Patent Publication Number: US-11389091-B2

Title: Methods for automated response to detection of an analyte using a non-invasive analyte sensor

Description:
FIELD 
     This disclosure relates generally to apparatus, systems and methods of non-invasively detecting an analyte via spectroscopic techniques using non-optical frequencies such as in the radio or microwave frequency bands of the electromagnetic spectrum. More specifically, this disclosure relates to non-invasive analyte detection and automated response based on detection of the one or more analytes. 
     BACKGROUND 
     There is interest in being able to detect and/or measure an analyte within a target. One example is measuring glucose in biological tissue. In the example of measuring glucose in a patient, current analyte measurement methods are invasive in that they perform the measurement on a bodily fluid such as blood for fingerstick or laboratory-based tests, or on fluid that is drawn from the patient often using an invasive transcutaneous device. There are non-invasive methods that claim to be able to perform glucose measurements in biological tissues. However, many of the non-invasive methods generally suffer from: lack of specificity to the analyte of interest, such as glucose; interference from temperature fluctuations; interference from skin compounds (i.e. sweat) and pigments; and complexity of placement, i.e. the sensing device resides on multiple locations on the patient&#39;s body. 
     SUMMARY 
     This disclosure relates generally to apparatus, systems and methods of non-invasively detecting an analyte via spectroscopic techniques using non-optical frequencies such as in the radio or microwave frequency bands of the electromagnetic spectrum. A non-invasive analyte sensor described herein includes at least one transmit antenna (which may also be referred to as a transmit element) that functions to transmit a generated transmit signal in a radio or microwave frequency range of the electromagnetic spectrum into a target containing an analyte of interest, and at least one receive antenna (which may also be referred to as a receive element) that functions to detect a response resulting from transmission of the transmit signal by the transmit antenna into the target. 
     The transmit and receive antennas are decoupled from one another which helps to improve the detection capability of the non-invasive analyte sensor. The decoupling between the transmit and receive antennas can be achieved using any one or more techniques that causes as much of the signal as possible that is transmitted by the transmit antenna to enter the target and that minimizes or even eliminates the amount of electromagnetic energy that is directly received by the receive antenna from the transmit antenna without traveling into the target. The decoupling can be achieved by one or more intentionally fabricated configurations and/or arrangements between the transmit and receive antennas that is sufficient to decouple the transmit and receive antennas from one another. In one non-limiting embodiment, the decoupling can be achieved by the transmit antenna and the receive antenna having intentionally different geometries from one another. Intentionally different geometries refers to different geometric configurations of the transmit and receive antennas that are intentional, and is distinct from differences in geometry of transmit and receive antennas that may occur by accident or unintentionally, for example due to manufacturing errors or tolerances. 
     Another technique to achieve decoupling of the transmit and receive antennas is to use an appropriate spacing between each antenna, depending upon factors such as output power, size of the antennas, frequency, and the presence of any shielding, so as to force a proportion of the electromagnetic lines of force of the transmit signal into the target so they reach the analyte, thereby minimizing or eliminating as much as possible direct receipt of electromagnetic energy by the receive antenna directly from the transmit antenna without traveling into the target. This technique helps to ensure that the response detected by the receive antenna is measuring the analyte and is not just the transmitted signal flowing directly from the transmit antenna to the receive antenna. In one embodiment, the sensor can use a first pair of transmit and receive antennas that have a first spacing therebetween, and a second pair of transmit and receive antennas that have a second spacing therebetween that differs from the first spacing. 
     The techniques described herein can be used to detect the presence of the analyte of interest, as well an amount of the analyte or a concentration of the analyte within the target. The techniques described herein can be used to detect a single analyte or more than one analyte. The target can be any target, for example human or non-human, animal or non-animal, biological or non-biological, that contains the analyte(s) that one may wish to detect. For example, the target can include, but is not limited to, human tissue, animal tissue, plant tissue, an inanimate object, soil, a fluid, genetic material, or a microbe. The analyte(s) can be any analyte, for example human or non-human, animal or non-animal, biological or non-biological, that one may wish to detect. For example, the analyte(s) can include, but is not limited to, one or more of blood glucose, blood alcohol, white blood cells, or luteinizing hormone. The presence or amount of the analyte can be responded to by controlling a flow, for example controlling the introduction of one or more compounds into the medium subjected to detection, controlling flow of the medium to start, stop, increase or decrease its flow, or directing flow of the medium, for example to change flow paths. In an embodiment, the analyte can be blood glucose and the response can be operation of an insulin pump to control the supply of insulin based on the blood glucose level. 
     In one embodiment, an analyte sensing and response system includes a sensor configured to detect at least one analyte of interest in a medium. The sensor includes an antenna array having at least one transmit antenna and at least one receive antenna, wherein the at least one transmit antenna and the at least one receive antenna are less than 95% coupled to one another, a transmit circuit that is electrically connectable to the at least one transmit antenna, the transmit circuit is configured to generate a transmit signal to be transmitted by the at least one transmit antenna, the transmit signal is in a radio or microwave frequency range of the electromagnetic spectrum, and a receive circuit that is electrically connectable to the at least one receive antenna, the receive circuit is configured to receive a response detected by the at least one receive antenna resulting from transmission of the transmit signal by the at least one transmit antenna into the medium. The system further includes a controller configured to direct an action affecting a level of the at least one analyte of interest in the medium, based on detection of the at least one analyte by the sensor. 
     In an embodiment, the action includes controlling a valve to increase or decrease a flow of the analyte of interest into the medium. In an embodiment, the action includes controlling a valve to increase or decrease flow into the medium of a compound interacting with the analyte of interest in the medium. In an embodiment, the system includes a mechanical device that is connected to and controlled by a signal from the controller, and the mechanical device is configured to control a level of the at least one analyte of interest in the medium based on the signal received from the controller. In an embodiment, the system includes a heating or cooling device that is connected to and controlled by a signal from the controller, and the heating or cooling device is configured to affect a temperature of the medium. In an embodiment, the analyte of interest is glucose, and the action includes operating an insulin pump based on detection of the glucose by the sensor. 
     In an embodiment, the controller is included in a device separate from the sensor. In an embodiment, the device separate from the sensor is configured to receive information regarding the analyte from the sensor. 
     In an embodiment, the information regarding the analyte is a presence or amount of the analyte, and the controller is further configured to determine the action based on the presence or amount of the analyte. In an embodiment, the information regarding the analyte includes the action to be directed by the controller. In an embodiment, the system further includes a remote server, and the remote server is configured to receive information regarding the analyte from the sensor and to communicate a command to the controller. 
     In another embodiment, an analyte sensing and response system includes a sensor configured to detect at least one analyte of interest in a medium includes a sensor housing and a decoupled detector array attached to the sensor housing. The decoupled detector array has at least one transmit element and at least one receive element, and the at least one transmit element and the at least one receive element are less than 95% coupled to one another. The at least one transmit element consists of a strip of conductive material having at least one lateral dimension thereof greater than a thickness dimension thereof, and the strip of conductive material of the at least one transmit element is disposed on a substrate. The at least one receive element consists of a strip of conductive material having at least one lateral dimension thereof greater than a thickness dimension thereof, and the strip of conductive material of the at least one receive element is disposed on a substrate. The sensor further includes a transmit circuit attached to the sensor housing. The transmit circuit is electrically connectable to the at least one transmit element. The transmit circuit is configured to generate a transmit signal to be transmitted by the at least one transmit element into a target containing the at least one analyte of interest. The transmit signal is in a radio or microwave frequency range of the electromagnetic spectrum. The sensor also includes a receive circuit attached to the sensor housing. The receive circuit is electrically connectable to the at least one receive element. The receive circuit is configured to receive a response detected by the at least one receive element resulting from transmission of the transmit signal by the at least one transmit element into the target containing the at least one analyte of interest. The system further includes a controller configured to direct an action affecting a level of the at least one analyte of interest in the medium, based on detection of the at least one analyte by the sensor. 
     In an embodiment, the action includes controlling a valve to increase or decrease a flow of the analyte of interest into the medium. In an embodiment, the action includes controlling a valve to increase or decrease flow into the medium of a compound interacting with the analyte of interest in the medium. In an embodiment, the system includes a mechanical device that is connected to and controlled by a signal from the controller, and the mechanical device is configured to control a level of the at least one analyte of interest in the medium based on the signal received from the controller. In an embodiment, the system includes a heating or cooling device that is connected to and controlled by a signal from the controller, and the heating or cooling device is configured to affect a temperature of the medium. In an embodiment, the analyte of interest is glucose, and the action includes operating an insulin pump based on detection of the glucose by the sensor. 
