HF ANTENNA ASSEMBLY
FIELD OF THE DISCLOSED TECHNIQUE
The disclosed technique generally relates to HF radio
communication, and more particularly, to a high gain antenna assembly
adapted for rapid deployment.
BACKGROUND OF THE DISCLOSED TECHNIQUE
The high frequency (HF) portion of the electromagnetic
spectrum includes radio frequencies in the range of approximately 2 to 30
MHz. The HF band is suitable for transmission of ground wave radio
signals for short distances (e.g., up to about 40km), as well as skywave
radio signals for longer distances. Near Vertical Incidence Skywave
(NVIS) involves the propagation of radio waves, which are refracted by the
ionosphere and return to the ground at a certain radius with respect to the
point of origin. The NVIS propagation is implemented at acute elevation
angles (e.g., 70°-90° relative to the horizontal), providing omni-directional
transmission for distances up to about 300km. Ionospheric refraction will
fail to occur beyond certain frequencies, and so NVIS propagation
operates best at the lower end of the HF band (e.g., approximately 2-1 2
MHz). These frequencies however are particularly susceptible to
atmospheric noise. The ionosphere is an atmospheric layer that is ionized
by solar radiation, and the refractive characteristics of the ionosphere
changes based on the time of day, season of the year, location of the sun,
and various additional factors which are constantly varying.
Assurance of reliable HF radio communication necessitates the
employment of suitable antennas. A whip antenna is a fairly prevalent
monopole antenna composed of a single straight vertical conductor
element that functions as a radiating element and is mounted atop a
conducting surface (ground plane). Whip antennas are commonly used
aboard a vehicle or on a portable handheld transceiver, as they do not
require extensive assembly or deployment operations for establishing a
communication link while the vehicle or portable transceiver is in motion.
Whip antennas are particularly suitable for providing ground wave radio
propagation, which requires a vertically polarized antenna configuration.
However, for NVIS propagation, a whip antenna provides very low gain
when radiating at high elevation angles. There is a practice of utilizing a
dipole antenna aboard vehicles or portable transceivers to enable NVIS
communication. However, the deployment of a dipole antenna typically
requires installing at least one mast for supporting the dipole wires. The
installation of masts is time consuming, and increases the overall weight
and cost of the antenna.
A narrow-band dipole antenna that is adapted for use at a
particular frequency features relatively high gain at high elevation angles,
but the dipole must be at least a certain length. For example, such a
dipole antenna operating at 2MHz has a length of approximately 74m,
which is impractical for use in many applications. Furthermore, the
efficiency of the Automatic Link Establishment (ALE) systems is drastically
reduced by limiting operation to a very narrow frequency band and
obligating the frequent changing of the dipole length. Efficient wide-band
dipole antennas generally require a large installation field (e.g., 50m in
length and 15m in width), resulting in considerable weight due to the
antenna mast and all the other necessary accessories.
U.S. Patent No. 4,21 7,591 to Czerwinski et al, entitled "High
frequency roll-bar loop antenna", is directed to a vehicular mounted
vertical loop HF communication antenna. The antenna includes a metallic
base horizontally positioned on the vehicle, and a vertically positioned
metallic loop element with one end affixed to the metallic base. The
antenna further includes a variable capacitor connected between the other
end of the metallic loop element and the metallic base, to form a closed
transmitting loop. The antenna further includes a coupling loop (e.g., of
coaxial cable) coplanar with the metallic loop element and slidably
mounted on the metallic base, where the area under the loop is adjustable
to maintain a desired input impedance at the antenna input terminal. The
antenna is adapted to provide NVIS operation over one HF frequency
range, and vertically polarized whip antenna operation over another higher
HF frequency range.
U.S. Patent No. 4,433,336 to Carr, entitled "Three-element
antenna formed of orthogonal loops mounted on a monopole", is directed
to an antenna which is electrically steerable in a transmitting mode and
which is capable of distinguishing the direction from which signals are
received without a mechanical rotator. The antenna includes two loop
antennas mounted on top of, and electrically coupled to, a vertically
oriented monopole antenna, where the respective axes are orthogonal to
one another. Each loop antenna includes an outer primary loop and a
smaller inner secondary loop disposed in the same plane as the primary
loop. The primary loops and secondary loops are interrupted at their top
ends opposite where they join the monopole antenna. A tuning capacitor
is coupled between the halves of the two primary loops, and coaxial
cables feed the two secondary loops. The antenna may selectively
radiate either omnidirectionally (via the monopole antenna) or directionally
(via the loop antennas).
U.S. Patent No. 5,252,985 to Christinsin, entitled "Whip tilt
adapter", is directed to an adapter that enables adjusting the polarization
of an HF radio whip antenna. The adapter includes a near-horizontal
member pivotally attached to a vertical shaft. The near-horizontal
member is held stationary with respect to the vertical shaft by securing
means, such as a pin that is inserted through matching sets of holes
through the member and shaft. The whip antenna is inserted into a
horizontal port at the distal end of the near-horizontal member. When the
member is oriented substantially horizontally, the antenna provides NVIS
operation utilizing reflective/refractive characteristics of the ionosphere
(e.g., at 2-1 4 MHz). When the near-horizontal member is oriented
vertically, the antenna provides for short-distance HF groundwave
communication. The member may also be oriented at various angles in
between a horizontal and vertical orientation. The adapter may be
installed on a mounting base on a vehicle.
