CA2168138A1 - Low frequency electromagnetic communication system, and antenna therefor - Google Patents
Low frequency electromagnetic communication system, and antenna thereforInfo
- Publication number
- CA2168138A1 CA2168138A1 CA 2168138 CA2168138A CA2168138A1 CA 2168138 A1 CA2168138 A1 CA 2168138A1 CA 2168138 CA2168138 CA 2168138 CA 2168138 A CA2168138 A CA 2168138A CA 2168138 A1 CA2168138 A1 CA 2168138A1
- Authority
- CA
- Canada
- Prior art keywords
- antenna
- loops
- low frequency
- receiver
- conductor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/04—Adaptation for subterranean or subaqueous use
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q7/00—Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
Landscapes
- Near-Field Transmission Systems (AREA)
- Support Of Aerials (AREA)
Abstract
An antenna apparatus for use in association with low frequency electro magnetic wave systems, the antenna having an antenna casing, a plurality of separate loops of electrical conductors wound within the casing the loops being formed of a single antenna conductor whereby in any one loop the conductor defines a continuous conductor loop, each of the loops being electrically unconnected with adjacent loops, so as to define a plurality of a separate antenna loops within the antenna casing, signal connections electrically connected to respective antenna loops for connection to a single signal processing means for processing low frequency electro magnetic pulses.
Also disclosed is a low frequency wave radiating and or receiving system utilising an antenna of the type described.
Also disclosed is a low frequency wave radiating and or receiving system utilising an antenna of the type described.
Description
-FIELD OF THE INVENTION
The invention relates to a communication system using low frequency oscillating electromagnetic fields, and in particular, to such a system having a compact antenna having a high degree of efficiency with such low frequency oscillating fields.
BACKGROUND OF THE INVENTION
Low frequency electromagnetic fields are of great interest for communication in view of certain characteristics. They have the ability to penetrate substantial distances into the body of the earth, both through various geological strata including rock overburden, and even water. Such low frequency electromagnetic fields can penetrate to a depth of five to ten thousand feet (two to three kilometres) or more and can carry message information encoded in various ways.
Such low frequency electromagnetic fields can also be used for communicating through massive man-made structures, such as large buildings, industrial and commercial installations, factories full of heavy equipment and the like.
However, in the past, commercial developments in low frequency electromagnetic fields have been held back, by various problems including the designing a satisfactory antenna. Generally speaking, the propagation, and/or reception, of low frequency electromagnetic fields has been based on the design of an antenna consisting of several loops of wire, arranged in a more or less circular manner, in which the circle had a very substantial diameter.
This had led to various problems. In the first place the cost of such systems was high compared with the benefits produced. In addition, it is not always practicable to lay out an antenna where the diameter of the antenna was many hundreds or thousands of feet.
One particular application where it is desirable to employ low frequency electromagnetic transmissions, is in the mining industry. Miners work at various different levels many thousands of feet below the ground. Radio transmissions to such miners have not proved to be practicable. Other forms of signalling systems have generally been proposed in the past which depended upon wired systems, with flashing lights or other localized devices. These systems have been liable to failure due to breakage of wires and the like. In particular, the problem arises in an acute form, in the delivery of an emergency evacuation warning to miners. If during the course of a shift an emergency arises and it is desirable to evacuate the men from the mine, it is desirable to communicate with all the men simultaneously. A delay of even a few minutes may result in some men being trapped. Notwithstanding this however most mines rely on a warning system which consists of introducing a foul smelling gas into the air ventilation system in the mine, in order to warn the miners of the need for immediate evacuation. Such systems are highly erratic in their operation. In some larger mines, it may take up to an hour before the odour of the warning gas reaches miners in more remote locations. Such a delay is far too long to give the men a chance to evacuate before the emergency develops. It is clearly highly desirable to provide a communication system which can provide at least a warning signal to all miners in a particular mine site simultaneously and promptly without the delays of such gas systems.
In addition to this however there is a problem, common to many industries, not merely the mining industry, of rapidly locating and paging specialized service personnel.
For example, if a piece of equipment such as electrical hydraulic or mechanical equipment in a mine requires the attention of a specialized service person, and if such service person is located elsewhere in the mine, it may be several hours before he can be located and paged, and brought to the location of the piece of equipment requiring servicing. At present, there are essentially no systems for locating and paging such service personnel when they are in the mine other than hard wired systems depending upon signalling devices such as flashing lights, buzzers or the like.
216~138 It will of course be appreciated that this explanation of problems in the particular case of the mining industry are merely examples of typical problems of communication, where geology, or man-made structures, impose substantial obstacles to the propagation of conventional radio wave communication.
In the particular case of communication with mining personnel underground, it has been proposed to utilize a low frequency system having an antenna which is laid out on the earth's surface, in the region over the mine site. Such a system is in fact available from Mine Site Technologies Inc.
of Australia, but this system has significant disadvantages.
In the first place, the antenna used for propagating the ultra low frequency electro magnetic fields over a mine site, is typically in the order of one kilometre in diameter. This involves a very substantial expense both in clearing the area over the mine site and then also constructing and laying out the antenna. In addition however, the system is relatively inefficient, in that it can penetrate only up to a depth of about one kilometre.
Furthermore the system requires considerable power consumption, and is not suitable for carrying encoded information so as to use as a paging system for specific individuals.
One additional unforseen problem in these systems is the fact that the penetration of the electro magnetic fields varies considerably depending upon whether the geology, particularly the surface overburden, is wet or dry. In dry conditions penetration is relatively satisfactory. However, after extensive rains, when the surface overburden becomes laden with water, the depth of penetration decreases significantly. Consequently, weather conditions can influence the effectiveness of the system.
The greater the diameter of the loop the greater it is affected by the geology and the environment. The impedance of a large loop will be driven up dramatically when high moisture leading to high soil conductivity conditions occur.
These factors lead to a low Q factor and low efficiency.
In order to overcome this it is necessary to provide for a substantial increase of power output, to increase the power of the electro magnetic fields during wet weather and this in turn greatly increases the cost of the system.
