U.S. patent application number 15/244332 was filed with the patent office on 2017-03-30 for wireless device.
This patent application is currently assigned to FUJITSU LIMITED. The applicant listed for this patent is FUJITSU LIMITED. Invention is credited to Ryosuke Kobayashi, Shin WATANABE.
Application Number | 20170093445 15/244332 |
Document ID | / |
Family ID | 58337244 |
Filed Date | 2017-03-30 |
United States Patent
Application |
20170093445 |
Kind Code |
A1 |
Kobayashi; Ryosuke ; et
al. |
March 30, 2017 |
WIRELESS DEVICE
Abstract
A distortion compensation unit compensates distortion in the
amplifier by using a distortion compensation coefficient that is in
accordance with a power value of a signal before amplification in
the amplifier. An updating unit updates, on the basis of the signal
before amplification in the amplifier and a signal after
amplification in the amplifier, the distortion compensation
coefficient. An extracting unit extracts, at a predetermined number
of measurement periods, when the power value of the signal before
amplification in the amplifier is equal to or greater than a
threshold, the distortion compensation coefficient that is in
accordance with the power value. A first calculating unit
calculates, by using an average value of the extracted distortion
compensation coefficients, an amount of variation in the distortion
compensation coefficient. A determination unit determines, on the
basis of the calculated amount of variation in the distortion
compensation coefficient, whether the amplifier is degraded.
Inventors: |
Kobayashi; Ryosuke;
(Kawasaki, JP) ; WATANABE; Shin; (Yokohama,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FUJITSU LIMITED |
Kawasaki-shi |
|
JP |
|
|
Assignee: |
FUJITSU LIMITED
Kawasaki-shi
JP
|
Family ID: |
58337244 |
Appl. No.: |
15/244332 |
Filed: |
August 23, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04B 1/0475 20130101;
H04B 2001/0425 20130101 |
International
Class: |
H04B 1/04 20060101
H04B001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 30, 2015 |
JP |
2015-193321 |
Claims
1. A wireless device comprising: an amplifier that amplifies a
signal that is wirelessly transmitted; and a processor configured
to: compensate distortion in the amplifier by using a distortion
compensation coefficient that is stored in a distortion
compensation table and that is in accordance with a power value of
the signal before amplification in the amplifier; update, on the
basis of an error between the signal before the amplification in
the amplifier and an amplified signal after the amplification in
the amplifier, the distortion compensation coefficient stored in
the distortion compensation table; extract, at a predetermined
number of measurement periods, from the distortion compensation
table when the power value of the signal before the amplification
in the amplifier is equal to or greater than a threshold, the
distortion compensation coefficient that is in accordance with the
power value; calculate, by using an average value of distortion
compensation coefficients extracted at the predetermined number of
measurement periods, an amount of variation in the distortion
compensation coefficient with respect to an initial value of the
distortion compensation coefficient; and determine, on the basis of
the calculated amount of variation in the distortion compensation
coefficient, whether the amplifier is degraded.
2. The wireless device according to claim 1, wherein the processor
is further configured to derive, on the basis of the calculated
amount of variation in the distortion compensation coefficient, a
prediction line of the amount of variation to predict, by using the
derived prediction line, a time at which the amount of variation
reaches a predetermined threshold.
3. The wireless device according to claim 2, wherein the the
processor is further configured to output, in stages by using the
prediction line, an alarm in accordance with the amount of
variation before the amount of variation in the distortion
compensation coefficient reaches the predetermined threshold.
4. The wireless device according to claim 1, wherein the processor
is further configured to: measure a temperature of the wireless
device; and acquire the initial value of the distortion
compensation coefficient that is in accordance with the measured
temperature to calculate the amount of variation in the distortion
compensation coefficient with respect to the acquired initial
value.
5. The wireless device according to claim 1, wherein the processor
is further configured to: acquire, when the power value of the
signal before the amplification in the amplifier is equal to or
greater than the threshold, at a predetermined number of
measurement periods, a frequency spectrum of the signal after the
amplification in the amplifier; average frequency spectra acquired
at the predetermined number of measurement periods to calculate, by
using a frequency spectrum obtained by the frequency spectra being
averaged, an amount of variation in a bandwidth of the signal after
amplification in the amplifier with respect to an initial value of
the bandwidth; and determine, on the basis of the calculated amount
of variation in the bandwidth, whether the amplifier is
degraded.
6. The wireless device according to claim 5, wherein the processor
is further configured to derive, on the basis of the calculated
amount of variation in the bandwidth, a prediction line of the
amount of variation to predict, by using the derived prediction
line, a time at which the amount of variation reaches a
predetermined threshold.
7. The wireless device according to claim 6, wherein the processor
is further configured to output, in stages by using the prediction
line, an alarm in accordance with the amount of variation before
the amount of variation in the bandwidth reaches the predetermined
threshold.
8. The wireless device according to claim 5, wherein the processor
is further configured to: measure a temperature of the wireless
device; and acquire the initial value of the bandwidth that is in
accordance with the measured temperature to calculate the amount of
variation in the bandwidth with respect to the acquired initial
value.
