Magnetic induction antenna systems and methods of deploying and using the same

Abstract

A magnetic induction antenna system, adapted to wirelessly transmit and / or receive MI signals through solid material, comprising an antenna cable adapted to wirelessly transmit MI downlink signals and / or wirelessly receive MI uplink signals, wherein the antenna cable forms a MI loop antenna with a selected antenna pattern that corresponds to locations of wireless devices, and the MI loop antenna includes a main conductive loop around the locations, and a conductive sub-loop within, or forming a portion of, the main conductive loop, arranged around a selected sub-set of the locations such that the antenna pattern is enhanced relative to the main conductive loop by the or each conductive sub- loop at the selected sub-set of the locations.

Description

RELATED APPLICATION

[0001] The present application is related to Australian Provisional Patent Application No. 2024900253, filed on 5 February 2024, and entitled “Magnetic induction antenna systems and methods of deploying and using the same”, in the name of Orica International Pte Ltd, the originally filed specification of which is hereby incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present disclosure relates to a magnetic induction (MI) antenna system, particularly an MI antenna system for transmitting and / or receiving MI signals that travel through solid material between the MI antenna system and remote / in-ground / in-earth / buried / down-hole wireless devices: these wireless devices are remote from the MI antenna system, separated by the solid material, and are generally in the solid material, e.g., buried in a mine / quarry or civil engineering structure. The solid material can include rock / stemming / earth, and the MI signals can therefore be referred to as "through the earth" (TTE) signals. When transmitted from the MI antenna system to the wireless devices (in a so-called "downlink"), the MI signals may include a blasting command for at least one remote wireless electronic blasting (WEB) device (which may be a wireless initiation device, e.g., a WEBGEN device from ORICA), and typically a plurality thereof, e g., for starting a detonation process of the WEB device BACKGROUND

[0003] A wireless electronic blasting system (e g , ORICA's WEBGEN system) has been developed to improve safety and reliability of blasting operations Instead of using a wire or cable for transmitting a blasting command to a blast initiation device in the blast area, an existing wireless blasting system wirelessly transmits a blasting command as a magnetic induction (MI) signal to a wireless blast initiation device in the blast area. By eliminating the need for deploying and connecting a wire or cable to a blast initiation device, not only is the safety improved but also is the transmission of the blasting command more reliable and independent of impacts, such as a pressure or force, of the surrounding (including, for example, rocks or soil).

[0004] An existing wireless blasting system may include a signal generator and a wireless initiation device. The signal generator generates and emits a blasting command. The blasting command is transmitted in a form of an MI signal for traveling through a dense medium, such as soil or rocks. Upon receipt of the blasting command, the wireless initiation device starts a detonation process, causing an explosive material to explode. Commercially available wireless initiation devices include WEBGEN wireless initiation devices, which are produced by ORICA.

[0005] For transmitting a blasting command, the existing art offers a number of antenna options with various transmission ranges. A maximum theoretical MI transmission range may be about 850 meters. While this range may be adequate in an underground mining environment, it is a limitation in open cut operations where one blast area could spread as far as 2 kilometres.

[0006] In order to achieve a long range MI signal transmission by an existing MI antenna arrangement (where the antenna comprises of a single circular cable loop, or a multiple of cable loops), the transmission signal strength has to be increased. In theory, this could be achieved by either boosting the power of the transmitter (i.e., increasing the current circulating in the antenna loop) or expanding the antenna loop size. Both approaches, however, are not effective, at least in some applications. Since the MI signal attenuates proportionally to the transmission distance cubed, a two-fold expansion of range would require at least an eight-fold boost in signal power. Attaining such a high-power MI transmitter quickly becomes impractical as the transmission range grows due to the excessively thick gauge antenna cable requirement, extreme current consumption, short operation time, overheating issues, and health hazards. The same goes with expanding the antenna loop size.

[0007] Further, the existing antenna options are not feasible to control the directivity or radiation pattern The antenna radiation patterns of the existing art are almost omnidirectional, where the MI signal is emitted to all directions A large proportion of the transmit power is wasted on unwanted signal radiation, and the transmission range is limited.

[0008] Still further, as the existing wireless blasting system applies antenna options for covering a wide communication range, a process of MI signal survey is required to measure and monitor a MI signal strength near a location where the wireless initiation device is to be deployed. For underground operations or large-scale operations, such a MI signal survey process may require a significant amount of cost and time.

[0009] There is thus a need for a cost-efficient and reliable way of improving the range and / or sensitivity of communication to and from wireless initiation devices arranged in an area, e.g., forblasting.

[0010] WO 2020 / 264193 Al describes a system for assisting blasting. The system includes at least one wireless blasting-related device that is deployable or deployed proximate to or within a portion of physical media intended to be blasted as part of a commercial blasting operation. The blasting-related device includes a device-based magnetic induction (MI) signal receiver with a magnetometer configured for through the earth (TTE) Ml communication, and the blasting-related device includes a device-based Ml signal source with a device-based antenna configured for TTE MI communication The device-based MI signal source is configured to communicate with a vehicle-based MI signal receiver in a blast support vehicle that includes a set of vehicle-based magnetometers.

[0011] US 2018 / 0231361 Al describes a wireless initiation device, comprising: a power source, a processing module, a first housing and an initiation unit. The processing module processes wireless electromagnetic communications signals received by an electromagnetic receiver system associated with the processing module. The wireless electromagnetic communications signals include a wireless electromagnetic communications signal representative of a FIRE command. The processing module is configured to generate an initiation signal upon receipt of the FIRE command. At least one of the power source and the processing module is disposed in the first housing, and the first housing has a first connector. The initiation unit has a second housing within which is disposed an initiation module that is configured to discharge initiation energy sufficient to initiate an explosive charge associated with the device. The initiation module is connected to, or connectable with, the processing module such that initiation module can receive an initiation signal from the processing module. The initiation unit also has a second connector that is configured to mate with the first connector, thereby connecting the first and second housings. The initiation module is configured to execute a sequence upon receipt of the initiation signal, the sequence resulting in discharge of initiation energy from the initiation unit.

[0012] US 9,450,684 B2 describes a system for controlling buried devices by means of a very low frequency (VLF) modulated magnetic field capable of providing through-the-earth (TTE) communications. The system comprises a plurality of VLF transmission loop antennas positioned to cover a desired coverage area and configured to transmit a magneto-inductive signal to a desired operating depth. One or more VLF receivers are configured to receive one or more magneto-inductive signals from the one or more VLF transmission antennas. The VLF receivers are operatively connected to the buried devices, and configured to output a control signal thereto in response to the magneto-inductive signals. The plurality of VLF transmission loop antennas may be square or rectangular antennas positioned in an array to cover the desired coverage area, the VLF transmission loop antennas sized and sufficiently powered to transmit the magneto-inductive signal to the desired operating depth. The scheme of US 9,450,684 B2 relies on time division multiplexing: without this multiplexing, there will be interference and / or signal cancellation on the received MI signal at the buried ends, should all the VLF loop antennas transmit at the same time.

[0013] It is desired to address or ameliorate one or more disadvantages or limitations associated with the prior art, or to at least provide a useful alternative. SUMMARY

[0014] Disclosed herein is a magnetic induction (MI) antenna system (1) adapted to wirelessly transmit and / or receive MI signals, through solid material, respectively to and / or from a plurality of wireless devices in respective accommodation sites (61), the antenna system (1) comprising: an antenna cable (30) adapted to: receive a first electrical signal (SI) to wirelessly transmit MI downlink signals to the wireless devices, and / or wirelessly receive MI uplink signals from the wireless devices to generate an uplink electrical signal (SIA) representing the MI uplink signals, wherein the antenna cable (30) forms a MI loop antenna with a selected antenna pattern that corresponds to locations of the accommodation sites (61), wherein the Ml loop antenna includes: a main conductive loop (LI) around a plurality of the accommodation sites (61), and at least one conductive sub-loop (L2,L3) within, or forming a portion of, the main conductive loop (LI), and arranged around at least one selected sub-set of the accommodation sites (61), such that the antenna pattern is enhanced, relative to the main conductive loop (LI), by the or each conductive sub-loop (L2,L3) at the selected sub-set of the accommodation sites (61).

[0015] The or each sub-loop (L2,L3) may include one or more closed sub-loops (L2) that each loops around one or more of the selected sub-set of the accommodation sites (61).

[0016] A selected one of the one or more closed sub-loops (L2) may completely surround a perimeter of a selected one of the selected sub-set of the accommodation sites (61).

[0017] A selected one of the one or more closed sub-loops (L2) may comprise a full turn or a plurality of full turns adjacent to and surrounding the selected one of the selected sub-set of the accommodation sites (61).

[0018] The selected one of the one or more closed sub-loops (L2) may further comprise a fractional turn adjacent to and surrounding the selected one of the selected sub-set of the accommodation sites (61).

[0019] A selected one of the one or more closed sub-loops (L2) may loop around only a selected one of the selected sub-set of the accommodation sites (61).

[0020] The or each sub-loop (L2,L3) may include one or more open sub-loops (L3) that each loops between ones of the accommodation sites (61).

[0021] A selected one of the one or more open sub-loops (L3) may include a side arranged between one or more of the selected sub-set of the accommodation sites (61) inside the open sub-loop (L3) and one or more of the accommodation sites outside the open sub-loop (L3).

[0022] The one or more open sub-loops (L3) may include a plurality of the open sub-loops (L3) arranged mutually adjacently to form a serpentine shape with the corresponding sub-sets of the accommodation sites (61) being mutually adjacent.

[0023] The at least one sub-loop (L2,L3) may include a plurality of the sub-loops (L2,L3) around a respective plurality of sub-sets of the accommodation sites (61).

[0024] A first sub-loop (L2a,L2d), of the plurality of the sub-loops (L2,L3), may be arranged to provide higher magnetic flux density (MFD) and MI sensitivity than a second sub-loop (L3b,L2f) of the plurality of the sub-loops (L2,L3).

[0025] The or each conductive sub-loop (L2,L3) may be selected to be arranged symmetrically around the or each accommodation site (61) in the respective sub-set of the accommodation sites (61) such that the or each accommodation site (61) is substantially in a middle of current carrying elements of the or each conductive sub-loop (L2,L3) for that accommodation site (61).

[0026] The or each conductive sub-loop (L2,L3) may be selected to have a mutual spacing (dO) between its current conducting elements on opposed sides of the or each accommodation site (61) in the respective sub-set of the accommodation sites (61), wherein the mutual spacing (dO) is based on a determined depth (h) of the respective accommodation site (61) and a predefined relationship between magnetic strength, the depth (h) and the mutual spacing (dO).

[0027] The antenna cable (30) may include two terminals (Tl, T2), the antenna cable (30) and the two terminals (Tl, T2) being arranged to form the main loop (LI) including the at least one sub-loop (L2,L3) between the two terminals (Tl, T2).

[0028] The antenna system (1) may further comprise: an electronic signal transmission arrangement (Ml) adapted to emit and transmit the first electrical signal (SI) to the antenna cable (30); and / or an electronic signal receiving arrangement (1800) adapted to detect and receive the uplink electrical signal (SIA) from the antenna cable (30).

[0029] The signal transmission arrangement (Ml) may comprise a first transformer arrangement (20) adapted to receive and convert a second electrical signal (S2) emitted by a signal generator (10) into the first electrical signal (SI), particularly the transformer arrangement (20) being adapted to step down a voltage of the second electrical signal (S2) and thereby convert the second electrical signal (S2) into the first electrical signal (SI), and / or the signal generator (10) may comprise a current generator (11) and a second transformer arrangement (12), the current generator (11) being adapted to generate a source electrical signal (SO) and the second transformer arrangement (12) being adapted to receive the source electrical signal (SO), step up a voltage of the source electrical signal (SO), and thereby convert the source electrical signal (SO) into the second electrical signal (S2).

[0030] The first transformer arrangement (20) may be connected to a base coil (122) to receive the second electrical signal (S2). The base coil (122) may be adapted to be inductively coupled with a source loop antenna (121) connected to a current generator (11). The current generator (11) may be adapted to generate and transmit a source electrical signal (SO) to the source loop antenna (121). The base coil (122) may be adapted to provide the second electrical signal (S2) induced by the source electrical signal (SO) in the source loop antenna (121). The base coil (122) may be adapted to step up a voltage of the source electrical signal (SO) and thereby convert the source electrical signal (SO) into the second electrical signal (S2).

[0031] An extension cable (40) may be adapted to receive the second electrical signal (S2) from a signal generator (10) and transmit the second electrical signal (S2) to the first transformer arrangement (20), the extension cable (40) being a high voltage rated electrical cable adapted for high power transmission,

[0032] A tuning circuit (70) may be connected between one of two terminals (Tl, T2) of the antenna cable (30) and an output of the first transformer arrangement (20).

[0033] Disclosed herein is a method of deploying a magnetic induction (MI) antenna system (1) in one or more signalling areas (50), the one or more signalling areas (50) each including a plurality of accommodation sites (61), the plurality of accommodation sites (61) being adapted for receiving respective wireless devices, wherein the method comprises: arranging an antenna cable (30) to: receive a first electrical signal (SI) from a signal transmission arrangement (Ml) to generate MI downlink signals, and / or provide an uplink electrical signal (SIA) to an electronic signal receiver arrangement (1800) adapted to receive the uplink electrical signal SIA representing currents induced by MI uplink signals in the antenna cable (30), and arranging the antenna cable (30) to extend from the signal transmission arrangement (Ml) and / or the signal receiver arrangement (1800) into the one or more signalling areas (50) and to serve as an (MI) loop antenna to wirelessly transmit the MI downlink signals to, and / or to wirelessly receive the MI uplinks signals from, the wireless devices, wherein the antenna cable (30) is arranged to form: a main conductive loop (LI) around a plurality of the accommodation sites (61); and at least one conductive sub-loop (L2,L3) within, or forming a portion of, the main conductive loop (LI), and arranged around at least one selected sub-set of the accommodation sites (61), such that the antenna pattern is enhanced, relative to the main conductive loop (LI), by the or each conductive sub-loop (L2,L3) at the selected sub-set of the accommodation sites (61) BRIEF DESCRIPTION OF DRAWINGS

[0034] In the drawings, which are not necessarily drawn to scale, like numerals may reference similar components in different figures. The shapes of elements illustrated in the drawings are not intended to limit the embodiments or the scope of the present disclosure, unless explicitly specified. The drawings illustrate various embodiments of the present disclosure.

