Active circulator
TECHNICAL FIELD
The present invention relates to the field of circulators in microwave systems
such as Active Electronically Scanned Antenna (AESA) systems.
BACKGROUND
A circulator is in general a three-port device finding its place in all microwave
systems, e.g. in AESA-systems and their associated Transmit/Receivemodules
(T/R-modules) with the function to direct a signal flow from a
transmitter to the antenna or to direct a signal flow from the antenna to the
receiver. This is sometimes also described as switching between transmit
and receive modes. The circulator can also have an additional function to
work as a matching device between poorly matched functional blocks, e.g. as
a matching device between the antenna and the transmitter or receiver. The
circulator is located at the end of the T/R-module, close to the antenna. In
addition to the circulator component there are aiso separate components as
the power amplifier, PA, for the transmitted signal and the low noise amplifier,
LNA, for the received signal. All these three components, often called a frontend
arrangement of the T/R module, require a substantial area on a circuit
bord.
By tradition the circulator itself is a design, based on ferrite disks and a bias
magnet. This building practice result in a large occupying area with special
mounting requirements. In addition it attenuates RF signals. Ferrite based
circulators are also narrowband components occupying a large building area
(Area= 250 - 400 mm2) . Together with the PA and LNA components, the area
of this solution for a front-end arrangement is large. When the term RF-signal
is used it includes all types of microwave signals.
Figure 1 shows a conventionel front-end arrangement with a Power Amplifier,
PA 101 , connected to a first port 102 of a circulator 103. A second port 04 of
the circulator is connected via a limiter 105 to a Low Noise Amplifier, LNA,
106. A third port 107 of the circulator is connected to an antenna 108. The
circufator is thus a three port device connecting the PA to the antenna when
the antenna is working in the transmit mode and connecting the antenna, via
the fimiter, to the LNA when the antenna is operating in the receive mode.
The limiter is protecting the LNA from high amplitudes of receievd energy.
US 2009/0286492 A 1 presents a solution where the circulator is replaced by
a semiconductor switch using Gallium Nitride (GaN) transistors. This solution
however requires a separate component for the switch and at least one
component for the LNA and PA, thus taking up a large building area.
There is thus a need for a solution providing a front-end arrangement for T/Rmodules
with at least reduced size and weight.
SUMMARY
The object of the invention is to reduce at least some of the mentioned
deficiencies with prior art solutions and to provide:
• an active circuiator for a microwave system and
• a method to manufacture an active circulator for a microwave system
to solve the problem to achieve a front-end arrangement for T/R-modules
with reduced size and weight.
The object is achieved by providing an active circulator for a microwave
system. Said microwave system comprises at least one front-end
arrangement. Each front-end arrangement comprises a power amplifier
function arranged to deliver an ampiified output signal via a circulator function
to an antenna in a transmit mode. A low noise amplifier function is arranged
to amplify an input signal from the antenna via the circulator function in a
receive mode. The circulator function is arranged to direct a signal flow
between the transmit and receive modes wherein each front-end
arrangement comprises one active circulator. Said active circulator
comprises the power amplifier function, the low noise amplifier function and
the circulator function of directing a signal flow, said three functions
integrated into one module.
The object is further achieved by providing a method to manufacture an
active circulator for a microwave system. Said microwave system using at
least one front-end arrangement. Each front-end arrangement has a power
amplifier function arranged to deliver an amplified output signal via a
circulator function to an antenna in a transmit mode. A low noise amplifier
function is arranged to amplify an input signal from the antenna via the
circulator function in a receive mode. The circulator function is arranged to
direct a signal flow between the transmit and receive modes wherein the
active circulator is manufactured as one module with the power amplifier
function, the low noise amplifier function and the circulator function of
directing a signal flow, said three functions for one front-end arrangement
thus being integrated into one module.
In one example of the active circulator of the invention the power amplifier
function and the low noise amplifier function of the active circulator are
arranged as a Distributed Power Amplifier, DPA, and as a Distributed Low
Noise Amplifier, DLNA, thus achieving a broad band performance. A
distributed amplifier comprises at least two amplifiers connected in parallel
between two transmission lines, one transmission line comprising an input
port to the distributed amplifier and the other transmission line comprising an
output port of the distributed amplifier.
