FIELD OF THE INVENTION
[0001] The embodiments of the invention relate to radio communication and more particularly
but not exclusively to an active antenna unit.
BACKGROUND
[0002] In mobile communication networks, an active antenna unit is always installed as a
single AA unit (AA = Active Antenna). A total weight of the single AA unit usually
exceeds a so-called "one man lift" weight limit, which is usually in a range between
20 to 30 kg depending on a country or region. Therefore, two or more persons or even
a crane are required to replace a defective AA unit or to upgrade the AA unit by a
new AA unit with new technical features.
[0003] When a single device of the AA unit is defective or does not work anymore with a
sufficient performance, a replacement of the whole AA unit is necessary, because interconnects
within the AA unit have to be broken and have to be remade, when a new device has
to be installed. This can only be done in a repair center or service station because
the renewal of the interconnects requires highly skilled installation teams and specific
functional tests for a validation of the new interconnect such as PIM tests (PIM =
Passive Inter Modulation) for detecting and eliminating passive inter-modulation products
caused by a non-linearity of a device or element and which are detectable as interference
signals. Furthermore, each replacement usually requires a calibration of an antenna
pointing direction.
[0004] Instead of the AA unit an RRH unit (RRH = Remote Radio Head) with a connected antenna
may be used to provide wireless coverage in a mobile communication network. When the
RRH unit needs to be replaced at an antenna mast, antennas need to be disconnected
from the old RRH unit and need to be reconnected to the new RRH unit. RF Coaxial Connectors
(RF = Radio Frequency) such as 7/16 DIN connectors for RF cables between the RRH unit
and the antennas usually require a torque controlled mount. Even if the 7/16 connector
fulfils the IP68 specification with a solid particle protection, that provides no
ingress of dust and a complete protection against contact and with a liquid ingress
protection, that provides protection for an immersion into water beyond a depth of
1 m by a hermetical sealing, water may enter a feeder cable, if the new connection
is not assembled by a highly skilled person.
SUMMARY
[0005] A replacement of current AA units or RRH units requires highly skilled service technicians
and/or a considerable amount of work and/or lifting equipment and therefore produces
large replacement costs. Thus, it is an object of the invention to facilitate the
replacement, to reduce an error rate of the replacement process and to reduce replacement
costs in a radio communication network.
[0006] The object is achieved by a first subsystem for an active antenna unit. The first
subsystem contains first connecting means of a detachable connection of the active
antenna unit adapted to connect to second connecting means of a second subsystem for
the active antenna unit, at least one input port at the first connecting means connected
to at least one transmit path for receiving amplified first radio frequency signals
from at least one output port of the second subsystem, means for filtering the amplified
first radio frequency signals in the at least one transmit path, and the at least
one transmit path for providing the amplified and filtered first radio frequency signals
to at least one antenna element. The object is further achieved by the second subsystem
for the active antenna unit. The second subsystem contains at least one transmit path
for radio frequency signals, at least one power amplifier in the at least one transmit
path for generating amplified radio frequency signals, at least one output port connected
to the at least one transmit path at second connecting means for providing the amplified
radio frequency signals to at least one input port of the first subsystem, and the
second connecting means of a detachable connection adapted to connect to first connecting
means of a first subsystem for the active antenna unit. The object is even further
achieved by the antenna array, which contains the first subsystem and the second subsystem.
[0007] The detachable connection may be for example a single plug connection, a single screw
connection, or several plug and/or screw connections. The first connection means may
contain for example a single male connector or several male connectors for electrical
connections between the first subsystem and the second subsystem and the second connection
means may contain for example a single female connector or several female connectors
adapted to connect to the one male connector or the several male connectors. In a
first alternative, the first connection means may contain a single female connector
or several female connectors and the second connection means may contain a single
male connector or several male connectors adapted to connect to the single female
connector or the several female connectors. In a second alternative, the first connection
means may contain a single male connector or several male connectors for a first group
of electrical connections between the first subsystem and the second subsystem and
a single female connector or several female connectors for a second group of electrical
connections between the first subsystem and the second subsystem and the second connection
may contain a single female connector or several female connectors for the first group
of electrical connections and a single male connector or several male connectors for
the second group of electrical connections.
[0008] The embodiments of the invention provide a first benefit of eliminating by the means
for filtering the amplified first radio frequency so-called unwanted out-of-band signals,
which have frequency components outside a frequency band, which is licensed to an
operator of the mobile communication network. Such signals are generated primarily
by a power amplifier in the transmit path of the active antenna unit. Such signals
also contain so-called passive inter-modulation radio frequency signals, which may
be generated at metal surfaces of fabricated connections, of fabricated devices and
the detachable connection between the first subsystem and the second subsystem by
a non-optimal contacting. The embodiments of the invention provide a second benefit
of providing the possibility to exchange the second subsystem without requiring exchanging
the first subsystem, when the active antenna unit shall be modified to transmit radio
frequency signals of a mobile communication standard, which is different to a currently
used mobile communication standard. The embodiments of the invention provide a third
benefit of facilitating a replacement of the active antenna unit, if a device of the
second subsystem shows a failure. In such a case, only the second subsystem needs
to be replaced and the first subsystem can be kept in its original position. The embodiments
of the invention provide a fourth benefit of requiring testing of the first subsystem
regarding a possible emission of the unwanted signals only once after fabrication
of the first subsystem and before installation of the active antenna unit and not
during replacement of the second subsystem. The embodiments of the invention provide
a fifth benefit of not requiring highly skilled technicians for the replacement of
the second subsystem. The first connecting means and the second connection means provide
the possibility of facilitating a separation of the second subsystem from the first
subsystem and an assembly of the second subsystem to the first subsystem by using
the first and the second connecting means without requiring to cut electrical wires
or cables or optical fibres and to weld or to solder the electrical wires or to weld
the optical fibres for repairing the electrical cables and wires or the optical fibres
after a replacement of the second subsystem. Furthermore, all electrical connections
can be verified regarding an optimal operation by a self-test of the second subsystem.