Different considerations arise when attempting to use such low frequency electromagnetic oscillations for communicating information both to an individual, and for receiving information from that individual. Clearly, a stationary fixed transmission system located at a fixed point can be provided with a relatively considerable power input for radiating over a substantial area.
However, when it is considered that it may be desirable to provide for individual persons to carry transmitters which can be used for replying to such communication, it will be appreciated that there are very severe limitations on the size of the equipment and of the power supply that can be designed into it. However, the desirability of providing for such two-way communication, through heavy overburden or through massive building structures or in large factories or commercial institutions, or through water, makes it highly desirable that some form of two-way communication system can be provided.
According to the present invention it has been found that for the purpose of transmitting and or receiving a low frequency signal, the use of smaller diameter multiple driven separate coils which are wound in the same direction and series resonated with consideration to the mutual inductance between them, creates an extreme advantage over the standard methods in use today.
The Q factor is determined by the bandwidth of the antenna, that is, the width of the communication channel.
The bandwidth is generally considered to include a group of frequencies with a response to 70.7% of maximum. The Q of a series resonant circuit is directly proportional to the resonant frequency and inversely proportional to the bandwidth. The Q is also directly proportional to the inductive reactance and inversely proportional to the resistance of the inductive circuit. The factor h is generally known as the "effective height" of the antenna.
The factor Qh is a figure of merit for an inductor antenna and may be viewed as a function of the efficiency.
The low Q and Qh factors for large loop inductor antenna systems dictate that a large amount of power is required to transmit signals through solid or liquid mediums. The amount of voltage in a large loop also dictates the need of high voltage ratings on the insulation for the wire forming the loop as well as the high cost in insuring safety for any one in close contact to the loop.
A large loop ranging from 100 metres to 1 kilometre in diameter seldom achieves a transmitted signal distance of more than a few kilometres.
BRIEF SUMMARY OF THE INVENTION
With a view to overcoming the foregoing conflicting disadvantages, the invention comprises a low frequency A.C.
electromagnetic communication system, the antenna apparatus in turn comprising an insulated antenna casing, a plurality of antenna loops formed of electrical conductors within said casing extending therealong side by side, said loops each comprising a single continuous conductor wound several times to comprise separate single antenna loops, said conductors of a said loop being electrically unconnected with adjacent said loops of conductors, whereby to define a plurality of separate looped antennas within said antenna casing, a plurality of signal amplifiers equal in number to said plurality of looped antennas , respective said amplifiers being electrically connected to respective said antenna loops, said amplifiers being adapted to be connected to a single signal processing means for processing low frequency electric sine wave currents.
The invention is applicable both to transmitters and to receivers.
The invention provides such a system wherein encoding circuits are connected to a signal generator, for encoding signals on the low frequency currents.
Another feature of the invention is the provision of one or more sub-transmission stations spaced about within a location, operable to transmit low frequency electromagnetic signals with coded information back to a main receiver.
Also the invention provides individual receiver/
transmitter units for use by individual personnel or adapted to be placed at various locations, which are adapted to receive signals from the main transmitter, and which are operable to transmit signals to one of the sub-transmission stations nearest to the individual receiver/transmitter for re-transmission to the main receiver.
The system also provides for passive tags which can be attached to a large number of articles such as for example, pieces of luggage, cattle, or pigs, or a wide variety of other items, which tags carry unique encoded information, and can be activated by a transmitter/receiver, so as to 216~138 emit unique individual signals which can be detected by the transmitter/receiver.
The various features of novelty which characterize the invention are pointed out with more particularity in the claims annexed to and forming a part of this disclosure.
For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated and described preferred embodiments of the invention.
IN THE DRAWINGS
Figure 1 is a perspective illustration of an antenna apparatus illustrating the invention, with portions cut away therefrom;
Figure 2 is an exploded perspective illustration showing four separate antenna windings and their four separate amplifiers, it being understood that an antenna according to the invention may comprise four, or even more,such antenna windings and respective amplifiers;
Figure 3 is a perspective illustration of one such antenna winding of a group of such windings, showing the single conductor of which such a winding is formed;
Figure 4 is a schematic side elevation showing a mine site with a transmitter antenna and a receiver antenna on the surface and showing individual receiver transmitters and re-transmission sub-stations at various underground locations;
Figure 5 is a perspective of a personally portable transceiver, and, Figure 6 is a schematic perspective of a receiving antenna.
DESCRIPTION OF A SPECIFIC EMBODIMENT
As already mentioned above, the invention, of which Figure 1 is merely one embodiment, may be used in a wide variety of situations for transmitting , and receiving,signals through geological strata, or within massive buildings, factories, or the like, or for example, through water, where it is not possible to propagate or to receive conventional radio frequency transmissions.
As already noted, information can be encoded on the electro magnetic radiations in accordance with the invention, in such a way as to provide useful information for transmission through and reception in media where it would be impossible to transmit or receive using conventional radio transmission systems .
The system illustrating this embodiment of the invention will be seen to comprise an antenna ring 10, and a signal generator 12. Typically the antenna ring 10 is adapted to be laid out on the ground,although the illustration can also be regarded as an illustration of an 21681~8 antenna which is mounted on a vehicle such as a truck, ship or the like, or which is mounted in or around a building .
Referring now to Figures 2 and 3, the antenna 10 of Figure 1 will be seen to comprise, in this illustration which is given here for the purposes of explanation only, a plurality of antenna loops 14,16,18,and 20. Each loop is formed separately from each other (Fig 3). Each loop consists of a continuous conductor 14a, 16a, etc,wound into several turns or windings and having two ends. The conductors are insulated and separate from one another, but are all contained in a single outer insulated casing 22.
While the illustration shows four separate loops, it will be appreciated that this number is selected solely for the purposes of illustration and a greater , or lesser, number of such loops may be used in various circumstances.
Each of the loops 14 etc is connected to its own respective amplifier 24,26,28,and 30. All of the amplifiers are connected to a single signal generator 12, so that all of the amplifiers receive the same low frequency wave forms generated by the signal generator. All of the antenna loops will thus be subjected to the same sine wave signal and all of the loops radiate such signals simultaneously. The amplifiers are each connected to respective condensers 32,34,36,and 38.
