WO2005091433A1

WO2005091433A1 - Consumption meter with integrated dual band antenna

Info

Publication number: WO2005091433A1
Application number: PCT/DK2005/000180
Authority: WO
Inventors: Poul Erik Schou-Pedersen
Original assignee: Kamstrup A/S
Priority date: 2004-03-19
Filing date: 2005-03-17
Publication date: 2005-09-29
Also published as: EP1733453A1

Abstract

The invention relates to a wireless readable consumption meter with an integrated microstrip dual band antenna. A resonator of the antenna exhibits a 1/4-wavelength first resonance within the frequency interval 400-500 MHz and exhibits a 3/4- wavelength second resonance within the frequency interval 800-1000 MHz. Preferably, the microstrip antenna part is formed on a printed circuit board that also forms an integral part with transmitting electronics and optionally other electronics parts of the meter so as to enable a compact design. The antenna is capable of for example a lower frequency of 434 MHz (ISM) and a higher frequency of 910 MHz (GSM) or 868 MHz (ISM). Preferably, the consumption meter is mounted within a protection casing also serving to provide a predetermined distance between the antenna and a surface on which the consumption meter is mounted. The casing may in addition have one or more electrically conductive surfaces which may form together with the antenna a resonator near the operating frequencies of the dual band antenna. The invention relates in addition to a system of consumption meters of the above type comprising wireless receiving means enabling the meters to wirelessly interchange measured quantity values.

Description

CONSUMPTION METER WITH INTEGRATED DUAL BAND ANTENNA

Field of the invention

The present invention relates to the field of consumption meters, more specifically the invention relates to consumption meters for wireless transmission of a measured consumed quantity. More specifically the invention relates to a consumption meter with a dual band antenna. In addition, the invention relates to a system of such consumption meters.

Background of the invention

Fig. 1 sketches a supply system with a supplier 1 providing a consumer 2 with a consumption resource such as water, heat, gas or electricity, via a supply net 3. A consumption meter 4 installed at the consumer 2 has means for wireless transmission of a consumed quantity to the supplier 1. The wireless transmission may be performed via an existing public network, such as GSM, or it may be performed via a local radio network established by the supplier 1 or by a third party service-provider.

Systems as the one sketched in Fig. 1 are known and wireless reading has a number of advantages. However, most often antennas adapted to function in the normal frequency range for this purpose, 400-1000 MHz, are bulky and vulnerable to mechanical impacts that it may be exposed to with a position inside or outside a consumer's house. Besides, the presence of separate antennas in connection with a consumption meter system increases complexity of the meter system, and thus installation costs are increased compared to meters without wireless reading facilities.

Reliability of a wireless consumption meter system is increased if the consumption meter is capable of communicating at several radio frequencies. For example the systems may be dual band systems utilizing frequency diversity between frequencies in the bands 400-500 MHz and 800-1000 Mhz. An example is a dual band system utilizing frequencies in the license-free bands 434 MHz and 868 MHz. The systems may also be dual band systems adapted for GSM and a local network frequency, such as in the range 400-500 MHz. In this way a wide range of consumers can be covered even with a limited transmitting power of 25 mW or less and it is possible to switch to the GSM net if the local net, for some consumers, does not provide a reliable coverage. However, for transmitting cost reasons the local net is preferred. Summary of the invention

It may be seen as an object of the present invention to provide a compact and robust consumption meter with means for wireless reading capable of functioning in at least two bands in the frequency range 400-1000 MHz. The consumption meter must be compact and adapted to exhibit a high efficiency in different mounting environments.

The invention complies with the object by providing in a first aspect a consumption meter for measuring a quantity value corresponding to a consumed quantity and transmitting said quantity value wirelessly to an associated remote receiver, the consumption meter comprising: - measuring means for measuring the quantity value, - transmitting means for wirelessly transmitting the measured quantity value to the associated remote receiver, and - a casing for housing the measuring means and the transmitting means, wherein the transmitting means comprises a dual band antenna comprising at least one path of electrically conductive material disposed on a surface of a substantia lly plane and electrically non-conductive substrate.