This provides the benefit of not requiring high skilled service technicians for replacing
the second subsystem. The embodiments of the invention provide a sixth benefit of
reducing replacement costs and thereby CAPEX (CAPEX = Capital expenditure) of a radio
communication system.
[0009] According to a preferred embodiment, the means for filtering the amplified first
radio frequency signals is at least one high frequency filter. The at least one high
frequency filter may be for example a single bandpass filter or a combination of multiple
bandpass filters (e.g. a duplex filter). The bandpass filter may provide a bandpass,
which corresponds to a frequency range, which is licensed by an operator of the radio
communication system. The preferred embodiment provides the advantage, that no extra
filter device is required in the transmit path within the first subsystem, in case
of the detachable connection may be located between the high frequency filter of the
first subsystem and an antenna port of the first subsystem.
[0010] According to a further preferred embodiment, the first subsystem (SS1) further contains
at least one output port at the first connecting means connected to at least one receive
path for receiving second radio frequency signals that have been received at the at
least one antenna element, the at least one receive path for providing the received
second radio frequency signals from the at said at least one antenna element to the
at least one output port, and means for providing at the at least one output port
a power level of the received second radio frequency signals within a predefined range
to a power level of the amplified first radio frequency signals at the at least one
input port. Preferably, the predefined range is between -130 dB and -100 dB. Preferably,
the first subsystem further contains in the receive path for the radio frequency signals
a single low noise amplifier or two or more low noise amplifiers connected in series
for providing the power level of the receive path at the first connecting means within
the predefined range. The further preferred embodiment provides the benefit that at
the detachable connection a difference of the power levels in the transmit path and
the receive path is reduced and that a degrading effect of a cross coupling of radio
frequency signals from the transmit path of the active antenna unit to the receive
path of the active antenna unit can be minimized or even eliminated.
[0011] According to an even further preferred embodiment, the first subsystem further contains
the at least one antenna element and the at least one antenna element is connected
to the first subsystem by a non-detachable connection. In known active antenna units
one or several antenna elements are connected to the active antenna units by a detachable
connection, which is located between a radio frequency filter and the one or several
antenna elements. By locating the detachable connection between the one or several
power amplifiers of the second subsystem and the means for attenuating the passive
inter-modulation radio frequency signals of the transmit path of the first subsystem,
the even further preferred embodiment provides the advantage, that passive inter-modulation
radio frequency signals can be only generated at the detachable connection at an input
of the means for attenuating the passive inter-modulation radio frequency signals
and therefore can be attenuated to an uncritical level. When a detachable connection
is used between the radio frequency filter and the one or several antenna elements
as in known active antenna units, no device can be applied for attenuating such passive
inter-modulation radio frequency signals. It is only possible, to measure output signals
of the one or several antenna elements and to adjust the detachable connection until
the passive inter-modulation radio frequency signals are reduced to an uncritical
level. Such a measurement and test procedure requires highly skilled technicians and
takes a long time so that large costs arise, when the interface between the known
active antenna unit and the one or several antenna elements needs to be released and
reconnected.
[0012] According to a further preferred embodiment, the first subsystem fulfils or exceeds
a predefined reliability. The predefined reliability may be for example a maximum
failure rate per year, a maximum mean time between failures or a minimum year over
year return rate. The maximum failure rate per year may be for example 1 percent of
installed first subsystems per year. The failure rate of components or devices depends
on physical or chemical characteristics such as fracture toughness, electric strength,
chemical resistance against aggressive substances, aging resistance of materials such
as rubber or plastic, etc. Other factors, which influence the failure rate of components
or devices of the active antenna unit are temperature, stress, vibration, moisture
and energy-rich radiation such as X-radiation or gamma radiation, cosmic rays or solar
wind. Inner factors of the active antenna unit, which also influence the failure rate
are heat losses, mechanical internal stress, electrical current density and electrical
field strength. Characteristics of a device which influence the reliability of the
device are for example a working temperature range. Heat sources, which influence
the working temperature of a device are the outdoor temperature and internal conversion
process, which transfer electromagnetic energy into thermal energy. When the device
is operated outside a predefined working temperature range or at an end of the predefined
working temperature range, a probability for a device failure may increase.
[0013] The devices of the first subsystem are subject to a smaller thermal stress than the
devices of the second subsystem, because a low noise amplifier of the first subsystem
is usually operated at about 85 °C, whereas a high power amplifier of the second subsystem
is operated above 100 °C. Preferably, devices with a low complexity (e.g. small number
of solder joints), with a sufficient robustness against thermal stress and low power
consumption are located within the first subsystem.
