Data processing: measuring – calibrating – or testing – Testing system – Of circuit
Reexamination Certificate
2000-07-20
2002-12-17
Assouad, Patrick (Department: 2857)
Data processing: measuring, calibrating, or testing
Testing system
Of circuit
C324S601000, C702S107000
Reexamination Certificate
active
06496785
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a network analyzer for calculating and measuring a circuit parameter of a device under test.
2. Description of the Related Art
There have been two practiced methods for measuring various circuit parameters of a device under test such as, for example, an S parameter of an arbitrary normalized impedance, an S parameter in the case where a matching circuit is added, and the circuit impedance.
A first method is to connect a fixture to a device under test so that a desired circuit parameter is directly measured. In
FIG. 10
is shown a system configuration of a device under test connected to a fixture. In the first method shown in
FIG. 10
, the fixture
120
is connected to a device under test
100
and the device under test
100
, together with the fixture
120
, is measured by the network analyzer
200
.
In this case, the circuit parameters of the device under test
100
vary with the fixture
120
. Therefore, in order to obtain the circuit parameters under given conditions, the measurement is carried out by fabricating a fixture
120
satisfying the given conditions and connecting it to the device under test
100
. When, for example, it is desired to obtain circuit parameters for ten kinds of conditions, ten fixtures
120
may be fabricated and then ten measurement, may be performed by connecting each fixture to the device under test
100
.
A second method is carried out as follows: raw data of the device under test (for example, an S parameter) is first measured. Then, the measured raw data is substituted into a relational expression between a desired circuit parameter and the raw data to thereby obtain the desired circuit parameter.
The second method will be described below by taking a measurement of the impedance of a device under test as an example. First, the impedance Z is expressed as the numerical expression in
FIG. 11
, where Ed is an error mainly due to the directivity of the bridge, Er is an error mainly due to the frequency tracking, and Es is an error mainly due to the source matching.
When the numerical expression of
FIG. 11
is represented by a signal flow graph,
FIG. 12
is obtained. S
11
denotes the raw data to be measured. By substituting this into the numerical expression of
FIG. 11
, the impedance Z can be obtained.
The second method can be effectively used when it is difficult or impossible, in principle, to fabricate a fixture. In the case shown in
FIG. 12
, for example, the impedance may be measured if the portion in the center of the right-hand side can be fabricated as a fixture. However, it is impossible to fabricate such a fixture in principle. The second method is therefore used for obtaining the impedance.
SUMMARY OF THE INVENTION
However the first method has the following defects. First of all, it is troublesome to fabricate a variety of fixtures and it is also troublesome to repeat measurements many times. It is also difficult to fabricate fixtures having ideal characteristics. Further, when a plurality of fixtures for the same purpose are fabricated, it is difficult to fabricate them with uniform characteristics. Furthermore, depending on circuit parameters to be measured, there are cases where fabrication of the fixtures is impossible in principle.
On the other hand, the second method, it is relatively easy to solve the above mentioned problems related to fabrication of fixtures. However, a long time is taken for calculation and this prolongs the totally required measuring time.
Accordingly, an object of the present invention is to provide a network analyzer whereby various circuit parameters of a device under test can be obtained simply.
According to the present invention, a network analyzer for calculating a circuit parameter of a device under test may include: a raw data measurement means for measuring raw data of the device under test; a measuring-system error-factor measurement means for obtaining measuring system error factors occurring in the measurement of the device under test; a parameter conversion factor calculation means for obtaining factors of parameter conversion indicative of the relationship between the circuit parameter and measuring-system error-factor-free data obtained by eliminating the measuring-system error factors from the raw data; a true-value raw data calculation means for obtaining the measuring-system error-factor-free data from the raw data and the measuring-system error factors; and a device-under-test calculation means for obtaining the circuit parameter from the measuring-system error-factor-free data and the parameter conversion factor.
The term “raw data” as used herein means the data directly measured by a network analyzer. An example of the raw data is an S parameter. Factors of errors occurring in the measurement system include an error attributable to the directivity of a bridge, an error attributable to the frequency tracking, and an error attributable to the source matching. An example of the circuit parameter is an impedance. An example of factors of parameter conversion is the relationship between an S parameter and the impedance.
According to the present invention, a circuit parameter can be obtained from raw data, factors of errors in the measurement system, and factors of parameter conversion. Therefore, when a circuit parameter is connected to a device under test, the circuit parameter can be calculated without fabricating any fixtures and repeating many times of measurement with the fixtures changed each time. Hence, a circuit parameter can be calculated simply.
The present invention may include a network analyzer as noted above, wherein the measurement means treats the raw data as the measuring-system error-factor-free data.
In the case where the measuring-system error-factor can be neglected, the raw data of the device-under-test may be treated as the measuring-system error-factor-free data.
According to the present invention, a network analyzer for calculating a circuit parameter of a device under test may include: a raw data measurement means for measuring raw data of the device under test; a measuring-system error-factor measurement means for obtaining measuring-system error factors occurring in the measurement of the device under test; a parameter conversion factor calculation means for obtaining factors of parameter conversion indicative of the relationship between the circuit parameter and measuring-system error-factor-free data obtained by eliminating the measuring-system error factors from the raw data; an extended error-factor calculation means for obtaining extended error factors by combining the measuring-system error factors and the parameter conversion factor; and a device-under-test calculation means for obtaining the circuit parameter from the raw data and the extended error factors.
According to the present invention, a circuit parameter can be obtained from raw data, factors of errors in the measurement system, and factors of parameter conversion. Therefore, when a fixture is connected to a device under test, the circuit parameter can be calculated without fabricating any fixtures and repeating measurements many times with the fixtures changed each time. Hence, a circuit parameter can be calculated simply.
Furthermore, the error factor calculation means obtains the extended error factors in advance by combining the error factors occurring in the measurement system and the factors of parameter conversion. Therefore, calculation speed can be improved.
According to the present invention, a network analyzer as noted above, may further include a parameter conversion factor record means for recording the parameter conversion factor.
The present invention may include a network analyzer as noted above, wherein the circuit parameter is an impedance.
The present invention may include a network analyzer as noted above, wherein the circuit parameter is an S parameter as an arbitrary normalized impedance.
The present invention may include a network analyzer as noted above, wherein the circuit param
Arakawa Norio
Nakayama Yoshikazu
Advantest Corporation
Assouad Patrick
Lowe Hauptman Gilman & Bener, LLP
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