U.S. Patent No. 6,91 7,339 to Li et al, entitled "Multi-band
broadband planar antennas", is directed to planar antenna with multi-band
and broadband functionalities applicable for compact antenna applications
(e.g., at around 2-5GHz). The antenna includes two inverted-L antennas
(ILAs) facing each other across a gap. One of the ILAs is input fed (e.g.,
directly by a coaxial cable input), and the other ILA is electromagnetically
coupled to the fed ILA. The vertical legs of the two ILAs are parallel and
substantially the same length, while the horizontal leg of the fed ILA is
shorter than the horizontal leg of the coupled ILA. The position of the gap
affects the bandwidth of the antenna. In one embodiment, a dual-band
antenna includes a monopole antenna disposed between the ILAs. The
monopole receives input fed and is connected to the input fed ILA near its
base. The monopole is designed for resonance at a higher frequency
than the ILAs.
U.S. Patent No. 7,839,344 to Marrocco et al, entitled "Wideband
multifunction antenna operating in the HF range, particularly for naval
installations", is directed to a wideband linear HF antenna designed
particularly for fixed installations onboard naval units for military
communications. The antenna includes a plurality of radiating elements
forming conducting branches arranged in a bifolded configuration (i.e., two
closed nested coplanar paths). The antenna further includes electrical
impedance elements disposed within the conducting branches, to
selectively impede current flow within selected frequency ranges to
establish current paths according to the operating frequency. The
antenna is adapted to provide uniform radiation at different angles of
elevation for the entire HF band. In particular: NVIS communication at the
lower HF range (2-4 MHz) and shorter distances (up to 150 km); sea wave
and ionospheric reflection communication at low HF frequencies (2-7
MHz) and slightly greater distances (up to 500 km); ionospheric reflection
communication at medium HF frequencies (6-1 5 MHz) and medium
distances ( 1 000-2000 km); and communication at low-medium angles of
elevation (5-30°) at higher HF frequencies ( 15-20 MHz).
Additional dual antenna arrangements which combine
monopoles and dipoles can be found in Japanese Patent Publication No.
5041 6 10(A) to Taniyoshi, entitled: "Antenna for mobile body"; Japanese
Patent Publication No. 521 0 1949(A) to Kawai et al, entitled: "Antenna
apparatus"; and Japanese Patent Publication No. 2002-1 00928(A) to
Inoue, entitled: "Composite antenna".
SUMMARY OF THE DISCLOSED TECHNIQUE
In accordance with one aspect of the disclosed technique, there
is thus provided an antenna assembly for providing high frequency (HF)
radio communication in two different operating modes. The antenna
assembly includes a whip antenna and at least two antenna wire
segments. The whip antenna establishes short range HF radio
communication with a communication target, via ground wave or
low-efficiency skywave propagation, allowing communication when the
antenna assembly is in motion. The antenna wire segments are
deployable to form an inverted-V antenna using the whip antenna as a
center mast. The inverted-V antenna establishes short or medium range
HF radio communication with a communication target, via Near Vertical
Incidence Skywave (NVIS) or directional skywave propagation, allowing
rapid deployment of the antenna wire segments when the antenna
assembly is stationary. The antenna assembly may be mounted aboard a
mobile platform, such as a vehicle. The antenna assembly may
alternatively be conveyed by at least one person, or further alternatively
be mounted aboard a stationary platform. The short range communication
may be with a communication target situated at a range of up to
approximately 300km from the antenna assembly. The medium range
communication may be with a communication target situated at a range of
between approximately 300-1 000km from the antenna assembly. The
antenna assembly may further include an antenna isolator, coupled with
the whip antenna and the antenna wire segments. The antenna isolator
provides isolation between the whip antenna and the antenna wire
segments, preventing current leakage during high voltage operation. The
antenna assembly may further include an HF transceiver, coupled with the
whip antenna and the antenna wire segments, for transmitting and
receiving HF radio frequency signals. The HF transceiver may be coupled
with the antenna wire segments via a twin-lead cable. The antenna
assembly may further include an antenna coupler, coupled with the whip
antenna, with the antenna wire segments, and with the HF transceiver.
The antenna coupler tunes the operational antenna impedance to match
the transmitter/receiver output/input impedance of the HF transceiver.
The antenna coupler may be a balanced antenna coupler. The antenna
assembly may further include at least two ground anchors and at least two
wire isolators. The ground anchors are secured to a ground surface when
forming the inverted-V antenna. The wire isolators are coupled to
respective ground anchors and to respective antenna wire segments,
providing isolation of the antenna wire segments from the ground surface.