[0014] Known active antenna units are fabricated as a single subsystem which is located
in a casing or housing. Even if most devices of the single subsystem achieve the predefined
reliability, the complete active antenna unit needs to be replaced, when a single
device such as a high power amplifier of the transmit path fails. Therefore, the further
preferred embodiment provides the advantage, that all devices of the first subsystem
does not need to be replaced if for example the power amplifier of the transmit path
within the second subsystem is defect or does not fulfill the required performance
anymore. It is only required to replace the second subsystem because the first subsystem
should work without outage time until the end of the product cycle of the active antenna
unit. First devices of the first subsystem may be high-quality devices, which may
have been tested comprehensively before installation regarding a fulfilment of the
predefined reliability. Therefore, the one or several first devices have a long operation
time without any failures preferably within the product cycle of the active antenna
unit. Second devices of the second subsystem may be low-quality devices, which may
have been installed without any long testing procedure.
[0015] According to an even further preferred embodiment, the second subsystem further contains
a single power supply or several power supplies or a single voltage transformer or
several voltage transformers as known from conventional active antenna units for devices
of the first subsystem such as low noise power amplifiers. The even further preferred
embodiment provides the benefit of enabling the repair of the power supplies and voltage
transformers supplying the first subsystem by simply replacing the second subsystem.
This provides the further benefit, that the first subsystem does not contain any error-prone
power supplies or voltage transformers..
[0016] According to a further preferred embodiment, the second subsystem has a weight below
or equal to a predefined maximum weight a human is allowed to carry according to a
legal requirement. Preferably, the predefined maximum weight may be a so-called one
man lift weight such as 20 kg or 30 kg. A weight of known active antenna units exceeds
a weight, which a single person can carry or is allowed to carry according to legal
requirements. A split of the active antenna unit in the first subsystem and the second
subsystem and the weight of the second subsystem below or equal to the predefined
maximum weight facilitates a replacement of the second subsystem by a single technician
without any lifting equipment, if the second subsystem shows a failure or needs to
be replaced for a system upgrade such an upgrade to a new radio communication standard.
[0017] Further advantageous features of the invention are defined and are described in the
following detailed description of the invention.
BRIEF DESCRIPTION OF THE FIGURE
[0018] The embodiments of the invention will become apparent in the following detailed description
and will be illustrated by accompanying figure given by way of non-limiting illustrations.
Figure 1 shows a block diagram of an active antenna unit according to an embodiment
of the invention.
Figure 2 shows three lateral views of the active antenna unit according to the embodiment
of the invention.
DESCRIPTION OF THE EMBODIMENTS
[0019] Various example embodiments will now be described more fully with reference to the
accompanying drawing in which an example embodiment is illustrated. In the figure,
the thicknesses of lines, layers and/or regions may be exaggerated for clarity.
[0020] Accordingly, while example embodiments are capable of various modifications and alternative
forms, embodiments thereof are shown by way of example in the figure and will herein
be described in detail. It should be understood, however, that there is no intent
to limit example embodiments to the particular forms disclosed, but on the contrary,
example embodiments are to cover all modifications, equivalents, and alternatives
falling within the scope of the invention. Like numbers refer to like or similar elements
throughout the description of the figure.
[0021] It will be understood that when an element is referred to as being "connected" or
"coupled" to another element, it can be directly connected or coupled to the other
element or intervening elements may be present. In contrast, when an element is referred
to as being "directly connected" or "directly coupled" to another element, there are
no intervening elements present. Other words used to describe the relationship between
elements should be interpreted in a like fashion (e.g., "between" versus "directly
between," "adjacent" versus "directly adjacent," etc.).
[0022] The terminology used herein is for the purpose of describing particular embodiments
only and is not intended to be limiting of example embodiments. As used herein, the
singular forms "a," "an" and "the" are intended to include the plural forms as well,
unless the context clearly indicates otherwise. It will be further understood that
the terms "comprises," "comprising," "includes" and/or "including," when used herein,
specify the presence of stated features, integers, steps, operations, elements and/or
components, but do not preclude the presence or addition of one or more other features,
integers, steps, operations, elements, components and/or groups thereof.
[0023] Unless otherwise defined, all terms (including technical and scientific terms) used
herein have the same meaning as commonly understood by one of ordinary skill in the
art to which example embodiments belong. It will be further understood that terms,
e.g., those defined in commonly used dictionaries, should be interpreted as having
a meaning that is consistent with their meaning in the context of the relevant art
and will not be interpreted in an idealized or overly formal sense unless expressly
so defined herein. Figure 1 shows a block diagram of an active antenna unit AA for
transmitting and receiving radio frequency signals via antenna elements AE1 to AE4.
The active antenna unit AA is shown for an FDD transmission scheme (FDD = Frequency
Division Duplex). In an alternative, by replacing duplex filters DF1, DF2 as shown
in Figure 1 with single filters and switches as known in the prior art, the active
antenna unit may be modified to be used for a TDD transmission scheme (TDD = Time
Division Duplex).
[0024] The embodiment is exemplarily shown with four antenna elements AE1 to AE4 and antenna
elements AE1, AE2 are used for a transmission of radio frequency signals and all four
antenna elements AE1 to AE4 are used for a reception of radio frequency signals. In
further alternatives, the active antenna unit AA may be adapted for transmitting the
radio frequency signals via a single antenna element, via four antenna elements by
adding two additional transmit paths with corresponding devices or via more than four
antenna elements by adding more than two additional transmit paths with corresponding
devices. In an even further alternative, the active antenna unit AA may be adapted
for receiving the radio frequency signals via a single antenna element, via two antenna
elements or via more than four antenna elements by adding additional receive paths
with corresponding devices.