By arranging the amplifier functions as distributed amplifiers, a distributed
amplification of the RF-signal is accomplished. The distributed amplification
principle has the advantage of inherently being very broad band and the
possibility of a bandwidth of at least one decade can be achieved with a
substantially constant gain over the bandwidth. A typical example of the
invention can have a bandwidth of 3-40 GHz but also broader bandwidths are
possible. With this configuration of the amplifier function, portions of the RFsignal
are successively tapped from the transmission line comprising the
input port of the amplifier function to the transmission line comprising the
output port of the amplifier function. The principle of the distributed
amplification can however also be applied to amplifier functions of the
invention in applications where a bandwidth less than one decade is
sufficient.
in one example of the active circulator of the invention, the active circulator is
a Monolithic Microwave integrated Circuit, MMIC, module.
In one example of the active circulator of the invention the MMIC module is
based on Gallium Nitride, GaN, semiconductor technology.
In one example of the method to manufacture an active circulator for a
microwave system the active circulator is manufactured as a Monolithic
Microwave Integrated Circuit, MMIC, module.
In one example of the method to manufacture an active circulator for a
microwave system the MMIC module is manufactured using Gallium Nitride,
GaN, semiconductor technology.
Further advantages are achieved if the invention is also given one or several
characteristics according to the dependent claims not mentioned above. This
will be further described below.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 schematically shows a prior art front-end arrangement.
Figure 2 schematically shows an example of an active circulator according to
the invention.
Figure 3 schematically shows examples of amplifiers used in the active
circulator.
Figure 4 schematically shows an example of an amplifier with two layers of
sub amplifiers used in the active circulator.
Figure 5 schematically shows an example of a realization of an antenna
transmission line.
DETAILED DESCRIPTION
The invention will now be described with reference to the enclosed drawings.
Figure 1 has already been described in the background part.
The active circulator of the invention can e.g. be used as a front-end
arrangement in a microwave system said microwave system comprising at
least one front-end arrangement. Each front-end arrangement comprises a
power amplifier function arranged to deliver an amplified output signal via a
circulator function to an antenna in a transmit mode, and a low noise
amplifier function arranged to amplify an input signal from the antenna via the
circulator function in a receive mode. The circulator function is arranged to
direct a signal flow between the transmit and receive modes, wherein each
front-end arrangement comprises one active circulator, said active circulator
comprises the power amplifier function, the low noise amplifier function and
the circulator function of directing a signal flow, said three functions
integrated into one module.
An example of an active circulator 201 shall now be described in detail with
reference to figure 2. The active circulator comprises an output transmission
line 202, an antenna transmission line 203 and an input transmission line 204
arranged in parallel, with the antenna transmission line located between the
output transmission line and the input transmission line. The transmission
lines have two ends, a first end and second end, and are arranged to extend
between a first side 205 and a second side 206 of the active circulator with
their first ends located at the first side and the second ends at the second
side of the active circulator.
The output transmission line 202 comprises a transmit input port TXin
connected to the first end at the first side 205 and a first termination
impedance 207 connected to the second end at the second side 206.
The antenna transmission line 203 comprises a second termination
impedance 208 connected to the first end at the first side 205 and an
antenna port ANT connected to the second end at the second side 206. An
antenna 2 10 suitable for the application is connected to the antenna port.
The active circulator of the invention can be applied to any type of antenna
suitable for the intended application. The antenna port also serves as an
RXin port, i.e. it receives an input signal from the antenna and as a TXout
port, i.e. it connects a signal from the power amplifier function to the antenna.
The input transmission line 204 comprises a receive output port RXout
connected to the first end at the first side 205 and a third termination
impedance 209 connected to the second end at the second side 206.
The power amplifier function and the low noise amplifier function of the active
circulator are preferably arranged as a Distributed Power Amplifier (DPA) and
as a Distributed Low Noise Amplifier (DLNA) thus achieving a broad band
performance as described in the Summary part above. A distributed amplifier
comprises at least two amplifiers A to A m , Ar, to A m, connected in parallel
between two transmission lines, one transmission line comprising an input
port to the distributed amplifier and the other transmission line comprising an
output port of the distributed amplifier. In the example of figure 2 the
Distributed Power Amplifier (DPA) comprises at least two transmit amplifiers
At,, connected in parallel between the output transmission line 202 and the
antenna transmission line 203 and the Distributed Low Noise Amplifier
(DLNA) comprises at least two receive amplifiers Ar,i connected in parallel
between the antenna transmission line and the input transmission line. The
index i being an integer raising index ranging from 1 to m.
The termination impedances are connected to a common reference plane
such as a ground plane. The termination impedances have the function of
tuning both the DPA and the DLNA for most efficient signal flow {flat gain
over bandwidth). The associated resistance values for the termination
impedances are usually in the range of 20-80 ohms, but this is merely a
typical example, not limiting the scope of the invention.