9. The wireless device according to claim 5, wherein the processor
is further configured to change the initial value of the distortion
compensation coefficient or the initial value of the bandwidth in
accordance with number of carriers that are used for radio
transmission.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims the benefit of
priority of the prior Japanese Patent Application No. 2015-193321,
filed on Sep. 30, 2015, the entire contents of which are
incorporated herein by reference.
FIELD
[0002] The embodiment discussed herein is related to a wireless
device.
BACKGROUND
[0003] Conventionally, for example, in radio communication devices,
such as base station devices or the like, due to aged deterioration
of amplifiers in the devices or the like, the gain of the
amplifiers may sometimes vary. Furthermore, in recent radio
communication devices, studies have been conducted on a system in
which a radio equipment control (REC) device that mainly performs a
baseband process is connected, by using optical fibers, to radio
equipment (RE) devices that mainly perform a radio process. The
connection between the REC device and the RE devices is performed
in accordance with, for example, an interface called a Common
Public Radio Interface (CPRI).
[0004] In the radio communication devices, for example, because the
gain prescribed by law is expected to be observed, in general, a
periodic inspection is performed to determine whether the gain of
an amplifier described above is within the range that satisfies the
prescription. However, because the base station devices and the RE
devices are often arranged at a high place, such as on the roof of
a building, on a steel tower, or the like, the efficiency of
checking the gain of the amplifiers in these devices by maintenance
workers on site is low and the cost is increased.
[0005] Thus, studies have been conducted on various kinds of
technologies in which a base station device or a RE device itself
determines deterioration of an amplifier in the device. For
example, it is conceivable to extract, in a device that has a
distortion compensation function that compensates nonlinear
distortion generated in an amplifier, a distortion compensation
coefficient in accordance with a power value of the most frequently
appearing radio signal, obtains an amount of variation in the
distortion compensation coefficient that was extracted in the past,
and determines, on the basis of the obtained amount of variation,
the degradation of the amplifier.
[0006] Patent Document 1: Japanese Laid-open Patent Publication No.
2002-232305
[0007] However, if the degradation of the amplifier is determined
by extracting the distortion compensation coefficient that is in
accordance with the power value of the most frequently appearing
radio signal, the frequency of appearance of the power value of the
radio signal varies due to the location of the device that is
placed or due to a use time zone of the device and thus the power
value of the radio signal may possibly deviate from the nonlinear
operation area of the amplifier. Here, when measuring variation of
the gain that is used to determine the degradation of the
amplifier, for example, it is prescribed by law that the power
value of the radio signal needs to be present in a nonlinear
operation area of the amplifier, i.e., it is prescribed by law that
the power value of the radio signal needs to be equal to or greater
than the threshold. Consequently, when the distortion compensation
coefficient that is in accordance with the power value of the most
frequently appearing radio signal is extracted, because the
variation of the gain may possibly be measured by using the
distortion compensation coefficient that is in accordance with the
power value that does not satisfy the prescription of law, it is
difficult to appropriately determine the degradation of the
amplifier.
SUMMARY
[0008] According to an aspect of an embodiment, a wireless device
includes an amplifier that amplifies a signal that is wirelessly
transmitted; a distortion compensation unit that compensates
distortion in the amplifier by using a distortion compensation
coefficient that is stored in a distortion compensation table and
that is in accordance with a power value of a signal before
amplification in the amplifier; an updating unit that updates, on
the basis of an error between the signal before the amplification
in the amplifier and a signal after the amplification in the
amplifier, the distortion compensation coefficient stored in the
distortion compensation table; an extracting unit that extracts, at
a predetermined number of measurement periods, from the distortion
compensation table when the power value of the signal before the
amplification in the amplifier is equal to or greater than a
threshold, the distortion compensation coefficient that is in
accordance with the power value; a first calculating unit that
calculates, by using an average value of distortion compensation
coefficients extracted at the predetermined number of measurement
periods, an amount of variation in the distortion compensation
coefficient with respect to an initial value of the distortion
compensation coefficient; and a determination unit that determines,
on the basis of the calculated amount of variation in the
distortion compensation coefficient, whether the amplifier is
degraded.
[0009] The object and advantages of the invention will be realized
and attained by means of the elements and combinations particularly
pointed out in the claims.
[0010] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory and are not restrictive of the invention, as
claimed.
BRIEF DESCRIPTION OF DRAWINGS
[0011] FIG. 1 is a block diagram illustrating the configuration of
a radio communication system according to an embodiment;
[0012] FIG. 2 is a block diagram illustrating the configuration of
a RE device according to the embodiment;
[0013] FIG. 3 is a block diagram illustrating the configuration of
an FPGA according to the embodiment;
[0014] FIG. 4 is a schematic diagram illustrating an example of
time fluctuation of a power value of a BB signal;
[0015] FIG. 5 is a schematic diagram illustrating an example of a
first association table in which the measurement temperature is
associated with an initial value of a distortion compensation
coefficient that is in accordance with each of the measurement
temperatures;
[0016] FIG. 6 is a schematic diagram illustrating an example of a
calculation process of the average value of distortion compensation
coefficients extracted from an LUT at the measurement time of a
predetermined number of measurements;
[0017] FIG. 7 is a schematic diagram illustrating an example of a
calculation process of an amount of variation in distortion
compensation coefficients;
[0018] FIG. 8 is a schematic diagram illustrating an example of a
calculation process of an amount of variation in the bandwidth of
an FB signal;
[0019] FIG. 9 is a flowchart illustrating an example of an
amplifier deterioration determination process according to the
embodiment;
[0020] FIG. 10 is a schematic diagram illustrating a specific
example of a prediction line of an amount of variation in the
distortion compensation coefficients;
[0021] FIG. 11 is a flowchart illustrating another example of an
amplifier deterioration determination process according to the
embodiment;
[0022] FIG. 12 is a schematic diagram illustrating a specific
example of a prediction line of an amount of variation in the
bandwidth of an FB signal; and
[0023] FIG. 13 is a schematic diagram illustrating variation of the
distortion compensation coefficients in accordance with the number
of carriers.
