U.S. patent application number 15/255020 was filed with the patent office on 2018-03-01 for rfid transponder and method for supplying energy thereto.
The applicant listed for this patent is NXP B.V.. Invention is credited to FRANZ AMTMANN, PETER THUERINGER.
Application Number | 20180060713 15/255020 |
Document ID | / |
Family ID | 59655957 |
Filed Date | 2018-03-01 |
United States Patent
Application |
20180060713 |
Kind Code |
A1 |
THUERINGER; PETER ; et
al. |
March 1, 2018 |
RFID TRANSPONDER AND METHOD FOR SUPPLYING ENERGY THERETO
Abstract
A RFID transponder includes an active load modulation unit and
an energy harvesting unit coupled to the active load modulation
unit. The active load modulation unit performs active load
modulation on transmitted signals. The energy harvesting unit
harvests RF energy from the ambient environment, converts the RF
energy to DC energy, stores the DC energy, and supplies the DC
energy to the active load modulation unit.
Inventors: |
THUERINGER; PETER; (Graz,
AU) ; AMTMANN; FRANZ; (Gratkorn, AU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NXP B.V. |
Eindhoven |
|
NL |
|
|
Family ID: |
59655957 |
Appl. No.: |
15/255020 |
Filed: |
September 1, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G06K 19/07773 20130101;
G06K 19/071 20130101; G06K 7/0008 20130101; H04B 5/0037 20130101;
H04B 5/0031 20130101; G06K 19/0723 20130101 |
International
Class: |
G06K 19/07 20060101
G06K019/07; G06K 19/077 20060101 G06K019/077 |
Claims
1. A RFID transponder, comprising: an active load modulation unit
that performs an active load modulation on transmitted signals,
wherein said active load modulation unit includes a clock recovery
circuit that recovers a clock received at an antenna from a
magnetic field generated by a reader; an energy harvesting unit
coupled to the active load modulation unit that harvests RF energy
from an ambient environment, converts the RF energy into DC energy,
stores the DC energy, and supplies the DC energy to the active load
modulation unit; and a passive load modulation unit that performs
passive load modulation of the field generated by the reader,
wherein the energy harvesting unit comprises a RF to DC converter
and an energy storage unit, wherein: the RF to DC converter
converts the RF energy into the DC energy and stores the DC energy
in the energy storage unit; the energy storage unit supplies the DC
energy to the active load modulation unit and to one or more other
components of the RFID transponder based on a preset energy supply
rule.
2. (canceled)
3. (canceled)
4. (canceled)
5. The RFID transponder of claim 1, wherein, according to the
preset energy supply rule, (i) the active load modulation unit and
the one or more other components are charged in parallel, or (ii) a
priority order is used for the energy storage unit to supply the DC
energy to the active load modulation unit and the one or more other
components.
6. The RFID transponder of claim 1, wherein the energy storage unit
comprises a plurality of energy storage elements that supply the DC
energy to the active load modulation unit and the one or more other
components separately.
7. The RFID transponder of claim 6, wherein the RF to DC converter
stores the DC energy in the plurality of energy storage elements
based on a preset energy storage rule.
8. The RFID transponder of claim 7, wherein the preset energy
storage rule defines (i) that the RF to DC converter stores the DC
energy in the plurality of energy storage elements in parallel, or
(ii) a priority order for the RF to DC converter to store the DC
energy in the plurality of energy storage elements.
9. (canceled)
10. The RFID transponder of claim 1, further comprising an energy
detection unit that detects if the RF energy exceeds a
predetermined threshold, and (i) if the RF energy exceeds the
predetermined threshold, then the passive load modulation unit
performs the passive load modulation, and (ii) if the RF energy is
equal to or less than the predetermined threshold, then the active
modulation unit performs the active load modulation.
11. The RFID transponder of claim 1, further comprising: an antenna
coupled to active load modulation unit for transmitting the
signals, wherein if a size of the antenna is larger than a
predetermined size, then the passive load modulation unit performs
the passive load modulation, and if the size of the antenna is
equal to or less than the predetermined size, then the active load
modulation unit performs the active load modulation.
12. The RFID transponder of claim 11, further comprising an antenna
coupling unit coupled between the antenna and the active load
modulation unit, wherein the antenna coupling unit performs
impendence and phase matching, and tuning, and wherein: when the
RFID transponder operates in a reception phase, the antenna
coupling unit works with the antenna in a parallel resonance mode;
and when the RFID transponder operates in an active transmission
phase, the antenna coupling unit works with the antenna in a serial
resonance mode.
