U.S. patent application number 15/628140 was filed with the patent office on 2020-01-23 for method and apparatus for calibration and equalization of multiport amplifiers (mpas).
This patent application is currently assigned to SPACE SYSTEMS/LORAL, LLC. The applicant listed for this patent is Space Systems/Loral, LLC. Invention is credited to Vijaya Gallagher, Richard Hoffmeister, Zheng Tu, Ghislain Turgeon, Anton Weaver-Madsen.
Application Number | 20200028475 15/628140 |
Document ID | / |
Family ID | 69161257 |
Filed Date | 2020-01-23 |
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United States Patent
Application |
20200028475 |
Kind Code |
A1 |
Turgeon; Ghislain ; et
al. |
January 23, 2020 |
METHOD AND APPARATUS FOR CALIBRATION AND EQUALIZATION OF MULTIPORT
AMPLIFIERS (MPAs)
Abstract
An amplifier system includes an input network having a plurality
of input ports; an output network having a plurality of output
ports; a plurality of amplification units coupled between the input
network and the output network, the plurality of amplification
units configured to amplify signals from the plurality of input
ports; and a calibration unit coupled between the plurality of
amplification units and the output network to calibrate amplified
signals from the plurality of amplification units.
Inventors: |
Turgeon; Ghislain; (San
Jose, CA) ; Weaver-Madsen; Anton; (Palo Alto, CA)
; Gallagher; Vijaya; (Palo Alto, CA) ;
Hoffmeister; Richard; (Palo Alto, CA) ; Tu;
Zheng; (Palo Alto, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Space Systems/Loral, LLC |
Palo Alto |
CA |
US |
|
|
Assignee: |
SPACE SYSTEMS/LORAL, LLC
Palo Alto
CA
|
Family ID: |
69161257 |
Appl. No.: |
15/628140 |
Filed: |
June 20, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62453992 |
Feb 2, 2017 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H03F 3/602 20130101;
H03F 1/0205 20130101; H03F 2201/3212 20130101; H03F 3/68 20130101;
H03F 1/3235 20130101; H03F 1/3247 20130101 |
International
Class: |
H03F 1/32 20060101
H03F001/32; H03F 3/60 20060101 H03F003/60; H03F 1/02 20060101
H03F001/02; H03F 3/68 20060101 H03F003/68 |
Claims
1. An amplifier system, comprising: a plurality of multiport
amplifiers, each of the plurality of multiport amplifiers
comprising: an input network having a plurality of input ports
including a first input port configured to selectively receive a
pilot signal, the input network including a first plurality of
hybrid couplers; an output network having a plurality of output
ports, the output network including a second plurality of hybrid
couplers; a plurality of amplification units coupled between the
input network and the output network, the plurality of
amplification units configured to amplify signals from the
plurality of input ports; a plurality of couplers between the
plurality of amplification units and the output network; a pilot
signal generator configured to generate a pilot signal; a
calibration unit to calibrate amplified signals from the plurality
of amplification units; a first pilot signal switching network
coupled to provide the pilot signal from the pilot signal generator
to first input ports of the plurality of multiport amplifiers; a
selector configured to select an individual multiport amplifier of
the plurality of multiport amplifiers, couple the pilot signal from
the pilot signal generator through the first pilot signal switching
network to the first input port of the individual multiport
amplifier, and couple the calibration unit between the plurality of
amplification units and the output network of the individual
multiport amplifier, the selector configured to select each of the
plurality of multiport amplifiers at different times; and a second
pilot signal switching network to provide the pilot signal to the
plurality of couplers between the plurality of amplification units
and the output network of the individual multiport amplifier, to
thereby bypass the plurality of amplification units for initial
calibration.
2. The amplifier system of claim 1 further comprising a plurality
of adjustment units disposed in series with the plurality of
amplification units.
3. The amplifier system of claim 2 wherein the calibration unit is
configured to obtain phase and amplitude data for the amplified
signals from the plurality of amplification units and the plurality
of adjustment units are configured to adjust phase and amplitude of
the signals amplified by the plurality of amplification units.
4. The amplifier system of claim 1 wherein the pilot signal is a
continuous wave signal at a fixed frequency.
5. The amplifier system of claim 1 wherein the calibration unit is
configured to compare an amplified pilot signal with a reference
signal to obtain relative phase and amplitude information for the
amplified pilot signal.
6. The amplifier system of claim 5 wherein the reference signal is
the pilot signal, or an amplified pilot signal from a reference
amplification unit.
7. The amplifier system of claim 1 wherein in each of the plurality
of multiport amplifiers, the plurality of input ports includes four
input ports, the input network includes four hybrid couplers, the
plurality of output ports includes four output ports, the output
network includes four hybrid couplers, the plurality of
amplification units includes four travelling wave tube amplifiers,
the plurality of multiport amplifiers includes twenty-two multiport
amplifiers, the selector configured to select one of the twenty-two
multiport amplifiers.
8. The amplifier system of claim 7 wherein the couplers between the
plurality of amplification units and the output network of each of
the plurality of multiport amplifiers include four couplers at
outputs of the four travelling wave tube amplifiers, the four
couplers selectably coupled to the calibration network and to the
pilot signal generator for calibration of passive components.
9. The amplifier system of claim 1 wherein the amplifier system is
embodied in a satellite.
10-20. (canceled)
21. The amplifier system of claim 9 wherein the satellite includes:
an Analog-to-Digital Converter (ADC) coupled to the calibration
unit, the ADC configured to convert calibration data from the
calibration unit to digitized calibration data; and a telemetry
unit coupled to the ADC, the telemetry unit configured to send the
digitized calibration data from the satellite to ground.
22. The amplifier system of claim 21 wherein the satellite further
includes a receiver configured to receive adjustment commands and
carry out adjustment of the individual multiport amplifier.
23. The amplifier system of claim 9 wherein the satellite includes:
an Analog-to-Digital Converter (ADC) coupled to the calibration
unit, the ADC configured to convert calibration data from the
calibration unit to digitized calibration data; and an adjustment
calculator coupled to the ADC, the adjustment calculator configured
to receive the digitized calibration data, determine what
adjustment to make, and provide corresponding adjustment commands
to the individual multiport amplifier without input from the
ground.
24. The amplifier system of claim 1 wherein the selector includes a
calibration switching network extending between the plurality of
couplers and the calibration unit.
25. The amplifier system of claim 24 wherein each of the plurality
of couplers includes a first port coupled to the calibration
switching network and a second port coupled to the second pilot
switching network.
26. The amplifier system of claim 25 wherein the plurality of
couplers connect the calibration switching network and the second
pilot switching network such that a pilot signal from the second
pilot switching network passes to the calibration switching network
without amplification.
