Note: Descriptions are shown in the official language in which they were submitted.
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WIDE-BAND AUTOMATED GAIN CONTROL FOR BURSTY FRAMES
FIELD
[0001] Due to fluctuations in power from the received data, there is the need
for an
Automated Gain Control (AGC) to scale the power of the Wideband digital signal
coming into a
receiver to avoid saturations or over-scaling. The Wideband AGC (WB-AGC)
measures the
power of the incoming data, compares it to a reference power value, and
applies the appropriate
scaling to the inputs in order to achieve the desired power level.
BACKGROUND
[0002] The prior art did not have a state machine or power spike detector, as
it dealt with
continuous transmission.
SUMMARY
[0003] This Summary is provided to introduce a selection of concepts in a
simplified
form that is further described below in the Detailed Description. This Summary
is not intended
to identify key features or essential features of the claimed subject matter,
nor is it intended to be
used to limit the scope of the claimed subject matter.
[0004] In VLSNR conditions, the power of the desired received signal has a
higher
probability of being masked by the noise power. This has the potential of
driving the power
control to undesired levels if the AGC has no means of differentiating between
noise power vs
signal power. This is exacerbated in bursty frames applications, where the
power can fluctuate
suddenly at the input of the receiver. If not controlled, this can cause the
WB-AGC loop to
produce a very large gain when there is no signal present (as the incoming
power is low), and
cause saturations and signal loss once the signal power returns.
[0005] A system of one or more computers can be configured to perform
particular
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operations or actions by virtue of having software, firmware, hardware, or a
combination of them
installed on the system that in operation causes or cause the system to
perform the actions. One
or more computer programs can be configured to perform particular operations
or actions by
virtue of including instructions that, when executed by data processing
apparatus, cause the
apparatus to perform the actions. One general aspect includes a method to
provide adaptive
power control for a Wide Band Automatic Gain Control (WB-AGC) including:
determining a
signal is present when a power derivative of the signal ramps up; adapting a
gain for an
Automated Gain Control (AGC) when the signal is present; and disabling the
adapting when the
signal is not present. Other embodiments of this aspect include corresponding
computer systems,
apparatus, and computer programs recorded on one or more computer storage
devices, each
configured to perform the actions of the methods.
[0006] Implementations may include one or more of the following features.
Implementations of the described techniques may include hardware, a method or
process, or
computer software on a computer-accessible medium.
[0007] The method may include measuring a power of the signal.
[0008] The method may include detecting a pattern of on, off, on for the
signal, wherein
the adapting is enabled after the detecting has detected the pattern.
[0009] The method where a duration of the pattern is greater than a threshold
duration.
100101 The method where a duration of the pattern is increased in a noisy
environment.
100111 The method where the determining includes computing the power
derivative of
the signal, and a positive non-zero value for the power derivative indicates
the signal is present.
[0012] The method where the determining includes computing the power
derivative of
the signal, and a non-zero value for the power derivative indicates a power
change in the signal.
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100131 The method may include filtering the signal to reduce noise prior to
the
determining.
100141 The method may include subtracting the signal from a previous capture
of the
signal prior to the determining.
100151 The method where the signal includes multiple carriers.
100161 The method where the signal includes bursts.
100171 The method where after the disabling, the adapting includes setting an
AGC start
value to a last-known gain used prior to the disabling.
100181 The method where the last known gain is associated with a transmitter
of the
signal.
100191 The method where the signal has a signal-to-noise ratio ranging from
20dB to -
1 OdB
100201 The method where the signal has a negative dB signal-to-noise ratio.
100211 Additional features will be set forth in the description that follows,
and in part
will be apparent from the description, or may be learned by practice of what
is described
DRAWINGS
100221 In order to describe the manner in which the above-recited and other
advantages
and features may be obtained, a more particular description is provided below
and will be
rendered by reference to specific embodiments thereof which are illustrated in
the appended
drawings. Understanding that these drawings depict only typical embodiments
and are not,
therefore, to be limiting of its scope, implementations will be described and
explained with
additional specificity and detail with the accompanying drawings.
100231 FIG. 1 illustrates a functionality of an adaptive control according to
various
embodiments.
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[0024] FIG. 2 illustrates a process to provide adaptive power control for a
Wide Band
Automatic Gain Control (WB-AGC) according to various embodiments.