[0035] Fig. 1 is a schematic view of a magnetic induction (MI) antenna system according to an embodiment of the present disclosure.

[0036] Fig. 2 is a schematic view of an MI antenna system according to another embodiment of the present disclosure.

[0037] Fig. 3 is a schematic view of a sub-loop according to an embodiment of the present disclosure.

[0038] Fig. 4 is a schematic view of an MI antenna system according to another embodiment of the present disclosure.

[0039] Fig. 5 is a schematic view of an MI antenna system according to another embodiment of the present disclosure.

[0040] Fig. 6 is a schematic view of an MI antenna system including a signal transmission arrangement according to an embodiment of the present disclosure.

[0041] Fig. 7 is a schematic view of an MI antenna system including a signal transmission arrangement according to another embodiment of the present disclosure.

[0042] Fig. 8 is a schematic view of an MI antenna system including a signal transmission arrangement according to another embodiment of the present disclosure.

[0043] Fig. 9 is a schematic view of an MI antenna system including a signal transmission arrangement according to another embodiment of the present disclosure.

[0044] Fig. 10 is a contour plot of magnetic field density strengths (in dBT) at a selected depth below a selected cable fonning a square loop antenna in a near-field numerical simulation.

[0045] Fig. 11 is contour plot of magnetic field density strengths (in dBT) at a selected depth below a selected cable forming a square main loop and a closed sub-loop in a near-field numerical simulation.

[0046] Fig. 12 is contour plot of magnetic field density strengths (in dBT) at a selected depth below a selected cable forming a square main loop and a plurality of open sub-loops in a near-field numerical simulation

[0047] Fig. 13 illustrates a method of deploying the antenna system according to the present disclosure.

[0048] Fig. 14 is a graph of simulated magnetic flux density at a constant depth below a pair of antiparallel conductors spaced 1 metre apart (on the Y axis, in decibel Tesla (dBT)) as a function of distance (in metres) from below one of the pair toward the other of the pair, which each curve representing a different constant depth.

[0049] Figs. 15 to 17 are schematic diagrams of an enclosed current generator and a sealed transformer coil for powering embodiments of the Ml antenna system.

[0050] Fig. 18 is a schematic diagram of an uplink signal receiver arrangement. DETAILED DESCRIPTION Overview

[0051] The present disclosure provides a magnetic induction (MI) antenna system 1 adapted to wirelessly transmit and / or receive MI signals that travel through solid material between the antenna system 1 and one or more remote / in-ground / in-earth / buried / down-hole wireless devices: these wireless devices are remote from the antenna system 1, separated by the solid material, and are generally in the solid material, e.g., buried in a mine / quarry or civil engineering structure. The solid material can include rock / stemming / earth, and the MI signals can therefore be referred to as "through the earth" (TTE) signals. When transmitted from the antenna system 1 to the wireless devices (in a so-called "downlink"), the MI signals may be referred to as "downlink" signals. When transmitted to the antenna system 1 from the wireless devices (in a so-called "uplink"), the MI signals may be referred to as "uplink" signals. The antenna system 1 can be configured to transmit the downlink signals, to receive the uplink signals, or to both receive the uplink signals and to transmit the downlink signals to provide "two-way" wireless communication between the antenna system and the wireless devices. The downlink signals can include (i.e., represent or carry, typically by way of modulation of the MI signals according to a modulation process, and corresponding demodulation of the MI signals according to a corresponding demodulation process) wireless commands for the one or more wireless device. In a blasting operation, the wireless commands can include blasting commands for one or more of the wireless devices in the form of wireless electronic blasting (WEB) devices, e.g., wireless initiation devices configured for wireless electronic blasting, e.g., WEBGEN devices from ORICA, e.g., for starting a detonation process of the WEB device. In some embodiments, the antenna system 1 is able to efficiently receive and / or transmit MI signals, e.g., to transmit a blasting command over a long transmission range, which may be as far as 2 kilometers, to the wireless devices.

[0052] The present disclosure also provides methods of deploying and using the antenna system 1.

[0053] The wireless devices are described as being located in respective accommodation sites 61, in which they remain substantially motionless relative to the antenna system 1 at least during transmission / reception of the Ml signals. The antenna system 1 includes at least one Ml loop antenna arranged (or deployed), typically in an antenna plane, e.g., a horizontal plane of a bench in a mine / quarry, and each accommodation site 61 is located at its corresponding depth, in the solid material, away from MI loop antenna (and thus away, at a selected depth, from the antenna plane). Although referred to as "the antenna plane", this plane need not be completely planar, and may be non-planar, e g., conforming to the surface of a mining / quarry bench or a civil construction site or an underground mining surface. The "antenna plane" may therefore be referred to as a partially non-planar "antenna surface" extending between the current-carrying elements of the MI loop antenna.

[0054] As shown in Fig. 1, the antenna system 1 includes: a cable 30 (referred to as the "antenna cable 30" because it forms at least a portion of the MI loop antenna) adapted to: - (for a downlink) receive an electrical signal SI (e.g., including a wireless command) to wirelessly transmit (e.g., the wireless command) by the downlink signals to the wireless devices in the accommodation sites 61; and / or - (for an uplink) wirelessly receive uplink signals from the wireless devices in the accommodation sites 61 to generate an uplink electrical signal S1A in the cable 30 (e g., including a wireless measurement or acknowl edgement).

[0055] As shown in Fig. 1, the cable 30 forms an MI loop antenna with a selected antenna pattern that corresponds to locations of the ac commodation sites 61 of the wireless devices, wherein the MI loop antenna includes: - a main conductive loop LI around a plurality of the accommodation sites 61 adapted to receive the wireless devices, and - at least one conductive sub-loop L2,L3 within, or forming a portion of, the main conductive loop L I and arranged around a selected sub-set of the accommodation sites 61, such that the antenna pattern is enhanced, relative to the main conductive loop LI, by the or each conductive sub-loop L2,L3 at the selected sub-set of the accommodation sites 61.

[0056] As shown in Fig. 1, the or each sub-loop L2,L3 includes: - one or more closed sub-loops L2 that each loops around (e.g., encircles) one of the selected sub-set of the accommodation sites 61 (thus substantially or completely surrounding a perimeter of a selected one of the selected sub-set of the accommodation sites 61, i.e., substantially or completely surrounding a projection of the corresponding one accommodation site 61 in the antenna plane), and / or - one or more open sub-loops (L3) that each loops between ones of the selected sub-set of the accommodation sites (61) (thus each open sub-loop L3 divides ones of the accommodation sites 61, thus looping between adjacent projections of the accommodation site 61 in the antenna plane).

[0057] The cable 30, by way of the main loop LI and the or each sub-loop L2,L3, forms the "MI loop antenna" because it forms a closed path for the electrical current of the electrical signals SI,SIA, despite the combination of the main loop LI and the sub-loop(s) being geometrically more complicated that a circular, elliptical, square or rectangular loop antenna. The MI loop antenna formed by the main loop LI and the or each sub-loop L2,L3 defines a volume that projects perpendicular to the antenna plane into the solid material adjacent to (e.g., below) the cable 30, in which, by way of the selected antenna pattern: for the downlink signals, the electrical signal SI generates a generally stronger Ml signal (due to the stronger magnetic flux density (MFD)) compared to outside of this volume; and, for the uplink signals, a generally stronger uplink electrical signal SI A is generated compared to from sites outside of this volume. In order for the MFD or Ml sensitivity to be enhanced by the (or each) subloop L2,L3, the main conductive loop L1 and the or each sub-loop L2,L3 are arranged such that the MI signal from the main conductive loop LI and the or each sub-loop interfere constructively to: enhance the MFD of the MI downlink signals, and / or enhance the MI sensitivity to the MI uplink signals.

[0058] The or each sub-loop L2,L3 is formed in series electrically or in parallel electrically with the main loop LI. In downlink implementations, the main loop LI and the sub-loops L2,L3 are driven by the same current source, or coordinated current sources, such that the electrical current (that provides the electrical signal SI) in the current-carrying elements of the main loop LI and the or each sub-loop L2,L3 (in the signalling area 60) have the same electrical current phase and frequency (and the same electrical current magnitude unless the current is divided into a plurality of parallel current-carrying elements). In uplink implementations, the current-carrying elements of the main loop LI and the or each sub-loop L2,L3 detect / receive (by way of induced currents) the uplink signals from the wireless devices, and the uplink signals typically have mutually different phases, frequencies and / or modulations from the respective wireless devices, e.g., the uplink signals may be timedivision multiplexed, frequency-division multiplexed, and / or code-divisional multiplexed so uplink signals from different ones of the wireless devices are distinguishable by demodulation; however, the current-carrying elements of the main loop L I and the or each sub-loop L2,L3 are connected in series and / or in parallel such that all of the current-carrying elements that detect respective portions of a specific uplink signal, from a specific wireless device, operate to collect the portions (by addition) and thus detect / receive / pick up more of the specific uplink signal. Thus the or each sub-loop L2,L3 effectively shortens the distance required for wireless transmission—between the loop antenna and the wireless devices—by bringing the loop antenna, which may be referred to as a "pickup antenna" for the uplink signals, closer to the wireless devices; in other words, the or each sub-loop L2,L3 effectively spreads the loop antenna out across a signalling area 60, around / above the accommodation sites 61, such that the loop antenna can simultaneously reach multiple / all uplink signals (i.e., transmitted from the wireless devices) at short distances. Furthermore, in order for the MFD and sensitivity to be enhanced, a rotational direction of the electrical signals SI,SIA in current-carrying elements of the cable 30 closest to each accommodation site 61 is generally arranged to be consistent for that accommodation site 61, e.g., clockwise or counterclockwise, so that the MI downlink signals from, and / or the induced current from the MI uplink signals from, those current-carrying elements interfere constructively.

[0059] The main loop LI and the or each sub-loop L2,L3 define the antenna plane of the MI loop antenna when in a planar arrangement.

[0060] The at least one sub-loop L2,L3 may include a plurality of the sub-loops L2,L3 around a respective plurality of sub-sets of the accommodation sites 61. As shown in Fig 1, the at least one sub-loop L2,L3 may include a plurality of the sub-loops L2a,L3b,L3c around a respective plurality of sub-sets (site 61a for L2a; sites 61c,61h,61m,61r forL3b; and sites 61d,61i,61n,61s and 61e,61j,61o,61t for L3c) of the accommodation sites 61. As shown in Fig. 2, the at least one sub-loop L2,L3 may include a plurality of the sub-loops L3a,L3d,L3e,L3f,L3g around a respective plurality of sub-sets (sites 61a,61f,61k,61p for L3a; sites 61b,61g,611,61q forL3d; sites 61c,61h,61m,61r for L3e; sites 61d,61i,61n,61s forL3f; and sites 6 le,61j,6 lo,6 It for L3g) of the accommodation sites 61. As shown in Fig. 5, the at least one sub-loop L2,L3 may include a plurality of the sub-loops L2c,L2d,L2f,L3h around a respective plurality of sub-sets, namely sites 61a,61b for L2c, site 61e for L2d, site 61t for L2f, and site 6In for L3h.

[0061] In some implementations, the at least one sub-loop L2,L3 includes: the open subloop L3 with a side thereof arranged between one or more of the selected sub-set of the accommodation sites 61 in the open sub-loop L3 (i.e., with their projections onto the antenna plane falling substantially within the open sub-loop L2) and one or more of the accommodation sites 61 outside the open sub-loop L3; thus the open sub-loop L3 lies between a pair of mutually adjacent ones of the accommodation sites 61 where one of the pair is inside the open sub-loop L3 and the other is outside the open sub-loop L3. As shown in Fig. 1, the or each sub-loop L2,L3 may include an open sub-loop L3b that loops between ones 611,61q,61r,61m,etc. of the accommodation sites 61; specifically, the open sub-loop L3b includes a side 32b arranged between sites 61c,61h,61m,61r, which are one or more of the selected sub-set of the accommodation sites 61 inside the open sub-loop L3b, and sites 61b,61g,611,61q, which are one or more of the accommodation sites 61 that are outside the open sub-loop L3b. As shown in Fig. 2, the or each sub-loop L2,L3 may include: an open subloop L3a that loops between ones of the accommodation sites 61, including a side arranged between sites 61a,61f,61k,61p inside the open sub-loop L3a and sites 61b,61g,611,61q outside the open sub-loop L3a.

[0062] The open sub-loop L3 may form a rectangular-wave pattern around and between the accommodation sites 61, e.g., as shown in Fig. 1, and thus the cable 30 may be described as forming a "serpentine antenna" or "meandering antenna". As shown in Fig. 1, the one or more open sub-loops L3 include a plurality of the open sub-loops L3b,L3c arranged mutually adjacently to form a serpentine shape with the corresponding sub-sets of the accommodation sites (sites 61c,61h,61m,61r and sites 61d,61 i,6In,61 s) being mutually adjacent. As shown in Fig. 2, the one or more open sub-loops L3 include a plurality of the open sub-loops L3a,L3d,L3e,L3f,L3g arranged mutually adjacently to form a serpentine shape with the corresponding sub-sets of the accommodation sites (sites 61a,61f,61k,61p; sites 61b,61g,611,61q; sites 61c,61h,61m,61r; sites 61d,61i,61n,61 s; and sites 61 e,61j,61 o,611) being mutually adjacent.