13. The RFID transponder of claim 12, wherein the antenna coupling
unit includes a transmission terminal, a reception terminal, a
switch, and first and second capacitors, and wherein: when the RFID
transponder is in the reception phase, the switch is closed such
that the first capacitor, the second capacitor, and the antenna are
connected in parallel, and when the RFID transponder is in the
active transmission phase, the switch is open such that the second
capacitor and the antenna are connected in parallel, and the first
capacitor is connected in series with the second capacitor and the
antenna.
14. The RFID transponder of claim 1, wherein the energy harvesting
unit harvests the RF energy from an H-field received from a
reader.
15. A method for supplying energy to a RFID transponder having an
active load modulation unit that performs active load modulation on
transmitted signals, a passive load modulation unit that performs
passive load modulation of a field generated by a reader, and an
antenna coupled to the active and passive load modulation units,
the method comprising the steps of: harvesting RF energy from an
ambient environment; converting the RF energy to DC energy; storing
the DC energy; supplying the DC energy to the active load
modulation unit and one or more additional components of the RFID
transponder based on a preset energy supply rule, wherein the
preset energy supply rule defines that (i) the active load
modulation unit and the one or more additional components are
charged in parallel, or (ii) a priority order is used to supply the
DC energy to the active load modulation unit and the one or more
additional components; and performing the passive load modulation
if a size of the antenna is larger than a predetermined size; and
performing the active load modulation if the size of the antenna is
equal to or less than the predetermined size.
16. (canceled)
17. (canceled)
18. (canceled)
19. The method of claim 15, further comprising: detecting if the RF
energy exceeds a predetermined threshold; performing the passive
load modulation if the RF energy exceeds the predetermined
threshold; and performing the active load modulation if the RF
energy is equal to or less than the predetermined threshold.
20. (canceled)
Description
BACKGROUND
[0001] The present invention is directed to a RFID transponder and,
more particularly, to a RFID transponder having an active load
modulation unit and a method for supplying energy to the RFID
transponder.
[0002] The ISO/IEC 14443 contactless smartcard infrastructure is
optimized for relatively large antenna sizes (ISO-card ID1).
However, more and more devices, like wearable devices, require
smaller antenna geometries, which results in a much lower coupling
coefficient to the reader antenna as compared when smartcard sized
antennas are used. This lower coupling coefficient limits the power
transmitted to small transponders, and more importantly, also
limits the strength of return link signals from the transponders to
a reader.
[0003] Conventionally, the return link signals of a passive
transponder are generated by loading the magnetic field of the
reader (load modulation, also called passive load modulation). This
passive load modulation may be realized with a resistor/resistors
or a capacitor/capacitors switched by the data signal loading the
magnetic field. It also may be realized with a transistor acting as
a resistor. However, if the signal received by the reader is below
the reader's sensitivity, the transponder cannot be detected, read
or written to by the reader.
[0004] To overcome this weak signal issue, "active load modulation"
is used, such that instead of changing the chip input impedance by
switching a resistor or a capacitor, the transponder actively
transmits a signal back to the reader. This active transmission has
to be frequency and phase synchronous to the reader carrier signal,
only in this case the return signal looks like a load modulated
signal to the reader, which is very important so that existing
infrastructure can be used.
[0005] Since transponders using active load modulation consume more
power than those using passive load modulation, the transponders
need sufficient energy to perform the active load modulation.
However, passive transponders using small antennas can't supply
sufficient energy for active load modulation. Thus, a battery is
used to store the energy needed to perform for active load
modulation. However, embedding a battery in a transponder increases
the size of the transponder, which defeats the ability to reduce
the size of the transponder, especially for wearable, small form
factor transponders. Further, for semi-passive transponders that
have an assisted battery but do not use the battery to supply
energy for active load modulation, using the battery to supply
energy for active load modulation would require a bigger battery,
thus increasing the size and cost of the transponders.
[0006] Accordingly, it is desired to have an energy supply solution
for small form factor passive or semi-passive transponders.
SUMMARY
[0007] A RFID transponder and method for supplying energy to a RFID
transponder are described herein.
[0008] A RFID transponder comprises an active load modulation unit
and an energy harvesting unit coupled to the active load modulation
unit. The active load modulation unit performs active load
modulation for transmitting signals. The energy harvesting unit
harvests RF energy from the ambient environment, converts the RF
energy to DC energy, stores the DC energy, and supplies the DC
energy to the active load modulation unit.
