WO2018083379A1 - Method for measuring physical characteristics and measuring arrangement to be utilized in the method - Google Patents

Method for measuring physical characteristics and measuring arrangement to be utilized in the method Download PDF

Info

Publication number
WO2018083379A1
WO2018083379A1 PCT/FI2017/050748 FI2017050748W WO2018083379A1 WO 2018083379 A1 WO2018083379 A1 WO 2018083379A1 FI 2017050748 W FI2017050748 W FI 2017050748W WO 2018083379 A1 WO2018083379 A1 WO 2018083379A1
Authority
WO
WIPO (PCT)
Prior art keywords
measuring element
microstrip line
measuring
rfid tag
physical characteristic
Prior art date
Application number
PCT/FI2017/050748
Other languages
French (fr)
Inventor
Timo Tarvainen
Timo Peltoniemi
Original Assignee
Elcoflex Oy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Elcoflex Oy filed Critical Elcoflex Oy
Publication of WO2018083379A1 publication Critical patent/WO2018083379A1/en

Links

Classifications

    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
    • G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code
    • G06K19/067—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components
    • G06K19/07—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips
    • G06K19/077—Constructional details, e.g. mounting of circuits in the carrier
    • G06K19/07749—Constructional details, e.g. mounting of circuits in the carrier the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N22/00—Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
    • G01R27/2617—Measuring dielectric properties, e.g. constants
    • G01R27/2623—Measuring-systems or electronic circuits
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
    • G01R27/2617—Measuring dielectric properties, e.g. constants
    • G01R27/2635—Sample holders, electrodes or excitation arrangements, e.g. sensors or measuring cells
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
    • G06K19/02—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the selection of materials, e.g. to avoid wear during transport through the machine
    • G06K19/025—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the selection of materials, e.g. to avoid wear during transport through the machine the material being flexible or adapted for folding, e.g. paper or paper-like materials used in luggage labels, identification tags, forms or identification documents carrying RFIDs
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
    • G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code
    • G06K19/067—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components
    • G06K19/07—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips
    • G06K19/0716—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips at least one of the integrated circuit chips comprising a sensor or an interface to a sensor
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
    • G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code
    • G06K19/067—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components
    • G06K19/07—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips
    • G06K19/0716—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips at least one of the integrated circuit chips comprising a sensor or an interface to a sensor
    • G06K19/0717—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips at least one of the integrated circuit chips comprising a sensor or an interface to a sensor the sensor being capable of sensing environmental conditions such as temperature history or pressure
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
    • G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code
    • G06K19/067—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components
    • G06K19/07—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips
    • G06K19/0723—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
    • G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code
    • G06K19/067—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components
    • G06K19/07—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips
    • G06K19/077—Constructional details, e.g. mounting of circuits in the carrier
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
    • G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code
    • G06K19/067—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components
    • G06K19/07—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips
    • G06K19/077—Constructional details, e.g. mounting of circuits in the carrier
    • G06K19/07718—Constructional details, e.g. mounting of circuits in the carrier the record carrier being manufactured in a continuous process, e.g. using endless rolls
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
    • G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code
    • G06K19/067—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components
    • G06K19/07—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips
    • G06K19/077—Constructional details, e.g. mounting of circuits in the carrier
    • G06K19/07749—Constructional details, e.g. mounting of circuits in the carrier the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
    • G06K19/07773—Antenna details
    • G06K19/07786—Antenna details the antenna being of the HF type, such as a dipole
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
    • G06K7/10009—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves
    • G06K7/10158—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves methods and means used by the interrogation device for reliably powering the wireless record carriers using an electromagnetic interrogation field
    • G06K7/10178—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves methods and means used by the interrogation device for reliably powering the wireless record carriers using an electromagnetic interrogation field including auxiliary means for focusing, repeating or boosting the electromagnetic interrogation field
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
    • G06K7/10009—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves
    • G06K7/10198—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves setting parameters for the interrogator, e.g. programming parameters and operating modes
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
    • G06K7/10009—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves
    • G06K7/10316—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves using at least one antenna particularly designed for interrogating the wireless record carriers
    • G06K7/10326—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves using at least one antenna particularly designed for interrogating the wireless record carriers the antenna being of the very-near field type, e.g. capacitive
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P3/00—Waveguides; Transmission lines of the waveguide type
    • H01P3/02—Waveguides; Transmission lines of the waveguide type with two longitudinal conductors
    • H01P3/08—Microstrips; Strip lines
    • H01P3/081—Microstriplines