     In an embodiment, the controller is included in a device separate from the sensor. In an embodiment, the device separate from the sensor is configured to receive information regarding the analyte from the sensor. In an embodiment, the information regarding the analyte is a presence or amount of the analyte, and the controller is further configured to determine the action based on the presence or amount of the analyte. In an embodiment, the information regarding the analyte includes the action to be directed by the controller. In an embodiment, the system further includes a remote server, wherein the remote server is configured to receive information regarding the analyte from the sensor and to communicate a command to the controller. 
     In an embodiment, a method for automatically acting based on detection of one or more analytes includes non-invasively detecting the one or more analytes in a medium. Non-invasively detecting the one or more analytes includes generating a transmit signal having at least two different frequencies each of which falls within a range of between about 10 kHz to about 100 GHz and transmitting the transmit signal into the medium from at least one transmit element having a first geometry. Non-invasively detecting the one or more analytes further includes using at least one receive element that is decoupled from the at least one transmit element and having a second geometry that is geometrically different from the first geometry to detect a response resulting from transmitting the transmit signal by the at least one transmit element into the medium and determining a presence or an amount of each of the one or more analytes based on the response. The method further includes determining, at a controller, an automated action affecting a level of at least one of the one or more analytes based on the presence or the amount of said at least one of the one or more analytes; and directing a control device to perform the automated action. 
     In an embodiment, the automated action includes increasing or decreasing a flow into the medium of said at least one of the one or more analytes. In an embodiment, the automated action includes increasing or decreasing a flow into the medium of one or more chemicals other than said at least one of the one or more analytes. In an embodiment, the automated action includes increasing or decreasing a temperature of the medium. In an embodiment, the automated action is increasing or decreasing a supply of insulin provided by an insulin pump. In an embodiment, at least one of the one or more analytes includes insulin. 
     In an embodiment, non-invasively detecting the one or more analytes is performed using a sensor, and the controller and the sensor are included in one device. In an embodiment, non-invasively detecting the one or more analytes is performed using a sensor, and the controller is in a device separate from the sensor. In an embodiment, the device separate from the sensor is a remote server. In an embodiment, the device separate from the sensor includes the control device. 
     In an embodiment, the medium is a flow of a fluid. 
     In an embodiment, a method for automatically acting based on detection of one or more analytes includes non-invasively detecting the one or more analytes. Non-invasively detecting the one or more analytes includes generating a transmit signal having at least two different frequencies each of which falls within a range of between about 10 kHz to about 100 GHz and transmitting the transmit signal from at least one transmit element having a first geometry into the medium. Non-invasively detecting the one or more analytes further includes detecting a response resulting from transmitting the transmit signal by the at least one transmit element into the medium using at least one receive element that is less than 95% coupled to the at least one transmit element; The method further includes determining a presence or an amount of each of the one or more analytes based on the response. The method also includes determining, at a controller, an automated action based on the presence or the amount of at least one of the one or more analytes and directing a control device to perform the automated action. 
     In an embodiment, the automated action includes increasing or decreasing a flow into the medium of said at least one of the one or more analytes. In an embodiment, the automated action includes increasing or decreasing a flow into the medium of one or more chemicals other than said at least one of the one or more analytes. In an embodiment, the automated action includes increasing or decreasing a temperature of the medium. In an embodiment, the automated action is increasing or decreasing a supply of insulin provided by an insulin pump. In an embodiment, at least one of the one or more analytes includes insulin. 
     In an embodiment, non-invasively detecting the one or more analytes is performed using a sensor, and the controller and the sensor are included in one device. In an embodiment, non-invasively detecting the one or more analytes is performed using a sensor, and the controller is in a device separate from the sensor. In an embodiment, the device separate from the sensor is a remote server. In an embodiment, the device separate from the sensor includes the control device. 
     In an embodiment, the medium is a flow of a fluid. 
    
    
     
       DRAWINGS 
       References are made to the accompanying drawings that form a part of this disclosure, and which illustrate embodiments in which the apparatus, systems and methods described in this specification can be practiced. 
         FIG. 1  is a schematic depiction of a non-invasive analyte sensor system with a non-invasive analyte sensor relative to a target according to an embodiment. 
         FIGS. 2A-C  illustrate different example orientations of antenna arrays that can be used in the sensor system described herein. 
         FIGS. 3A-3I  illustrate different examples of transmit and receive antennas with different geometries. 
         FIGS. 4A, 4B, 4C and 4D  illustrate additional examples of different shapes that the ends of the transmit and receive antennas can have. 
         FIG. 5  is a schematic depiction of a sensor device according to an embodiment. 
         FIG. 6  is a flowchart of a method for detecting an analyte according to an embodiment. 
         FIG. 7  is a flowchart of analysis of a response according to an embodiment. 
         FIG. 8  is a flowchart of a method of providing an automated response to detection of one or more analytes according to an embodiment. 
         FIG. 9  illustrates one non-limiting example of a system configured to automatically carry out an action. 
         FIG. 10  illustrates one non-limiting example of a system configured to automatically control an insulin pump. 
     
    
    
     Like reference numbers represent like parts throughout. 
     DETAILED DESCRIPTION 
     The following is a detailed description of apparatus, systems and methods of non-invasively detecting an analyte via spectroscopic techniques using non-optical frequencies such as in the radio or microwave frequency bands of the electromagnetic spectrum. A non-invasive analyte sensor includes a transmit antenna (which may also be referred to as a transmit element) that functions to transmit a generated transmit signal that is in a radio or microwave frequency range of the electromagnetic spectrum into a target containing an analyte of interest, and a receive antenna (which may also be referred to as a receive element) that functions to detect a response resulting from transmission of the transmit signal by the transmit antenna into the target. The transmit antenna and the receive antenna are decoupled from one another which improves the detection performance of the sensor. 
     The transmit antenna and the receive antenna can be located near the target and operated as further described herein to assist in detecting at least one analyte in the target. The transmit antenna transmits a signal, which has at least two frequencies in the radio or microwave frequency range, toward and into the target. The signal with the at least two frequencies can be formed by separate signal portions, each having a discrete frequency, that are transmitted separately at separate times at each frequency. In another embodiment, the signal with the at least two frequencies may be part of a complex signal that includes a plurality of frequencies including the at least two frequencies. The complex signal can be generated by blending or multiplexing multiple signals together followed by transmitting the complex signal whereby the plurality of frequencies are transmitted at the same time. One possible technique for generating the complex signal includes, but is not limited to, using an inverse Fourier transformation technique. The receive antenna detects a response resulting from transmission of the signal by the transmit antenna into the target containing the at least one analyte of interest. 
     The transmit antenna and the receive antenna are decoupled (which may also be referred to as detuned or the like) from one another. Decoupling refers to intentionally fabricating the configuration and/or arrangement of the transmit antenna and the receive antenna to minimize direct communication between the transmit antenna and the receive antenna, preferably absent shielding. Shielding between the transmit antenna and the receive antenna can be utilized. However, the transmit antenna and the receive antenna are decoupled even without the presence of shielding. 
     The signal(s) detected by the receive antenna can be analyzed to detect the analyte based on the intensity of the received signal(s) and reductions in intensity at one or more frequencies where the analyte absorbs the transmitted signal. An example of detecting an analyte using a non-invasive spectroscopy sensor operating in the radio or microwave frequency range of the electromagnetic spectrum is described in WO 2019/217461, the entire contents of which are incorporated herein by reference. The signal(s) detected by the receive antenna can be complex signals including a plurality of signal components, each signal component being at a different frequency. In an embodiment, the detected complex signals can be decomposed into the signal components at each of the different frequencies, for example through a Fourier transformation. In an embodiment, the complex signal detected by the receive antenna can be analyzed as a whole (i.e. without demultiplexing the complex signal) to detect the analyte as long as the detected signal provides enough information to make the analyte detection. In addition, the signal(s) detected by the receive antenna can be separate signal portions, each having a discrete frequency. 
     In one embodiment, the sensor described herein can be used to detect the presence of at least one analyte in a target. In another embodiment, the sensor described herein can detect an amount or a concentration of the at least one analyte in the target. The target can be any target containing at least one analyte of interest that one may wish to detect. The target can be human or non-human, animal or non-animal, biological or non-biological. For example, the target can include, but is not limited to, human tissue, animal tissue, plant tissue, an inanimate object, soil, a fluid, genetic material, or a microbe. Non-limiting examples of targets include, but are not limited to, a fluid, for example blood, interstitial fluid, cerebral spinal fluid, lymph fluid or urine, human tissue, animal tissue, plant tissue, an inanimate object, soil, genetic material, or a microbe. 