27. An amplifier system, comprising: a first multiport amplifier
(MPA) comprising: an first input network having n input ports
including a first pilot input port configured to selectively
receive a pilot signal, the first input network including a first
plurality of input hybrid couplers; a first output network having n
output ports, the first output network including a first plurality
of output hybrid couplers; a first n amplification units coupled
between the first input network and the first output network, the
first n amplification units configured to amplify signals from the
n input ports of the first input network; a first n couplers
between the first n amplification units and the first output
network; a second MPA comprising: a second input network having n
input ports including a second pilot input port configured to
selectively receive the pilot signal, the second input network
including a second plurality of input hybrid couplers; a second
output network having n output ports, the second output network
including a second plurality of output hybrid couplers; a second n
amplification units coupled between the second input network and
the second output network, the second plurality of amplification
units configured to amplify signals from the n input ports of the
second input network; a second n couplers between the second n
amplification units and the second output network; a pilot signal
generator configured to generate a pilot signal; a first pilot
signal switching network extending between the pilot signal
generator and the first and second pilot input ports; a second
pilot signal switching network extending between the pilot signal
generator and the first and second n couplers; a calibration unit
to calibrate signals from the plurality of amplification units; and
a calibration switching network extending between the calibration
unit and the first and second n couplers, the calibration switching
network and the first pilot switching network configured to select
the first MPA or the second MPA as a selected MPA, couple the pilot
signal through the first pilot switching network to the pilot input
port of the selected MPA and couple the n couplers of the selected
MPA to the calibration unit for calibration of amplification units
of the selected MPA.
28. The amplifier system of claim 27 wherein the first input
network is configured to couple the pilot signal from the first
pilot input port to only the first n amplification units and the
second input network is configured to couple the pilot signal from
the second pilot input port to only the second n amplification
units.
29. The amplifier system of claim 27 wherein the calibration
switching network and the second pilot switching network are
configured to select the first MPA or the second MPA for initial
calibration that includes providing the pilot signal from the pilot
signal generator, through the second pilot switching network to
couplers of the first or second MPA without amplification, and from
the couplers through the calibration switching network to the
calibration unit without amplification.
30. An amplification system comprising: a plurality of multi-port
amplifiers (MPAs), each MPA including an input network, an output
network, a plurality of amplification units coupled between the
input network and the output network; a first pilot signal
switching network connected to the plurality of MPAs, the first
pilot switching network configured to provide a pilot signal to an
input port of the input network of a selected MPA of the plurality
of MPAs for calibration of the plurality of amplification units of
the selected MPA; a calibration switching network connected to the
plurality of MPAs, the calibration switching network configured to
send amplified pilot signals from between the plurality of
amplification units and the output network of the selected MPA for
calibration of the plurality of amplification units of the selected
MPA; a second pilot signal switching network connected to the
plurality of MPAs, the second pilot switching network configured to
provide the pilot signal without amplification to nodes between the
plurality of amplification units and the output network of the
selected MPA for initial calibration of the selected MPA that
bypasses the plurality of amplification units of the selected MPA;
and the first pilot signal switching network and the calibration
switching network are configured to individually select each of the
plurality of MPAs at different times as the selected MPA and to
perform calibration of the plurality of amplification units of the
selected MPA.
31. The amplification system of claim 30 wherein the first pilot
signal switching network and the calibration switching network are
further configured to select each MPA of the plurality of MPAs and
perform calibration of the plurality of amplification units of each
MPA according to a predetermined schedule or in response to a
triggering event.
Description
[0001] This application claims the benefit of U.S. Provisional
Patent Application No. 62/453,992, "Method and apparatus for
calibration and equalization of multiport amplifiers (MPAs)," filed
on Feb. 2, 2017.
BACKGROUND
[0002] Multiport Amplifiers (MPAs) are increasingly being proposed
for High Throughput Satellite (HTS) applications to provide the
flexibility to move power from one beam to another, depending on
the traffic demand. Satellites using MPAs at L, S and C band have
been flown for several years. Extending this technology to Ku, Ka
and higher frequency bands is a natural step, one that is being
proposed on a number of spacecraft.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] FIG. 1 is a block diagram describing a satellite
communication system.
[0004] FIG. 2 depicts a satellite that includes an amplification
system with multiple MPAs.
[0005] FIG. 3 shows an example of an MPA.
[0006] FIG. 4 illustrates operation of an MPA.
[0007] FIG. 5 illustrates power leakage in an MPA.
[0008] FIG. 6 illustrates an example of an MPA with calibration
hardware.
[0009] FIG. 7 illustrates coupling of calibration hardware to an
MPA.
[0010] FIG. 8 illustrates multiple MPAs sharing calibration
hardware.
[0011] FIGS. 9A-D illustrate an example of an amplification system
that includes calibration components.
[0012] FIG. 10 illustrates an example of a satellite with a
telemetry unit that sends calibration data to ground.
[0013] FIG. 11 illustrates an example of a satellite with an
adjustment calculator that uses calibration data to calculate
appropriate adjustment.
[0014] FIG. 12 illustrates an example of shared phase and amplitude
calibration hardware.
[0015] FIG. 13 illustrates an example of a pilot signal system.
[0016] FIG. 14 illustrates an example of hardware that provides a
pilot signal to multiple input ports of a selected MPA.
[0017] FIG. 15 illustrates a method of calibrating an MPA in a
satellite.
DETAILED DESCRIPTION
[0018] Some satellites use one or more multiport amplifier (MPA)
that each include multiple amplification units connected in
parallel in an arrangement that provides flexibility in allocating
power to user beams. An input network (INET) splits an input signal
equally and provides replica signals that pass along parallel
amplification pathways through each of the parallel amplification
units and are then recombined by an output network (ONET). Examples
of an amplification unit that may be used in MPAs include a
Travelling Wave Tube Amplifier (TWTA) and a Solid-State Power
Amplifier (SSPA). In general, paths through parallel amplification
units are arranged so that the amplitude and phase relationships
between different paths provide full transmission along wanted
paths without losing significant power to unwanted paths (i.e.
zero, or near zero power lost or "leaked" to unwanted paths). In
real systems, some leakage occurs and paths are not perfectly
isolated. Isolation between paths may be improved by maintaining
phase and amplitude relationships, which may tend to drift over
time, for example because of changes in hardware over time.
Adjustment may be performed to return phase and amplitude
relationships to acceptable ranges when they are found to be
outside their acceptable ranges. Efficiently identifying when
changes occur, quantifying changes, and providing appropriate
adjustment may provide benefits including reducing lost power.
[0019] In an example, a pilot signal may be provided to an input of
an MPA and a calibration unit may be coupled to outputs of
amplification units (e.g. between amplification units and an ONET)
of the MPA. These outputs may be compared with a reference signal.
For example, one amplification unit may be chosen as a reference
and its output may be used as a reference signal for comparison
with other amplification unit outputs, or the pilot signal may be
used as a reference signal for comparison with amplification unit
outputs. Amplitude and gain data may be obtained for the
amplification units relative to the reference signal. This data may
be digitized and sent to the ground, e.g. to a network control
center, where it is used to determine if adjustment is needed, and
if so, what adjustment should be made. Alternatively, an adjustment
system on-board the satellite may determine whether adjustment is
needed, if so, what adjustment should be made, and may perform the
adjustment without intervention, or with little intervention, from
the ground.