Definitions

  • the invention relates to a measuring method, in which at least one measurable physical characteristic is measured from an object at several points by using sensors integrated to the physical object.
  • the invention also relates to a flexible elongated measuring element utilised in the method, the measuring sensors coupled to the measuring element being controlled by a control unit connected to the one end of the measuring element.
  • Physical properties of different objects can be measured by integrating into them measuring sensors, the measuring results of which can be read by using a wireless reader or by coupling a reader to the measuring sensor by means of a cable.
  • RFID tags Radio Frequency Identifica- tion
  • RFID systems consist of three basic components: RFID tag, RF reader and antennas both in the RFID tag and RF reader.
  • An advantage of RFID measuring is that it does not require a direct connection between the RF reader and RFID tag.
  • RFID systems can be used in different types of applications.
  • the data is saved in an RFID tag, from which there is a connection to the antenna used.
  • the antenna makes it possible to convey the data in the RFID tag to an RF reader.
  • the RF reader conveys the radio signal it has received from the RFID tag further, for example, to be interpreted by a PC.
  • RFID tags can be either active, passive or semi-passive. Passive RFID tags have no power source of their own. The very small electric current required for the use of a passive RFID tag is induced from a scanning signal on a radio frequency arriving to the antenna of the RFID tag, by means of which the RFID tag can transmit a response. The response of a passive RFID tag can be short; for example, its ID number. The lack of an own power source makes the passive RFID tag very small in size. The reading distances of passive RFID tags vary between 10 mm and 5 metres.
  • Active RFID tags contain their own power source. Their range is longer and their memory bigger. They can also save additional data transmitted by the RF reader. Because passive RFID tags are much more inexpensive, most RFID tags used are passive.
  • a passive RFID tag can be installed or integrated inside a non-conducting object or piece.
  • the permittivity of the piece is known in certain circumstances. Thus, for example, the piece's percentage of moisture or temperature can be deduced from the change in its permittivity.
  • a passive RFID tag is used, for example, to measure the moisture content of soil.
  • the RFID reader has separate antennas for a transmitter and receiver.
  • the RF reader can transmit com- mands to the RFID tag on optional frequencies.
  • a deduction of a certain physical characteristic of the object can be made from signals arriving from the RFID tags on different frequencies.
  • US 20160148025 there is described a detection sys- tern for parcelled goods in a storage, in which several adjacent RFID tags are utilised.
  • the RFID tags define with their antennas measuring values of electro-magnetic fields from their immediate surroundings.
  • the reader of the system receives the measurement data from RFID tags from a waveguide, to which each RFID tag connects electro-magnetically.
  • the reader of the system deduces from the signal value received from different RFID tags as to where the piece to be located is in the storage system.
  • the reader of the system is connected galvanically to the waveguide used in the measuring system, which waveguide is from its free end matched with a resistance corresponding to the waveguide's characteristic impedance to prevent the generation of a standing wave.
  • the RFID tags of the described system contain several different functionalities and their manufacturing costs are high. Different subcomponents for RFID tags can be fabricated with the manufacturing technique of a flexible circuit board.
  • a roll-to-roll method is utilised in the manufacture of flexible circuit boards. In the roll-to-roll method, film-type circuit board material is processed as long strips, which are rolled on coils. Different manufacturing steps of a flexible circuit board are performed in the manufacturing apparatus on the straight section arranged between the initial and receiving rolls. There can be several successive manufacturing steps.
  • the roll-to-roll manufacturing technique is very well suited to be used in case of big manufacturing lots.
  • substrates can be used, onto at least one surface of which there has been grown or laminated a metal film.
  • substrates can be used, onto at least one surface of which there has been grown or laminated a metal film.
  • manufac- turing method also several printable materials can be used, which can be dielectrics, conductive material or semiconductors.
  • manufacturing method also separate components can be connected to a semi-finished product in different steps of the manufacturing process.
  • the roll-to-roll manufacturing method it is possible to fabricate different passive and active electrical elements as well as different connection wires and waveguides to the flexible circuit board.
  • the process also makes possible the coupling of separate components, such as a microcircuit included in the RFID tag, to the flexible circuit board in connection with the manufacturing process.
  • One way to fabricate a wire or antenna onto a flexible circuit board substrate is to use an etching method, in which excessive metal on the surface of the flexible circuit board substrate is removed by a chemical etching process.
  • a metal foil covering the entire surface has been laminated onto at least one surface of the cir- cuit board substrate.
  • the metal foil can be, for example, copper laminate. If the flexible circuit board in question is double-sided, electrical connection can be created between copper laminates on different sides of the circuit board substrate via through holes.
  • the metal film can be laminated to the flexible circuit board as one manufacturing step in the roll-to-roll method.
  • So-called printable electronics can also be utilised when fabricating electrical circuit entities onto a flexible circuit board.
  • a printing plate or ink material in the printing plate touches and adheres to the material functioning as printing bed.
  • Some electrically insulating material is used as the printing bed, onto which the desired circuit entities are fabricated by printing.
  • Electrically functional, liquid or powdery materials are available for the manufacture of both electrically conductive, dielectric, semi-conductive and optical circuit elements.
  • the control unit of the measuring system reads the RFID tags using a waveguide, to which each RFID tag is coupled either galvanically or electro-magnetically.
  • the objectives of the invention are achieved with a measuring method and measuring element, in which the control unit of the measuring system guides several RFID tags through a connecting waveguide, which can be a microstrip line.
  • the control unit can command the RFID tag to transmit either the measuring result for a physical characteristic or to transmit just its identifier on two or several frequencies with the same transmission power.
  • a standing wave is generated to a waveguide with mismatched impedance on a frequency transmitted by the control unit, the RFID tags located farthermost from the control unit being positioned to the maximum points of the standing wave.
  • the losses of the microstrip line are compensate for d in RFID tags situated far from the control unit.
  • the physical characteristic to be measured can be measured with one measuring device from several different places of the object under examination.
  • the measuring element can be lengthened and that several successive RFID tags can be utilised in the same measuring element, by generating a standing wave to the waveguide, to the maximum points of which the farthermost RFID tags are connected to compensate for electrical losses in the waveguide.
  • Some embodiments are the measuring of the characteristics of wall, floor and roof elements, measuring the characteristics of stored grain, measuring the characteristics of inte- riors of transport containers, measuring the characteristics of soil, measuring the characteristics of peat, and as a measuring element for a safety floor, with which a person fallen on the floor is located.
  • the elongated flexible measuring element of physical quantities of the invention, arranged to be installed into the object to be measured is characteristic in that the measuring element comprises a microstrip line, at the first end of which there is a control unit for guiding the RFID tags of the measuring element, the control unit being arranged
  • the method according to the invention for measuring a physical characteristic in a measurement object in which method an elongated flexible measuring element con- taining a microstrip line is used, which is located in the measurement object to be measured, the measuring element comprising at least two RFID tags with antenna elements, the RFID tags connecting to the microstrip line of the measuring element either galvanically or electro-magnetically is characteristic in that the control unit at the first end of the microstrip line in the measuring element: - determines the physical characteristic to be measured with the measuring element;
  • the elongated measuring element of physical quantities of the invention comprises a substrate made of flexible dielectric material, for which there advantageously has been fabricated a waveguide in the longitudinal direction of the measuring element by using a roll-to-roll manufac- turing method, the waveguide advantageously being a microstrip line, and an antenna or antennas utilised by RFID tags.
  • the microcircuit in the RFID tags is advantageously connected to soldering points fabricated to the semi-finished measuring element.
  • the RFID tags of the measuring element can connect to the microstrip line of the measuring element either galvanically and/or electro-magnetically.
  • An RF reader is coupled to the first end of the waveguide, the reader being later also referred to as control unit.
  • the control unit is advantageously used for controlling the operation of all RFID tags of the measuring element of the invention during the measuring process.
  • the microcircuit in the RFID tags of the invention advantageously measures at least one of the following physical characteristics in the measurement objects: moisture, temperature, pressure or distance from another object.
  • the object to be measured can be, for example, a wall element, floor, roof, interior of a container, storage space, grain storage, soil or peat stack.
  • the object can also be any change caused by water content of a human or animal body in the vicinity of the antenna.