[0009] A method for supplying energy to the RFID transponder that
includes an active load modulation unit comprises harvesting RF
energy from the ambient environment, converting the RF energy to DC
energy, storing the DC energy, and supplying the DC energy to the
active load modulation unit.
[0010] The above features, and other features and advantages will
be readily apparent from the following detailed description when
taken in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The present invention is illustrated by way of example and
is not limited by embodiments thereof shown in the accompanying
figures, in which like references indicate similar elements.
Elements in the figures are illustrated for simplicity and clarity
and have not necessarily been drawn to scale.
[0012] FIG. 1 is a schematic block diagram of a RFID transponder in
accordance with an exemplary embodiment;
[0013] FIG. 2 is a schematic block diagram of active load
modulation unit of the RFID transponder of FIG. 1 in accordance
with an exemplary embodiment;
[0014] FIG. 3A is a schematic block diagram of an energy harvesting
unit of the RFID transponder of FIG. 1 in accordance with an
exemplary embodiment;
[0015] FIG. 3B is a schematic block diagram of an energy harvesting
unit of the RFID transponder of FIG. 1 in accordance with another
exemplary embodiment;
[0016] FIG. 4 is a schematic block diagram of a RFID transponder in
accordance with another exemplary embodiment;
[0017] FIG. 5 is a schematic block diagram of a passive load
modulation unit of the RFID transponder of FIG. 4 in accordance
with an exemplary embodiment;
[0018] FIG. 6A is a schematic circuit diagram of an antenna
coupling unit and an antenna of the RFID transponders of FIGS. 1
and 4 in according with an exemplary embodiment;
[0019] FIG. 6B is an equivalent circuit diagram of the antenna
coupling unit and the antenna shown in FIG. 6A during a reception
phase;
[0020] FIG. 6C is an equivalent circuit diagram of the antenna
coupling unit and the antenna shown in FIG. 6A during an active
transmission phase; and
[0021] FIG. 7 is a flow chart of a method for supplying energy to a
RFID transponder in accordance with an exemplary embodiment.
DETAILED DESCRIPTION
[0022] FIG. 1 is a schematic block diagram of a RFID transponder
100 in accordance with an exemplary embodiment of the present
invention. The RFID transponder 100 includes an antenna 102, an
antenna coupling unit 104, an active load modulation unit 106, an
energy harvesting unit 108, a demodulator 110 and a controller
112.
[0023] The RFID transponder 100 uses the antenna 102 to receive
magnetic field and signals from an external device (e.g., a reader)
and transmit signals to the external device. Antennas that receive
and transmit signals from/to readers are known in the art and thus
further description is not necessary for a complete understanding
of the present invention. Antennas for Near Field Communications
that can transmit and receive signals are generally known, such as
from U.S. Pat. No. 9,331,378 of Merlin et al., and assigned to NXP
BV, the contents of which is herein incorporated by reference.
[0024] The antenna coupling unit 104 is connected to the antenna
102 and implements impendence and phase matching and tuning. The
circuitry for performing impedance and phase matching will be
described in more detail with relation to FIG. 6.
[0025] The active load modulation unit 106 is connected to the
antenna coupling unit 104 and the controller 112. The active load
modulation unit 106 performs active load modulation to actively
transmit signals to an external device.
[0026] The energy harvesting unit 108 is connected to the antenna
coupling unit 104 and harvests RF energy from the ambient
environment. In one embodiment, the energy harvesting unit 108
harvests RF energy from magnetic fields, especially from H-field
generated by the external device/reader and received by the antenna
102. The energy harvesting unit 108 converts the RF energy to DC
energy, and stores the DC energy.
[0027] The energy harvesting unit 108 is also connected to the
active load modulation unit 106 and supplies the DC energy to the
active load modulation unit 106. The energy harvesting unit 108
also may be coupled to one or more other components of the RFID
transponder 100 and supply the DC energy to such components as
necessary.
[0028] The demodulator 110 demodulates a modulated RF input signal
received from an external device and provides the demodulated
signal to the controller 112 for further processing. Such
demodulators are generally known in the art and further description
of this circuitry is not necessary for one of skill in the art to
understand the invention.