[0020] FIG. 1 depicts a block diagram of a wireless communications
system that includes a communication platform 100, which may be a
satellite located, for example, at a geostationary or
non-geostationary orbital location. In other embodiments, other
platforms may be used such as UAV or balloon, or even a ship for
submerged subscribers. In yet another embodiment, the subscribers
may be air vehicles and the platform may be a ship or a truck where
the "uplink" and "downlink" in the following paragraphs are
reversed in geometric relations. Platform 100 may be
communicatively coupled to at least one gateway 105 and a plurality
of subscriber terminals ST (including subscriber terminals 107).
The term subscriber terminals may be used to refer to a single
subscriber terminal or multiple subscriber terminals. A subscriber
terminal is adapted for communication with the wireless
communication platform including as satellite 100. Subscriber
terminals may include fixed and mobile subscriber terminals
including, but not limited to, a cellular telephone, wireless
handset, a wireless modem, a data transceiver, a paging or position
determination receiver, or mobile radio-telephone, or a headend of
an isolated local network. A subscriber terminal may be hand-held,
portable (including vehicle-mounted installations for cars, trucks,
boats, trains, planes, etc.) or fixed as desired. A subscriber
terminal may be referred to as a wireless communication device, a
mobile station, a mobile wireless unit, a user, a subscriber, or a
mobile.
[0021] In one embodiment, satellite 100 comprises a bus (i.e.
spacecraft) and one or more payloads (i.e. the communication
payload). The satellite may also include multiple power sources,
such as batteries, solar panels, and one or more propulsion
systems, for operating the bus and the payload.
[0022] At least one gateway 105 may be coupled to a network 140
such as, for example, the Internet, terrestrial public switched
telephone network, mobile telephone network, or a private server
network, etc. Gateway 105 and the satellite (or platform) 100
communicate over a feeder beam 102, which has both a feeder uplink
102u and a feeder downlink 102d. In one embodiment, feeder beam 102
is a spot beam to illuminate a region 104 on the Earth's surface
(or another surface). Gateway 105 is located in region 104 and
communicates with satellite 100 via feeder beam 102. Although a
single gateway is shown, some implementations will include many
gateways, such as five, ten, or more. One embodiment includes only
one gateway. Each gateway may utilize its own feeder beam, although
more than one gateway can be positioned within a feeder beam. Note
that the terms "feeder" beams and "service" beams are used for
convenience. Both feeder beams and service beams are spot beams and
the terms are not used in a manner to limit the function of any
beam. In one embodiment, a gateway is located in the same spot beam
as subscriber terminals.
[0023] Subscriber terminals ST and satellite 100 communicate over
service beams; for example, FIG. 1 shows service beams 106, 110,
114 and 118 for illuminating regions 108, 112, 116 and 120,
respectively. In many embodiments, the communication system will
include more than four service beams (e.g., 60, 100, etc.). Each of
the service beams have an uplink (106u, 110u, 114u, 118u) and a
downlink (106d, 110d, 114d, 118d) for communication between
subscriber terminals ST and satellite 100. Although FIG. 1 only
shows two subscriber terminals within each region 108, 112, 116 and
120, a typical system may have thousands of subscriber terminals
within each region.
[0024] In one embodiment, communication within the system of FIG. 1
follows a nominal roundtrip direction whereby data is received by
gateway 105 from network 140 (e.g., the Internet) and transmitted
over the forward path 101 to a set of subscriber terminals ST. In
one example, communication over the forward path 101 comprises
transmitting the data from gateway 105 to satellite 100 via uplink
102u of feeder beam 102, through a first signal path on satellite
100, and from satellite 100 to one or more subscriber terminals ST
via downlink 106d of service beam 106. Although the above example
mentions service beam 106, the example could have used other
service beams.
[0025] Data can also be sent from the subscriber terminals ST over
the return path 103 to gateway 105. In one example, communication
over the return path comprises transmitting the data from a
subscriber terminal (e.g., subscriber terminal 107 in service beam
106) to satellite 100 via uplink 106u of service beam 106, through
a second signal path on satellite 100, and from satellite 100 to
gateway 105 via downlink 102d of feeder beam 102. Although the
above example uses service beam 106, the example could have used
any service beam.
[0026] FIG. 1 also shows a Network Control Center 130, which
includes an antenna and modem for communicating with satellite 100,
as well as one or more processors and data storage units. Network
Control Center 130 provides commands to control and operate
satellite 100. Network Control Center 130 may also provide commands
to any of the gateways and/or subscriber terminals.
[0027] In one embodiment, communication platform 100 implements the
technology described above. In other embodiments, the technology
described above is implemented on a different platform (e.g. on the
ground or on a different type of satellite) in a different
communication system.
[0028] The architecture of FIG. 1 is provided by way of example and
not limitation. Embodiments of the disclosed technology may be
practiced using numerous alternative implementations.
[0029] Multiport Amplifiers (MPAs) are increasingly being proposed
for High Throughput Satellite (HTS) applications to provide the
flexibility to move power from one beam to another, depending on
the traffic demand. Satellites using MPAs at L, S and C band have
been flown for several years. Extending this technology to Ku, Ka
and higher frequency bands is a natural step, one that is being
proposed on a number of spacecraft
[0030] MPA performance is well known to be susceptible to
degradation due to changes in gain and phase of the MPA
components--for example, the Travelling Wave Tube Amplifier (TWTA)
or Solid-State Power Amplifier (SSPA) components--as they can vary
widely over the life of the satellite. At Ku band, relative phase
variations between the set of TWTAs used in an MPA can be as large
as 20 degrees over the 15-year satellite life, and gain variations
can be of the order of 2 dB over 15 years.
[0031] Corrections of these gain and phase variations over life and
compensation for the variations facilitate proper functioning of
MPAs in many applications, because the result of these variations
is leakage of desired channel power into adjacent channels, which
can manifest as coherent interference or multipath effects, as well
as a reduction in power at the desired output ports. Many of the
corrections in amplitude and phase over a satellite life are
attributable to the active components in the MPA (typically TWTAs,
but could be SSPAs, or other components). Aspects of the present
technology include systems and methods to detect changes in MPA
characteristics over time, for example changes in gain and phase in
TWTAs or other amplifier units, so that appropriate adjustment may
be made. A TWTA may be a Linearized TWTA (LTWTA) and the term TWTA
is used herein to include LTWTAs and other variations on basic TWTA
design.
[0032] FIG. 2 illustrates an example of a satellite 200 that may be
part of a satellite system (e.g. like satellite 100 of FIG. 1).
