Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Analysis of complex waves
Reexamination Certificate
1999-05-19
2003-01-21
Le, N. (Department: 2858)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Analysis of complex waves
C324S076130
Reexamination Certificate
active
06509728
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a spectrum analyzer, or more in particular, to a spectrum analyzer having the function of effectively displaying the amplitude probability distribution (hereinafter sometimes referred to as the APD) of the signal field strength of a disturbance or the like, that is, the time ratio at which the level of the envelope of the signal such as a disturbance exceeds a preset threshold level, as a measure for statistically evaluating an electromagnetic environment.
In recent years, the digital communication and the digital broadcasting using such means as the portable telephone and the personal handy phone (PHS) operating in a frequency band higher than 1 GHz have extended more than ever before.
In order to protect these radio communications from disturbance, a method of measuring the disturbance and the limits thereof are under study at the International Special Committee on Radio Disturbance (CISPR).
At present, the limit of the frequency band of not higher than 1 GHz is specified primarily by the quasi peak value (QP value) of the disturbance.
This is by reason of the fact that the QP value of the disturbance is correlated with the degree of the interference in the analog communication.
It is, however, difficult to consider that the QP value of the disturbance or the peak value now being studied by CISPR, etc. as a limit in the frequency band not lower than 1 GHz is correlated with the degree of interference in the digital communication or the digital broadcasting.
For the digital communication and the digital broadcasting expected to be used more and more in the frequency band not lower than 1 GHz to be protected from the disturbance, it is desirable to determine the limit of the frequency band not lower than 1 GHz as an index correlated with the degree of interference in the digital system.
On the other hand, the communication quality of the digital communication line is expressed by a bit error rate (BER). It has been reported that the deterioration of the BER of the digital line caused by the disturbance can be estimated from the APD.
Therefore, the APD of the disturbance strength, if it can be measured accurately in simplistic fashion, is considered to provide the optimal index for evaluating the interference in the digital communication.
The apparatus for measuring the APD of the electrical signal has a long history and has hitherto been used primarily for measuring the atmospherics.
With the progress of the technologies, the APD measuring circuit has come to be configured of semiconductors and the operating speed thereof has increased. The conventional APD measuring circuit
121
, however, requires as many comparators and counters as the number of the levels for determining the amplitude resolution.
For improving the amplitude resolution, therefore, it is necessary to add as many comparators and counters as the number of levels. Thus, the APD measuring apparatus of high resolution is expensive and is not suitably used widely to measure EMI.
A spectrum analyzer is also known conventionally as a disturbance field strength measuring apparatus for statistically evaluating an electromagnetic environment.
FIG. 44
is a block diagram showing a general configuration of a spectrum analyzer of this type constituting a disturbance field strength measuring apparatus for statistically evaluating the electromagnetic environment.
Specifically, as shown in
FIG. 44
, the spectrum analyzer comprises a front end
101
, a bandpass filter (BPF)
102
, a log video amplifier (LVA)
103
, a peak detection circuit
104
, a bottom detection circuit
105
, an arithmetic unit
106
and a display unit
107
.
The front end
101
is a radio wave receiving circuit including a frequency converter having a local oscillator and a mixer for producing an intermediate frequency signal (IF).
As a result, the radio disturbance or the like received through an antenna (not shown) is output from the front end
101
as an IF signal component, and then supplied to the peak detection circuit
104
and the bottom detection circuit
105
through the BPF
102
and the LVA
103
.
The peak detection circuit
104
and the bottom detection circuit
105
detect the peak value and the bottom value of the envelope component of the IF signal based on the output of the LVA
103
.
Specifically, let P(t) be the output signal of the LVA
103
. Then, during the measurement time (T
i
≦t<t
i
+T), the peak value P
p
(t
i
) and the bottom value P
b
(t
i
) are supplied to the arithmetic unit
106
in the form of
P
p
(
t
i
)=max
P
(
t
)
P
b
(
t
i
)=min
P
(
t
) (1)
In the arithmetic unit
106
, the peak value P
p
(t
i
) and the bottom value P
b
(t
i
) for the envelope component of the disturbance or the like supplied as described above and the front end state number or a trigger signal from the front end
101
are arithmetically processed in a predetermined manner for display on the display unit
107
.
FIG. 45
shows an example display on the display unit
107
of the spectrum analyzer described above.
Specifically, as shown in
FIG. 45
, the display unit
107
displays the peak value P
p
(t
i
) and the bottom value P
b
(t
i
) in the envelope component of the disturbance or the like from the arithmetic unit
106
on the frequency axis by changing the value i sequentially in the order of 0, 1, 2, . . . , N
w
−1 (N
w
: resolution in frequency domain).
In this case, f
c
on the frequency axis designates the center frequency, f
1
the start frequency and f
2
the stop frequency in the measurement range (span).
As a result, the peak value P
p
(t
i
) and the bottom value P
b
(t
i
) of the radio disturbance expressed as
f
RF
(
i
)=
f
1
+{(
f
2
−f
1
)
i/N
w
.} (2)
received during the measurement time (t
i
≦t<t
i
+T) are read from
FIG. 45
in the form analyzed on the frequency axis.
The area of P indicated by P
p
(t
i
)>P>P
b
is shown by hatching so that the amount between the peak value P
p
(t
i
) and the bottom value P
b
(t
i
) is easily identified.
In the disturbance measuring apparatus using the spectrum analyzer described above, however, the APD is not displayed based on the output signal P(t) of the LVA
103
during the measuring time (t
i
≦t<t
i
+T) constituting an important factor for statistically evaluating the electromagnetic environment, and therefore nothing can be understood of the APD.
Displaying the APD by the contour display method is another alternative conceivable. This method poses the problem, however, that as explained in detail later in comparison with the area identification display method according to this invention, the distribution with a correct threshold value contour cannot be easily identified in the case where contours of different threshold values are superposed one on the other.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a spectrum analyzer having the function of effectively displaying the APD by solving the problem of the prior art described above, by employing the area identification display method using a band group having a plurality of ranges such as different color bands, for example.
Another object of the present invention is to solve the problem of the prior art described above and to provide an APD display method with a spectrum analyzer effectively capable of APD by the area identification display method using a band group having a plurality of ranges such as different color bands.
In order to achieve the above-mentioned objects, according to an embodiment of the invention, there is provided a spectrum analyzer having the APD display function, comprising:
signal receiving and processing means for receiving an input signal in accordance with desired frequency sweep information;
sampling means for sampling an output signal output from the signal receiving and processing means, based on a plurality of threshold values and outputting a plurality of output codes corresponding to sample value of t
Hosoya Haruhiko
Shinozuka Takashi
Uchino Masaharu
Anritsu Corporation
Frishauf Holtz Goodman & Chick P.C.
Le N.
Nguyen Vincent Q.
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