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EP 0 718 908 B1 |
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EUROPEAN PATENT SPECIFICATION |
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Mention of the grant of the patent: |
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31.10.2001 Bulletin 2001/44 |
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Date of filing: 22.12.1994 |
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A circuit arrangement for the transmission of an RF signal
Schaltungsanordnung für die Übertragung eines Hochfrequenzsignals
Montage de circuit pour la transmission d'un signal à fréquence radio
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Designated Contracting States: |
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DE FR GB IT NL |
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Date of publication of application: |
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26.06.1996 Bulletin 1996/26 |
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Proprietor: TEXAS INSTRUMENTS DEUTSCHLAND GMBH |
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85356 Freising (DE) |
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Inventor: |
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- Winterer, Albert
D-84095 Furth (DE)
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Representative: Schwepfinger, Karl-Heinz, Dipl.-Ing. |
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Prinz & Partner GbR
Manzingerweg 7 81241 München 81241 München (DE) |
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References cited: :
EP-A- 0 297 790 GB-A- 2 268 032 US-A- 4 904 995
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EP-A- 0 531 125 JP-A- 61 123 303 US-A- 5 227 805
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- MOTOROLA TECHNICAL DEVELOPMENTS, vol. 19, June 1993 SCHAUMBURG, ILLINOIS US, pages
91-93, XP 000361491 HERTZ ET AL. 'HOUSING COVER PLATES: BATTERY CONTACT AND ELECTROMAGNETIC
WAVE COUPLER'
- PATENT ABSTRACTS OF JAPAN vol. 10 no. 313 (E-448) [2369] ,11 June 1986 & JP-A-61 123303
(MATSUSHITA ELECTRIC)
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Note: Within nine months from the publication of the mention of the grant of the European
patent, any person may give notice to the European Patent Office of opposition to
the European patent
granted. Notice of opposition shall be filed in a written reasoned statement. It shall
not be deemed to
have been filed until the opposition fee has been paid. (Art. 99(1) European Patent
Convention).
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[0001] The invention relates to a circuit arrangement for the transmission of an RF signal
as defined in the precharacterizing part of claim 1.
[0002] A circuit arrangement of this type is known from JP-A 61 123 303.
[0003] The amount of electrical power or water used by private or industrial customers has
so far been determined by reading meters on the premises. In this respect it is necessary
for the persons employed for this purpose to go to the premisses where the respective
meter is installed, to note down the readings and then to pass them to a central office
for processing. Attempts are now being made to use a transmit module to transmit the
readings for the electricity or water consumed by means of a RF signal containing
the respective readings. The RF signal may for example be received with the aid of
receiving systems in vehicles, which drive past the buildings wherein the respective
meters are installed. Taking the readings will then no longer involve personal attendance
and inspection of the meters.
[0004] However radio modules to be installed on the meter have to meet stiff requirements.
More particularly such a module must be small in size and cheap for it to be able
to be mounted in or on the meter without an excessive amount of space being required.
[0005] One object of the invention is to provide a circuit of the type initially mentioned
such that it can be mounted with only a small space requirement on an electricity
or water meter while at the same time not entailing high manufacturing costs.
[0006] This object is to be fulfilled in a circuit arrangement of this type as specified
above which is provided with the features of the characterizing part of claim 1.
[0007] A particular reason for its being possible for the circuit arrangement in accordance
with the invention to be produced in a particularly space saving and cheap form is
that it does not require any antenna of its own, but achieves effective signal radiation
because of the provision of an electrical counter-weight to the antenna formed by
the battery.
[0008] One embodiment of the invention will now be described with reference to the drawings
in more detail.
Figure 1 is a circuit diagram of the circuit arrangement in accordance with the invention.
Figure 2 is a diagrammatic representation of one possible application of the circuit
in accordance with the invention in connection with an electricity or water meter.
[0009] The circuit arrangement depicted in figure 1 comprises a transmit circuit 10 with
an operating voltage or power connection 14 itself connected with an operating voltage
or power line 12 and a ground connection 18 connected a ground line 16.