[0063] The one or more closed sub-loops can be used to enhance the MFD and MI sensitivity at one or more accommodation sites selectively, e.g., if one site had particularly Mi-opaque rock and / or a deep wireless device, that site can have a correspondingly selected larger number of turns of the sub-loop to correspondingly and selectively enhance the MFD. Thus, a first sub-loop (L2a,L2d), of the plurality of the sub-loops (L2,L3), may be arranged to provide higher magnetic flux density (MFD) and MI sensitivity than a second sub-loop (L3a,L2f) of the plurality of the sub-loops (L2,L3). As shown in Fig. 1, the closed sub-loop L2a has more current carrying elements arranged around its site 61a than the open sub-loop L3b has around its set of sites 61c,61h,61m,61r, thus the closed sub-loop L2a has been arranged to provide higher magnetic flux density (MFD) and MI sensitivity to its site 61a than the open sub-loop L3b provides to its sites 61c,61h,61m,61r. As shown in Fig. 5, the closed sub-loop L2d has more current carrying elements arranged around its site 61e than the closed sub-loop L2f has around its site 6 It, thus the closed sub-loop L2d has been arranged to provide higher magnetic flux density (MFD) and MI sensitivity to its site 61e than the closed sub-loop L2f provides to its site 6It.

[0064] In blasting implementations, which include the downlink, the antenna system 1 is adapted to wirelessly transmit a first blasting command through a first Ml signal to a first WEB device for starting a detonation process of the first WEB device. The antenna system 1 includes the cable 30 adapted to receive the electrical signal SI comprising the first blasting command and wirelessly transmit the first blasting command through the first MI signal to the first WEB device

[0065] In the blasting implementations, the cable 30 is adapted to meander at least partially in a winding course relative to a first accommodation site adapted to receive the first WEB device. The cable 30 is adapted to form a first sub-loop L2,L3 in the winding course, the first sub-loop L2,L3 being arranged adjacent to and surrounding an arcuate region of more than 90 degrees relative to the first accommodation site.

[0066] The first cable 30 can be arranged in a signalling area 60 (where MI signals are transmitted to and / or received from the remote wireless devices) and adjacent to the first accommodation site 61, where one of the remote wireless devices can be deployed. It is thus possible to effectively relay and distribute the MI signal to—and / or receive signals from— only desirable subsets of the accommodation sites in the signalling area 60 by the first cable 30. Although the Ml signal transmitted by the first sub-loop L2,L3 tends to be confined locally, it is certain that there will be MI signal where the first sub-loop L2,L3 is. The first cable 30 can be placed close to the signalling area 60, the accommodation site 61 in the signalling area 60, the wireless device, and / or explosive materials in the accommodation sites 61 (in the blasting implementations). This, in effect, minimizes the distance between the first cable 30 and the wireless devices at the accommodation sites 61, which makes the distribution of the MI signal (and the blasting command in the blasting implementations) much easier. Even more notably, this mitigates the need for a large scale MI signal survey as required in the existing art.

[0067] Existing MI loop antennas may have antenna radiation patterns (substantially in the near field) that are substantially omnidirectional, thus: (a) the downlink MI signals are emitted in all or many directions, including in directions where no relevant wireless receiver is located or expected to be located (thus a large proportion of the transmit power is wasted on the unwanted signal radiation directions, and the transmission range is accordingly limited); and (b) the uplink MI signals are detected from all or many directions, including from directions where no relevant wireless transmitter is located or expected to be located (thus substantial noise or interference signals can be undesirably gathered from unnecessary directions in the radiation pattern, and the detection range is accordingly limited). In contrast, the antenna system 1 is able to control the directivity and / or radiation pattern by the arrangement of the or each sub-loop L2,L3 of the first cable 30.

[0068] Further, in the blasting implementations, the antenna system 1 need not compromise any benefits offered by an existing wireless blasting systems or operations. For example, the process of loading an accommodation site with bulk explosive materials and a WEB device can be done similarly to the existing operation, e g., as in ORICA's WEBGEN200 system. The cable 30 can be deployed shortly before the blasting operation.

[0069] The antenna system 1 is thus capable of performing the following, in a costefficient and reliable manner: (a) efficiently transmitting an MI downlink signal (e.g., including a blasting command), over a long transmission range including TTE, to a wireless device (e.g., a WEB device, e.g., a wireless initiation device), and / or (b) efficiently receiving an MI uplink, over a long transmission range including TTE, from a wireless device.

[0070] As will be explained in exemplary embodiments with reference to the figures, the MI antenna system 1 according to the present disclosure provides the technical advantages over the existing art in that the MI antenna system 1 can effectively relay and distribute the MI signal to the selected accommodation sites by the cable 30, even if the cable is of lower current-carrying capacity (e.g., 24 AWG cable, with 0.51mm core diameter, which can handle 3.5 A), and thus less expensive, more environmentally friendly, and / or more disposable. In blasting implementations, the cable 30 can be placed close to or in the signalling area 60, the accommodation sites 61 in the signalling area 60, the WEB device, or explosive materials in the accommodation site 61, which minimizes the distance between the cable 30 and the WEB device or explosive materials at the accommodation site 61 of the signalling area 60, which makes the distribution of the MI signal and the blasting command much easier. Even more notably, this mitigates the need for a large scale MI signal survey as required in the existing art.

[0071] The MI antenna system 1 according to the present disclosure allows for simultaneous distribution of the signal across a wide horizontal plane, without the need of deep rock / through the earth penetration, and this can be critical in blasting implementations, for firing WEB devices (via the downlink), and / or in sensing implementations, for wide-areas sensing (via the uplink). Magnetic Induction (MI) Antenna Loop LI and Sub-loops L2, L3

[0072] Fig. 1 illustrates an MI antenna system 1 according to the present disclosure.

[0073] In blasting implementations, the antenna system 1 is adapted to wireless transmit a blasting command by modulation of a magnetic induction (MI) signal to a wireless electronic blasting (WEB) device at an accommodation site 61, e g., for starting a detonation process of the WEB device (e.g., if it is a WEB device). The WEB device is a device configured to receive a wireless signal including a blasting command and to start a detonation process of a detonating device according to the received blasting command. The detonating device is configured to discharge an energy to trigger explosion of explosive materials when a detonation process is triggered by the WEB device. A detonating device and a WEB device may be integrated or separately formed and are in the existing art. As an example, a detonating device and a WEB device are described in US 2018 / 0231361 Al.

[0074] In blasting implementations, referring to Fig. 1, the antenna system 1 includes the cable 30 adapted to receive the first electrical signal SI, which includes a first blasting command, and to wirelessly transmit the first blasting command through a magnetic induction (MI) signal to the WEB devices located at respective selected depths (e.g., defined in a blasting plan) in the respective accommodation sites 61.

[0075] As shown in Fig. 1, in the implementations disclosed herein, the cable 30 forms a MI loop antenna including: - a main conductive loop L1 around a plurality of the accommodation sites 61 adapted to receive the wireless devices, and - at least one conductive sub-loop L2, L3 within or forming a portion of the main conductive loop LI (and substantially co-planar therewith) and around a selected sub-set of the accommodation sites 61.

[0076] For the downlink, the MI signal at the depths of the wireless devices in the accommodation sites 61 has a (selected) magnetic flux density (MFD) pattern (providing a minimum MFD and / or signal-to-noise ratio for reliable MI downlink signalling to the wireless devices), and the MFD at the depths of the wireless devices in the sub-set of the accommodation sites 61 is enhanced (relative to the main conductive loop LI, and relative to each sub-loop not being formed) by the or each conductive sub-loop L2,L3.

[0077] As shown in Fig. 1, the MI loop antenna is arranged in / on a signalling area 60 in a working area 50 (also referred to as a working site, or—for blasting—a blasting area / site). The signalling area 60, e.g., shown in Fig. 7, includes the accommodation sites 61 and is thus lies above the locations of the wireless devices. As shown in Figs. 1 and 7, the cable 30 extends from its terminals T1,T2 across the working area 50 to the signalling area 60 without forming the MI loop antenna so as to mitigate unnecessary portions of the antenna patterns (and thus transmission of unnecessary magnetic flux and / or collection of unnecessary MI noise) from the cable 30 outside the signalling area 60: accordingly, the cable 30 may be arranged to have a selected spacing between its current carrying conductors (which carry the current II from the terminals T1,T2 as shown in Fig. 1, or current SIA to the terminals T1,T2 as shown in Fig. 18), including to be as close as possible, e.g., substantially adjacent, separated only by cable insulation, including in a pair and / or in a twisted pair of the antiparallel cable portions, because there is no need to radiate MI signals and / or gather MI signals outside of the signalling area 60. Outside of the signalling area 60, the cable pair (i.e., the pair of conductive elements) of the cable 30 should be as closed as possible together, e.g., the cable pair can be twisted pair, because there is no need to radiate MI signal to the area outside of the signalling area 60. Thus, the distance d-max in Fig. 1 may be substantially equal to twice the diameter of the cable 30. In at least some implementations, the antenna system 1 can include two or more signalling areas 60, e.g., two or more groups of blast holes in a big bench, and thus the antenna system 1 can include correspondingly two or more MI loop antennas, extending across the or respective working areas / sites to the respective signalling areas 60 and MI loop antennas therein (each with selected sub-loops as described herein). Each of the MI loop antennas may be electrically connected in parallel to the terminals T1,T2; alternatively or additionally, each of the MI loop antennas (“i”) may have a corresponding antenna system, each with its own circuit, including a secondary coil 22i, a tuning circuit 70i, terminals Tli,T2i, a cable 3Oi and thus a signalling area 60i (in other words, a plurality of the arrangement from the secondary coil 22 to the signalling area 60 in Fig. 7). Each of the plurality of coils 22i is magnetically coupled to a primary coil 21 (e.g., see Fig. 7), and each sends or receives current to or from its own corresponding signalling area 60i—this can be thought of as having a transformer with a primary coil 21 and a plurality of the secondary coils 22, each secondary coil 22i powering its own separate load (the MI loop antenna) or receiving signals from its own separate MI loop antenna (“i”). In these implementations, two of the MI loop antennas can be arranged above and below the solid material (e.g., one above the solid material and the other below the solid material) such that both of the MI loop antennas magnetically couple to wireless devices in the solid material; for example, having multiple of the MI loop antennas may be used in underground blasting with one MI loop antenna placed below the blast ring, and one MI loop antenna placed above the blast ring—then two MI loop antennas can be coupled from the same source (Current Generator 11) such that they have the same phase and frequency, and such that transmissions from the MI loop antennas (or beam patterns thereof, for the uplink signals) interfere constructively where the wireless devices are inside solid material.

[0078] In blasting implementations, the signalling area 60 may be referred to as a portion of the blasting area / site, and includes the area affected by the blast, e.g., such that loop LI and sub-loops L2,L3 in the signalling area 60 are typically destroyed or at least damaged by the blasts of the WEB devices.

[0079] As shown in Fig. 1, the sub-loop includes: - at least one closed sub-loop L2 completely surrounding the corresponding accommodation site, in the plane of the main conductive loop LI, and / or - at least one open sub-loop L3 partially surrounding the corresponding accommodation site, in the plane of the main conductive loop LI.

[0080] As shown in Fig. 1, the closed sub-loop L2a completely surrounds its accommodation site 61a

[0081] As shown in Fig. 1, the open sub-loop L3b partially surrounds, on at least 3 sides, its 4 accommodation sites 61c, 61 h, 61m, 61 r, and the open sub-loop L3b partially surrounds, on at least 3 sides, its 8 accommodation sites 61d, 61e, 61i, 61j, 61n, 61o, 61s, 61t.

[0082] In order for the antenna pattern (and thus the MFD and antenna sensitivity) to be enhanced by the or each sub-loop L2,L3, the main conductive loop LI and the or each subloop L2,L3 are arranged such that the MI signal from the main conductive loop L I and the or each sub-loop L2,L3 interfere substantially constructively to enhance antenna pattern (and thus the MFD and antenna sensitivity) relative to the main conductive loop LI without the sub-loop L2,L3 at the locations of the accommodation sites 61. In order for the antenna pattern to be enhanced, a rotational direction of the electrical signals SI,SIA in elements of the cable 30 closest to each accommodation site 61 is consistent, e g., clockwise or counterclockwise ("anticlockwise), so that the MI downlink signals or induced current (from the MI uplink signals) of the elements interfere constructively.

[0083] As shown in Fig. 1, the electrical signal SI is carried by current II, which travels in an anticlockwise direction around the main conductive loop LI and each of the sub-loops L2,L3. Accordingly, for the downlink, accordingly to the "right-hand rule", the magnetic field from the current II in the closest elements of the cable 30 (not past another element of the cable 30, i,e., the cable elements "seen" by the top of the accommodation site 61 and looping or "sub-looping" around the accommodation site 61) to each accommodation site 61 is out of the page (of Fig. 1) at that accommodation site 61. Equivalently, for the uplink, the current II is generated (according to Faraday's law) in substantially the same direction around the main conductive loop LI and each of the sub-loops L2,L3 that are closest to the accommodation site 61 generating the uplink signal.

[0084] As shown in Fig. 1, the open sub-loop L3 can include a side thereof arranged between the corresponding sub-set of the accommodation sites in the sub-loop L3 and one of the accommodation sites outside the sub-loop: e.g., the sub-loop L3b has two sides 32a,b between accommodation sites 61c, 61h, 61m, 61r in the sub-loop L3b and the other accommodation sites in Fig. 1, e.g., 61d, 61i, 61n, 61s. Along the side 32a,b between the accommodation sites 61, the cable 30 loops back on itself, forming a narrow stroke of a rectangular-wave pattern laying across the working area 50, which is in contrast to the wide stroke of the rectangular-wave pattern formed by the open sub-loop L3. The antenna pattern provided in the narrow stroke formed by the cable 30 is dominated by destructive interference relative to the main conductive loop LI, and the antenna pattern at the depths of interest is generally not enhanced, and generally substantially weaker than the antenna pattern in the sub-loops L3, e.g., as illustrated hereinafter with reference to Fig. 12.