Preferably, a resonator formed by the at least one path of electrically conductive material exhibits first and second resonance frequencies. Preferably, the first resonance frequency is within the frequency interval 400-500 MHz, and the second resonance frequency is within the frequency interval 800-1000 MHz.

The non-conductive substrate may be a PCB. The PCB may comprise electronic components disposed on the PCB. The measuring means may comprise electronic components disposed on the PCB. The measuring means and the transmitting means may be integrated on a single PCB.

The casing preferably comprises a cover of an electrically non-conductive material. The casing may be adapted to provide a predetermined minimum distance between the dual band antenna and an associated object onto which the consumption meter is adapted for mounting (such as a wall etc.).

The consumption meter may further comprise an electrically conducting surface being positioned relative to the dual band antenna so as to influence transmitting properties of said dual band antenna. The electrically conductive surface may together with the at least one path of electrically conductive material exhibit a resonance frequency at or near to at least one of the first and second resonance frequencies. The electrically conductive surface may be positioned on a surface of the casing or its cover.

The consumption meter may further comprise receiving means for receiving a wireless signal from an associated transmitter using the dual band antenna.

The dual band antenna may be adapted for frequency diversity communication.

In preferred embodiments, the consumption meter is adapted to measure an amount of liquid, such as water, heat, electricity or gas.

In a second aspect the invention provides a system comprising a plurality of consumption meters, each consumption meter comprising - measuring means for measuring a quantity value, - transmitting means for wirelessly transmitting the measured quantity value to an associated remote receiver, said transmitting means comprising a dual band antenna comprising at least one path of electrically conductive material disposed on a surface of a substantially plane and electrically non-conductive material, - receiving means for receiving a wireless signal from an associated transmitter using the dual band antenna, and - a casing for housing the measuring means, the transmitting means and the receiving means, wherein the plurality of consumption meters are adapted to interchange measured quantity values using their transmitting and receiving means.

In the system according to the second aspect at least one of the plurality of consumption meters is preferably adapted to transmit a measured quantity value to an associated reading unit using its transmitting means.

A consumption meter according to the invention is by nature compact since both consumption meter means and transmitting means is housed within a single casing. Housed within a single casing the design is mechanically robust and unobtrusive. In addition, the antenna is inexpensive to manufacture and install since a limited number of separate components are involved. The simple antenna design provides an easy integration with the measuring means, either on a separate PCB or on the same PCB as the measuring means, thus the invention enables the transmitting means to be added to consumption meters involving only a limited extra cost. The simple antenna results in a manufacturing process involving only a limited number of mechanical mounting operations such as mounting of connecting wires. Mounting the consumption meter at the end user is simple since only one casing has to be mounted.

Brief description of drawings

In the following the invention is described in details with reference to the accompanying figures of which

Fig. 1 shows a sketch of a consumption meter system with wireless reading,

Fig. 2 shows a block diagram of a consumption meter,

Fig. 3 shows a PCB layout of a transmitter with an integrated microstrip antenna,

Fig. 4a shows a cross section of a consumption meter mounted on a surface, and

Fig. 4b shows a cross section of an embodiment with the antenna part having an additional conductive surface.

While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims.

Detailed description of the invention With reference to Fig. 1 a consumption meter 4 is adapted to measure a consumed electricity quantity by supplied by a distribution net 3 by an electricity supplier 1 to a consumer 2. The examples of embodiments that will be described in the following are suited for installation at a small consumer such as in a dwelling of a private consumer.

Fig. 2 shows a block diagram of a consumption meter 10 according to the invention. The consumption meter 10 comprises a measuring module 11 adapted to measure a consumed quantity of a consumption resource by performing measurements on the consumption resource flowing in 12 and out 13 of the measuring module 11. In case of an electricity meter the measuring module 11 may comprise transformers and/or shunt resistors for measuring voltage and current and calculating means for calculating from the measured voltage and current a consumed amount of electrical energy during a certain period of time. In case of a heat meter, the measuring module 11 may be adapted to measure a water input temperature, a water output temperature, and a water flow is measured. In the shown embodiment the measuring module has a display/control unit 14, for example with a Liquid Crystal Display (LCD) screen, allowing a user to read at least the measured consumed quantity and preferably also other parameters or additional information by selection from one or more user input means, such as push buttons. The display/control unit 14 may comprise control means allowing a user to force a transmission of a measured quantity value.