The whip antenna is bent downwards when establishing the short range
communication, to enable safe motion of the antenna assembly. The whip
antenna is aligned in an upright position when used as a central mast for
the inverted-V antenna. The whip antenna includes a whip antenna
radiator and a whip antenna base, which can support the whip antenna
radiator in a bent position or in an upright position. The antenna assembly
may further include at least two wire holders, coupled with the antenna
isolator, for holding the antenna wire segments when the inverted-V
antenna is formed. A storage bag may be used to store away the antenna
wire segments when not in use. The antenna wire segments may be
wound onto a spool when not in use, and unwound from the spool when
being deployed to form the inverted-V antenna. A winding mechanism
may be used to wind and unwind the antenna wire segments onto or from
the spool.
In accordance with another aspect of the disclosed technique,
there is thus provided a method for establishing and maintaining HF radio
communication in two different operating modes with an antenna
assembly. The method includes the procedure of initiating an HF radio
communication session with the antenna assembly. The method further
includes the procedure of, when the antenna assembly is in motion,
selecting a whip antenna operating mode of the antenna assembly, and
activating the whip antenna to provide short range HF radio
communication with a communication target, via ground wave or
low-efficiency skywave propagation, allowing communication when the
antenna assembly is in motion. The method further includes the
procedure of, when the antenna assembly is stationary, selecting an
inverted-V antenna operating mode of the antenna assembly, deploying
antenna wire segments of the antenna assembly and forming an inverted-
V antenna using the whip antenna as a center mast, and activating the
inverted-V antenna to provide short or medium range HF radio
communication with a communication target, via Near Vertical Incidence
Skywave (NVIS) or directional skywave propagation, allowing rapid
deployment of the antenna wire segments when the antenna assembly is
stationary. The method further includes the procedure of terminating the
HF radio communication session. The antenna assembly may be
mounted aboard a mobile platform, such as a vehicle. The antenna
assembly may alternatively be conveyed by at least one person, or further
alternatively be mounted aboard a stationary platform. The short range
communication may be with a communication target situated at a range of
up to approximately 300km from the antenna assembly. The medium
range communication may be with a communication target situated at a
range of between approximately 300-1 000km from the antenna assembly.
Deploying the antenna wire segments may include securing ground
anchors to a ground surface, coupling a wire isolator to each of the ground
anchors, and coupling an end of each of the antenna wire segments to a
respective one of the wire isolators, which provide isolation of the antenna
wire segments from the ground surface. The method may further include
the procedure of bending the whip antenna downwards before activating
the whip antenna, to enable safe motion of the antenna assembly. The
whip antenna is aligned in an upright position when used as a central
mast for the inverted-V antenna. A storage bag may be used to store
away the antenna wire segments when not in use. The antenna wire
segments may be wound onto a spool when not in use, and unwound
from the spool when being deployed to form the inverted-V antenna.
BRIEF DESCRIPTION OF THE DRAWINGS
The disclosed technique will be understood and appreciated
more fully from the following detailed description taken in conjunction with
the drawings in which:
Figure 1 is a block diagram of an antenna assembly for HF radio
communication in two different operating modes, constructed and
operative in accordance with an embodiment of the disclosed technique;
Figure 2 is a rear view schematic illustration of the antenna
assembly of Figure 1 mounted on an armored military vehicle and
deployed in a whip antenna operating mode, constructed and operative in
accordance with an embodiment of the disclosed technique;
Figure 3 is a rear view schematic illustration of the antenna
assembly of Figure 1 mounted on an armored military vehicle and
deployed in an inverted-V antenna operating mode, constructed and
operative in accordance with an embodiment of the disclosed technique;
and
Figure 4 is a block diagram of a method for establishing and
maintaining HF radio communication in two different operating modes with
an antenna assembly, operative in accordance with an embodiment of the
disclosed technique.
DETAILED DESCRIPTION OF THE EMBODIMENTS
The disclosed technique overcomes the disadvantages of the
prior art by providing an antenna assembly adapted for rapid deployment
and to provide effective and reliable HF radio communication aboard a
mobile platform, using either a whip antenna operating mode to provide
ground wave or low efficiency skywave propagation for short range
communication, or an inverted-V antenna operating mode to provide
skywave propagation for short range or medium range communication.
The term "mobile platform", and any variations thereof, as used
herein refers to any platform or surface capable of moving from one
location to another, including, but not limited to: a vehicle, a transportation
medium, or a person. Accordingly, the antenna assembly of the disclosed
technique may be mounted onto a vehicle (i.e., constituting a vehiclemounted
antenna assembly) or conveyed directly by at least one person
(i.e., constituting a portable antenna assembly).