Satellite 200 includes m signal input modules 202_1-202_m, where an
individual signal input module may include an antenna to receive an
RF signal from a gateway, user terminal, or other source that is
external to satellite 200. Satellite 200 also includes n signal
output modules 204_1-204_n, where an individual signal output
module may include an antenna to direct an RF signal to a gateway,
user terminal, or other recipient that is external to satellite
200. For example, output modules 204_1-204_n may direct spot beams
to user terminals. The numbers of inputs and outputs m and n may
depend on satellite design and configuration. An amplification
system 206 is located between the input modules and output modules
to amplify received signals before sending them to a recipient. It
will be understood that FIG. 2 is a simplified illustration and
that additional components may be provided including multiplexers,
demultiplexers, filters, etc. Amplification system 206 includes X
MPAs (MPA 1-MPA X), where X may be any suitable number depending on
satellite design. In FIG. 2, multiple MPAs are arranged in parallel
to amplify a large number of signals and provide high
throughput.
[0033] FIG. 3 shows an example of an MPA 300 that has n input ports
302, n output ports 304, and n amplification units (Amp 1-n)
arranged in parallel (redundant components are omitted in this
figure for simplicity). Such an MPA may be considered an n.times.n
MPA, where n may be any suitable number. For example, 4.times.4,
8.times.8, 16.times.16 MPAs may be used in different applications
and other values of n may also be used. While specific examples are
described below, it will be understood that aspects of the present
technology are applicable to MPAs of any size.
[0034] Input ports 302 connect with an input network, INET 306,
which couples signals from input ports 302 so that an input from a
given input port is split equally to provide replica signals that
pass along parallel amplification pathways. The signals are
provided to an input redundancy network 308, which provides access
to one or more redundant pathways that can be used if default
amplifiers fail. Signals then pass through an adjustment stage 310,
where adjustment units Adj_1-Adj_n provide the ability to
individually adjust each pathway. For example, phase, gain or both
may be adjusted for each pathway in adjustment stage 310 in a
controllable manner (e.g. in response to a command). Signals then
pass through fixed amplification stage 312 where each signal is
amplified by a respective amplification unit Amp_1-Amp_n.
Amplification of each pathway is adjustable (i.e. gain is
adjustable) through the corresponding adjustment units so that both
the phase and amplitude of a signal from a fixed amplification unit
are adjustable. Thus, an individual pathway includes a fixed
amplification unit in series with an adjustment unit so that if the
amplification unit (or other component along the pathway) changes
over time, adjustment can be made to return it to an acceptable
condition. Detecting and measuring such changes and making
appropriate correction in response to such changes may provide
several advantages including keeping signal leakage at an
acceptable level.
[0035] An output redundancy network 314 provides access to one or
more redundant pathways (in conjunction with input redundancy
network 308). Thus, while n pathways may be active, there may be
one or more inactive pathways, which are not shown in FIG. 3. Spare
pathways are provided for redundancy and are only used when a
default pathway fails (e.g. an amplification unit fails to meet a
predetermined specified standard). In a 4.times.4 MPA a single
redundant pathway may be sufficient, in a larger MPA, such as an
8.times.8 MPA, two redundant pathways may be preferred, and in
larger MPAs, more redundancy may be provided. In some MPAs, no
redundant amplification pathways may be provided.
[0036] An output network, ONET 316, receives signals from output
redundancy network 314 from n pathways and recombines them so that
ONET 316 generally reverses the signal splitting of INET 306 to
provide an amplified signal at an output port.
[0037] FIG. 4 provides a simplified illustration of how an input
signal S is received at an input port (input port n) and is
amplified by n amplification units, Amp_1-Amp_n, in parallel (input
networks and output networks are omitted for simplicity). Signal S
is split into signals S' that travel along parallel pathways
through adjustment stage 310 and amplification stage 312, with each
pathway having an adjustment unit and an amplification unit. Thus,
one pathway passes through Adj_1 and Amp_1, while another passes
through Adj_2 and Amp_2, and so on. The amplified signals S'' are
then recombined and provided as an amplified output S at output
port 1.
[0038] While FIG. 4 illustrates ideal operation of MPA 300, real
MPAs may not operate perfectly so that there may be some leakage of
signal power to other output ports, which may reduce power of
amplified output signal S and may cause interference at other
output ports.
[0039] FIG. 5 illustrates leakage of power to output ports other
than output port 1. In addition to providing amplified signals S''
to output port 1, some signals (indicated by dotted lines) are
provided to other output ports (e.g. output ports 2, 3, and so on).
Power provided to output port 1 is reduced accordingly and unwanted
effects may be experienced at output ports 2-n. Leakage increases
as phase and/or amplitude of amplified signals S'' drift from an
established range (e.g. a range established by tuning during an
initialization procedure). This may occur where changes in
amplification units produce changes in gain and/or output phase.
Keeping such leakage of power within an acceptable range may be
achieved by adequately adjusting phase and amplitude of amplified
signals S'' so that they maintain a predetermined relationship over
time. In order to accurately maintain phase and amplitude within a
range, detection and measurement of changes in these parameters may
be performed.
[0040] In one aspect, what is described is a calibration method
that focuses on hardware post INET and Pre ONET. It is recognized
that an amplification unit (e.g. TWTA) is often the primary source
of variation in phase and gain tracking between the amplification
pathways of the MPA over life. This approach is making measurements
to track degradations in the MPAs, sending this information to the
ground as part of the regular satellite telemetry stream to a
Satellite Operations Center (SOC) and letting the operator have a
very simple method of deciding what corrections to make and then
sending the appropriate commands to the satellite to implement the
corrections. This principle can be applied to 4.times.4, 8.times.8,
16.times.16 or larger MPAs.
[0041] FIG. 6 schematically illustrates an example of an MPA 600
including calibration hardware. In this scheme, a pilot signal, P,
which may be a continuous wave (CW) carrier is injected into one of
the input ports (input port n) of an INET by a coupler as shown at
the point labeled "P" in FIG. 6. The signal is distributed by INET
606 and input redundancy network 608 to parallel pathways through
adjustment units Adj_1-Adj_n of adjustment stage 610 and
amplification units Amp_1-Amp_n (which may be TWTAs) of
amplification stage 612 to output redundancy network 614. Each of
the amplified pilot signals then passes via calibration unit 618 to
ONET 616 and output ports 1-n. Calibration unit 618 is coupled to
parallel pathways at this point, prior to combining pathways in
ONET 616, so that each amplified signal may be individually
accessed for calibration purposes.
[0042] In some amplification systems (e.g. amplification systems
provided in satellites) two or more MPAs may be provided to amplify
a large number of signals. While each MPA in such a system may
include dedicated calibration hardware, it may be beneficial to
share some or all calibration hardware between MPAs. Thus, while
calibration hardware may be coupled between amplification units and
an ONET of an MPA, some or all calibration hardware may be located
remotely where it may be shared between MPAs. Similarly, while each
MPA may have a dedicated pilot signal generator, it may be
beneficial to share some or all such pilot signal generation
hardware between MPAs.