The measuring module 11 is connected via an interface 18 to a transmitting/receiving module 15 adapted to transmit and receive radio frequency (RF) signals. Via the interface 18 a measured consumed quantity value is transferred to the transmitting/receiving module 15 which produces and transmits an according RF signal, and the transmitting/receiving module 15 comprises a dual band microstrip antenna 16. Preferably the microstrip antenna 16 is formed on a PCB that also holds all necessary electronic signal processing means for providing an RF signal to the dual band microstrip antenna 16. If preferred, the measuring module 11 and the transmitting/receiving module 15 may be integrated on a single PCB.

The casing 17 is preferably fabricated in a electrically non-conductive material, such as a plastic material of equivalent. In order to protect the meter 10 the casing 17 is preferably encircling both measuring module 11, interface 18 and transmitting/receiving module 15. Hereby a very compact meter 10 is provided without the need to occupy unnecessary space in a consumer's dwelling.

The consumption meter 10 is adapted to wirelessly transmit a measured consumed quantity value. It may be preferred that other information data may be transmitted by the meter. The other information data may be an intermediate measurement data, such as an instantaneous consumption value, an instantaneous flow or temperature etc. In addition, the consumption meter 10 may be adapted to transmit messages regarding a detected error, such as a heat meter detecting an unusual large flow indicating a broken pipe or a defect flow sensor etc.

Preferably the consumption meter 10 is adapted also to receive wireless information via the transmitting/receiving module 15. Such information may be a request from the consumption resource supplier for data, such as a request for a consumed quantity value, or a request for other data. The resource supplier may also be able to send a message to the consumption meter 10 so as to reset a continuous consumption quantity counter etc. The supplier may also send messages to the user to be displayed on the display/control module 14. Such messages could be a current per unit resource price. Fig. 3 shows a layout of transmitting/receiving means 20 integrated on a plane PCB substrate 22 with a first part 23 having electrically conductive paths 21, 25 on its surface, these paths 21, 25 forming a microstrip dual band antenna. A second area 24 of the PCB 22 preferably holds electrically conductive paths (not visible) and electronic components (not visible) forming at least all necessary electronic means to implement the RF part of the transmitting/receiving means 20. The paths 21, 25 form the radiating elements of the antenna, and these paths 21, 25 may be formed by a metal such as copper, aluminium, brass, or silver. The paths 21, 25 may further have a layer of a protecting material such as a layer of lacquer. In order to produce a compact layout requiring only a limited PCB area 23, the conductive path 21 is seen to have a curved shape. The length of the path 21 is dictated by the desired first and second resonance frequencies at which the antenna is adapted to operate. The paths 21 are seen to be folded or curved so as to provide the required path length while occupying only a limited region of the first part of the PCB 23, hereby enabling a compact design of the total transmitting/receiving means 20.

The path 25 forms a connection path to the antenna and it is electrically connected to the RF part of the transmitting/receiving means 20, this RF part being positioned in the second area 24 of the PCB. This second part 24 may have conductive paths on either one or both sides of the PCB. Preferably, the two paths 21, 25 are electrically connected via a capacitor located in an area indicated by dotted box 26. The exact location of the capacitor depends on the desired RF parameters of the antenna. Preferably the connecting capacitor is surface mounted to the paths 21, 25 by soldering.

In the embodiment shown in fig. 3 two optional paths 27, 28 are included. One or both of these paths 27, 28 may be electrically connected to the path 21 by means of resistors or pieces of short-circuiting wire so as to increase an effective length of the path 21. Hereby it is possible by simple means to adjust RF parameters of the antenna.