[0010] An RF signal produced by the transmit circuit 10 is supplied at an output 20 and
to an impedance matching circuit 22, which comprises two variable capacitors C1 and
C2 and a coil L1. The impedance matching circuit 22 has the form of a p element, in
which the capacitors C1 and C2 are at one end connected with ground, whereas the other
ends are connected together by the coil L1. The one end of the coil L1 is in this
case connected with the output 20 of the transmit circuit 10, and the other end of
the coil L1 is connected with the output of the impedance matching circuit 22. The
coil L2 transfers the output signal of the impedance matching circuit 22 to the metallic
outer casing of a battery 24, whose internal pole is connected via a coil L3 with
the ground line 16. In the illustrated working embodiment of figure 1 the external
casing of the battery 24 constitutes the positive terminal, but however it is also
possible to utilize a battery whose external casing constitutes the negative terminal.
The positive terminal of the battery 24 is connected via a coil L4 with the operating
voltage or power line 12 so that the positive operating or power voltage may be applied
to the terminal 14 of the transmit circuit 10. Between the positive operating voltage
line 12 and the ground line 16 a further capacitor C3 is arranged.
[0011] In the case of the employment of a currently used type of battery, as for instance
a lithium battery, as the battery 24 the positive terminal will act as an antenna,
and the coil L2 will function as an antenna extension coil. The coil L2 is so dimensioned
with that the RF signal may be supplied to the positive terminal of the battery 24.
On the other hand the coil L4 is of such a size that it functions as a blocking element
for the RF oscillation, which is supplied to the positive terminal of the battery
24. The coil L4 consequently only transmits the positive operating voltage to the
operating voltage line 12, whereas the RF signal is radiated by the battery 24 acting
as an antenna. The capacitor C3 has the purpose of conducting away to ground the RF
fractions, with which the operating voltage at the operating voltage or power line
12 might be modulated. In order for the battery to actually operate as an antenna,
the negative terminal is decoupled from the ground line by the coil L3 so that an
RF signal transmitted to the battery 24 may not be conducted away to ground.
[0012] By means of a suitable adjustment of the capacitors C1 and C2 and the select of a
suitable size of the coil L1, it is possible to arrive at an impedance match, which
has the consequence that the RF signal provided at the output 20 of the transmit circuit
10 is transmitted with a high efficiency to the positive terminal of the battery 24.
[0013] In practice it has been seen the in the case of the use of a lithium battery, whose
outer casing is the plus pole, for the intended purpose the battery is suitable as
an antenna. However a battery will also radiate in a satisfactory manner, if its external
casing is connected with the minus pole.
[0014] Figure 2 diagrammatically indicates how the circuit arrangement to be described here
may be designed in an advantageous manner and how it can be connected with a water
meter. In this case the transmit circuit 10 and all other components of the circuit
arrangement of figure 1 with the exception of the battery 24 are in one block 26 on
a printed circuit board 28 composed of three layers, that is to say an upper conductor
board layer 30, a middle conductor board layer 32 and a lower conductor board layer
34. In a first embodiment, which is represented in figure 2, conductive paths are
formed on the basis of the upper conductor layer 30, which produce the desired circuit
connections between the components of the circuit. The middle conductor board layer
32 in this case constitutes the ground line 16 and on the lower conductor board layer
34 conductive paths are also formed, which may produce circuit connections between
the components. In a conventional fashion the through hole connections between the
conductive paths of the upper conductor layer 30 and the lower conductor layer 34
are produced, such through hole connections not being connected with the conductor
layer 32. The conductor layer 32, which acts as an electrical counter-weight to the
antenna constituted by the battery 24, is recessed in the part underneath the battery
since it would otherwise interfere with the counter-weight function.
[0015] In a further embodiment, which is not illustrated in figure 2, the middle conductor
layer 32 is employed as a ground line. In this case as well the layer 34 underneath
the battery 24 is removed so that it can perform its function as a counter-weight
to the antenna.
[0016] The printed circuit board 28 is located together with the components mounted on it
in a housing 36 of plastic, which is metallized on the internal and external surfaces
38 and 40.
[0017] The housing 36 is placed in position with the aid of attachment means (not illustrated)
on the metallic housing 42 of a water meter 44, which is only indicated diagrammatically
in figure 2. It is standard practice for the conduction layer 32 or 34, which is connected
with the ground line, to be connected with the housing 42 of the water meter, because
there is then optimum efficiency as regards radiation in the RF signal. However in
cases where such a galvanic coupling is not possible, it is possible to produce a
satisfactory capacitive coupling between the conductor layer of the printed circuit
board 28 and the housing 38 consisting of metal, this also being something responsible
for an improvement in the electrical counter-weight as regards the antenna constituted
by the battery 24.