DESCRIPTION OF EMBODIMENTS
[0024] Preferred embodiments of the present invention will be
explained with reference to accompanying drawings. The disclosed
technology is not limited to the embodiment. Furthermore, in the
embodiment described below, components having the same function are
assigned the same reference numerals and descriptions of overlapped
portions will be omitted.
[0025] FIG. 1 is a block diagram illustrating the configuration of
a radio communication system according to an embodiment. The radio
communication system illustrated in FIG. 1 includes a REC device 10
and a plurality of RE devices 100 connected to the REC device 10.
Furthermore, a monitoring device 30 is connected to the REC device
10. Furthermore, the connection between the REC device 10 and the
plurality of the RE devices 100 is performed by conforming to the
interface called, for example, a CPRI.
[0026] The REC device 10 performs a baseband process on
transmission data. For example, the REC device 10 performs the
baseband process, such as an encoding process, a modulation
process, or the like, on the transmission data and sends the
obtained baseband signal to each of the RE devices 100.
[0027] The monitoring device 30 monitors the state of the REC
device 10 and the RE device 100 and notifies a user whether, for
example, a maintenance checkup, such as a replacement of a part, is
needed. Specifically, if, for example, an amplifier included in one
of the RE devices 100 is degraded, the monitoring device 30
generates an alarm that indicates the subject status.
[0028] Each of the RE devices 100 is connected to the REC device 10
via optical fibers and performs a radio process on the transmission
data. For example, each of the RE devices 100 performs
digital-to-analog (DA) conversion and up-conversion on the baseband
signal that is received from the REC device 10 and then sends the
obtained radio signal via the antenna.
[0029] FIG. 2 is a block diagram illustrating the configuration of
a RE device according to the embodiment. In FIG. 2 mainly
illustrates the configuration related to transmission and does not
illustrate the configuration related to reception. The RE device
100 illustrated in FIG. 2 includes a multiplier 101, a DA converter
102, an oscillator 103, a modulator 104, a power amplifier (PA)
105, an oscillator 106, a mixer 107, and an AD converter 108.
Furthermore, the RE device 100 includes, as a processor, in
addition to a field programmable gate array (FPGA) 109 and a
central processing unit (CPU) 110, a memory 111.
[0030] The multiplier 101 multiplies the distortion compensation
coefficient that is output from the FPGA 109 with respect to the
baseband signal (hereinafter, referred to as a "BB signal") that is
received from the REC device 10 and then performs distortion
compensation on the BB signal. Namely, the multiplier 101 functions
as a distortion compensation unit. The distortion compensation
coefficient is a coefficient that is used to compensate the
nonlinear distortion generated in the PA 105. The multiplier 101
outputs, to the DA converter 102, the BB signal that has been
subjected to distortion compensation.
[0031] The DA converter 102 performs DA conversion on the BB signal
that has been subjected to distortion compensation and then outputs
the obtained analog BB signal to the modulator 104.
[0032] The oscillator 103 generates a local signal with a radio
frequency by using a clock of the BB signal.
[0033] The modulator 104 up-converts an analog BB signal by using
the local signal generated in the oscillator 103.
[0034] The PA 105 amplifies the signal that is up-converted by the
modulator 104 and sends the up-converted signal to the antenna.
[0035] The oscillator 106 generates a local signal with the
intermediate frequency by using a clock of the BB signal.
[0036] The mixer 107 down-converts a feedback signal (hereinafter,
referred to as an "FB signal") that is fed back from the PA 105 by
using the local signal generated in the oscillator 106.
[0037] The AD converter 108 performs AD conversion on the FB signal
that is down-converted by the mixer 107 and then outputs the
obtained digital FB signal to the FPGA 109.
[0038] The FPGA 109 refers to a look-up table (hereinafter,
referred to as a "LUT") that stores therein distortion compensation
coefficients and outputs the distortion compensation coefficient
that is in accordance with the power value of the BB signal to the
multiplier 101. Furthermore, the FPGA 109 updates, on the basis of
the FB signal that is output from the AD converter 108, the
distortion compensation coefficients stored in the LUT.
Furthermore, if the power value of the BB signal is equal to or
greater than a threshold, the FPGA 109 extracts, at the measurement
time of the predetermined number of measurements from the LUT, the
distortion compensation coefficients and calculates, by using the
average value of the extracted distortion compensation
coefficients, an amount of variation in the distortion compensation
coefficient with respect to the initial value. Furthermore, if the
power value of the BB signal is equal to or greater than the
threshold, the FPGA 109 acquires the frequency spectra of the FB
signal at the measurement time of the predetermined number of
measurements and then calculates, by using the averaged frequency
spectrum, an amount of variation in the bandwidth of the FB signal
with respect to the initial value. Here, the BB signal is an
example of a signal before amplification in the PA 105 and the FB
signal is an example of a signal after amplification in the PA 105.
