Data processing: measuring – calibrating – or testing – Testing system – Of circuit
Reexamination Certificate
2000-02-01
2002-07-16
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Testing system
Of circuit
C702S085000, C702S107000, C324S600000, C324S601000, C324S637000, C324S638000
Reexamination Certificate
active
06421624
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a multi-port device apparatus and method for analyzing the characteristics of the multi-port device having three or more terminals (ports), and more particularly, to a multi-port device analysis apparatus and method and a calibration method of the multi-port analysis apparatus for measuring various parameters of a multi-port device with high efficiency and high dynamic range without changing connections between the multi-port device under test and the analysis apparatus.
BACKGROUND OF THE INVENTION
In order to analyze the characteristics of the communication devices or communication components (device under test) used in various communication systems, a network analyzer is frequently used. A network analyzer obtains various test parameters, such as a transfer function, reflection characteristics, and phase characteristics (hereafter “scattering parameter S” or “S-parameter”), of a device under test. Such S-parameters are known in the art and determined by observing the frequency response (voltage and phase) of the device under test resulted in response to a sweep frequency signal from the network analyzer.
A network analyzer is usually comprised of two ports, one is input port and the other one is output port. The input port sends a sweep frequency signal (test signal) to the device under test and the output port receives the response output signal of the device under test. The input port and the output port of the network analyzer are usually organized such that either port can be switched to the other by a switching operation in the network analyzer. An example of configuration of such a network analyzer is shown in a block diagram of FIG.
1
.
The configuration and operation of the network analyzer shown in
FIG. 1
is briefly explained. A network analyzer
10
has two input-output ports P
1
and P
2
which are connected to directional bridges (or directional couplers)
11
and
12
, respectively. Each of the bridges
11
and
12
functions as a signal separation circuit. A test signal from a signal generator
15
is sent to one of either the bridge
11
or bridge
12
which is selected by a switch
13
. The test signal (sweep frequency signal) is sent from the selected one of the port P
1
or port P
2
to the device under test. The test signal from the signal generator
15
is also sent to the inside of the network analyzer as a reference signal. Namely, this reference signal and the input signal from the bridge
11
or
12
are respectively provided to frequency converters
17
,
18
and
19
whereby converted to signals of a lower frequency.
The frequency converted input signal and the reference signal are respectively converted to digital signals by AD converter
21
,
22
and
23
. The digital signals are processed by a digital signal processor (DSP)
25
to determine S-parameters of the device under test. The S-parameters or other data derived from the S-parameters are displayed by a display
29
in various formats under the control of a CPU
28
which controls the overall operation of the system.
The devices to be tested, for example, components such as used in communication devices and systems, are sometimes formed with not only two terminals but also three or more terminals (hereinafter may also be referred to as “multi-port device”). In order to measure the S-parameters of the multi-port devices, an S-parameter test set having three or more ports may be used in combination with the network analyzer having two ports. Such an example is shown in
FIG. 2
wherein a three port DUT is connected to a three port S-parameter test set having three ports.
In using the three port test set of
FIG. 2
, before connecting the DUT to test ports
90
,
92
and
94
, the test set is preferably calibrated to test the DUT with high accuracy. Typically, such a calibration process is conducted by using a predetermined two port calibration set between the test ports
90
and
92
, between the test ports
92
and
94
, and between the test ports
94
and
92
. Then the DUT is connected to the test set and the S-parameters are measured.
The process for measuring the S-parameters of three port device with use of the conventional network analyzer is described in more detail.
FIG. 3
is block diagram showing an example of network analyzer designed for three port device testing. The network analyzer
200
of
FIG. 2
includes a three port test set therein, and thus functions in the same manner as the example of FIG.
2
.
The network analyzer
200
includes a signal source
210
which is a sweep frequency signal, switches
212
,
214
,
216
,
218
and
220
, each having two switching circuits (designated by circle
1
and circle
2
), a receiver circuit
222
and three direction bridges (couplers)
230
,
232
and
234
. The receiver circuit
222
includes three measurement units
224
,
226
and
228
. The receiver circuit
222
of
FIG. 3
thus corresponds to the frequency converters
17
,
18
,
19
and the A/D converters
21
,
22
,
23
and the DSP
25
of FIG.
1
. The measurement unit
228
is to measure a signal level of the signal source
210
, i.e., a reference level “R”. The other measurement units
224
and
226
are to measure signal levels of output signals (transmission signal and/or reflection signal) from the device under test. In this example, measured results based on the voltage ratio between the measurement units
224
and
228
is denoted as “measurement A” and measured results based on the voltage ratio between the measurement units
226
and
228
is denoted as “measurement B”.
FIG. 4
is a table showing between types of S-parameters and switch settings and number of signal sweep operation when testing the S-parameters of the three port device
40
by the network analyzer of FIG.
3
. In
FIG. 4
, labels SW
1
-SW
5
correspond to the switches
212
-
220
, respectively. When the switching circuit (circle
1
or circle
2
) in the switch is ON, it is connected to a path to other circuit components, and when the switching circuit is OFF, it is connected to the ground through a terminal resistor.
The three port device (DUT)
300
is connected to test ports
240
,
242
and
244
of the network analyzer
200
. First, the switch setting is made so that the test signal is provided to the DUT
300
through the test port
240
. Under this condition, the network analyzer
200
measures S-parameters S
11
, S
21
and S
31
of the DUT
300
. For example, for measuring S-parameter S
11
, the test (sweep frequency) signal
210
is supplied to the DUT
300
through the switch
212
(SW
1
) and the test port
240
. At the same time, a reflected signal from an input terminal (
1
) of the DUT
300
is received by the measurement unit
224
through the directional bridge
230
and the switch
216
(SW
3
) to conduct the “measurement A”. Also at the same time, for measuring S-parameter S
21
, a transmission signal from a terminal (
2
) of the DUT
300
is received by the measurement unit
226
through the bridge
232
and the switches
218
(SW
4
) and
220
(SW
5
) to conduct the “measurement B”. Thus, S-parameters S
11
and S
21
can be measured by a single sweep of the test signal
210
.
For measuring S-parameter S
31
, while applying the test signal
210
to the terminal (
1
) of the DUT
300
through the test port
240
, a transmission signal from the terminal (
3
) of the DUT
300
is measured. Thus, the switch
5
is changed its connection so that the transmission signal from the terminal (
3
) of the DUT
300
is received by the measurement unit
226
through the directional bridge
234
and the switch
220
. As in the foregoing, for measuring S-parameters S
1
, S
21
and S
31
, the sweep signal must be applied to the terminal (
1
) by two times as shown in the left column of FIG.
4
.
In a similar manner, by applying the test signal to the terminal (
2
) of the DUT
300
, the network analyzer
200
measures S-parameters S
12
, S
22
and S
32
of the DUT
300
under the settings shown in the center column of FIG.
4
. The network
Nakayama Yoshikazu
Wagata Hirotaka
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