[0001] The present invention relates to a device for detection and onward transmission of
a remotely transmitted signal. More particularly the present invention relates to
a device for signal detection and transmission with reduced anisotropy.
[0002] Signal receivers such as inductive pick-up coils have an anisotropic reception characteristic
and null conditions exist in any communication system in which the spatial orientation
of the coil cannot be predetermined.
[0003] Schemes have been produced to reduce the anisotropic properties in communications
systems. Many such arrangements have relied on mechanical switching networks, but
these have the disadvantage of using moving parts.
[0004] It is an object of the present invention to eliminate null relationships of the type
discussed, allowing a remote signal detection device to be used in any orientation
to the signal source.
[0005] The null relationships of the transmitter and receiving means may be reduced by using
three or more signal detection means (such as coils) in combination, however, even
in such cases the incidence of null orientations is not eliminated.
[0006] We have now found that the null orientations of the signal receiver may be eliminated
using three or more signal detection means and in combination therewith means for
determining and summing the absolute value of the signals produced by said coils.
[0007] Accordingly we provide an antenna device for the receipt and onward transmission
of an electromagnetically transmitted signal, said device comprising:
at least three signal detection means;
means for determining the absolute value of the output of each signal detection means;
and
means for summing the absolute value of said signal detection means.
[0008] Generally, the signal detection means will be arranged such that the axes of said
signal detecting means are disposed in three dimensions. For example, where there
are three signal detection means it is preferred that the axes of the signal detection
means do not lie in the same plane and that no two axes are parallel.
[0009] It may be preferred in some circumstances to have the axes of said signal detection
means disposed .with maximum separation. A particularly convenient and useful arrangement
consists of three signal detection means arranged so that their.axes are orthogonal.
However other arrangements, such as four signal detection means with axes in tetrahedral
arrangement, may be used.
[0010] The nature of the signal detection means is not narrowly critical, and such components
as coils and Hall effect devices may be used. In general, the nature of the signal
detection means may he selected by those skilled in the art in accordance with the
desired nature and frequency of the signal to be detected Preferred signal detecting
means are inductive pick-up coils.
[0011] Said means for determining the absolute value of a signal received by a signal detection
means include rectifiers. Such rectifiers may include, for example, diode bridges
and full wave rectifiers which may, for example, be constructed using operational
amplifiers.
[0012] Said summing means may provide means for summing signals in one or more stages. The
arrangment of summing stages may be chosen as a matter of convenience in order to
achieve summing of said signals. The summing stages may comprise a means for summing
groups of two or more outputs of the signal detection means.
[0013] It will be known to those skilled in the art that a range of additional components
may be incorporated into the said antenna device as a matter of convenience. For example,
it may be advantageous in some circumstances to use one or more additional components
selected from signal amplification means and signal filtering means. Means for signal
amplification and means for signal filtering may be chosen from a wide range of components
known in the .art in accordance with desired nature and frequency range of the output
signal.
[0014] In one embodiment of the invention there is provided an antenna device as hereinbefore
described which additionally comprises means for amplification of the output of each
signal detection means and means for filtering each amplified signal prior to absolute
value determination.
[0015] The present invention further provides a process of communication using a remote
receiving means which process comprises:
generating an electromagnetic signal;
transmitting and receiving said signal in at least one of at least three signal detection
means; determining the absolute value of each output of said signal detection means;
and
summing the absolute values of the outputs of said signal detection means using a
signal summing means.
[0016] The device of the present invention provides significant advantage over prior art
receiving means by ensuring reliable pick-up and onward transmission of an appropriate
signal in any orientation of the antenna to the incoming signal.
[0017] It will be understood by to those skilled in the art that the device of the present
invention may be used in a wide range of applications. For example the device may
be used as an antenna device in communication systems, security systems and remote
switching or triggering systems.
[0018] The device is of particular use where it is required to receive and onwardly transmit
a signal .when the device is in a random orientation.
[0019] Reliable detection and onward transmission of a signal by a stationary antenna is
particularly critical in the case of remote control firing systems used in blasting.
Such systems have been developed recently to obviate the need to use fixed signal
transmission lines such as wire or explosive fuse cord to initiate firing of ignition
devices in blasting detonators.
[0020] The use of the present invention as a means of receiving and onwardly transmitting
an initiation signal for an explosive device provides increased safety and reliability
in such remote firing systems.
[0021] Remote firing systems generally operate by transmission of an electromagnetic signal
to an antenna at the site of the blasting detonator. Usually the detonator is placed
in places which are difficult to reach and it is difficult to ensure a suitable orientation
for signal transmission to a conventional antenna. Hence a blasting assembly for remote
initiation comprising an antenna device according to the present invention for receipt
and onward transmission of a signal to a blasting detonator has the advantage of allowing
random orientation of the antenna device and detonator while ensuring reliable response
to the appropriate detonation signal.
[0022] Hence in one embodiment there is provided a blasting assembly for remote explosive
initiation comprising an antenna device as hereinbefore described which is in communication
with a detonator.
[0023] In a further embodiment, there is provided a method of firing a detonator which method
comprises generating an electromagnetic signal, receiving and onwardly transmitting
said signal to a detonator by means of an antenna device as hereinbefore described.
[0024] Various examples of devices in accordance with this invention will now be described
with the aid of the accompanying drawings.
[0025] In the accompanying drawings:
Fig 1 is a block diagram of a first example of a device according to the present invention.