Furthermore, a specific configuration of the FPGA 109 will be
described in detail later.
[0039] The CPU 110 determines the degradation of the PA 105 on the
basis of the amount of variation in the distortion compensation
coefficient or on the basis of the amount of variation in the
bandwidth of the FB signal calculated by the FPGA 109. For example,
if the amount of variation in the distortion compensation
coefficient is equal to or greater than the threshold, the CPU 110
determines that the PA 105 is degraded and, if the amount of
variation in the distortion compensation coefficient is less than
the threshold, the CPU 110 determines that the PA 105 is not
degraded.
[0040] Furthermore, the CPU 110 notifies the monitoring device 30
via the REC device 10 of the information related to the
determination result indicating whether the PA 105 is degraded. At
this point, the CPU 110 may also derive a prediction line of the
amount of variation on the basis of, for example, the calculated
amount of variation in the distortion compensation coefficient and
notify the monitoring device 30 of the remaining time before the
amount of variation in the distortion compensation coefficient
reaches a predetermined threshold.
[0041] The memory 111 temporarily stores therein various kinds of
information that is used for a process executed by the CPU 110.
[0042] FIG. 3 is a block diagram illustrating the configuration of
an FPGA according to the embodiment. The FPGA 109 illustrated in
FIG. 3 includes a LUT 201, a delay device 202, an oscillator 203, a
mixer 204, a comparator 205, and a computing unit 206. Furthermore,
the FPGA 109 includes an electrical power measuring unit 207, a
coefficient extracting unit 208, a memory 209, a temperature
measuring unit 210, and a coefficient variation amount calculating
unit 211. Furthermore, the FPGA 109 includes a fast Fourier
transformation (FFT) processing unit 212, a memory 213, and a
bandwidth variation amount calculating unit 214.
[0043] The LUT 201 stores therein distortion compensation
coefficients associated with the power values of the BB signal and
outputs, if the BB signal is input to the FPGA 109, the distortion
compensation coefficient that is associated with the power value of
the input BB signal to the multiplier 101. Namely, the LUT 201
functions as a distortion compensation table.
[0044] The delay device 202 makes the BB signal that is input to
the FPGA 109 delay and matches the FB signal that is fed back to
the FPGA 109 to the phase. Namely, the delay device 202 temporarily
holds the BB signal and makes the BB signal delay such that the
associated BB signal and FB signal are compared by the comparator
205.
[0045] The oscillator 203 generates a local signal with a frequency
that is used to remove a carrier component in the FB signal.
[0046] The mixer 204 removes a carrier component from the FB signal
by using the local signal generated in the oscillator 203. Namely,
by removing the carrier component from the FB signal, the mixer 204
extracts the FB signal that can be compared with the BB signal.
[0047] The comparator 205 compares the BB signal with the FB signal
and outputs an error between both the signals to the computing unit
206.
[0048] The computing unit 206 calculates a distortion compensation
coefficient that makes the error output from the comparator 205
approach zero and updates the LUT 201 by using the calculated
distortion compensation coefficient. Namely, the computing unit 206
functions as an updating unit and updates the distortion
compensation coefficients stored in the LUT 201 such that an error
between the BB signal and the baseband component of the FB signal
becomes zero. Consequently, an accuracy of the distortion
compensation coefficients is improved and the nonlinear distortion
generated in the PA 105 can be efficiently compensated.
[0049] The electrical power measuring unit 207 measures the power
value of the BB signal and outputs the measured power value of the
BB signal to both the coefficient extracting unit 208 and the FFT
processing unit 212. The power value of the BB signal measured by
the electrical power measuring unit 207 varies in accordance with,
for example, time, as illustrated in FIG. 4. FIG. 4 is a schematic
diagram illustrating an example of time fluctuation of a power
value of a BB signal. It is assumed that the threshold illustrated
in FIG. 4 is a threshold that divides the area into the nonlinear
operation area and the linear operation area of the PA 105. Namely,
the power value of the BB signal becomes equal to or greater than
the threshold at a certain time; is present in the nonlinear
operation area of the PA 105; becomes less than the threshold at
another time that is different from the certain time; and is
present in the linear operation area of the PA 105. When measuring
variation of the gain that is used to determine the degradation of
the amplifier, such as the PA 105 or the like, for example, it is
prescribed by law that the power value of the radio signal is
present in the nonlinear operation area of the amplifier, i.e., it
is prescribed by law that the power value of the radio signal is
equal to or greater than the "threshold". Namely, if the power
value of the BB signal is less than the threshold, the prescription
of law is not satisfied.
[0050] The coefficient extracting unit 208 monitors the power value
of the BB signal measured by the electrical power measuring unit
207 and, if the power value of the BB signal is equal to or greater
than the threshold (for example, the threshold illustrated in FIG.
4), the coefficient extracting unit 208 extracts, from the LUT 201
at the measurement time of the predetermined number of
measurements, the distortion compensation coefficients that are in
accordance with the power value of the BB signal. Then, the
coefficient extracting unit 208 outputs, to the memory 209, the
distortion compensation coefficients extracted from the LUT 201 at
the measurement time of the predetermined number of
measurements.