  • a standing wave can be advantageously generated to a waveguide utilised in the measuring element, to the maximum points of which the RFID tags farthermost from the control unit of the measuring system are placed to compensate for losses in the waveguide.
  • Figure 1 a illustrates in an exemplary manner the structure of an RFID tag according to a first embodiment of the invention and its cross-section in the direction A - B;
  • Figure 1 b illustrates in an exemplary manner the structure of an RFID tag according to a second embodiment of the invention and its cross-section in the direction A - B;
  • Figure 1 c illustrates in an exemplary manner the structure of an RFID tag according to a third embodiment of the invention and its cross-section in the direction A - B;
  • Figure 2a illustrates in an exemplary manner the functional main elements of the microcircuit utilised in RFID tags
  • Figure 2b illustrates in an exemplary manner a flexible measuring element of the invention, in which there are four RFID tags;
  • Figure 3 illustrates in an exemplary manner a measuring element of the invention installed to a wall element
  • Figure 4 illustrates a simulation result carried out with the measuring element of the invention, the measuring element comprising five RFID tags;
  • Figure 5 illustrates a simulation result carried out with the measuring element of the invention as a function of frequency of the attenuation of one RFID tag
  • Figure 6 illustrates a simulation result carried out with the measuring element of the invention as a function of frequency of reflection attenuation of one RFID tag; and Figure 7 illustrates as an exemplary flowchart the main steps of the measuring method of the invention.
  • FIG. 1a there is illustrated the implementation of one exemplary RFID tag 13A of the measuring element 1 A according to the first embodiment of the invention onto a flexible substrate 6 and its cross-section in the direction A - B.
  • the substrate can advantageously be polyester (PET) or polypropylene (PP).
  • the thickness of the sub- strate 6 is advantageously 175 pm.
  • the lower surface of the substrate 6 is provided with a ground plane 5 made of electrically conductive material, the thickness of which is advantageously 18 pm, the ground plane being illustrated drawn in dashed lines in the figure.
  • a conductor 2 is fabricated onto the upper surface of the substrate 6 from electrically conductive material. The thickness of the conductor is advantageously 18 pm, and its width is advantageously 350 pm.
  • the ground plane 5 and the conductor 2 together form a microstrip line with a characteristic impedance of 50 ⁇ , through which RFID tags 13A belonging to the measuring element of the invention are guided during measurements.
  • the electrically conductive material used in the manufacture of the mi- crostrip line 2 and antenna element 4 is advantageously copper, silver, aluminium or argental.
  • the electrically conductive layers can be fabricated onto the different surfaces of the substrate 6 of the measuring element 1A advantageously by using several different manufacturing methods or combining several manufacturing methods.
  • Different subcomponents of RFID tags of the measuring element of the invention can be fabricated advantageously by a manufacturing technique utilised in the manufacture of a flexible circuit board.
  • One suitable manufacturing technique is the roll- to-roll manufacturing method.
  • the roll-to-roll manufacturing method it is possible to utilise the flexible substrate 6, onto at least one surface of which there has been grown an electrically conductive film, for example, with a thin film growing method chemically or physically.
  • the electrically conductive film can also be a metal film laminated or printed onto the surface of the substrate 6.
  • Different printable materials can also be utilised in the manufacturing method, which can comprise dielectrics, electric conductors or semi-conductors.
  • separate components can also be connected to the semi-finished product in different stages of the manufacturing process.
  • the roll-to-roll manufacturing method it is also possible to fabricate different passive and active electrical elements, sensors and different coupling wires and wave- guides onto the flexible substrate 6 of the measuring element 1A.
  • the process makes it also possible to join separate components, such as a microcircuit included in an RFID tag to the flexible circuit board during the manufacturing process.
  • One way to manufacture a wire or antenna onto the flexible substrate 6 of the measuring element 1 A is to use an etching method, in which excessive metal on the sur- face of the flexible circuit board substrate is removed by using a chemical etching process.
  • a metal film covering the surface has been grown or laminated onto at least one surface of the circuit board substrate.
  • the metal film can be, for example, copper laminate. If the flexible circuit board is double-sided, an electrical connection can be created between the copper laminates on different sides of the circuit board substrate by utilizing vias.
  • So-called printable electronics can also be used in the manufacture of different electrical circuit entities, such as conductors and antennas onto the flexible substrate 6 of the measuring element 1A.
  • a printing board or ink material in the printing board contacts the material functioning as the printing bed and adheres to it.
  • An electrically dielectric material is used as the printing bed, onto which the desired circuit entities are fabricated by printing.
  • Electrically functional, liquid or powdery materials are available for the manufacture of both electrically conductive, dielectric, semi-conductive and optical circuit elements.
  • a microcircuit 3 belonging to the RFID tag 13A has been connected to the microstrip line 2 from one of its connection points 2a.
  • This connection strengthens the electro-magnetic connection of the RFID tag 13A to the microstrip line by approximately 20 dB, compared to a solution, in which the electromagnetic connection has been implemented with a purely capacitive solution.
  • a second connection point of the microcircuit 3 is coupled to the antenna element 4.
  • the ground plane 5 does not advantageously extend under the antenna element 4.
  • the antenna element 4 and microstrip line 2 are fabricated advantageously from the same electrically conductive material using the roll-to-roll manufacturing method either in the same or successive working steps.
  • the RFID tag can also comprise more antenna elements than what has been illustrated in Figure 1 a.
  • the RFID tag 13A can also comprise other sensor elements utilisable in the measuring, which are connected to the microcircuit 3 in- eluded in the RFID tag 13A (not shown in Figure 1 a).
  • the reference 8 illustrates the protective layer, with which the fabricated RFID tag 13A is protected from mechanical or chemical stresses generating in the object.
  • the protective layer 8 advantageously comprises material, the permittivity and permeability of which do not disturb the measurements made by the RFID tag 13A.
  • Figure 1 b there is illustrated the implementation of one exemplary RFID tag 13B of the measuring element 1 B of a second advantageous embodiment of the inven- tion onto the flexible substrate 6, and its cross-section in the direction A - B.
  • This embodiment differs from the embodiment in Figure 1 a in that the microcircuit 3 of the RFID tag 13B is coupled to the ground plane 5 on the lower surface of the flexible substrate 3 with an electrically conductive connection 3a from a third connection point.
  • the connection through the flexible substrate 6 to the ground plane 5 can be achieved, for example, by pressing conductive paste into a hole fabricated to the flexible substrate 6.
  • control unit of the measuring element 1 B can supply electric power from the microstrip line to the microcircuit 3 of the RFID tag 13B, because the microcircuit 3 has been galvanically coupled to the microstrip line used.
  • FIG 1c there is illustrated an implementation of one exemplary RFID tag 13C of the measuring element 1 C of a third advantageous embodiment of the invention onto the flexible substrate 6, and its cross-section in the direction A - B.
  • This embodiment differs from the embodiment in Figure 1 a in that the microcircuit 3 of the RFID tag 13C only has a capacitive connection to the microstrip line in the measuring element 1 C.
  • two antenna elements 4a and 4b are connected to the microcircuit 3 of the RFID tag 13C. The distance the antenna elements 4a and 4b with their supply wires have from the microcircuit wire 2 (distance Li) impacts the magnitude of the capacitive connection.
  • Figure 2a illustrates the functional main components of the microcircuit 3 utilised in the exemplary RFID tag.
  • the rectifier included in the RF part 31 is used to generate the operating voltage VDD for the microcircuit 3 from the RF transmission received through the antenna element 4.
  • the RF part 31 further comprises a demodulator, with which information transmitted to the RFID tag in question by the control unit of the measuring element is demod- ulated from the received RF transmission to be used by the digital control unit 32 of the microcircuit 3 in the RFID tag.
  • the RF part 31 further comprises a modulator, which modulates the identifier and measurement information from the digital control unit 32 of the microcircuit 3 into an antenna transmission, which is guided to the antenna element 4 of the RFID tag.
  • the digital control unit 32 of the microcircuit 3 controls the functions of the microcircuit 3 of the RFID tag in accordance with program routines programmed into it.
  • the digital control unit 32 can advantageously save into the memory 33 at least on a temporary basis the measuring instructions it has received from the control unit of the measuring element. Likewise, the digital control unit 32 saves the measurement data assembled from the sensor/sensors 34 at least temporarily into the memory 33.
  • the digital control unit 32 transmits the identifier data of the RFID tag saved into the memory 33 to the modulator of the RF part 31 to be transmitted further to the control unit of the measuring element.
  • the control unit of the measuring element has determined the transmission frequency used by the RFID tag and advantageously also the transmission power for the transmission going to the control unit of the measuring element.
  • the control unit of the measuring element advantageously requests the RFID tag to transmit its identifier data on several different transmission frequencies. Of the transmission amplitudes it has received on different frequencies, the control unit of the measuring element advantageously makes a deduction of the prevailing value of a certain physical char- acteristic of the measurement object.