     The analyte(s) can be any analyte that one may wish to detect. The analyte can be human or non-human, animal or non-animal, biological or non-biological. For example, the analyte(s) can include, but is not limited to, one or more of blood glucose, blood alcohol, white blood cells, or luteinizing hormone. The analyte(s) can include, but is not limited to, a chemical, a combination of chemicals, a virus, bacteria, or the like. The analyte can be a chemical included in another medium, with non-limiting examples of such media including a fluid containing the at least one analyte, for example blood, interstitial fluid, cerebral spinal fluid, lymph fluid or urine, human tissue, animal tissue, plant tissue, an inanimate object, soil, genetic material, or a microbe. The analyte(s) may also be a non-human, non-biological particle such as a mineral or a contaminant. 
     The analyte(s) can include, for example, naturally occurring substances, artificial substances, metabolites, and/or reaction products. As non-limiting examples, the at least one analyte can include, but is not limited to, insulin, acarboxyprothrombin; acylcarnitine; adenine phosphoribosyl transferase; adenosine deaminase; albumin; alpha-fetoprotein; amino acid profiles (arginine (Krebs cycle), histidine/urocanic acid, homocysteine, phenylalanine/tyrosine, tryptophan); andrenostenedione; antipyrine; arabinitol enantiomers; arginase; benzoylecgonine (cocaine); biotinidase; biopterin; c-reactive protein; carnitine; pro-BNP; BNP; troponin; carnosinase; CD4; ceruloplasmin; chenodeoxycholic acid; chloroquine; cholesterol; cholinesterase; conjugated 1-β hydroxy-cholic acid; cortisol; creatine kinase; creatine kinase MM isoenzyme; cyclosporin A; d-penicillamine; de-ethylchloroquine; dehydroepiandrosterone sulfate; DNA (acetylator polymorphism, alcohol dehydrogenase, alpha 1-antitrypsin, cystic fibrosis, Duchenne/Becker muscular dystrophy, analyte-6-phosphate dehydrogenase, hemoglobin A, hemoglobin S, hemoglobin C, hemoglobin D, hemoglobin E, hemoglobin F, D-Punjab, beta-thalassemia, hepatitis B virus, HCMV, HIV-1, HTLV-1, Leber hereditary optic neuropathy, MCAD, RNA, PKU,  Plasmodium vivax , sexual differentiation, 21-deoxycortisol); desbutylhalofantrine; dihydropteridine reductase; diptheria/tetanus antitoxin; erythrocyte arginase; erythrocyte protoporphyrin; esterase D; fatty acids/acylglycines; free β-human chorionic gonadotropin; free erythrocyte porphyrin; free thyroxine (FT4); free tri-iodothyronine (FT3); fumarylacetoacetase; galactose/gal-1-phosphate; galactose-1-phosphate uridyltransferase; gentamicin; analyte-6-phosphate dehydrogenase; glutathione; glutathione perioxidase; glycocholic acid; glycosylated hemoglobin; halofantrine; hemoglobin variants; hexosaminidase A; human erythrocyte carbonic anhydrase I; 17-alpha-hydroxyprogesterone; hypoxanthine phosphoribosyl transferase; immunoreactive trypsin; lactate; lead; lipoproteins ((a), B/A-1, β); lysozyme; mefloquine; netilmicin; phenobarbitone; phenytoin; phytanic/pristanic acid; progesterone; prolactin; prolidase; purine nucleoside phosphorylase; quinine; reverse tri-iodothyronine (rT3); selenium; serum pancreatic lipase; sissomicin; somatomedin C; specific antibodies (adenovirus, anti-nuclear antibody, anti-zeta antibody, arbovirus, Aujeszky&#39;s disease virus, dengue virus,  Dracunculus medinensis, Echinococcus granulosus, Entamoeba histolytica , enterovirus,  Giardia duodenalisa, Helicobacter pylori , hepatitis B virus, herpes virus, HIV-1, IgE (atopic disease), influenza virus,  Leishmania donovani, leptospira , measles/mumps/rubella,  Mycobacterium leprae, Mycoplasma pneumoniae , Myoglobin,  Onchocerca volvulus , parainfluenza virus,  Plasmodium falciparum , polio virus,  Pseudomonas aeruginosa , respiratory syncytial virus,  Rickettsia  (scrub typhus),  Schistosoma mansoni, Toxoplasma gondii, Trepenoma pallidium, Trypanosoma cruzi/rangeli , vesicular  stomatis  virus,  Wuchereria bancrofti , yellow fever virus); specific antigens (hepatitis B virus, HIV-1); succinylacetone; sulfadoxine; theophylline; thyrotropin (TSH); thyroxine (T4); thyroxine-binding globulin; trace elements; transferrin; UDP-galactose-4-epimerase; urea; uroporphyrinogen I synthase; vitamin A; white blood cells; and zinc protoporphyrin. 
     The analyte(s) can also include one or more chemicals introduced into the target. The analyte(s) can include a marker such as a contrast agent, a radioisotope, or other chemical agent. The analyte(s) can include a fluorocarbon-based synthetic blood. The analyte(s) can include a drug or pharmaceutical composition, with non-limiting examples including ethanol; cannabis (marijuana, tetrahydrocannabinol, hashish); inhalants (nitrous oxide, amyl nitrite, butyl nitrite, chlorohydrocarbons, hydrocarbons); cocaine (crack cocaine); stimulants (amphetamines, methamphetamines, Ritalin, Cylert, Preludin, Didrex, PreState, Voranil, Sandrex, Plegine); depressants (barbiturates, methaqualone, tranquilizers such as Valium, Librium, Miltown, Serax, Equanil, Tranxene); hallucinogens (phencyclidine, lysergic acid, mescaline, peyote, psilocybin); narcotics (heroin, codeine, morphine, opium, meperidine, Percocet, Percodan, Tussionex, Fentanyl, Darvon, Talwin, Lomotil); designer drugs (analogs of fentanyl, meperidine, amphetamines, methamphetamines, and phencyclidine, for example, Ecstasy); anabolic steroids; and nicotine. The analyte(s) can include other drugs or pharmaceutical compositions. The analyte(s) can include neurochemicals or other chemicals generated within the body, such as, for example, ascorbic acid, uric acid, dopamine, noradrenaline, 3-methoxytyramine (3MT), 3,4-Dihydroxyphenylacetic acid (DOPAC), Homovanillic acid (HVA), 5-Hydroxytryptamine (5HT), and 5-Hydroxyindoleacetic acid (FHIAA). 
     Referring now to  FIG. 1 , an embodiment of a non-invasive analyte sensor system with a non-invasive analyte sensor  5  is illustrated. The sensor  5  is depicted relative to a target  7  that contains an analyte of interest  9 . In this example, the sensor  5  is depicted as including an antenna array that includes a transmit antenna/element  11  (hereinafter “transmit antenna  11 ”) and a receive antenna/element  13  (hereinafter “receive antenna  13 ”). The sensor  5  further includes a transmit circuit  15 , a receive circuit  17 , and a controller  19 . As discussed further below, the sensor  5  can also include a power supply, such as a battery (not shown in  FIG. 1 ). 
     The transmit antenna  11  is positioned, arranged and configured to transmit a signal  21  that is the radio frequency (RF) or microwave range of the electromagnetic spectrum into the target  7 . The transmit antenna  11  can be an electrode or any other suitable transmitter of electromagnetic signals in the radio frequency (RF) or microwave range. The transmit antenna  11  can have any arrangement and orientation relative to the target  7  that is sufficient to allow the analyte sensing to take place. In one non-limiting embodiment, the transmit antenna  11  can be arranged to face in a direction that is substantially toward the target  7 . 
     The signal  21  transmitted by the transmit antenna  11  is generated by the transmit circuit  15  which is electrically connectable to the transmit antenna  11 . The transmit circuit  15  can have any configuration that is suitable to generate a transmit signal to be transmitted by the transmit antenna  11 . Transmit circuits for generating transmit signals in the RF or microwave frequency range are well known in the art. In one embodiment, the transmit circuit  15  can include, for example, a connection to a power source, a frequency generator, and optionally filters, amplifiers or any other suitable elements for a circuit generating an RF or microwave frequency electromagnetic signal. In an embodiment, the signal generated by the transmit circuit  15  can have at least two discrete frequencies (i.e. a plurality of discrete frequencies), each of which is in the range from about 10 kHz to about 100 GHz. In another embodiment, each of the at least two discrete frequencies can be in a range from about 300 MHz to about 6000 MHz. In an embodiment, the transmit circuit  15  can be configured to sweep through a range of frequencies that are within the range of about 10 kHz to about 100 GHz, or in another embodiment a range of about 300 MHz to about 6000 MHz. In an embodiment, the transmit circuit  15  can be configured to produce a complex transmit signal, the complex signal including a plurality of signal components, each of the signal components having a different frequency. The complex signal can be generated by blending or multiplexing multiple signals together followed by transmitting the complex signal whereby the plurality of frequencies are transmitted at the same time. 