Each transmission line is divided in transmission line sections T t, to T tm+ ,
T a, i to T a, + and T to T r,m+ for the output transmission line, the antenna
transmission tine and the receive transmission line respectively. The
numbering, denoted with the second index running from 1 to m+1 , of the
transmission line sections starts from the first side of the active circulator.
The amplifiers have an input terminal and an output terminal. Each point
between two transmission line sections of the output transmission line, here
defined as a first starting point, is connected to the input terminal of one
transmit amplifier via a first input matching line section 210 and the output
terminal of this transmit amplifier is connected, via a first output matching line
section 2 11, to a point, here defined as a first end point, between two
transmission line sections of the antenna transmission line having the same
second index numbers as the two transmission line sections surrounding the
first starting point.
Each point between two transmission line sections of the antenna
transmission line, here defined as a second starting point, is connected to the
input terminal of one receive amplifier via a second input matching line
section 212 and the output terminal of this receive amplifier is connected, via
a second output matching line section 213, to a point, here defined as a
second end point, between two transmission line sections of the input
transmission ine having the same second index numbers as the two
transmission line sections surrounding the second starting point in this case
the first end point is the same point as the second starting point. The transmit
and receive amplifiers are thus arranged in a matrix having m columns and
two rows, a transmit row and a receive row.
Each transmission line section has a certain length and width which affects
the impedance and time delay of each transmission line section. For practical
reasons the length of the transmission line sections are normally the same
and the impedance is changed by varying the width of the transmission line
sections. The matching line sections can be varied in the same way as the
transmission line sections in order to match the amplifiers to the transmission
lines. The impedance values of the transmission line sections and the
matching line sections are usually higher than 50 ohms, typically in the range
of 50-90 ohms, but this is merely a typical example, not limiting the scope of
the invention.
The active circulator thus has three ports:
• an antenna port ANT for connection to the antenna, this port being a
common port for the output signal from the power amplifier function
TXout and for the input signal from the antenna RXin,
• a transmit in port TXin arranged to receive an input signal to the power
amplifier function and
• a receive out port RXout arranged to output a signal from the low
noise amplifier function.
The theory of operation in transmit mode can then be explained as follows
with reference to the example of figure 2. The power amplifier, PA, has an
input RF-port, TXin, and an output RF-port, TXout. An incoming wave at the
TXin port travels in the direction towards the TXout port aiong the output
transmission line 202 of impedance, Za, is successively tapped and amplified
at three locations through the transmit amplifiers and fed to the antenna
transmission line of impedance, Zb, where the amplified portions of the
incoming wave travels towards the TXout port and adds up as an output
signal entering the output port, TXout. This circuit arrangement is, as
mentioned above, called a distributed amplifier, in this case a distributed
power amplifier, DPA. in transmit mode, the circuit arrangement in the upper
part (with the receive amplifiers), is turned off by using a control voltage, as
will be further explained.
The theory of operation in receive mode can then be explained as follows
with reference to the example of figure 2 . The low noise amplifier, LNA, has
an input RF-port, RXin, and an output RF-port, RXout. An incoming wave at
the RXin port travels in the direction towards the RXout port along the
antenna transmission line of impedance, Zb, is successively tapped and
amplified at three locations through the receive amplifiers and fed to the input
transmission line of impedance, Zc, where the amplified portions of the
incoming wave travels towards the RXout port and adds up as an output
signal entering the output port, RXout. This circuit arrangement is called a
distributed amplifier, in this case a distributed low noise amplifier, DLNA. In
receive mode, the circuit arrangement in the lower part (with the transmit
amplifiers), is turned off by using a control voltage, as will be explained.
The two RF-port notations, RXin and TX Ut , are actually the same physical
port as the antenna port, ANT. The different notations are just used to
illustrate the two modes of operation, receive and transmit.
The proposed circuit arrangement can be implemented in several ways.
Depending on the semiconductor technology used in the implementation,
different characteristics can be obtained. In using a GaAs semiconductor
technology, a substantial bandwidth of both the power amplifier function and
the low noise amplifier function would be achieved.
With the GaN semiconductor technology it is possible to achieve, over and
above a broad bandwidth, also a higher output power, as this technology
typically produces a power density, referring to transistor size, of around 5-
6W7mm. In addition, this semiconductor technology has an inherent property
of very high breakdown voltages. This property has resulted in circuits, e.g.
robust low noise amplifiers, that can withstand very high voltage swings at
transistor level and that can be used in distributed low noise amplifiers. This
makes a separate receiver limiter circuit redundant. Hence, the most relevant
semiconductor technology is gallium nitride (GaN) and its application in
Transmit/Receive-modules, T/R-modules. The frequency band of main
interest for the invention is 2 - 18 GHz. The principle of the invention is
however not limited to the use of the described semiconductor technology
and the exemplified frequency range, but also other suitable semiconductor
technoiogies can be used and the invention can be adapted also to other
frequency ranges.