[0085] By way of the open sub-loop L3 forming a rectangular-wave pattern around the accommodation sites (61), the cable (30) may be described as forming a "serpentine antenna" or "meandering antenna".

[0086] As shown in Fig. 1, the cable 30 includes two terminals Tl, T2 to which the signal S1 is applied (for the downlink), or at which the signal S1A is detected (for the uplink).

[0087] As shown in Fig. 1, the closed sub-loop L2 can completely surround a perimeter of a first accommodation site 61a of the sub-set of the accommodation sites 61, and can encircle a top of the first accommodation site 61a multiple times. As shown in Fig. 4, the closed subloop L2b can completely surround a perimeter of a second accommodation site 61b of the sub-set of the accommodation sites 61, and can encircle a top of the second accommodation site 61b multiple times, e.g., at least twice.

[0088] Tn some implementations, a selected one of the one or more closed sub-loops (L2) comprises a full turn or a plurality of full turns adjacent to and surrounding the first accommodation site 61—specifically, surrounding the projection / perimeter of the first accommodation site 61 in the antenna plane. As shown in Fig. 1, the closed sub-loop L2 comprises a full turn or a plurality of full turns adjacent to and surrounding the first accommodation site 61a.

[0089] In some implementations, the selected one of the one or more closed sub-loops L2 further comprises a (or any) fractional turn adjacent to and surrounding the first accommodation site 61—specifically, surrounding the projection / perimeter of the first accommodation site 61 in the antenna plane. The "fractional turn" includes a fraction of a full turn, thus less than 100% of a full turn. As shown in Fig. 1, the closed sub-loop L2a further comprises a fractional turn, in addition to the plurality of full turns, adjacent to and surrounding the first accommodation site 61a, thus surrounding the first accommodation site 61a 2.5 times. By way of the fractional turn in Fig. 1, the cable 30 can loop toward any accommodation site, e.g., site 61b or 61 f, that is adjacent to the first accommodation site. As shown in Fig. 4, the closed sub-loop L2b further comprises a fractional turn, in addition to the plurality of full turns, adjacent to and surrounding the second accommodation site 61b, thus surrounding the second accommodation site 61b 2.25 times.

[0090] As shown in Fig. 5, the at least one sub-loop can include a plurality of the closed sub-loops L2 surrounding respective sub-sets of the accommodation sites 61.

[0091] The multiple closed sub-loops L2 can be used to enhance the antenna pattern at multiple accommodation sites selectively, e g., if one site had particularly Mi-opaque rock and / or a deep wireless device, that site can have a correspondingly selected larger number of turns of the sub-loop to correspondingly and selectively enhance the antenna pattern.

[0092] A selected one of the one or more closed sub-loops L2 might surround or loop around only one accommodation site, i.e., a sub-set of 1 of the accommodation sites 61. As shown in Fig. 1, in some implementations, the closed sub-loop L2a may surround only site 61a of the accommodation sites 61 (where "surrounding" means surrounding a protection of the accommodation site 61 in the antenna plane). As shown in Fig. 4, the closed sub-loop L2b may surround only site 61b of the accommodation sites 61.

[0093] The or each of the conductive sub-loops L2,L3 includes a selected minimum separation distance (d-min) between the first accommodation site 61 and the first cable 30, which is the minimum distance therebetween, e.g., as shown in Fig. 2, thus the cable 30 is no closer than the minimum separation distance (d-min) from the closest first accommodation site 61. The minimum separation distance (d-min) provides for the accommodation site 61 to have a portion of the cable 30 near to it, but not so close that the vertical component of the magnetic field due to that portion of the cable 30 falls to substantially zero at the accommodation site 61 (which can occur if the cable 30 lies directly on top of the accommodation site 61). The d-min is selected based on the depth of the sites 61, as described hereinafter, and is generally substantially equal to half of the mutual spacing dO of current conducting elements on opposed sides of each accommodation site 61. Having the minimum distance (d-min) between a central axis of the accommodation site 61 and the closest elements of the cable (30) mitigates the risk of one of the elements carrying its electrical signal (SI) in an opposite direction around the accommodation site, and thus not enhancing the MFD or MI sensitivity (by interfering destructively with the MI signals from the other elements).

[0094] The antenna system 1 disclosure herein may be best for shallow depths of the accommodation sites relative to any antiparallel portions of the MI loop antenna (including the main conductive loop LI and the or all conductive sub-loops L2,L3), thus the antenna plane, and thus the layout of the or each of the conductive sub-loops L2,L3, is selected such that the or each sub-loop L2,L3 is selected to have an average diameter, or spacing, around the or each corresponding accommodation site 61 that is substantially equal to or more than the depth of that accommodation site 61. The mutual spacing (i.e., spacing perpendicular to the current direction and over a centre of the accommodation site 61) of current conducting elements on opposed sides of an accommodation site 61 is selected to be a distance dO. If the hole depths (h) of the accommodation sites 61 are relatively deep, e.g., greater than 10 times the available spacing (for dO) for the MI loop antenna (where "dO" is mutual spacing between opposite elements around the accommodation site 61, thus forming a diameter or a loop width, e.g., as shown in Fig. 2), it may be preferable to select a traditional big loop antenna. Thus, the sub-loops of the MI loop antenna (including the or each of the conductive sub-loops L2,L3) are selected to have a mutual spacing dO of current conducting elements on opposed sides of each accommodation site 61 that is substantially equal to or greater than the hole depth h of that accommodation site 61, including having the mutual spacing dO substantially being the same order of magnitude as the hole depth h. For an example bench with accommodation sites 61 with depths h of substantially 10m or 20m, and mutual spacing between adjacent accommodation sites 61 of substantially 3.8m (e.g., spread over a 1-km by 1.6-km bench), the mutual spacing dO can be selected to be substantially 3.8m.

[0095] Once the sub-loops L2,L3 are arranged (or planned to be arranged) symmetrically surrounding each relevant accommodation site 61 (such that each accommodation site 61 is substantially in the middle of the current carrying elements that generate the MFD for that accommodation site 61 or that detect the MI uplink signals from that accommodation site 61), the mutual spacing dO of the current conducting elements on the opposed sides of each accommodation site 61 may be selected based on: (i) the known determined depth h of the accommodation site 61, and (ii) a predefined relationship between magnetic strength, the depth (h) and the mutual spacing (dO). The predefined relationship is a form of predefined magnetic-strength (Bz) relationship that defines the z-axis magnetic field (Bz) centrally between two current conducting elements as a function of depth h from the plane of the current conducting elements (which is the surface) and the mutual spacing dO of the current conducting elements. In the predefined Bz relationship, the z-axis magnetic field Bz may depend on one or more polynomials of the mutual spacing dO for the known depth h, including a ratio of two or more polynomials. In the predefined Bz relationship, the z-axis magnetic field Bz may be proportional to: 1 w [Equation 1], |0096| Selecting the mutual spacing dO based on the predefined Bz relationship may include selecting a value of dO that optimises the value of the predefined Bz relationship, e.g., selecting a value of dO that optimises Equation 1—and, if more than one value is optimal, then the smallest optimal dO value for a more efficiently spaced sub-loop—unless that dO is larger than the inter-hole spacing (i.e., the spacing of adjacent accommodation sites 61), in which case dO is selected to be as large as possible whilst lying between adjacent accommodation sites 61, e.g., dO can be substantially equal to the spacing of adjacent accommodation sites 61. The optimization of Equation 1 could be referred to as a onedimensional optimization because the process requires finding a smallest value of dO that gives the maximum value of Equation 1. The selection of dO using the predefined Bz relationship, e.g., by optimization of Equation 1, can be very fast, and can thus be incorporated into the method of designing and / or laying out the MI loop antenna, e.g., using hole locations from a blast plan and / or hold location measurements on the bench. |0097| Once the sub-loops L2,L3 are arranged (or planned to be arranged) symmetrically surrounding each relevant accommodation site 61, and spaced with the selected dO apart around each relevant accommodation site 61, as described in the preceding paragraph, an optimal layout of each of the sub-loops L2,L3 is thereby selected, i .e., based on the layout of the relevant accommodation sites 61 and their respective depths h, e g., from a blast plan and / or measurements of as-drilled blastholes, at least for most sub-loop arrangements, e.g., as shown in Figs. 1 to 4; however, for the sub-loop L3h, which has a frond shape, as shown in Fig. 5, the depth and predefined Bz relationship can only define the diameter of the inner current carrying elements, and a further relationship may be required to select the spacing of the outer current carrying elements from the inner current carrying elements. For example, the spacing of the outer current carrying elements from the inner current carrying elements can be determined from the following further relationship where "d2" is the predetermined inner diameter (from "dO" above) and dO is now the spacing of the outer current carrying elements from the inner current carrying elements, and this relationship can also be optimised to find the smallest dO that optimises Equation 2: [Equation 2],

[0098] As shown in Fig. 14: (A) the antenna pattern (represented by MFD in a vertical direction) reaches a high point (representing optimal antenna pattern enhancement) when the site 61 is substantially in the middle, between a pair of antiparallel conductors; and (B) the antenna pattern (represented by MFD in a vertical direction) reaches a low point (representing poor antenna pattern enhancement) when the site 61 is substantially 60% of a spacing outside of a pair of antiparallel conductors. Fig. 14 shows: (A) on the X axis, a distance (in m) of the site 61 from being directly under one conductor of the pair, in a direction toward (and thus under and past) the second conductor of the pair, in a direction perpendicular to the pair of conductors, assuming the spacing of the conductors is 1 m, and the depth of the site 61 is 1 m for the "1 m" curve (thus substantially equal to the spacing of the conductors), 2 m for the "2 m" curve (thus substantially twice the spacing of the conductors), 3 m for the "3 m" curve (thus substantially thrice the spacing of the conductors), etc., up to 10 m for the "10 m" curve (thus substantially ten times the spacing of the conductors); and (B) on the Y axis, the MFD (in dB T) in the Z-axis direction, which is perpendicular to a plane defined by the pair of antiparallel conductors, thus the Y axis shows the Z component of the MFD.

[0099] Accordingly, one or more loops of the MI loop antenna (including the main conductive loop LI and the or all conductive sub-loops L2,L3) are arranged symmetrically around the respective accommodation sites 61 such that each accommodation site 61 is substantially in the middle of pairs of current conducting elements, which form the loop, on opposed sides of each accommodation site 61.

[0100] By having a spacing between mutually anti-parallel current carrying elements, cancellation of opposite contributions is mitigated. The mutually anti-parallel current carrying elements are spatially parallel but carrying the current 11 in opposite directions. By having the mutual spacing dO around the accommodation site 61 that is substantially the same order of magnitude as the depths h of the accommodation site 61, the MI loop antenna can provide improved magnetic field strength (MFD) and sensitivity to uplink signals compared to a traditional large MI loop antenna.

[0101] As shown in Fig. 2, the at least one sub-loop can include a plurality of the open sub-loops L3 arranged mutually adjacently to form a serpentine shape with the corresponding sub-sets of the accommodation sites being mutually adjacent. This serpentine shape is the rectangular-wave pattern.

[0102] In some implementations, the first accommodation site 61a surrounded by the first sub-loop L2a has a first depth from a ground / surface on which the first cable 30 is disposed, the one or more additional accommodation sites 61 includes a second accommodation site 61c outside of the first sub-loop L2a, and the second accommodation site 61c has a second depth from the ground, the first depth being greater than the second depth. Thereby, the first subloop L2a and the second sub-loop L3b are adapted to the respective depths of the accommodation sites so that an MI signal can be effectively transmitted from or to the depths, where a wireless device can be disposed. In some implementations, a first sub-loop L2d has a first number of turns and the second sub-loop L2f has a second number of turns, the first number of turns being greater than the second number of turns. As the first number of turns is greater than the second number of turns, the first sub-loop L2d is able to detect / transmit a Ml signal more strongly than the second sub-loop L2f.

[0103] As shown in Fig 5, a first accommodation site 61b can be surrounded by a first sub-loop L2b (which may have a first depth from a ground on which the first cable 30 is disposed), the one or more additional accommodation sites 61 may include a second accommodation site 61 d outside of the first sub-loop L2b (and the second accommodation site 61 d may have a second depth from the ground, the first depth being greater than the second depth). Thus the sub-loop 33 may be selectively arranged around a deeper accommodation site based on depths known from the blast plan. In some implementations, a smallest distance d-min-1 of a first sub-loop to a first accommodation site surrounded by the first sub-loop may be greater than a smallest distance d-min-2 of a second sub-loop to a second accommodation site, e.g., selected according to the characteristics of the accommodation sites, such as the depth of the accommodation site where a wireless device is to be disposed, the medium of the accommodation site that may affect the transmissivity of the MI signal, or the WEB device located at the accommodation site that may require an Ml signal strength or a certain range of an Ml signal strength. The spacing and loop diameter of the cable 30 are important in terms of positioning, whereas number of turns of a sub-loop will only increase the effective current proportionally since increasing the number of turns provides the same magnetic field pattem / sensitivity of a single loop, but with effective current multiplied by the number of turns. In view of this, the sub-loops according to the present disclosure can be adapted to provide a stronger MI signal according to the characteristics of the accommodation sites, such as the depth of the accommodation site where a WEB device is to be disposed, the medium of the accommodation site that may affect the transmissivity of the MI signal, or the WEB device located at the accommodation site that may require an MI signal strength or a certain range of an MI signal strength. In some implementations, the first accommodation site includes a first depth from a ground on which the first cable is disposed, the first WEB device is received by the first accommodation site at the first depth, and the shape of the first subloop, and / or the number of turns of the first sub-loop, and / or the distance of the first sub-loop to the first accommodation site is adapted to wirelessly transmit the first blasting command through the first magnetic induction, MI, signal to the first WEB device at the first depth. Accordingly, the sub-loop can be adapted to the depth of the accommodation site for effectively transmitting the MI signal to a certain depth at the accommodation site, where a WEB device can be disposed. In some implementations, a shape of the first sub-loop, and / or a number of turns of the first sub-loop, and / or a distance of the first sub-loop to the first accommodation site is adapted such that the first sub-loop enhances the antenna pattern directed to the first accommodation site. In some implementations, each of the first sub-loop and the one or more additional sub-loops surrounds only one accommodation site each. As each sub-loop is adapted to transmit an MI signal to only one accommodation site surrounded the respective sub-loop, the MI signal strength for each accommodation site can be individually adjusted by configuring the respective sub-loop Such configuration can include a shape of the sub-loop, a size of the sub-loop, a number of turns of the sub-loop, or a smallest distance from the sub-loop to the respective accommodation site This facilitates the detection / distribution of the MI signals in view of the diversity of the accommodation sites and the locations of the WEB devices. In some implementations, the first sub-loop is arranged surrounding only the first accommodation site and not surrounding another accommodation site adapted to receive a WEB device. The first accommodation site may be in the middle of the first sub-loop surrounding the first accommodation site. Thereby, the first sub-loop can be adapted according to the characteristics of the single accommodation site (such as a depth of the accommodation site and transmissivity of the medium at the accommodation site).