  • the control unit 3 of the digital microcircuit 3 transmits also the measurement data received from the sensor 32 of the microcircuit 3 to the modulator of the RF part 31 .
  • the measurement data indicating a certain physical characteristic obtained from the sensor 34 of the microcircuit 3 is transmitted to the control unit of the measuring element for analysis.
  • the sensor or sensors 34 included in the microcircuit 3 can advantageously comprise one or several measuring sensors. For example, moisture, pressure or distance from an object can be measured with one measuring sensor, which measuring results are read from the sensor/sensors 34 by the digital control unit 32 of the microcircuit 3 in connection with the measuring transaction.
  • the measuring element 10 comprises at least four RFID tags 13Ai, 13A2, 13A3 and 13A fabricated onto the flexible substrate 6 using at least for the main part the roll-to-roll manufacturing method.
  • the distances of the four RFID tags in the example measured from the control unit 19 of the measuring element 10 can be multiples of the distance between the RFID tag 13Ai and the control unit 19.
  • the locations of the RFID tags 13A3 - 13A 4 farther away from the control unit 19 of the measuring element 10 can be determined on the basis of a measurement performed and/or frequency used in the microstrip line.
  • the microstrip line of the measuring element 10 on UHF frequencies is not matched from its free end to the wave impedance of the microstrip line so that a standing wave is generated to the micro- circuit wire.
  • the farthermost RFID tags for example 13A2 - 13A3, measured from the control unit 19 of the measuring element 10, are positioned so that they are located at the maximum points of the standing wave generated on the measuring frequency used in the measuring element 10.
  • the microstrip line of the measuring element can be matched from its other end with a resistance in the magnitude of the wave impedance of the microstrip line.
  • the beam of the RFID antenna extends deeper into the surrounding matter than on HF or UHF frequencies. It is an advantage of the invention that UHF, HF or LF frequency ranges can be utilised in the measuring element case-specifically so that the optimal measuring depth in the object is achieved.
  • FIG 3 illustrates an example for an application of the measuring element 10 according to Figure 2b.
  • the measuring element 10 is in- stalled inside an exemplary wall element 40.
  • the wall element 40 is factory-made, the measuring element 10 of the invention can advantageously be installed into the element already at the factory manufacturing the element.
  • the measuring element 10 is installed into the wall element, for example, with an adhesive.
  • the measuring element 10 of the invention integrated in the wall it is, for example, possible to monitor moisture, room temperature or pressure.
  • the measuring element 10 of the invention can also be used in the floor and room elements of apartments or with the measuring element it is also possible to control the functional state of the roof of a building.
  • a bed sensor for monitoring the condition of a patient.
  • a safety floor can be executed using the measuring element of the invention, the floor sensors in which monitor the movements and functional condition of the person in the room. For example, if it is detected that the person lies immovable on the floor, an alarm can be generated of the situation for the nursing personnel.
  • the measuring element of the invention can also be used for measuring the humidity and temperature of a grain storage or the moisture content of soil. Likewise, in peat production, it is possible to measure the drying of peat in peat stacks.
  • Figure 4 there is illustrated a simulation result, in which there are shown the attenuations of five successive RFID tags from a measuring element of the invention with a total length of 2m.
  • the structure and dimensions of the RFID tags are according to Figure 1 a.
  • the distance of RFID tags from each other is 40cm, and the microcircuit wire is matched to the level of 50 ⁇ .
  • the simulation frequency used is 868MHz.
  • the attenuation difference between the first RFID tag (Tag1 ) and the RFID tag farthest away from it (Tag5) is in the range of 14dB.
  • the control unit at the first end of the measuring element which in connection with RFID tags is often called the RF reader.
  • the attenuation difference between the first RFID tag and the RFID tag farthest away from it is in the range of 33dB. If the operational area of the microcircuit of the RFID tag is in the magnitude of 25dB, the farthermost RFID tags cannot be utilised when using a microstrip line with matched impedance.
  • the functionality of the three farthermost RFID tags also in this case, if a standing wave is generated to the microstrip line used, to the maximum points of which the farthermost RFID tags are placed.
  • the standing wave is generated by leaving the microstrip line of the measuring element unmatched to the char- acteristic impedance of 50 ⁇ at its free end.
  • the measuring element could comprise RFID tags both according to Figure 1 a and Figure 1 c, combined in the following way.
  • the RFID tags closest to the control unit would be implemented according to Figure 1 c as RFID tags connecting mainly capacitively, and the RFID tags farthest away from the control unit as RFID tags utilising a galvanic connection according to Figure 1 a.
  • the control unit of the measuring element can transmit signals to the microstrip line also on such a transmission power, which could damage the nearby RFID tags, if they had been coupled galvanically to the microstrip line.
  • FIG. 5 there is illustrated a simulation result for attenuation concerning one RFID tag.
  • the dimension of the RFID tag is similar to the one illustrated in connection with Figure 1 a.
  • the thickness of the substrate 6 is 175pm.
  • the lower surface of the electrically conductive ground plane 5 has a thickness of 18pm.
  • the wire 2 on the upper surface of the substrate 6 has a thickness of 8pm, and its width is 350pm.
  • Figure 6 illustrates a simulation result for return loss concerning one RFID tag.
  • the RFID tag used in the simulation has the dimensions according to Figure 1 a. In the case of one RFID tag, the return loss is approximately 5dB.
  • Figure 7 illustrates in an exemplary flowchart the main steps for a method of the invention for measuring a physical characteristic.
  • the measuring element is activated in step 70. Activation can mean either the start of continuous measuring or only one measuring action at a chosen time.
  • the control unit of the measuring element sets the next measuring frequency used and the transmission power for the measuring signal.
  • the transmission frequency set by the control unit of the measuring element can be on at least one of the following frequency ranges UHF band, HF band or LF band.
  • step 72 the control unit of the measuring element transmits on a determined frequency a signal to the microstrip line belonging to the measuring element.
  • the transmission contains the identifier data of at least one RFID tag.
  • step 73 the control unit of the measuring element makes a decision on whether the transmission request for the measurement data measured from its installation object is also shown in the transmission to the RFID tag or not. If the decision in step 73 is that the command to transmit measurement data is transmitted to the RFID tag so in step 74 the RFID tag receives the measuring command assigned to it and measures the value for the physical characteristic using the sensor of the RFID tag.
  • step 75 the RFID tag transmits the measurement data to the control unit of the measuring unit, the control unit of the measuring element receiving the response message transmitted by the RFID tag in step 76. If the decision in step 73 is that no command to transmit the measurement data is transmitted to the RFID tag, the measuring process transfers directly to step 76.
  • control unit of the meas- uring element determines the value for the physical characteristic in the measurement object from the measurement data contained in the response message.
  • step 78 whether the control unit of the measuring element transmits the value for the measured physical characteristic to the data processing device monitoring the physical condition of the monitored subject;
  • the data pro- cessing device can be, for example, a PC, into which the monitoring program for the physical characteristic measured from the object has been installed. In this case, the measuring process terminates in step 80.
  • step 77 the control unit of the measuring element determines from the microstrip line the frequency and amplitude of the transmission returning from the RFID tag.
  • the control unit of the measuring element advantageously saves the frequency received by it and the measuring values for the amplitude measured by it into its memory.
  • step 79 the new change in the measuring frequency is decided on. After this, the measuring process returns to step 71 , in which the control unit changes the frequency of the measuring signal to the frequency determined in step 79.
  • the measurement is continued in the measuring loop 71 - 79 until the measurements are detected to have been carried out on all suitable measuring frequencies in step 79.
  • step 78 it is decided in step 78 that the control unit of the measuring element transmits the value for the measured physical characteristic to the data processing device controlling the value, which can be, for example, a PC, into which the control program has been installed.
  • the measuring process terminates in step 80.
  • the invention has the following technical advantages:
  • the measuring element of the invention It is possible to manufacture the measuring element of the invention to the length of 10-15 m. In this case, it is possible to measure with one measuring element the measuring value for a physical characteristic from several points utilising only one measuring point, which is the control unit of the measuring element.
  • the measuring element of the invention can be applied in several different applications by only changing the microcircuit sensor of the RFID tag.
  • the microcircuit of the RFID tag can be of simple functionality, because it does not need to calculate the actual measuring value for the physical characteristic to be measured. By using such simple microcircuits of RFID tags, it is possible to manufacture a low-cost measuring element.