An advantage of the invention is that in one Monolithic Microwave Integrated
Circuit, MMIC, module, based on e.g. GaN semiconductor technology it is
possible to integrate the low noise amplifier (LNA), the power amplifier (PA)
and the circulator function of directing a signal flow between transmit mode
(TX) and receive mode (RX), with good isolation over a large bandwidth. The
semiconductor area of the active circulator can in one example of the
invention be around 25 times smaller in comparison with the design approach
using ferrite based circulators and separate designs of PA and LNA.
The amplifier functions of the active circulator, receive and transmit
amplifiers, can be accomplished by any conventional means suitable for
integration into a module such as e.g. a Monolithic Microwave integrated
Circuit, MMIC, module. Figure 3 schematically shows some suitable amplifier
realizations of amplifiers 300. in figure 3a the amplifier 300 comprises a first
transistor 301 and a second transistor 302 connected in a well known
common gate/common source combination where the gate, G, of the first
transistor and the source, S, of the second transistor is connected to a
reference plane such as ground. The input terminal 303 of the amplifier is
connected to the source 304 of the first transistor. The output terminal 305 of
the amplifier is connected to the drain terminal 306 of the second transistor.
The gate terminal 308 of the second transistor is connected to the drain
terminal 307 of the first transistor. A first capacitor 309 is inserted between
the gate terminal of the first transistor and the ground, making current control
possible.
n figure 3b the amplifier 300 comprises a third transistor 310 and a fourth
transistor 3 11 connected in a well known common source/common gate
combination where the gate, G, of the fourth transistor and the source, S, of
the third transistor is connected to a reference plane such as ground. The
input terminal 312 of the amplifier is connected to the gate 313 of the third
transistor. The output terminal 314 of the amplifier is connected to the drain
terminal 3 15 of the fourth transistor. The source terminal 316 of the fourth
transistor is connected to the drain terminal 317 of the third transistor. A
second capacitor 318 is inserted between the gate terminal of the fourth
transistor and the ground, making current control possible.
The amplifier function accomplished in the realizations according to figures
3a and 3b are advantageous from an isolation point of view as it improves
the isolation between transmit and receive function. This is due to the fact
that two transistors are used to realize the amplifier function, having the
effect of a "double isolation" between the transmission lines when the DPA or
DLNA is turned off.
Figure 3c shows a common source, single transistor solution with a fifth
transistor 320 having the source, S, connected to a reference plane such as
ground. The input terminal 321 of the amplifier is connected to the gate 322
of the fifth transistor and the drain 323 is connected to the output terminal
324 of the amplifier.
The circulator function of directing a signal flow is arranged with the
Distributed Low Noise Amplifier, DLNA, being arranged to be turned off while
the antenna is working in the transmit mode by a first control voltage being
arranged to be connected to the Distributed Low Noise Amplifier, DLNA, and
the Distributed Power Amplifier, DPA, is arranged to be turned off while the
antenna is working in the receive mode by a second control voltage being
arranged to be connected to the Distributed Power Amplifier (DPA). The first
control voltage for turning off the DLNA can be applied to the gate terminals
of the amplifiers belonging to the DLNA. The second control voltage for
turning off the DPA can be applied to the gate terminals of the amplifiers
belonging to the DPA. Other solutions for turning off the DLNA or DPA are
also possible within the scope of the invention.
The active circulator can preferably be a Monolithic Microwave Integrated
Circuit, MMIC, module. The MMIC module is preferably based on Gallium
Nitride, GaN, semiconductor technology.
In a further example of the invention the amplifiers, the transmit and/or
receive amplifiers, comprise at least two layers of sub amplifiers, the sub
amplifiers being arranged between two transmission lines where at least one
is an intermediate transmission line. Figure 4 shows the active circulator 400
with the output transmission line 202, the antenna transmission line 203 and
the input transmission line 204 as described in association with figure 2. In
the example of figure 4 both the transmit and the receive amplifiers
comprises two layers of sub amplifiers. A first intermediate transmission line
401 is inserted in parallel between the output and antenna transmission lines.