[0051] The memory 209 stores therein the distortion compensation
coefficients extracted by the coefficient extracting unit 208 from
the LUT 201 for each measurement time.
[0052] The temperature measuring unit 210 measures the temperature
of the RE device 100 and outputs the measured temperature to both
the coefficient variation amount calculating unit 211 and the
bandwidth variation amount calculating unit 214. In a description
below, the temperature that is output from the temperature
measuring unit 210 to both the coefficient variation amount
calculating unit 211 and the bandwidth variation amount calculating
unit 214 is referred to as a "measurement temperature".
[0053] The coefficient variation amount calculating unit 211
calculates an amount of variation in the distortion compensation
coefficient with respect to the initial value by using the
distortion compensation coefficients stored in the memory 209,
i.e., by using the average value of the distortion compensation
coefficients extracted from the LUT 201 at the measurement time of
the predetermined number of measurements. At this point, the
coefficient variation amount calculating unit 211 may also change
the initial value of the distortion compensation coefficient in
accordance with the "measurement temperature" from the temperature
measuring unit 210 and calculate an amount of variation in the
distortion compensation coefficient of the changed initial value.
The amount of variation in the distortion compensation coefficient
calculated by the coefficient variation amount calculating unit 211
is output to the CPU 110.
[0054] In the following, an example of the process performed by the
coefficient variation amount calculating unit 211 will be described
with reference to FIGS. 5 to 7. FIG. 5 is a schematic diagram
illustrating an example of a first association table in which the
measurement temperature is associated with an initial value of a
distortion compensation coefficient that is in accordance with each
of the measurement temperatures. FIG. 6 is a schematic diagram
illustrating an example of a calculation process of the average
value of the distortion compensation coefficients extracted from an
LUT at the measurement time of the predetermined number of
measurements. Furthermore, in FIG. 6, a solid line 501 indicates
the initial value of each of the distortion compensation
coefficients that are in accordance with a certain measurement
temperature and a broken line 502 indicates the distortion
compensation coefficients stored in the memory 209, i.e., the
distortion compensation coefficients extracted from the LUT 201 at
the measurement time of the predetermined number of measurements.
FIG. 7 is a schematic diagram illustrating an example of a
calculation process of an amount of variation in each of the
distortion compensation coefficients.
[0055] For example, the coefficient variation amount calculating
unit 211 holds the first association table illustrated in FIG. 5
and acquires, by using the first association table, the initial
value of the distortion compensation coefficient that is associated
with the "measurement temperature" measured by the temperature
measuring unit 210. The initial value of the distortion
compensation coefficient is a value that is previously determined
when, for example, the RE device 100 is shipped from a plant or the
like. Furthermore, the coefficient variation amount calculating
unit 211 refers to the memory 209 and performs, as illustrated in
FIG. 6, a moving average process on the distortion compensation
coefficients extracted from the LUT 201 at the measurement time of
the predetermined number of measurements, whereby the coefficient
variation amount calculating unit 211 calculates the average value
of the distortion compensation coefficients. In the example
illustrated in FIG. 6, the average value of the distortion
compensation coefficients extracted from the LUT 201 at the
measurement time of 100 measurements. Then, the coefficient
variation amount calculating unit 211 calculates, as illustrated in
FIG. 7, a difference between the initial value of each of the
distortion compensation coefficients acquired from the first
association table, the initial value being indicated by the solid
line 501, and an average value of the distortion compensation
coefficients, the average value being indicated by a broken line
503 as the amount of variation in the distortion compensation
coefficient with respect to the initial value.
[0056] A description will be given here by referring back to FIG.
3. The FFT processing unit 212 monitors the power value of the BB
signal measured by the electrical power measuring unit 207 and, if
the power value of the BB signal is equal to or greater than the
threshold (for example, the threshold illustrated in FIG. 4),
acquires the frequency spectra of the FB signal at the measurement
time of the predetermined number of measurements. The fast Fourier
transformation is used to acquire the frequency spectra of the FB
signal. Then, the FFT processing unit 212 outputs the frequency
spectra of the FB signal acquired at the measurement time of the
predetermined number of measurements to the memory 213.
[0057] The memory 213 stores the frequency spectra of the FB signal
acquired by the FFT processing unit 212 for each measurement
time.
[0058] The bandwidth variation amount calculating unit 214 averages
the frequency spectra of the FB signal stored in the memory 213,
i.e., the frequency spectra of the FB signal acquired by the FFT
processing unit 212 at the measurement time of the predetermined
number of measurements. Then, the bandwidth variation amount
calculating unit 214 calculates, by using the averaged frequency
spectrum, an amount of variation in the bandwidth of the FB signal
with respect to the initial value. At this point, the bandwidth
variation amount calculating unit 214 may also change the initial
value of the bandwidth in accordance with the "measurement
temperature" received from the temperature measuring unit 210 and
calculate an amount of variation in the bandwidth of the FB signal
with respect to the changed initial value. The amount of variation
in the bandwidth of the FB signal calculated by the bandwidth
variation amount calculating unit 214 is output to the CPU 110.