Abstract

An elongated measuring element (10) for physical characteristics fabricated onto a flexible dielectric substrate using a roll-to-roll manufacturing apparatus comprises a ground plane executed onto the lower surface of the flexible dielectric substrate (6), a microstrip line implemented onto the upper surface of the dielectric surface in its longitudinal direction, antenna elements (4) implemented adjacent to the microstrip line on the dielectric substrate, under which there is no ground plane, and at least two RFID tags (13A1, 13A2, 13A3, 13A4) fabricated on a dielectric substrate, with a microcircuit (3) for measuring at least one physical characteristic in the object. The microcircuits (3) are connected galvanically to at least one antenna element (4) and galvanically or electro-magnetically to the microstrip line. At a first end of the microstrip line there is a control unit of a measuring element to control the RFID tags, which determines the physical characteristic to be measured by the measuring element, at least one transmission frequency to be used in the microstrip line when measuring the physical characteristic, transmits the response command to at least one RFID tag of the measuring element on at least one transmission frequency, receives a response message from at least one RFID tag, and indicates the prevailing value of the physical characteristic to be measured from the received response message.

Description

Method for measuring physical characteristics and measuring arrangement to be utilized in the method
The invention relates to a measuring method, in which at least one measurable physical characteristic is measured from an object at several points by using sensors integrated to the physical object. The invention also relates to a flexible elongated measuring element utilised in the method, the measuring sensors coupled to the measuring element being controlled by a control unit connected to the one end of the measuring element. State of the art
Physical properties of different objects can be measured by integrating into them measuring sensors, the measuring results of which can be read by using a wireless reader or by coupling a reader to the measuring sensor by means of a cable.
In wireless measuring systems, so-called RFID tags (Radio Frequency Identifica- tion) are utilised in the remote reading and recording of data.
RFID systems consist of three basic components: RFID tag, RF reader and antennas both in the RFID tag and RF reader. An advantage of RFID measuring is that it does not require a direct connection between the RF reader and RFID tag. By varying the power and size of components, antenna model, operating frequency and recording capacity, RFID systems can be used in different types of applications.
In the RFID system, data transmission occurs in the following way. The data is saved in an RFID tag, from which there is a connection to the antenna used. The antenna makes it possible to convey the data in the RFID tag to an RF reader. The RF reader conveys the radio signal it has received from the RFID tag further, for example, to be interpreted by a PC.
RFID tags can be either active, passive or semi-passive. Passive RFID tags have no power source of their own. The very small electric current required for the use of a passive RFID tag is induced from a scanning signal on a radio frequency arriving to the antenna of the RFID tag, by means of which the RFID tag can transmit a response. The response of a passive RFID tag can be short; for example, its ID number. The lack of an own power source makes the passive RFID tag very small in size. The reading distances of passive RFID tags vary between 10 mm and 5 metres.
Active RFID tags contain their own power source. Their range is longer and their memory bigger. They can also save additional data transmitted by the RF reader. Because passive RFID tags are much more inexpensive, most RFID tags used are passive.
A passive RFID tag can be installed or integrated inside a non-conducting object or piece. The permittivity of the piece is known in certain circumstances. Thus, for example, the piece's percentage of moisture or temperature can be deduced from the change in its permittivity.
One such measuring method has been described in the patent publication US 20160061751 , in which a passive RFID tag is used, for example, to measure the moisture content of soil. The RFID reader has separate antennas for a transmitter and receiver. In the described measuring system, the RF reader can transmit com- mands to the RFID tag on optional frequencies. A deduction of a certain physical characteristic of the object can be made from signals arriving from the RFID tags on different frequencies.
In the application publication US 20160267769 there is presented a measuring system, in which RFID tags are read wirelessly with a separate reader. The RFID tag described in the publication measures the moisture or humidity of the surroundings from the change in impedance of the antenna it uses. A special tuning branch is included in the used antenna, the impedance of which changes along with a change in moisture. In the publication, each RFID tag is read separately and with a wireless reader. In the measuring systems described above, in which RFID tags are read each one separately, the person performing the reading action must always have exact knowledge of the reading places so that the reading transaction would succeed without difficulties.
In the application publication US 20160148025 there is described a detection sys- tern for parcelled goods in a storage, in which several adjacent RFID tags are utilised. The RFID tags define with their antennas measuring values of electro-magnetic fields from their immediate surroundings. The reader of the system receives the measurement data from RFID tags from a waveguide, to which each RFID tag connects electro-magnetically. The reader of the system deduces from the signal value received from different RFID tags as to where the piece to be located is in the storage system. The reader of the system is connected galvanically to the waveguide used in the measuring system, which waveguide is from its free end matched with a resistance corresponding to the waveguide's characteristic impedance to prevent the generation of a standing wave. It is desired to prevent a standing wave so that the connection of actual RFID tags to the waveguide would not be hindered in the described system, and that at the same time, the electro-magnetic fields in the surroundings of the RFID tag would not be disturbed, which are measured in the system to locate the object in the storage.
The RFID tags of the described system contain several different functionalities and their manufacturing costs are high. Different subcomponents for RFID tags can be fabricated with the manufacturing technique of a flexible circuit board. A roll-to-roll method is utilised in the manufacture of flexible circuit boards. In the roll-to-roll method, film-type circuit board material is processed as long strips, which are rolled on coils. Different manufacturing steps of a flexible circuit board are performed in the manufacturing apparatus on the straight section arranged between the initial and receiving rolls. There can be several successive manufacturing steps. The roll-to-roll manufacturing technique is very well suited to be used in case of big manufacturing lots.
In the roll-to-roll manufacturing method substrates can be used, onto at least one surface of which there has been grown or laminated a metal film. In the manufac- turing method, also several printable materials can be used, which can be dielectrics, conductive material or semiconductors. In the manufacturing method, also separate components can be connected to a semi-finished product in different steps of the manufacturing process.
In the roll-to-roll manufacturing method it is possible to fabricate different passive and active electrical elements as well as different connection wires and waveguides to the flexible circuit board. The process also makes possible the coupling of separate components, such as a microcircuit included in the RFID tag, to the flexible circuit board in connection with the manufacturing process. One way to fabricate a wire or antenna onto a flexible circuit board substrate is to use an etching method, in which excessive metal on the surface of the flexible circuit board substrate is removed by a chemical etching process. In this case, a metal foil covering the entire surface has been laminated onto at least one surface of the cir- cuit board substrate. The metal foil can be, for example, copper laminate. If the flexible circuit board in question is double-sided, electrical connection can be created between copper laminates on different sides of the circuit board substrate via through holes.
The metal film can be laminated to the flexible circuit board as one manufacturing step in the roll-to-roll method.
So-called printable electronics can also be utilised when fabricating electrical circuit entities onto a flexible circuit board. In this manufacturing method, a printing plate or ink material in the printing plate touches and adheres to the material functioning as printing bed. Some electrically insulating material is used as the printing bed, onto which the desired circuit entities are fabricated by printing. Electrically functional, liquid or powdery materials are available for the manufacture of both electrically conductive, dielectric, semi-conductive and optical circuit elements.
Objectives of the invention
It is an objective of the invention to introduce a measuring method utilised in the measurement of physical characteristic and a flexible measuring element, in which the value for a certain physical characteristic is measured by RFID tags in at least two places inside the selected measurement object. The control unit of the measuring system reads the RFID tags using a waveguide, to which each RFID tag is coupled either galvanically or electro-magnetically. The objectives of the invention are achieved with a measuring method and measuring element, in which the control unit of the measuring system guides several RFID tags through a connecting waveguide, which can be a microstrip line. The control unit can command the RFID tag to transmit either the measuring result for a physical characteristic or to transmit just its identifier on two or several frequencies with the same transmission power. In an embodiment of the invention, a standing wave is generated to a waveguide with mismatched impedance on a frequency transmitted by the control unit, the RFID tags located farthermost from the control unit being positioned to the maximum points of the standing wave. With the coupling arrangement, the losses of the microstrip line are compensate for d in RFID tags situated far from the control unit.
It is an advantage of the invention that the physical characteristic to be measured can be measured with one measuring device from several different places of the object under examination.
It is a further advantage of the invention that no examination objects need to be marked for a reading action in the examined object, because measuring results for the measurements made of the subject are only read from one control unit installed fixedly to the object.
It is a further advantage of the invention that the measuring element can be lengthened and that several successive RFID tags can be utilised in the same measuring element, by generating a standing wave to the waveguide, to the maximum points of which the farthermost RFID tags are connected to compensate for electrical losses in the waveguide.
It is a further advantage of the invention that it can be utilised in the measuring of the moisture, temperature and pressure of different types of objects. Some embodiments are the measuring of the characteristics of wall, floor and roof elements, measuring the characteristics of stored grain, measuring the characteristics of inte- riors of transport containers, measuring the characteristics of soil, measuring the characteristics of peat, and as a measuring element for a safety floor, with which a person fallen on the floor is located.
The elongated flexible measuring element of physical quantities of the invention, arranged to be installed into the object to be measured is characteristic in that the measuring element comprises a microstrip line, at the first end of which there is a control unit for guiding the RFID tags of the measuring element, the control unit being arranged
- to determine a physical characteristic to be measured by the measuring element;
- to determine at least one transmission frequency used in the microstrip line when measuring a physical characteristic;
- to transmit a response command to at least one RFID tag of the measuring element at least on one transmission frequency;
- to receive a response message from at least one RFID tag; and - to indicate the prevailing value of the measured physical characteristic from the received response message.
The method according to the invention for measuring a physical characteristic in a measurement object, in which method an elongated flexible measuring element con- taining a microstrip line is used, which is located in the measurement object to be measured, the measuring element comprising at least two RFID tags with antenna elements, the RFID tags connecting to the microstrip line of the measuring element either galvanically or electro-magnetically is characteristic in that the control unit at the first end of the microstrip line in the measuring element: - determines the physical characteristic to be measured with the measuring element;