     The receive antenna  13  is positioned, arranged, and configured to detect one or more electromagnetic response signals  23  that result from the transmission of the transmit signal  21  by the transmit antenna  11  into the target  7  and impinging on the analyte  9 . The receive antenna  13  can be an electrode or any other suitable receiver of electromagnetic signals in the radio frequency (RF) or microwave range. In an embodiment, the receive antenna  13  is configured to detect electromagnetic signals having at least two frequencies, each of which is in the range from about 10 kHz to about 100 GHz, or in another embodiment a range from about 300 MHz to about 6000 MHz. The receive antenna  13  can have any arrangement and orientation relative to the target  7  that is sufficient to allow detection of the response signal(s)  23  to allow the analyte sensing to take place. In one non-limiting embodiment, the receive antenna  13  can be arranged to face in a direction that is substantially toward the target  7 . 
     The receive circuit  17  is electrically connectable to the receive antenna  13  and conveys the received response from the receive antenna  13  to the controller  19 . The receive circuit  17  can have any configuration that is suitable for interfacing with the receive antenna  13  to convert the electromagnetic energy detected by the receive antenna  13  into one or more signals reflective of the response signal(s)  23 . The construction of receive circuits are well known in the art. The receive circuit  17  can be configured to condition the signal(s) prior to providing the signal(s) to the controller  19 , for example through amplifying the signal(s), filtering the signal(s), or the like. Accordingly, the receive circuit  17  may include filters, amplifiers, or any other suitable components for conditioning the signal(s) provided to the controller  19 . In an embodiment, at least one of the receive circuit  17  or the controller  19  can be configured to decompose or demultiplex a complex signal, detected by the receive antenna  13 , including a plurality of signal components each at different frequencies into each of the constituent signal components. In an embodiment, decomposing the complex signal can include applying a Fourier transform to the detected complex signal. However, decomposing or demultiplexing a received complex signal is optional. Instead, in an embodiment, the complex signal detected by the receive antenna can be analyzed as a whole (i.e. without demultiplexing the complex signal) to detect the analyte as long as the detected signal provides enough information to make the analyte detection. 
     The controller  19  controls the operation of the sensor  5 . The controller  19 , for example, can direct the transmit circuit  15  to generate a transmit signal to be transmitted by the transmit antenna  11 . The controller  19  further receives signals from the receive circuit  17 . The controller  19  can optionally process the signals from the receive circuit  17  to detect the analyte(s)  9  in the target  7 . In one embodiment, the controller  19  may optionally be in communication with at least one external device  25  such as a user device and/or a remote server  27 , for example through one or more wireless connections such as Bluetooth, wireless data connections such a 4G, 5G, LTE or the like, or Wi-Fi. If provided, the external device  25  and/or remote server  27  may process (or further process) the signals that the controller  19  receives from the receive circuit  17 , for example to detect the analyte(s)  9 . If provided, the external device  25  may be used to provide communication between the sensor  5  and the remote server  27 , for example using a wired data connection or via a wireless data connection or Wi-Fi of the external device  25  to provide the connection to the remote server  27 . In an embodiment, the controller  19  is further configured to determine an action to be taken in response to detection of the analyte or analytes of interest  9 . In an embodiment, another controller (not shown) separate from controller  19  can determine the action. 
     With continued reference to  FIG. 1 , the sensor  5  may include a sensor housing  29  (shown in dashed lines) that defines an interior space  31 . Components of the sensor  5  may be attached to and/or disposed within the housing  29 . For example, the transmit antenna  11  and the receive antenna  13  are attached to the housing  29 . In some embodiments, the antennas  11 ,  13  may be entirely or partially within the interior space  31  of the housing  29 . In some embodiments, the antennas  11 ,  13  may be attached to the housing  29  but at least partially or fully located outside the interior space  31 . In some embodiments, the transmit circuit  15 , the receive circuit  17  and the controller  19  are attached to the housing  29  and disposed entirely within the sensor housing  29 . 
     The receive antenna  13  is decoupled or detuned with respect to the transmit antenna  11  such that electromagnetic coupling between the transmit antenna  11  and the receive antenna  13  is reduced. The decoupling of the transmit antenna  11  and the receive antenna  13  increases the portion of the signal(s) detected by the receive antenna  13  that is the response signal(s)  23  from the target  7 , and minimizes direct receipt of the transmitted signal  21  by the receive antenna  13 . The decoupling of the transmit antenna  11  and the receive antenna  13  results in transmission from the transmit antenna  11  to the receive antenna  13  having a reduced forward gain (S 21 ) and an increased reflection at output (S 22 ) compared to antenna systems having coupled transmit and receive antennas. 
     In an embodiment, coupling between the transmit antenna  11  and the receive antenna  13  is 95% or less. In another embodiment, coupling between the transmit antenna  11  and the receive antenna  13  is 90% or less. In another embodiment, coupling between the transmit antenna  11  and the receive antenna  13  is 85% or less. In another embodiment, coupling between the transmit antenna  11  and the receive antenna  13  is 75% or less. 
     Any technique for reducing coupling between the transmit antenna  11  and the receive antenna  13  can be used. For example, the decoupling between the transmit antenna  11  and the receive antenna  13  can be achieved by one or more intentionally fabricated configurations and/or arrangements between the transmit antenna  11  and the receive antenna  13  that is sufficient to decouple the transmit antenna  11  and the receive antenna  13  from one another. 
     For example, in one embodiment described further below, the decoupling of the transmit antenna  11  and the receive antenna  13  can be achieved by intentionally configuring the transmit antenna  11  and the receive antenna  13  to have different geometries from one another. Intentionally different geometries refers to different geometric configurations of the transmit and receive antennas  11 ,  13  that are intentional. Intentional differences in geometry are distinct from differences in geometry of transmit and receive antennas that may occur by accident or unintentionally, for example due to manufacturing errors or tolerances. 
     Another technique to achieve decoupling of the transmit antenna  11  and the receive antenna  13  is to provide appropriate spacing between each antenna  11 ,  13  that is sufficient to decouple the antennas  11 ,  13  and force a proportion of the electromagnetic lines of force of the transmitted signal  21  into the target  7  thereby minimizing or eliminating as much as possible direct receipt of electromagnetic energy by the receive antenna  13  directly from the transmit antenna  11  without traveling into the target  7 . The appropriate spacing between each antenna  11 ,  13  can be determined based upon factors that include, but are not limited to, the output power of the signal from the transmit antenna  11 , the size of the antennas  11 ,  13 , the frequency or frequencies of the transmitted signal, and the presence of any shielding between the antennas. This technique helps to ensure that the response detected by the receive antenna  13  is measuring the analyte  9  and is not just the transmitted signal  21  flowing directly from the transmit antenna  11  to the receive antenna  13 . In some embodiments, the appropriate spacing between the antennas  11 ,  13  can be used together with the intentional difference in geometries of the antennas  11 ,  13  to achieve decoupling. 
     In one embodiment, the transmit signal that is transmitted by the transmit antenna  11  can have at least two different frequencies, for example upwards of 7 to 12 different and discrete frequencies. In another embodiment, the transmit signal can be a series of discrete, separate signals with each separate signal having a single frequency or multiple different frequencies. 
     In one embodiment, the transmit signal (or each of the transmit signals) can be transmitted over a transmit time that is less than, equal to, or greater than about 300 ms. In another embodiment, the transmit time can be than, equal to, or greater than about 200 ms. In still another embodiment, the transmit time can be less than, equal to, or greater than about 30 ms. The transmit time could also have a magnitude that is measured in seconds, for example 1 second, 5 seconds, 10 seconds, or more. In an embodiment, the same transmit signal can be transmitted multiple times, and then the transmit time can be averaged. In another embodiment, the transmit signal (or each of the transmit signals) can be transmitted with a duty cycle that is less than or equal to about 50%. 
       FIGS. 2A-2C  illustrate examples of antenna arrays  33  that can be used in the sensor system  5  and how the antenna arrays  33  can be oriented. Many orientations of the antenna arrays  33  are possible, and any orientation can be used as long as the sensor  5  can perform its primary function of sensing the analyte  9 . 
     In  FIG. 2A , the antenna array  33  includes the transmit antenna  11  and the receive antenna  13  disposed on a substrate  35  which may be substantially planar. This example depicts the array  33  disposed substantially in an X-Y plane. In this example, dimensions of the antennas  11 ,  13  in the X and Y-axis directions can be considered lateral dimensions, while a dimension of the antennas  11 ,  13  in the Z-axis direction can be considered a thickness dimension. In this example, each of the antennas  11 ,  13  has at least one lateral dimension (measured in the X-axis direction and/or in the Y-axis direction) that is greater than the thickness dimension thereof (in the Z-axis direction). In other words, the transmit antenna  11  and the receive antenna  13  are each relatively flat or of relatively small thickness in the Z-axis direction compared to at least one other lateral dimension measured in the X-axis direction and/or in the Y-axis direction. 