The features of the invention herein give advantages over the large loop technology in use today. The ULF
216~138 transmitter inductor can be versatile in size and range from just a few centimetres to possibly 50 metres in diameter.
The inductor/antenna is constructed from several individual inductors directly wound together and series resonated as separate circuits taking in account the mutual inductance between them. Each separate winding is designed for optimum Q with as many effective turns as required to result in high inductance at low resistance. Using this method at carrier frequencies of 2000 to 3000 Hertz with inductors as small as lo 20 to 25 centimetres in diameter transmission distances of 2 kilometres and greater can be met. The Q of the individual wound inductors can easily meet 50 or greater whereas with the larger inductors Q's of 2 or 3 are very common.
The factor Qh can be viewed as a function of efficiency of the antenna, that is, the larger the Qh factor, the greater is the energy radiated by the antenna within the desired bandwidth of the carrier frequency for a fixed amount of electrical energy supplied to the antenna.
The multiple separate winding technique allows the driving of each individual loop separately at low wattage.
The system can be powered with a 12 volt storage battery which is also important for portable use, or can even be solar power in remote applications.
The factors to consider when making an inductor are;
-the diameter of the loops, the length of the conductors, the number of turns in each loop, and the radial depth of the winding.
The value of inductance (L) is measured in Henry, named after the American Physicist Joseph Henry. The single most important thing we can measure about an inductor is the strength of the magnetic field. However, the strength of the field is greatly influenced by conditions surrounding the inductor. The inductance of a coil is one Henry when a current variation of 1 ampere per second induces 1 volt of electrical opposition to the current flow.
There are conditions other than the applied voltage that can affect the strength of the magnetic field. An increase in the magnetic field without increasing the applied voltage can be achieved by adding more turns and increasing the diameter of the coil. This is correct in theory. However, this will also increase the influence of the core and raise the resistance of the coil and thus lower the Q of the inductor. Again in theory, the permeability of the core could be increased by the addition of high permeability iron or ferrite to the core. However, this is not practical due mostly to cost.
In the present invention, with reference to ~igures 2 and 3 , multiple coils eg 14a ,16a etc. are wound in the same direction at the chosen diameter to produce the optimum inductance for the largest possible diameter at the lowest resistance. Typically, the aim is to achieve 20 to 30 millihenry at a resistance of less than 20 ohms for a diameter of 10 to 15 metres. Smaller portable loops can easily achieve 25 to 30 millihenry at a resistance of less than 10 ohms for a diameter of 1 metre or less. The diameter of the conductor is also a contributing factor however, and consideration for eddy currents can be accomplished by multiple parallel conductors forming the effect of Litz wire.
As generally shown in Figure 4 a transmitter system may comprise an antenna ring 10, a signal generator 12, which will incorporate encoding circuits (indicated generally as 40) for modulating encoded information onto the low frequency sine wave signal generated by the signal generator. This system will be capable of generating and radiating signals which will penetrate for example two or more kilometers of overburden, or rock, carrying with it encoded information. As described Figure 4 is intended as an illustration of a mine, and as such has a main access shaft 42, and a series of more or less horizontal or gently sloping side shafts called "stopes" 44. Individual miners or service personnel, or specialised pieces of equipment, represented as 46 may be located at widely varying locations within the mine. In accordance with the invention each such individual (or piece of equipment), will carry a personally portable receiver or transceiver 48 (Fig 5).
21681~8 Alternatively such transceiver units may be placed at strategic locations pieces of around and within the mine.
Also located at spaced points within the mine ,in this illustration, there are one or more re-transmitter units 50.
These will typically have a greater range than the individual units 48.
If a message is transmitted by the antenna 10 it will be received by the designated individual indicated as 46 in his personal receiver 48, or by all individuals in some cases.
If the message requires a reply, that individual can send the reply by means of transceiver 48. That reply signal will be received by the re-transmitter unit 50 which will then resend the reply at a sufficient power output to reach the surface.
At the surface a receiver antenna 52 is located of a design generally similar to antenna 10 with certain modifications (see Fig 6). Antenna 52 is connected to a suitable receiver unit 54 thus completing the transmission and reception of the message and the reply.
The personal receiver/transmitter 48 (Fig 5) will be somewhat like a pager, in design. It will have a housing 56, typically rectangular in shape and a clip 58 by means of which it may by secured to the person,or to a piece of equipment. It may have a visual signal such as the light 60, and also a speaker 62, (which may also incorporate microphone) in known manner.
Referring to Figure 6, a receiver antenna 52 will have loops 64-64 similar to the loops in the transmitter antenna.
However an amplifier 66 is provided for each loop ,to amplify the signal received in the antenna for communication to the receiver. A capacitor 68 is connected across the output and return of each loop.
The foregoing is a description of a preferred embodiment of the invention which is given here by way of example only. The invention is not to be taken as limited to any of the specific features as described, but comprehends all such variations thereof as come within the scope of the appended claims.
The invention relates to a communication system using low frequency oscillating electromagnetic fields, and in particular, to such a system having a compact antenna having a high degree of efficiency with such low frequency oscillating fields.
BACKGROUND OF THE INVENTION
Low frequency electromagnetic fields are of great interest for communication in view of certain characteristics. They have the ability to penetrate substantial distances into the body of the earth, both through various geological strata including rock overburden, and even water. Such low frequency electromagnetic fields can penetrate to a depth of five to ten thousand feet (two to three kilometres) or more and can carry message information encoded in various ways.
Such low frequency electromagnetic fields can also be used for communicating through massive man-made structures, such as large buildings, industrial and commercial installations, factories full of heavy equipment and the like.
However, in the past, commercial developments in low frequency electromagnetic fields have been held back, by various problems including the designing a satisfactory antenna. Generally speaking, the propagation, and/or reception, of low frequency electromagnetic fields has been based on the design of an antenna consisting of several loops of wire, arranged in a more or less circular manner, in which the circle had a very substantial diameter.
This had led to various problems. In the first place the cost of such systems was high compared with the benefits produced. In addition, it is not always practicable to lay out an antenna where the diameter of the antenna was many hundreds or thousands of feet.