- determines at least one transmission frequency used in the microstrip line when measuring the physical characteristic;
- transmits a response command to at least one RFID tag of the measuring element on at least one transmission frequency;
- receives a response message from at least one RFID tag; and
- indicates the prevailing value of the measured physical characteristic from the received response message.
Some advantageous embodiments of the invention are presented in the dependent claims.
The basic idea of the invention is the following: The elongated measuring element of physical quantities of the invention comprises a substrate made of flexible dielectric material, for which there advantageously has been fabricated a waveguide in the longitudinal direction of the measuring element by using a roll-to-roll manufac- turing method, the waveguide advantageously being a microstrip line, and an antenna or antennas utilised by RFID tags. The microcircuit in the RFID tags is advantageously connected to soldering points fabricated to the semi-finished measuring element. The RFID tags of the measuring element can connect to the microstrip line of the measuring element either galvanically and/or electro-magnetically. An RF reader is coupled to the first end of the waveguide, the reader being later also referred to as control unit. The control unit is advantageously used for controlling the operation of all RFID tags of the measuring element of the invention during the measuring process. The microcircuit in the RFID tags of the invention advantageously measures at least one of the following physical characteristics in the measurement objects: moisture, temperature, pressure or distance from another object. The object to be measured can be, for example, a wall element, floor, roof, interior of a container, storage space, grain storage, soil or peat stack. The object can also be any change caused by water content of a human or animal body in the vicinity of the antenna.
In the measuring method of the invention a standing wave can be advantageously generated to a waveguide utilised in the measuring element, to the maximum points of which the RFID tags farthermost from the control unit of the measuring system are placed to compensate for losses in the waveguide.
The invention is next explained in detail, referring to the attached drawings, in which
Figure 1 a illustrates in an exemplary manner the structure of an RFID tag according to a first embodiment of the invention and its cross-section in the direction A - B;
Figure 1 b illustrates in an exemplary manner the structure of an RFID tag according to a second embodiment of the invention and its cross-section in the direction A - B;
Figure 1 c illustrates in an exemplary manner the structure of an RFID tag according to a third embodiment of the invention and its cross-section in the direction A - B;
Figure 2a illustrates in an exemplary manner the functional main elements of the microcircuit utilised in RFID tags;
Figure 2b illustrates in an exemplary manner a flexible measuring element of the invention, in which there are four RFID tags;
Figure 3 illustrates in an exemplary manner a measuring element of the invention installed to a wall element; Figure 4 illustrates a simulation result carried out with the measuring element of the invention, the measuring element comprising five RFID tags;
Figure 5 illustrates a simulation result carried out with the measuring element of the invention as a function of frequency of the attenuation of one RFID tag;
Figure 6 illustrates a simulation result carried out with the measuring element of the invention as a function of frequency of reflection attenuation of one RFID tag; and Figure 7 illustrates as an exemplary flowchart the main steps of the measuring method of the invention.
The embodiments in the next specification are only exemplary, and one skilled in the art can carry out the basic idea of the invention also in some other way than what is described in the specification. Even though an embodiment or embodiments may be referred to in several points of the specification, this does not mean that the reference would only be focused on one described embodiment or that the described feature would be feasible only in one described embodiment. Individual features of two or several embodiments can be combined and thus achieve new em- bodiments of the invention.
In Figure 1a there is illustrated the implementation of one exemplary RFID tag 13A of the measuring element 1 A according to the first embodiment of the invention onto a flexible substrate 6 and its cross-section in the direction A - B. The substrate can advantageously be polyester (PET) or polypropylene (PP). The thickness of the sub- strate 6 is advantageously 175 pm.
The lower surface of the substrate 6 is provided with a ground plane 5 made of electrically conductive material, the thickness of which is advantageously 18 pm, the ground plane being illustrated drawn in dashed lines in the figure. A conductor 2 is fabricated onto the upper surface of the substrate 6 from electrically conductive material. The thickness of the conductor is advantageously 18 pm, and its width is advantageously 350 pm. The ground plane 5 and the conductor 2 together form a microstrip line with a characteristic impedance of 50 Ω, through which RFID tags 13A belonging to the measuring element of the invention are guided during measurements. The electrically conductive material used in the manufacture of the mi- crostrip line 2 and antenna element 4 is advantageously copper, silver, aluminium or argental.
The electrically conductive layers can be fabricated onto the different surfaces of the substrate 6 of the measuring element 1A advantageously by using several different manufacturing methods or combining several manufacturing methods. Different subcomponents of RFID tags of the measuring element of the invention can be fabricated advantageously by a manufacturing technique utilised in the manufacture of a flexible circuit board. One suitable manufacturing technique is the roll- to-roll manufacturing method. In the roll-to-roll manufacturing method it is possible to utilise the flexible substrate 6, onto at least one surface of which there has been grown an electrically conductive film, for example, with a thin film growing method chemically or physically. The electrically conductive film can also be a metal film laminated or printed onto the surface of the substrate 6. Different printable materials can also be utilised in the manufacturing method, which can comprise dielectrics, electric conductors or semi-conductors. In the manufacturing method, separate components can also be connected to the semi-finished product in different stages of the manufacturing process.
In the roll-to-roll manufacturing method it is also possible to fabricate different passive and active electrical elements, sensors and different coupling wires and wave- guides onto the flexible substrate 6 of the measuring element 1A. The process makes it also possible to join separate components, such as a microcircuit included in an RFID tag to the flexible circuit board during the manufacturing process.
One way to manufacture a wire or antenna onto the flexible substrate 6 of the measuring element 1 A is to use an etching method, in which excessive metal on the sur- face of the flexible circuit board substrate is removed by using a chemical etching process. In this case, a metal film covering the surface has been grown or laminated onto at least one surface of the circuit board substrate. The metal film can be, for example, copper laminate. If the flexible circuit board is double-sided, an electrical connection can be created between the copper laminates on different sides of the circuit board substrate by utilizing vias.
So-called printable electronics can also be used in the manufacture of different electrical circuit entities, such as conductors and antennas onto the flexible substrate 6 of the measuring element 1A. In this manufacturing method, a printing board or ink material in the printing board contacts the material functioning as the printing bed and adheres to it. An electrically dielectric material is used as the printing bed, onto which the desired circuit entities are fabricated by printing. Electrically functional, liquid or powdery materials are available for the manufacture of both electrically conductive, dielectric, semi-conductive and optical circuit elements.
In the example in Figure 1 a, a microcircuit 3 belonging to the RFID tag 13A has been connected to the microstrip line 2 from one of its connection points 2a. This connection strengthens the electro-magnetic connection of the RFID tag 13A to the microstrip line by approximately 20 dB, compared to a solution, in which the electromagnetic connection has been implemented with a purely capacitive solution. A second connection point of the microcircuit 3 is coupled to the antenna element 4. The ground plane 5 does not advantageously extend under the antenna element 4.
The antenna element 4 and microstrip line 2 are fabricated advantageously from the same electrically conductive material using the roll-to-roll manufacturing method either in the same or successive working steps.
The RFID tag can also comprise more antenna elements than what has been illustrated in Figure 1 a. In addition, the RFID tag 13A can also comprise other sensor elements utilisable in the measuring, which are connected to the microcircuit 3 in- eluded in the RFID tag 13A (not shown in Figure 1 a).
On the lower surface of the measuring element 1 A there advantageously is an adhesive layer 7, with which the measuring element 1 A can be attached to the measurement object, when needed. The reference 8 illustrates the protective layer, with which the fabricated RFID tag 13A is protected from mechanical or chemical stresses generating in the object. The protective layer 8 advantageously comprises material, the permittivity and permeability of which do not disturb the measurements made by the RFID tag 13A.
In Figure 1 b there is illustrated the implementation of one exemplary RFID tag 13B of the measuring element 1 B of a second advantageous embodiment of the inven- tion onto the flexible substrate 6, and its cross-section in the direction A - B.
This embodiment differs from the embodiment in Figure 1 a in that the microcircuit 3 of the RFID tag 13B is coupled to the ground plane 5 on the lower surface of the flexible substrate 3 with an electrically conductive connection 3a from a third connection point. The connection through the flexible substrate 6 to the ground plane 5 can be achieved, for example, by pressing conductive paste into a hole fabricated to the flexible substrate 6.
In this advantageous embodiment, the control unit of the measuring element 1 B can supply electric power from the microstrip line to the microcircuit 3 of the RFID tag 13B, because the microcircuit 3 has been galvanically coupled to the microstrip line used.
In Figure 1c there is illustrated an implementation of one exemplary RFID tag 13C of the measuring element 1 C of a third advantageous embodiment of the invention onto the flexible substrate 6, and its cross-section in the direction A - B. This embodiment differs from the embodiment in Figure 1 a in that the microcircuit 3 of the RFID tag 13C only has a capacitive connection to the microstrip line in the measuring element 1 C. In this advantageous embodiment, two antenna elements 4a and 4b are connected to the microcircuit 3 of the RFID tag 13C. The distance the antenna elements 4a and 4b with their supply wires have from the microcircuit wire 2 (distance Li) impacts the magnitude of the capacitive connection.
Figure 2a illustrates the functional main components of the microcircuit 3 utilised in the exemplary RFID tag.
From the antenna element 4 of the RFID tag there is a galvanic connection to the RF part 31 of the microcircuit 3. The rectifier included in the RF part 31 is used to generate the operating voltage VDD for the microcircuit 3 from the RF transmission received through the antenna element 4.
The RF part 31 further comprises a demodulator, with which information transmitted to the RFID tag in question by the control unit of the measuring element is demod- ulated from the received RF transmission to be used by the digital control unit 32 of the microcircuit 3 in the RFID tag.
The RF part 31 further comprises a modulator, which modulates the identifier and measurement information from the digital control unit 32 of the microcircuit 3 into an antenna transmission, which is guided to the antenna element 4 of the RFID tag. The digital control unit 32 of the microcircuit 3 controls the functions of the microcircuit 3 of the RFID tag in accordance with program routines programmed into it. The digital control unit 32 can advantageously save into the memory 33 at least on a temporary basis the measuring instructions it has received from the control unit of the measuring element. Likewise, the digital control unit 32 saves the measurement data assembled from the sensor/sensors 34 at least temporarily into the memory 33.
When the control unit of the measuring element has transmitted the command to transmit the measurement or measurement results, in one advantageous embodiment of the invention the digital control unit 32 transmits the identifier data of the RFID tag saved into the memory 33 to the modulator of the RF part 31 to be transmitted further to the control unit of the measuring element. In this embodiment, the control unit of the measuring element has determined the transmission frequency used by the RFID tag and advantageously also the transmission power for the transmission going to the control unit of the measuring element. The control unit of the measuring element advantageously requests the RFID tag to transmit its identifier data on several different transmission frequencies. Of the transmission amplitudes it has received on different frequencies, the control unit of the measuring element advantageously makes a deduction of the prevailing value of a certain physical char- acteristic of the measurement object.
