WO2003036552A1

WO2003036552A1 - Remote sensor or transducer system and a mobile communication device

Info

Publication number: WO2003036552A1
Application number: PCT/FI2002/000818
Authority: WO
Inventors: Timo Varpula; Heikki SEPPÄ
Original assignee: Valtion Teknillinen Tutkimuskeskus
Priority date: 2001-10-23
Filing date: 2002-10-22
Publication date: 2003-05-01
Also published as: FI20012051A0; FI20012051A

Abstract

The present invention relates to a remote identification or sensor system. The system comprises a reader device (5) capable of sending and receiving information wirelessly with the help of electromagnetic emissions, and at least one remote identification device or remote sensor (1) adapted to generate its operating power from the incident electromagnetic radiation and to wirelessly communicate with the reader device (5) using at least one frequency(f2). According to the invention, the reader device (5) is integrated with a mobile terminal(4).

Description

Remote sensor or transducer system and a mobile communication device

The invention relates to a remote identification or sensor system according to the preamble of claim 1.

The invention also relates to a mobile terminal.

Generally, the invention is utilized in the identification objects and wireless remote reading of their specific data by electromagnetic signals.

The use of remote identification (RFID) devices is going to boom in a few year. These devices shall replace, e.g., a major portion of optically readable barcode markings on goods. A remote identification device by definition is a tag that is remotely readable by a radio-frequency signal and comprises an antenna, a circuit for generating the operating voltage, demodulator/modulator circuits of the radio- frequency signal and a memory. The memory is adapted readable by means of RF signal. Remote identification devices fall in different categories: passive and active, whereby the coupling may be inductive, capacitive or by radio frequency electric field. Passive RFID transponders generate their operating power from the radio- frequency field of the incident interrogation signal. Active transponders contain an integral battery. Inductively coupled remote identification devices typically operate at 125 kHz or 13.56 MHz. The present invention concerns passive remote identification devices readable by an RF field. The frequency bands allocated in Europe for this kind of communications are the 868 - 870 MHz band and the 2.4 - 2.4835 GHz band known as the ISM (Industrial Scientific Medical) band.

A remote sensor functions substantially in the same way as a remote identification device. Instead of the memory or in addition thereto, the sensor contains circuits for converting the reading of the measured variable (e.g., pressure, temperature and the like) into a form suitable for transmission. Due to wireless reading, remote sensors offer the benefit of operating wirelessly. In practice, sensor cabling and its installation frequently form an investment item much more expensive than the sensor itself.

In plural applications realized using a remote identification or sensor device, the goal is to achieve a maximally large distance of read communication. This maximum usable distance of communications is limited by the following factors: 1) authority regulations on the maximum permissible transmission power levels, 2) DC voltage and power consumption of the RFID transponder or remote sensor (only in passive transponders and sensors), 3) signal-to-noise ratio of reply reception at reader, and 4) spurious signals. In Europe, remote identification applications are generally permitted to operate on the above-mentioned frequency bands using a transmitted power level as low as max. 0.5 W (ERP on the 868 -870 MHz band and EIRP on the 2.45 GHz ISM band). In Finland, the maximum effective radiated power on the ISM band is only 0.1 W. In the USA, the limit of radiated power on the 915 MHz band is 1 W and, respectively, 4 W on the ISM band at 2.45 GHz. The lower permissible ERP levels of European regulations set severe limitations to the maximum read distance and data transfer rate between the reader and the remote identification device. To push the price of a single remote identification device sufficiently low, its microcircuitry must be produced using commercial technology such as the 0.5 μm CMOS process. A rough estimate of power consumption in the microcircuit is at least 5 μW when the data transfer rate is 4 kbit/s. On the basis of these design figures, theoretical maximum read/write distance is limited to less than 4 meters on the 868 - 870 MHz band and to 1.2 meters on the ISM band. Under practical circumstances involving an unfavorable mutual orientation between the transponders and reader antennas in combination with the above-mentioned constraints, the maximum read distances may remain still even substantially shorter than those cited above. Plausibly in the near future, however, a new band will be allocated around 800 MHz for remote identification applications permitting the use of about 2 W ERP. At this power level, there should be no major problem extending the read distance to 4 meters. Clearly, the higher the power level of the interrogation incident on the remote identification device the longer the maximum read distance. The ERP levels permissible for mobile phones are much higher than those permitted for remote identification devices. For instance, the maximum permissible nominal output power of a mobile phone of the second output power class operating in the GSM900 network is 8 W. At this power level, the read distance of a remote identification device can be extended to about 15 m. As a reference, it must be noted herein that the frequency band allocated for GSM900 mobile phones covers 890 - 915 MHz.