[0025] Throughout the drawings and the detailed description, unless otherwise
described,
the same drawing reference numerals will be understood to refer to the same
elements, features,
and structures. The relative size and depiction of these elements may be
exaggerated for clarity,
illustration, and convenience.
DETAILED DESCRIPTION
[0026] The present teachings may be a system, a method, and/or a computer
program
product at any possible technical detail level of integration. The computer
program product may
include a computer readable storage medium (or media) having computer readable
program
instructions thereon for causing a processor to carry out aspects of the
present invention.
100271 The computer readable storage medium can be a tangible device that can
retain
and store instructions for use by an instruction execution device. The
computer readable storage
medium may be, for example, but is not limited to, an electronic storage
device, a magnetic
storage device, an optical storage device, an electromagnetic storage device,
a semiconductor
storage device, or any suitable combination of the foregoing. A non-exhaustive
list of more
specific examples of the computer readable storage medium includes the
following: a portable
computer diskette, a hard disk, a random access memory (RAI\4), a read-only
memory (ROM),
an erasable programmable read-only memory (EPROM or Flash memory), a static
random
access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a
digital
versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded
device such as
punch-cards or raised structures in a groove having instructions recorded
thereon, and any
suitable combination of the foregoing. A computer readable storage medium, as
used herein, is
not to be construed as being transitory signals per se, such as radio waves or
other freely
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propagating electromagnetic waves, electromagnetic waves propagating through a
waveguide or
other transmission media (e.g., light pulses passing through a fiber-optic
cable), or electrical
signals transmitted through a wire.
100281 Computer readable program instructions described herein can be
downloaded to
respective computing/processing devices from a computer readable storage
medium or to an
external computer or external storage device via a network, for example, the
Internet, a local area
network, a wide area network and/or a wireless network. The network may
comprise copper
transmission cables, optical transmission fibers, wireless transmission,
routers, firewalls,
switches, gateway computers and/or edge servers. A network adapter card or
network interface
in each computing/processing device receives computer readable program
instructions from the
network and forwards the computer readable program instructions for storage in
a computer
readable storage medium within the respective computing/processing device.
100291 Computer readable program instructions for carrying out operations of
the present
invention may be assembler instructions, instruction-set-architecture (ISA)
instructions, machine
instructions, machine dependent instructions, microcode, firmware
instructions, state-setting
data, or either source code or object code written in any combination of one
or more
programming languages, including an object oriented programming language such
as
SMALLTALK, C++ or the like, and conventional procedural programming languages,
such as
the "C" programming language or similar programming languages. The computer
readable
program instructions may execute entirely on the user's computer, partly on
the user's computer,
as a stand-alone software package, partly on the user's computer and partly on
a remote computer
or entirely on the remote computer or server. In the latter scenario, the
remote computer may be
connected to the user's computer through any type of network, including a
local area network
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(LAN) or a wide area network (WAN), or the connection may be made to an
external computer
(for example, through the Internet using an Internet Service Provider). In
some embodiments,
electronic circuitry including, for example, programmable logic circuitry,
field-programmable
gate arrays (FPGA), or programmable logic arrays (PLA) may execute the
computer readable
program instructions by utilizing state information of the computer readable
program instructions
to personalize the electronic circuitry, in order to perform aspects of the
present invention.
100301 Aspects of the present invention are described herein with reference to
flowchart
illustrations and/or block diagrams of methods, apparatus (systems), and
computer program
products according to embodiments of the invention. It will be understood that
each block of the
flowchart illustrations and/or block diagrams, and combinations of blocks in
the flowchart
illustrations and/or block diagrams, can be implemented by computer readable
program
instructions
100311 These computer readable program instructions may be provided to a
processor of
a general purpose computer, special purpose computer, or other programmable
data processing
apparatus to produce a machine, such that the instructions, which execute via
the processor of the
computer or other programmable data processing apparatus, create means for
implementing the
functions/acts specified in the flowchart and/or block diagram block or
blocks. These computer
readable program instructions may also be stored in a computer readable
storage medium that
can direct a computer, a programmable data processing apparatus, and/or other
devices to
function in a particular manner, such that the computer readable storage
medium having
instructions stored therein comprises an article of manufacture including
instructions which
implement aspects of the function/act specified in the flowchart and/or block
diagram block or
blocks.
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100321 The computer readable program instructions may also be loaded onto a
computer,
other programmable data processing apparatus, or other device to cause a
series of operational
steps to be performed on the computer, other programmable apparatus or other
device to produce
a computer implemented process, such that the instructions which execute on
the computer, other
programmable apparatus, or other device implement the functions/acts specified
in the flowchart
and/or block diagram block or blocks.