In Fig. 3 only one side of the PCB 22 is visible. The other, not visible, side of the PCB 22 may have conductive paths thereon in the area 24 adapted for electronic components relating to the RF circuits. If preferred, part of the necessary electronics or all electronics may be implemented as discrete components or in an ASIC. It may even be preferred to integrate at all electronics necessary for both transmitting/receiving means and measuring means in one single ASIC. Alternatively part of transmitting/receiving electronics is implemented in a first ASIC, and part of the measuring means electronics is implemented in a second ASIC. Preferably, the other side of the PCB 22 has not conductive paths in the first part 23 where the antenna paths 21, 25 are formed. The microstrip dual band antenna according to the invention will exhibit a 1/4 wavelength resonator characteristics at a first frequency and a 3/4-wavelength resonator characteristics at a second frequency. The antenna exhibits a narrow frequency pass band. Hereby, unwanted signals are effectively attenuated thus allowing the transmitting/ receiving electronics to be very simple without the need for complicated filters etc. The detailed design of the microstrip part of the antenna, such as to adapt the design to different frequencies, is an iterative process with efficiency (gain) and bandwith as important parameters. The antenna paths 21 shown in Fig. 2 are designed to a first band of 434 MHz, i.e. the ISM band, and a second band of 868 MHz, i.e. the ISM band. Alternative shapes of electrically conductive paths 21 may be chosen thus allowing the antenna to be tuned to various frequency bands.

It may be preferred to design the antenna for a first, lower, frequency being associated with a local wireless network supported by a consumption supplier, whereas a second, higher, frequency allows the antenna to transmit/receive via the GSM network. Hereby, the same antenna design may be mass produced for use for consumers situated within a coverage area of the local supplier wireless network, whereas remotely situated consumers may have their consumption meters read with the same type of antenna but via the GSM network. Another embodiment may be tuned to a lower frequency band of 434 MHz and a higher frequency band of 868 MHz.

In order to provide a proper, predetermined RF radiating performance of the antenna part 23 of the transmitting/receiving means 20, the PCB 22 is preferably positioned at a well- defined distance to a rigid structure, i.e. as a brick wall or a conductive plate etc. The PCB may also be placed at a well-defined distance over a conductive surface which for example may be part of the casing. This is further described below.

The second part 24 of the PCB 22 has electrically conductive paths (not shown) forming an electronic circuit being part of the electronic transmitting means, i.e. high frequency (HF) amplifiers, modulating means, HF filters etc. Thus, the entire transmitting means 20, including the dual band antenna, is integrated on a single PCB 22.

As mentioned, it may be preferred to integrate on the PCB 22 also the electricity measuring means, thus enabling an integration of all electronic components of the electricity meter on a single PCB 22. In this way internal wiring between antenna, transmitting electronics, measuring electronics etc. can be completely eliminated. With a reduced or even eliminated internal wiring the meter can be manufactured efficiently, and the meter will in addition be reliable due to a reduced risk of broken wires. Fig. 4a illustrates a cross section of a consumption meter 100 mounted on a surface 130 of a rigid object, for example a wall, or on a conductive surface. A transmitting/receiving PCB 120 comprising a dual band microctrip antenna is fixed in position within a casing 110 of a non-conductive material. Preferably, the casing 110 completely encircles the PCB 120 so as to protect all internal parts of the consumption meter 100. At the same time the casing 110 must be formed of a non-conductive material, such as a plastic, so as to allow radio waves to penetrate through it without substantial attenuation. The PCB 120 is preferably fixed to the casing 110 so as to ensure that the antenna is positioned at a predetermined minimum distance d to a surface 130 on which the meter 100 is mounted. In a preferred embodiment a conductive surface is attached to the backside part of the casing, either on an inner surface or on an outer surface of the casing

The d distance from the antenna part of the PCB 120 to the rigid or conductive surface 130 on which the meter 100 is mounted is critical with respect to transmitting properties of the antenna. Therefore, the PCB 120 is fixed to the casing 110, and the casing 110 has a shape, for example including distance pieces, to ensure that the PCB 120 is in a controlled position relative to the surface 130 on which the meter 100 is mounted. Hereby it is ensured that the distance d is defined so as to provide optimal radiating properties of the antenna.