[0025] The active antenna unit AA is split into a first subsystem SS1 and a second subsystem
SS2. This means, the active antenna unit AA contains the first subsystem SS1, the
second subsystem SS2 and a detachable connection between the first subsystem SS1 and
the second subsystem SS2. The detachable connection is adapted to separate the second
subsystem SS2 from the first subsystem SS1 and to assemble the second subsystem SS2
to the first subsystem SS1 and may contain for example one or several plug connections
for electrical connections EC1 to EC10 between the first subsystem SS1 and the second
subsystem SS2. The electrical connections EC1 to EC10 may be provided for example
by cables such as coaxial cables, which are connected to corresponding ports of the
first subsystem SS1 and the second subsystem SS2.
[0026] Alternatively, the detachable connection may contain one or several screw connections
for the electrical connections EC1 to EC10 between the first subsystem SS1 and the
second subsystem SS2. According to further alternatives the electrical connections
EC1 to EC10 between the first subsystem SS1 and the second subsystem SS2 may be provided
by a mixture of one or several plug connections and one or several screw connections.
[0027] The first subsystem SS1 contains first connection means CM1 and the second subsystem
SS2 contains second connection means CM2. The first connection means CM1 may contain
for example a single male connector or several male connectors for the electrical
connections EC1 to EC10 between the first subsystem SS1 and the second subsystem SS2
and the second connection means CM2 may contain for example a single female connector
or several female connectors adapted to connect to the one male connector or the several
male connectors of the first connection means CM1. In a first alternative, the first
connection means CM1 may contain a single female connector or several female connectors
and the second connection means CM2 may contain a single male connector or several
male connectors adapted to connect to the single female connector or the several female
connectors of the first connection means CM1. In a second alternative, the first connection
means CM1 may contain a single male connector or several male connectors for a first
group of the electrical connections EC1 to EC10 between the first subsystem SS1 and
the second subsystem SS2 and a single female connector or several female connectors
for a second group of the electrical connections EC1 to EC10 between the first subsystem
SS1 and the second subsystem SS2 and the second connection means CM2 may contain a
single female connector or several female connectors for the first group of the electrical
connections EC1 to EC10 and a single male connector or several male connectors for
the second group of the electrical connections EC1 to EC10.
[0028] Devices of transmit paths Tx1-SS1, Tx2-SS1 and receive paths Rx1-SS1, Rx2-SS1, Rx3-SS1,
Rx4-SS1 of the first subsystem SS1 between the first connecting means CM1 and antenna
ports OP1-AE1, OP2-AE2, OP3-AE3, OP4-AE4 are preferably located within a first housing
HS1-1 such as a composite plastic and aluminium sheet metal housing. The antenna elements
AE1 to AE4 are preferably located inside a second housing HS1-2 such as a PVC housing
(PVC = polyvinyl chloride) or a fiberglass housing. The second subsystem SS2 is preferably
located within a third housing HS2 such as an aluminium die cast housing. In a further
preferred embodiment, the antenna elements AE1 to AE4 may be connected to the antenna
ports OP1-AE1, OP2-AE2, OP3-AE3, OP4-AE4 of the first subsystem SS1 by non-detachable
connections. Thereby no passive inter-modulation radio frequency signals may be generated.
In case of detachable connections, such passive inter-modulation radio frequency signals
may be generated due to the connections becoming unfasten or untighten.
[0029] The first subsystem SS1 contains within a first transmit path Tx1-SS1 first means
DF1 for filtering amplified first radio frequency signals in the first transmit path
Tx1-SS1. Thereby, unwanted radio frequency signals which may be generated for example
by a non-perfect contacting for electrical connection EC2 between the first contacting
means CM1 and the second contacting means CM2 of the detachable connection due to
passive intermodulation are attenuated or suppressed. The first means DF1 for filtering
the amplified first radio frequency signals may be for example a first duplex filter
DF1 such as shown in Figure 1, which separates a single electrical connection for
transmit signals and receive signals between the first duplex filter DF1 and a first
antenna element AE1 into the first transmit path Tx1-SS1 and a first receive path
Rx1-SS1. The first duplex filter DF1 may contain a band-pass filter, which lets passing
the transmit signals within a frequency band licensed by an operator of a radio communication
system and which attenuates or blocks the transmit signals outside the frequency band.
Instead of the first duplex filter DF1 a single filter may be applied, if the first
antenna element AE1 may be only used for transmitting radio frequency signals. In
case of a TDD application, the first duplex filter DF1 may be replaced by a single
filter such as a single bandpass filter.
[0030] Equally, the first subsystem SS1 contains within a second transmit path Tx2-SS1 second
means DF2 for filtering further amplified first radio frequency signals in the second
transmit path Tx2-SS1. Thereby, further unwanted radio frequency signals, which may
be generated for example by a non-perfect contacting for electrical connection EC6
between the first contacting means CM1 and the second contacting means CM2 of the
detachable connection due to passive intermodulation are attenuated or suppressed.
The second means DF2 for filtering the further amplified first radio frequency signals
may be for example a second duplex filter DF2 such as shown in Figure 1, which separates
a single electrical connection for transmit signals and receive signals between the
second duplex filter DF2 and a second antenna element AE2 into the second transmit
path Tx2-SS1 and a second receive path Rx2-SS1. The second duplex filter DF2 may contain
a band-pass filter, which lets passing the transmit signals within the frequency band
licensed by the operator and which attenuates or blocks the transmit signals outside
the frequency band. Instead of the second duplex filter DF2 a single filter may be
applied, if the second antenna element AE2 may be only used for transmitting radio
frequency signals. In case of a TDD application, the second duplex filter DF2 may
be replaced by a further single filter such as a single bandpass filter.