[0043] FIG. 7 shows an example of an MPA 700 that shares certain
calibration hardware with other MPAs. In particular, MPA 700
includes a coupling stage 718 between amplification stage 712 and
ONET 716 (redundancy networks are omitted in this figure for
simplicity). Coupling stage 718 includes individual couplers
Cpl_1-Cpl_n along each amplification pathway (e.g. Cpl_1 on pathway
that includes Adj_1 and Amp_1, Cpl_2 on amplification pathway that
includes Adj_2 and Amp_2, etc.). Each coupling Cpl_1-Cpl_n allows
an amplified signal from a respective amplification unit
Amp_1-Amp_n to be provided to calibration unit 730. Thus, n
couplers, Cpl_1-Cpl_n are connected to calibration unit 730 through
a selector 732. One or more other MPA may be similarly connected to
calibration unit 730 through selector 732 so that one MPA is
selected at any given time. Thus, calibration unit 730 is shared
between multiple MPAs. While calibration unit 730 is on-board a
satellite with MPA 700, in other examples, some or all components
of a calibration unit may be located remotely from an MPA, for
example, on the ground.
[0044] FIG. 7 also shows signal generator 734 connected through
selector 736 to input port n of MPA 700. Selector 736 may allow
signal generator 734 to connect with one or more other MPA.
Selector 736 may provide a signal from signal generator 734 (e.g. a
pilot signal such as a continuous wave signal) to a selected MPA
while selector 732 connects calibration unit 730 to the selected
MPA. Thus, selectors 736, 732 may operate together to connect
signal generator 734 and calibration unit 730 to a selected MPA,
with different MPAs being selected at different times.
[0045] FIG. 8 shows an amplification system 800 that includes X
MPAs (MPA_1-MPA_X) that share certain calibration hardware.
Amplification system 800 includes calibration unit 830, which is
selectively coupled to a selected MPA by selector 832 (i.e. one of
the MPAs, MPA_1-MPA_X is selected at a given time by selector 832
and is connected to calibration unit 830. Amplification system 800
also includes a pilot signal generator 834, which is selectively
coupled to the selected MPA by selector 836. Thus, selector 836 and
selector 832 operate together to select an MPA and may be
considered to form a selector 850.
[0046] FIGS. 9A-D illustrate an embodiment of an amplification
system that includes 22 4.times.4 MPAs sharing a calibration unit
to detect and measure phase and amplitude changes. FIG. 9A shows an
example of an MPA 900, with a pilot signal, which may be a
continuous wave (CW) carrier injected into one of the input ports
of an INET 906 by a coupler 940 as shown at the node labeled `2` in
FIG. 9A. The signal applied through coupler 940 is distributed
through INET 906, which includes four hybrid couplers "H," to
adapters 942a-d, which are waveguide to coaxial adapters in this
example. Phase shifters (phase trimmers) 944a-d are manually
adjusted phase shifters in this example and may be set during
initialization to tune MPA 900 (additionally, phase along each
amplification may be adjusted during use as described below). In
other examples, commandable phase shifters or other electronic
devices may be used instead of manual devices. Input redundancy
network 908 includes switches ("SW") and phase shifters (phase
trimmers, "PT") that allow rerouting of signals so that the four
inputs from phase shifters (phase trimmers) 944a-d can be connected
to any four of the five outputs of input redundancy network 908,
which connect to linearizers 946a-946d and spare linearizer 946s.
It will be understood that only four of the five linearizers are
active at any time according to the pathways selected by input
redundancy network 908. Linearizers 946a-d and spare linearizer
946s are connected to amplification units 948a-948d and spare
amplification unit 948s. Amplification units may be TWTAs, SSPAs,
or some other suitable amplification units. The combination of a
linearizer and a TWTA may be considered a linearized TWTA, or
LTWTA. Outputs of amplification units 948a-948d and spare
amplification unit 948s are connected through corresponding
circulators 950a-d and spare circulator 950s, which act as RF
isolators, to output redundancy network 914. Output redundancy
network 914 includes switches ("SW") to allow four of the five
amplification units to be connected (in conjunction with input
redundancy network 908). It will be understood that the redundancy
networks of FIG. 9A are for illustration and that aspects of the
present technology may be implemented using different redundancy
networks (or no redundancy network). Couplers 952a-d (or "test
couplers") are connected between outputs of output redundancy
network 914 and inputs of ONET 916 so that there is one coupler for
each active pathway (i.e. regardless of which amplification units
are active, including spare amplification unit 948s, there will be
one test coupler coupled to the output of each active amplification
unit). ONET 916 combines signals and generates output signals at
output ports A-D.
[0047] Each coupler 952a-d includes an input port and an output
port, which may be considered nodes that connect with hardware that
external to the MPA. Thus, couplers 952a-d have respective nodes
1a-d (input ports) and nodes 3a-d (output ports), respectively
(e.g. coupler 952a includes node 1a and node 3a, coupler 952b
includes node 1b and node 3b, and so on). Input ports at nodes
1a-1d allow a pilot signal to be applied to couplers 952a-d and
output ports at nodes 3a-3d allow amplified signals to be sampled
at couplers 952a-d for calibration purposes.
[0048] FIG. 9B shows how output ports of couplers 952a-d at nodes
3a-d connect to calibration circuits including a primary phase
calibration unit 960. Taking output port at node 3a as an example,
this pre-ONET port connects through a 22:1 output switching network
962a, which uses WR75 waveguide switches ("Pre-ONET Output SW
network 22:1 WR75-Sw") to select one of the 22 such output ports of
22 MPAs provided. Similar ports are provided on 21 other MPAs and
are similarly connected through switching networks. The selected
output is connected through a WR75-to-SMA adapter 964a and 1:2
hybrid coupler 966a that provides a phase calibration output at
node 3a1 and a power calibration output at node 3a2 (components
such as adapters and couplers are provided as examples, other
adapters such as WR51-to-SMA may be used in some embodiments and
adapters and/or couplers may not be necessary in other examples).
Phase calibration output from node 3a1 is connected through a 1:2
coupler 968a to primary phase calibration unit 960 and redundant
phase calibration unit 970, through filters ("FLTR"). Primary phase
calibration unit 960 may be active by default, with redundant phase
calibration unit 970 activated only if primary phase calibration
unit 960 fails.
[0049] Output ports 3b, 3c, and 3d are similarly connected through
22:1 output switching networks 962b-d respectively, and through
adapters 964b-d and couplers 966b-d respectively to provide phase
calibration outputs at nodes 3b1, 3c1, and 3d1 and power
calibration outputs at nodes 3b2, 3c2, and 3d2. Switching networks
962a-d may collectively be considered as a switching network 962,
or selector, that selects a particular MPA (selected MPA) from
among the 22 MPAs connected to switching network 962. Nodes 3b1,
3c1, and 3d1 are selectively coupled through switches 972a-b so
that one of the outputs from one of these nodes is selected and is
provided to 1:2 coupler 974, which provides the selected input to
an active phase calibration unit (either primary phase calibration
unit 960 or redundant phase calibration unit 970). A second input
to primary phase calibration unit 960 and redundant phase
calibration unit 970 comes from coupler 968a, so that the outputs
from nodes 3b1, 3c1, and 3d1 can be compared with the output from
node 3a1. Primary phase calibration units 960 and redundant phase
calibration unit 970 compare a signal from node 3a1 with signals
from nodes 3b1, 3c1, and 3d1. The signal from node 3a1 (sampled at
coupler 952a of FIG. 9A) corresponds to the pilot signal injected
at coupler 940, amplified by amplification unit 948a, and may be
considered a reference signal in this example because it is used
for comparison with the other amplified signals (e.g. with signal
from node 3b1 amplified by amplification unit 948b, signal from
node 3c1 amplified by amplification 948c, and signal from node 3d1
amplified by amplification 948d). Comparison of amplified signals
provides relative phase data for amplified signals from
amplification units 948b-c relative to an amplified signal from
amplification unit 948a. Such relative phase data may indicate
changing phase relationships between signals from different
pathways (e.g. because of differences between amplification units
over time). Quantifying such relative phase changes provides
calibration data that may be used to restore phase relationships to
an acceptable range (e.g. restore relative phases to their
initialized relationship).