A second intermediate transmission line 402 is inserted in parallel between
the antenna and input transmission fines. The intermediate transmission lines
have transmission line sections arranged in the same configuration as the
output-, antenna- and input transmission lines with the difference that the
intermediate transmission lines are equipped with termination impedances
403 at both the first 205 and second 206 side of the active circulator. The first
intermediate transmission line has transmission line sections T , to Ti and
the second intermediate transmission line has transmission fine sections Ti2 ,
The transmit amplifiers are in this example replaced with two layers of
transmit sub amplifiers, each layer having m transmit sub amplifiers. The
receive amplifiers are correspondingly replaced with two layers of receive
sub amplifiers, each layer having m receive sub amplifiers. The transmit sub
amplifiers are denoted At,ij and the receive sub amplifiers Ar,ij where i is an
integer running from 1 to n, denoting the layer and j is an integer index
running from 1 to . In the example of figure 4, n=4 and m=3. The transmit
sub amplifiers are in layer 1 and 2 and the receive sub amplifiers in layer 3
and 4 . The sub amplifiers are thus arranged in a matrix having co!umns
and n rows.
The At, amplifier is, in the example of figure 4, replaced with two transmit
sub amplifiers At and At 2 , with their input and output matching line
sections, connected in series. A - At 2 is extending between the output
transmission line and the antenna transmission in the same way as At, . The
sub amplifiers have matching line sections connected to both its input and
output terminals in the same way as the transmit and the receive amplifiers.
The input matching line sections of the first layer are denoted 4 , of the
second layer 412, of the third layer 4 13 and of the fourth layer 414. The
output matching line sections of the first layer are denoted 421 , of the second
layer 422, of the third layer 423 and of the fourth layer 424. At , with its
matching line sections is connected between the output transmission line and
the first intermediate transmission line. Each point, called intermediate points,
between transmission line sections in the first intermediate transmission line
is connected to a point between the first output matching line section 421 and
the second input matching Sine section 412 in the m columns of sub
amplifiers. There are thus intermediate points in each intermediate
transmission line. The At ,2i sub amplifier with its matching line sections is
connected between a first intermediate point and the antenna transmission
line such that the combination At n/At ,2i is extending between the output
transmission line and the antenna transmission in the same way as A , . The
other columns of sub amplifiers, A 2 At ,22 and A , 3 At,23 with their matching
fine sections are connected between the output transmission line and the
antenna transmission line in the same manner.
The intermediate points are numbered in consecutive order, starting with the
first intermediate point closest to the first side of the active circulator.
The receive sub amplifiers are inserted between the antenna transmission
line and the input transmission line in the same way as the transmit sub
amplifiers are inserted between the output transmission line and the antenna
transmission line. The Ar, amplifier is, as an example, replaced with two
receive sub amplifiers Ar, and Ar,2 with their matching line sections
connected in series. Ar,ii/A r,2i is thus extending between the antenna
transmission line and the input transmission in the same way as A .
In the configuration of the active circulator according to figure 4 , the DPA
thus comprises two layers of transmit sub amplifiers and the DLNA
comprises two layers of receive sub amplifiers. The turning off of the DLNA
during transmit mode can be arranged by the first contro! voltage being
applied, or arranged to be connected, to at least one gate terminal in each
column of receive sub amplifiers. Preferably the first control voltage is
applied, or arranged to be connected, to ail gate terminals in each column of
receive sub amplifiers. The turning off of the DPA during receive mode can
be arranged by the second control voltage being applied, or arranged to be
connected, to at least one gate terminal in each column of transmit sub
amplifiers. Preferably the second control voltage is applied, or arranged to be
connected, to all gate terminals in each column of transmit sub amplifiers.
The first and second control voltages can be generated, or arranged to be
generated, by any conventional means within the microwave system or
externally. The first control voltage is generated, or arranged to be
generated, when the T/R-module is in the transmit mode and the second
control voltage is generated, or arranged to be generated, when the T/Rmodule
is in the receive mode.
in the example of figure 4 the number of layers of transmit and receive sub
amplifiers are the same, in this case two layers of transmit sub amplifiers and
two layers of receive sub amplifiers. In other examples of the invention the
number of layers for transmit sub amplifiers and receive sub amplifiers can
differ. It is also possible to have one layer of transmit amplifiers combined
with two layers of receive sub amplifiers, i.e. there are three rows of
amplifiers/sub amplifiers.
In further examples of the invention there can also be more than two layers of
transmit sub amplifiers and/or more than two layers of receive sub amplifiers.
In these applications additional intermediate transmission lines have to be
inserted according to the principles described above n an example of the
invention with three layers of transmit sub amplifiers, one layer of transmit
sub amplifiers are thus extending between two intermediate transmission
lines.
