In an example embodiment, the oscillator circuit (the resonator of said oscillator circuit) is configured to run in two modes.

[0114] In an example embodiment, the oscillator circuit is configured to operate (the switching network is configured to switch) alternately (sequentially) in the first resonance mode and the second resonance mode. In an example embodiment, a time division oscillator circuit is provided.

[0115] In the following, an example cycle of the time division oscillator circuit is provided. In an example embodiment, the oscillator circuit is configured to operate with the first (main) resonance mode having the first resonance frequency a period of to ... t1. In an example embodiment, the oscillator circuit is configured to sleep a period of t1 ... t2 (be in sleep mode, switched off, deactivated, provide no output signal). In an example embodiment, the oscillator circuit is configured to operate with the second (parasitic) resonance mode having the second resonance frequency a period of t2 ... t3. In an example embodiment, the oscillator circuit is configured to sleep a period of t3 ... t4. In an example embodiment, the preceding cycle is repeated (sequentially, continuously, by an external input).

[0116] In an example embodiment, the output signal comprises a mixture (a sequence) of output signals. In an example embodiment, the mixture of output signals comprises signals for the first resonance frequency and the second resonance frequency. In an example embodiment, the first resonance frequency provides a signal representing gas concentration. In an example embodiment, the second resonance frequency provides a signal representing temperature.

[0117] Fig. 4 provides a schematical sensor layout to accommodate this example embodiment. As shown in Fig. 4, in certain embodiments, the sensor 200 comprises a plurality of oscillator circuits 100. In certain embodiments, the sensor 200 comprises a matrix of oscillators circuits 100. As shown in Fig. 4, the reference oscillator 201 comprises no opening, enabling no gas to enter therein. In an embodiment, the reference oscillator 201 is configured to provide a reference frequency for the gas sensor 200. As shown in Fig. 4, the gas sensor 200 comprises a plurality of oscillator circuits 100, each having a respective opening 150 to allow gas to enter therein. In an example embodiment, each oscillator circuit 100 is used to measure a concentration of a different component of the gas, such as oxygen concentration, hydrogen concentration, and / or nitrogen concentration.

[0118] In this example embodiment, the resonator 110 of the oscillator circuit 100 is a gravimetric resonator. In certain embodiments, the resonator 110 comprises a layer of absorbent material on its surface (not shown). In certain embodiments, the layer of absorbent material is a sensing film comprising a sensing material that interacts with a (target, analyte, measured) gas.

[0119] In certain embodiments, the layer of absorbent material is selective for a certain type of gas. In this example embodiment, the layer of absorbent material comprises (contains) palladium or platinum. In certain embodiments, the layer of absorbent material is palladium or platinum. In certain embodiments, the sensing is based on a selective absorption of the gas onto the layer of absorption material. The oscillator circuit 100 comprising the resonator 110 having the layer of absorbent material of palladium or platinum is selective for sensing the concentration of hydrogen gas, according to an example embodiment.

[0120] In certain embodiments, a resonator (a gas sensing device) comprises a first resonance frequency that varies with adsorbed gas (chemicals, molecules) and a second resonance frequency that varies with temperature.

[0121] In this example embodiment, each of the resonators 110 in the plurality of oscillator circuits 100 comprises a respective (different) layer of absorption material on the resonator 110 surface. In this example embodiment, the gas sensor 200 is configured to measure concentrations of various (different) types of gases. In this example embodiment, each oscillator circuit 100 is selective for a certain type of gas (due to each having a different respective layer of absorption material on the resonator surface).

[0122] In certain embodiments, the control unit 202 is configured to receive the output signals of the oscillator circuits 100. In certain embodiments, the control unit 202 is configured to receive the output signal of the reference oscillator 201 .

[0123] In certain embodiments, the control unit 202 comprises a frequency detector configured to detect the resonance frequencies of each of the oscillator circuits 100 and the reference resonance frequency of the reference oscillator 201. In certain embodiments, the control unit 202 comprises a processing circuitry configured to provide (correlate, calculate) a sensor output data OUT based on the resonance frequencies and the reference resonance frequency (that are detected by the frequency detector).

[0124] Without limiting the scope and the interpretation of the patent claims, certain technical effects of one or more of the example embodiments disclosed herein are listed in the following. A technical effect is providing a dual-function oscillator circuit in one package, capable of different functions.

[0125] By using an oscillator or a resonator resonating in two respective, different resonance frequencies (resonance modes), the dual-function oscillator circuit is achieved. One frequency of the oscillator is used for detecting a first parameter (e.g. a parameter of interest), such as gas concentration. The other frequency of the oscillator is used for detecting a second parameter, such as temperature. Therefore, a need for separate resonator (device) for sensing the second parameter, such as temperature, is omitted. It should be noted that there are typically multiple resonance modes in a resonator. In a typical case, one wants to suppress all other modes than the main mode as much as possible to ensure oscillation in the main mode. However, in the instant case an ingenious new purpose for the other resonance modes of the resonator (that are unwanted in a conventional situation) has been found.