[0050] FIG. 9B shows how the differential phase between one of the
amplified pilot signals from one of the amplification units (one
output CW signal in this example), taken as the reference (from a
reference Output Coupler), is measured for each remaining three
amplification unit pathways (TWTAs pathway) within a given
4.times.4 MPA. This phase difference, from an alignment reference,
for each pathway (designated by theta 2-1, theta 3-1 and theta 4-1)
can be measured accurately using simple circuitry by adjusting the
output couplers and switching network loss such that the two
signals being compared are close to the alignment values for phase.
In this case, the phase difference detector is simply the output of
a simple mixer, since the two signals are at the same
frequency.
[0051] FIG. 9C illustrates an example of how primary power
calibration unit 980 and redundant power calibration unit 982 may
be selectively coupled to pathways of an MPA. Nodes 3a2, 3b2, 3c2,
and 3d2 receive power calibration outputs from switching networks
962a-d respectively as shown in FIG. 9B and are thus coupled to
different amplification pathways of a selected MPA. Switches 984a-c
selectively connect one of nodes 3a2-3d2 to a coupler 986, which
connects a selected node through a filter ("FLTR") to primary power
calibration unit 980 and redundant power calibration unit 982.
[0052] The amplitude of the output signal from each of the four
pathways (i.e. from each amplification unit) is measured using a
power detector in a power calibration unit to generate respective
amplitude measurements A1, A2, A3, A4. Since the same pilot signal
(e.g. CW signal) is also coupled into all pathways (through all
amplification units) the amplitude and phase differences through
each of the four pathways are measured during a given time period
when the MPA is selected. The values (A1, A2, A3, A4) and (theta
2-1, theta 3-1, theta 4-1) for the four pathways through the four
amplification units may be transmitted to the ground in the normal
telemetry stream, needing no additional hardware. Since changes in
phase and amplitude relationships (e.g. TWTAs variation) tend to
occur slowly (ageing and seasonal variation), this telemetry data
generally does not need to be transmitted very frequently and does
not therefore place much of a burden on the telemetry system.
[0053] On the ground, the operator may compare the received values
of (A1, A2, A3, A4) and (theta 2-1, theta 3-1, theta 4-1) with the
factory settings at the time of satellite launch, and may send
commands to the satellite to adjust the phase and gain settings of
the amplification units (e.g. TWTAs) and/or other components.
Software simulation may be performed using the Amplitude and Phase
information to determine if an adjustment is necessary to maintain
the desired MPA isolation performance. Gain adjustments are a
normal part of any amplification unit adjustment (e.g. TWTA
adjustment), and may be performed in a Linearizer or other
component prior to, or as part of the amplification unit. Phase
adjustments may be made by including commandable phase shifters
that can be included in the same unit as the Linearizer but could
be separate devices prior to the TWTA. While linearizers 946a-d are
used to perform phase adjustment in the example above, in other
examples separate adjustment components may be provided along
amplification pathways.
[0054] FIG. 9D shows an example of hardware for providing a pilot
signal that is shared by 22 MPAs (e.g. MPA 900). In order to reduce
the number of Pilot units on board a satellite, a pre-INET 1:22
switch network 990 ("Pre-INET Input SW network"), is provided as
shown, connected to a Pilot, 992, through a 4:2 hybrid coupler 994
producing a pilot signal at a suitable frequency, for example, a
frequency at or near the edge of a frequency band allocated for use
by the satellite, or other frequency that is not used for
transmission of user data. While a continuous wave pilot signal at
a fixed frequency is one example of a pilot signal, other signals
may be used as pilot signals. Pilot signals may be generated at
multiple frequencies and may be modulated in various ways to test
power leakage over a range of conditions. While the examples
described here include a pilot signal generator on-board a
satellite, other examples may include generation of pilot signals
externally, for example, on the ground, with the pilot signal being
received by the satellite and injected at appropriate nodes of
MPAs.
[0055] Making measurements with unique phase and power detectors
may help to minimize the potential impact from the detector
variation (e.g. ageing and temperature) on the measurement accuracy
since all measurements are relative and are made by a given phase
and power detector for all MPAs. With this approach, the signal is
cycled through the MPA calibrations one MPA at a time for the 22
MPAs, using minimal expensive hardware like MLOs, power and phase
detectors while avoiding signal interference with proper sequencing
of the switches. Thus, switching network 990 selects a particular
MPA and provides an output to node 2 of the selected MPA (e.g. as
provided to coupler 940 of MPA 900). Switching networks 990 and 962
may be considered as forming a single switching network, or
selector, that selects one of the 22 MPAs at a time as a selected
MPA, with switching network 990 selecting the MPA to provide the
pilot and switching network 962 taking readings from the selected
MPA.
[0056] FIG. 9D also shows a switching network 996, which provides
the pilot signal from the Pilot 992 to the selected MPA, where a
coupler 998 produces four signals that are provided to nodes 1a-d
as shown in FIG. 9A. Pilot signals injected at nodes 1a-d of
couplers 952a-d bypass amplification units and may be used to
calibrate passive components. Such an initial calibration of the
passive components (excluding the amplification units, e.g. TWTAs
and adjustment units) of the calibration hardware may help to
minimize the effect of calibration hardware on the accuracy of the
measurement system. Here the injected signals are injected at input
ports 1a through 1d and are measured at nodes 3a through 3d
similarly as described above, but in this case the active pathway
components (e.g. TWTAs, LTWTAs, SSPAs, or other amplification
units, linearizers, etc.) are excluded so that only passive
components of the system affect measurement. By obtaining baseline
measurements for the calibration system without active components,
any differences caused by these components may be accounted for and
can be eliminated from subsequent measurements that include active
components.
[0057] When calibration data is obtained (e.g. phase and/or
amplitude data), the calibration data may be used to determine if
an MPA is operating within an acceptable range. For example, prior
to launch, gains of amplification units, settings of phase
shifters, and settings of other components may be adjusted to
establish phase and amplitude relationships between different
amplification pathways that provide low power leakage.
Subsequently, after launch, it may be desirable to maintain low
power leakage by keeping phase and amplitude relationships close to
their initial values and acceptable ranges may be defined
accordingly. When one or more amplitude and/or phase relationship
is outside an acceptable range, adjustment may be performed to
return it to the acceptable range.