[0029] The controller 112 can be a microcontroller or a state
machine. The controller 112 ensures that the transmit voltage in
the case of active load modulation is not harvested and that the
demodulator 110 does not lock to its own transmission signal during
active load modulation. The controller 112 also controls the
signaling (i.e., the demodulator 110), as well as other parts of an
RFID system, as will be understood by those of skill in the
art.
[0030] FIG. 2 is a schematic block diagram of the active load
modulation unit 106 of FIG. 1 in accordance with an exemplary
embodiment of the present invention. As previously discussed, the
active load modulation unit 106 is connected between the antenna
coupling unit 104 and the controller 112. The active load
modulation unit 106 includes a clock recovery circuit 118, a
Phase-Locked Loop (PLL) 120, a Digital to Analog Converter (DAC)
122 and a driver 124.
[0031] The clock recovery circuit 118 recovers a clock received at
the antenna 102 from a magnetic field. The PLL 120 receives the
recovered clock signal from the clock recovery circuit 118 and
generates a PLL signal that is provided to the DAC 122. The PLL 120
also receives a control signal from the controller 112 when the
RFID transponder 100 is operating in an active transmission phase.
The control signal indicates a reference clock. The DAC 122
converts a digital transmission signal received from the controller
to an analog signal using the PLL signal. The DAC 112 is connected
to the driver 124, which receives the analog signal generated by
the DAC 112 and provides the analog signal to the antenna coupling
unit 104. The DAC 112 is an optional component of the active load
modulation unit 106, and the driver 124 can be directly controlled
by the controller 112. If the DAC 112 is not included, then the
driver 124 provides a transmission signal generated by the PLL 120
in accordance with a transmission control signal generated by the
controller 112 to the antenna coupling unit 104. The active load
modulation unit 106 performs active load modulation to actively
transmit signals back to the external device. The above-description
is simplified so as not to obscure the present invention. Active
load modulation circuitry is known, such as from U.S. Pat. No.
9,401,739 of Pieber et al. and assigned to NXP BV, the content of
which is incorporated by reference.
[0032] FIG. 3A is a schematic block diagram of the energy
harvesting unit 108 of the RFID transponder of FIG. 1 in accordance
with an exemplary embodiment of the present invention. The energy
harvesting unit 108 includes a RF to DC converter 126 and an energy
storage unit 128. The RF to DC converter 126 converts the received
RF energy into DC energy and stores the DC energy in the energy
storage unit 128. In one embodiment, the RF to DC converter 126
comprises a voltage multiplier including one or more capacitors and
one or more diodes connected between the antenna coupling unit 104
and the energy storage unit 128. However, other circuit
arrangements for RF to DC converters, such as a rectifier or a
charge pump, are known by those of skill in the art and the present
invention is not limited to any one specific implementation. The
energy storage unit 128 supplies the stored DC energy to the active
load modulation unit 106.
[0033] The energy harvesting unit 108 preferably also includes a
switch 130. When the RFID transponder 100 performs active load
modulation, the switch 130, as controlled by the controller 112, is
open (off) so there is not a connection between the RF to DC
converter 126 and the energy storage unit 128 to prevent energy
from going back into the RF to DC converter 126.
[0034] The energy storage unit 128 may also supply the stored DC
energy to one or more other components of the RFID transponder 100
as required. Further, the energy storage unit 128 supplies the DC
energy to the active load modulation unit 106 and the one or more
other components based on a preset energy supply rule.
[0035] The preset energy supply rule defines when and how the
active load modulation unit 106 and the one or more other
components are charged by the energy storage unit 128. For example,
the active load modulation unit 106 and the one or more other units
may be charged in parallel. In another embodiment, the preset
energy supply rule defines a priority order for the energy storage
unit 128 to supply the DC energy to the active load modulation unit
106 and the one or more other components.
[0036] In one embodiment, the preset energy supply rule defines
that the energy storage unit 128 supplies the DC energy to the
active load modulation unit 106 after the energy storage unit 128
supplies a certain amount of the DC energy to one or more other
components. The one or more other components may be components that
are essential for internal processing by the RFID transponder 100,
and the above-mentioned certain amount of energy may be a minimum
amount of the DC energy that these essential components need to
operate.
[0037] In another embodiment, the preset energy supply rule defines
that the energy storage unit 128 supplies the DC energy to the
active load modulation unit 106 before the energy storage unit 128
supplies the DC energy to one or more other components, so that
sufficient energy can be supplied to the active load modulation
unit 106 for performing active mode modulation.