Fig 2 is a block diagram of a second example of a device according to the present invention.
Fig 3 is a block diagram of a third example of a device according to the present invention.
Fig 4 is a block diagram of a fourth example of a device according to the present
invention.
Fig 5 is a block diagram of a fifth example of a device according to the present invention.
Fig 6 is a circuit diagram of a specific example according to an embodiment of the
present invention.
[0026] Referring to the diagrams:
"L" is used to designate said signal detection means, "M" is used to designate said
absolute value determining means and "S" is used to designate said summing means.
[0027] In Fig 1 there is shown one embodiment of said antenna device which comprises:
three input coils (Ll,L2,L3) which are arranged in an approximately mutually orthogonal orientation;
amplification means for amplifying the output of each coil (A1,A2,A3);
filtering means for modifying the output of each said coil (F1,F2,F3);
absolute magnitude determining means of the filtered output of each input coil (Ml,M2,M3);
means for summing the absolute values of said coil output (S1).
Fig 2 shows a block diagram in which the coil signal passes through a filter prior
(Fl,F2,F3) prior to amplification and absolute value determination.
Fig 3 shows a block diagram of a device of an embodiment of the present invention
in which the signals are received (L1,L2,L3) and are passed through a filter before (F1,F2,F3) and after (F1',F2',F3') amplification stages (Al,A2,A3).
Fig 4 shows a block diagram of a device of an embodiment of the present invention in
which the amplified signals are summed by a summing means comprising two summing stages
(S1,S2).
Fig 5 shows a block diagram of a device according to the invention in which there are
four signal detecting means (L1,L2,L3,L4).
Fig 6 shows one possible implementation of the embodiment of the invention shown in
Figure 2.
[0028] The receiving coils L
1, L
2 and L
3 consist of approximately 3000 turns of copper wire on soft iron cores, having a resistance
of 240 ohms and an inductance of 150 mH. The component values of the device are as
follows:
[0029] Components C
9, R
28, C
10 , R
29, C
11 and R
30 act in conjunctionn with the inductance of the coils as input filtering networks
denoted F
l, F
2 and F
3 in the preferred block schematic diagram shown in Figure 2. The filtering stages
increase the sensitivity of the coils at the desired transmission frequency. The filtering
stages are followed by operational amplifiers IC
la, IC
lb, IC
2a, IC
2b, IC
3a, IC
3b, and components R
1, R
2, C
1, R
3, R
4, C
2, R
10, R
11, R
15, R
16, C
3, R
17, and R
18. These components act as three independent ac amplifiers which increase the input
signals from coils L
1, L
2 and L
3 to an appropriate level for the full-wave rectification stages. Three full-wave rectififers
denoted M
1, M
2 and M
3 in the block diagram (Fig 2) are constructed from components IC
1c, IC
2c, IC
3c, D
1s D
2, D
3, D
4, D
5, D
6, R5, R7, R12, R
13, R14, R
19, R
20 and R
21. The action of these components is to rectify each half cycle of the input signal
so as to produce an output signal equal to the absolute magnitude of the input signal.
The final stage of the circuit comprises components
C4,
C5, C
6, R
22, R
23, R
24, R
25, and IC
4 is an ac summing amplifier, the output of which could, for example, be connected
to the command decoding circuitry of the remote control device such as a blasting
detonator. Components C
7, C
8, R
26 25 and R
27 produce split supply voltages and a zero voltage level from a single battery B
l.
1. An antenna device for receipt and onward transmission of an electromagnetically
transmitted signal, said device comprising:
at least three signal detection means (Ll,L2,L3,L4);and characterized by having
means (Ml,M2,M3,M4) for determining the absolute value of the output of each signal
detection means; and
means (S1,S2) for summing the absolute value of said signal detection means;
the signal detection means being arranged such that the axes of said signal detection
means are disposed in three dimensions.
2. An antenna device according to claim 1, characterized by having three signal detection
means (Ll,L2,L3) arranged so that their axes are orthogonal.
3. An antenna device according to claim 1, characterized by having four signal detecting
means (L1,L2,L3,L4) with axes in tetrahedral arrangement.
4. An antenna device according to any one of claims 1 to 3 inclusive characterized
in that the signal detection means are selected from coils and Hall effect devices.
5. An antenna device according to any one of claims 1 to 4 inclusive characterized
in that the device additionally comprises at least one component selected from the
group of amplification means (Al,A2,A3) and signal filtering means (Fl,F2,F3).
6. An antenna device according to claim 5 characterized in that the device comprises
means (Al,A2,A3) for amplification of the output of each signal detecting means and
means (Fl,F2,F3) for filtering each amplified signal prior to absolute value determination.
7. A blasting assembly for remote explosive initiation comprising an antenna device
according to any one of claims 1 to 6 inclusive which is connected to a detonator.
8. A process of communication using a remote receiving means which process comprises
generating an electromagnetic signal; transmitting and receiving said signal in at
least one of at least three signal detection means (Ll,L2,L3,L4);characterized in
that the absolute value of each output of said signal detection means is determined
and
the absolute values of the outputs of said signal detection means are summed using
a signal summing means (S1,S2).
9. A method of firing a detonator which method comprises generating an electromagnetic
signal, receiving and onwarding transmitting said signal to a detonator by means of
an antenna device according to any one of claims 1 to 6 inclusive.