One particular application where it is desirable to employ low frequency electromagnetic transmissions, is in the mining industry. Miners work at various different levels many thousands of feet below the ground. Radio transmissions to such miners have not proved to be practicable. Other forms of signalling systems have generally been proposed in the past which depended upon wired systems, with flashing lights or other localized devices. These systems have been liable to failure due to breakage of wires and the like. In particular, the problem arises in an acute form, in the delivery of an emergency evacuation warning to miners. If during the course of a shift an emergency arises and it is desirable to evacuate the men from the mine, it is desirable to communicate with all the men simultaneously. A delay of even a few minutes may result in some men being trapped. Notwithstanding this however most mines rely on a warning system which consists of introducing a foul smelling gas into the air ventilation system in the mine, in order to warn the miners of the need for immediate evacuation. Such systems are highly erratic in their operation. In some larger mines, it may take up to an hour before the odour of the warning gas reaches miners in more remote locations. Such a delay is far too long to give the men a chance to evacuate before the emergency develops. It is clearly highly desirable to provide a communication system which can provide at least a warning signal to all miners in a particular mine site simultaneously and promptly without the delays of such gas systems.
In addition to this however there is a problem, common to many industries, not merely the mining industry, of rapidly locating and paging specialized service personnel.
For example, if a piece of equipment such as electrical hydraulic or mechanical equipment in a mine requires the attention of a specialized service person, and if such service person is located elsewhere in the mine, it may be several hours before he can be located and paged, and brought to the location of the piece of equipment requiring servicing. At present, there are essentially no systems for locating and paging such service personnel when they are in the mine other than hard wired systems depending upon signalling devices such as flashing lights, buzzers or the like.
216~138 It will of course be appreciated that this explanation of problems in the particular case of the mining industry are merely examples of typical problems of communication, where geology, or man-made structures, impose substantial obstacles to the propagation of conventional radio wave communication.
In the particular case of communication with mining personnel underground, it has been proposed to utilize a low frequency system having an antenna which is laid out on the earth's surface, in the region over the mine site. Such a system is in fact available from Mine Site Technologies Inc.
of Australia, but this system has significant disadvantages.
In the first place, the antenna used for propagating the ultra low frequency electro magnetic fields over a mine site, is typically in the order of one kilometre in diameter. This involves a very substantial expense both in clearing the area over the mine site and then also constructing and laying out the antenna. In addition however, the system is relatively inefficient, in that it can penetrate only up to a depth of about one kilometre.
Furthermore the system requires considerable power consumption, and is not suitable for carrying encoded information so as to use as a paging system for specific individuals.
One additional unforseen problem in these systems is the fact that the penetration of the electro magnetic fields varies considerably depending upon whether the geology, particularly the surface overburden, is wet or dry. In dry conditions penetration is relatively satisfactory. However, after extensive rains, when the surface overburden becomes laden with water, the depth of penetration decreases significantly. Consequently, weather conditions can influence the effectiveness of the system.
The greater the diameter of the loop the greater it is affected by the geology and the environment. The impedance of a large loop will be driven up dramatically when high moisture leading to high soil conductivity conditions occur.
These factors lead to a low Q factor and low efficiency.
In order to overcome this it is necessary to provide for a substantial increase of power output, to increase the power of the electro magnetic fields during wet weather and this in turn greatly increases the cost of the system.
Different considerations arise when attempting to use such low frequency electromagnetic oscillations for communicating information both to an individual, and for receiving information from that individual. Clearly, a stationary fixed transmission system located at a fixed point can be provided with a relatively considerable power input for radiating over a substantial area.
However, when it is considered that it may be desirable to provide for individual persons to carry transmitters which can be used for replying to such communication, it will be appreciated that there are very severe limitations on the size of the equipment and of the power supply that can be designed into it. However, the desirability of providing for such two-way communication, through heavy overburden or through massive building structures or in large factories or commercial institutions, or through water, makes it highly desirable that some form of two-way communication system can be provided.
According to the present invention it has been found that for the purpose of transmitting and or receiving a low frequency signal, the use of smaller diameter multiple driven separate coils which are wound in the same direction and series resonated with consideration to the mutual inductance between them, creates an extreme advantage over the standard methods in use today.
The Q factor is determined by the bandwidth of the antenna, that is, the width of the communication channel.
The bandwidth is generally considered to include a group of frequencies with a response to 70.7% of maximum. The Q of a series resonant circuit is directly proportional to the resonant frequency and inversely proportional to the bandwidth. The Q is also directly proportional to the inductive reactance and inversely proportional to the resistance of the inductive circuit. The factor h is generally known as the "effective height" of the antenna.
The factor Qh is a figure of merit for an inductor antenna and may be viewed as a function of the efficiency.
The low Q and Qh factors for large loop inductor antenna systems dictate that a large amount of power is required to transmit signals through solid or liquid mediums. The amount of voltage in a large loop also dictates the need of high voltage ratings on the insulation for the wire forming the loop as well as the high cost in insuring safety for any one in close contact to the loop.
A large loop ranging from 100 metres to 1 kilometre in diameter seldom achieves a transmitted signal distance of more than a few kilometres.
BRIEF SUMMARY OF THE INVENTION
With a view to overcoming the foregoing conflicting disadvantages, the invention comprises a low frequency A.C.
electromagnetic communication system, the antenna apparatus in turn comprising an insulated antenna casing, a plurality of antenna loops formed of electrical conductors within said casing extending therealong side by side, said loops each comprising a single continuous conductor wound several times to comprise separate single antenna loops, said conductors of a said loop being electrically unconnected with adjacent said loops of conductors, whereby to define a plurality of separate looped antennas within said antenna casing, a plurality of signal amplifiers equal in number to said plurality of looped antennas , respective said amplifiers being electrically connected to respective said antenna loops, said amplifiers being adapted to be connected to a single signal processing means for processing low frequency electric sine wave currents.
The invention is applicable both to transmitters and to receivers.
The invention provides such a system wherein encoding circuits are connected to a signal generator, for encoding signals on the low frequency currents.