[0058] FIG. 10 shows an example of a satellite 1000 that includes X
MPAs with shared calibration hardware. A selector 1002 selects an
individual MPA (one of MPA_1-MPA_X) as a selected MPA and connects
it with pilot signal generator 1001 and calibration unit 1004 so
that calibration data may be obtained for the selected MPA.
Calibration unit 1004 is connected to Analog-to-Digital Converter,
ADC 1006, which converts calibration to a digital format. The
digitized calibration data is then sent to telemetry unit 1008,
which sends the digitized calibration data to ground (e.g. to a
network control center), where the digitized calibration data may
be analyzed and a determination may be made as to whether the
digitized calibration data indicates operation within an acceptable
range. If operation is not within an acceptable range then suitable
adjustments may be calculated from the digitized calibration data.
Appropriate adjustment commands may then be sent from ground to a
receiver 1010 in satellite 1000, which sends the adjustment
commands to the selected MPA and carries out adjustment of the
selected MPA per the adjustment commands, for example, by adjusting
gain and/or phase of at least one amplification pathway in the
selected MPA. Receiver 1010 may connect directly to MPAs, or may
connect through one or more intervening components such as selector
1002. Selector 1002 may include switching networks for RF signals
(e.g. similar to switching networks 990 and 962 above) and a switch
for commands that directs commands to a selected MPA.
[0059] In an alternative arrangement illustrated in FIG. 11,
adjustment may be performed with little or no intervention from the
ground. FIG. 11 shows a satellite 1100, which is similar to
satellite 1000 (components are similarly numbered). In this
example, digitized configuration data from ADC 1006 is sent to an
adjustment calculator 1104, which determines if adjustment is
needed, and if so, what adjustment to make. This may be done
without input from the ground and may use a lookup table, or other
resource to obtain appropriate adjustment from digitized
calibration data. Adjustment calculator 1104 provides adjustment
commands to a selected MPA which carries out the commands as
before. Adjustment calculator 1104 may connect directly to MPAs, or
may connect through one or more intervening components such as
selector 1002. Thus, calibration data may be analyzed on-board a
satellite and suitable adjustment commands may be generated
on-board, without intervention from the ground.
[0060] FIG. 12 shows another example of hardware that may be used
to obtain amplitude and phase data for pathways of an MPA. Nodes
3a-d are connected between amplification units and an ONET as
before (e.g. to connectors 952a-d as shown in FIG. 9A). Pre-ONET
output switching networks 1202a-d couple nodes 3a-d of a selected
MPA to switches 1204a-d and 4:2 hybrid coupler 1206. Switches
1204a-d select one node at a time from the selected MPA. For
example, in FIG. 12, switch 1204a is closed, thus coupling an
amplified pilot signal from node 3a to coupler 1206, while switches
1204b-d are open so that other nodes 3b-d are not coupled to
coupler 1206. The two outputs of coupler 1206 are provided to
switches 1208a and 1208b, which select either a primary calibration
unit 1210 or redundant calibration unit 1212 (FIG. 12 shows switch
1208a closed and switch 1202b open to select primary calibration
unit 1210). Primary calibration unit 1210 and redundant calibration
unit 1212 may be considered examples of FQ demodulator networks.
The signal from node 3a goes through band pass filter 1214 and low
noise amplifier 1216 to primary calibration unit 1210 where it is
provided as an RF input to two mixers 1218a and 1218b that also
receive the pilot signal as local oscillator (LO) inputs. Mixer
1218a receives the pilot signal with zero phase adjustment
(0.degree.) as its LO input and provides an intermediate frequency
(IF) output I through a low pass filter 1220 to analog-to-digital
converter 1222. Mixer 1218b receives the pilot signal with
ninety-degree phase adjustment (90.degree.) as its LO input and
provides an IF output Q through a low pass filter 1224 to
analog-to-digital converter 1226. The in-phase (I) and
quadrature-phase (Q) signals from the I/Q demodulator contains the
delta phase and amplitude information between the Pilot reference
and the pathway under test. By measuring all the MPA pathways with
the Pilot reference the relative phase and amplitude between
pathways within the MPA can be assessed and compared with the
initial on the ground factory alignment. Digital I and Q values
from analog-to-digital converters 1222, 1226 may be provided to
ground (e.g. as part of telemetry data sent by telemetry equipment)
or may be used to identify any deviation from acceptable ranges,
calculate adjustments, and perform adjustments on the satellite.
Redundant calibration unit 1212 has identical components configured
to perform identical functions as in primary calibration unit 1210
and a detailed description is therefore unnecessary.
[0061] Rather than taking an amplified pilot signal from one
amplification pathway as a reference signal, here the pilot signal
is used as a reference signal. The pilot signal is provided to
primary calibration unit 1210 and redundant calibration unit 1212
for use as a reference signal. Alternatively, a different signal
may be provided as a reference signal (e.g. an output of a
particular amplification pathway of the selected MPA).
[0062] FIG. 13 shows an example of hardware that provides a pilot
signal to primary calibration unit 1210 and redundant calibration
unit 1212, in addition to other components. Three pilot signal
generators 1302a-c are provided in a redundant arrangement in this
example. Switches 1304a-c allow an active pilot signal generator
from pilot signal generators 1302a-c to be connected to 2:2 hybrid
couplers 1306a-b, which provide outputs to 2:6 hybrid couplers
1308a-b, which in turn provide 12 outputs, including an output to
primary calibration unit 1210 and an output to redundant
calibration unit 1212 so that the pilot signal can be used as a
reference signal. Outputs from 2:6 hybrid couplers 1308a-b may be
switched between MPAs, as shown for example by additional switches
1310a-b, which allow selection of output 21 or 22, which may
correspond to different MPAs.
[0063] In order to calibrate over a range of different conditions,
a pilot signal may be applied to more than one input port of an MPA
and suitable hardware may be provided for this purpose. FIG. 14
shows an example of an MPA 1400 with four inputs A-D that each have
a coupler, couplers 1420a-d, to receive a pilot signal that can be
injected at any one of the input ports. The pilot signal is
generated by a pilot signal generator 1422, which may be an active
pilot signal generator in a redundant arrangement (e.g. three pilot
signal generators 1302a-c of FIG. 13). The output of pilot signal
generator 1422 passes through a 1:22 switching network 1424, which
couples the pilot signal to a selected MPA. Switching network 1424
includes switches, 2:4 hybrid couplers, and 2:6 hybrid couplers in
an arrangement that may be similar to that shown in FIG. 13. An
output is provided to a 1:4 hybrid coupler 1426 that splits the
pilot signal, which is then sent to couplers 1420a-d and is used
for calibration.