[0126] Due to the oscillator’s specific frequency-vs-temperature behavior, the main resonance mode exhibits a flat f-vs-T characteristic (linear temperature coefficient of frequency, TCF, is close to zero), whilst the secondary (parasitic) resonance mode exhibits non-flat f-vs-T characteristic (linear temperature coefficient of frequency, TCF, is different than zero). The secondary (parasitic) resonance mode can be used as a proxy for the second parameter sensing, all within one package using a single oscillator. Thus, a further technical effect is enabling utilization of respective, different resonance modes of a single oscillator in detecting different parameters, such as gas concentration and temperature using only one oscillator.

[0127] Further technical effects include reduced complexity, and reduced costs of the oscillator circuit. This is due to removing the need for a second sensor, such as a separate temperature sensor for gas sensing applications. A further technical effect is providing a simplified solution and simplifying the manufacturing process of such, whilst achieving the same capabilities as previous oscillator circuits. A further technical effect is a small footprint of the oscillator circuit system.

[0128] Various embodiments have been presented. It should be appreciated that in this document, words comprise, include, and contain are each used as open-ended expressions with no intended exclusivity.

[0129] The foregoing description has provided by way of non-limiting examples of particular implementations and embodiments a full and informative description of the best mode presently contemplated by the inventors for carrying out the invention. It is however clear to a person skilled in the art that the invention is not restricted to details of the embodiments presented in the foregoing, but that it can be implemented in other embodiments using equivalent means or in different combinations of embodiments without deviating from the characteristics of the invention. Furthermore, some of the features of the afore-disclosed example embodiments may be used to advantage without the corresponding use of other features. As such, the foregoing description shall be considered as merely illustrative of the principles of the present invention, and not in limitation thereof. Hence, the scope of the invention is only restricted by the appended patent claims.

Claims

CLAIMS1 . An oscillator circuit (100), comprising a resonator (110) having at least a first resonance mode and a second resonance mode, each resonance mode having a respective resonance frequency, wherein the oscillator circuit (100) comprises a switching network (130) to switch between the respective resonance frequencies, and wherein the oscillator circuit (100) is configured to provide an output signal (OUT) of said respective resonance frequency.

2. The oscillator circuit (100) of claim 1 , wherein the switching network (130) comprises a frequency selecting circuitry.

3. The oscillator circuit (100) of claim 2, wherein the frequency selecting circuitry comprises at least one frequency selective network (141 ), preferably at least two frequency selective networks (141 / 142).

4. The oscillator circuit (100) of claim 3, wherein the frequency selecting network (141 / 142) comprises a filter, such as a low-pass filter, a band pass filter, a bandstop filter, or a high-pass filter.

5. The oscillator circuit (100) of any preceding claim, wherein the first resonance mode and the second resonance mode have different respective linear temperature coefficients of frequency, TCFs.

6. The oscillator circuit (100) of claim 5, wherein the first resonance mode and the second resonance mode have respective linear temperature coefficients of frequency, TCF, differentiating from one another by at least a difference of 2 ppm / °C.

7. The oscillator circuit (100) of any preceding claim, wherein the first resonance mode has a linear temperature coefficient of frequency, TCF, zero, or essentially zero.

8. The oscillator circuit (100) of any preceding claim, wherein the second resonance mode has a linear temperature coefficient of frequency, TCF, different from zero.

9. The oscillator circuit (100) of any preceding claim, wherein the oscillator circuit (100) comprises the switching network (130) to switch between the respective resonance frequencies based on a period of time.

10. The oscillator circuit (100) of any preceding claim, wherein the oscillator circuit (100) comprises the switching network (130) to switch between the respective resonance frequencies by an external input.11 . The oscillator circuit (100) of any preceding claim, wherein the oscillator circuit (100) comprises the switching network (130) to switch between the respective resonance frequencies and a sleep period.

12. A sensor, comprising a housing for the sensor, a reference oscillator circuit, and an oscillator circuit (100) of any of claims 1-11.

13. Use of an oscillator circuit (100) of any of claims 1-11 or a sensor of claim 12 in a gas sensing, a liquid sensing, a biosensing and / or a particulate matter sensing application.

14. The use of claim 13, wherein the first resonance mode of the oscillator circuit (100) is used for said sensing application to sense a parameter of interest, and the second resonance mode of the oscillator circuit (100) is used for sensing another parameter.

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