Another feature of the invention is the provision of one or more sub-transmission stations spaced about within a location, operable to transmit low frequency electromagnetic signals with coded information back to a main receiver.
Also the invention provides individual receiver/
transmitter units for use by individual personnel or adapted to be placed at various locations, which are adapted to receive signals from the main transmitter, and which are operable to transmit signals to one of the sub-transmission stations nearest to the individual receiver/transmitter for re-transmission to the main receiver.
The system also provides for passive tags which can be attached to a large number of articles such as for example, pieces of luggage, cattle, or pigs, or a wide variety of other items, which tags carry unique encoded information, and can be activated by a transmitter/receiver, so as to 216~138 emit unique individual signals which can be detected by the transmitter/receiver.
The various features of novelty which characterize the invention are pointed out with more particularity in the claims annexed to and forming a part of this disclosure.
For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated and described preferred embodiments of the invention.
IN THE DRAWINGS
Figure 1 is a perspective illustration of an antenna apparatus illustrating the invention, with portions cut away therefrom;
Figure 2 is an exploded perspective illustration showing four separate antenna windings and their four separate amplifiers, it being understood that an antenna according to the invention may comprise four, or even more,such antenna windings and respective amplifiers;
Figure 3 is a perspective illustration of one such antenna winding of a group of such windings, showing the single conductor of which such a winding is formed;
Figure 4 is a schematic side elevation showing a mine site with a transmitter antenna and a receiver antenna on the surface and showing individual receiver transmitters and re-transmission sub-stations at various underground locations;
Figure 5 is a perspective of a personally portable transceiver, and, Figure 6 is a schematic perspective of a receiving antenna.
DESCRIPTION OF A SPECIFIC EMBODIMENT
As already mentioned above, the invention, of which Figure 1 is merely one embodiment, may be used in a wide variety of situations for transmitting , and receiving,signals through geological strata, or within massive buildings, factories, or the like, or for example, through water, where it is not possible to propagate or to receive conventional radio frequency transmissions.
As already noted, information can be encoded on the electro magnetic radiations in accordance with the invention, in such a way as to provide useful information for transmission through and reception in media where it would be impossible to transmit or receive using conventional radio transmission systems .
The system illustrating this embodiment of the invention will be seen to comprise an antenna ring 10, and a signal generator 12. Typically the antenna ring 10 is adapted to be laid out on the ground,although the illustration can also be regarded as an illustration of an 21681~8 antenna which is mounted on a vehicle such as a truck, ship or the like, or which is mounted in or around a building .
Referring now to Figures 2 and 3, the antenna 10 of Figure 1 will be seen to comprise, in this illustration which is given here for the purposes of explanation only, a plurality of antenna loops 14,16,18,and 20. Each loop is formed separately from each other (Fig 3). Each loop consists of a continuous conductor 14a, 16a, etc,wound into several turns or windings and having two ends. The conductors are insulated and separate from one another, but are all contained in a single outer insulated casing 22.
While the illustration shows four separate loops, it will be appreciated that this number is selected solely for the purposes of illustration and a greater , or lesser, number of such loops may be used in various circumstances.
Each of the loops 14 etc is connected to its own respective amplifier 24,26,28,and 30. All of the amplifiers are connected to a single signal generator 12, so that all of the amplifiers receive the same low frequency wave forms generated by the signal generator. All of the antenna loops will thus be subjected to the same sine wave signal and all of the loops radiate such signals simultaneously. The amplifiers are each connected to respective condensers 32,34,36,and 38.
The features of the invention herein give advantages over the large loop technology in use today. The ULF
216~138 transmitter inductor can be versatile in size and range from just a few centimetres to possibly 50 metres in diameter.
The inductor/antenna is constructed from several individual inductors directly wound together and series resonated as separate circuits taking in account the mutual inductance between them. Each separate winding is designed for optimum Q with as many effective turns as required to result in high inductance at low resistance. Using this method at carrier frequencies of 2000 to 3000 Hertz with inductors as small as lo 20 to 25 centimetres in diameter transmission distances of 2 kilometres and greater can be met. The Q of the individual wound inductors can easily meet 50 or greater whereas with the larger inductors Q's of 2 or 3 are very common.
The factor Qh can be viewed as a function of efficiency of the antenna, that is, the larger the Qh factor, the greater is the energy radiated by the antenna within the desired bandwidth of the carrier frequency for a fixed amount of electrical energy supplied to the antenna.
The multiple separate winding technique allows the driving of each individual loop separately at low wattage.
The system can be powered with a 12 volt storage battery which is also important for portable use, or can even be solar power in remote applications.
The factors to consider when making an inductor are;
-the diameter of the loops, the length of the conductors, the number of turns in each loop, and the radial depth of the winding.
The value of inductance (L) is measured in Henry, named after the American Physicist Joseph Henry. The single most important thing we can measure about an inductor is the strength of the magnetic field. However, the strength of the field is greatly influenced by conditions surrounding the inductor. The inductance of a coil is one Henry when a current variation of 1 ampere per second induces 1 volt of electrical opposition to the current flow.
There are conditions other than the applied voltage that can affect the strength of the magnetic field. An increase in the magnetic field without increasing the applied voltage can be achieved by adding more turns and increasing the diameter of the coil. This is correct in theory. However, this will also increase the influence of the core and raise the resistance of the coil and thus lower the Q of the inductor. Again in theory, the permeability of the core could be increased by the addition of high permeability iron or ferrite to the core. However, this is not practical due mostly to cost.
In the present invention, with reference to ~igures 2 and 3 , multiple coils eg 14a ,16a etc. are wound in the same direction at the chosen diameter to produce the optimum inductance for the largest possible diameter at the lowest resistance. Typically, the aim is to achieve 20 to 30 millihenry at a resistance of less than 20 ohms for a diameter of 10 to 15 metres. Smaller portable loops can easily achieve 25 to 30 millihenry at a resistance of less than 10 ohms for a diameter of 1 metre or less. The diameter of the conductor is also a contributing factor however, and consideration for eddy currents can be accomplished by multiple parallel conductors forming the effect of Litz wire.