[0031] The first transmit path Tx1-SS1 contains an electrical connection between a first
input port IP1-SS1 located at the first contacting means CM1 and the first duplexer
DF1, the first duplexer DF1, an electrical connection between the first duplexer DF1
and a first directional coupler DC1, the first directional coupler DC1, an electrical
connection between the first directional coupler DC1 and a first antenna port OP1-AE1
for the first antenna element AE1. Preferably, an electrical connection between the
first antenna port OP1-AE1 and the first antenna element AE1 may be a fixed non-detachable
connection. This means, the first antenna element AE1 may be a part of the first subsystem
SS1.
[0032] The first receive path Rx1-SS1 contains the electrical connection between the first
antenna port OP1-AE1 and the first directional coupler DC1, the first directional
coupler DC1, the electrical connection between the first directional coupler DC1 and
the first duplex filter DF1, the first duplex filter DF1, preferably an electrical
connection between the first duplex filter DF1 and a first low noise power amplifier
system LNAG1, preferably the first low noise power amplifier system LNAG1, preferably
an electrical connection between the first low noise power amplifier system LNAG1
and a first output port OP1-SS1. The first low noise power amplifier system LNAG1
may contain two low noise power amplifiers connected in serious such as shown in Figure
1. Alternatively, a single low noise power amplifier or a low noise power amplifier
system with more than two low noise power amplifiers may be applied.
[0033] The second transmit path Tx2-SS1 contains an electrical connection between a second
input port IP2-SS1 located at the first contacting means CM1 and the second duplexer
DF2, the second duplexer DF2, an electrical connection between the second duplexer
DF2 and a second directional coupler DC2, the second directional coupler DC2, an electrical
connection between the second directional coupler DC2 and a second antenna port OP2-AE2
for the second antenna element AE2. Preferably, an electrical connection between the
second antenna port OP2-AE2 and the second antenna element AE2 may be a fixed non-detachable
connection. This means, the second antenna element AE2 may be a part of the first
subsystem SS1.
[0034] The second receive path Rx2-SS1 contains the electrical connection between the second
antenna port OP2-AE2 and the second directional coupler DC2, the second directional
coupler DC2, the electrical connection between the second directional coupler DC2
and the second duplex filter DF2, the second duplex filter DF2, preferably an electrical
connection between the second duplex filter DF2 and a second low noise power amplifier
system LNAG2, preferably the second low noise power amplifier system LNAG2, and preferably
an electrical connection between the second low noise power amplifier system LNAG2
and a second output port OP2-SS1. The second low noise power amplifier system LNAG2
may contain two low noise power amplifiers connected in serious such as shown in Figure
1. Alternatively, a single low noise power amplifier or a low noise power amplifier
system with more than two low noise power amplifiers may be applied.
[0035] Preferably, the first subsystem SS1 contains means for providing at the at the first
output port OP1-SS1 and the second output port OP2-SS1 of the receive paths Rx1-SS1
and Rx2-SS1 a power level of the received second radio frequency signals within a
predefined range to a power level of the amplified first radio frequency signals at
the first input port IP1-SS1 and the second input port IP2-SS1 of the transmit paths
Tx1-SS1 and Tx2-SS1. Preferably, the predefined range is between -130 dB and -100
dB. Preferably, the first low noise amplifier system LNAG1 and the second low noise
amplifier system LNAG2 are applied for this purpose of providing at the at the first
output port OP1-SS1 and the second output port OP2-SS1 of the receive paths Rx1-SS1
and Rx2-SS1 the power level of the received second radio frequency signals within
the predefined range.
[0036] The first subsystem SS1 as exemplarily shown in Figure 1 further contains a third
receive path Rx3-SS1 and a fourth receive path Rx4-SS1. The third and the fourth receive
path Rx3-SS1, Rx4-SS1 contain electrical connections between antenna ports OP3-AE3,
OP4-AE4, directional couplers DC3, DC4, electrical connections between the directional
coupler DC3, DC4 and filters F3, F4, the filters F3, F4, preferably electrical connections
between the filters F3, F4 and low noise power amplifier systems LNAG3, LNAG4, preferably
the low noise power amplifier systems LNAG3, LNAG4, and preferably electrical connections
between the low noise power amplifier systems LNAG3, LNAG4 and output ports OP3-SS1,
OP4-SS1. The low noise power amplifier systems LNAG3, LNAG4 may contain two low noise
power amplifiers connected in series such as shown in Figure 1. Alternatively, single
low noise power amplifiers or low noise power amplifier systems with more than two
low noise power amplifiers may be applied. The filters F3, F4 are single bandpass
filters or a combination of multiple bandpass filters.
[0037] The first subsystem SS1 further contains a first switch SW1 enabling access to the
radio frequency signals of the two pairs of directional couplers DC1, DC2 being attached
to the filters DF1 and DF2, a second switch SW2 for enables access to the two pairs
of directional couplers DC3, DC4 being attached to the filters F3 and F4, a first
integrated circuit or a first microcontroller IC1 with a first computer program product
and a second integrated circuit or a second microcontroller IC2 with a second computer
program product. The first computer program product and the second computer program
product may be used for controlling the switches SW1, SW2 and for providing inventory
data for the first subsystem SS1.The first and the second switch SW1, SW2 may be for
example FETs (FET = Field Effect Transistor).
[0038] Preferably, all devices of the first subsystem SS1 fulfill a predefined minimum reliability.