The frequency bands allocated for wireless remote identification communication and the maximum permissible transmission power levels thereof are listed in the table below:

N/A = not applicable EIRP = Equivalent Isotropic Radiated Power

ERP = Equivalent Radiated Power It is an object of the present invention to overcome the above-described problems of the prior art and to provide an entirely novel type of remote identification or sensor sensor system.

The goal of the invention is achieved by way of selecting the operating frequency of the reader device to be compatible with the operating frequency of a mobile phone, whereby the antenna of the mobile phone may also be used at the operating frequency of the remote reader device. Typically, it is desirable to set the operating frequency of the reader device as close as possible to the operating frequency of a mobile communications system. Good compatibility, however, may also be attained at frequencies falling close to the harmonics (N*f or f/N, N = integer) of the operating frequency f of the mobile communications system. In accordance with the invention, the reader device is integrated with a mobile terminal. According to a preferred embodiment of the invention, the energy emitted by a mobile terminal at its normal operating frequency is used for generating the operating power of the interrogated remote identification device or remote sensor.

More specifically, the remote identification device or remote sensor system according to the invention is characterized by what is stated in the characterizing part of claim 1.

Furthermore, a mobile terminal according to the invention is characterized by what is stated in the characterizing part of claim 8.

The invention offers significant benefits.

Among the advantages of the present invention, the following are important. Due to the operation of the remote identification devices in the microwave range close to those used by the GSM and Bluetooth standards, the reader electronics of remote identification systems can be readily integrated with existing mobile phone constructions and, moreover, at minimal extra cost. Hence, a mobile telephone appears to serve as an ideal platform for integrating the relatively simple circuitry of reader electronic. Namely, a mobile phone as such already includes a battery serving as the power supply, a display and RF circuits for transmission and reception. Then if a remote identification device is built around a sensor, the mobile phone replaces the other major components of the sensor such as the sensor battery or respective power source and reader display. In this fashion, a mobile phone can be employed as a user interface toward low-cost remote sensors. The high output power of a GSM phone facilitates remote read over a distance of 4 m and beyond or, alternatively, remote read of a power-hungry sensor at a close distance. Remote identification devices may also be used for locating a mobile phone in interior spaces. In one possible implementation of phone location, the remote identification device senses the field strength of the signal emitted by a GSM phone or an RFID reader, the measured signal strength value is stored in the memory of the RFID device and therefrom further during normal communication back to the GSM phone. Having the GSM phone at the same time communicating with a communications network server either over the GSM network or a Bluetooth connection , the server can compute the location of the mobile phone. In principle, the computation could also take place in the mobile phone with the provision that the coordinate data of the remote identification devices are loaded into the mobile phone. The method can reach a location uncertainty even smaller than 30 cm if the antennas of the remote identifica- tion devices are designed to receive signals in different polarizations. While large spaces may need a great number of remote identification devices, they are low-cost and easy-to-mount items.

In the following, the invention will be examined in greater detail with the help of exemplifying embodiments illustrated in the appended drawings in which

FIG. 1 is an illustrative diagram of a conventional remote identification/sensor system; and

FIG. 2 is an illustrative diagram of a system according to the invention. By definition, a remote identification device (RFID transponder) is a miniature tag device comprising an antenna connected to a microcircuit with a memory that can respond by sending the contents of its memory by backscatter communications responsive to an interrogation signal received from an interrogating reader device when the transponder of the tag device is scanned by an RF signal emitted by the reader. A passive RFID transponder has no battery, but instead it captures its operating power from the radio-frequency field of the interrogation signal sent toward its direction by the reader device. Energy transfer and information transmission between the remote identification device and the reader device may take place using a magnetic field, an electric field or an emitted radio- frequency signal. In many applications of the remote identification device technology, it is important that the distance from the reader device to the transponder can be made long - even up to several meters. For this purpose, it is essential to keep the power consumption of the remote identification device circuitry as low as possible.