     In use of the embodiment in  FIG. 2A , the sensor and the array  33  may be positioned relative to the target  7  such that the target  7  is below the array  33  in the Z-axis direction or above the array  33  in the Z-axis direction whereby one of the faces of the antennas  11 ,  13  face toward the target  7 . Alternatively, the target  7  can be positioned to the left or right sides of the array  33  in the X-axis direction whereby one of the ends of each one of the antennas  11 ,  13  face toward the target  7 . Alternatively, the target  7  can be positioned to the sides of the array  33  in the Y-axis direction whereby one of the sides of each one of the antennas  11 ,  13  face toward the target  7 . 
     The sensor  5  can also be provided with one or more additional antenna arrays in addition the antenna array  33 . For example,  FIG. 2A  also depicts an optional second antenna array  33   a  that includes the transmit antenna  11  and the receive antenna  13  disposed on a substrate  35   a  which may be substantially planar. Like the array  33 , the array  33   a  may also be disposed substantially in the X-Y plane, with the arrays  33 ,  33   a  spaced from one another in the X-axis direction. 
     In  FIG. 2B , the antenna array  33  is depicted as being disposed substantially in the Y-Z plane. In this example, dimensions of the antennas  11 ,  13  in the Y and Z-axis directions can be considered lateral dimensions, while a dimension of the antennas  11 ,  13  in the X-axis direction can be considered a thickness dimension. In this example, each of the antennas  11 ,  13  has at least one lateral dimension (measured in the Y-axis direction and/or in the Z-axis direction) that is greater than the thickness dimension thereof (in the X-axis direction). In other words, the transmit antenna  11  and the receive antenna  13  are each relatively flat or of relatively small thickness in the X-axis direction compared to at least one other lateral dimension measured in the Y-axis direction and/or in the Z-axis direction. 
     In use of the embodiment in  FIG. 2B , the sensor and the array  33  may be positioned relative to the target  7  such that the target  7  is below the array  33  in the Z-axis direction or above the array  33  in the Z-axis direction whereby one of the ends of each one of the antennas  11 ,  13  face toward the target  7 . Alternatively, the target  7  can be positioned in front of or behind the array  33  in the X-axis direction whereby one of the faces of each one of the antennas  11 ,  13  face toward the target  7 . Alternatively, the target  7  can be positioned to one of the sides of the array  33  in the Y-axis direction whereby one of the sides of each one of the antennas  11 ,  13  face toward the target  7 . 
     In  FIG. 2C , the antenna array  33  is depicted as being disposed substantially in the X-Z plane. In this example, dimensions of the antennas  11 ,  13  in the X and Z-axis directions can be considered lateral dimensions, while a dimension of the antennas  11 ,  13  in the Y-axis direction can be considered a thickness dimension. In this example, each of the antennas  11 ,  13  has at least one lateral dimension (measured in the X-axis direction and/or in the Z-axis direction) that is greater than the thickness dimension thereof (in the Y-axis direction). In other words, the transmit antenna  11  and the receive antenna  13  are each relatively flat or of relatively small thickness in the Y-axis direction compared to at least one other lateral dimension measured in the X-axis direction and/or in the Z-axis direction. 
     In use of the embodiment in  FIG. 2C , the sensor and the array  33  may be positioned relative to the target  7  such that the target  7  is below the array  33  in the Z-axis direction or above the array  33  in the Z-axis direction whereby one of the ends of each one of the antennas  11 ,  13  face toward the target  7 . Alternatively, the target  7  can be positioned to the left or right sides of the array  33  in the X-axis direction whereby one of the sides of each one of the antennas  11 ,  13  face toward the target  7 . Alternatively, the target  7  can be positioned in front of or in back of the array  33  in the Y-axis direction whereby one of the faces of each one of the antennas  11 ,  13  face toward the target  7 . 
     The arrays  33 ,  33   a  in  FIGS. 2A-2C  need not be oriented entirely within a plane such as the X-Y plane, the Y-Z plane or the X-Z plane. Instead, the arrays  33 ,  33   a  can be disposed at angles to the X-Y plane, the Y-Z plane and the X-Z plane. 
     Decoupling Antennas Using Differences in Antenna Geometries 
     As mentioned above, one technique for decoupling the transmit antenna  11  from the receive antenna  13  is to intentionally configure the transmit antenna  11  and the receive antenna  13  to have intentionally different geometries. Intentionally different geometries refers to differences in geometric configurations of the transmit and receive antennas  11 ,  13  that are intentional, and is distinct from differences in geometry of the transmit and receive antennas  11 ,  13  that may occur by accident or unintentionally, for example due to manufacturing errors or tolerances when fabricating the antennas  11 ,  13 . 
     The different geometries of the antennas  11 ,  13  may manifest itself, and may be described, in a number of different ways. For example, in a plan view of each of the antennas  11 ,  13  (such as in  FIGS. 3A-I ), the shapes of the perimeter edges of the antennas  11 ,  13  may be different from one another. The different geometries may result in the antennas  11 ,  13  having different surface areas in plan view. The different geometries may result in the antennas  11 ,  13  having different aspect ratios in plan view (i.e. a ratio of their sizes in different dimensions; for example, as discussed in further detail below, the ratio of the length divided by the width of the antenna  11  may be different than the ratio of the length divided by the width for the antenna  13 ). In some embodiments, the different geometries may result in the antennas  11 ,  13  having any combination of different perimeter edge shapes in plan view, different surface areas in plan view, and/or different aspect ratios. In some embodiments, the antennas  11 ,  13  may have one or more holes formed therein (see  FIG. 2B ) within the perimeter edge boundary, or one or more notches formed in the perimeter edge (see  FIG. 2B ). 
     So as used herein, a difference in geometry or a difference in geometrical shape of the antennas  11 ,  13  refers to any intentional difference in the figure, length, width, size, shape, area closed by a boundary (i.e. the perimeter edge), etc. when the respective antenna  11 ,  13  is viewed in a plan view. 
     The antennas  11 ,  13  can have any configuration and can be formed from any suitable material that allows them to perform the functions of the antennas  11 ,  13  as described herein. In one embodiment, the antennas  11 ,  13  can be formed by strips of material. A strip of material can include a configuration where the strip has at least one lateral dimension thereof greater than a thickness dimension thereof when the antenna is viewed in a plan view (in other words, the strip is relatively flat or of relatively small thickness compared to at least one other lateral dimension, such as length or width when the antenna is viewed in a plan view as in  FIGS. 3A-I ). A strip of material can include a wire. The antennas  11 ,  13  can be formed from any suitable conductive material(s) including metals and conductive non-metallic materials. Examples of metals that can be used include, but are not limited to, copper or gold. Another example of a material that can be used is non-metallic materials that are doped with metallic material to make the non-metallic material conductive. 
     In  FIGS. 2A-2C , the antennas  11 ,  13  within each one of the arrays  33 ,  33   a  have different geometries from one another. In addition,  FIGS. 3A-I  illustrate plan views of additional examples of the antennas  11 ,  13  having different geometries from one another. The examples in  FIGS. 2A-2C and 3A -I are not exhaustive and many different configurations are possible. 
     With reference initially to  FIG. 3A , a plan view of an antenna array having two antennas with different geometries is illustrated. In this example (as well as for the examples in  FIGS. 2A-2C and 3B-3I ), for sake of convenience in describing the concepts herein, one antenna is labeled as the transmit antenna  11  and the other antenna is labeled as the receive antenna  13 . However, the antenna labeled as the transmit antenna  11  could be the receive antenna  13 , while the antenna labeled as the receive antenna  13  could be the transmit antenna  11 . Each of the antennas  11 ,  13  are disposed on the substrate  35  having a planar surface  37 . 
     The antennas  11 ,  13  can be formed as linear strips or traces on the surface  37 . In this example, the antenna  11  is generally U-shaped and has a first linear leg  40   a , a second linear leg  40   b  that extends perpendicular to the first leg  40   a , and a third linear leg  40   c  that extends parallel to the leg  40   a . Likewise, the antenna  13  is formed by a single leg that extends parallel to, and between, the legs  40   a ,  40   c.    
     In the example depicted in  FIG. 3A , each one of the antennas  11 ,  13  has at least one lateral dimension that is greater than a thickness dimension thereof (in  FIG. 3A , the thickness dimension would extend into/from the page when viewing  FIG. 3A ). For example, the leg  40   a  of the antenna  11  extends in one direction (i.e. a lateral dimension) an extent that is greater than a thickness dimension of the leg  40   a  extending into or out of the page; the leg  40   b  of the antenna  11  extends in a direction (i.e. a lateral dimension) an extent that is greater than a thickness dimension of the leg  40   b  extending into or out of the page; and the leg  40   c  of the antenna  11  extends in one direction (i.e. a lateral dimension) an extent that is greater than a thickness dimension of the leg  40   c  extending into or out of the page. Likewise, the antenna  13  extends in one direction (i.e. a lateral dimension) an extent that is greater than a thickness dimension of the antenna  13  extending into or out of the page. 