Reference is now made to Figures 1, 2 and 3. Figure 1 is a
block diagram of an antenna assembly, generally referenced 110,
constructed and operative in accordance with an embodiment of the
disclosed technique. Figure 2 is a rear view schematic illustration of the
antenna assembly 110 of Figure 1 mounted on an armored military
vehicle, generally referenced 140, and deployed in a whip antenna
operating mode, constructed and operative in accordance with an
embodiment of the disclosed technique. Figure 3 is a rear view schematic
illustration of the antenna assembly 110 of Figure 1 mounted on an
armored military vehicle 140 and deployed in an inverted-V antenna
operating mode, constructed and operative in accordance with an
embodiment of the disclosed technique. Antenna assembly 110 includes
a whip antenna 112, a balanced antenna coupler 114, an HF transceiver
116, a pair of antenna wire segments 118 and 120, an antenna isolator
122, a pair of wire isolators 124 and 126, and a pair of ground anchors
128 and 130. Whip antenna 112 is made up of a radiator portion 113 and
a base portion 115.
Antenna isolator 122 is coupled with whip antenna 112 and with
antenna wire segments 118 and 120. Antenna coupler 114 is coupled
with whip antenna 112, with antenna wire segments 118 and 120, and
with HF transceiver 116. Antenna wire segments 118, 120 are each
coupled with a respective wire isolator 124, 126, which in turn are each
coupled with a respective ground anchor 128, 130, when deployed to
provide an inverted-V antenna, as will be elaborated upon herein below.
Antenna assembly 110 is preferably mounted onto a vehicle,
such as a civilian-operated vehicle (e.g., a truck, a sport utility vehicle
(SUV), an off-road vehicle, a transporter vehicle, a Jeep, a Land Rover
model vehicle, a Hummer brand vehicle, and the like) or a military vehicle
(e.g., a tank, an armored personnel carrier such as the BTR series, and
the like), a ship (e.g., a naval ship), or onto another type of mobile
platform. Antenna assembly 110 may alternatively be held by a user (e.g.,
carried by a soldier) or mounted onto a fixed stationary platform. When
mounted on a vehicle or other mobile platform, antenna assembly 110
utilizes a larger and more powerful antenna coupler (e.g., 150W) and a
heavier and more rugged whip antenna, to ensure robustness and
integrity. When used in a portable configuration (i.e., being carried by a
person), antenna assembly 110 utilizes a lighter weight antenna coupler
(e.g., 30W) and a lighter weight whip antenna (e.g., 1 kg), to ease carrying
and transportation.
Whip antenna 112 is a standard monopole antenna with an
omnidirectional radiation pattern, made up of a straight flexible wire
mounted perpendicularly over a conducting surface, as known in the art.
Whip antenna 112 may be telescopically extendable and retractable, or
may be composed of individual sections that are attachable and
detachable to/from one other in order to extend or retract the antenna as
necessary for operation. Whip antenna 112 is fixedly mounted onto a
short ledge 142 adjoining a side of vehicle 140. Alternatively, whip
antenna 112 may be mounted onto another region of vehicle 140 (e.g., on
the roof of vehicle 140) or onto a component affixed to a different region of
vehicle (e.g., near the front or rear thereof). Whip antenna base 115, or
an alternative/additional structural feature of whip antenna 112, enables
selective bending of the whip antenna radiator 113 in a particular direction
(e.g., forward, backward, toward one side) or maintaining whip antenna
radiator 113 in an upright position.
Antenna wire segments 118 and 120 are long portions of wires
of metallic conductors that can mutually function as a driven element in a
dipole antenna configuration. Each wire segment 118, 120, is wound onto
a spool or reel allowing the wire segment to be lengthened or shortened.
The other end of wire segments 118, 120 is connected to antenna coupler
114. When not in use, antenna wire segments 118, 120 are preferably
kept fully wound around the spool and stored inside a storage bag 138
(Figure 2). When deployed, each wire segment 118, 120 is removed from
storage bag 138 and routed through a respective wire holder 144, 146
affixed to either side of antenna isolator 122. Wire holders 144 and 146
may each be formed as a small ring with an opening and extending
horizontally from the vertically oriented whip antenna radiator 113 (as
depicted in Figure 3), such that each wire segment 118, 120 is looped
through the respective ring with one end hanging downward on either
side. Wire holders 144, 146 may be embodied by an alternative structure
or configuration in a manner which enables the deployment of wire
segments 118, 120 in an inverted-V formation using whip antenna 112 as
a central mast while maintaining isolation between wire segments 118,
120 and whip antenna 112. Antenna assembly 110 may generally include
any even number of antenna wire segments, but preferably includes two
(a larger number of wire segments may slightly increase the overall
antenna gain, but would significantly lengthen the time required for
deployment). The wire segments 118, 120 are manufactured from
antenna wire that provides the required strength when tensioned and yet
flexible enough for rapid deployment during multiple instances (i.e., the
antenna wire segments may be reused numerous times and
stored/retrieved as needed). Antenna assembly 110 may include a
mechanism for winding and unwinding antenna wire segments 118, 120
around their spools in a quick and convenient manner (e.g., similar to a
self-extracting tape measure device). In general, antenna wire segments
118, 120 may be wound or unwound using any suitable device or
mechanism for retracting or extending the length of wire segments 118,
120. For example, antenna wire segments 118, 120 may be composed of
a retractable/extendable telescopic cable, or a single cable that is
dividable into multiple shorter sections (each of which may be stored away
separately).