Inasmuch as the RFID transponder is responsive to the incident interrogation signal of the reader device by backscattering the RF signal emitted by the reader device, the response signal of the remote identification device is very weak. Hence, it is essential to achieve a maximally high signal-to-noise ratio and immunity to spurious signals in the communication between the remote identification device and the reader.

Referring to FIG. 1, a typical remote identification system shown therein comprises a reader device 10 and a remote identification device 20 arranged to communicate wirelessly with each other. Generally, reader device 10 includes a processor 11, a demodulator 12 and RF circuitry 13 with an antenna 14 for generating an RF signal and receiving the same. The remote identification device 20 respectively comprises an antenna 21, a matching circuit 22, a rectifier and detector circuit 23 and a logic circuit 24. Cooperation of logic circuit 24 with matching circuit 22 takes care of the modulation functions. The remote identification device 20 is typically constructed on a thin, laminated substrate, generally in a credit card size. Now referring to FIG. 2, a typical remote identification/sensor system according to the invention comprises remote identification devices or sensors 1 with an integrated antenna 2 and a mobile terminal 4 complemented with reader means for remote read. The mobile terminal 4, such as a mobile phone 4, respectively includes a reader means 5 and an antenna 3. Other typical components of the mobile terminal 4 are a transmitter and a receiver, as well as the supplementary electronics circuitry thereof with software, and an antenna 3 suited for mobile communications at an operating frequency f₂. Additionally, the mobile terminal includes a battery serving as a power source of electric energy supply for the electronics of the transmitter and receiver sections. Further, the present mobile terminals include also a display. The mobile terminal 4 communicates at frequency fi and the reader at frequency f₂. The operating frequencies fi and f₂ are selected such that both systems can use the same antennas 2 and 3. The type of antennas is selected to be sufficiently wideband for send/receive on both frequencies. Typically, the frequencies are selected to be quite close to each other. In Europe, for instance, a remote identification system may use the 869 MHz (f₂) frequency band, while the 890 - 915 Mhz (fj) frequency band is allocated for mobile terminal communications. If the mobile phone does not commumcate at the GSM frequencies fi when a remote identification device is being interrogated, the remote identification devices (RFID circuits thereof) can capture energy for their operating voltage from the RF field emitted by the mobile phone at the frequencies f₂ reserved for the remote identification system. If the application also involves a connection to a GSM network and thereby to a server, the operating power of the remote identification devices may alternatively be generated from the RF field emitted by the mobile phone at its communications frequency fj. This optional operating mode obviously must then be taken into account when designing the antenna of the RFID device. In both cases, communications between the remote identification device or sensor 1 and the reader 5 takes place on the frequency band f₂ allocated for remote identification systems. Thus, emissions at frequency fj only offer alternative source for generating electric energy in the remote identification device or sensor 1. Next, a few exemplary embodiments of practical applications of the invention are discussed.

Example of a logistics application

Globally, some 400 million paper rolls are produced annually and each one of them is generally identified by means of a barcode label adhered on the roll. Though, a preferable arrangement would be such that places the roll identifier in the bore of the roll core, where the roll ID code is protected from damage during roll transportation and is accessible over the entire existence of the roll. As the largest rolls may have a diameter in excess of 2 m, the incident RF field must travel through a paper web mass about one meter thick. However, such a thick mass of paper web is an efficient attenuator to RF emissions. As an example, a i m thick wall of newsprint web presents an attenuation of 19 dB at 869 MHz and 52 dB at 2.45 GHz. These attenua- tion values are so high that it is impossible to interrogate a remote identification device located in the core of a 2 m dia. newsprint roll on neither of the frequency bands at the power levels allocated for remote identification systems. In contrast, interrogation becomes possible if the maximum permissible 8 W ERP level of GSM phones is used and, additionally, is focused on the RFID device by means of direc- tional antenna. In this fashion, a mobile phone can serve a dual function by both providing operating power for an RFID device and supporting an automated logistics control system in a warehouse. With the help of the mobile phone, the information of a roll being transferred may be forwarded from, e.g., a moving truck to the computer running the warehouse inventory program.