As generally shown in Figure 4 a transmitter system may comprise an antenna ring 10, a signal generator 12, which will incorporate encoding circuits (indicated generally as 40) for modulating encoded information onto the low frequency sine wave signal generated by the signal generator. This system will be capable of generating and radiating signals which will penetrate for example two or more kilometers of overburden, or rock, carrying with it encoded information. As described Figure 4 is intended as an illustration of a mine, and as such has a main access shaft 42, and a series of more or less horizontal or gently sloping side shafts called "stopes" 44. Individual miners or service personnel, or specialised pieces of equipment, represented as 46 may be located at widely varying locations within the mine. In accordance with the invention each such individual (or piece of equipment), will carry a personally portable receiver or transceiver 48 (Fig 5).
21681~8 Alternatively such transceiver units may be placed at strategic locations pieces of around and within the mine.
Also located at spaced points within the mine ,in this illustration, there are one or more re-transmitter units 50.
These will typically have a greater range than the individual units 48.
If a message is transmitted by the antenna 10 it will be received by the designated individual indicated as 46 in his personal receiver 48, or by all individuals in some cases.
If the message requires a reply, that individual can send the reply by means of transceiver 48. That reply signal will be received by the re-transmitter unit 50 which will then resend the reply at a sufficient power output to reach the surface.
At the surface a receiver antenna 52 is located of a design generally similar to antenna 10 with certain modifications (see Fig 6). Antenna 52 is connected to a suitable receiver unit 54 thus completing the transmission and reception of the message and the reply.
The personal receiver/transmitter 48 (Fig 5) will be somewhat like a pager, in design. It will have a housing 56, typically rectangular in shape and a clip 58 by means of which it may by secured to the person,or to a piece of equipment. It may have a visual signal such as the light 60, and also a speaker 62, (which may also incorporate microphone) in known manner.
Referring to Figure 6, a receiver antenna 52 will have loops 64-64 similar to the loops in the transmitter antenna.
However an amplifier 66 is provided for each loop ,to amplify the signal received in the antenna for communication to the receiver. A capacitor 68 is connected across the output and return of each loop.
The foregoing is a description of a preferred embodiment of the invention which is given here by way of example only. The invention is not to be taken as limited to any of the specific features as described, but comprehends all such variations thereof as come within the scope of the appended claims.
Claims (23)
1. An antenna apparatus for use in association with low frequency electro magnetic wave systems, the antenna apparatus comprising;
an antenna casing;
a plurality of separate loops of electrical conductors wound within said casing said loops extending therewithin side by side, each of said loops being formed of a single antenna conductor whereby in any one said loop said conductor defines a continuous conductor loop, each of said loops being electrically unconnected with adjacent said loops, whereby to define a plurality of a separate antenna loops within said antenna casing;
a plurality of signal connection means equal in number to said plurality of loops, respective said connection means being electrically connected to respective said antenna loops said connection means being adapted to be connected to a single signal processing means.
an antenna casing;
a plurality of separate loops of electrical conductors wound within said casing said loops extending therewithin side by side, each of said loops being formed of a single antenna conductor whereby in any one said loop said conductor defines a continuous conductor loop, each of said loops being electrically unconnected with adjacent said loops, whereby to define a plurality of a separate antenna loops within said antenna casing;
a plurality of signal connection means equal in number to said plurality of loops, respective said connection means being electrically connected to respective said antenna loops said connection means being adapted to be connected to a single signal processing means.
2. An antenna apparatus as claimed in claim 1 wherein said signal processing apparatus is a low frequency signal generator for generating low frequency electrical pulses whereby said low frequency electro magnetic pulses will be simultaneously communicated to all said antenna loops and will be radiated around said plurality of antenna loops simultaneously.
3. An antenna apparatus as claimed in claim 2 and including a plurality of signal amplifiers there being one said amplifier connected to each said antenna loop and all said amplifiers being connectable to said signal generator whereby to receive said pulses therefrom simultaneously.
4. An antenna apparatus as claimed in claim 3 and including information encoding circuit means connected to said signal generator whereby information can be encoded onto said signal pulses for radiation by said antenna loops.
5. An antenna apparatus as claimed in claim 1 wherein each of said antenna loops comprises a plurality of windings of said conductor.
6.. An antenna apparatus as claimed in claim 5 wherein said antenna loops have a diameter of between about 20 and 25 centimetres,for carrier frequencies of about 2000 to 3000 Hertz.
7. An antenna apparatus as claimed in claim 5 wherein said loops have a diameter of between 10 to 15 metres and have an inductance of between 20 to 30 millihenries and a resistance of not more than about 20 ohms.
8. An antenna apparatus as claimed in claim 5 wherein said loops have a diameter of not more than about 1 metre and an inductance of between about 25 and 30 millihenries and a resistance of not more than about 10 ohms.
9. An antenna apparatus as claimed in claim 2 including a plurality of capacitors connected to respective loops, there being a said capacitor for each said loop.
10. An antenna apparatus as claimed in claim 1 wherein said signal processing means is a receiver circuit and wherein said antenna is a receiving antenna and including a capacitor and an amplifier connected in circuit between said antenna and said receiver circuit.
11. A low frequency wave radiating system for radiating low frequency waves through media unreceptive to radio waves and comprising;
a low frequency generator apparatus operable to generate low frequency waves, and, an antenna connected to said generator apparatus, said an antenna consisting of a plurality of separate loops of electrical conductors wound within casing means said loops extending therewithin side by side, each of said loops being formed of a single antenna conductor whereby in any one said loop said conductor defines a continuous conductor loop, each of said loops being electrically unconnected with adjacent said loops, whereby to define a plurality of a separate antenna loops within said antenna casing, said loops being electrically connected to said connected to said single generator for generating low frequency electro magnetic pulses, whereby said low frequency electro magnetic pulses will be simultaneously communicated to all said antenna loops and will be radiated around said plurality of antenna loops simultaneously.
a low frequency generator apparatus operable to generate low frequency waves, and, an antenna connected to said generator apparatus, said an antenna consisting of a plurality of separate loops of electrical conductors wound within casing means said loops extending therewithin side by side, each of said loops being formed of a single antenna conductor whereby in any one said loop said conductor defines a continuous conductor loop, each of said loops being electrically unconnected with adjacent said loops, whereby to define a plurality of a separate antenna loops within said antenna casing, said loops being electrically connected to said connected to said single generator for generating low frequency electro magnetic pulses, whereby said low frequency electro magnetic pulses will be simultaneously communicated to all said antenna loops and will be radiated around said plurality of antenna loops simultaneously.