[0038] In FIG. 3A, the energy storage unit 128 includes one energy
storage element 129, which is used for supplying the DC energy to
the active load modulation unit 106 and the one or more other
components of the RFID transponder 100. In other embodiments, the
energy storage unit 128 may include a plurality of energy storage
elements that supply the DC energy to the active load modulation
unit 106 and the one or more other components separately. In one
embodiment, the energy storage unit 128 comprises one or more
capacitors having first terminals connected to a node between the
RF to DC converter 126 and the active load modulation unit 106 and
second terminals connected to ground. The capacitors are sized such
that they fit within the RFID transponder 100 and store sufficient
energy to operate the active load modulation unit 106. However, in
one embodiment, the energy storage unit comprises off-chip
capacitors on the order of a few microfarads.
[0039] As shown in FIG. 3B, in one embodiment, the energy storage
unit 128 includes first and second energy storage elements 129a and
129b. The first energy storage element 129a is used for supplying
DC energy to the active load modulation unit 106, and the second
energy storage element 129b is used for supplying DC energy to one
or more other components.
[0040] The RF to DC converter 126 stores DC energy in the energy
storage elements 129a and 129b based on a preset energy storage
rule. The preset energy storage rule may define that the RF to DC
converter 126 stores the DC energy in the energy storage elements
129a, 129b in parallel, or the preset energy store rule may define
a priority order for the RF to DC converter 126 to store the DC
energy in the energy storage elements 129a, 129b.
[0041] Also as shown in FIG. 3B, the energy harvesting unit 108
further includes a first switch 130 and a second switch 132. The
first switch 130 is coupled between the RF to DC converter 126 and
the first energy storage element 129a, and the second switch 132 is
coupled between the RF to DC converter 126 and the second energy
storage element 129b. The first and second switches 130 and 132
control connection and disconnection between the RF to DC converter
26 and the first energy storage element 129a and the second energy
storage element 129b respectively.
[0042] In the embodiment shown, the first energy storage element
129a is dedicated to supplying energy to the active load modulation
unit 106, which ensures sufficient energy is stored for the active
load modulation unit 106, while the second energy storage element
129b is dedicated to supplying energy to one or more other
components, which can reduce the risk that other components of the
RFID transponder 100 do not have sufficient energy to function
correctly.
[0043] FIG. 4 is a schematic block diagram of a RFID transponder
200 in accordance with another exemplary embodiment of the present
invention. The difference between the RFID transponder 100 and the
RFID transponder 200 is that the RFID transponder 200 includes both
an active load modulation unit 106 and a passive load modulation
unit 214. The passive load modulation unit 214 performs a passive
load modulation of the external device reader's field.
[0044] The RFID transponder 200 also may include an energy
detection unit 216 that detects if the RF energy exceeds a
predetermined threshold. If the energy detection unit 216
determines that the RF energy exceeds the predetermined threshold,
the RFID transponder 200 uses the passive load modulation unit 214
to perform passive load modulation; and if the energy detection
unit determines that the RF energy is equal to or less than the
predetermined threshold, the RFID transponder 200 uses the active
modulation unit 106 to perform active load modulation.
[0045] In one embodiment, the RFID transponder 200 may perform
passive or active load modulation based on a size of the antenna
102. For example, if the antenna 102 is larger than a predetermined
size, the passive load modulation unit 214 is used to perform
passive load modulation, and if the antenna 102 is equal to or less
than a predetermined size, the active load modulation unit 106 is
used to perform the active load modulation. The determination
result of performing the passive load modulation or the active load
modulation may be stored in a memory, look-up table, or control
register of the RFID transponder 200.
[0046] When the RFID transponder 200 performs passive load
modulation, the energy storage unit 128 supplies DC energy to the
passive load modulation unit 124 during energy gaps (modulation
times in both directions) and to smooth current spikes.
[0047] FIG. 6A is a schematic circuit diagram of the antenna
coupling unit 104 and the antenna 102 shown in FIGS. 1 and 4 in
accordance with an exemplary embodiment of the present invention,
while FIG. 6B is an equivalent circuit diagram of the antenna
coupling unit 104 and the antenna 102 during a reception phase, and
FIG. 6C is an equivalent circuit diagram of the antenna coupling
unit 104 and the antenna 102 during an active transmission phase.