The predefined minimum reliability may be for example a maximum failure rate per year,
a maximum mean time between failures or a minimum year over year return rate. The
maximum failure rate per year may be for example 1 percent of installed first subsystems
per year. Exemplarily, the devices of the first subsystem SS1 fulfill following reliabilities:
The low noise power amplifier systems LNAG1 to LNAG4 fulfill a reliability of 0.003
% per year. The duplex filters DF1, DF2 fulfill a reliability of 0.2% per year. The
filter F3, F4 fulfill a reliability of 0.1% per year. The directional couplers DC1
to DC4 fulfill a reliability of 0.01 % per year. The switches SW1, SW2 fulfill a reliability
of 0.003 % percent per year. The integrated circuits or microcontrollers IC1, IC2
fulfill a reliability of 0.01 % per year. The first and the second computer program
product fulfill a reliability of 1 min outage per year. The reliability of the first
and the second computer program products mainly depend on a complexity of instruction
of the computer program product and an effort, which has been spent for debugging
to test almost all possible combinations of input parameters, which are used by the
computer program product, to avoid a program crash for example in case of a division
by zero.
[0039] Voltage supplies and connections for voltage supply of the devices of the first subsystem
SS1 are not shown in Figure 1 for simplification. Preferably, the first subsystem
SS1 does not contain any voltage supplies and voltage supply is provides by one or
several voltage supplies of the second subsystem SS2.
[0040] The second subsystem SS2 contains a power amplifier system PAS in a first transmit
path Tx1-SS2 and a second transmit path Tx2-SS2. The power amplifier system PAS contains
a first power amplifier P1 and a directional coupler DC5 for the first transmit path
Tx1-SS2 and a second power amplifier P2 for the second transmit path Tx2-SS2 and a
directional coupler DC6 for the second transmit path Tx2-SS2. The directional couplers
DC5, DC6 are used for a pre-distortion of the transmit signals. Instead of the power
amplifier system PAS separate power amplifiers may be applied for the first transmit
path Tx1-SS2 and the second transmit path Tx2-SS2. In further alternatives, two or
more power amplifiers may be applied for the first transmit path Tx1-SS2 and the second
transmit path Tx2-SS2. In even further alternatives, only a single power amplifier
may be contained in the second subsystem SS2, if the second subsystem SS2 contains
only a single transmit path.
[0041] The second subsystem SS2 further may further contain a processing unit PU and two
converters CV1, CV2, which are connected by electrical connections to the processing
unit PU. The converter CV1, CV2 are part of a so-called CPRI (CPRI = Common Public
Radio Interface) for transmitting I/Q samples in a form of electrical or optical signals.
Optical fibers FB1, FB2 may be connected to the converters CV1, CV2. The converters
CV1, CV2 contain optical detectors for converting optical signals into electrical
signals and contain optical emitters such as LEDs (LED = Light Emitting Diode) or
small lasers for converting electrical signals into optical signals. The processing
unit PU is primarily used for controlling an adaptation of the transmit signals for
example by pre-distortion means and/or clipping means.
[0042] Digital transmit signals may be provided from the processing unit PU to a first transmitter
unit TU1 of the first transmit path Tx1-SS2 and to a second transmitter unit TU2 of
the second transmit path Tx2-SS2 (corresponding electrical connections are not shown
in Figure 1 for simplification). The transmitter units TU1, TU2 convert the digital
transmit signals into analogue transmit signals and perform an up mixing from a low
frequency to a high frequency in a range of for example MHz or GHz. Digital receive
signals may be provided from receiver units RU1, RU2, RU3, RU4 to the processing unit
PU (corresponding electrical connections are also not shown in Figure 1 for simplification).
The receiver units RU1, RU2, RU3, RU4 convert analogue receive signals into digital
receive signals and perform a down mixing from the high frequency in the range of
for example MHz or GHz to a low frequency as known from active antenna units in the
prior art.
[0043] The second subsystem SS2 further contains with respect to the first transmit path
Tx1-SS2, the first transmitter unit TU1, an electrical connection from the first transmitter
unit TU1 to the power amplifier system PAS, the power amplifier system PAS, and an
electrical connection from the power amplifier system PAS to a first output port OP1-SS2.
[0044] Equally, the second subsystem SS2 further contains with respect to the second transmit
path Tx2-SS2, the second transmitter unit TU2, an electrical connection from the second
transmitter unit TU2 to the power amplifier system PAS, the power amplifier system
PAS, and an electrical connection from the power amplifier system PAS to a second
output port OP2-SS2.
[0045] The second subsystem SS2 further contains with respect to receive paths Rx1 -SS2,
Rx2-SS2, Rx3-SS2, Rx4-SS2 electrical connections from input ports IP1-SS2, IP2-SS2,
IP3-SS2, IP4-SS2 to attenuators AT1, AT2, AT3, AT4, the attenuators AT1, AT2, AT3,
AT4, electrical connections from the attenuators AT1, AT2, AT3, AT4 to intermediate
amplifiers IA1, IA2, IA3, IA4, the intermediate amplifiers IA1, IA2, IA3, IA4, electrical
connections from the intermediate amplifiers IA1, IA2, IA3, IA4 to the receiver units
RU1, RU2, RU3, RU4 and the receiver units RU1, RU2, RU3, RU4. The attenuators AT1,
AT2, AT3, AT4 are used for enabling a power level adjustment of the receive signals
at an input of the intermediate amplifiers IA1, IA2, IA3, IA4.