1. A circuit arrangement for the transmission of an RF signal comprising a transmit circuit
(10) for the production of the RF signal, an antenna (24) for the radiation of the
RF signal, an impedance matching circuit (22) arranged between the antenna (24) and
the output (20) of the transmit circuit (10) and a battery (24) for the application
of the operating voltage between a positive operating voltage line (12) and a ground
line (16), wherein the positive operating voltage line (12) and the ground line (16)
are decoupled from the battery (24) with respect to the RF signal and the RF signal
from the output (20) of the transmit circuit (10) is applied to a terminal of the
battery (24) so that the part of the battery (24) connected with this terminal constitutes
the antenna, characterized in that the transmit circuit (10), the impedance matching circuit (22) and the battery (24)
are mounted on a printed circuit board (28) having an upper, a middle and a lower
conductor layer (30, 32, 34), conductive paths being provided on one of said middle
or lower conductor layers (32, 34), and the other of said middle or lower conductor
layers being galvanically separated from the other layers, and in that the ground line (16) is connected with the galvanically separated conductor layer
(32 or 34) and constitutes an electrical counter-weight to the antenna formed by the
battery (24).
2. The circuit arrangement as claimed in claim 1, characterized in that the application of the RF signal to the terminal of the battery (24) is performed
via an antenna extension coil (22).
3. The circuit arrangement as claimed in claim 1 or in claim 2, characterized in that the RF signal is applied to the terminal of the battery (24) connected with the external
casing of the battery.
4. The circuit arrangement as claimed in claim 1, 2 or 3, characterized in that the conductor layer (32; 34) connected with the ground line (16) is galvanically
connected with the housing (42) of the electricity or water meter (44).
5. The use of the circuit arrangement as claimed in claim 1, 2 or 3 in the case of an
electricity or water meter (44) with a metallic housing (42), the RF signal to be
transmitted containing data on readings taken from the electricity or water meter
(44), characterized in that the circuit arrangement is accommodated in a plastic housing (36) internally and
externally metallized in order to produce a capacitive coupling between the ground-connected
conductor layer (32; 34) and the housing (38) of the electricity or water meter (44).
1. Schaltungsanordnung zum Senden eines HF-Signals, mit einer Sendeschaltung (10) für
die Erzeugung des HF-Signals, einer Antenne (24) für die Abstrahlung des HF-Signals,
einer Impedanzanpassungsschaltung (22), die zwischen der Antenne (24) und dem Ausgang
(20) der Sendeschaltung (10) angeordnet ist, und einer Batterie (24) zum Anlegen der
Betriebsspannung zwischen einer Leitung (12) für positive Betriebsspannung und einer
Masseleitung (16), wobei die Leitung (12) für positive Betriebsspannung und die Masseleitung
(16) von der Batterie (24) in bezug auf das HF-Signal entkoppelt sind und das HF-Signal
vom Ausgang (20) der Sendeschaltung (10) an einen Anschluß der Batterie (24) angelegt
wird, so daß derjenige Teil der Batterie (24), der mit diesem Anschluß verbunden ist,
die Antenne bildet, dadurch gekennzeichnet, daß die Sendeschaltung (10), die Impedanzanpassungsschaltung (22) und die Batterie (24)
auf einer gedruckten Leiterplatte (28) angebracht sind, die eine obere, eine mittlere
und eine untere Leiterschicht (30, 32, 34) enthält, wobei entweder auf der mittleren
oder auf der unteren Leiterschicht (32, 34) leitende Pfade vorgesehen sind und die
andere der mittleren und der unteren Leiterschicht von den anderen Schichten galvanisch
getrennt ist, und daß die Masseleitung (16) mit der galvanisch getrennten Leiterschicht
(32 oder 34) verbunden ist und ein elektrisches Gegengewicht für die durch die Batterie
(24) gebildete Antenne bildet.
2. Schaltungsanordnung nach Anspruch 1, dadurch gekennzeichnet, daß das Anlegen des HF-Signals an den Anschluß der Batterie (24) über eine Antennenerweiterungsspule
(22) erfolgt.