[0104] In some implementations, the first cable 30 is adapted to form the one or more additional sub-loops L2,L3, the one or more additional sub-loops L2,L3 each being adjacent to and surrounding an arcuate region of more than 90 degrees relative to at least one of the one or more additional accommodation sites. Thereby, the sub-loops (including the first subloop and the one or more additional sub-loops) can serve as localized loop antennas for respective wireless devices at the respective accommodation sites That is, instead of relying a main loop LI encircled by the first cable 30, the antenna system 1 of the present disclosure includes the localized loop antennas L2,L3 placed in close proximity to, and arranged selectively for, the respective accommodation sites (and thus respective wireless devices). As the sub-loops L2,L3 are adjacent to respective accommodation sites, the localized loop antennas can effectively improve the MI signal strength / sensitivity at the respective accommodation sites.

[0105] In some implementations, the first cable 30 is adapted to meander at least partially in the meandering section relative to one or more additional accommodation sites 61 adapted for receiving respective wireless devices, and the first cable 30 is adapted to: receive the first electrical signal SI and / or wirelessly transmit the MI downlink uplink signals (e.g., in blasting implementations, to send a first blasting command through a magnetic induction, MI, signal to one or more WEB devices received by the one or more additional accommodation sites for starting a detonation process of the one or more WEB devices), and / or detect the MI uplink signals and, by induction of current, generate the uplink electrical signal SIA. By meandering the first cable 30 relative to more accommodation sites, the efficiency of transmitting the blasting command to the WEB devices can be improved, and the efficiency of gathering the MI uplink signals can be improved. In the implementation of Fig. 2, the first cable 30 is adapted and arranged to meander at least partially in a meandering section Cl, formed by the mutually adjacent open sub-loops L3, relative to the accommodation site or the accommodation sites 61a, 61b. The accommodation sites 61a, 61b are adapted to receive the wireless devices. The first cable 30 is adapted and arranged to form the open sub-loops L3 in the meandering section Cl. In the implementation of Fig. 2, the meandering section Cl includes five open sub-loops L3 (also referred to herein as "loop sections") and each of the sub-loops surrounds four accommodation sites 61.

[0106] Herein, the wording “surround” means that the cable defines a boundary, either enclosed ("completely surround") or not ("partially surround"), for the accommodation site(s) and may be replaced by or supplemented by (partially) “encircle”, “circulate”, “enclose”, “enclave”, or “envelope”.

[0107] Fig. 3 illustrates a schematic enlarged view of a portion of the open sub-loop L3a shown in Fig. 2. As shown in Fig. 3, the first sub-loop L3a or the first cable 30 in the first sub-loop L3a is arranged adjacent to and surrounding an arcuate region 62 of more than 90 degrees relative to the first accommodation site 61a. From another aspect, the first cable 30 in the first sub-loop L3a is arranged next to the first accommodation site 61a (or the arcuate region 62) while turning around the first accommodation site 61a with an angle 0 of larger than 90 degrees In the embodiment of Figs. 2 and 3, the first sub-loop L3a or the first cable 30 in the first loop section L3a is arranged adjacent to and surrounding an arcuate region 62 of substantially 180 degrees. Namely, the first cable 30 in the first sub-loop L3a is arranged next to the first accommodation site 61a (or the arcuate region 62) while turning around the first accommodation site 61a with an angle of substantially 180 degrees. The arcuate region may expand an angle 0 of greater than 90 degrees, equal to or larger than 100 degrees, equal to or larger than 180 degrees, equal to or larger than 360 degrees, equal to or larger than 360 degrees, or equal to or larger than 720 degrees.

[0108] In some implementations, the first sub-loop L2a includes more than an approximately half turn adjacent to and surrounding the first accommodation site 61a. By having more than an approximately half turn adjacent to and surrounding the first accommodation site 61a, the first sub-loop L2a can locally surround the first accommodation site 61a with approximately 180 degrees or more. This effectively improves the MI signal strength / sensitivity at the first accommodation site 61a, as compared to using the main loop LI.

[0109] In some implementations, the first sub-loop L2a comprises an approximately half to full turn surrounding adjacent to and surrounding the first accommodation site. As shown in Fig. 2, the first sub-loop L2a forms more than an approximately half turn adjacent to and surrounding the first accommodation site 61a. Herein, a half turn means that the cable 30 makes a substantially U-turn around and surrounding the first accommodation site 61a. Additionally or alternatively, a sub-loop may form an approximately half to full turn adjacent to and surrounding the accommodation site. Herein, a full turn means that the first cable 30 makes a 360-degrees turn around the accommodation site.

[0110] As shown in Fig. 3, the first sub-loop L3a is arranged adjacent to and directly facing two opposite sections 63 a, 63b of a perimeter of the first accommodation site 61a. As illustrated in Fig. 3, the first accommodation site 61a has a perimeter in a substantially circular shape. The perimeter of the first accommodation site may, nonetheless, have any shapes defining the boundary of the first accommodation site. The first sub-loop L3a is arranged adjacent to and directly facing the two opposite sections 63a, 63b of the perimeter of the first accommodation site 61a in Fig. 2. The first sub-loop L3a illustrated in Fig. 3 is further arranged adjacent to and directly facing the adjacent section 63c between the two opposite sections 63a, 63b of the perimeter of the first accommodation site 61a. Referring to Fig. 2, the first sub-loop L3a is also arranged adjacent to and directly facing only two opposite sections of the perimeter of the accommodation site 6 If below the first accommodation site 61a.

[0111] As shown in Fig. 2, the first cable 30 of the antenna system 1 includes not only a main loop LI formed by the first cable 30 and its two terminals Tl, T2 but also the first subloop L3a as a localized loop in or forming a portion of the main loop LI. In Fig. 2, the first cable 30 includes the five open sub-loops L3, which are also referred to as five "localized loops" in the meandering section Cl. The main loop LI in Fig. 2 thus includes the five subloops (or "localized loops") serving as localized loop antennas for relaying the MI signal to the accommodation sites surrounded by respective localized loops.

[0112] In some implementations, the first cable 30 is adapted to have at least two corners adjacent to and surrounding the first accommodation site. By having at least two corners adjacent to and surrounding the accommodation site, the first sub-loop is able to locally surround the accommodation site and effectively improve the MI signal strength at the accommodation site. As shown in Fig. 3, the first sub-loop L3a is adapted to have two corners 302,304 adjacent to and surrounding the first accommodation site 61a. In other words, the first cable 30 make at least two turns, forming at least two corners 302,304 to surround the first accommodation site. By arranging the first sub-loop L3a to have two or more comers, the antenna system 1 is able to effectively improve the MI signal strength at the first accommodation site 61a.

[0113] As explained above, the open sub-loop L3a (or "localized loop") is formed within the meandering section Cl to serve as a localized loop antenna within or forming a portion of the main loop LI of the first cable 30. Although Fig. 2 and Fig. 3 illustrate an embodiment of an open sub-loop L3a forming a substantially U-shape, the shape of the sub-loop L3 need not be limited to a particular shape Instead, at least one of the shape of the sub-loop L3, the number of turns of the sub-loop L3, and the minimum separation distance (d-min) of the subloop L3 may be adapted such that the sub-loop L3 serves as the localized MI antenna for receiving / transmitting the MI signals from / to the accommodation site surrounded by the subloop L3 and to the wireless device located at the accommodation site 61. In particular, the first cable 30 may be arranged such that every accommodation site 61 has some portion of the cable 30 near it. Thanks to the minimum separation distance (d-min) between the first cable 30 to the accommodation site 61, and the consistent rotational direction of the current in the first cable relative to the adjacent accommodation sites 61 (surrounding the adjacent accommodation site 61), the current transmitted by the first cable 30 is able to detect / induce an MI signal with a sufficient strength from / to the accommodation site 61.

[0114] The accommodation sites 61 include imperfect holes that have drill deviations, e g., drilled holes that are not exactly perpendicular to the ground, or holes with toes that are skewed from where the collar of the hole. The selected value for the separation distance (d-min) takes into account such hole deviations. The separation distance (d-min) is selected to make sure each wireless device is 'surrounded' and centred by sections / arcs of the cable 30 as much as possible, accounting for hole deviation, and distance between adjacent holes

[0115] In blasting implementations, as illustrated in Fig. 2, the antenna system 1 may be arranged to transmit the blasting command, through an MI signal, to a plurality of accommodation sites 61. In this case, the first cable 30 is arranged to meander relative to the plurality of accommodation sites and thereby transmit the blasting command contained in the first electrical signal SI, through an MI signal, to the accommodation sites and a plurality of WEB devices at the accommodation sites.

[0116] As shown in Fig. 2, the first cable 30 can be arranged to meander relative to twenty accommodation sites and form five sub-loops. Each of the sub-loops is arranged adjacent to and surround four accommodation sites and thereby adapted to serve as a localized MI antenna for the MI signals from / to the surrounded four accommodation sites. The first cable 30 in Fig. 1 thus includes five localized MI antennas within or forming the main loop LI. Each of the sub-loops can be have any of the configurations (including the shape, the distance from the accommodation site, the size) as described herein for the open sub-loop L3a.

[0117] Instead of relying on the main loop LI to detect / transmit an MI signal from / to all of the twenty accommodation sites, the antenna system 1 of Fig. 2 includes five localized MI antennas adapted to detect / distribute the MI signal from / to desirable accommodations sites. This ensures that there will be an MI signal within the sub-loop and facilitates the detection / distribution of the MI signals (e.g., and the blasting command). As a result, it is no longer necessary to conduct a large scale MI signal survey as required in the existing art.

[0118] Fig. 4 illustrates the antenna system 1 according to another implementation In Fig. 4, the first cable 30 is arranged to form a closed sub-loop L2b arranged adjacent to and surrounding only one accommodation site 61b. In this configuration, the closed sub-loop L2b is designated for only one accommodation site and serves as a localized MI antenna to transmit an MI signal to the respective accommodation site. This ensures that there will be sufficient MI signal sensitivity / strength at each of the accommodation sites. There is thus no need to conduct a large-scale MI signal survey to ensure a sufficient MI signal sensitivity / strength from / to the location of each accommodation site or each wireless device.

[0119] With reference to Fig. 4, it would be appreciated that the sub-loop L2b can be provided with different configurations in terms of, for example, the shape of the closed subloop L2b, the size of the closed sub-loop L2b, or the distance of the closed sub-loop L2b to the respective accommodation site 61b.

[0120] Fig. 5 illustrates the antenna system 1 configured according to another implementation. In Fig. 5, the first cable 30 is adapted to form a closed sub-loop L2c with a plurality of full turns (namely, a plurality of 360-degrees turns) around a plurality of accommodation sites 61a,61b Specifically, the closed sub-loop L2c has substantially two-and-a-quarter full turns. In other implementations, it would be appreciated that the closed subloop L2 may include any number of full turns and may further include any fractional turn.

[0121] In some implementations, each of the one or more additional accommodation sites is surrounded by either the first sub-loop or the one or more additional sub-loops. As a result, each accommodation site in the meandering section is surrounded by a sub-loop. Thereby, the respective sub-loops can serve as localized loop antennas to transmit MI signals to the accommodation sites. By arranging a first sub-loop according to the present disclosure, an MI signal can be easily relayed and distributed to, or detected from, the corresponding accommodation site. This improves the MI signal strength at the corresponding accommodation site. Referring to Fig. 4, the accommodation site 61b is surrounded by a subloop in the form of the closed sub-loop L2b, and thus an MI signal sensitivity / strength at the accommodation site 61b is improved and greater than an MI signal sensitivity / strength at the ones of the accommodation sites 61 located outside of the closed sub-loop L2b but still inside the main loop L I (i.e., sites 61 excluding 61b in the arrangement of Fig. 4).

[0122] Referring to Fig. 4, the first accommodation site 61b may have a greater depth from the ground onto which the first cable 30 is disposed and thus a first wireless device at the first accommodation site 61b may be disposed at a greater depth. On the other hand, the second accommodation site 61c may have a smaller depth from the ground and thus a second wireless device may be disposed at a smaller depth from the ground. As the sub-loop L2b is able to improve the MI signal sensitivity / strength of the accommodation site 61b, it is possible to receive / transmit the MI signal from / to the first wireless device at the accommodation site 61b without the need of increasing the current of (or reducing the noise of) of the electrical signals SI, SI A and provide a localized MI antenna adapted to the characteristics of the accommodation site 61b. The antenna system 1 can thus effectively detect / distribute the MI signal from / to only desirable accommodation sites in the signalling area 60 by the first cable 30. This makes the collection / distribution of the MI signals much easier and mitigates the need for a large-scale MI signal survey as required in the existing art.