[0059] In the following, a process performed by the bandwidth
variation amount calculating unit 214 will be described with
reference to FIG. 8. FIG. 8 is a schematic diagram illustrating an
example of a calculation process of an amount of variation in the
bandwidth of an FB signal. Furthermore, in FIG. 8, a waveform 511
indicates the frequency spectrum of the FB signal before the
average and a waveform 512 indicates the frequency spectrum of the
FB signal after the average.
[0060] For example, the bandwidth variation amount calculating unit
214 holds a second association table in which a measurement
temperature is associated with the initial value of the bandwidth
in accordance with each of the measurement temperatures and
acquires, by using the second association table, the initial value
of the bandwidth associated with the "measurement temperature"
measured in the temperature measuring unit 210. The initial value
of the bandwidth is a value that is previously determined when, for
example, the RE device 100 is shipped from a plant or the like.
Then, the bandwidth variation amount calculating unit 214 refers to
the memory 213 and performs the moving average process on the
frequency spectra of the FB signal acquired at the measurement time
of the predetermined number of measurements, whereby the bandwidth
variation amount calculating unit 214 averages the frequency
spectra of the FB signal. In the example illustrated in FIG. 8, the
moving average process is performed on the frequency spectra of the
FB signal acquired at the measurement time of 100 measurements,
whereby the frequency spectra of the FB signal are averaged. Then,
the bandwidth variation amount calculating unit 214 measures, as
illustrated on the right side illustrated in FIG. 8, by using the
averaged frequency spectrum, the bandwidth of the FB signal. Then,
the bandwidth variation amount calculating unit 214 calculates a
difference between the initial value of the bandwidth acquired from
the second association table and the bandwidth of the FB signal
measured from the averaged frequency spectrum as the amount of
variation in the bandwidth of the FB signal with respect to the
initial value.
[0061] In the following, an example of the amplifier deterioration
determination process performed in the RE device 100 will be
described with reference to the flowchart illustrated in FIG. 9
using a specific example. FIG. 9 is a flowchart illustrating an
example of an amplifier deterioration determination process
according to the embodiment.
[0062] When the BB signal sent from the REC device 10 is received
by the RE device 100, the BB signal is subjected to distortion
compensation by the multiplier 101, is subjected to DA conversion
by the DA converter 102, and is up-converted by the modulator 104.
Then, after the signal with the radio frequency obtained from up
conversion is amplified by the PA 105, the signal is sent from the
antenna and is fed back to the mixer 107. The fed back signal is
down-converted by the mixer 107 and becomes the FB signal with the
intermediate frequency and, then, the FB signal is output from the
mixer 107 to the AD converter 108.
[0063] Then, the FB signal that has been subjected to AD conversion
by the AD converter 108 is input to the FPGA 109. In contrast, the
BB signal is also input to the FPGA 109 and the BB signal is made
to delay by the delay device 202, whereby the phase of the BB
signal matches with that of the FB signal. The BB signal and the FB
signal are compared by the comparator 205 and the distortion
compensation coefficients stored in the LUT 201 are updated by the
computing unit 206 such that the difference between the BB signal
and the FB signal approaches zero.
[0064] The coefficient extracting unit 208 monitors the power value
of the BB signal measured by the electrical power measuring unit
207 and extracts, if the power value of the BB signal is equal to
or greater than the threshold (Yes at Step S101), the distortion
compensation coefficient that is in accordance with the power value
of the BB signal from the LUT 201 (Step S102). The distortion
compensation coefficient extracted from the LUT 201 by the
coefficient extracting unit 208 is stored in the memory 209 (Step
S103).
[0065] The coefficient variation amount calculating unit 211 refers
to the memory 209 and determines whether the number of distortion
compensation coefficients stored in the memory 209 reaches a
predetermined number (Step S104). As the predetermined number, for
example, 100 is set. If the number of distortion compensation
coefficients stored in the memory 209 does not reach the
predetermined number, i.e., if extraction of the distortion
compensation coefficients from the LUT 201 at the measurement time
of the predetermined number of measurements has not been completed
(No at Step S104), the coefficient variation amount calculating
unit 211 returns the process to Step S102.
[0066] In contrast, if the number of distortion compensation
coefficients stored in the memory 209 reaches the predetermined
number, i.e., if extraction of the distortion compensation
coefficients from the LUT 201 at the measurement time of the
predetermined number of measurements has been completed (Yes at
Step S104), the coefficient variation amount calculating unit 211
proceeds the process to Step S105.
[0067] The coefficient variation amount calculating unit 211
calculates the distortion compensation coefficients stored in the
memory 209, i.e., the average value of the distortion compensation
coefficients extracted from the LUT 201 at the measurement time of
the predetermined number of measurements (Step S105).
[0068] The coefficient variation amount calculating unit 211
acquires the measurement temperature that was acquired by the
temperature measuring unit 210 (Step S106). Then, the coefficient
variation amount calculating unit 211 acquires, by using the first
association table, the initial value of the distortion compensation
coefficient that is in accordance with the measurement temperature
(Step S107).
[0069] The coefficient variation amount calculating unit 211
calculates, as the amount of variation in the distortion
compensation coefficient with respect to the initial value, the
difference between the initial value of the distortion compensation
coefficient acquired from the first association table and the
average value of the distortion compensation coefficients
calculated at Step S105 (Step S108). The amount of variation in the
distortion compensation coefficient calculated by the coefficient
variation amount calculating unit 211 is output to the CPU 110.