Fig. 4b illustrates a cross section of an embodiment of the consumption meter 200 with its transmitting/receiving PCB 220 fixed in position within the non-conducting casing 210, where the PCB 220 is positioned at a distance d relative to an electrically conductive surface 225. Preferably this conductive surface 225 is a metal foil or a metal sheet attached to a rear panel 215 of the casing 210, the rear panel 215 being adapted to be mounted against a wall etc. The conductive surface 225 may also be formed as a coating on the rear panel 215. Preferably, the conductive surface 225 has an extension and positioned relative to the PCB 220 so as to form a reflecting plane behind the antenna part of the PCB 220. If preferred, the conductive surface 225 may be formed as an integral part of the casing 210, for example the entire rear panel 215 of the casing 210 may be a formed as a metal sheet. Preferably, the conductive surface 225 is plane and positioned parallel to the PCB 220.

The conductive surface 225 in Fig. 4b serves to modify the radiating properties of the radiating paths of the antenna and thus the conductive surface 225 forms part of the antenna. Embodiments including a conductive surface 225 can be formed so as to be less sensitive to changes in radiating properties depending on mounting position and material of surface on which the 200 meter is mounted. This is due to the fact that the conductive surface 225 serves to shield the antenna against influence from the mounting surface and thereby it serves to reduce the amount of radiated RF energy absorbed in the mounting surface. Hereby, the conductive surface 225 improves the efficiency of the antenna.

In a preferred embodiment, the conductive surface 225 is mounted with a distance d to the PCB 220 so that it exhibits together with the conductive paths of the antenna a resonance frequency near the first resonance frequency, near the second resonance frequency, or near both of the first and second resonance frequencies. Typically, it is preferred that this resonance frequency is a few percent higher than the operation frequencies of the dual band antenna, i.e. the transmitted/received frequencies.

In still a further embodiment two or more conductive surfaces adapted to interact with the antenna may be provided so as to further increase the efficiency of the antenna. For example a first conductive surface can be positioned in relation to a rear panel of the casing, such as described above. A second conductive surface may then be positioned in relation to a side panel of the casing. In an attractive embodiment a first conducting surface forms an integral part of the rear panel of the casing and a second conducting surface forms an integral part of a side panel of the casing.

A consumption meter according to the invention will normally be mounted on an interior wall of the consumer's house. In case the meter is used in densely built-up areas or under transmission conditions that for other reasons are poor, the meter may be supplied with a socket for cable connection to an external antenna. Such external antenna may be mounted on an exterior wall of a consumer's house for better transmission.

In addition to transmission of a measured consumption quantity the meter may be adapted to transmit other types of information, for example information regarding detected errors thus allowing the supplier to take action before an error results in corrupted measurement data. The meter may also comprise means for receiving wireless information using the same integrated antenna as for transmission. The received information may be such as a request for a consumption quantity measurement from the supplier. In case the meter is not capable of receiving wireless information, a measurement value may be transmitted to the supplier with regular intervals, and/or by pushing a button on the meter.

The communication properties of the consumption meter may also be utilized to receive and retransmit or route data from or to other equipment utilizing the same network. For example a system of intercommunicating consumption meters according to the invention enables an improved coverage of the local network since, in principle, it is necessary only for the provider to be able to wirelessly communicate with one meter in the system in order to be able to access measured quantity values from all meters in the system. As long as every meter in the system is able to wirelessly communicate with at least one other meter in the system it is possible for the supplier to access data from a wide area by means of a limited number of fixed antenna units or by means of mobile reading units in a limited number of positions.

Following the above, a single type of consumption meter may be installed at all consumers coupled to a supplier's consumption net. Consumers within a coverage of the supplier's local radio network, such as an ISM network, may use this network, whereas consumers out of the range of the local network may have their meter read via the GSM network. This eliminates the need for costly on-site measurements at each consumer for deciding if the supplier's net can be used or if a GSM compatible meter should be installed instead. If later performed tests show that the supplier's net is insufficient to reach a consumer, then it may be only necessary to operate a switch on the meter in order to switch from one transmitting frequency to another without the need for changing the antenna once installed. This switching may even be performed by the supplier by calling the meter via the GSM network and then transmit data causing the meter to switch transmitting frequency. In this way it is possible to adapt an individual consumer's system with a minimum of installing costs.

