Telecommunications – Receiver or analog modulated signal frequency converter – With wave collector
Reexamination Certificate
2000-04-06
2003-10-21
Maung, Nay (Department: 2684)
Telecommunications
Receiver or analog modulated signal frequency converter
With wave collector
C455S090300, C455S274000, C375S258000, C343S788000
Reexamination Certificate
active
06636728
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a portable receiver of the type comprising several antennas which are connected to a receiver unit for receiving a signal transmitted by electromagnetic induction, said antennas being made in the form of coils which are carried by a support in such a way that the respective turns of said coils are oriented along different respective axes of a reference axis system associated with said support.
2. Description of the Related Art
Portable receivers of the kind indicated above can be used especially in an anti-theft system for motor vehicles. In this case, the signal receiver is usually incorporated into what is called an “identifier”, which is intended to be carried by the owner of the vehicle or by an authorized person and which may furthermore include a signal transmitter placed on the same support as the signal receiver. This support may, for example, be made in the form of a smart card or in the form of a card incorporated into a badge, into the head of the contact key of a motor vehicle or into other articles likely to be carried by the owner of the motor vehicle or by a person authorized to drive the vehicle. Thus, signals may both be received by the identifier from an identification unit, forming part of the anti-theft system and located on board the vehicle, and be transmitted by the identifier to said identification unit.
Under these conditions, when a driver wishes to enter his vehicle, a dialogue between the identification unit and the identifier is established in a known manner. If the identification unit detects the presence of a correct identifier in a known manner, for example by comprising a code transmitted by the identifier with a reference code prerecorded in a memory of the anti-theft system, the identification unit, should the two codes be identical, transmits an authorization signal which can be used to authorize or carry out one or more functions of the motor vehicle, for example to unlock the door locks of the motor vehicle and/or release an engine-immobilizer system.
At the present time, the problem of how to achieve reception homogeneity of the signals by an identifier placed in the magnetic field transmitted by the antenna of the transmitter-receiver of the identification unit located on board the vehicle is well known. In other words, the signal received by the receiver of the identifier should have as large and as constant an amplitude as possible, whatever the position and/or orientation of the identifier in space, corresponding to the working range of the transmitter of said identification unit.
To solve this problem, a first known solution consists in generating what is called a “rotating field” on the transmission side, that is to say within the identification unit located on board the vehicle. For this purpose, an antenna, two coils are used, the axes of revolution of and the currents flowing through said coils are offset by 90°. This is relatively easy to achieve if the modulation used for transmitting the digital data is of the OOK type (on-off modulation). However, if the modulation is of the PSK type (frequency shift modulation) or FSK type (phase shift modulation), the phase between the two currents flowing through the respective coils must be kept constant. This means that almost identical RLC circuits have to be used so that, during the transitions (changes in value of the data), the phases remain coherent. This is difficult to achieve, particularly in high-volume mass production.
It is also possible to produce a “rotating field” on the reception side, that is to say within the receiver of the identifier, by making the latter, for example, as shown schematically in
FIG. 1
of the appended drawings.
FIG. 1
shows an identifier
1
made, for example, in the form of a card
2
(the support) which may have the dimensions of a smart card and which carries two antennas
3
and
4
, a receiver unit
5
and, optionally, a transmitter unit
6
which may also be provided on the card
2
. Each of the two antennas
3
and
4
is made in the form of a coil L
1
and L
2
, which coil is preferably wound on a core
7
or
8
, preferably made of ferrite, and is electrically connected to the receiver unit
5
and, where appropriate, to the transmitter unit
6
if one has been provided. The turns of the two coils L
1
and L
2
, or more precisely the normals to the surfaces of the turns of the two coils L
1
and L
2
, are oriented along the axes
9
and
11
, respectively, these being perpendicular to each other and lying in the plane of the card
2
. The two antennas
3
and
4
may be antennas tuned to the frequency of the signal to be received. In this case, capacitors C
1
and C
2
are connected in parallel to the coils L
1
and L
2
, respectively, in order to form, with the latter, parallel resonant RLC circuits, R being the resistance of the coil L
1
or L
2
, L being its inductance and C being the capacitance of the capacitor C
1
or C
2
.
Under these conditions, when the card
2
is in a magnetic field H which varies with time, for example an alternating magnetic field produced by the antenna of the transmitter-receiver of the identification unit located on board a motor vehicle, the two RLC circuits of the card
2
described above constitute two channels for receiving the carrier wave of the signal transmitted by said identification unit and for sending it to the receiver unit
5
of the card
2
. The problem in this case is the electronic processing of the two channels. The voltages or electromotive forces induced in the two coils L
1
and L
2
may, in certain positions of the card
2
with respect to the direction
12
of the magnetic field H, be in phase or in phase opposition. It is therefore not possible to make a direct summation of the two voltages by putting the two RLC circuits in series, since there are cases in which the resultant voltage would be zero.
This is because, assuming that the card
2
lies in the Ox-Oy plane of an orthonormal fixed coordinate system Ox, Oy, Oz, that the direction
12
of the magnetic field H is parallel to the Ox axis of said orthonormal coordinate system and that the induction B is given by the formula:
B=B
0
sin &ohgr;
t
(1)
in which B
0
is a constant that depends on the intensity of the magnetic field H and on the permeability &mgr; of the medium, in particular the permeability of the core
7
or
8
, and &ohgr; is the angular frequency of the carrier wave of the signal transmitted by the identification unit, the magnetic flux &phgr;
1
which passes through the coil L
1
is, as is well known, given by the formula:
&phgr;
1
=B
0
S
1
cos &agr; sin &ohgr;
t
(2)
in which S
1
is the area of the turns of the coil L
1
and &agr; is the angle that the axis
9
of the coil L
1
makes with the direction
12
of the field H (
FIG. 1
shows one particular position of the card
2
in which the angle &agr; here is equal to &pgr;/2). It is also known that the electromotive force e
1
induced in the coil L
1
is given by the formula:
e
1
=
d
1
dt
=
B
0
S
1
ω
cos
α
cos
ω
t
(
3
)
Likewise, the electromotive force e
2
induced in the coil L
2
, the axis
11
of which makes an angle of &pgr;/2 with respect to the axis
9
of the coil L
1
, is given by the following two formulae:
e
2
=
d
2
dt
=
B
0
S
2
ω
cos
(
π
2
-
α
)
cos
ω
t
(
4
)
e
2
=B
0
S
2
&ohgr; sin &agr; cos &ohgr;
t
(5)
Assuming that the two areas S
1
and S
2
are equal and writing
B
0
S
1
&ohgr;=B
0
S
2
&ohgr;=K
(6)
we then obtain the following formulae for e
1
and e
2
:
e
1
=K
cos &agr; cos &ohgr;
t
(7)
e
1
=K
sin &agr; cos &ohgr;
t
(8)
from which it follows that
e
1
−e
2
=K
(cos &agr;−si
Lele Tanmay
Liniak Berenato & White
Maung Nay
Valeo Securite Habitacle
LandOfFree
Portable multi-antenna signal receiver does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Portable multi-antenna signal receiver, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Portable multi-antenna signal receiver will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3158609