Antenna coupler 114 provides equal current at both terminals of
antenna wire segments 118, 1 0 and eliminates any additional RF current
on the coaxial shielding. Antenna coupler 114 efficiently and
automatically tunes the operational antenna impedance to match the
transmitter/receiver output/input impedance of HF transceiver 116 (which
is typically around 50) . Antenna coupler 114 is preferably a balanced
antenna coupler, which establishes a true isolation of the antenna
terminals from the ground and provides equal current levels at both
terminals, which significantly improves the antenna gain and radiation
pattern. An unbalanced coupler, which would result in a much lower
overall antenna gain, may optionally be used instead.
HF transceiver 116 includes all the necessary components and
circuitry for transmitting and receiving RF signals within the high frequency
(HF) portion of the radio spectrum (i.e., approximately 2-30 MHz). HF
transceiver 116 incorporates the transmitting and receiving components in
a single unit, although may alternatively be embodied by separate
transmitter and receiver units. HF transceiver 116 is coupled to antenna
coupler 114 through a feed line, such as a coaxial cable, that provides an
RF signal for transmitting/receiving and a DC voltage for the operation of
antenna coupler 114. Alternatively, HF transceiver 116 may be coupled to
antenna coupler 114 with both a coaxial cable and an additional
control/DC voltage cable. HF transceiver 116 also incorporates a radio
panel interface that allows a user to select different operational modes
and settings for antenna assembly 110.
Antenna isolator 1 2 is preferably affixed to the upper portion of
whip antenna radiator 113 (e.g., at the very tip) and provides the required
isolation between the whip antenna 112 and the wire segments 118 and
120, preventing current leakage during high voltage operation. Antenna
isolator 122 may generally be disposed at any location along whip
antenna radiator 113. It should be noted that raising the height of antenna
isolator 122 along whip antenna radiator 113 will increase the dipole gain
of the inverted-V antenna formed by wire segments 118, 120 but
necessitates a more rigid whip antenna 112, while conversely, a lower
situated antenna isolator 122 enables a more flexible whip antenna 112 to
be used but results in a lower dipole gain.
Referring now to Figure 2, whip antenna 112 is utilized to
establish an HF radio communication link with a communication target
(not shown) while vehicle 140 is in motion. An operator of vehicle 140
(e.g., a driver or a passenger) initially selects a whip antenna operating
mode of antenna assembly 110, such that all the output power from HF
transceiver 116 will be directed through only to the whip antenna terminal
(and not to the wire segments terminals). While whip antenna 112 is
operational, antenna wire segments 118 and 1 0 are preferably stored in
the storage bag 138 and deactivated, for practical considerations and so
as not to diminish the gain of whip antenna 112. Whip antenna radiator
113 is bent downwards to permit vehicle 140 to continue travelling in a
safe manner, preventing any impacts, shocks or collisions that could occur
if whip antenna radiator 113 was in an upright position. The bending of
whip antenna radiator 113 may be implemented remotely while vehicle
140 is in motion, e.g., using a remote control associated with whip
antenna 112. Whip antenna 112 functions as a radiating element that
provides HF ground wave propagation, so that ground wave radio signals
are transmitted to and received from the target located a relatively short
distance away (e.g., up to approximately 40km from antenna assembly
110). Whip antenna 112 may also be utilized to provide HF skywave
propagation although at a reduced efficiency (the antenna gain at acute
elevation angles is very low, especially at lower HF frequencies), allowing
skywave radio signals to reach a target situated at a range of
approximately 40-200km. When the communication session is completed,
whip antenna 112 is deactivated and ceases propagation of ground
wave/low-efficiency skywave radio frequencies.
Referring now to Figure 3, when the operator of vehicle 140
wants to establish a communication link with a communication target (not
shown) located at a further distance away (e.g., at a range of
approximately 40-300km from antenna assembly 110), ground wave HF
propagation is insufficient. Accordingly, the operator stops (e.g., parks)
vehicle 140 at a suitable location and then proceeds to deploy antenna
wire segments 118, 120 to form an inverted-V antenna structure. In
particular, the operator retrieves the wound spools of antenna wire
segments 118, 120 from within storage bag 138 and unwinds the antenna
wire segments 118, 120 from their respective spools. At a specific
marked point of each wire segment, the operator secures the anchors
128, 130 into the ground. Ground anchors 128, 130 are positioned on
either side of vehicle 140 at a minimum distance (e.g., 8-25m) away from
vehicle 140. Ground anchors 128, 130 are coupled to respective wire
isolators 124, 126, e.g., via polyethylene terephthalate (PET) fibers, and
the wire isolators 124, 126 are coupled to the free end of respective
antenna wire segments 118, 120, which are pulled taught. Ground
anchors 128, 130 may be embodied by any suitable device or mechanism
adapted to securely fasten an antenna wire segment to the ground
surface, while ensuring isolation between the wire segments 118, 120 and
the ground. For example, wire segments 118, 120 may be affixed to
another structure situated on the ground (e.g., a fencepost) as long as the
wire isolation is maintained. Consequently, each wire segment 118, 120
extends vertically along the vertically oriented whip antenna 112 until a
distal end of whip antenna 112 at which it is coupled (i.e., at wire holders
144, 146 affixed to either side of antenna isolator 122) and then slopes
downward toward anchors 128, 130 secured to the ground, together
forming an inverted-V configuration. Antenna wire segments 118, 120
function as radiating elements while whip antenna 112 functions as a
central supporting mast for an inverted-V antenna, generally referenced
148. Antenna wire segments 118, 120 may generally be coupled to whip
antenna 112 at any point thereof (e.g., wire holders 144, 146 may be
disposed at any height respective of whip antenna 112), but the gain of
inverted-V antenna 148 is a function of the height of the wire segments
118, 120, such that the antenna gain increases as the apexes of wire
segments 118, 120 are raised higher. Inverted-V antenna 148 is
preferably configured in a symmetrical manner, i.e., such that the height of
both wire segments 118, 120 are substantially similar and the angles
formed between the mast and each of the wire segments 118, 120 are
substantially similar. A non-symmetrical configuration would result in
reduced efficiency. The antenna wire segments 118, 120 are preferably
completely unspooled (i.e., to attain their maximum length) in order to
obtain the highest antenna gain. For example, wire segments 118, 120
having a length of around 15m would provide efficient NVIS
communication in different environments (e.g., during both daytime and
nighttime). Theoretically, optimal efficiency and antenna gain would result
if the antenna wire segments were to be deployed in a perfectly horizontal
alignment, but practically this is not feasible and would require a
considerable amount of time and resources to set up. Antenna wire
segments 118, 120 may be coupled to HF transceiver 116 indirectly, via
an intermediate coupler, such that wire segments 118, 120 do not extend
all the way to HF transceiver 116 when inverted-V antenna 148 is
deployed. For example, a twin-lead cable may be used to convey RF
signals between HF transceiver 116 and antenna wire segments 118, 120,
such that the twin-lead cable is coupled at one end to HF transceiver 116
and at the other end to a splitter coupled to each of antenna wire
segments 118, 120. It is appreciated that the deployment of inverted-V
antenna 148 may be done fairly quickly, typically requiring only a few
minutes to set up completely.
The operator proceeds to select an inverted-V antenna
operating mode of antenna assembly 110 (e.g., via the radio panel
interface of HF transceiver 116), such that all the output power from HF
transceiver 116 will be directed through only to the wire segments
terminals (and not to the whip antenna terminal). While inverted-V
antenna 148 is operational, whip antenna 112 is deactivated (i.e., does
not radiate) and is prevented from interference with wire segments 118,
120 by antenna isolator 122. Inverted-V antenna 148 provides HF
skywave propagation, allowing HF radio communication with a relatively
distant communication target. In particular, inverted-V antenna 148 may
operate through NVIS propagation, utilizing reflections and refractions
from the ionosphere, allowing NVIS radio signals to reach a "short range"
target situated at a range of up to approximately 300km (omni
directionally). Inverted-V antenna 148 may also operate through
directional skywave propagation, allowing skywave radio signals to reach
a "medium range" target situated at a range of approximately 300-
1000km. When the communication session is completed, wire segments
118 and 120 are deactivated and the operator dismantles inverted-V
antenna 148, i.e., by detaching antenna wire segments 118, 120 from the
respective wire isolators 124, 126 and from the respective anchors 128,
130. Antenna wire segments 118, 120 are then wound back onto their
spools and placed back into storage bag 138. Wire isolators 124, 126 and
ground anchors 128, 130 may also be stored away while not in use.
It is appreciated that whip antenna operation of antenna
assembly 110 allows an operator of vehicle 140 to quickly and
conveniently establish secure and effective HF radio communication (i.e.,
ground wave or low-efficiency skywave propagation) with a relatively near
(short range) communication target while vehicle 140 is in motion.
Correspondingly, inverted-V antenna operation of antenna assembly 110
allows the vehicle operator to establish secure and effective HF radio
communication (i.e., NVIS or directional skywave propagation) with a
relatively near (short range) or relatively distant (medium range)
communication target, briefly after stopping vehicle 140 (e.g., after several
minutes required for setup). In this manner, a single antenna assembly in
accordance with the disclosed technique can be utilized in different ways,
depending on the circumstances, for providing reliable HF radio
communication.
It is noted that if the vehicle operator inadvertently attempts to
activate the wrong antenna after a particular antenna operational mode for
antenna assembly 110 has been selected, the operator may be notified
accordingly (e.g., via a warning message displayed on the radio panel
interface of HF transceiver 116).
Reference is now made to Figure 4, which is a block diagram of
a method for establishing and maintaining HF radio communication in two
different operating modes with an antenna assembly, operative in
accordance with an embodiment of the disclosed technique. In procedure
182, a vehicle is maneuvered. Referring to Figures 2 and 3, armored
military vehicle 140 is driven by a vehicle driver.
In procedure 184, an HF radio communication session is
initiated with an antenna assembly onboard the vehicle. Referring to
Figures 2 and 3, a vehicle operator of vehicle 140 uses antenna assembly
110 to initiate a radio communication session with a communication target
(not shown).
When the vehicle is in motion, short range radio communication
may be established. In procedure 186, a whip antenna operating mode is
selected. Referring to Figure 2, a vehicle operator of vehicle 140 selects a
whip antenna operating mode of antenna assembly 110, e.g., via a radio
panel interface of HF transceiver 116. In procedure 188, the whip
antenna of the antenna assembly is bent to enable safe vehicle motion.
Referring to Figure 2, an operator of vehicle 140 bends whip antenna
radiator 113 downwards, to permit vehicle 140 to continue travelling in a
safe manner and avoiding impacts, shocks or collisions that could occur if
whip antenna radiator 113 was positioned upright. In procedure 190, the
whip antenna is activated to provide short range HF radio communication,
via ground wave or low-efficiency skywave propagation. Referring to
Figure 2, whip antenna 112 may provide HF ground wave propagation to
allow communication with a target situated up to approximately 40km
away. Alternatively, whip antenna 112 may be utilized to provide HF
skywave propagation at a reduced efficiency to allow communication with
a target situated at a range of approximately 40-200km away.
When the vehicle is stationary (i.e., after the vehicle driver has
stopped or parked the vehicle), short range or medium range HF radio
communication may be established. In procedure 192, an inverted-V
antenna operating mode is selected. Referring to Figure 3, a vehicle
operator of vehicle 140 selects an inverted-V antenna operating mode of
antenna assembly 110, e.g., via a radio panel interface of HF transceiver
116. In procedure 194, antenna wire segments of the antenna assembly
are deployed and an inverted-V antenna is formed using the whip antenna
as a center mast. Referring to Figure 3, an operator of vehicle 140 sets
up inverted-V antenna 148 using antenna wire segments 118, 120 as
radiating elements and whip antenna 112 as a central supporting mast.
Wire segments 118, 120 are retrieved from storage bag 138 and unwound
from their spools; ground anchors 1128, 130 are secured to the ground at
fixed distances on either side of vehicle 140; antenna wire segments 118,
120 are pulled taught while positioned through wire holders 144, 146
affixed to antenna isolator 122, and then angled downwards and joined to
wire isolators 124, 160, which are affixed to ground anchors 128, 130
(e.g., via PET fibers). In procedure 196, the inverted-V antenna is
activated to provide short or medium range HF radio communication, via
NVIS or directional skywave propagation. Referring to Figure 3, inverted-
V antenna 148 may provide omni-directional NVIS propagation to allow
communication with a short range target situated up to approximately
300km away. Inverted-V antenna 148 may also provide directional
skywave propagation to allow communication with a medium range target
situated at a range of approximately 300-1 000km away.
In procedure 198, the HF radio communication session is
terminated. Referring to Figures 2 and 3, the operator of vehicle 140
terminates the radio communication session with the communication
target. If antenna assembly 110 had been operating in whip antenna
operating mode, then the operator deactivates whip antenna 112 which
then ceases ground wave/low-efficiency skywave propagation. If antenna
assembly 110 had been operating in inverted-V antenna operating mode,
then the operator deactivates antenna wire segments 118, 120 to cease
NVIS/directional skywave propagation and dismantles inverted-V antenna
148.
It will be appreciated by persons skilled in the art that the
disclosed technique is not limited to what has been particularly shown and
described hereinabove.
CLAIMS
1. An antenna assembly for providing high frequency (HF) radio
communication in two different operating modes, said antenna
assembly comprising:
a whip antenna, operative for establishing short range HF radio
communication with a communication target, via ground wave or
low-efficiency skywave propagation, allowing communication when
said antenna assembly is in motion; and
at least two antenna wire segments, deployable to form an
inverted-V antenna using said whip antenna as a center mast, said
inverted-V antenna operative to establish short or medium range HF
radio communication with a communication target, via Near Vertical
Incidence Skywave (NVIS) or directional skywave propagation,
allowing rapid deployment of said antenna wire segments when said
antenna assembly is stationary.
2. The antenna assembly of claim 1, wherein said antenna assembly is
mounted aboard a mobile platform.
3. The antenna assembly of claim 2, wherein said mobile platform is a
vehicle.
4. The antenna assembly of claim 3, wherein said vehicle is selected
from the list consisting of:
a military vehicle;
a tank;
an armoured personnel carrier;
a ship;
a civilian vehicle;
a truck;
a sport utility vehicle (SUV);
an off-road vehicle;
a transporter vehicle;
a Jeep;
a Land Rover model vehicle; and
a Hummer brand vehicle.
5. The antenna assembly of claim 1, wherein said antenna assembly is
conveyed by at least one person.
6. The antenna assembly of claim 1, wherein said antenna assembly is
mounted aboard a stationary platform.
7. The antenna assembly of claim 1, wherein said short range
communication with a communication target comprises said
communication target being situated at a range of up to
approximately 300km from said antenna assembly.
8. The antenna assembly of claim 1, wherein said medium range
communication with a communication target comprises said
communication target being situated at a range of between
approximately 300-1 000km from said antenna assembly.
9. The antenna assembly of claim 1, further comprising:
an antenna isolator, coupled with said whip antenna and said
antenna wire segments, said antenna isolator operative to provide
isolation between said whip antenna and said antenna wire
segments, preventing current leakage during high voltage operation.
10. The antenna assembly of claim 1, further comprising:
an HF transceiver, coupled with said whip antenna and said
antenna wire segments, said HF transceiver operative for
transmitting and receiving HF radio frequency signals.
1. The antenna assembly of claim 10, wherein said HF transceiver is
coupled with said antenna wire segments via a twin-lead cable.
2. The antenna assembly of claim 10, further comprising:
an antenna coupler, coupled with said whip antenna, with said
antenna wire segments, and with said HF transceiver, said antenna
coupler operative to tune the operational antenna impedance to
match the transmitter/receiver output/input impedance of said HF
transceiver.
3. The antenna assembly of claim 12, wherein said antenna coupler is a
balanced antenna coupler.
4. The antenna assembly of claim 1, further comprising:
at least two ground anchors, operative for being secured to a
ground surface when forming said inverted-V antenna; and
at least two wire isolators, each coupled to a respective one of
said ground anchors and to a respective one of said antenna wire
segments, said wire isolators providing isolation of said antenna wire
segments from said ground surface.
5. The antenna assembly of claim 1, wherein said whip antenna is bent
downwards when establishing said short range communication, to
enable safe motion of said antenna assembly.
6. The antenna assembly of claim 1, wherein said whip antenna is
aligned in an upright position when used as a central mast for said
inverted-V antenna.
7. The antenna assembly of claim 1, wherein said whip antenna
comprises:
a whip antenna radiator; and
a whip antenna base, operative for supporting said whip
antenna radiator in a bent position or in an upright position.
8. The antenna assembly of claim 9, further comprising at least two wire
holders, coupled with said antenna isolator, said wire holders
operative for holding said antenna wire segments when said
inverted-V antenna is formed.
19. The antenna assembly of claim 1, further comprising a storage bag,
operative for storing away said antenna wire segments when not in
use.
20. The antenna assembly of claim 1, wherein said antenna wire
segments are wound onto a spool when not in use, and unwound
from said spool when being deployed to form said inverted-V
antenna.
2 1. The antenna assembly of claim 20, further comprising a winding
mechanism, operative to wind/unwind said antenna wire segments
onto/from said spool.
22. A method for establishing and maintaining HF radio communication
in two different operating modes with an antenna assembly, the
method comprising the procedures of:
initiating an HF radio communication session with said antenna
assembly;
when said antenna assembly is in motion:
selecting a whip antenna operating mode of said antenna
assembly; and
activating said whip antenna to provide short range HF
radio communication with a communication target, via ground
wave or low-efficiency skywave propagation, allowing
communication when said antenna assembly is in motion,
when said vehicle is stationary:
selecting an inverted-V antenna operating mode of said
antenna assembly;
deploying antenna wire segments of said antenna
assembly and forming an inverted-V antenna using said whip
antenna as a center mast; and
activating said inverted-V antenna to provide short or
medium range HF radio communication with a communication
target, via Near Vertical Incidence Skywave (NVIS) or directional
skywave propagation, allowing rapid deployment of said
antenna wire segments when said antenna assembly is
stationary,
and
terminating said HF radio communication session.
23. The method of claim 22, wherein said antenna assembly is mounted
aboard a mobile platform.
24. The method of claim 23, wherein said mobile platform is a vehicle.
25. The method of claim 22, wherein said antenna assembly is conveyed
by at least one person.
26. The method of claim 22, wherein said antenna assembly is mounted
aboard a stationary platform.
27. The method of claim 22, wherein said short range communication
with a communication target comprises said communication target
being situated at a range of up to approximately 300km from said
antenna assembly.
28. The method of claim 22, wherein said medium range communication
with a communication target comprises said communication target
being situated at a range of between approximately 300-1 000km
from said antenna assembly.
29. The method of claim 22, wherein said procedure of deploying
antenna wire segments comprises securing ground anchors to a
ground surface, coupling a wire isolator to each of said ground
anchors, and coupling an end of each of said antenna wire segments
to a respective one of said wire isolators, said wire isolators providing
isolation of said antenna wire segments from said ground surface.
30. The method of claim 22, further comprising the procedure of bending
said whip antenna downwards before activating said whip antenna, to
enable safe motion of said antenna assembly.
3 1. The method of claim 22, wherein said whip antenna is aligned in an
upright position when used as a central mast for said inverted-V
antenna.
32. The method of claim 22, wherein said antenna wire segments are
stored away in a storage bag when not in use.
33. The method of claim 22, wherein said antenna wire segments are
wound onto a spool when not in use, and unwound from said spool
when being deployed to form said inverted-V antenna.