[0123] Fig. 5 illustrates the antenna system 1 according to another implementation. In Fig. 5, the first cable 30 is adapted to form three closed sub-loops L2 and one open sub-loop L3h (which is a form of “frond” loop). The sub-loop L2a includes two-and-a-quarter full turns adjacent to and completely surrounding a sub-set of two accommodation sites 61 a,61b. The sub-loop L2d includes three-and-a-half full turns adjacent to and completely surrounding only one accommodation site 61 e. The open sub-loop L3h includes less than one full turn adjacent to and substantially surrounding the accommodation site 61 n, but the cable 30 is doubled back on itself to effectively provide an open sub-loop for the accommodation sites 6 Ij, 6 li, 61h, 61m, 61r, 61s and 61o that are adjacent to and surrounding the open sub-loop L3h. The subloop L2f is adjacent to and completely surrounding the accommodation site 6It with two-and-a-quarter full turns. It would be appreciated that the arrangement in Fig. 5 is exemplary and that variations and modifications can be made based on the description of the closed subloops L2. For example, the sub-loops L2e,L2d,L2f may each include a single full turn or more than two full turns and may further include any fractional turn, e g., selected based on conductivity of the rock and depth of the wireless device in the corresponding accommodation site 61. With reference to the open sub-loop L3h, "open loop" may refer to the cable sections not completely surrounding the accommodation site, and "closed loop" may refer to the cable sections completely looping around an accommodation site, potentially multiple times.

[0124] As illustrated in Fig. 5, the first cable 30 can be adapted to form a plurality of subloops L2,L3 of different configurations. Such configurations may be adapted to the respective accommodation site(s) surrounded by the respective sub-loops L2,L3. For example, the subloop L2c may be adapted to detect / transmit the MI signals from / to the two accommodation sites 61a, 61b with similar characteristics that are different from those of the accommodation sites 61c, 6Id, etc. surrounded only by the main loop LI. As another example, the sub-loop L2d may be adapted to transmit an MI signal to the accommodation site 61e that required a greater sensitivity / strength than the accommodation sites 61c, 61 d, etc. surrounded only by the main loop LI. Thereby, both of the sub-loop L2c and the sub-loop L2d can each effectively relay an MI signal to, or receive an MI signal from, the respective depth of the accommodations site where a wireless device can be disposed. The antenna system 1 is thus able to facilitate the distribution of the MI signals to, and / or the gathering of the MI signals from, the accommodation sites and the wireless devices.

[0125] As illustrated in Figs. 1 to 5, the cable 30 may form the main loop LI and the subloops L2, L3 as a single continuous cable arranged around the accommodation sites 61 of the working area 50. Alternatively, the cable 30 may include additional electrical terminals in the arrangement on the working area 50, including in the main loop LI and between the sub-loops L2, L3, to allow shorter portions of cable to be joined to form the cable 30 (which may allow to simultaneous arrangement of a plurality of the sub-loops L2, L3 for a more efficient layout). Each of the shorter portions of cable may be electrically connected, in series or in parallel, so long as the cable 30 carries the same electrical signal S2, having the same frequency and phase in the main loop LI and the sub-loops L2, L3. The electrical frequency and the phase are constant, including when using series and parallel configurations. The wavelength of the electrical signals are typically in hundreds of kilometres, so the cable length, even on a 1km bench, is negligible, so phase changes in different cable sections would be negligible. Signal Transmission Arrangement Ml for Downlink

[0126] In the downlink implementations, the antenna system 1 further includes a signal transmission arrangement Ml adapted to emit and transmit the first electrical signal SI comprising the first blasting command to the first cable.

[0127] Fig. 6 illustrates the antenna system 1 including a signal transmission arrangement ML In an embodiment, the antenna system 1 according to the present disclosure may include the signal transmission arrangement Ml, to which the first cable 30 is connected to receive the first electrical signal SI.

[0128] In some implementations, a frequency tuning component, which can include a tuning circuit 70 (typically including at least one tuneable or replaceable capacitor and associated electronic components to provide a selectable capacitance for tuning the MI loop antenna), is connected (generally in series) between one of two terminals of the first cable 30 and an output of the first transformer arrangement 20. In particular, the tuning circuit 70 is adapted to optimize the current of the first electrical signal SI transmitted by the first transformer arrangement 20, or the current SIA detected by the Ml loop antenna.

[0129] In some embodiments, the antenna system 1 may include the tuning circuit 70 in series between an output of the signal transmission arrangement Ml and one of the terminals Tl, T2 of the first cable 30 (as illustrated in Fig. 6).

[0130] The tuning circuit 70 can be a variable capacitor. As the shape of the MI loop antenna differs depending on the layout of the accommodation sites and the WEB device depths (and rock reluctance), the inductance of the cable arrangement between the terminals Tl, T2 is generally difficult to predict in advance, and thus having a variable capacitor will allow better control of tuning, e.g., after design of the specific cable arrangement for a given working area 50, or after physically laying out the cable arrangement (thus allowing the actual cable layout to differ substantially from a design thereof because the tuning circuit 70 is tuned to the actual layout rather than the design).

[0131] Fig. 7 illustrates the antenna system 1 including an exemplary configuration of the signal transmission arrangement Ml according to an embodiment.

[0132] In some implementations, the signal transmission arrangement comprises a first transformer arrangement 20 adapted to receive and convert a second electrical signal S2 emitted by a signal generator 10 into the first electrical signal SI. In an implementation, the transformer arrangement is adapted to step down a voltage of the second electrical signal S2 and thereby convert the second electrical signal S2 into the first electrical signal SI. Thereby, the antenna system can be arranged adjacent to the signalling area 60 for relaying and distributing MI signals to accommodation sites in the signalling area 60 while receiving an electrical signal comprising the blasting command from the signal generator 10 (which can be a distant signal generator, i.e., distant from the MI loop antenna and the working area 50) via another cable, referred to as the "second cable 40" (to differentiate it from the "first cable 30") and the "extension cable 40" (because it extends the electrical signal from the current generator 11 over a substantive distance to the "antenna cable 30" that forms at least a portion of the MI loop antenna). As a result, the amplitude of the current circulating inside the first cable 30 can be adjusted by the voltage step-down device and generally kept much lower than 200 root-mean-squared Amps (Arms) (which is the amount of current generated by the signal generator 10 in the existing art). This allows for driving a much longer cable and deploying the MI loop antenna to cover a longer range of communication. Also, since the first cable 30 does not need to carry a significant amount of current, it can be made low cost and treated as consumable. The second cable 40 in Fig. 7 will have less current running in it, compared to cable 30 because the number of turns of coil 21 is more than the number of turns of coil 22, so the second cable 40 can have a lower current rating and be cheaper than cable 30.

[0133] The signal transmission arrangement Ml may include a first transformer arrangement 20 adapted to receive and convert a second electrical signal S2 into the first electrical signal SI and output the first electrical signal SI to the terminals Tl, T2 of the first cable 30. The first transformer arrangement 20 may be adapted to transform (eg., step down) a voltage of the second electrical signal S2 and thereby convert the second electrical signal S2 into the first electrical signal SI. A voltage of the first electrical signal SI can be stepped down and lower than the voltage of the second electrical signal S2. The first transformer arrangement 20 may include two inputs 20a for connecting to the second cable 40 and receiving the second electrical signal S2 from the second cable 40.

[0134] In some implementations, the second cable 40 is adapted to receive the second electrical signal S2 from the signal generator 10 and transmit the second electrical signal S2 to the first transformer arrangement 20, the second cable 40 being a high voltage rated electrical cable adapted for high power transmission. The second cable 40 can therefore transmit a second electrical signal S2 with a high voltage. Due to the minimized power loss in high voltage transmission, the second cable 40 can be used to transmit the second electrical signal S2 for a long distance from the signal generator 10 to the first transformer arrangement 20 near the blast site. After the stepping down the voltage at the first transformer arrangement 20, the first cable can transmit the first electrical signal SI with a stepped-down voltage to relay the MI signals through the sub-loop to the accommodation site. Due to the stepping-down process performed by the first transformer arrangement 20, the first cable does not need to carry a high voltage electrical signal and therefore a low-cost first cable can be used for relaying the MI signal in the blast area; however, this cable might need to carry a relatively high current, up to substantially 10 A.

[0135] By including the first transformer arrangement 20, the antenna system 1 may be adapted to be connected to the signal generator 10 via the second cable 40 to receive the second electrical signal S2 output by the signal generator 10. Thereby, the antenna system 1 can be arranged adjacent to the signalling area 60 for relaying and distributing Ml signals to accommodation sites in the signalling area 60. Since the first transformer arrangement 20 is adapted to step down the voltage of the second electrical signal S2, the second electrical signal S2 can have a high voltage for long-distance transmission. The signal generator 10 may therefore be positioned at a location distant from the signalling area 60 and away from the effect of the explosion. In addition, by including the first transformer arrangement 20, the antenna system 1 can be adapted to transmit a wide range of voltages of the electrical signal and not be limited to the voltage of the first electrical signal SI to be transmitted by the first cable 30.

[0136] As a result, the amplitude of the current circulating inside the first cable 30 can be adjusted by the voltage step-down device and generally kept much lower than 200 Arms (which is the amount of current generated by a signal generator in the existing art) This allows for driving a much longer cable and deploying the MI loop antenna to cover a longer range of communication. Also, since the first cable 30 does not need to carry a significant amount of current, it can be made low cost and treated as consumable, e.g., using cheaper cable may have poorer insulation, and thus not be able to carry as high a voltage. In some applications, e.g., blasting, the cable 30, or least the portion thereof in the working area 50 (also known as the blasting area / site), is selected to be disposable so that it can be damaged / destroyed / lost / buried in use, e.g., when blasting primers at the sites 61.

[0137] Here, the first transformer arrangement 20 may be a step-down transformer. The first transformer arrangement 20 as a step-down transformer may include a primary coil 21 and a secondary coil 22 inductively coupled and disposed adjacent to each other. The tuning circuit 70 may be connected in series between one of the terminals Tl, T2 of the first cable 30 and the output 20b of the first transformer arrangement 20. The tuning circuit 70 may thus help regulate and optimize the current induced in the secondary coil 22. The turn ratios of the primary coil 21 and the secondary coil 22 may be configured to control the amount of current carried by the first cable 30. The tuning circuit 70 is only responsible for tuning the MI loop antenna, therefore maximizing the current running in the cable 30 for detection / transmission of the MI signals. Dynamic tuning of the antenna system 1 excluding the MI loop antenna (before coil 21) may be handled dynamically by the Current Generator 11. After the antenna pattern has been designed / selected, and / or after the cable 30 has been laid out (thus forming the sub-loops L2,L3), a total inductance of the cable 30 (forming the selected antenna pattern) can be estimated / simulated / measured, and from that a value of capacitance for the tuning circuit 70 can be calculated / selected / provided for proper tuning of the MI loop antenna.

[0138] In some implementations, the first transformer arrangement 20 may include an amplifier or circuit, e.g., a switched step-down circuit such as a known step-down converter or buck converter, adapted to step down a voltage of the second electrical signal S2 and thereby convert the second electrical signal S2 into the first electrical signal SI.

[0139] Figs. 8 and 9 illustrate the antenna system 1 including exemplary configurations of the signal transmission arrangement Ml according to other embodiments.

[0140] In some implementations, the first transformer arrangement 20 is connected to a base coil 122 to receive the second electrical signal S2, and the base coil 122 is adapted to be inductively coupled with a loop antenna 121 (which may be referred as a "source loop antenna 121" or a "primary-side loop" because it is on the primary side of a second transformer arrangement 12 formed by the loop antenna 121 and the base coil 122, which itself may be referred to as a "secondary-side loop") connected to a current generator 11, and the current generator 11 is adapted to generate and transmit a source electrical signal SO to the loop antenna 121, the base coil 122 is adapted to provide the second electrical signal S2 induced by the source electrical signal SO in the loop antenna 121, and the base coil 122 is adapted to step up a voltage of the source electrical signal SO and thereby convert the source electrical signal SO into the second electrical signal S2. By including the base coil 122, the antenna system is able to receive a source electrical signal SO from a loop antenna 121, and transmit a second electrical signal S2 with a stepped-up voltage, which minimizes power loss resulting from the long electrical cable resistance of the long cable 40.

[0141] In Fig. 8, the signal transmission arrangement Ml includes the first transformer arrangement 20 and the second cable 40 as described above. The signal transmission arrangement Ml further includes the base coil 122 connected to the input 20a of the first transformer arrangement 20 via the second cable 40. The base coil 122 may be provided with a plurality of turns. The base coil 122 may be inductively coupled with the source antenna coil to inductively generate the second signal S2 when a source electrical signal SO is transmitted through the source antenna coil The base coil 122 may be adapted to step up a voltage of the source electrical signal SO and thereby convert the source electrical signal SO into the second electrical signal S2.

[0142] By including the base coil 122, the antenna system 1 is able to inductively generate and transmit the second signal S2 by placing a source antenna coil adj acent to the base coil 122. The source antenna coil may be a source loop antenna 121 that is generally used in the existing art to wireless transmit an MI signal through a dense medium for a long distance, which can be maximally 850 meters. The antenna system 1 is thereby compatible with known wireless signal transmitters, e.g., the ORICA WEBGEN transmitters. Because the base coil 122 may step up a voltage of the source electrical signal SO, the antenna system 1 can transmit the second electrical signal S2 with a high voltage via the second cable 40 for a long distance. It is thus possible to minimize the power loss resulting from the long electrical cable resistance. As a result, in blasting implementations, the signal generator 10 can be moved away from the signalling area 60 and the explosion. Also, the distance between the first transformer arrangement 20 and the accommodation sites can be reduced to avoid the power loss in the first cable 30.