[0070] If the amount of variation in the distortion compensation
coefficient is equal to or greater than the threshold (Yes at Step
S109), the CPU 110 determines that the PA 105 is degraded (Step
S110) and outputs an alarm indicating the subject status (Step
S111).
[0071] In contrast, if the amount of variation in the distortion
compensation coefficient is less than the threshold (No at Step
S109), the CPU 110 determines that the PA 105 is degraded (Step
S112). At this time, the information related to the determination
result indicating whether the PA 105 is degraded may also be
created by the CPU 110 and the created information may also be
reported to the monitoring device 30 via the REC device 10. Then,
the CPU 110 derives a prediction line of the amount of variation on
the basis of the amount of variation in the distortion compensation
coefficient and notifies the monitoring device 30 of the
information on the remaining time before the amount of variation in
the distortion compensation coefficient reaches the threshold (Step
S113). Namely, the CPU 110 functions as a predicting unit that
predicts, by using the prediction line, the time at which the
amount of variation reaches the predetermined threshold.
[0072] FIG. 10 is a schematic diagram illustrating a specific
example of a prediction line of an amount of variation in the
distortion compensation coefficients. Specifically, for example, as
illustrated in FIG. 10, by using, for example, the least squares
method by the CPU 110, a prediction line 602 of the amount of
variation in the distortion compensation coefficients is derived
from plots 601 that indicate the amount of variation in the
distortion compensation coefficient for each measurement day. Then,
the number of remaining days before the amount of variation in the
distortion compensation coefficient for each measurement day
reaches a predetermined threshold is acquired from the prediction
line 602 by the CPU 110. In the example illustrated in FIG. 10, it
is found that the prediction line 602 is derived by the plots 601
for 600 days and it is found that the number of remaining days
before the amount of variation in the distortion compensation
coefficient for each measurement day reaches the predetermined
threshold is about 100 days. Furthermore, the CPU 110 may also
output, in stages, an alarm in accordance with the subject amount
of variation by using the derived prediction line before the amount
of variation of the distortion compensation coefficient reaches the
predetermined threshold.
[0073] In the following, another example of the amplifier
deterioration determination process performed in the RE device 100
will be described with reference to the flowchart illustrated in
FIG. 11 using a specific example. FIG. 11 is a flowchart
illustrating another example of an amplifier deterioration
determination process according to the embodiment. Furthermore, the
process illustrated in FIG. 11 is performed in parallel with the
process illustrated in FIG. 9.
[0074] The FFT processing unit 212 monitors the power value of the
BB signal measured by the electrical power measuring unit 207 and,
if the power value of the BB signal is equal to or greater than the
threshold (Yes at Step S121), the FFT processing unit 212 acquires
the frequency spectrum of the FB signal (Step S122). The frequency
spectrum of the FB signal acquired by the FFT processing unit 212
is stored in the memory 213 (Step S123).
[0075] The bandwidth variation amount calculating unit 214 refers
to the memory 213 and determines whether the number of frequency
spectra stored in the memory 213 reaches a predetermined number
(Step S124). As the predetermined number, for example, 100 is set.
If the number of frequency spectra stored in the memory 213 does
not reach the predetermined number, i.e., acquisition of the
frequency spectra of the FB signal at the measurement time of the
predetermined number of measurements has not been completed (No at
Step S124), the bandwidth variation amount calculating unit 214
returns the process to Step S122.
[0076] In contrast, if the number of frequency spectra stored in
the memory 213 reaches the predetermined number, i.e., acquisition
of the frequency spectra of the FB signal at the measurement time
of the predetermined number of measurements has been completed (Yes
at Step S124), the bandwidth variation amount calculating unit 214
proceeds the process to Step S125.
[0077] The bandwidth variation amount calculating unit 214 averages
the frequency spectra of the FB signal stored in the memory 213,
i.e., averages the frequency spectra of the FB signal acquired by
the FFT processing unit 212 at the measurement time of the
predetermined number of measurements (Step S125). Then, the
bandwidth variation amount calculating unit 214 measures the
bandwidth of the FB signal by using the averaged frequency spectrum
(Step S126).
[0078] The bandwidth variation amount calculating unit 214 acquires
the measurement temperature acquired by the temperature measuring
unit 210 (Step S127). Then, the bandwidth variation amount
calculating unit 214 acquires, by using the second association
table, the initial value of the bandwidth that is in accordance
with the measurement temperature (Step S128).
[0079] The bandwidth variation amount calculating unit 214
calculates the difference between the initial value of the
bandwidth acquired from the second association table and the
bandwidth of the FB signal measured at Step S126 as an amount of
variation in the bandwidth of the FB signal with respect to the
initial value (Step S129). The amount of variation in the bandwidth
of the FB signal calculated by the bandwidth variation amount
calculating unit 214 is output to the CPU 110.
[0080] If the amount of variation in the bandwidth of the FB signal
is equal to or greater than the threshold (Yes at Step S130), the
CPU 110 determines that the PA 105 is degraded (Step S131) and
outputs an alarm indicating the subject state (Step S132).