In a further variation of the invention it is possible to have a different number
of columns of amplifiers or sub amplifiers for transmit amplifiers and receive
amplifiers. As an example it is possible within the scope of the invention to
have three columns of transmit amplifiers combined with 5 columns of
receive sub amplifiers arranged in two layers.
In an example of the invention illustrated in figure 5 , showing the active
circulator 500, the antenna transmission line can be divided in two parallel
transmission lines, a first 501 and a second 502 antenna transmission line.
One end of the antenna transmission lines is connected to the antenna port,
ANT, at the second side 206 of the active circulator and the opposite ends of
the antenna transmission lines are connected to a reference plane via
individual termination impedances 503 or via one common termination
impedance (not shown in figure 5). The reference plane can e.g. be a ground
plane. The example of figure 5 has otherwise the same configuration as
shown in figure 2 , i.e. it has three columns, m=3, of amplifiers and one row of
transmit amplifiers and one row of receive amplifiers. The first antenna
transmission line 501 has m+1 , i.e. four transmission line sections Ta,1 1 to
Ta,1 . The output signals from the transmit amplifiers are now fed to the first
antenna transmission line and travels along the first antenna transmission
line to the antenna port as described earlier.
The second antenna transmission line 502 has also m+1 , i.e. four
transmission line sections Ta,21 to Ta,24. The input signal from the antenna
is now fed to the second antenna transmission line and is successively
tapped, via the receive amplifiers, to the input transmission line where it
travels along the input transmission line to the RXout port as described
earlier.
The split of the antenna transmission line into two parallel transmission lines
can be applied to all examples and variations of the invention. An advantage
with this example of the invention is that the variations of the invention with
different numbers of columns for the transmit and receive amplifiers can be
more conveniently impiemented.
The function of the active circulator illustrated in figure 5 otherwise
corresponds to the functions of the active circulator of figure 2.
In one application of the invention the active circulator 201 , 400, 500
comprises the front-end arrangement for each Transmit/Receive-module,
T/R-module, in an Active Electronically Scanned Antenna, AESA, system.
The matching line sections and termination impedances shown in figures 2, 4
and 5, and described in association with these figures, are all individual
components and can assume individual values even if they are designated
with equal reference signs in the figures.
The invention also includes a method to manufacture an active circulator for
a microwave system. Said microwave system uses at least one front-end
arrangement, each front-end arrangement having a power amplifier function
arranged to deliver an amplified output signal via a circulator function to the
antenna 210 in a transmit mode and a low noise amplifier function arranged
to amplify an input signal from the antenna via the circulator function in a
receive mode. The circulator function is arranged to direct a signal flow
between the transmit and receive modes wherein the active circulator is
manufactured as one module with the power amplifier function, the low noise
amplifier function and the circulator function of directing a signal flow. Said
three functions for one front-end arrangement are thus integrated into one
module.
In one example of the method of the invention the power amplifier function
and the low noise amplifier function are arranged as a Distributed Power
Amplifier, DPA, and as a Distributed Low Noise Amplifier, DLNA, thus
achieving a broad band performance. A distributed amplifier has at least two
amplifiers, A , to At,m , A , to Ar,m, 300, connected in parallel between two
transmission lines, 202-204, one transmission line having an input port to the
distributed amplifier and the other transmission line having an output port of
the distributed amplifier.
In one example of the method of the invention the active circulator 201 , 400,
500 has an output transmission line 202, an antenna transmission line 203
and an input transmission line 204 in parallel, with the antenna transmission
line located between the output and the input transmission lines. The
transmission lines are extending between a first side 205 and a second side
206 of the active circulator and have following features:
• the output transmission line having a transmit input port TXin at the
first side 205 and a first termination impedance 207 at the second side
206,
• the antenna transmission line 203 having a second termination
impedance 208 at the first side 205 and an antenna port ANT at the
second side 206 and
· the input transmission line 204 having a receive output port RXout at
the first side 205 and a third termination impedance 209 at the second
side 206.
The Distributed Power Amplifier, DPA, has at least two transmit amplifiers
(At , - At m) connected in parailel between the output transmission line 202
and the antenna transmission line 203 and the Distributed Low Noise
Amplifier, DLNA, having at least two receive amplifiers Ar, - A connected
in parailel between the antenna transmission line 203 and the input
transmission line 204.
In one example of the method of the invention the circulator function of
directing a signal flow is arranged with the Distributed Low Noise Amplifier,
DLNA, being turned off while the antenna is working in the transmit mode by
applying a first control voltage to the Distributed Low Noise Amplifier, DLNA.