12. A low frequency wave radiating system as claimed in claim 11 and including a plurality of signal amplifiers there being one said amplifier connected to each said antenna loop and all said amplifiers being connectable to said signal generator whereby to receive said pulses therefrom simultaneously.
13. A low frequency wave radiating system as claimed in claim 11 and including information encoding circuit means connected to said signal generator whereby information can be encoded onto said signal pulses for radiation by said antenna loops.
14. A low frequency wave radiating system as claimed in claim 11 wherein each of said antenna loops comprises a plurality of windings of said conductor.
15. A low frequency wave radiating system as claimed in claim 14 wherein said antenna loops have a diameter of between about 20 and 25 centimetres,for carrier frequencies of about 2000 to 3000 Hertz.
16. A low frequency wave radiating system as claimed in claim 14 wherein said loops have a diameter of between 10 to 15 metres and have an inductance of between 20 to 30 millihenries and a resistance of not more than about 20 ohms.
17. A low frequency wave radiating system as claimed in claim 14 wherein said loops have a diameter of not more than about 1 metre and an inductance of between about 25 and 30 millihenries and a resistance of not more than about 10 ohms.
18. A low frequency wave radiating system as claimed in claim 14 and including a receiver circuit means and a receiver antenna connected thereto said receiver antenna being of similar construction to said radiating antenna.
19. A low frequency wave radiating system as claimed in claim 18 and including at least one retransmission unit adapted to be located at a distance from said receiver antenna and at least one personal receiver and transmission unit adapted to be personally portable, said retransmission unit being adapted to receive signals from said personal unit, and to retransmit said signals to said receiver antenna.
20. A low frequency wave receiving system for receiving low frequency waves transmitted through media unreceptive to radio waves and comprising;
a low frequency receiver apparatus operable to receive low frequency waves, and, an antenna connected to said receiver apparatus, said an antenna consisting of a plurality of separate loops of electrical conductors wound within casing means said loops extending therewithin side by side, each of said loops being formed of a single antenna conductor whereby in any one said loop said conductor defines a continuous conductor loop, each of said loops being electrically unconnected with adjacent said loops, whereby to define a plurality of a separate antenna loops within said antenna casing, said loops being electrically connected to said connected to said single receiver for receiving low frequency electro magnetic pulses, whereby said low frequency electro magnetic pulses will be simultaneously communicated from all said antenna loops to said receiver simultaneously.
a low frequency receiver apparatus operable to receive low frequency waves, and, an antenna connected to said receiver apparatus, said an antenna consisting of a plurality of separate loops of electrical conductors wound within casing means said loops extending therewithin side by side, each of said loops being formed of a single antenna conductor whereby in any one said loop said conductor defines a continuous conductor loop, each of said loops being electrically unconnected with adjacent said loops, whereby to define a plurality of a separate antenna loops within said antenna casing, said loops being electrically connected to said connected to said single receiver for receiving low frequency electro magnetic pulses, whereby said low frequency electro magnetic pulses will be simultaneously communicated from all said antenna loops to said receiver simultaneously.
21. A low frequency wave receiving system as claimed in claim 20 and including a plurality of signal amplifiers there being one said amplifier connected to each said antenna loop and all said amplifiers being connectable to said signal receiver whereby said receiver will receive said pulses simultaneously from all said loops.
22. A low frequency wave receiving system as claimed in claim 21 wherein each of said antenna loops comprises a plurality of windings of said conductor.
23. A method of low frequency communication for communicating by means of low frequency waves through media unreceptive to radio waves and comprising the steps of;
generating low frequency waves by means of a low frequency generator apparatus ;
radiating said low frequency waves by means of a radiating antenna connected to said generator apparatus, said radiating antenna consisting of a plurality of separate loops of electrical conductors wound within casing means said loops extending therewithin side by side, each of said loops being formed of a single antenna conductor whereby in any one said loop said conductor defines a continuous conductor loop, each of said loops being electrically unconnected with adjacent said loops, whereby to define a plurality of a separate antenna loops within said antenna casing, said loops being electrically connected to said signal generator for generating low frequency electro magnetic waves whereby said low frequency electro magnetic waves will be simultaneously communicated to all said antenna loops and will be radiated around said plurality of antenna loops simultaneously;
receiving said low frequency waves by means of a receiver antenna connected to a receiver circuit said receiving antenna consisting of a plurality of separate loops of electrical conductors wound within casing means said loops extending therewithin side by side, each of said loops being formed of a single antenna conductor whereby in any one said loop said conductor defines a continuous conductor loop, each of said loops being electrically unconnected with adjacent said loops, whereby to define a plurality of a separate antenna loops within said antenna casing, said loops being electrically connected to said connected to said single receiver for processing low frequency electro magnetic pulses, whereby said low frequency electro magnetic waves will be simultaneously received by all said receiver antenna loops and will be communicated to said receiver circuit simultaneously.
