Note: Descriptions are shown in the official language in which they were submitted.
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SYSTEM AND METHOD FOR SENSING SIGNAL DISRUPTION
The present invention relates to a system and method for sensing signal
disruption. In
particular is relates to a system and method for sensing disruption to a
signal transmitted
via a guiding medium suitable for carrying electromagnetic surface waves.
Background to the Invention
The applicant's prior published patent application GB2494435 discloses a
communication system which utilises a guiding medium which is suitable for
sustaining
electromagnetic surface waves. The present application presents various
applications and
improvements to the system disclosed in GB2494435.
Summary of the Invention
In a first aspect, the present invention provides a system for sensing
disruption to a signal
propagating along a guiding medium for guiding electromagnetic surface waves,
the
system comprising: a guiding medium for guiding electromagnetic surface waves;
a
transmitter arranged to transmit electromagnetic surface waves along the
guiding
medium; a receiver arranged to receive electromagnetic surface waves
transmitted along
the guiding medium and to measure changes to a signal transmitted via the
guiding
medium in order to sense disruption to said signals based on said measured
changes.
In a second aspect, the present invention provides a method of sensing
disruption to a
signal in a system for sensing disruption to a signal propagating along a
guiding medium
for guiding electromagnetic surface waves, the system comprising: a guiding
medium for
guiding electromagnetic surface waves; a transmitter arranged to transmit
electromagnetic surface waves along the guiding medium; a receiver arranged to
receive
electromagnetic surface waves transmitted along the guiding medium and to
measure
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changes to a signal transmitted via the guiding medium in order to sense
disruption to
said signals based on said measured changes; the method comprising:
transmitting a
signal as an electromagnetic surface wave along the guiding medium; measuring
a
change in a signal transmitted via the guiding medium; sensing disruption to
said signals
based on said measured changes.
Further examples of features of embodiments of the present invention are
recited in the
appended claims.
Brief Description of Embodiments of the Invention
Embodiments of the present invention will now be described, by way of example
only,
and with reference to the accompanying drawings, in which:
Figure 1 shows a system in accordance with a first embodiment of the present
invention;
and
Figure 2 is a flow chart showing a method in accordance with an embodiment of
the
present invention.
Detailed Description of Embodiments of the Invention
A first embodiment of the invention will be described in connection with
Figure 1. Figure
1 shows a system 100 which may be used to sense the movement of objects. The
system
100 includes a guiding medium 101. The guiding medium 101 is a high impedance
channel in which the reactive impedance is higher than the resistive
impedance. Such a
channel is suitable for the propagation of electromagnetic surface waves. In
this
example, the guiding medium includes a dielectric layer 102 and a conductive
layer 103.
This guiding medium is similar to the one described in the applicant's co-
pending patent
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application published under number GB2494435. As will be appreciated, the high
impedance channel may take other forms, as described in GB2494435.
The dielectric layer 102 is a sheet of material having a uniform thickness.
The width and
length of the dielectric layer 102 will vary depending on the specific
application. In this
example, an upper surface 104 of the dielectric layer 102 is the surface over
which
surface waves are transmitted. The conductive layer 103 is also a sheet of
material
having a uniform thickness. The width and length of the conductive layer 103
are
generally the same as those equivalent dimensions of the dielectric layer 102,
but they are
not necessarily the same. The conductive layer 103 is positioned against the
dielectric
layer 102. The dielectric layer 102 and the conductive layer 103 accordingly
form a
dielectric coated conductor.
The upper surface 104 of the dielectric layer 102, and hence the guiding
medium 101,
has a reactive impedance which is greater than its resistive impedance. Such a
surface is
suitable for guiding surface waves. In particular, the reactance and
resistance is such that
the surface is suitable for guiding Zenneck surface waves. The layer of air
formed above
the guiding medium acts as the transmission medium for the surface wave.
The system 100 includes a transmit launcher 105 and a receive collector 106.
The system
100 also includes a transmitter 107 and a receiver 108. The transmitter 107 is
arranged to
transmit a signal to transmit launcher 105. The transmit launcher 105
modulates a carrier
signal which is then launched onto the guiding medium 101. The receive
collector 106
receives the surface waves which have propagated over the guiding medium 101.
The
receive collector 106 has the same construction as the transmit launcher 105.
However, it
operates in reverse, collecting surface waves from the guiding medium 101,
rather than
launching them. The receive collector 106 demodulates the carrier signal and
passes the
received signal to the receiver 108.
_
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The system 100 effectively forms a communications channel in which signals may
be
sent from one point to another, via the guiding medium 101. Accordingly, the
guiding
medium 101 acts as a transmission line. As such, anything which interferes
with the
transmission of signals along the transmission line may be detected by
measuring
changes to the signals which pass along the guiding medium 101, or by
measuring
changes to any reflected signals at the transmit end.
It has been appreciated by the applicant that when items move close to the
guiding
medium 101, the signal power measured at the receiver is reduced. The
insertion loss for
a given object can therefore be measured. The system 100 also includes a power
measurement device 109, which is located at the receiver end. The power
measurement
device 109 measures the signal power at the receiver 106. When an object moves
closer
to the guiding medium 101, the receive power is reduced, and the power
measurement
device 109 calculates a power loss for the movement of the object. The power
measurement device may calculate insertion loss.
There are various applications for this system. For example, it is often the
case that
machinery includes rotating parts. Those parts often move very close to each
other, and
their positions are set with very small tolerances. If a part were to move too
close to
another, such that a touch occurs, the machinery could be damaged or broken. A
guiding
medium may be placed on a surface of a rotating part. The power measurement
device
109 determines the insertion loss due to the position of the parts under
normal operating
conditions. In the event of movement of the parts in use, the power loss will
increase, and
this will be measured by the power measurement device 109. This can then be
used to
raise an alarm.
In an alternative embodiment, the system 100 may also be used to detect damage
to a
surface, including the appearance of gaps or movement in a surface. For
example, a
guiding medium 101 may be placed on a structurally important surface of a
vehicle, such
as an aircraft wing. Any movement, cracks or gaps that appear in the surface
will stretch,
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move or break the guiding medium. Such movement will result in a drop power at
the
receiver 108 which can be picked up by the power measurement device.
In addition to insertion loss, the system may use channel estimation figures,
or return
5 loss. The later may be useful for the surface movement detection example.
Any break in
the guiding medium would result in a reflection from the broken -edge. This
could be
detected at the transmitter end. A common element to these embodiments is the
detection
in changes in the transmission channels link budget to indicate some sort of
disruption to
the surface wave signal.
It should be noted that in an alternative embodiment, the transmit and receive
ends could
be co-located for return loss measurements. Furthermore, the system could be
bidirectional, with transmission in both directions. A grid of bidirectional
guiding
medium transmission lines could be used to pin point objects/damage.
Time-doinain reflectrometry may be used to enhance the aforementioned
techniques.
Time-domain reflectrometry techniques could be extended to operate over two-
dimensional structures.
Figure 2 is a flow-chart showing a method in accordance with an embodiment of
the
present invention. The process begins by transmitting an electromagnetic
surface wave
along the guiding medium (S200). Following this, any changes in the signal
transmitted
along the guiding medium are measured (S201). Finally, disruption to the
signal is sensed
based on the measured signals (S202).
Further modifications and variations of the aforementioned systems and methods
may be
implemented within the scope of the appended claims.