[0143] Fig. 9 illustrates the antenna system 1 including a signal transmission arrangement according to another embodiment. The signal transmission arrangement of Fig. 9 differs from the signal transmission generator of Fig. 8 in that the signal transmission arrangement of Fig. 9 further includes the signal generator 10 that drives the source loop antenna 121 (or source antenna coil). The disclosure regarding the first transformer arrangement 20 and the first cable 30 of Figs. 1 to 7 are applicable to the same components illustrated in Fig 9 and thus omitted hereinafter.

[0144] In some implementations, the signal generator 10 comprises a current generator 11 and the second transformer arrangement 12, the current generator 11 being adapted to generate a source electrical signal SO and the second transformer arrangement 12 being adapted to receive the source electrical signal SO, step up a voltage of the source electrical signal SO, and thereby convert the source electrical signal SO into the second electrical signal S2. By stepping up a voltage of the source electrical signal SO and thereby converting the source electrical signal SO into the second electrical signal S2, the second electrical signal S2 with a stepped-up voltage can be delivered with minimized power loss. Then, the voltage of the second electrical signal S2 can be stepped down by the first transformer arrangement 20, which is connected to the first cable 30 and arranged near the working area 50. The first electrical signal SI with its stepped-down voltage is then transmitted to the first cable 30 and the or each sub-loop L2,L3 of the MI loop antenna to relay the MI downlink signals to the accommodation sites The antenna system 1 can thus transmit the second electrical signal S2 with a high voltage via the second cable 40 for a long distance It is thus possible to mitigate power loss resulting from the long electrical cable resistance of the second cable 40, which can be selected to be longer than the first cable 30, and conveniently connected together via the first transformer arrangement 20 (which generally carries the frequency and phase of the second electrical signal S2 into the first electrical signal SI, and thus any signals / data therein, whilst reducing the voltage from the second electrical signal S2 to the first electrical signal SI).

[0145] As illustrated in Fig. 9, the antenna system 1 may include the signal generator 10. The signal generator 10 may include a current generator 11 configured to generate and output a source electrical signal SO via the outputs 11b. The signal generator 10 may further include the second transformer arrangement 12 configured to receive the source electrical signal SO via the inputs 12a, which are connected to the outputs 1 lb of the current generator 11 through a cable pair. The second transformer arrangement 12 is further configured to step down the voltage of the source electrical signal SO and thereby convert the source electrical signal SO into the second electrical signal S2. The second transformer arrangement 12 then outputs the second electrical signal S2 through the outputs 12b to the second cable 40 connected to the outputs 12b or to the outputs 10b of the signal generator 10, which are then connected to the second cable 40.

[0146] Here, the second transformer arrangement 12 may be a step-up transformer. In some implementations, the second transformer arrangement 12 may include an amplifier or circuit, e g , a switched step-up circuit such as a known step-up converter or boost converter, adapted to step up a voltage of the source electrical signal SO and thereby convert the source electrical signal SO into the second electrical signal S2.

[0147] The current generator 11 may be connected to a work station (not illustrated) for receiving a command of generating the source electrical signal SO, which contains a blasting command for instructing the WEB device to start a detonation process. The current generator 11 may include an input interface and a processor configured to generate the command of generating the source electrical signal SO based on a user’s operation through the input interface. The blasting command may be designated and / or encrypted for specific WEB devices. Sealed Coil Generator

[0148] In some implementations, as shown in Fig. 15, the second transformer arrangement 12 can include a magnetic core 1502 between the loop antenna 121 and the base coil 122. The magnetic core 1502 provides a low reluctance path for the magnetic flux generated by the loop antenna 121 to travel to and induce current in the base coil 122. The magnetic core 1502 includes low reluctance materials to form the low reluctance path, e g., ferromagnetic materials, e g., including iron / ferrite. As shown in Fig. 15, the antenna system 1 may include an enclosure 1504 that encloses the current generator 11 and the loop antenna 121, and thus encloses a primary side of the magnetic core 1502; however, as shown in Fig. 15, the enclosure 1504 does not enclose a secondary side of the magnetic core 1502, nor does it enclose the base coil 122, thus the secondary side of the magnetic core 1502 is physically, mechanically and magnetically accessible outside the enclosure 1504, and thus the base coil 122 can be arranged on and physically connected to and magnetically coupled to the secondary side while the enclosure 1540 remains sealed. The enclosure 1504, e.g., a sealed box, can thus protect the current generator 11 and the loop antenna 121 from moisture / dust / dirt / impact, which may be common in a mining / quarrying / civil-engineering site, whilst still allowing the base coil 122 (the secondary side) to be connected (e.g., manually connected) in the method of deployment disclosed herein. The base coil 122 may be manually wound around the core 1502, e.g., if the core 1502 does not have a gap as shown in FIG 15.

[0149] As shown in Fig. 16, the magnetic core 1502 may include a slot / gap 1602 through which the base coil 122 can be moved / slid in order to couple the base coil 122 with the magnetic core 1502 and thus form the second transformer arrangement 12 ready for use.

[0150] As shown in Fig. 17, the magnetic core 1502 may also include a movable element 1702 (e.g., a hinge as shown in Fig. 17, or a ferromagnetic sliding member or piece) that can increase the gap 1602 in order to receive the base coil 122 by being moved / slid, and that can decrease the gap 1602 after the base coil 122 is in place (including to substantially close the gap 1602), coupled with the magnetic core 1502 and thus forming the second transformer arrangement 12 ready for use. By way of the movable element 1702, the magnetic core 1502 can move to clamp onto the base coil 122.

[0151] After use of the second transformer arrangement 12 for the signalling, the base coil 122 can be removed from the enclosed current generator 1506 without needing to expose any part of the current generator 11 to the site. This may include manually removing the base coil 122 from the magnetic core 1502, e.g., manually, after a blasting / signalling operation. Signal Receiver Arrangement for Uplink

[0152] In the uplink implementations, the antenna system 1 further includes a signal receiving arrangement 1800 adapted to detect the uplink electrical signal SIA representing the currents induced by the MI uplink signals in the first cable 30. As shown in Fig. 18, the signal receiving arrangement 1800 (also referred to as a "signal receiving system") includes a receive (RX) frequency tuning component 1802 with an equivalent configuration to the frequency tuning component (e.g., including tuning circuit 70) described hereinbefore, used for the same purpose, i.e., tuning the signal receiving arrangement 1800 to match / include the communication frequencies in the uplink signal. As with the tuning circuit 70, the RX frequency tuning component 1802 can include at least one tuneable or replaceable capacitor and associated electronic components to provide a selectable capacitance for tuning the MI loop antenna, e g., connected (generally in series) between one of two terminals T1,T2 of the first cable 30 and an input of a low-noise preamplifier component 1804 (also referred to as a "front end amplifier") that delivers the uplink signals, in electronic form, to a signal processor 1806 of the signal receiving arrangement 1800, as shown in Fig. 18, to extract / demodulate the uplink signals for storage and / or transmission to an operational control system, e.g., as used for ORICA's WEBGEN system.

[0153] In examples, the signal processor 1806 may include analog processing elements, including a high selectivity band pass filter, and digital processing elements, including a digital signal processor (DSP). The DSP may be configured to extract an uplink message from the uplink signals having error control coding that offers additional digital signal processing gain to the overall SNR. The signal processor 1806 may include highly selective signal filtering after the low noise amplifier 1804 to reduce the noise and boost the received signal to noise ratio (SNR). The signal processor 1806 may apply the error control decoding to provide an additional signal processing gain on top of the analogue gain from the signal filtering.

[0154] In an example of the signal receiving arrangement 1800, the low noise amplifier 1804 may have substantially 90nV / sqrt(Hz), and the signal processor 806 may include a two-section Butterworth band-pass active filter with a very narrow bandwidth (substantially 50Hz), and digital signal correlation to provide signal processing gain

[0155] The MI uplink signals, and thus the uplink electrical signal SIA, can provide uplink communication, e.g., as described in Singapore Provisional Patent Application No. 10202301716Y, filed on 16 June 2023 in the name of Orica International Pte Ltd, and in related International Patent Application PCT / SG2024 / 050396, also in the name of Orica International Pte Ltd, the originally filed specifications of which are hereby incorporated by reference in their entireties herein. The uplink communication can represent a wireless measurement, made by the wireless device, or an acknowledgement signal from the wireless device, e.g., to confirm that the wireless device had received one of the MI downlink signals, or a data log, or sensor measurement results, or data used for mesh networking. Alternatively or additionally to providing the uplink communication, the MI uplink signals, and thus the uplink electrical signal SI A, can include / represent electromagnetic pulses (BMP) from explosions and blasts, including from blasts initiated by the wireless devices in the form of wireless initiation devices or primers. Example Implementations

[0156] In an example implementation of the signal transmission arrangement Ml, the loop antenna 121 was provided by a WEB GEN QUADLOOP antenna, the current 10 was substantially 50 Amps (RMS), the magnetic core 1502 included a ferrite core, the second current 12 in the second cable 40 (or "extension cable") was substantially 1 Anns, the voltage U2 across the second cable 40 was substantially 240 Vrms, and the first current II was substantially 6 Arms in the first cable 30, which was enough to operate the MI loop antenna formed using a disposable type of the first cable 30, as tuned by the tuning circuit 70.

[0157] Example implementations will be described hereinafter with reference to Figs. 10 to 12 to show the effect of the antenna system 1 according to the present disclosure on the MI signal strengths at the accommodation sites. Numerical simulations were performed, using a commercially available computational electromagnetics simulator, to simulate the MI signal strengths relative to the main loop LI and the sub-loops L2, L3. In the numerical simulations for Figs. 10 to 12: the frequency of the MI signals was selected to be 2 kHz (this simulates the carrier frequency of the MI signals, and the carrier frequency is selected to be at the resonant frequency of the MI loop antenna formed by the cable 30); the current II was selected to be 1 Amp (RMS); the depth of the simulated measurements was selected to be 2 m below the cable 30; and the strength was measured by determining the magnetic flux density along the Z-axis, i e , vertically (as the cable 30 is arranged horizontally). The measurements in Figs. 10 to 12 are of the magnitude of the magnetic flux density (MFD) in decibel Tesla (dBT). The simulation simulated having an MI receiver with an orientation along the Z-axis, namely facing upward toward the ground, thus along the axis of the plane in which the main loop LI is arranged. The simulation values were selected to be scaled up for a real-world application, e.g., the 2m depth and 20m loop side scales up to a real depth of 20m and a real loop side of 400m, e.g., as could be used in a 400-m mine / quarry bench.

[0158] By way of a comparative example, a prior art arrangement was simulated to measure MFD from a prior art rectangular loop 1002. In the simulation, the prior art loop 1002 was selected to have sides 20 metres long (on all sides, thus forming a square loop) comprising one turn of the 1-A current-carrying conductor. As shown in Fig. 10, the MFD in the prior art loop 1002 was substantially below -169 dBT in the central half of the rectangle / square. As can be seen in Fig. 10, the Ml signal strength is very strong near the perimeter of the cable loop. As the Ml receiver moves further toward the center of the cable loop, the MI signal strength is significantly reduced. This shows the lack of efficiency of the existing antenna loop, which simply forms a main loop by the cable and its two terminals. Fig. 11 illustrates an example closed sub-loop 1102 in an example main loop 1104. In the numerical simulation for Fig. 11: the main loop 1104 was substantially square, with sides of 20 m each, formed by one turn of the 1-A current-carrying conductor; and the closed sub-loop 1102 was substantially square, with sides of 2 m each, formed by two-and-a-quarter turns of the 1-A current-carrying conductor. As shown in Fig. 11, the MFD in the sub-loop 1102 is enhanced (at around -158 dBT) compared to the MFD at a similar distance from the cable 30 in other areas of the main loop 1104 (less than -164 dBT). Fig. 12 illustrates an example plurality of open sub-loops 1202 to 1208 in, or forming a portion of, an example main loop 1210. As shown in Fig. 12, the MFD in each of the sub-loop 1202 to 1208 is enhanced (at around -164 dBT along the centre line of each sub-loop 1202 to 1208) compared to the MFD around the centre of the prior art loop 1102 of equivalent size (at under -170 dBT in the central half).

[0159] As described above, the antenna system 1 according to the present disclosure need not compromise any benefits of the existing MI system, e.g., as used for wireless blasting. In blasting implementations, the blast hole loading process may be done as in the existing art to prepare an accommodation site and load a WEB device at the accommodation site. It is thus possible to mitigate the need for large scale MI signal surveys. Since the relayed MI signal distribution can be precisely managed through the first cable, the only uncontrolled factor left is the short path between the hole collar and its toe.

[0160] In another aspect, the present disclosure provides a method of deploying the antenna system as described above in one or more MI signalling areas, each including a plurality of accommodation sites, the plurality of accommodation sites being adapted for receiving respective wireless devices. The method includes arranging the first cable 30, e.g., by an autonomous vehicle or remote-controlled vehicle, to extend around the one or more MI signalling areas 60 and to serve as a remote antenna to wirelessly receive / transmit the MI signals from / to the respective WEB devices, wherein the first cable is arranged to form the at least one sub-loop, e.g., the sub-loop being adjacent to and surrounding an arcuate region of more than 90 degrees relative to one of the plurality of accommodation sites.

[0161] According to the present disclosure, a method of deploying the antenna system 1 is provided. The method includes deploying the antenna system 1 in one or more signalling areas 60. When there are a plurality of signalling areas 60, each of the one or more signalling areas 60 may include a plurality of accommodation sites, which are adapted to receive respective wireless devices.

[0162] Thereby, it is thus possible to effectively relay and gather / distribute the MI signal to only desirable signalling areas or accommodation sites in the signalling area by the first cable 30. Although the MI signals transmitted to or by the first cable 30 tends to be confined locally, it is certain that there will be MI signal where the first cable 30 is. The first cable 30 can be placed close to the signalling area, the accommodation site in the signalling area, the wireless device, or any explosive materials in the accommodation site. This, in effect, minimizes the distance between the first cable and the WEB device or explosive materials at the accommodation site of the blast area, which makes the gathering / distribution of the MI signal much easier. Even more notably, this mitigates the need for a large scale MI signal survey as required in the existing art.