When the RFID transponder 100 or 200 operates in a reception phase,
the antenna coupling unit 104 works with the antenna 102 in a
parallel resonance mode. When the RFID transponder 100 or 200
operates in an active transmission phase, the antenna coupling unit
104 works with the antenna 102 in a serial resonance mode. In
practice, the antenna coupling unit 104 may work with the antenna
102 in a substantive parallel resonance mode or a substantive
serial resonance mode that is near to the parallel resonance mode
and serial resonance mode respectively due to mistuning/intended
mistuning, parasitics or other reasons.
[0048] In FIG. 6A, the antenna coupling unit 104 includes a
transmission terminal TX, a reception terminal RX, a switch S1, a
first capacitor C1, and a second capacitor C2, and the antenna 102
includes a inductor L1.
[0049] As shown in FIG. 6B, when the RFID transponder 100 operates
in a reception phase, the switch S1 is closed so the first
capacitor C1, the second capacitor C2 and the inductor L1 are
connected in parallel.
[0050] As shown in FIG. 6C, when the RFID transponder operates in
an active transmission phase, the switch S1 is open so the second
capacitor C2 and the inductor L1 are connected in parallel and the
first capacitor C1 is connected in series with both of the second
capacitor C2 and the inductor L1.
[0051] When the RFID transponder operates in a passive load
modulation phase, the antenna coupling unit 104 works in a parallel
resonance mode as shown in FIG. 6B.
[0052] Another switch (not shown) may be coupled directly to the
reception terminal and used to protect the reception terminal from
high voltages on the antenna during transmission, and an EMC filter
(Electromagnetic Compatibility Filter, also not shown) may be
coupled to the transmission terminal and used to filter the higher
harmonics.
[0053] The RFID transponder 100 or 200 may be a passive RFID
transponder or a semi-passive RFID transponder.
[0054] The active load modulation unit 106 may regulate a
transmission power based on the DC energy obtained from the energy
harvesting unit 108. For example, if the energy harvesting unit 108
does not supply enough energy for the active load modulation unit
106 to operate with full power, the active load modulation unit 106
regulates a transmission power to a lower transmission power based
on the DC energy obtained from the energy harvesting unit 108. This
can be realized by reducing an output voltage of the DAC 122 or
reducing a supply voltage of the driver 124.
[0055] FIG. 7 is a flow chart of a method for supplying energy to
the RFID transponder 100/200 in accordance with an exemplary
embodiment of the present invention. The method includes harvesting
RF energy from the ambient environment in step 702; converting the
RF energy to DC energy in step 704; storing the DC energy in step
706; and supplying the DC energy to the active load modulation unit
106 and other components of the RFID transponder 100/200 as
required in step 708.
[0056] The method further includes supplying the DC energy to one
or more other components of the RFID transponder. Further, the DC
energy is supplied to the active load modulation unit 106 and the
one or more other components based on the above preset energy
supply rule.
[0057] As for the RFID transponder 200 having both a passive load
modulation unit 214 and an active load modulation unit 106, the
method may include the following steps: detecting if the RF energy
exceeds a predetermined threshold; performing passive load
modulation if the RF energy exceeds the predetermined threshold,
and performing active load modulation if the RF energy is equal to
or less than the predetermined threshold.
[0058] In an alternative embodiment, for the RFID transponder 200
having both a passive load modulation unit and an active load
modulation unit, the method may include the following steps:
performing passive load modulation if the antenna is larger than a
predetermined size; and performing active load modulation if the
antenna is equal to or less than a predetermined size.
[0059] In the foregoing specification, the invention has been
described with reference to specific examples of embodiments of the
invention. It will, however, be evident that various modifications
and changes may be made therein without departing from the broader
spirit and scope of the invention as set forth in the appended
claims.
[0060] In the claims, the words `comprising` and `having` do not
exclude the presence of other elements or steps then those listed
in a claim. The terms "a" or "an," as used herein, are defined as
one or more than one. Also, the use of introductory phrases such as
"at least one" and "one or more" in the claims should not be
construed to imply that the introduction of another claim element
by the indefinite articles "a" or "an" limits any particular claim
containing such introduced claim element to inventions containing
only one such element, even when the same claim includes the
introductory phrases "one or more" or "at least one" and indefinite
articles such as "a" or "an." The same holds true for the use of
definite articles. Unless stated otherwise, terms such as "first"
and "second" are used to arbitrarily distinguish between the
elements such terms describe. Thus, these terms are not necessarily
intended to indicate temporal or other prioritization of such
elements. The fact that certain measures are recited in mutually
different claims does not indicate that a combination of these
measures cannot be used to advantage.
* * * * *