It will be appreciated that any embodiment of the consumption meter according to the invention may be provided with RF transmitting and receiving means that enables utilisation of the dual band property of the antenna for a frequency diversity mode of operation.

The consumption meter according to the invention may be used in connection with metering of liquid e.g. water, heat, gas or electricity. However, the general functionality of the design allows a wide range of other applications that may profit from a compact and robust meter design.

Claims

1. A consumption meter for measuring a quantity value corresponding to a consumed quantity and transmitting said quantity value wirelessly to an associated remote receiver, the consumption meter comprising :

- measuring means for measuring the quantity value,

- transmitting means for wirelessly transmitting the measured quantity value to the associated remote receiver, and

- a casing for housing the measuring means and the transmitting means,

wherein the transmitting means comprises a dual band antenna comprising at least one path of electrically conductive material disposed on a surface of a substantially plane and electrically non-conductive substrate.

2. A consumption meter according to claim 1, wherein a resonator formed by the at least one path of electrically conductive material exhibits first and second resonance frequencies.

3. A consumption meter according to claim 2, wherein the first resonance frequency is within the frequency interval 400-500 MHz, and wherein the second resonance frequency is within the frequency interval 800-1000 MHz.

4. A consumption meter according to claim 2 or 3, wherein the non-conductive substrate is a PCB.

5. A consumption meter according to claim 4, wherein the transmitting means comprises electronic components disposed on the PCB.

6. A consumption meter according to claim 4 or 5, wherein the measuring means comprises electronic components disposed on the PCB.

7. A consumption meter according to any of the preceding claims, wherein the measuring means and the transmitting means are integrated on a single PCB.

8. A consumption meter according to any of the preceding claims, wherein the casing comprises a cover of an electrically non-conductive material.

9. A consumption meter according to any of the preceding claims, further comprising an electrically conducting surface being positioned relative to the dual band antenna so as to influence transmitting properties of said dual band antenna.

10. A consumption meter according to any of claims 9, wherein the electrically conductive surface together with the at least one path of electrically conductive material exhibits a resonance frequency at or near to at least one of the first and second resonance frequencies.

10 11. A consumption meter according to claim 9 or 10, wherein the electrically conductive surface is positioned on a surface of the casing.

12. A consumption meter according to any of the preceding claims, wherein the casing is 15 adapted to provide a predetermined minimum distance between the dual band antenn a and an associated object onto which the consumption meter is adapted for mounting.

13. A consumption meter according to any of the preceding claims, wherein the consumption meter further comprises receiving means for receiving a wireless signal from

20 an associated transmitter using the dual band antenna.

14. A consumption meter according to any of the preceding claims, wherein the dual band antenna is adapted for frequency diversity communication.

25 15. A consumption meter according to any of the preceding claims, wherein the consumption meter is adapted to measure an amount of liquid, such as water.

16. A consumption meter according to any of claims 1-14, wherein the consumption meter is adapted to measure an amount of heat.

30 17. A consumption meter according to any of claims 1-14, wherein the consumption meter is adapted to measure an amount of electricity.

18. A consumption meter according to any of claims 1-14, wherein the consumption meter 35 is adapted to measure an amount of gas.

19. A system comprising a plurality of consumption meters, each consumption meter comprising - measuring means for measuring a quantity value,

- transmitting means for wirelessly transmitting the measured quantity value to an associated remote receiver, said transmitting means comprising a dual band antenna comprising at least one path of electrically conductive material disposed on a surface of a substantially plane and electrically non-conductive material,

- receiving means for receiving a wireless signal from an associated transmitter using the dual band antenna, and

- a casing for housing the measuring means, the transmitting means and the receiving means,

wherein the plurality of consumption meters are adapted to interchange measured quantity values using their transmitting and receiving means.

20. A system according to claim 19, wherein at least one of the plurality of consumption meters is adapted to transmit a measured quantity value to an associated reading unit using its transmitting means.