[0163] Referring to Fig. 13, the method may include a step 100 of arranging the first cable 30 to send the uplink electrical signal SIA to the electronic signal receiver arrangement. The method may include, repeatedly: measuring the uplink signals (e.g., measuring SNR, magnetic field strength, etc.) from the wireless devices in the sites 61 using the MI loop antenna, and then arranging (and re-arranging / adjusting) the layout / arrangement of the main loop L I and the sub-loops L2,L3 to improve the measured uplink signals. This repeated rearranging while measuring the uplink signals provides a dynamic tuning / layout / adjustment of the MI loop antenna in real time. As the uplink and downlink both experience the same attenuation through the ground (TTE), the uplink detection acts as a live feedback to tell an operator or the system how much MI signal gets through from the MI loop antenna to each site 61 with a wireless device, including as a particular cable layout on the surface is changed / re-arranged. This method may allow for optimization of the arrangement of the cable 30 for a specific arrangement of the wireless devices in the sites 61 using the uplink signals.

[0164] In the signalling implementations, i.e., using the MI downlink, as illustrated in Figs. 6 to 9, the signal transmission arrangement may include provide the tuning circuit 70 in series between an output of the signal transmission arrangement Ml and one of the two terminals Tl, T2 of the first cable 30. Thereafter, in a step 200, the first cable 30 is arranged to extend from the signal transmission arrangement into the one or more blast areas and to meander at least partially in a meandering section relative to the accommodation site(s) in the blast area(s) so that the first cable forms one or more sub-loops in the meandering section to serve as a localized MI loop antenna to wirelessly transmit a blasting command through a MI signal to the accommodation site(s).

[0165] In the method according to the present disclosure, the first cable 30 may be deployed to any of the configurations described herein with reference to Figs. 1 to 9 and Figs. 11 to 12 The step 200 of extending the first cable 30 into the blast area(s) may be performed by an autonomous vehicle so as to remove humans from site specific hazards. In particular, the first cable 30 can be connected to the outputs of the signal transmission arrangement Ml (or the outputs of the first transformer arrangement 20) by utilizing IKON clip-on connectors. This allows fast implementation in the field, especially when the first cable is to be deployed only a short time before the blast. In addition, the step 200 is less error prone than clipping wire (e.g., IKON leg-wires) to firing lines and therefore the method according to the present disclosure is more automation friendly.

[0166] In the present disclosure, the first cable 30 may have a lower current compared to the 200 A current of existing commercial MI antennas used for blasting, e.g., ORICA's WEBGEN antenna. The first cable 30 can thus operate using lower currents, therefore any antenna / cable involved may thus be disposable and made of some low-cost, readily available cable such as IKON receiver (RX) wire. It is thus possible to save costs and easily replace the first cable after one detonation process. On the other hand, the signal transmission arrangement Ml may be treated as non-consumable. Interpretation

[0167] The above embodiments and modifications are not intended to limit the scope of the present invention. Rather, the present invention covers various modifications based on the features disclosed herein, such as a combination of two or more features described above in different embodiments or removal of a feature from an embodiment, within the scope of the present invention. For example, the first cable according to the present disclosure may be arranged to have any combinations of the sub-loops L3, L2 as illustrated in Figs. 1 to 5. Further, it is to be noted that the figures are merely illustrative and should be interpreted as limiting to the scope of the invention. For example, although the sub-loops L3, L2 are illustrated to have three or four straight sides surrounding the accommodation site(s), it would be appreciated that the sub-loop may have any shape surrounding the accommodation site(s), such as an eclipse, a circle, or any polygonal shapes.

[0168] In the implementations as illustrated with the figures, the antenna system 1 includes a single set of a signal transmission arrangement Ml (for example, abase coil 122, a second cable 40, and a first transformer arrangement 20) and a first cable 30. In some implementations, the antenna system 1 may include multiple of such sets to cover a larger blast area or a plurality of blast areas. In some implementations, when the antenna system 1 includes multiple sets of a base coil 122, a second cable 40, and a first transformer arrangement 20 and a first cable, each of the sets can be coupled with a single loop antenna (for example WEBGEN QUADLOOP antennas). In some implementations, the antenna system 1 may include multiple sets of first cables 30 connected to a single signal transmission arrangement Ml (for example, a single set of a base coil 122, a second cable 40, and a first transformer arrangement 20), wherein each of the first cables 30 may be connected to the outputs of the same first transformer arrangement 20.

[0169] Accordingly, the above embodiments and modifications are exemplary and illustrative. It would be understood that the scope of the present invention is not limited by the above disclosure, but defined by the claims hereinafter. The reference numerals and alpha numerals in the detailed description are not intended to limit the scope of the related terms in the detailed description but are intended only to refer to exemplary embodiments in the drawings.

[0170] The MI signal can include frequencies of substantially 2kHz or 1.8 kHz, or between 1 kHz and 3 kHz, or between 100 Hz and 10 kHz, or between 0.1 kHz and 200 kHz, or between 1 kHz and 10 kHz, or between 10 kHz and 50 kHz, or between 50 kHz and 100 kHz, or between 100 Hz and 100 kHz, or between 100 kHz and 200 kHz, or between 120 kHz and 130 kHz. The MI signal can include at least one frequency within the ultra low frequency (ULF) band, or within the very low frequency (VLF) band as defined by the International Telecommunications Union (ITU).

[0171] The "blasting command" may include a "SYNCH" command, an "ARM" command, a "DELAY CHANGE REQUEST", a "STATUS CHECK REQUEST" and / or a "FIRE", some of which control the wireless device to generate and send uplink signals, e g., as used in the WEB GEN system.

[0172] As used herein, the terms “set” and "sub-set" each corresponds to or is defined as a non-empty finite organization of elements that mathematically exhibits a cardinality of at least 1 (i.e., a set as defined herein can correspond to a unit, singlet, or single element set, or a multiple element set), in accordance with known mathematical definitions (for instance, in a manner corresponding to that described in An Introduction to Mathematical Reasoning: Numbers, Sets, and Functions , “Chapter 11 : Properties of Finite Sets” (e.g., as indicated on p. 140), by Peter J. Eccles, Cambridge University Press (1998)). Thus, a set includes at least one element. In general, an element of a set can include or be one or more portions of a system, an apparatus, a device, a structure, an object, a process, a procedure, physical parameter, or a value depending upon the type of set under consideration.

[0173] The FIGs. included herewith show aspects of non-limiting representative embodiments in accordance with the present disclosure, and particular structural elements shown in the FIGs. may not be shown to scale or precisely to scale relative to each other. The depiction of a given element or consideration or use of a particular element number in a particular Fig or a reference thereto in corresponding descriptive material can encompass the same, an equivalent, an analogous, categorically analogous, or similar element or element number identified in another Fig. or descriptive material associated therewith The presence of “ / ” in a Fig. or text herein is understood to mean “and / or”, i.e., “X / Y” is to mean “X” or “Y” or “both X and Y”, unless otherwise indicated. The recitation of a particular numerical value or value range herein is understood to include or be a recitation of an approximate numerical value or value range, for instance, within + / - 20%, +1- 15%, + / - 10%, + / - 5%, +1- 2.5%, + / 2%, +1- 1%, + / - 0.5%, or + / - 0%. The term “essentially all” or “substantially” can indicate a percentage greater than or equal to 50%, 60%, 70%, 80%, or 90%, for instance, 92.5%, 95%, 97.5%, 99%, or 100%.

[0174] Many modifications will be apparent to those skilled in the art without departing from the scope of the present invention. - 45 -

[0175] Throughout this specification and any claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0176] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Claims

1. A magnetic induction (MI) antenna system adapted to wirelessly transmit and / or receive MI signals, through solid material, respectively to and / or from a plurality of wireless devices in respective accommodation sites, the antenna system comprising:an antenna cable adapted to:- receive a first electrical signal to wirelessly transmit MI downlink signals to the wireless devices, and / or- wirelessly receive MI uplink signals from the wireless devices to generate an uplink electrical signal representing the MI uplink signals, wherein the antenna cable forms a MI loop antenna with a selected antenna pattern that corresponds to locations of the accommodation sites, wherein the MI loop antenna includes:- a main conductive loop around a plurality of the accommodation sites, and- at least one conductive sub-loop within, or forming a portion of, the main conductive loop, and arranged around at least one selected sub-set of the accommodation sites, such that the antenna pattern is enhanced, relative to the main conductive loop, by the or each conductive sub-loop at the selected sub-set of the accommodation sites.

2. The antenna system according to claim 1, wherein the or each sub-loop includes one or more closed sub-loops that each loops around one or more of the selected sub-set of the accommodation sites.

3. The antenna system according to claim 2, wherein a selected one of the one or more closed sub-loops completely surrounds a perimeter of a selected one of the selected sub-set of the accommodation sites4. The antenna system according to claim 3, wherein a selected one of the one or more closed sub-loops comprises a full turn or a plurality of full turns adjacent to and surrounding the selected one of the selected sub-set of the accommodation sites.

5. The antenna system according to claim 4, wherein the selected one of the one or more closed sub-loops further comprises a fractional turn adjacent to and surrounding the selected one of the selected sub-set of the accommodation sites.- 47 -6. The antenna system according to any one of claims 2 to 5, wherein a selected one of the one or more closed sub-loops loops around only a selected one of the selected sub-set of the accommodation sites.

7. The antenna system according to one of the preceding claims, wherein the or each subloop includes one or more open sub-loops that each loops between ones of the accommodation sites.

8. The antenna system according to claim 7, wherein a selected one of the one or more open sub-loops includes a side arranged between one or more of the selected sub-set of the accommodation sites inside the open sub-loop and one or more of the accommodation sites outside the open sub-loop.

9. The antenna system according to claim 7 or 8, wherein the one or more open sub-loops include a plurality of the open sub-loops arranged mutually adjacently to form a serpentine shape with the corresponding sub-sets of the accommodation sites being mutually adjacent.

10. The antenna system according to any one of the preceding claims, wherein the at least one sub-loop includes a plurality of the sub-loops around a respective plurality of sub-sets of the accommodation sites.

11. The antenna system according to claim 10, wherein a first sub-loop, of the plurality of the sub-loops, is arranged to provide higher magnetic flux density and Ml sensitivity than a second sub-loop of the plurality of the sub-loops.

12. The antenna system according to any one of the preceding claims, wherein the or each conductive sub-loop is selected to be arranged symmetrically around the or each accommodation site in the respective sub-set of the accommodation sites such that the or each accommodation site is substantially in a middle of current carrying elements of the or each conductive sub-loop for that accommodation site.

13. The antenna system according to any one of the preceding claims, wherein the or each conductive sub-loop is selected to have a mutual spacing between its current conducting elements on opposed sides of the or each accommodation site in the respective sub-set of the accommodation sites, wherein the mutual spacing is based on a determined depth of the respective accommodation site and a predefined relationship between magnetic strength, the depth and the mutual spacing.- 48 -14. The antenna system according to any one of the preceding claims, wherein the antenna cable includes two terminals, the antenna cable and the two terminals being arranged to form the main loop including the at least one sub-loop between the two terminals.

15. The antenna system according to any one of the preceding claims, further comprising: an electronic signal transmission arrangement adapted to emit and transmit the first electrical signal to the antenna cable; and / oran electronic signal receiving arrangement adapted to detect and receive the uplink electrical signal from the antenna cable.

16. The antenna system according to claim 15,wherein the signal transmission arrangement comprises a first transformer arrangement adapted to receive and convert a second electrical signal emitted by a signal generator into the first electrical signal, particularly the transformer arrangement being adapted to step down a voltage of the second electrical signal and thereby convert the second electrical signal into the first electrical signal,and / or wherein the signal generator comprises a current generator and a second transformer arrangement, the current generator being adapted to generate a source electrical signal and the second transformer arrangement being adapted to receive the source electrical signal, step up a voltage of the source electrical signal, and thereby convert the source electrical signal into the second electrical signal.

17. The antenna system according to claim 16,wherein:the first transformer arrangement is connected to a base coil to receive the second electrical signal,the base coil is adapted to be inductively coupled with a source loop antenna connected to a current generator,the current generator is adapted to generate and transmit a source electrical signal to the source loop antenna,the base coil is adapted to provide the second electrical signal induced by the source electrical signal in the source loop antenna, andthe base coil is adapted to step up a voltage of the source electrical signal and thereby convert the source electrical signal into the second electrical signal,and / or wherein:an extension cable adapted to receive the second electrical signal from a signal generator and transmit the second electrical signal to the first transformer arrangement, the- 49 -extension cable being a high voltage rated electrical cable adapted for high power transmission,and / or wherein:a tuning circuit is connected between one of two terminals of the antenna cable and an output of the first transformer arrangement.

18. A method of deploying a magnetic induction (MI) antenna system in one or more signalling areas, the one or more signalling areas each including a plurality of accommodation sites, the plurality of accommodation sites being adapted for receiving respective wireless devices, wherein the method comprises:- arranging an antenna cable to:- receive a first electrical signal from a signal transmission arrangement to generate MI downlink signals, and / or- provide an uplink electrical signal to an electronic signal receiver arrangement adapted to receive the uplink electrical signal representing currents induced by MI uplink signals in the antenna cable, and- arranging the antenna cable to extend from the signal transmission arrangement and / or the signal receiver arrangement into the one or more signalling areas and to serve as an MI loop antenna to wirelessly transmit the MI downlink signals to, and / or to wirelessly receive the MI uplinks signals from, the wireless devices, wherein the antenna cable is arranged to form:a main conductive loop around a plurality of the accommodation sites; and at least one conductive sub-loop within, or forming a portion of, the main conductive loop, and arranged around at least one selected sub-set of the accommodation sites, such that the antenna pattern is enhanced, relative to the main conductive loop, by the or each conductive sub-loop at the selected sub-set of the accommodation sites

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