generating low frequency waves by means of a low frequency generator apparatus ;
radiating said low frequency waves by means of a radiating antenna connected to said generator apparatus, said radiating antenna consisting of a plurality of separate loops of electrical conductors wound within casing means said loops extending therewithin side by side, each of said loops being formed of a single antenna conductor whereby in any one said loop said conductor defines a continuous conductor loop, each of said loops being electrically unconnected with adjacent said loops, whereby to define a plurality of a separate antenna loops within said antenna casing, said loops being electrically connected to said signal generator for generating low frequency electro magnetic waves whereby said low frequency electro magnetic waves will be simultaneously communicated to all said antenna loops and will be radiated around said plurality of antenna loops simultaneously;
receiving said low frequency waves by means of a receiver antenna connected to a receiver circuit said receiving antenna consisting of a plurality of separate loops of electrical conductors wound within casing means said loops extending therewithin side by side, each of said loops being formed of a single antenna conductor whereby in any one said loop said conductor defines a continuous conductor loop, each of said loops being electrically unconnected with adjacent said loops, whereby to define a plurality of a separate antenna loops within said antenna casing, said loops being electrically connected to said connected to said single receiver for processing low frequency electro magnetic pulses, whereby said low frequency electro magnetic waves will be simultaneously received by all said receiver antenna loops and will be communicated to said receiver circuit simultaneously.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2168138 CA2168138A1 (en) | 1996-01-26 | 1996-01-26 | Low frequency electromagnetic communication system, and antenna therefor |
| AU14338/97A AU1433897A (en) | 1996-01-26 | 1997-01-24 | Low frequency electromagnetic communication system and antenna therefor |
| PCT/CA1997/000054 WO1997027645A1 (en) | 1996-01-26 | 1997-01-24 | Low frequency electromagnetic communication system and antenna therefor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2168138 CA2168138A1 (en) | 1996-01-26 | 1996-01-26 | Low frequency electromagnetic communication system, and antenna therefor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2168138A1 true CA2168138A1 (en) | 1997-07-27 |
Family
ID=4157436
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2168138 Abandoned CA2168138A1 (en) | 1996-01-26 | 1996-01-26 | Low frequency electromagnetic communication system, and antenna therefor |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AU1433897A (en) |
| CA (1) | CA2168138A1 (en) |
| WO (1) | WO1997027645A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6813324B1 (en) | 1999-08-05 | 2004-11-02 | Mine Radio Systems Inc. | Synchronized communication system |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2806213B1 (en) * | 2000-03-07 | 2003-09-05 | Valeo Electronique | ANTENNA, VEHICLE COMMUNICATION SYSTEM, AND VEHICLE HAVING SUCH ANTENNA |
| US7778006B2 (en) | 2006-04-28 | 2010-08-17 | Orica Explosives Technology Pty Ltd. | Wireless electronic booster, and methods of blasting |
| GB0613081D0 (en) * | 2006-07-03 | 2006-08-09 | Wireless Fibre Systems Ltd | Underground data communications system |
| GB0724692D0 (en) * | 2007-12-19 | 2008-01-30 | Rhodes Mark | Antenna formed of multiple resonant loops |
| GB0724697D0 (en) * | 2007-12-19 | 2008-01-30 | Rhodes Mark | Antenna formed of multiple loops |
| US9519037B2 (en) | 2011-11-10 | 2016-12-13 | Mayo Foundation For Medical Education And Research | Spatially coincident MRI receiver coils and method for manufacturing |
| EP2781037B1 (en) * | 2011-11-17 | 2018-06-20 | Vital Alert Communication Inc. | Vlf transmit antenna system, method and apparatus |
| FR3056794B1 (en) * | 2016-09-23 | 2019-12-20 | Eliot Innovative Solutions | IDENTIFICATION SENSOR FOR LARGE DEPTH BURIALS |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57142002A (en) * | 1981-02-27 | 1982-09-02 | Toshiba Corp | Small-sized loop antenna |
| US4809010A (en) * | 1981-10-02 | 1989-02-28 | Canon Kabushiki Kaisha | Low profile wireless communication system and method |
| DE3823972A1 (en) * | 1988-07-15 | 1990-01-18 | Walter Dr Rer Nat Suedbeck | Magnetic radiating element having a coil made of bifilar turns |
| NO951225L (en) * | 1994-03-31 | 1995-10-02 | Halliburton Co | Sealed modular antenna for use in a wellbore |
-
1996
- 1996-01-26 CA CA 2168138 patent/CA2168138A1/en not_active Abandoned
-
1997
- 1997-01-24 AU AU14338/97A patent/AU1433897A/en not_active Abandoned
- 1997-01-24 WO PCT/CA1997/000054 patent/WO1997027645A1/en active Application Filing
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6813324B1 (en) | 1999-08-05 | 2004-11-02 | Mine Radio Systems Inc. | Synchronized communication system |
Also Published As
| Publication number | Publication date |
|---|---|
| AU1433897A (en) | 1997-08-20 |
| WO1997027645A1 (en) | 1997-07-31 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN1040365C (en) | Conductor locator adapter for electronic markers | |
| CN103283162B (en) | Portable Tou Di radio | |
| US8115622B2 (en) | Underground radio communications and personnel tracking system | |
| US4777652A (en) | Radio communication systems for underground mines | |
| US8542114B2 (en) | Cap-lamp and communications support system | |
| Murphy et al. | Underground mine communications | |
| WO2008003939A1 (en) | Underground data communications system | |
| WO2000033066A9 (en) | Apparatus and method for wireless gas monitoring | |
| CA2168138A1 (en) | Low frequency electromagnetic communication system, and antenna therefor | |
| AU602263B2 (en) | Mine emergency communication cable and method for use | |
| CN1012928B (en) | Medium frequency mine communication system | |
| EP0987401A2 (en) | Drill string telemetry | |
| CN102753996A (en) | Asset detection apparatus and method | |
| JP6471382B2 (en) | Magnetic wave antenna and magnetic wave communication apparatus using the same | |
| US3740488A (en) | Inductive loop through-the-earth communication system | |
| HU192119B (en) | Signalling apparatus under the earth level | |
| US20080009242A1 (en) | Underground data communications system | |
| US20090027287A1 (en) | Systems and methods for communications through materials | |
| RU2611603C1 (en) | Communication system of very low and extremely low frequency range with deep-seated and distant objects | |
| Bae et al. | Pulsed ferrite magnetic field generator for through-the-earth communication systems for disaster situation in mines | |
| CA1311527C (en) | Electromagnetic fire warning system for underground mines | |
| JP2022041722A (en) | Wireless communication system | |
| Ilsley et al. | Experiments in underground communication through earth strata | |
| RU2161846C1 (en) | Tunnel antenna | |
| Hjelmstad et al. | Ultra low frequency electromagnetic fire alarm system for underground mines |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |