Note: Descriptions are shown in the official language in which they were submitted.
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MULTI-BEAM ANTENNA WITH MULTI-DEVICE CONTROL UNIT
REFERENCE TO PRIORITY APPLICATIONS
This application claims priority to commonly-owned United States Provisional
Patent Application No. 60/027,687.
0
TECHNICAL FIELD
This invention relates to the field of cellular or mobile telephone base
station
antennas and, more particularly, relates to a remote electrical tilt (RET)
base station
antenna with a removable multi-device control unit that can be switched to
remotely
control more than one electro-mechanical actuator contained inside the
antenna.
BACKGROUND OF THE INVENTION
Antennas with variable electrical tilt (VET) functionality are known in the
art.
These antennas, which are used in cellular networks, enable network operators
to
electrically tilt the elevation beam pointing direction of the antenna by
manually
rotating a knob or translating a shaft on the exterior of the antenna. The
knob or
shaft is linked to phase shifters inside the antenna that convert the
mechanical
rotation or translation of the shaft to phase changes in the radio frequency
beam
forming network inside the antenna. Changes in phase between radiating
elements
inside the antenna cause the beam emitted from the antenna to tilt up or down
relative to mechanical boresite of the antenna. An example of a cellular base
station
antenna demonstrating VET technology is depicted in US 7,068,236.
Beam tilt adjustment is needed in cellular networks to reduce signal
propagation between sites in the network in order to minimize signal
interference and
to maximize network capacity. Antennas with VET functionality allow network
operators to make accurate tilt adjustments at a cell site without
mechanically tilting
the antenna and without changing the visual appearance of the site. Antennas
with
VET functionality typically include some sort of lilt indicator to provide
visual feedback
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of the antenna electrical tilt setting to a person located at the antenna to
inspect the
antenna or to manually make the tilt adjustment.
Remote electrical tilt (RET) antennas are also known in the art. RET antennas
incorporate an electro-mechanical actuator attached to or installed inside of
the
antenna to rotate the knob or translate the shaft on a VET antenna. This
enables the
electrical tilt of the VET antenna to be controlled from a remote location,
eliminating
the expense of hiring a rigger to climb the tower and manually adjust the
electrical tilt
of the antenna beam.
This conventional configuration of RET actuators is shown in FIG 1, in which a
tri-band antenna 4 includes three self contained, separately removable RET
actuators
5a-c, one for each operational frequency band of the antenna. Each RET
actuator is
a self contained electro-mechanical device with lightning protection circuits,
communications circuits, a motor, motor control circuits, power control
circuits and a
motor position sensor contained within a single enclosure. For antennas
designed to
operate over multiple frequency bands, multiple, stand-alone RET actuators are
attached to or inserted inside of the antenna housing. Cable assemblies are
connected between the RET actuators to provide power and signaling to the
multiple
RET actuators for that antenna. This design approach is expensive due to the
cost of
the external cable assemblies and the redundant electronic components used by
multiple RET actuators. In addition, removable RET actuators must be
configured to
physically align with and receive the phase shifter shafts for each beam of
the multi-
beam antenna, which requires a different removable RET actuator configuration
for
each antenna with a different phase shifter shaft configuration.
The locations of the phase shifter adjustment knobs or shafts on a typical
multi-band RET antenna are constrained by the physical size and shape of the
RET
actuators and by their attachment mechanisms. The phase shifter adjustment
knobs
or shafts must be spaced far enough apart to allow the multiple RET actuators
to be
attached to the antenna without mechanical interference. The knobs or shafts
must
also be spaced far enough apart to provide room for the RET actuator mounting
hardware and to provide access for the tools used to install the mounting
hardware.
As a result, the location of the phase shifter adjustment knobs or shafts on
the
antenna are often determined by the geometry of the RET actuators and not by
the
optimum phase shifter placement inside the antenna. These constraints increase
the
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mechanical complexity of the RET antenna design and increase the development
time and costs for new antenna models.
There is, therefore, a continuing need for a RET antenna that can be produced
with fewer electronic parts for lower cost and that reduces mechanical
constraints on
the phase shifter drive shaft locations inside the antenna.
SUMMARY OF THE INVENTION
The present invention meets the need described above in a RET antenna with
a multi-device control unit that is configured to be inserted into and removed
from a
receptacle in the antenna. The multi-device control unit works with one or
more
modular switching units, which are typically located inside the antenna
enclosure, to
control the motors and position sensors located inside the antenna to allow a
single
controller located in the multi-device control unit to control multiple
embedded
electro-mechanical actuators, such as phase shifter control motors. This
enables
multiple motors to share a common control system located in the multi-device
control
unit, which greatly reduces the number of electronic components required for a
multi-
beam RET antenna.
The multi-device control unit typically includes one or more lightning
protection
circuits, communications circuits, motor controllers, power control circuits
and motor
position sensing circuits inside a small housing, which is usually located
inside the
antenna housing at the time of manufacture. These components are shared
between
all motors inside the antenna through the modular switching unit, which allows
a
single set of components within the multi-device control unit to replace
redundant
components deployed in prior RET actuators. The modular switching unit
monitors
an internal addressing bus and closes the connections to the appropriate motor
and
motor position feedback sensor based on the hardware address for that motor.
The
modular switching unit is configured to be inserted into a receptacle in the
antenna
body and secured with two mounting screws
Generally described, the invention may be practiced as a multi-beam RET
base station antenna for a telecommunications system. The antenna includes a
number of beam systems supported by a housing. Each beam system includes a
number of antenna elements for directing a beam of electromagnetic energy in a
propagation direction, a plurality of phase shifters operatively connected to
the
antenna elements for tilting the beam propagation direction, a control device
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operatively connected to the phase shifters for operating the phase shifters
to tilt the
beam propagation direction, and a gear-motor unit operatively connected to the
control device for electro-mechanically driving the control device to tilt the
beam
propagation direction. The antenna also includes a multi-device control unit
operative to selectively control the beam propagation direction of each beam
system
and one or more modular switching devices configured to interface between the
multi-
device control unit and the motors and position sensors of the antenna systems
to
allow a single set of control electronics of the multi-device control unit to
selectively
control the beam propagation direction of each beam system.
The modular switching unit is typically located inside the enclosure and the
multi-device control unit is typically configured for manual insertion into
and removal
from a receptacle supported by the housing, which is typically open to the
exterior of
the antenna. The multi-device control unit typically includes a lightning
protection
circuit, a communications interface, an internal addressing interface, a motor
control
interface, a power sensing interface, and a power control circuit, which are
sufficient
components for the multi-device control unit. The modular switching device
typically
includes at least one switch, a signal routing device, and a plurality of
address
registers with each register associated with a beam system of the antenna,
which are
sufficient components for the modular switching device.
The invention may also be implemented in a method for providing a base
station antenna for a telecommunications system with optional multi-beam RET
control functionality. An antenna operator is provided with an antenna that
includes a
plurality of beam systems located within an antenna enclosure. Each beam
system
includes a number of antenna elements for directing a beam of electromagnetic
energy in a propagation direction, a number of phase shifters operatively
connected
to the antenna elements for tilting the beam propagation direction, a control
device
operatively connected to the phase shifters for operating the phase shifters
to tilt the
beam propagation direction, and a gear-motor unit operatively connected to the
control device for electro-mechanically driving the control device to tilt the
beam
propagation direction. The antenna is provisioned prior to delivery with a
receptacle
supported by the housing, which may be open to the exterior of the antenna. In
response to a request from the antenna operator for optional multi-beam RET
control
functionality received after initial delivery of the antenna, the antenna
operator is
provided with a multi-device control unit configured for manual insertion into
and
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removal from the receptacle. The modular switching device is operable to
interface
between the multi-device control unit and the motors and position sensors of
the
antenna systems to allow a single set of control electronics of the multi-
device control
unit to selectively control the beam propagation direction of each beam
system.
In view of the foregoing, it will be appreciated that the present invention
provides a cost effective RET antenna that includes a multi-device control
unit that
greatly reducing the number of electronic components required for a multi-RET
system. The
specific techniques and structures for implementing particular
embodiments of the invention, and thereby accomplishing the advantages
described
above, will become apparent from the following detailed description of the
embodiments and the appended drawings and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an electrical schematic of a prior art configuration for a tri-band
antenna with three removable RET actuators.
FIG. 2 is an electrical schematic of a tri-band RET antenna with a multi-
device
control unit and internal switching devices.
FIG. 3 is a perspective view of a tri-band RET antenna with a multi-device
control unit.
FIG. 4 is a front view of the RET control equipment in an RET antenna with a
multi-device control unit.
FIG. 5 is a bottom view of the antenna enclosure of an RET antenna with a
multi-device control unit.
FIG. 6 is a front perspective view of a multi-device control unit and
associated
receptacle.
FIG. 7 is a rear perspective view of the multi-device control unit and
associated
receptacle.
DETAILED DESCRIPTION OF THE EMBODIMENTS
The present invention meets the need described above in a RET antenna with
a multi-device control unit that can be inserted into and removed from a
receptacle in
the antenna. The multi-device control unit works with one or more modular
switching
units, which are typically located inside the antenna enclosure. The multi-
device
control unit works together with motors and position sensors located inside
the
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antenna to allow a single controller located in the multi-device control unit
to control
multiple embedded electro-mechanical actuators, such as phase shifter control
motors. This enables multiple motors to share a common control system located
in
the multi-device control unit, which greatly reduces the number of electronic
components required for a multi-beam RET antenna.
The multi-device control unit typically includes one or more lightning
protection
circuits, communications circuits, motor controllers, power control circuits
and motor
position sensing circuits inside a small housing that is usually located
inside the
antenna enclosure. These components are shared between multiple motors inside
the antenna through the modular switching unit, which allows a single set of
components within the multi-device control unit to replace redundant
components
deployed in prior RET actuators. The modular switching unit monitors an
internal
addressing bus and closes the connections to the appropriate motor and motor
position feedback sensor based on the hardware address for that motor. This
enables multiple motors to share a common control system, greatly reducing the
number of electronic components required for a multi-RET system.
An electronic connector on the multi-device control unit plugs into a mating
connector on a receptacle mounted to the antenna enclosure to provide power,
signaling and motor position feedback between the multi-device control unit
and the
motors and position sensors inside the antenna. The motors and motor position
feedback sensors associated with each phase shifter adjustment shaft are
permanently attached inside the antenna. This
configuration eliminates the
mechanical drive train and linkage interface of conventional RET actuators and
replaces it with an electrical interface, implemented by the multi-device
control unit,
between the RET controller and the antenna. The electrical connections inside
the
antenna are made with a wiring harness which is flexible and does not
constrain the
mounting location for the motors and motor position sensors inside the
antenna.
An additional benefit of this design is that a customer does not need to
perform
a calibration step at installation. The position feedback sensors are
installed and
calibrated at the factory. Since there is never a mechanical separation in the
phase
shifter drive chain after the antenna leaves the factory, calibration is never
lost. The
present invention can be used for control of electro-mechanical actuators
inside the
antenna for purposes other than remote electrical beam tilt (RET.) Actuators
for
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remote azimuth beam steering (RAS) and/or remote azimuth beam width control
(RAB) can also be controlled using the same multi-device control unit.
Turning now to the figures, in which like element numerals refer to similar
element throughout the figures, FIG. 1 is an electrical schematic of a prior
art
configuration for a tri-band antenna 4 with three removable RET actuators 5a-
c. In
this arrangement, there is a mechanical interface 7 forming a drive train
linkage
between the antenna 4 and the RET actuators 5a-c. The tri-band antenna 4
includes
three self contained, separately removable RET actuators 5a-c, one for each
antenna
array implementing an operational frequency band of the antenna. Referring to
the
RET actuator 5a as a representative unit, the RET actuator is a self contained
electro-mechanical device with lightning protection circuits 52a and 54b, a
communications interface 56a, a position sensor interface 58a, a motor control
interface 60a, a power control circuit 62a, a motor 64a, and a position sensor
66a
contained within a single enclosure 67a. A drive rod 68a extending through the
enclosure drives the phase shifters of an associated antenna array 70a.
Therefore,
the RET actuators 5a-c contain a complete duplication of the equipment needed
to
control the electrical tilt of an array transmitting and receiving the signals
for one
beam of a multi-beam antenna. In addition, the drive rods 68a-c must
mechanically
interface with the control rods of the antenna arrays 70a-c, resulting in a
physically
restrictive and potentially complicated mechanical interface 7.
FIG. 2 is an electrical schematic of an antenna system 10 including a dual-
polarization, tri-band RET antenna 12 and a multi-device control unit 20. The
multi-
device control unit 20 includes lightning protection circuits 72 and 74, a
communications interface 76, an internal addressing interface 82, a motor
control
interface 84, a position sensing interface 86, and a power control circuit 88.
The
multi-device control unit 20 works together with modular switching devices 14a-
b,
which are typically located inside the antenna enclosure, to control the phase
shifters
to implement electrical beam tilt for up to four bands of a multi-band
antenna. The
multi-device control unit 20 and the modular switching devices 14a-b shown in
FIG. 2
therefore replace up to four sets of components (i.e., those components in the
multi-
device control unit) in the prior art design shown in FIG. 1. The single set
of
components in the multi-device control unit 20 works in concert with the
modular
switching devices 14a-b to control the electrical tilt for all three beams of
the antenna
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with the single set of control components in the multi-device control unit 20
with one
of the four potential control circuits dormant in this particular
configuration. It should
be appreciated that the multi-device control unit 20 may be may be configured
to
control additional dev ices. For example, a typical control unit can support
up to 16
motor/position sensors. Although FIG. 2 shows only two modular switching
devices
14a-b eight modular switching devices are typically installed, and a larger or
smaller
number could be installed as a matter of design choice.
As each modular switching device 14a-b is identical, a representative modular
switching device 14a will be described. The modular switching device, which is
configured to relay tilt control commands from the multi-device control unit
20 for up
to two operational bands implemented by antenna arrays, drives up to two
existing
internal phase shifter motors 90a-b and interfaces with up to two existing
internal
position sensors 92a-b of the host antenna. The modular switching device 14a
itself
includes switches 94a-b, fixed address registers 96a-b, and a comparator 98a.
The
comparator, which operates as a signal routing device to route control
commands to
the appropriate switch, could be replaced by functionality in or associated
with the
address registers or any other suitable signal routing device that directs
addressed
signals to an associated addressed device. However, it will be appreciated
that with
only two addresses to route, a simple comparator is adequate for the signal
routing
task in this particular embodiment. Control logic in the multi-device control
unit 20
operates cooperatively with the fixed address registers 94a-b and the
comparator 98a
to selectively control the phase shifter motors 90a-b. As result, the multi-
device
control unit 20 can independently control up to four phase shifter motors
through the
pair of modular switching devices 14a-b. Of course, a greater or smaller
number of
phase shifter motors could be controlled at the particular antenna requires.
It should be appreciated that the RET motors and position sensors are the
motors and position sensors originally provisioned in the antenna 12, which
avoids
the need for a mechanical linkage between the multi-device control unit 20 and
the
antenna 12. Therefore, there is only an electrical interface 15 is required
between
the multi-device control unit 20 and the antenna 12, as shown schematically in
FIG. 2.
If desired, the motors 90a-b, position sensors 92a-b, and switching devices
14a-b
can be installed but remain dormant in the antenna 12 in the absence of the
multi-
device control unit 20. This allows the antenna 12 to be provisioned at the
factory to
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be easily converted from manual tilt control to RET motorized tilt control
through the
addition of the multi-device control unit 20. Although the motors 90a-b,
position
sensors 92a-b and switching devices 14a-b are provisioned but left dormant in
a
manual tilt control antenna in this alternative, the cost of providing these
components
is more than offset by the benefit of eliminating the mechanical linkage and
accompanying physical design constraints required to connect the prior art
style RET
actuator to the antenna.
The modular switching devices 14a-b and associates wiring are preferably
located in strategic locations inside the antenna enclosure at the time of
manufacture.
Nevertheless, as an alternative arrangement, the multi-device control unit 20
may be
installed at the factory as original equipment, and a module containing the
switching
devices 14a-b may fit into the receptacle. In this case, the switching module
is
provided to the customer upon request for the optional RET functionality. As
another
alternative, the multi-device control unit 20 and the modular switching
devices 14a-b
may be combined into an integrated control module that fits into the
receptacle. In
this case, the integrated control module is provided to the customer upon
request for
the optional RET functionality. As yet another alternative, the combined
functionality
of the multi-device control unit 20 and the modular switching devices 14a-b
may be
installed inside or in association with the antenna at the factory as original
equipment,
and an activation device or activation code may be provided to the customer
upon
request for the optional RET functionality.
The advantages of the present invention can be enhanced with additional
motorized actuators, for example for beam azimuth steering and beam width
control.
In particular, the same size multi-device control unit 20 with additional
switching
devices located in strategic locations inside the antenna can control many
motorized
actuators to perform these and other antenna functions. Therefore, the multi-
device
control unit scheme can be extended to a wide range of motorized actuators
performing a wide range of functions within the antenna without the physical
limitations of mechanical linkages between the antenna and removable remote
control actuators.
FIG. 3 is a perspective view of the bottom portion of the antenna system 10
including the tri-band antenna 12 shown substantially to scale. For this
particular
antenna, the maximum width across the bottom of the antenna enclosure 25 is
approximately 10 inches (24.5 cm) and the maximum depth across the bottom of
the
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antenna enclosure is approximately 6 inches (14.2 cm). The height of the
antenna is
not shown and can vary considerably for different embodiments. For example, a
typical tri-band antenna 12 may be approximately 8 feet 10 inches (2.7 meters)
tall.
The bottom of the enclosure 25 carries six cable connectors represented by the
enumerated cable connector 16. Each vertical array transmits and receives one
band
of the tri-band antenna, and each band has two cable connectors, one for each
polarization. Also at the bottom of the enclosure, there are three manual beam
tilt
adjusters (including a beam tilt indicator displayed on the bottom portion of
a phase
shifter control rod, a manual beam tilt adjustment knob connected to the
bottom of the
phase shifter control rod, and an indicator cover) represented by the
enumerated
manual beam tilt adjuster 32 with a manual adjustment knob 18 the end. The
antenna
system 10 also includes the multi-device control unit 20, which fits into a
receptacle
22 (shown in FIGS. 4-7) in the antenna housing on the bottom of the enclosure
25.
FIG. 4 is a front view of the RET control equipment in the antenna 12. There
are three phase shifter control rods represented by the phase shifter control
rod 24,
three gear-motor units represented by the gear-motor unit 26, and three
position
sensors represented by the enumerated position sensor 28. A receptacle 22
receives
the multi-device control unit 20, physically supports and electrically
connects to the
switching devices 14a-b, which are implemented on PC cards. The switching
devices
14a-b are electrically connected by wires 35a-b that go to the gear motors and
positions sensors, as shown in FIG. 4 and schematically in FIG. 2.
FIG. 5 is a bottom view of the antenna enclosure 25 of an RET antenna 12.
The enclosure 25 carries the receptacle 22 (shown without the multi-device
control
unit in FIG. 5) for receiving the multi-device control unit 20, which plugs
into
receptacle and is secured by two screws. FIG. 6 is a front perspective view
and FIG.
7 is a rear perspective view of the multi-device control unit 20 and the
associated
receptacle 22. The front of the multi-device control unit 20 includes cable
connectors
for connecting the multi-device control unit to a remote control unit. The
rear of
the multi-device control unit includes a plug 32, such as a PC board edge
connector,
30 that plugs into a connector 34 on the receptacle 22. The switching
devices 14a-b
plug onto the connector 34 and, in turn, are connected by wire to the gear-
motors and
position sensors located inside the antenna, as shown in FIG. 4.