[0046] According to a first alternative, the attenuators AT1, AT2, AT3, AT4 may be located
in the first subsystem SS1 instead of being located in the second subsystem SS2. According
to a second alternative, the attenuators AT1, AT2, AT3, AT4, the electrical connections
between the attenuators AT1, AT2, AT3, AT4 and the intermediate amplifiers IA1, IA2,
IA3, IA4 and the intermediate amplifiers IA1, IA2, IA3, IA4 may be located in the
first subsystem SS1 instead of being located in the second subsystem SS2.
[0047] The second subsystem SS2 as exemplarily shown in Figure 1 further contains a switch
SW3, a generator TG for providing a test signal and a test receiver TR. The switch
SW3, the generator TG and the test receiver TR are applied for predistortion, self-testing
of the receive paths Rx1-SS1 to Rx4-SS1 and Rx1-SS2 to Rx4-SS2 and the transmit paths
Tx1-SS1, Tx2-SS1, Tx1-SS2, Tx2-SS2 including the first connecting means CM1 and the
second connecting means CM2, and calibration of the receive paths Rx1-SS1 to Rx4-SS1
and Rx1-SS2 to Rx4-SS2 and the transmit paths Tx1-SS1, Tx2-SS1, Tx1-SS2, Tx2-SS2.
[0048] Electrical connections between the processing unit PU and the generator TG and between
the processing unit PU and the test receiver TR are not shown in Figure 1 for simplification.
[0049] The second subsystem SS2 further contains a single power supply or a single voltage
transformer or several voltage supplies or several voltage transformers for the devices
contained in the first subsystem SS1 and for the devices contained in the second subsystem
SS2. This means, that no power supplies or voltage transformer are required within
the first subsystem SS1. The devices of the first subsystem SS1 are supplied by the
power supplies or voltage transformers of the second subsystem SS2 via corresponding
electrical connections via the first and the second connections means CM1, CM2. Such
electrical connections are not shown in Figure 1 for simplification.
[0050] In addition an inlet filter with surge protection may protect the power supplies
or voltage transformers of the second subsystem SS2 and may reduce at a power inlet
switching noise. Isolated DC/DC converters are combined in series with one or several
non-isolated DC/DC converters. This means for example that the first power amplifier
P1 and the second power amplifier P2 may be directly supplied by one isolated DC/DC
converter -48V to 28V, the other devices of the first subsystem SS1 and the second
subsystem may be supplied by one isolated DC/DC converter -48V to 5V plus several
non-isolated DC/DC converters providing lower voltages. The power supply of the low
noise power amplifiers systems LNAG1 to LANG2 of the first subsystem SS1 is derived
from one of power rails of the second subsystem SS2. The second subsystem SS2 contains
one or several devices for current limitation and supply voltage filtering supplying
the first and the second low noise amplifier systems LNAG1, LNAG2 of the first subsystem
SS1. Such well-known voltage components may have a high failure risk and are therefore
preferably located only within the second subsystem SS2.
[0051] The first subsystem SS1 may have a first weight, which exceeds a predefined maximum
weight, which is also called a one man lift weight. The one man lift weight is usually
given by legal requirements. The one man lift weight may be for example 20 kg or 30
kg. The second subsystem SS2 preferably has a second weight, which is equal to or
below the one man lift weight. The second weight may be adjusted by shifting functional
units such as the attenuators AT1 to AT4 from the second subsystem SS2 to the first
subsystem SS1.
[0052] Figure 2a) shows a first lateral view of the active antenna unit AA on a side of
the active antenna unit AA, where the antenna elements AE1 to AE4 are located. Figure
2b) shows a second lateral view (rotated by 90° along a longitudinal axis of the active
antenna unit AA with respect to Figure 2a), which shows a preferred location of the
first subsystem SS1 and the second subsystem SS2. Figure 2c) shows a third lateral
view (rotated by 90° along a longitudinal axis of the active antenna unit AA with
respect to Figure 2b), which also shows the preferred location of the first subsystem
SS1 and the second subsystem SS2.
[0053] The description and drawing merely illustrate the principles of the invention. It
will thus be appreciated that those skilled in the art will be able to devise various
arrangements that, although not explicitly described or shown herein, embody the principles
of the invention and are included within its spirit and scope. Furthermore, all examples
recited herein are principally intended expressly to be only for pedagogical purposes
to aid the reader in understanding the principles of the invention and the concepts
contributed by the inventor(s) to furthering the art, and are to be construed as being
without limitation to such specifically recited examples and conditions. Moreover,
all statements herein reciting principles, aspects, and embodiments of the invention,
as well as specific examples thereof, are intended to encompass equivalents thereof.
[0054] Functional blocks denoted as "means for ..." (performing a certain function) shall
be understood as functional blocks comprising circuitry that is adapted for performing
or to perform a certain function, respectively. Hence, a "means for s.th." may as
well be understood as a "means being adapted or suited for s.th.". A means being adapted
for performing a certain function does, hence, not imply that such means necessarily
is performing the function (at a given time instant).