The Distributed Power Amplifier, DPA is turned off while the antenna is
working in the receive mode by applying a second control voltage to the
Distributed Power Amplifier, DPA.
In one example of the method of the invention the active circulator is
manufactured as a Monolithic Microwave Integrated Circuit, MMIC, module.
In one example of the method of the invention the MMIC module is
manufactured using Gallium Nitride, GaN, semiconductor technology.
The invention is not limited to the examples and embodiments described
above, but may vary freely within the scope of the appended claims.

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CLAIMS
1. An active circulator (201, 400, 500) for a microwave system, said
microwave system comprising at least one front-end arrangement, each
front-end arrangement comprising a power amplifier function arranged to
5 deliver an amplified output signal via a circulator function to an antenna (210)
in a transmit mode, and a low noise amplifier function arranged to amplify an
input signal from the antenna via the circulator function in a receive mode,
the circulator function being arranged to direct a signal flow between the
transmit and receive modes, c h a r a c t e r i z e d in that each front-end
10 arrangement comprises one active circulator (201, 400, 500), said active
circulator comprising the power amplifier function, the low noise amplifier
function and the circulator function of directing a signal flow, said three
functions integrated into one module, wherein the power amplifier function
^ and the low noise amplifier function of the active circulator are arranged as a
15 Distributed Power Amplifier, DPA, and as a Distributed Low Noise Amplifier,
DLNA, thus achieving a broad band perfomnance, a distributed amplifier
comprising at least two amplifiers (At,i to At^, Ar.i to Ar,m, 300) connected in
parallel between two transmission lines (202-204), one transmission line
comprising an input port to the distributed amplifier and the other
20 transmission line comprising an output port of the distributed amplifier.
2. The active circulator according to claim 1 , c h a r a c t e r i z e d in that the
active circulator (201, 400, 500) comprises three ports:
• an antenna port (ANT) for connection to the antenna, this port being a
25 common port for the output signal from the power amplifier function,
TXout, and for the input signal from the antenna, RXin,
• a transmit in port (TXin) arranged to receive an input signal to the
power amplifier function and
• a receive out port (RXout) arranged to output a signal from the low
30 noise amplifier function.
AMENDED SHEET
1 ^ ',>.,.„ X ...ron,ce PCT/SE 2010/05 0 69 5
3. The active circulator according to claim 1 or 2, c h a r a c t e r i z e d in that
the active circulator comprises an output transmission line (202) an antenna
transmission line (203) and an input transmission line (204) arranged in
parallel, with the antenna transmission line located between the output
5 transmission line and the input transmission line, the transmission lines t>elng
arranged to extend between a first side (205) and a second side (206) of the
active circulator,
• the output transmission line (202) comprising the transmit input port
10 (TXin) at the first side (205) and a first termination impedance (207) at
the second side (206),
• the antenna transmission line 203) comprising a second termination
impedance (208) at the first side (205) and the antenna port (ANT) at
the second side (206) and
15 "the input transmission line (204) comprising the receive output port
(RXout) at the first side (205) and a third termination impedance (209)
at the second side (206)
and the Distributed Power Amplifier, DPA, comprises at least two transmit
20 amplifiers (At.i - At.m) connected in parallel between the output transmission
line (202) and the antenna transmission line (203) and the Distributed Low
Noise Amplifier, DLNA, comprises at least two receive amplifiers (Ar,i - Ar.m)
connected in parallel between the antenna transmission line (203) and the
input transmission line (204).
25
4. The active circulator according to any one of claims 1-3,
c h a r a c t e r i z e d in that the circulator function of directing a signal flow is
arranged with the Distributed Low Noise Amplifier, DLNA, being arranged to
\ be turned off while the antenna is working in the transmit mode by a first
30 control voltage being arranged to-be connected to the Distributed Low Noise
Amplifier, DLNA, and the Distributed Power Amplifier, DPA, is arranged to be
AMENDED SHEET
L ' '•JV,^s.^<.. -,.TBmcI PCt7SE20I0/05 0 69 5
" • •^ST inieTnaiiOfiai -^-plicatlot
- 2 ^ - 1 7 -0^ 2012
turned off while the antenna is working in the receive mode by a second
control voltage being arranged to be connected to the Distributed Power
Amplifier, DPA.
5 5. The active circulator according to any one of claims 1-4,
c h a r a c t e r i z e d in that the active circulator (201, 400, 500) is a
Monolithic Microwave Integrated Circuit, MMIC, module.
