Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Electrical signal parameter measurement system
Reexamination Certificate
2002-07-08
2004-10-12
Wachsman, Hal (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Electrical signal parameter measurement system
C702S076000, C702S057000, C324S095000
Reexamination Certificate
active
06804617
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a field distribution measuring method and apparatus for measuring a distribution of an electric field or a magnetic field by a probe sweeping, more specifically, to a field distribution measuring method and apparatus which can eliminate measured noises generated due to offsets between probe sweeping positions and measuring timings.
BACKGROUND ART
Small antenna directivity evaluation apparatuses and electromagnetic wave monitoring visualizing apparatuses must measure two-dimensional distributions of electric fields or magnetic fields. These apparatuses have conventionally used a field measurement method in which a probe sweeps two-dimensionally to measure two-dimensional distributions of electric fields or magnetic fields.
The conventional field distribution measuring method and apparatus will be explained with reference to FIG.
6
.
A field distribution measurement screen
100
which defines an area in which electric fields or magnetic fields are to be measured includes a probe
102
for detecting electric fields or magnetic fields. The probe
102
is connected to a probe sweep control unit
104
and can sweep in the x-axial direction and the y-axial direction. The probe
102
is connected to a measuring unit
106
which measures electric fields or magnetic fields, based on signals from the probe
102
. The probe sweep control unit
104
outputs a measurement trigger signal corresponding to a position of the probe
102
and supplies the measurement trigger signal to the measuring unit
106
. Data F of the electric fields or magnetic fields measured by the measuring unit
106
are recorded in a buffer memory
108
together with position information supplied by the probe sweep control unit
104
. The buffer memory
108
is connected to a computing/display unit
110
which processes and displays in two-dimensional plane measured data stored in the buffer memory
108
.
In the field distribution measuring apparatus shown in
FIG. 6
, a field distribution is measured by the probe
102
sweeping the field distribution measurement screen
100
while electric fields or magnetic fields being measured on the field distribution measurement screen
100
, and measured electric fields or magnetic fields are processed together with position information of the probe
102
.
The probe
102
continuously sweeps the field distribution measurement screen
100
without pausing at each sampling point (measuring point) so that the probe
102
can sweep without loss for maximum measurement throughput. As exemplified in
FIG. 6
, the probe
102
is moved in the positive direction along the x-axis, then moved by a prescribed value in the positive direction along the y-axis, next moved in the negative direction along the x-axis, then moved by a prescribed value in the positive direction along the y-axis, and then moved in the positive direction along the x-axis. The probe
102
repeats these motions so as to sweep substantially all the surface of the field distribution measurement screen
100
(hereinafter call such sweep “zigzag sweep”).
The probe sweep control unit
104
outputs measurement trigger signals corresponding to positions of the probe
102
while the probe
102
is sweeping the field distribution measurement screen
100
. As exemplified in
FIG. 7
, a plurality of x coordinates are set in advance, spaced equidistantly from each other along the x-axis, and when an x coordinate of a position of the probe
102
comes to each of the set x-coordinates, the probe sweep control unit
104
outputs a measurement trigger signal. The measurement trigger signals are supplied to the measuring unit
106
.
The measuring unit
106
judges a signal detected by the probe
102
when the measuring unit
106
received the measurement trigger signal to be information of electric fields or magnetic fields, and measures the electric fields or magnetic fields, based on the signal outputted by the probe
102
.
Data of electric fields or magnetic fields thus measured are stored by the buffer memory
108
together with position information (coordinates (x,y)) of the probe outputted by the prove sweep control unit.
Next, the data stored by the buffer memory
108
are developed on a two-dimensional plane by the computing/display unit
110
, and a two-dimensional field distribution of electric fields or magnetic fields can be displayed.
However, there is a delay time from detection of a measurement trigger signal to output of a measured value. Accordingly, in the conventional field distribution measuring method described above, in which the probe continuously sweeps without pausing at each sampling position for higher measuring throughputs, an x coordinate of the probe
102
at the time of outputting a measurement trigger signal is displaced from an x coordinate of the probe
102
at the time of the actual measurement.
Furthermore, as shown in
FIG. 7
, when the probe
102
sweeps zigzag, the shift of coordinates on an odd number-th line on the y-axis and that of coordinates on an even number-th line on the y-axis take place in directions opposite to each other. That is, on an odd number-th line on the y-axis, where the probe is moved along the x-axis in the positive direction, sampling points shift in the positive direction (circled in FIG.
7
). Oppositely, on an even number-th line on the y-axis, where the probe is moved along the x-axis in the negative direction, sampling points shift in the negative direction (crossed in FIG.
7
). A deviation amount of the sampling points between the odd number-th line and the even number-th line is 2xvxtd
d
[m] by which x axial sampling positions on both lines deviates from each other for the same trigger point when a sweeping velocity of the probe is v [m/s], and a delay time is t
d
[see].
Accordingly, by developing a field distribution on a two-dimensional plane, based on the position information outputted by the probe sweep control unit
104
, correct two-dimensional images of electric fields or magnetic fields cannot be obtained.
DISCLOSURE OF INVENTION
An object of the present invention is to provide a field distribution measuring method and apparatus for measuring a distribution of electric fields or magnetic fields by continuously sweeping a probe, wherein measuring noises generated due to offsets between sweeping positions of the probe and measuring timings can be removed.
The above-described object can be achieved by a field distribution measuring method for measuring an electric field or a magnetic field by a probe measuring at a plurality of sampling points while continuously sweeping, wherein a shift amount of the sampling points is computed, based on a spurious spectrum generated by a displacement between a position of the probe and a measuring timing, and a distribution of the electric field or the magnetic field is measured in consideration of the shift amount.
In the above-described field distribution measuring method, it is possible that the method comprises the steps of: storing a plurality of measured data obtained by the probe sweeping in a first direction together with position information of the probe as reference data; storing a plurality of measured data obtained by the probe sweeping in a second direction opposite to the first direction together with position information of the probe as adjustment data; interpolating the adjustment data to compute interpolated data with data between the sampling points interpolated; computing spatial frequency power spectra for the reference data and the interpolated data; and computing the shift amount of the sampling points, based on the spatial frequency power spectra.
In the above-described field distribution measuring method, it is possible that the shift amount of the sampling points is computed based on an accumulated value of the spatial frequency power spectra.
In the above-described field distribution measuring method, it is possible that the shift amount of the sampling points is judged, based on a point where the accumulated value o
Advantest Corporation
Muramatsu & Associates
Wachsman Hal
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