[0081] In contrast, if the amount of variation in the bandwidth of
the FB signal is less than the threshold (No at Step S130), the CPU
110 determines that the PA 105 is not degraded (Step S133). At this
time, the information indicating whether the determined PA 105 is
degraded may also be created by the CPU 110 and the created
information may also be reported to the monitoring device 30 via
the REC device 10. Then, the CPU 110 derives a prediction line of
the amount of variation on the basis of the amount of variation in
the bandwidth of the FB signal and notifies the monitoring device
30 of the information about the remaining time before the amount of
variation in the bandwidth of the FB signal reaches the threshold
(Step S134). Namely, the CPU 110 functions as a predicting unit
that predicts, by using the prediction line, the time at which the
amount of variation reaches the predetermined threshold.
[0082] FIG. 12 is a schematic diagram illustrating a specific
example of a prediction line of an amount of variation in the
bandwidth of an FB signal. Specifically, for example, as
illustrated in FIG. 12, by using, for example, the least squares
method by the CPU 110, a prediction line 612 of the amount of
variation in the bandwidth of the FB signal is derived from plots
611 that indicate the amount of variation in the bandwidth of the
FB signal for each measurement day. Then, the number of remaining
days before the amount of variation in the bandwidth of the FB
signal for each measurement day reaches a predetermined threshold
is acquired from the prediction line 612 by the CPU 110. In the
example illustrated in FIG. 12, it is found that the prediction
line 612 is derived by the plots 611 for 600 days and it is found
that the number of remaining days before the amount of variation in
the bandwidth of the FB signal for each measurement day reaches the
predetermined threshold is about 100 days. Furthermore, the CPU 110
may also output, in stages, an alarm in accordance with the subject
amount of variation by using the derived prediction line before the
amount of variation in the bandwidth of the FB signal reaches the
predetermined threshold.
[0083] As described above, according to the embodiment, when the
power value of the BB signal is equal to or greater than the
threshold, the distortion compensation coefficients that are in
accordance with the power value of the BB signal are extracted from
the LUT 201 at the predetermined number of measurement periods.
Then, according to the embodiment, an amount of variation in the
distortion compensation coefficient is calculated by using the
average value of the extracted distortion compensation coefficients
and it is determined, on the basis of the calculated amount of
variation in the distortion compensation coefficient whether the PA
105 is degraded. Consequently, it is possible to extract the
distortion compensation coefficient that is in accordance with the
power value of the BB signal from the LUT 201 in the state in which
the power value of the BB signal that is the signal before
amplification in the PA 105 is present in the nonlinear operation
area in the PA 105. Consequently, it is possible to appropriately
determine degradation of the PA 105 (in particular, the degradation
of the gain of the PA 105) by using the distortion compensation
coefficient that is in accordance with the power value that
satisfies the prescription of law.
[0084] Furthermore, according to the embodiment, when the power
value of the BB signal is equal to or greater than the threshold,
the frequency spectra of the FB signal are acquired at the
predetermined number of measurements. Then, according to the
embodiment, an amount of variation in the bandwidth of the FB
signal is calculated by using the averaged frequency spectrum and
it is determined, on the basis of the calculated amount of
variation in the bandwidth of the FB signal, whether the PA 105 is
degraded. Consequently, it is possible to acquire the frequency
spectrum of the FB signal in the state in which the power value of
the BB signal that is the signal before amplification in the PA 105
is present in the nonlinear operation area in the PA 105.
Consequently, by using the frequency spectrum of the FB signal that
is in accordance with the power value that satisfies the
prescription of law, degradation of the PA 105 (in particular, the
degradation of the occupied bandwidth of the signal output from the
PA 105) can be appropriately determined.
[0085] Furthermore, in the embodiment described above, the initial
value of the distortion compensation coefficient is changed in
accordance with the temperature of the RE device 100; however, the
initial value of the distortion compensation coefficient may also
be changed in accordance with the number of carriers that are used
for radio transmission. If the number of carriers that are used for
radio transmission is changed, it is known that a characteristic
curve of a distortion compensation coefficient varies in accordance
with, for example, as illustrated in FIG. 13, the number of
carriers. FIG. 13 is a schematic diagram illustrating variation of
the distortion compensation coefficients in accordance with the
number of carriers. If the number of carriers is changed in this
way, by using the CPU 110 or the monitoring device 30, the initial
value of the distortion compensation coefficient may also be
changed in accordance with the changed number of carriers.
Furthermore, it is known that, if the number of carriers that are
used for radio transmission is changed, the bandwidth of the FB
signal is also changed in accordance with the number of carriers.
Thus, if the number of carriers is changed, by using the CPU 110 or
the monitoring device 30, the initial value of the bandwidth may
also be changed in accordance with the number of carriers that has
been changed.
[0086] According to an aspect of an embodiment of the wireless
device disclosed in the present invention, an advantage is provided
in that degradation of an amplifier can appropriately be
determined.
[0087] All examples and conditional language recited herein are
intended for pedagogical purposes of aiding the reader in
understanding the invention and the concepts contributed by the
inventor to further the art, and are not to be construed as
limitations to such specifically recited examples and conditions,
nor does the organization of such examples in the specification
relate to a showing of the superiority and inferiority of the
invention. Although the embodiment of the present invention has
been described in detail, it should be understood that the various
changes, substitutions, and alterations could be made hereto
without departing from the spirit and scope of the invention.
* * * * *