6. The active circulator according to claim 5, c h a r a c t e r i z e d in that the
10 MMIC module is based on Gallium Nitride, GaN, semiconductor technology.
7. The active circulator according to any one of claims 3-6,
c h a r a c t e r i z e d in that the transmit and/or receive amplifiers comprise
at least two layers of sub amplifiers, (At,ii-At,i3, At,2rAt,23, Ar.n - Ar,i3, Af2i -
15 Ar,23) the sub amplifiers being arranged between two transmission lines
where at least one is an intermediate transmission line.
8. The active circulator according to any one of claims 3-7,
c h a r a c t e r i z e d in that the antenna transmission line is divided in two
20 parallel transmission lines, a first (501) and a second (502) antenna
transmission line, one end of the antenna transmission lines being connected
to the antenna port (ANT) at the second side (206) of the active circulator
(201, 400, 500) and the opposite ends of the antenna transmission lines
being connected to a reference plane via individual termination impedances
25 (503) or via one common termination impedance.
9. The active circulator according to any one of the preceding claims,
c h a r a c t e r i z e d in that the active circulator (201, 400, 500) comprises
the front-end arrangement for each Transmit/Receive-module, T/R-module,
30 in an Active Electronically Scanned Antenna, AESA, system.
AMENDED SHEET
* • i:S5j5^'-^4l^ PCT/SE2010/05 06 9 5
^ ^ ^ ^ 1 7 -04- 2012
10. A method to manufacture an active circulator for a microwave system,
; said microwave system usin^ at least one front-end arrangement, each front-
I end arrangement having a power amplifier function arranged to deliver an
amplified output signal via a circulator function to an antenna (210) in a
5 transmit mode and a low noise amplifier function arranged to amplify an input
signal from the antenna via the circulator function in a receive mode, the
circulator function being arranged to direct a signal flow between the transmit
and receive modes, c h a r a c t e r i z e d in that the active circulator is
manufactured as one module with the power amplifier function, the low noise
10 amplifier function and the circulator function of directing a signal flow, said
three functions for one front-end arrangement thus being integrated into one
module, wherein the power amplifier function and the low noise amplifier
function are arranged as a Distributed Power Amplifier, DPA, and as a
Distributed Low Noise Amplifier, DLNA, thus achieving a broad band
15 performance, a distributed amplifier having at least two amplifiers (At.i to At,m,
Ar.i to Arm, 300) connected in parallel between two transmission lines (202-
204), one transmission line having an input port to the distributed amplifier
and the other transmission line having an output port of the distributed
amplifier.
20
11. The method according to claim l O c h a r a c t e r i z e d i n that the active
circulator (201, 400, 500) has an output transmission line (202), an antenna
transmission line (203) and an input transmission line (204) in parallel, with
the antenna transmission line located between the output and the input
25 transmission lines, the transmission lines extending between a first side (205)
and a second side (206) of the active circulator,
• the output transmission line having a transmit input port (TXin) at the
first side (205) and a first termination impedance (207) at the second
30 side (206),
AMENDED SHEET
•
' i rne Gv-c« -.. roffiM PCT / SE 2010 / 0 5 0 6 9«;
- - 2 ^ - 1 7 -04- 2012
• the antenna transmission line (203) having a second termination
impedance (208) at the first side (205) and an antenna port (ANT) at
the second side (206) and
• the input transmission line (204) having a receive output port (RXout)
5 at the first side (205) and a third termination impedance (209) at the
second side (206)
and the Distributed Power Amplifier, DPA, having at least two transmit
amplifiers (At,i - At,,,) connected in parallel between the output transmission
10 line (202) and the antenna transmission line (203) and the Distributed Low
Noise Amplifier, DLNA, having at least two receive amplifiers (Ar,i - Arm)
i connected in parallel between the antenna transmission line (203) and the
I input transmission line (204).
I
15 12. The method according to any one of claims 10-11, c h a r a c t e r i z ed
in that the circulator function of directing a signal flow is arranged with the
Distributed Low Noise Amplifier, DLNA, being turned off while the antenna is
working in the transmit mode by applying a first control voltage to the
Distributed Low Noise Amplifier, DLNA, and the Distributed Power Amplifier,
20 DPA, is turned off while the antenna is working in the receive mode by
applying a second control voltage to the Distributed Power Amplifier, DPA.
I 13. The method according to any one of claims 10-12, c h a r a c t e r i z ed
in that the active circulator is manufactured as an Monolithic Microwave
25 Integrated Circuit, MMIC, module.
i
14. The method according to claim 13, c h a r a c t e r i z e d in that the MMIC
module is manufactured using Gallium Nitride, GaN, semiconductor
technology.