100331 The flowchart and block diagrams in the Figures illustrate the
architecture,
functionality, and operation of possible implementations of systems, methods,
and computer
program products according to various embodiments of the present invention. In
this regard,
each block in the flowchart or block diagrams may represent a module, segment,
or portion of
instructions, which comprises one or more executable instructions for
implementing the specified
logical function(s). In some alternative implementations, the functions noted
in the block may
occur out of the order noted in the figures. For example, two blocks shown in
succession may, in
fact, be executed substantially concurrently, or the blocks may sometimes be
executed in the
reverse order, depending upon the functionality involved. It will also be
noted that each block of
the block diagrams and/or flowchart illustration, and combinations of blocks
in the block
diagrams and/or flowchart illustration, can be implemented by special purpose
hardware-based
systems that perform the specified functions or acts or carry out combinations
of special purpose
hardware and computer instructions.
100341 Reference in the specification to "one embodiment" or "an embodiment"
of the
present invention, as well as other variations thereof, means that a feature,
structure,
characteristic, and so forth described in connection with the embodiment is
included in at least
one embodiment of the present invention. Thus, the appearances of the phrase
"in one
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embodiment" or "in an embodiment", as well any other variations, appearing in
various places
throughout the specification are not necessarily all referring to the same
embodiment.
100351 The WB-AGC accounts for Very Low SNR (VLSNR) conditions, for example,
down to -10dB SNR. The WB-AGC may be used in applications where an input
signal to the
receiver is switched on/off, hindering its ability to appropriately adjust the
power. One such
application uses bursty frames.
100361 In some embodiments, the transmitter of the signal may be a satellite,
and the
receiver of the signal may be Very Small Aperture Terminal (VSAT). The
transmitter may
multiplex the signal using time division. The time division multiplexing may
be a function of
time hopping the signal between beams, enabling or displaying coverage of a
beam coverage
area, moving between different beam coverage areas, moving between a satellite
coverage area
and a satellite non-coverage area, or the like. The time division multiplexing
of the signal may
be of a fixed or variable duration.
100371 After determining a signal is present, the WB-AGC may set a gain of the
AGC to
a last-known gain value when adapting a gain for the AGC In some embodiments,
the last-
known value may be associated with a specific transmitter. For example, when a
transmitter of
the signal changes in a known pattern a respective last-known value of the
gain may be
associated and used when adapting the AGC of the signal from the respective
transmitter.
Exemplary transmitters changing in a known pattern include constellations of
Low-Earth Orbit
(LEO) and Mid-Earth Orbit (MEO) satellites.
100381 The present teachings can handle carriers with alternate coding and
modulation
(ACM), for example, BPSK, 8PSK, 16APSK, 32APSK, 64APSK, and 256APSK
constellations.
These carriers may be packaged according to a standard, for example, DVBS2/2X
standard. The
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carriers may appear as either continuous or bursty frames to the receiver. The
bursts may be
encapsulated in a "superframe" format. The superframe may be of a fixed sized
length. In some
embodiments, variable sized superframes are supported.
[0039] The WB-AGC may track the power of the incoming bursts, with or without
superframes, fixed or variable superframe sizes, with a signal-to-noise ratio
ranging from 20dB
to -10dB. The WB-AGC may handle multiple carriers of this format, in a
frequency band, for
example, a frequency band of up to 2Gsps.
[0040] The new WB-AGC may include a power detector, lock detector and state
machine. The WB-AGC halts the adaptation of the loop when sudden power changes
occur. It
determines the presence of signal ON (signal + noise power), or OFF (only
noise power) and
reacts to its presence. The WB-AGC is geared towards the acquisition process,
when the receiver
is turned on and information packets/bursts/frames have not yet been acquired
or locked-on In
this initial scenario the receiver cannot estimate a system-based time of when
to turn off the gain
adaptation. The WB-AGC state machine may take control of the loop adaptation
during the
acquisition time and cede control once "demod-lock" has occurred.
[0041] The WB-AGC detects power drops/surges by computing a derivative of the
incoming signal power. The input signal power is measured or computed,
filtered to reduce
noise, and subtracted against the previous captures. This produces a power
derivative. Its
absolute value indicates a sudden power change, and its sign indicates whether
the signal is OFF
(not present) or ON (present). A state machine can decide whether to start or
stop the gain loop
adaptation based on the power derivative.