Example of a monitoring problem in the industry

In order to located ground faults or the like problems, a three-phase electric power transmission network is monitored by measuring phase-leg currents and line voltages in the terrain. This task can be carried out readily using, e.g., a measurement method based on remote sensors in the fashion discussed below. Passive voltage and current sensors attached to the high-potential conductors of the line are interrogated from the ground level by a reader connected to a mobile phone. The measurement results are automatically sent over the GSM network to a monitoring relay station. A plurality of similar monitoring systems of critical variables (vibration, pressure, temperature, etc.) may be found in process industries. With the help of the novel sensors, installa- tion becomes easy inasmuch as no cabling is needed.

Example of a consumer application

The earpiece of a mobile phone is also replaceable with a wirelessly operating micro- phone. Hereby, a small passive or battery-powered microphone is placed in the ear. The mobile phone is hung on the user's belt thus minimizing the RF field intensity incident on the user's head. The mobile phone identifies the RFID code of the remote microphone device and commands the device to generate a voice signal responsive to the digital data sent to the device on the remote identification system frequency band f₂. With the help of the individual ID codes, it is also possible to send a voice message simultaneously to a group of people located close to each other if so desired.

Examples of domestic sensor applications

A typical service meter located in customer premises comprises a sensor, read electronics and a display. Additionally, the meter needs operating power that is supplied by the mains, a battery (or a rechargeable battery). Frequently, the sensor forms only a fraction of overall manufacturing cost of the meter. By way of connecting the sensor of the meter to the sensor RFID circuit, either as an integral part of the circuit or as a separate component, a system can be established wherein a mobile phone can be used for reading measurement data so that the mobile phone (operating on an GSM or RFID frequency band) provides the operating power of the sensor device (thus substituting a battery), the processor of the mobile telephone set performs linearization and the like processing of the measurement data (thus substituting the processor of the sensor device) and the remotely interrogated measurement data can be displayed on the display of the mobile telephone (thus substituting the display of the service meter), complemented with the possibility of wirelessly sending forward the sensor measurement data (thus substituting the communications channel of the service meter). Obviously, the price of basic-type remote-readable service meters can be lowered substantially by integrating to mobile phones reading devices for RFID circuits. A simple service meter now costing 50 FBVI to 500 FIM could be implemented at a production cost of 5 FDVI to 10 FIM. An example of such a device is a hospital-grade thermometer. Today, a modern thermometer that rapidly measures the patient's temperature from his/her ear by means of an infrared radiation sensor and costs about 500 FIM could be replaced at the cost of 5 FBVI with a disposable or reusable sensor pad made on a polymer substrate suitable for placing in the patient's mouth, armpit or on the skin under clothing. Then, there is only needed a mobile phone placed nearby for monitoring the patient's temperature. When momtoring the temperature of babies, the mobile phone could be left alongside the baby patient and armed to issue an alarm if the baby patient's temperature exceed a predetermined limit. Also sweating, heart rate, etc. are measurable in the same fashion. Diapers can be sensed for their moisture content, the temperature of ham being baked can be measured prior to baking and when heating in the oven, etc. Obviously, the number of possible applications is huge. The method proposed herein is applicable to both consumer-related business and industrial purposes including product inspection and the like control/monitoring needs.

Example of location application

If a corridor or similar relatively narrow space (having a width of less than 6 m, for instance) is provided with plural low-cost remote identification device stickers (each costing less than 10 FIM displaced at, e.g., 3 m from each other, a mobile phone can identify its location rather accurately. At its best, the location uncertainty is about 30 cm, while the greatest location error is about 1 m. One alternative possibility is to design the RFID devices such that they can store their location relative to the coordinates of the building and sense the intensity of the RF field incident thereon. Next, the measurement values of the incident RF field are compressed by taking the logarithm thereof with the help of, e.g., a conversion table, before the values are stored in the memory of the RFID device. Subsequently, the value of incident field strength can be transmitted using a word length of 4 bits only. While the location system outlined herein may not be the best possible conceivable by means of RF technology in interior premises, it yet excels by its extremely fast and cost-efficient installation for mobile phones equipped with an integral reader function of RFID devices inasmuch as RFID devices are very cheap and their location can be stored wirelessly in each of them immediately after their attachment.