[0064] FIG. 15 illustrates an example of a method for calibrating
MPAs, e.g. MPAs in an amplification system in a satellite. An MPA
is selected 1550, for example, using a switching network. A pilot
signal is provided 1552 at an input port of the selected MPA (this
may be repeated for additional input ports). A pilot signal may be
provided at a frequency that is not in use, e.g. at the edge of an
allocated frequency band so that calibration may be performed in
parallel with receiving, amplifying, and transmitting regular
communications. Couplers between the amplification units and an
ONET provide amplified pilot signals from different amplification
pathways of the selected MPA to a calibration unit. Outputs from
different amplification units are compared 1554 with a reference
signal to obtain amplitude and phase differences. Analog-to-digital
conversion 1556 provides digital amplitude and phase data. This
digital data is sent 1558 to a recipient that may be on the ground,
or may be an adjustment unit on-board the satellite so that a
determination may be made as to whether adjustment is appropriate,
and if so, what adjustment to make. Gain and phase are then
adjusted 1560. The process of FIG. 15 may be performed periodically
during satellite operation with each MPA in a satellite being
checked on a predetermined schedule, or in response to some
trigger, such as an indication of power leakage. Between such
checks, calibration equipment may be powered-down to conserve
power.
[0065] According to one aspect of the present disclosure, an
amplifier system includes: an input network having a plurality of
input ports; an output network having a plurality of output ports;
a plurality of amplification units coupled between the input
network and the output network, the plurality of amplification
units configured to amplify signals from the plurality of input
ports; and a calibration unit coupled between the plurality of
amplification units and the output network to calibrate amplified
signals from the plurality of amplification units.
[0066] Optionally, the amplifier system may further include a
plurality of adjustment units disposed in series with the plurality
of amplification units. Optionally, the calibration unit may be
configured to obtain phase and amplitude data for the amplified
signals from the plurality of amplification units and the plurality
of adjustment units are configured to adjust phase and amplitude of
the signals amplified by the plurality of amplification units.
Optionally, the amplifier system may further include a pilot signal
generator coupled to an input port of the input network to provide
a pilot signal to the plurality of amplification units and wherein
the amplified signals are amplified pilot signals. Optionally, the
calibration unit may be configured to compare an amplified pilot
signal with a reference signal to obtain relative phase and
amplitude information for the amplified pilot signal. Optionally,
the reference signal is the pilot signal, or an amplified pilot
signal from a reference amplification unit. Optionally, the input
network, the output network, and the plurality of amplification
units are in a first multiport amplifier, the amplifier system
comprising a plurality of multiport amplifiers that includes the
first multiport amplifier, and the calibration unit is coupled to
the plurality of multiport amplifiers through a selector configured
to select an individual multiport amplifier of the plurality of
multiport amplifiers. Optionally, the amplifier further includes a
pilot signal generator coupled to the plurality of multiport
amplifiers through the selector. Optionally, the amplifier system
is embodied in a satellite.
[0067] According to one aspect of the present disclosure, a
satellite includes: a plurality of multiport amplifiers, an
individual multiport amplifier having a plurality of amplification
units coupled between an input network and an output network; a
pilot signal generator connected to the plurality of multiport
amplifiers to apply a pilot signal to an input port of a selected
multiport amplifier; and a calibration unit coupled to the
plurality of multiport amplifiers to receive and calibrate outputs
of the plurality of amplification units of the selected multiport
amplifier generated in response to the pilot signal.
[0068] Optionally, the selected multiport amplifier has n input
ports, n output ports, and n active amplification units, and the
calibration unit is coupled to outputs of the n amplification units
to receive amplified pilot signals generated in response to the
pilot signal applied to the input port of the selected multiport
amplifier. Optionally, the calibration unit comprises a mixer that
mixes an output of a selected amplification unit with a reference
signal to generate an output to indicate at least one of phase
difference and amplitude difference. Optionally, the reference
signal is an output of a reference amplification unit from the n
amplification units, and the calibration unit is configured to
compare outputs of each other amplification unit of the n
amplification units with the reference signal from the reference
amplification unit to obtain at least one of phase difference and
amplitude difference for each other amplification unit. Optionally,
the pilot signal generator is coupled to the calibration unit to
provide the pilot signal to the calibration unit as the reference
signal. Optionally, the satellite further includes an
analog-to-digital converter to convert an analog output from the
calibration unit representing at least one of phase and amplitude
information to a digital value. Optionally, the satellite further
includes a telemetry system configured to send telemetry
information from the satellite to a ground station and the
analog-to-digital converter is coupled to the telemetry system to
provide the digital value to the telemetry system to be sent to the
ground station. Optionally, the satellite further includes an
adjustment calculator coupled to the analog-to-digital converter to
receive the digital value, the adjustment calculator configured to
calculate adjustment to at least one of phase or gain of one or
more outputs of the plurality of amplification units. Optionally,
the plurality of amplification units may be Travelling Wave Tube
Amplifiers (TWTAs) or Solid-State Power Amplifiers (SSPAs).
[0069] According to one aspect of the present disclosure, a
satellite communications system including: a satellite having: one
or more multiport amplifiers, each of the one or more multiport
amplifiers having a plurality of amplification units connected in
parallel; a calibration unit selectively connected to the one or
more multiport amplifiers to calibrate outputs of the plurality of
amplification units of the one or more multiport amplifiers. The
communications system also includes: a user terminal configured to
communicate with the satellite using radio frequency (RF)
communication and a gateway connected to the Internet, the gateway
configured to communicate with the satellite using RF
communication.
[0070] Optionally, the satellite communication system further
includes a network control center configured to provide commands to
control the satellite, the network control center configured to
receive calibration data generated by the calibration unit and to
send commands to adjust the one or more multiport amplifiers.
[0071] For purposes of this document, it should be noted that the
dimensions of the various features depicted in the figures may not
necessarily be drawn to scale.
[0072] For purposes of this document, reference in the
specification to "an embodiment," "one embodiment," "some
embodiments," or "another embodiment" may be used to describe
different embodiments or the same embodiment.
[0073] For purposes of this document, a connection may be a direct
connection or an indirect connection (e.g., via one or more other
parts). In some cases, when an element is referred to as being
connected or coupled to another element, the element may be
directly connected to the other element or indirectly connected to
the other element via intervening elements. When an element is
referred to as being directly connected to another element, then
there are no intervening elements between the element and the other
element. Two devices are "in communication" if they are directly or
indirectly connected so that they can communicate electronic
signals between them.
[0074] For purposes of this document, the term "based on" may be
read as "based at least in part on."
[0075] For purposes of this document, without additional context,
use of numerical terms such as a "first" object, a "second" object,
and a "third" object may not imply an ordering of objects, but may
instead be used for identification purposes to identify different
objects.
[0076] For purposes of this document, the term "set" of objects may
refer to a "set" of one or more of the objects.
[0077] The foregoing detailed description has been presented for
purposes of illustration and description. It is not intended to be
exhaustive or to limit the subject matter claimed herein to the
precise form(s) disclosed. Many modifications and variations are
possible in light of the above teachings. The described embodiments
were chosen in order to best explain the principles of the
disclosed technology and its practical application to thereby
enable others skilled in the art to best utilize the technology in
various embodiments and with various modifications as are suited to
the particular use contemplated. It is intended that the scope of
be defined by the claims appended hereto.
* * * * *