[0042] FIG. 1 illustrates a functionality of an adaptive control according to
various
embodiments.
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[0043] FIG. 1 illustrates a functional visualization of an adaptive control
100 of a WB-
AGC. In some embodiments, the adaptive control 100 in a WB-AGC includes one or
more
states. The visualization includes a power measurement 102 (present, falling,
not present,
rising), a power derivative line 104 (d(Power)/dx as constant, negative,
positive), and an
adaption line 106 (toggle allowing adaptation of gain by WB-AGC).
[0044] In state 1, a signal is present per a portion of power measurement 102
within state
1 that indicates signal presence. The power is constant and a portion of power
derivative 104
within state 1 is zero. As such, the adaptive control 100 sets adaptation to
off per adaption line
106 within state 1. With the adaptation being off, a gain applied to the
signal does not change.
[0045] In state 2, a signal is not present and is ramping down per a portion
of power
measurement 102 within state 2. A duration of the signal ramp down may be
based on a loop
bandwidth. As such, a portion of power derivative 104 within state 2 spikes
down. The adaptive
control 100 disables or sets adaptation to off per a portion of adaption line
106 within state 2.
With the adaptation being off, a gain to be applied to the signal does not
change.
[0046] In state 3, a signal is not present per a portion of power measurement
102 within
state 3. The power is constant and a portion of power derivative 104 within
state 3 is zero. As
such, adaptation is turned off per a portion of adaptation line 106 within
state 3. With the
adaptation being off, a gain applied to the signal does not change.
[0047] In state 4, a signal is present and ramping up per a portion of power
measurement
102 within state 4. As such, a portion of power derivative 104 within state 4
spikes up. When a
state machine has determined a pattern of ON, OFF, ON, for example, at time to
in state 4,
adaptation is turned on per a portion of adaption line 106 within state 4. As
such, a gain of the
WB-ABC is allowed to adapt. In case of misdetection, (for example, a power
drop is detected
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instead of a power surge) the adaptive control 100 may return to state 1 and
may resume on
trying to detect a pattern.
[0048] In state 5, a signal is present per a portion of power measurement 102
within state
4. Further to adaptation being turned on in state 4, the adaptation is kept
turned on (gain adapts)
while a signal is present is indicated. When a signal absence is determined
per the power
measurement 102, the adaptive control 100 returns to state 2.
[0049] Programmable detection/misdetection counters and thresholds may be used
to
manage an operation of the state machine 100. The counter values indicate the
amount of "time"
(measured in clock instances) that the -event", defined as the power
derivative value being above
or below a threshold, should occur to declare a "success" when a declaring
power surge (signal
ON) or power drop (signal OFF).
[0050] In some embodiments, a power surge/drop detection can be made more
robust for
noisy environments. In some embodiments, a power surge/drop detection can be
made less
robust for low-noise environments. For low-noise environments, there is a high
probability that a
power surge/drop declaration is not a miss-detection. In this case the
detection counters can be
set to lower values, decreasing the latency of detection. This is in contrast
to high-noise
environments where these counters should be set to higher values as haying
only 1 event is not a
probabilistic measure of success.
[0051] During operation, noise may be at 0 dBFS at a maximum gain of the WB-
AGC.
In some embodiments, the WB-AGC may have a range of up to 72dB.
100521 FIG. 2 illustrates a process to provide adaptive power control for a
Wide Band
Automatic Gain Control (WB-AGC) according to various embodiments.
[0053] A process 200 may include operation 202 to determine a signal is
present when a
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power derivative of the signal ramps up. The process 200 may include operation
204 to adapt a
gain for an AGC when the signal is present. The process 200 may include
operation 204 to
disable the adapting when the signal is not present. The process 200 may
include operation 208
to detect a pattern of on, off, on for the signal. The process 200 may include
operation 210 to
filter the signal to reduce noise. The process 200 may include operation 212
to subtract the
signal from a previous capture of the signal.
100541 Having described preferred embodiments of a system and method (which
are
intended to be illustrative and not limiting), it is noted that modifications
and variations can be
made by persons skilled in the art considering the above teachings. It is
therefore to be
understood that changes may be made in the embodiments disclosed which are
within the scope
of the invention as outlined by the appended claims. Having thus described
aspects of the
invention, with the details and particularity required by the patent laws,
what is claimed and
desired protected by Letters Patent is set forth in the appended claims.
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