Without departing from the scope and spirit of the invention, the operating power to an RFID device or sensor may also be supplied by an external RF field such that emitted from a leaky cable. When implemented in family houses, for instance, this arrangement allows the read/write distance of the system to be extended and the number of sensors to be increased without any increase in the power consumption of the reader device itself. Using the same technique, an exhibition or other conference environment, for instance, can be furnished for a larger read/write distance for a large number of users.

Claims

What is claimed is:

1. A remote identification or sensor system comprising

- a reader device (5) capable of sending and receiving information wirelessly with the help of electromagnetic emissions, and

- at least one remote identification device or remote sensor (1) adapted to generate its operating power from the incident electromagnetic radiation and to wirelessly communicate with said reader device (5) using at least one frequency (f₂), in which system

- said reader device (5) is integrated with a mobile terminal (4),

characterized in that

- said system includes a plurality of remote identification devices or remote sensors (1) installed permanently in a building for position location of said reader device.

2. A remote identification or sensor system comprising

- said reader device (5) is integrated with a mobile terminal (4), characterized in that

- said system includes a plurality of remote identification devices or remote sensors (1) installed permanently on the conductors of an electric power transmission line for the purpose of monitoring the functions of an electric power transmission network.

3. A remote identification or sensor system comprising

- said reader device (5) is integrated with a mobile terminal (4),

characterized in that

- said system includes at least one remote identification device or remote sensor (1) capable of measuring the temperature or moisture content or frequency or any combination of such variables.

4. A remote identification or sensor system comprising

- a reader device (5) capable of sending and receiving information wirelessly with the help of electromagnetic emissions, and - at least one remote identification device or remote sensor (1) adapted to generate its operating power from the incident electromagnetic radiation and to wirelessly communicate with said reader device (5) using at least one frequency (f₂),

characterized in that

- said reader device (5) is integrated with a mobile terminal (4).

5. The system of claim 1, characterized in that the operating frequency (fi) of said mobile terminal (4) or a harmonic thereof is at least substantially close to the operating frequency (f₂) of said reader device (4) or a harmonic thereof.

6. The system of claim 1 or 2, characterized in that the operating frequency (fi) of said mobile terminal (4) is at least substantially close to the operating frequency (f₂) of said reader device (5).

7. The system of claim 3, characterized in that the operating frequency (fi) of said mobile terminal (4) is within the frequency band of 880 - 915 MHz and the operating frequency (f₂) of said reader device (5) is within the frequency band of 865 - 870 MHz or respectively within the frequency band of 433 - 435 MHz.

8. A mobile terminal (4) comprising

- a transmitter and a receiver, as well as the supplementary electronics circuitry thereof with software, and an antenna (3) suited for mobile communications at an operating frequency (fi), and

- a power source for providing electric operating power to said transmitter and receive electronics circuitry, characterized in that

- said mobile terminal (4) additionally includes reader device means (5) capable of facilitating communications with passive remote identification devices (1) at a second communications frequency (f₂) different from the operating frequency (fi) used by the mobile terminal.

9. The system of claim 5, characterized in that the operating frequency (fi) of said mobile terminal (4) or a harmonic thereof is at least substantially close to the operating frequency (f₂) of said reader device (4) or a harmonic thereof.

10. The system of claim 5 or 6, characterized in that the operating frequency (fi) of said mobile terminal (4) is at least substantially close to the operating frequency (f₂) of said reader device.

11. The system of claim 7, characterized in that the operating frequency (fi) of said mobile terminal (4) is in the frequency band of 880 - 915 MHz and the operating frequency (f₂) of said reader device (5) is in the frequency band of 865 - 870 MHz or respectively in the frequency band of 433 - 435 MHz.