     The antennas  11 ,  13  also differ in geometry from one another in that the total linear length of the antenna  11  (determined by adding the individual lengths L 1 , L 2 , L 3  of the legs  40   a - c  together) when viewed in plan view is greater than the length L 13  of the antenna  13  when viewed in plan view. 
       FIG. 3B  illustrates another plan view of an antenna array having two antennas with different geometries. In this example, the antennas  11 ,  13  are illustrated as substantially linear strips each with a lateral length L 11 , L 13 , a lateral width W 11 , W 13 , and a perimeter edge E 11 , E 13 . The perimeter edges E 11 , E 13  extend around the entire periphery of the antennas  11 ,  13  and bound an area in plan view. In this example, the lateral length L 11 , L 13  and/or the lateral width W 11 , W 13  is greater than a thickness dimension of the antennas  11 ,  13  extending into/from the page when viewing  FIG. 3B . In this example, the antennas  11 ,  13  differ in geometry from one another in that the shapes of the ends of the antennas  11 ,  13  differ from one another. For example, when viewing  FIG. 3B , the right end  42  of the antenna  11  has a different shape than the right end  44  of the antenna  13 . Similarly, the left end  46  of the antenna  11  may have a similar shape as the right end  42 , but differs from the left end  48  of the antenna  13  which may have a similar shape as the right end  44 . It is also possible that the lateral lengths L 11 , L 13  and/or the lateral widths W 11 , W 13  of the antennas  11 ,  13  could differ from one another. 
       FIG. 3C  illustrates another plan view of an antenna array having two antennas with different geometries that is somewhat similar to  FIG. 3B . In this example, the antennas  11 ,  13  are illustrated as substantially linear strips each with the lateral length L 11 , L 13 , the lateral width W 11 , W 13 , and the perimeter edge E 11 , E 13 . The perimeter edges E 11 , E 13  extend around the entire periphery of the antennas  11 ,  13  and bound an area in plan view. In this example, the lateral length L 11 , L 13  and/or the lateral width W 11 , W 13  is greater than a thickness dimension of the antennas  11 ,  13  extending into/from the page when viewing  FIG. 3C . In this example, the antennas  11 ,  13  differ in geometry from one another in that the shapes of the ends of the antennas  11 ,  13  differ from one another. For example, when viewing  FIG. 3C , the right end  42  of the antenna  11  has a different shape than the right end  44  of the antenna  13 . Similarly, the left end  46  of the antenna  11  may have a similar shape as the right end  42 , but differs from the left end  48  of the antenna  13  which may have a similar shape as the right end  44 . In addition, the lateral widths W 11 , W 13  of the antennas  11 ,  13  differ from one another. It is also possible that the lateral lengths L 11 , L 13  of the antennas  11 ,  13  could differ from one another. 
       FIG. 3D  illustrates another plan view of an antenna array having two antennas with different geometries that is somewhat similar to  FIGS. 3B and 3C . In this example, the antennas  11 ,  13  are illustrated as substantially linear strips each with the lateral length L 11 , L 13 , the lateral width W 11 , W 13 , and the perimeter edge E 11 , E 13 . The perimeter edges E 11 , E 13  extend around the entire periphery of the antennas  11 ,  13  and bound an area in plan view. In this example, the lateral length L 11 , L 13  and/or the lateral width W 11 , W 13  is greater than a thickness dimension of the antennas  11 ,  13  extending into/from the page when viewing  FIG. 3D . In this example, the antennas  11 ,  13  differ in geometry from one another in that the shapes of the ends of the antennas  11 ,  13  differ from one another. For example, when viewing  FIG. 3D , the right end  42  of the antenna  11  has a different shape than the right end  44  of the antenna  13 . Similarly, the left end  46  of the antenna  11  may have a similar shape as the right end  42 , but differs from the left end  48  of the antenna  13  which may have a similar shape as the right end  44 . In addition, the lateral widths W 11 , W 13  of the antennas  11 ,  13  differ from one another. It is also possible that the lateral lengths L 11 , L 13  of the antennas  11 ,  13  could differ from one another. 
       FIG. 3E  illustrates another plan view of an antenna array having two antennas with different geometries on a substrate. In this example, the antenna  11  is illustrated as being a strip of material having a generally horseshoe shape, while the antenna  13  is illustrated as being a strip of material that is generally linear. The planar shapes (i.e. geometries) of the antennas  11 ,  13  differ from one another. In addition, the total length of the antenna  11  (measured from one end to the other) when viewed in plan view is greater than the length of the antenna  13  when viewed in plan. 
       FIG. 3F  illustrates another plan view of an antenna array having two antennas with different geometries on a substrate. In this example, the antenna  11  is illustrated as being a strip of material forming a right angle, and the antenna  13  is also illustrated as being a strip of material that forms a larger right angle. The planar shapes (i.e. geometries) of the antennas  11 ,  13  differ from one another since the total area in plan view of the antenna  13  is greater than the total area in plan view of the antenna  11 . In addition, the total length of the antenna  11  (measured from one end to the other) when viewed in plan view is less than the length of the antenna  13  when viewed in plan. 
       FIG. 3G  illustrates another plan view of an antenna array having two antennas with different geometries on a substrate. In this example, the antenna  11  is illustrated as being a strip of material forming a square, and the antenna  13  is illustrated as being a strip of material that forms a rectangle. The planar shapes (i.e. geometries) of the antennas  11 ,  13  differ from one another. In addition, at least one of the width/length of the antenna  11  when viewed in plan view is less than one of the width/length of the antenna  13  when viewed in plan. 
       FIG. 3H  illustrates another plan view of an antenna array having two antennas with different geometries on a substrate. In this example, the antenna  11  is illustrated as being a strip of material forming a circle when viewed in plan, and the antenna  13  is also illustrated as being a strip of material that forms a smaller circle when viewed in plan surrounded by the circle formed by the antenna  11 . The planar shapes (i.e. geometries) of the antennas  11 ,  13  differ from one another due to the different sizes of the circles. 
       FIG. 3I  illustrates another plan view of an antenna array having two antennas with different geometries on a substrate. In this example, the antenna  11  is illustrated as being a linear strip of material, and the antenna  13  is illustrated as being a strip of material that forms a semi-circle when viewed in plan. The planar shapes (i.e. geometries) of the antennas  11 ,  13  differ from one another due to the different shapes/geometries of the antennas  11 ,  13 . 
       4 A-D are plan views of additional examples of different shapes that the ends of the transmit and receive antennas  11 ,  13  can have to achieve differences in geometry. Either one of, or both of, the ends of the antennas  11 ,  13  can have the shapes in  FIGS. 4A-D , including in the embodiments in  FIGS. 3A-I .  FIG. 4A  depicts the end as being generally rectangular.  FIG. 4B  depicts the end as having one rounded corner while the other corner remains a right angle.  FIG. 4C  depicts the entire end as being rounded or outwardly convex.  FIG. 4D  depicts the end as being inwardly concave. Many other shapes are possible. 
     Another technique to achieve decoupling of the antennas  11 ,  13  is to use an appropriate spacing between each antenna  11 ,  13  with the spacing being sufficient to force most or all of the signal(s) transmitted by the transmit antenna  11  into the target, thereby minimizing the direct receipt of electromagnetic energy by the receive antenna  13  directly from the transmit antenna  11 . The appropriate spacing can be used by itself to achieve decoupling of the antennas  11 ,  13 . In another embodiment, the appropriate spacing can be used together with differences in geometry of the antennas  11 ,  13  to achieve decoupling. 
     Referring to  FIG. 2A , there is a spacing D between the transmit antenna  11  and the receive antenna  13  at the location indicated. The spacing D between the antennas  11 ,  13  may be constant over the entire length (for example in the X-axis direction) of each antenna  11 ,  13 , or the spacing D between the antennas  11 ,  13  could vary. Any spacing D can be used as long as the spacing D is sufficient to result in most or all of the signal(s) transmitted by the transmit antenna  11  reaching the target and minimizing the direct receipt of electromagnetic energy by the receive antenna  13  directly from the transmit antenna  11 , thereby decoupling the antennas  11 ,  13  from one another. 
