Data processing: measuring – calibrating – or testing – Calibration or correction system – Signal frequency or phase correction
Reexamination Certificate
2001-01-29
2003-07-15
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Calibration or correction system
Signal frequency or phase correction
C702S074000, C356S450000, C375S142000
Reexamination Certificate
active
06594605
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a correlation function measuring method and apparatus, more specifically to a correlation function measuring method and apparatus for measuring a correlation vector of a plurality of input signals.
Recently, a technique for visualizing a wave source image by electric wave holography has been practiced and is used, e.g., in monitoring electric waves from base stations for portable telephones. Electric wave holograms of electric waves from base stations of a portable telephone network are analyzed to thereby visually monitor the electric waves from the base stations so as to obtain materials useful to judge whether or not to install a new base station.
A wave source image visualizing method and apparatus has been proposed by the applicant of the present application in, e.g., the specification of Japanese Patent Application No. 289848/1995.
The wave source image visualizing method and apparatus proposed by the applicant of the present application will be explained with reference to FIG.
8
.
FIG. 8
is a block diagram of the proposed wave source image visualizing apparatus.
As shown in
FIG. 8
, a monitored signal (a) received by a stationary antenna (not shown) is subjected to prescribed signal processing by the pre-conversion unit
218
a,
a data memory
220
a
and Fourier-transform unit
222
a
to be inputted to a correlation vector computing unit
230
while a monitored signal (b) received by a scanning antenna (not shown) is subjected to prescribed signal processing by a pre-conversion unit
218
b,
a data memory
220
b
and a Fourier-transform unit
222
b
to be inputted to the correlation vector computing unit
230
. The pre-conversion units
218
a,
218
b
restrict the monitored signal (a) and the monitored signal (b), based on a center frequency f
0
and a band width bw to convert them to IF signals and output the IF signals. The data memories
220
a,
220
b
perform an analog-to-digital (A/D) conversion process on the IF signals and store the A/D converted signals therein. The Fourier-transform units
222
a,
222
b
perform Fourier-transformation to output a spectrum S
A
(f) and a spectrum S
B
(f).
In the correlation vector computing unit
230
, based on the following formula,
∫
f
0
-
bw
2
f
0
+
bw
2
S
A
*
(
f
)
·
S
B
(
f
)
&LeftBracketingBar;
S
A
(
f
)
&RightBracketingBar;
ⅆ
f
(
1
)
a correlation vector is given, where * represents a complex conjugate.
In such a wave source image visualizing apparatus, when measuring conditions, such as band width restriction, frequency conversion, etc., are changed, frequency characteristics of the pre-conversion units
218
a,
218
b
change. Furthermore, the frequency characteristic change varies between the pre-conversion unit
218
a
and the pre-conversion unit
218
b.
Accordingly, it is necessary to prepare in advance correction data, and a correlation vector is corrected by using the correction data. The wave source image visualizing apparatus shown in
FIG. 8
gives correction data &rgr;(c) in the following way.
That is, when correction data &rgr;(c) is given, switches
216
a,
216
b,
224
are set on a correction side (c), correction signals are outputted by a signal generator
212
, the correction signals are distributed to two paths by the power splitter
214
, the correction signals are inputted to the correction sides (c) of the switches
216
a,
216
b,
and a correlation vector is given by the correlation vector computing unit
230
. A value of the given correlation vector is stored in a correction data memory
228
as the correction data &rgr;(c).
For electric wave monitor, the switches
216
a,
216
b,
224
are set on a measuring side (m), and a correlation vector is given by the correlation vector computing unit
230
. The given correlation vector is corrected in a correction unit
229
by using the correction data &rgr;(c) to be outputted to a wave source image reproduction processing unit (not shown).
The wave source image reproduction processing unit performs prescribed image processing, and a processed image is presented on a display of a display unit (not shown).
However, in the proposed wave source image visualizing apparatus, a correlation vector of an average of band frequencies given when a correction signal is inputted is used as correction data &rgr;(c). Accordingly, in a case that characteristics of the pre-conversion units
218
a,
218
b
change by frequencies, correction accuracy varies depending on frequencies.
Characteristics of the pre-conversion units
218
a,
218
b
are varied by changes of measuring conditions, surrounding temperature changes, changes over time, etc. The proposed wave source image visualizing apparatus has correction accuracy lowered by these factors.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a correlation function measuring method and apparatus which can correct a correlation vector with high accuracy.
The above-described object is achieved by a correlation function measuring method in which a first monitored signal is processed by a first signal processing means to give a first spectrum, a second monitored signal is processed by a second signal processing means to give a second spectrum, and a correlation function between the first spectrum and the second spectrum is measured, the method comprising the steps of: inputting, before measuring the correlation function, correction signals to the first signal processing means and the second signal processing means, and giving correction values corresponding to frequencies of the correction signals, based on a spectrum given by the first signal processing means, and a spectrum given by the second signal processing means; and in measuring the correlation function, giving a correlation function between the first spectrum and the second spectrum by using the correction values corresponding to the frequencies. Correction data for respective frequencies are given before a correlation function is measured, and the correlation function is given by using the correction data corresponding to the frequencies, whereby the correlation function can be given with high accuracy. Thus, the correlation function measuring method can measure a correlation function with high accuracy.
In the above-described correlation function measuring method it is preferable that in giving the correction values, the frequencies of the correction signals are scanned to give the correction values corresponding to the respective frequencies.
In the above-described correlation function measuring method it is preferable that a recurrence formula is given based on the correction values; and in renewing the correction values, correction values necessary to determine at least the recurrence formula are again given to renew the recurrence formula, and based on the renewed recurrence formula, the correction values are renewed.
In the above-described correlation function measuring method it is preferable that in giving the correction values, modulated waves are inputted to the first signal processing means and the second signal processing means to give correction values corresponding to respective frequencies.
In the above-described correlation function measuring method it is preferable that in giving the correction values, first correction signals are inputted to the first signal processing means and the second signal processing means, scanning frequencies, to give magnitude correction data corresponding to the frequencies, based on a spectrum given by the first signal processing means and a spectrum given by the second signal processing means, and second correction signals are inputted to the first signal processing means and the second signal processing means to give phase correction data corresponding to the respective frequencies, based on a spectrum given by the first signal processing means and a spectrum given by the second signal processing means, and the correction values corresponding to the respective frequencies are given based
Advantest Corp.
Hoff Marc S.
Muramatsu & Associates
West Jeffrey
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