In another advantageous embodiment of the invention, in addition to the identifier data of the RFID tag, the control unit 3 of the digital microcircuit 3 transmits also the measurement data received from the sensor 32 of the microcircuit 3 to the modulator of the RF part 31 . In this embodiment, the measurement data indicating a certain physical characteristic obtained from the sensor 34 of the microcircuit 3 is transmitted to the control unit of the measuring element for analysis.
The sensor or sensors 34 included in the microcircuit 3 can advantageously comprise one or several measuring sensors. For example, moisture, pressure or distance from an object can be measured with one measuring sensor, which measuring results are read from the sensor/sensors 34 by the digital control unit 32 of the microcircuit 3 in connection with the measuring transaction.
In Figure 2b there is illustrated in an exemplary manner an advantageous measuring element 10 of the invention. The measuring element 10 comprises at least four RFID tags 13Ai, 13A2, 13A3 and 13A fabricated onto the flexible substrate 6 using at least for the main part the roll-to-roll manufacturing method. The distances of the four RFID tags in the example measured from the control unit 19 of the measuring element 10 can be multiples of the distance between the RFID tag 13Ai and the control unit 19. In an advantageous embodiment, the locations of the RFID tags 13A3 - 13A4 farther away from the control unit 19 of the measuring element 10 can be determined on the basis of a measurement performed and/or frequency used in the microstrip line.
In an advantageous embodiment of the invention, the microstrip line of the measuring element 10 on UHF frequencies is not matched from its free end to the wave impedance of the microstrip line so that a standing wave is generated to the micro- circuit wire. In this advantageous embodiment, the farthermost RFID tags, for example 13A2 - 13A3, measured from the control unit 19 of the measuring element 10, are positioned so that they are located at the maximum points of the standing wave generated on the measuring frequency used in the measuring element 10. With this process, it is possible to compensate for the attenuation generating in the microstrip line in the longitudinal direction of the microstrip line so that RFID tags can be installed into the measuring element 10 farther away from the control unit 19 than what would be possible without the utilisation of the standing wave.
When utilising the measuring element of the invention on HF or LF frequencies, the microstrip line of the measuring element can be matched from its other end with a resistance in the magnitude of the wave impedance of the microstrip line.
When utilising the measuring element of the invention on LF frequencies, for example 13.56 MHz, the beam of the RFID antenna extends deeper into the surrounding matter than on HF or UHF frequencies. It is an advantage of the invention that UHF, HF or LF frequency ranges can be utilised in the measuring element case-specifically so that the optimal measuring depth in the object is achieved.
Figure 3 illustrates an example for an application of the measuring element 10 according to Figure 2b. In the example in Figure 3, the measuring element 10 is in- stalled inside an exemplary wall element 40. If the wall element 40 is factory-made, the measuring element 10 of the invention can advantageously be installed into the element already at the factory manufacturing the element. In an advantageous embodiment of the invention, for example, the measuring element 10 is installed into the wall element, for example, with an adhesive. With the measuring element 10 of the invention integrated in the wall it is, for example, possible to monitor moisture, room temperature or pressure. In the respective way, the measuring element 10 of the invention can also be used in the floor and room elements of apartments or with the measuring element it is also possible to control the functional state of the roof of a building. With the measuring element 10 of the invention it is also possible to execute, for example, a bed sensor for monitoring the condition of a patient. Likewise, a safety floor can be executed using the measuring element of the invention, the floor sensors in which monitor the movements and functional condition of the person in the room. For example, if it is detected that the person lies immovable on the floor, an alarm can be generated of the situation for the nursing personnel.
The measuring element of the invention can also be used for measuring the humidity and temperature of a grain storage or the moisture content of soil. Likewise, in peat production, it is possible to measure the drying of peat in peat stacks. In Figure 4 there is illustrated a simulation result, in which there are shown the attenuations of five successive RFID tags from a measuring element of the invention with a total length of 2m. The structure and dimensions of the RFID tags are according to Figure 1 a. In the example in Figure 4, the distance of RFID tags from each other is 40cm, and the microcircuit wire is matched to the level of 50 Ω. The simulation frequency used is 868MHz. The attenuation difference between the first RFID tag (Tag1 ) and the RFID tag farthest away from it (Tag5) is in the range of 14dB. With this kind of attenuation difference, all five RFID tags can always be read and controlled by the control unit at the first end of the measuring element, which in connection with RFID tags is often called the RF reader.
When the number of RFID tags is grown to ten, the mutual distance of RFID tags being the same, the attenuation difference between the first RFID tag and the RFID tag farthest away from it is in the range of 33dB. If the operational area of the microcircuit of the RFID tag is in the magnitude of 25dB, the farthermost RFID tags cannot be utilised when using a microstrip line with matched impedance.
It is possible to achieve the functionality of the three farthermost RFID tags also in this case, if a standing wave is generated to the microstrip line used, to the maximum points of which the farthermost RFID tags are placed. The standing wave is generated by leaving the microstrip line of the measuring element unmatched to the char- acteristic impedance of 50Ω at its free end.
Alternatively, the measuring element could comprise RFID tags both according to Figure 1 a and Figure 1 c, combined in the following way. In this embodiment, the RFID tags closest to the control unit would be implemented according to Figure 1 c as RFID tags connecting mainly capacitively, and the RFID tags farthest away from the control unit as RFID tags utilising a galvanic connection according to Figure 1 a. With such an arrangement, the control unit of the measuring element can transmit signals to the microstrip line also on such a transmission power, which could damage the nearby RFID tags, if they had been coupled galvanically to the microstrip line. When the RFID tags closest to the control unit are connected to the microstrip line merely capacitively, such a high transmission power can be attenuated by tens of decibels by a capacitive connection concerning these closest RFID tags. In this case, there is no danger for the damage of the RFID tags due to high transmission power. In Figure 5 there is illustrated a simulation result for attenuation concerning one RFID tag. The dimension of the RFID tag is similar to the one illustrated in connection with Figure 1 a. The thickness of the substrate 6 is 175pm. The lower surface of the electrically conductive ground plane 5 has a thickness of 18pm. The wire 2 on the upper surface of the substrate 6 has a thickness of 8pm, and its width is 350pm.
On the measuring frequency of 866MHz the attenuation between the microstrip line and RFID tag is approximately 9dB, when using RFID tags according to Figure 1 a.
Figure 6 illustrates a simulation result for return loss concerning one RFID tag. The RFID tag used in the simulation has the dimensions according to Figure 1 a. In the case of one RFID tag, the return loss is approximately 5dB.
Figure 7 illustrates in an exemplary flowchart the main steps for a method of the invention for measuring a physical characteristic.
The measuring element is activated in step 70. Activation can mean either the start of continuous measuring or only one measuring action at a chosen time. In step 71 , the control unit of the measuring element sets the next measuring frequency used and the transmission power for the measuring signal. The transmission frequency set by the control unit of the measuring element can be on at least one of the following frequency ranges UHF band, HF band or LF band.
In step 72, the control unit of the measuring element transmits on a determined frequency a signal to the microstrip line belonging to the measuring element. The transmission contains the identifier data of at least one RFID tag.
In step 73, the control unit of the measuring element makes a decision on whether the transmission request for the measurement data measured from its installation object is also shown in the transmission to the RFID tag or not. If the decision in step 73 is that the command to transmit measurement data is transmitted to the RFID tag so in step 74 the RFID tag receives the measuring command assigned to it and measures the value for the physical characteristic using the sensor of the RFID tag.
In step 75, the RFID tag transmits the measurement data to the control unit of the measuring unit, the control unit of the measuring element receiving the response message transmitted by the RFID tag in step 76. If the decision in step 73 is that no command to transmit the measurement data is transmitted to the RFID tag, the measuring process transfers directly to step 76.
If the control unit has received measurement data on the measured physical characteristic from the RFID tag in step 76, then in step 77, the control unit of the meas- uring element determines the value for the physical characteristic in the measurement object from the measurement data contained in the response message.
After this it is decided in step 78, whether the control unit of the measuring element transmits the value for the measured physical characteristic to the data processing device monitoring the physical condition of the monitored subject; the data pro- cessing device can be, for example, a PC, into which the monitoring program for the physical characteristic measured from the object has been installed. In this case, the measuring process terminates in step 80.
If it has been decided in step 73 that no actual command to measure a physical characteristic is to be transmitted to the RFID tag, but only a command to transmit the RFID identifier, then in step 77 the control unit of the measuring element determines from the microstrip line the frequency and amplitude of the transmission returning from the RFID tag. The control unit of the measuring element advantageously saves the frequency received by it and the measuring values for the amplitude measured by it into its memory. In this second embodiment of the method of the invention, it is decided in step 78 that the respective amplitude measurement is made also on some other transmission frequency. In step 79, the new change in the measuring frequency is decided on. After this, the measuring process returns to step 71 , in which the control unit changes the frequency of the measuring signal to the frequency determined in step 79.
The measurement is continued in the measuring loop 71 - 79 until the measurements are detected to have been carried out on all suitable measuring frequencies in step 79.
After this, also in this embodiment it is decided in step 78 that the control unit of the measuring element transmits the value for the measured physical characteristic to the data processing device controlling the value, which can be, for example, a PC, into which the control program has been installed. In this case, the measuring process terminates in step 80. The invention has the following technical advantages:
It is possible to manufacture the measuring element of the invention to the length of 10-15 m. In this case, it is possible to measure with one measuring element the measuring value for a physical characteristic from several points utilising only one measuring point, which is the control unit of the measuring element.
The measuring element of the invention can be applied in several different applications by only changing the microcircuit sensor of the RFID tag.
Further, the microcircuit of the RFID tag can be of simple functionality, because it does not need to calculate the actual measuring value for the physical characteristic to be measured. By using such simple microcircuits of RFID tags, it is possible to manufacture a low-cost measuring element.
In addition, by combining different embodiments of the invention, it is possible to manufacture measuring elements, the lengths of which are sufficient even for large applications. Above there has been described some advantageous embodiments of the measuring method of the invention and of the measuring element utilised in the measuring method. The invention is not limited to the embodiments described above, but the inventional idea can be applied in numerous way within limits set by the patent claims.