[0055] The functions of the various elements shown in the Figures, including any functional
blocks labeled as "means", "means for connecting", "connection means", "means for
attenuating", "predistortion means", "clipping means" etc., may be provided through
the use of dedicated hardware, such as "a connector", "an attenuator", "a filter",
"a clipping unit", "a predistortion unit" etc. as well as hardware capable of executing
software in association with appropriate software. Moreover, any entity described
herein as "means", may correspond to or be implemented as "one or more modules", "one
or more devices", "one or more units", etc. When provided by a processor, the functions
may be provided by a single dedicated processor, by a single shared processor, or
by a plurality of individual processors, some of which may be shared. Moreover, explicit
use of the term "processor" or "controller" should not be construed to refer exclusively
to hardware capable of executing software, and may implicitly include, without limitation,
digital signal processor (DSP) hardware, network processor, application specific integrated
circuit (ASIC), field programmable gate array (FPGA), read only memory (ROM) for storing
software, random access memory (RAM), and non volatile storage. Other hardware, conventional
and/or custom, may also be included. Similarly, any switches shown in the Figures
are conceptual only. Their function may be carried out through the operation of program
logic, through dedicated logic, through the interaction of program control and dedicated
logic, or even manually, the particular technique being selectable by the implementer
as more specifically understood from the context.
[0056] It should be appreciated by those skilled in the art that any block diagram herein
represent conceptual views of illustrative circuitry embodying the principles of the
invention.
1. A first subsystem (SS1) for an active antenna unit (AA), said first subsystem (SS1)
comprises:
- first connecting means (CM1) of a detachable connection of said active antenna unit
(AA) adapted to connect to second connecting means (CM2) of a second subsystem (SS2)
for said active antenna unit (AA),
- at least one input port (IP1-SS1, IP2-SS1) at said first connecting means (CM1)
connected to at least one transmit path (Tx1-SS1, Tx2-SS1) for receiving amplified
first radio frequency signals from at least one output port (OP1-SS2, OP2-SS2) of
said second subsystem (SS2),
- means (DF1, DF2) for filtering said amplified first radio frequency signals in said
at least one transmit path (Tx1-SS1, Tx2-SS1), and
- said at least one transmit path (Tx1-SS1, Tx2-SS1) for providing said amplified
and filtered first radio frequency signals to at least one antenna element (AE1, AE2).
2. First subsystem (SS1) according to claim 1, wherein said means (DF1, DF2) for filtering
said amplified first radio frequency signals is at least one high frequency filter.
3. First subsystem (SS1) according to claim 2, wherein said at least one high frequency
filter is a single bandpass filter.
4. First subsystem (SS1) according to any of the preceding claims, wherein said first
subsystem (SS1) further comprises:
- at least one output port (OP1-SS1, OP2-SS1) at said first connecting means (CM1)
connected to at least one receive path (Rx1-SS1, Rx2-SS1) for receiving second radio
frequency signals that have been received at said at least one antenna element (AE1,
AE2),
- said at least one receive path (Rx1-SS1, Rx2-SS1) for providing said received second
radio frequency signals from said at said at least one antenna element (AE1, AE2)
to said at least one output port (OP1-SS1, OP2-SS1), and
- means (LNAG1, LNAG2) for providing at said at least one output port (OP1-SS1, OP2-SS1)
a power level of said received second radio frequency signals within a predefined
range to a power level of said amplified first radio frequency signals at said at
least one input port (IP1-SS1, IP2-SS1).
5. First subsystem (SS1) according to claim 4, wherein said predefined range is between
-130 dB and
- 100 dB.
6. First subsystem (SS1) according to claim 4 or claim 5, wherein said means (LNAG1,
LNAG2) for providing said power level of said received second radio frequency signals
within said predefined range is at least one low noise amplifier (LNAG1, LNAG2).
7. First subsystem (SS1) according to any of the preceding claims, wherein said first
subsystem (SS1) further comprises said at least one antenna element (AE1, AE2) and
wherein said at least one antenna element (AE1, AE2) is connected to said first subsystem
(SS1) by a non-detachable connection.
8. First subsystem (SS1) according to any of the preceding claims, wherein said first
subsystem (SS1) fulfils or exceeds a predefined reliability.
9. First subsystem (SS1) according to claim 8, wherein said predefined reliability is
either of the following: a maximum failure rate per year, a maximum mean time between
failures, a minimum year over year return rate.
10. First subsystem (SS1) according to claim 9, wherein said maximum failure rate per
year is 1 percent of installed first subsystems per year.
11. A second subsystem (SS2) for an active antenna unit (AA), said second subsystem (SS2)
comprises:
- at least one transmit path (Tx1-SS2, Tx2-SS2) for radio frequency signals,
- at least one power amplifier (P1, P2) in said at least one transmit path (Tx1-SS2,
Tx2-SS2) for generating amplified radio frequency signals,
- at least one output port (OP1-SS2, OP2-SS2) connected to said at least one transmit
path (Tx1-SS2, Tx2-SS2) at second connecting means (CM2) for providing said amplified
radio frequency signals to at least one input port (IP1-SS1, IP2-SS1) of said first
subsystem (SS1), and
- said second connecting means (CM2) of a detachable connection adapted to connect
to first connecting means (CM1) of a first subsystem (SS1) for said active antenna
unit (AA).
12. Second subsystem (SS2) according to claim 11, wherein said second subsystem (SS2)
further comprises at least one voltage transformer or power supply for said first
subsystem (SS1).
13. Second subsystem (SS2) according to claim 11 or claim 12, wherein said second subsystem
(SS2) has a weight below or equal to a predefined maximum weight a human is allowed
to carry according to a legal requirement.
14. Second subsystem (SS2) according to claim 13, wherein said predefined maximum weight
is 20 kg or 30 kg.
15. An active antenna unit (AA) comprising a first subsystem (SS1) according to any of
the claims 1 to 10 and a second subsystem (SS2) according to any of the claims 11
to 14.