     Referring to  FIG. 5 , an example configuration of the sensor device  5  is illustrated. In  FIG. 5 , elements that are identical or similar to elements in  FIG. 1  are referenced using the same reference numerals. In  FIG. 5 , the antennas  11 ,  13  are disposed on one surface of a substrate  50  which can be, for example, a printed circuit board. At least one battery  52 , such as a rechargeable battery, is provided above the substrate  50 , for providing power to the sensor device  5 . In addition, a digital printed circuit board  54  is provided on which the transmit circuit  15 , the receive circuit  17 , and the controller  19  and other electronics of the second device  5  can be disposed. The substrate  50  and the digital printed circuit board  54  are electrically connected via any suitable electrical connection, such as a flexible connector  56 . An RF shield  58  may optionally be positioned between the antennas  11 ,  13  and the battery  52 , or between the antennas  11 ,  13  and the digital printed circuit board  54 , to shield the circuitry and electrical components from RF interference. 
     As depicted in  FIG. 5 , all of the elements of the sensor device  5 , including the antennas  11 ,  13 , the transmit circuit  15 , the receive circuit  17 , the controller  19 , the battery  52  and the like are contained entirely within the interior space  31  of the housing  29 . In an alternative embodiment, a portion of or the entirety of each antenna  11 ,  13  can project below a bottom wall  60  of the housing  29 . In another embodiment, the bottom of each antenna  11 ,  13  can be level with the bottom wall  60 , or they can be slightly recessed from the bottom wall  60 . 
     The housing  29  of the sensor device  5  can have any configuration and size that one finds suitable for employing in a non-invasive sensor device. In one embodiment, the housing  29  can have a maximum length dimension L H  no greater than 50 mm, a maximum width dimension W H  no greater than 50 mm, and a maximum thickness dimension TH no greater than 25 mm, for a total interior volume of no greater than about 62.5 cm 3 . 
     In addition, with continued reference to  FIG. 5  together with  FIGS. 3A-3I , there is preferably a maximum spacing D max  and a minimum spacing D min  between the transmit antenna  11  and the receive antenna  13 . The maximum spacing D max  may be dictated by the maximum size of the housing  29 . In one embodiment, the maximum spacing D max  can be about 50 mm. In one embodiment, the minimum spacing D min  can be from about 1.0 mm to about 5.0 mm. 
     With reference now to  FIG. 6  together with  FIG. 1 , one embodiment of a method  70  for detecting at least one analyte in a target is depicted. The method in  FIG. 6  can be practiced using any of the embodiments of the sensor device  5  described herein. In order to detect the analyte, the sensor device  5  is placed in relatively close proximity to the target. Relatively close proximity means that the sensor device  5  can be close to but not in direct physical contact with the target, or alternatively the sensor device  5  can be placed in direct, intimate physical contact with the target. The spacing between the sensor device  5  and the target  7  can be dependent upon a number of factors, such as the power of the transmitted signal. Assuming the sensor device  5  is properly positioned relative to the target  7 , at box  72  the transmit signal is generated, for example by the transmit circuit  15 . The transmit signal is then provided to the transmit antenna  11  which, at box  74 , transmits the transmit signal toward and into the target. At box  76 , a response resulting from the transmit signal contacting the analyte(s) is then detected by the receive antenna  13 . The receive circuit  17  obtains the detected response from the receive antenna  13  and provides the detected response to the controller  19 . At box  78 , the detected response can then be analyzed to detect at least one analyte. The analysis can be performed by the controller  19  and/or by the external device  25  and/or by the remote server  27 . 
     Referring to  FIG. 7 , the analysis at box  78  in the method  70  can take a number of forms. In one embodiment, at box  80 , the analysis can simply detect the presence of the analyte, i.e. is the analyte present in the target. Alternatively, at box  82 , the analysis can determine the amount of the analyte that is present. 
     The interaction between the transmitted signal and the analyte may, in some cases, increase the intensity of the signal(s) that is detected by the receive antenna, and may, in other cases, decrease the intensity of the signal(s) that is detected by the receive antenna. For example, in one non-limiting embodiment, when analyzing the detected response, compounds in the target, including the analyte of interest that is being detected, can absorb some of the transmit signal, with the absorption varying based on the frequency of the transmit signal. The response signal detected by the receive antenna may include drops in intensity at frequencies where compounds in the target, such as the analyte, absorb the transmit signal. The frequencies of absorption are particular to different analytes. The response signal(s) detected by the receive antenna can be analyzed at frequencies that are associated with the analyte of interest to detect the analyte based on drops in the signal intensity corresponding to absorption by the analyte based on whether such drops in signal intensity are observed at frequencies that correspond to the absorption by the analyte of interest. A similar technique can be employed with respect to increases in the intensity of the signal(s) caused by the analyte. 
     Detection of the presence of the analyte can be achieved, for example, by identifying a change in the signal intensity detected by the receive antenna at a known frequency associated with the analyte. The change may be a decrease in the signal intensity or an increase in the signal intensity depending upon how the transmit signal interacts with the analyte. The known frequency associated with the analyte can be established, for example, through testing of solutions known to contain the analyte. Determination of the amount of the analyte can be achieved, for example, by identifying a magnitude of the change in the signal at the known frequency, for example using a function where the input variable is the magnitude of the change in signal and the output variable is an amount of the analyte. The determination of the amount of the analyte can further be used to determine a concentration, for example based on a known mass or volume of the target. In an embodiment, presence of the analyte and determination of the amount of analyte may both be determined, for example by first identifying the change in the detected signal to detect the presence of the analyte, and then processing the detected signal(s) to identify the magnitude of the change to determine the amount. 
     Automated Response to Detected Analytes 
       FIG. 8  is a flowchart of a method of providing an automated response to detection of one or more analytes according to an embodiment. The method  90  can include detecting one or more analytes  92 , determining an action to take  94 , providing an instruction directing the determined action  96 , and taking the action  98 . The method  90  can be performed continuously, repeated iteratively, performed according to a predetermined schedule or sampling frequency, or when triggered by an event or a user prompt. 
     One or more analytes are detected at  92 . The one or more analytes can include any of the analytes described herein. The detection of the one or more analytes at  92  can be performed using any of the sensors described herein. The detection of the one or more analytes can include detection of a presence and/or an amount of each of the one or more analytes. Each of the one or more analytes can be detected according to any of the methods described herein. 
     Determination of an action to take occurs at  94 . The action can be any suitable response to detection of one or more analytes that can be implemented by one or more control devices. The action can modify one or more properties of the medium or components thereof such as the at least one analyte of interest. The properties that can be affected by the action determined at  94  include, for example, physical properties such as density, shape, distributions of different materials, or viscosity, chemical properties such as the stereochemistry of one or more materials, temperatures, electrical properties such as resistivity, or the like. The properties can be altered, for example, by using mechanical devices to move or stir the materials or to alter shape of a vessel containing the medium, adding additives to the medium, directing the medium through one or more filters, or any other such suitable action based on the desired response to the detection of the at least one analyte, the one or more properties to be affected in such a response, and mechanical acts and/or chemical interactions usable to produce the effects on the one or more properties. 
     The action can be determined at  94  based on the particular application, the one or more analytes being detected, and the capabilities of the automated controls. For example, where the one or more analytes include blood glucose and the control device is an insulin pump, the action can be an amount or rate for the supply of insulin. In an embodiment, the action directly affects an amount of one or more of the analytes, for example, increasing or decreasing a flow of the analyte into a medium through, for example, a valve on a line providing the analyte. In an embodiment, the action is a response to the detection of the analyte, for example shutting off a flow of a medium using, for example, a valve, a controllable duct, or the like when the presence of an analyte indicates contamination in the medium. In an embodiment, the action can indirectly affect the amount of one or more of the analytes, for example operation of an insulin pump to supply insulin when blood glucose is above an upper boundary or to reduce the supply of insulin when blood glucose is below a lower boundary. Other non-limiting examples of controls indirectly affecting levels of the one or more analytes can include controlling the addition of precursors or catalysts to a reaction mixture, adding biocides to reduce bacteria or other biological contaminants, or any other suitable control that does not directly control a supply of the one or more analytes, but can trigger a change in the levels of those analytes in a medium. 
     The action can be determined at  94  based on logic relating to the presence and/or amount of the one or more analytes detected at  92 . The determination of the action can be performed, for example, at the device including the sensor used to detect the one or more analytes at  92 , a local device separate from but located in proximity to the device including the sensor, a remote server such as a cloud server, or any other suitable device including a controller configured to determine the action. The logic can include, for example, upper and/or lower boundaries for the one or more analytes, one or more target quantities for the one or more analytes, conditional logic based on the presence or absence of the one or more analytes detected at  92 , or any other suitable logic allowing a controller to associate the one or more analytes detected at  92  with actions responsive to the detection. The logic can include multiple different actions associated with different amounts or presences of the one or more analytes. For example, the logic can include both an upper boundary and a lower boundary for, each with a different associated action. In an embodiment, the logic can include particular values for particular parameters, for example associating particular settings for a variable control, such as a flow rate or aperture size through a controllable valve, a particular dosage of a medical composition such as insulin or a drug, or the like, with particular levels of one or more analytes. The association of levels of the one or more analytes with particular setting for variable controls can be made, for example, through formulae, lookup tables, or any other suitable method. 