Claims

Patent claims
1 . An elongated measuring element (10) for measuring physical characteristics, which is configured to be installed into an object (40) to be measured, the measuring element (10) being manufactured with a roll-to-roll manufacturing apparatus onto a flexible dielectric elongated substrate (6), the measuring element (10) comprising:
- a ground plane (5) executed onto a lower surface of a dielectric substrate (6);
- a microstrip line (2) executed onto the upper surface of the dielectric substrate (6) in its longitudinal direction;
- antenna elements (4, 4a, 4b) implemented adjacent to the microstrip line onto a dielectric substrate (6), no ground plane (5) being present under the antenna elements;
- at least two RFID tags (13A, 13B) fabricated onto the dielectric substrate (6), the tags comprising a microcircuit (3) for measuring at least one physical char- acteristic in an object, which microcircuits (3) are connected to the microstrip line (2) galvanically or electro-magnetically and galvanically to at least one antenna element (4, 4a, 4b);
characterised in that at a first end of the microstrip line (2) there is a control unit of the measuring element (10) for controlling the RFID tags (13A, 13B, 13C), the con- trol unit being configured:
- to determine a physical characteristic to be measured by the measuring element (10);
- to determine (71 ) at least one transmission frequency used in the microstrip line (2) when measuring the physical characteristic;
- to transmit (72) a response command to at least one RFID tag (13A, 13B,
13C) of the measuring element on at least one transmission frequency;
- to receive (76) a response message from at least one RFID tag (13A, 13B, 13C); and
- to indicate (77) the prevailing value of the physical characteristic to be meas- ured from the received response message.
2. The measuring element according to claim 1 , characterised in that the value for the physical characteristic is configured to be determined in the control unit of the measuring element (10) from signal amplitudes of the response message containing the identifier of the RFID tag on at least two different transmission frequen- cies.
3. The measuring element according to claim 1 , characterised in that the RFID tag (13A, 13B, 13C) is configured to measure by a command of the control unit of the measuring element (10) the value for the physical characteristic in the object (40) and to transmit (7) the measurement data to the control unit of the measuring element (10).
4. The measuring element according to claim 1 , 2 or 3, characterised in that the transmission frequency used is on the UHF band, HF band or LF band.
5. The measuring element according to claim 1 , characterised in that at least one of the connection points (2a) in the microcircuit (3) of an RFID tag (13A, 13B, 13C) is connected galvanically to the microstrip line (2).
6. The measuring element according to claim 5, characterised in that a second connection point in the microcircuit (3) of an RFID tag (13A, 13B, 13C) is connected (3a) to the ground plane (5) of the microstrip line (2) for supplying power to the microcircuit (3) of the RFID tag.
7. The measuring element according to claim 1 , 5 or 6, characterised in that at a second free end of the microstrip line, the microstrip line (2) is not matched to the pure resistance corresponding to the characteristic impedance of the microstrip line on UHF frequencies to generate a standing wave to the microstrip line.
8. The measuring element according to claim 7, characterised in that the RFID tags (13A2, 13A3) closest to the second free end of the microstrip line (2) are installed into the maximum points of the standing wave generating to the microstrip line (2) on UHF frequencies for compensating for the power loss generating in the longitudinal direction of the microstrip line (2).
9. The measuring element according to claim 1 , characterised in that the mi- crostrip line (2), the ground plane (5) and the antenna elements (4, 4a, 4b) are manufactured either
on both sides of a coppered substrate by etching from copper films;
by printing conductive material onto at least one surface of the dielectric substrate;
- by laminating the ground plane onto the lower surface of the substrate and by printing the microstrip line and antenna elements onto the upper surface of the substrate; or
by thin film technology by growing conductive material onto the substrate either chemically or physically.
10. The measuring element according to claim 1 or 9, characterised in that the microstrip line (2), the ground plane (5) and the antenna elements (4, 4a, 4b) are fabricated using at least one of the following materials: copper, silver, aluminium or argental.
1 1 . The measuring element according to claim 1 , characterised in that the micro- circuit (3) of an RFID tag (13A, 13B, 13C) comprises:
- an RF front part (31 ) for receiving RF signals from at least one antenna element (4, 4a, 4b) and for transmitting RF signals to at least one antenna element (4, 4a, 4b) and a rectifier for generating operating voltage for the microcircuit from an RF signal received from an antenna element;
- a digital control unit (32) for controlling functions of the microcircuit (3);
- a sensor (34) for measuring at least one physical characteristic; and
- a memory unit (33) for saving the measurement data of the sensor at least temporarily.
12. The measuring element according to claim 1 1 , characterised in that the physical characteristic to be measured by the microcircuit (3) of an RFID tag (13A, 13B, 13C) is moisture, temperature or pressure.
13. The measuring element according to 1 or 12, characterised in that the physical characteristic to be measured by the microcircuit (3) of an RFID tag (13A, 13B, 13C) is configured to be measured from a wall structure, floor structure, roof structure, bed, seat, grain storage, container, dielectric material, soil or peat.
14. Measuring method for measuring at least one physical characteristic in a measurement object (40), in which method an elongated flexible measuring element (10) contained in a microstrip line (2) is used, the measuring element being placed into the measurement object (40) to be measured, and further comprising at least two RFID tags (13A, 13B, 13C) with antenna elements (4, 4a, 4b), which RFID tags are connected to the microstrip line (2) of the measuring element (10) either galvan- ically or electro-magnetically,
characterised in that the control unit at a first end of the microstrip line contained in the measuring element:
- determines a physical characteristic to be measured by the measuring element (10);
- determines (71 ) at least one transmission frequency used in the microstrip line (2) when measuring the physical characteristic; - transmits (72) a response command to at least one RFID tag (13A, 13B, 13C) of the measuring element on at least one transmission frequency;
- receives (76) a response message transmitted by at least one RFID tag (13A, 13B, 13C); and
- indicates (77) the prevailing value of the physical characteristic to be measured from the received response message.
15. The measuring method according to claim 14, characterised in that a standing wave is generated to the microstrip line (2) on UHF frequency, when the microstrip line (2) is not matched to the pure resistance corresponding to its characteristic im- pedance at a second free end of the microstrip line (2).
16. The measuring method according to claim 15, characterised in that the RFID tags (13A2, 13A3) closest to the second free end of the microstrip line are installed on UHF frequency to the microstrip line (2) at maximum points of the standing wave for compensating the power loss in the microstrip line (2).
17. The measuring method according to claim 14 or 16, characterised in that the transmission frequency used in the measuring element (10) is changed (79) and that the value for the physical characteristic in the object is determined from amplitude values of the response messages transmitted by the RFID tag (13A, 13B, 13C) on at least two frequencies.
18. The measuring method according to claim 17, characterised in that the physical characteristics to be measured is moisture, temperature or pressure.
PCT/FI2017/050748 2016-11-01 2017-10-30 Method for measuring physical characteristics and measuring arrangement to be utilized in the method WO2018083379A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI20165821A FI128912B (en) 2016-11-01 2016-11-01 Method of measuring physical quantities, and measuring arrangement used in the method
FI20165821 2016-11-01

Publications (1)

Publication Number Publication Date
WO2018083379A1 true WO2018083379A1 (en) 2018-05-11

Family

ID=62076757

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/FI2017/050748 WO2018083379A1 (en) 2016-11-01 2017-10-30 Method for measuring physical characteristics and measuring arrangement to be utilized in the method

Country Status (2)

Country Link
FI (1) FI128912B (en)
WO (1) WO2018083379A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2020142766A1 (en) * 2019-01-04 2020-07-09 Hodges John W Apparatus for in vivo dielectric spectroscopy

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7038470B1 (en) * 2003-12-10 2006-05-02 Advanced Design Consulting, Usa, Ind. Parallel-plate capacitive element for monitoring environmental parameters in concrete
US20060145861A1 (en) * 2004-12-31 2006-07-06 Forster Ian J RFID devices for enabling reading of non-line-of-sight items
US20060261946A1 (en) * 2005-05-19 2006-11-23 International Business Machines Corporation System and method to record environmental condition on an RFID tag
US20100109846A1 (en) * 2007-09-05 2010-05-06 Brother Kogyo Kabushiki Kaisha Microstrip antenna and apparatus for reading rfid tag information
US20100165557A1 (en) * 2007-07-19 2010-07-01 Lapp Engineering & Co. Cable receiving unit
US20160061751A1 (en) * 2014-08-28 2016-03-03 William N. Carr Wireless Impedance Spectrometer
US20160253534A1 (en) * 2013-11-11 2016-09-01 Nec Corporation Article management system and article management method

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7038470B1 (en) * 2003-12-10 2006-05-02 Advanced Design Consulting, Usa, Ind. Parallel-plate capacitive element for monitoring environmental parameters in concrete
US20060145861A1 (en) * 2004-12-31 2006-07-06 Forster Ian J RFID devices for enabling reading of non-line-of-sight items
US20060261946A1 (en) * 2005-05-19 2006-11-23 International Business Machines Corporation System and method to record environmental condition on an RFID tag
US20100165557A1 (en) * 2007-07-19 2010-07-01 Lapp Engineering & Co. Cable receiving unit
US20100109846A1 (en) * 2007-09-05 2010-05-06 Brother Kogyo Kabushiki Kaisha Microstrip antenna and apparatus for reading rfid tag information
US20160253534A1 (en) * 2013-11-11 2016-09-01 Nec Corporation Article management system and article management method
US20160061751A1 (en) * 2014-08-28 2016-03-03 William N. Carr Wireless Impedance Spectrometer

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2020142766A1 (en) * 2019-01-04 2020-07-09 Hodges John W Apparatus for in vivo dielectric spectroscopy
US10921274B2 (en) 2019-01-04 2021-02-16 John W. Hodges Apparatus for in vivo dielectric spectroscopy

Also Published As

Publication number Publication date
FI20165821L (en) 2018-05-02
FI20165821A (en) 2018-05-02
FI128912B (en) 2021-03-15

Similar Documents

Publication Publication Date Title
EP2774085B1 (en) Array of rfid tags with sensing capability
Marrocco et al. Multiport sensor RFIDs for wireless passive sensing of objects—Basic theory and early results
JP5619997B2 (en) Antenna for wet environment
EP1899745B1 (en) Measuring system and method for detecting radio-frequency tags
EP2779033A1 (en) Shielded cavity backed slot decoupled RFID tags
US8786441B2 (en) Radio frequency identification tag
Suwalak et al. Determination of dielectric property of construction material products using a novel RFID sensor
US10833531B2 (en) Electric power generation or distribution asset monitoring
Ali et al. RFID Humidity Sensor Tag for Low-cost Applications.
WO2018083379A1 (en) Method for measuring physical characteristics and measuring arrangement to be utilized in the method
EP3309896A1 (en) Ball-grid-array radio-frequency integrated-circuit printed-circuit-board assembly for automated vehicles
WO2006078147A1 (en) Thin rfid tag for radio frequency identification
JP2011049711A (en) Antenna substrate and ic tag
JP2007310898A (en) Non-contact type ic module and method for manufacturing non-contact type ic module
KR101459768B1 (en) Antenna
KR101294579B1 (en) Antenna
US8730045B2 (en) Isolating and RFID-based sensor from environmental interference
US11734542B2 (en) Transponder label and method for manufacturing a transponder label
CN103036002B (en) Sensing equipment
KR101349519B1 (en) Antenna
KR20080097117A (en) Radio frequency identification devices
US11921055B2 (en) Surface change detector and surface change detection method using same
Michisaka Novel sensing techniques of chipless RFID sensor for infrastructure
US20200024566A1 (en) Material Metric Measurement
Virtanen Development of Sensor Integrated and Inkjet-Printed Tag Antennas for Passive UHF RFID Systems

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 17867100

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 17867100

Country of ref document: EP

Kind code of ref document: A1