3. Schaltungsanordnung nach Anspruch 1 oder Anspruch 2, dadurch gekennzeichnet, daß das HF-Signal an den Anschluß der Batterie (24) angelegt wird, der mit dem äußeren
Gehäuse der Batterie verbunden ist.
4. Schaltungsanordnung nach Anspruch 1, 2 oder 3, dadurch gekennzeichnet, daß die Leiterschicht (32; 34), die mit der Masseleitung (16) verbunden ist, mit dem
Gehäuse (42) des Elektrizitäts- oder Wasser-Meßgeräts (44) galvanisch verbunden ist.
5. Verwendung der Schaltungsanordnung nach Anspruch 1, 2 oder 3 im Fall eines Elektrizitäts-
oder Wasser-Meßgeräts (44) mit einem metallischen Gehäuse (42), wobei das zu sendende
HF-Signal Daten über Ablesungen, die am Elektrizitäts- oder Wasser-Meßgerät (44) vorgenommen
werden, enthält, dadurch gekennzeichnet, daß die Schaltungsanordnung in einem innen und außen mit Metall beschichteten Kunststoffgehäuse
(36) untergebracht ist, um zwischen der mit Masse verbundenen Leiterschicht (32; 34)
und dem Gehäuse (38) des Elektrizitäts- oder Wasser-Meßgeräts (44) eine kapazitive
Kopplung zu erzeugen.
1. Disposition de circuit pour la transmission d'un signal radiofréquence, comprenant
un circuit (10) de transmission pour la production du signal radiofréquence, une antenne
(24) pour le rayonnement du signal radiofréquence, un circuit (22) d'adaptation d'impédance
disposé entre l'antenne (24) et la sortie (20) du circuit (10) de transmission et
une batterie (24) pour l'application de la tension de fonctionnement entre une ligne
(12) de tension de fonctionnement positive et une ligne (16) de masse, la ligne (12)
de tension de fonctionnement positive et la ligne (16) de masse étant découplées par
rapport à la batterie (24) du point de vue du signal radiofréquence et le signal radiofréquence
étant appliqué de la sortie (20) du circuit (10) de transmission à une borne de la
batterie (24) de manière que la partie de la batterie (24) connectée à cette borne
constitue l'antenne, caractérisée en ce que le circuit (10) de transmission, le circuit (22) d'adaptation d'impédance et la batterie
(24) sont montés sur une carte (28) de circuits imprimés comportant une couche supérieure,
une couche médiane et une couche inférieure à conducteurs (30, 32, 34), des chemins
conducteurs étant prévus sur l'une desdites couches médiane ou inférieure (32, 34)
à conducteurs, et l'autre desdites couches médiane ou inférieure à conducteurs étant
séparée galvaniquement des autres couches, et en ce que la ligne (16) de masse est connectée à la couche (32 ou 34) à conducteurs séparée
galvaniquement et constitue un contrepoids électrique à l'antenne formée par la batterie
(24).
2. Disposition de circuit selon la revendication 1, caractérisée en ce que l'application du signal radiofréquence à la borne de la batterie (24) est effectuée
par l'intermédiaire d'une bobine (22) d'extension d'antenne.
3. Disposition de circuit selon la revendication 1 ou la revendication 2, caractérisé en ce que le signal radiofréquence est appliqué à la borne de la batterie (24) connectée au
boîtier externe de la batterie.
4. Disposition de circuit selon la revendication 1, 2 ou 3, caractérisée en ce que la couche (32, 34) à conducteurs connectée à la ligne (16) de masse est connectée
galvaniquement au boîtier (42) du compteur (44) d'électricité ou d'eau.
5. Utilisation de la disposition de circuit selon la revendication 1, 2 ou 3 dans le
cas d'un compteur (44) d'eau ou d'électricité comportant un boîtier métallique (42),
le signal radiofréquence devant être transmis contenant des données sur des lectures
prises du compteur (44) d'électricité ou d'eau, caractérisée en ce que la disposition de circuit est logée dans un boîtier (36) en matière plastique métallisé
à l'intérieur et à l'extérieur de manière à produire un couplage capacitif entre la
couche (32, 34) à conducteurs connectée à la masse et le boîtier (38) du compteur
(44) d'électricité ou d'eau.
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