     Once the action to take is determined at  94 , an instruction directing the determined action is provided  96 . The instruction can be any suitable command to direct taking of the action determined at  94 . The instruction can be provided at  96  by conveying the command to the device taking action, for example by a wired connection, any suitable wireless communications, or combinations thereof. One more devices may be involved in conveying the command, such as a remote server conveying the command to a local device that then conveys the instruction to the device taking action. Once the instruction is provided at  96 , the action can be taken at  98 . The action can be taken at  98  by operating any suitable device according to the instruction provided at  96 , such as opening or closing one or more valves, moving one or more vanes, replacing filters, or adjusting a flow of a material into the medium. In an embodiment, the material can be a material reactive with a component in the medium such as the at least one analyte of interest. In an embodiment, the material can be a material capable of affecting properties of the medium such as density, viscosity, or resistivity of the medium, such as an additive. In an embodiment, the action can be heating or cooling the medium. For example, the action can include heating the medium using a heating element, heat lamp, or other suitable heat source. In an embodiment, the action can include cooling the medium, for example using a refrigeration circuit, addition of materials at relatively lower temperature than the medium, or other suitable device or technique for cooling the medium. In an embodiment, the action taken is as adjusting an output rate or amount of insulin provided by an insulin pump. 
     As indicated above, the data obtained by the sensor  5  needs to be analyzed, for example by determining an action to take based on said data as described above, and causing that action to be automatically performed. The analysis can occur on the sensor  5  or on one or more devices or systems separate from the sensor  5 . Unless otherwise indicated by the Applicant, the term devices or systems is intended to be construed broadly as encompassing any type of devices or systems that can analyze the data obtained by the sensor  5 . Examples of devices or system that can be used to analyze the data include, but are not limited to, hardware-based computing devices or systems; cloud-based computing devices or systems; machine learning devices or systems including active learning devices or systems; artificial intelligence-based devices or systems; neural network-based devices or systems; combinations thereof, and any other types of devices and systems that are suitable for analyzing the data. The devices can be located at any suitable location, incorporated into a device including sensor  5 , or in a separate device local to or remote from sensor  5 . 
     One or more output signals resulting from or based on the analysis are then generated. In some embodiments, the output signal(s) is generated by the device(s) or system(s) that analyze the data. The output signal(s) is directed to one or more other devices or systems that implement an action based on the output signal(s). In one embodiment, the output signal(s) is directed to one or more machine(s) or system(s), for example a valve or a medical device such as an insulin pump, that modifies the operation of the machine(s) or system(s). In one embodiment, the output signal(s) can be stored in a suitable data storage separately from, or in addition to, being sent to one or more machines or systems, for example to log actions directed by the system. 
       FIG. 9  illustrates one non-limiting example of a system  100  configured to automatically carry out an action. In this example, sensor  5  analyzes a medium  102  and generates an output signal that is sent to a control device  104  included in the system  100 . In an embodiment, the output signal may pass to remote device  106  prior to reaching control device  104 . 
     Medium  102  is a medium in which one or more analytes may be present. Medium  102  can be any medium possibly containing the one or more analytes. Medium  102  can include, but is not limited to, human tissue, animal tissue, plant tissue, an inanimate object, soil, a fluid, genetic material, or a microbe. In an embodiment, medium  102  is a flow of a fluid, such as flow of a compound through a fluid line, blood flow within a person or animal, or the like. In an embodiment, medium  102  is fluid located within a vessel, such as a beaker, cuvette, sample storage container, reaction bag or vessel, or any other such suitable vessel for containing the fluid. Non-limiting examples of medium  102  can include, for example, samples for analysis or screening such as blood samples, reaction mixtures or additions thereto such as chemical feed stocks, process outputs such as output flows from chemical reactors, drugs for administration to patients such as fluid for intravenous (IV) delivery, fluids upstream and/or downstream of filters, or any other medium where the presence or amount of an analyte can be responded to through automated controls. 
     Control device  104  is configured to act in response to a command. The control device  104  can be connected, directly or indirectly, to the system  100 . In the embodiment shown in  FIG. 9 , control device  104  is configured to wirelessly receive the command from either sensor  5  or separate device  106 . The control device can be any suitable device, such as a mechanical device, heating or cooling device, or the like, for carrying out an action determined based on detection or amounts of one or more analytes. Non-limiting examples of control device  104  include, for example, valves, pumps, flow directors, fluid metering devices, fans, heat exchangers, heating elements, or the like. In embodiments, control device  104  can control a flow that then interacts with medium  102 . For example, in one embodiment, medium  102  can be a reaction mixture and control device  104  can control a flow of a compound that is being added to the medium  102 , such as a particular reagent used in the reaction mixture. In other embodiments, control device  104  can control flow of the medium  102  itself. For example, control device  104  controlling the flow of medium  102  can operate to stop a flow of medium  102  if a contaminant is detected therein. In one embodiment, control device  104  is an insulin pump. The control device  104  can respond to a command to automatically perform an action based on the detection of the one or more analytes. The action can be any suitable action to be taken by the control device  104 . Non-limiting examples of actions taken by control device  104  include opening or closing a valve, moving an adjustable valve to a particular aperture size or flow setting, activating or deactivating a pump, setting a flow rate for a pump, selecting a duct or fluid line that a flow director allows flow to enter, providing heating or cooling to medium  102  setting a delivery rate for a controlled IV drip or an insulin pump, or the like. In an embodiment, multiple control devices  104  can each take particular actions based on detection of the one or more analytes, producing a composite response. 
     In an embodiment, the control device  104  can be co-located in a same device as sensor  5 . In another embodiment, the control device  104  can be physically separate from the sensor  5 . In an embodiment, processing of signals from sensor  5  to determine action to be taken at control device  104  can be performed at the device including sensor  5 . In an embodiment, processing of signals from sensor  5  to determine action to be taken at a control device  104  can be performed at a controller included in control device  104 . In an embodiment, the processing of signals can be performed at a controller included in a separate device  106  that is separate from both the control device  104  and the sensor  5 . In an embodiment, the separate device  106  is remote from both the sensor  5  and the control device  104 , for example being a cloud server. In an embodiment, the separate device may be in physical proximity to the sensor  5  or the control device  104 , for example being a controller for a process located in the same building or along a production line where sensor  5  is located, or, as further non-limiting examples, a mobile device such as a smart phone, tablet, computer, or the like. The processing of signals from sensor  5  results in a command for the control device  104  to implement. Sensor  5 , control device  104 , and optionally separate device  106  can respectively communicate with one another through any suitable wired connection or, as shown in the embodiment in  FIG. 9 , wireless communications or data connections such as Bluetooth, cellular data communications such 4G, 5G, LTE or the like, or Wi-Fi. 
       FIG. 10  illustrates one non-limiting example of a system configured to automatically control an insulin pump. Sensor  5  is in proximity to subject  140 , for example, being on a strap worn on the wrist of subject  140 . In the embodiment shown in  FIG. 10 , sensor  5  is configured to detect blood glucose levels in subject  140 . The subject  140  has an insulin pump  142 , configured to deliver insulin when subject  140  is in need thereof. The insulin pump  142  is configured to receive data and control the administration of insulin based on the data. The data can be a blood glucose level measured by the sensor  5 , or a command regarding the administration of insulin based on the blood glucose level measured by the sensor  5 . In an embodiment, the data can be received at the insulin pump  142  directly from sensor  5 . In this embodiment, the data can be the measurement of blood glucose to be processed at insulin pump  142 , or a signal processed at one or both of the sensor  5  and the insulin pump  142  to determine the control of the administration of insulin by insulin pump  142 . In an embodiment, sensor  5  can communicate separate device  106 , which can receive the data from sensor  5 , and convey data to insulin pump  142 . Separate device  106  can perform at least some processing of the data, for example receiving a blood glucose level from sensor  5  and processing the blood glucose level to determine the command for administering insulin from insulin pump  142 . Sensor  5 , insulin pump  142 , and optionally separate device  106  can respectively communicate with one another through any suitable wired connection or, as shown in the embodiment in  FIG. 10 , wireless communications or data connections such as Bluetooth, cellular data communications such 4G, 5G, LTE or the like, or Wi-Fi. 
     The terminology used in this specification is intended to describe particular embodiments and is not intended to be limiting. The terms “a,” “an,” and “the” include the plural forms as well, unless clearly indicated otherwise. The terms “comprises” and/or “comprising,” when used in this specification, specify the presence of the stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, and/or components. 
     The examples disclosed in this application are to be considered in all respects as illustrative and not limitative. The scope of the invention is indicated by the appended claims rather than by the foregoing description; and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.