JPH0718898B2 - Impedance measurement method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of measuring a signal source and a load impedance of a transistor evaluation unit having an input / output circuit as seen from the transistor side.

Conventional technology When measuring the power characteristics or noise characteristics of a transistor at high frequencies (for example, frequencies above several GHz),
It is necessary to measure the signal source and load impedance added to the transistor without fail. For example, when measuring power characteristics, it is necessary to measure the signal source and load impedance to obtain the maximum output, and when measuring noise characteristics, measure the signal source and load impedance that give the minimum noise value. There is a need to. These signal sources and load impedances are impedances seen from the transistor side to the signal source side and the load side, and it is extremely difficult to measure with a simple measurement method from the impedance measurement reference plane that is usually performed. .

The conventional method for measuring the signal source and the load impedance is to configure the evaluation unit of the transistor having the input / output circuit so that the input side and the output side can be separated at the transistor part, and After measuring the noise characteristics while adjusting the input / output circuit, the evaluation unit was separated, connectors were added to the input side and output side units, and the impedance was measured individually from the transistor side.

However, in such a method, the evaluation unit of the transistor having the input / output circuit must be configured in advance so that the input / output and the output side can be separated at the transistor portion. It cannot measure itself. Also, after separating the unit,
Since the connector must be connected to the circuit for impedance measurement, and the signal source and the load impedance change due to this connector, accurate measurement cannot be performed, resulting in a large error.

FIG. 4 is a plan view and a sectional view of an evaluation unit used in a conventional signal source and load impedance measuring method.

In FIG. 4 (a), the transistor package is located at the center of the jig, and the input side printed board 12 and the output side printed board
Connected to 13 microstrip lines. In this state, connect the evaluation unit to the measurement system using connector 5,
Microstrip line 14 for power characteristics or noise characteristics
Measure while adjusting.

FIG. 4 (b) is a plan view B- of FIG. 4 (a).
A cross-sectional view taken along line B'is shown. As a support base formed of a material such as copper or aluminum, an input side block 17 and an output side printed board 13 are provided under the input side printed board 12.
An output side block 19 is provided under and a transistor block 18 is provided under a region where a transistor package is placed, and they are respectively connected and used as a ground. These three blocks are separable from each other and are connected to each other when the power characteristic or the noise characteristic is measured while adjusting the microstrip line 14 as shown in FIG. 4 (a).

FIG. 5 is a cross-sectional view showing a method of measuring the values of the signal source and the load impedance viewed from the transistor side after adjusting the microstrip line by the power characteristic or the noise characteristic. For example, when measuring the signal source impedance,
The transistor block 18 shown in FIG. 7A is separated and removed, the input side block 7 on which the input side printed board 12 is mounted is taken out, and the transistor side connector 20 is newly connected to the transistor side of the input side printed board 12. A 50 ohm load 8 is connected to the connector 15 of the evaluation unit, the measurement connector 3 having the impedance measurement reference plane 4 that has already been subjected to error correction is connected to the transistor side connector 20, and the signal source impedance is measured. The measuring connector 3 is connected to the impedance measuring device via the coaxial cable 2. To measure the load impedance, follow the same procedure as for measuring the source impedance.
This is performed for the output side printed circuit board 13 which is an output circuit and the output side block 19 located therebelow.

Problems to be Solved by the Invention In the conventional signal source and load impedance measuring methods shown in FIGS. 4 and 5, after measuring the power characteristic or the noise characteristic while adjusting the pattern of the microstrip line, When measuring the signal source and the load impedance, the transistor block located in the central part of the evaluation unit must be separated and measured. It must be configured so that and can be separated in advance. Therefore, the impedance itself cannot be measured by the evaluation unit that cannot be separated and the evaluation unit that cannot add a new connector. Even after the evaluation unit is separated, even if a new connector can be connected to the input or output circuit for impedance measurement, the signal source and load impedance change due to the newly added connector, so the higher the frequency becomes. There was a very big problem that the error became so large that accurate measurement could not be performed.

The present invention has been made in view of the above point, and in measuring a signal source and a load impedance, a transistor evaluation unit having an input / output circuit is configured so that an input side and an output side can be separated in advance at a transistor portion. It is an object of the present invention to provide an excellent impedance measuring method that is simple and has high accuracy without the need for preparation.

Means for Solving the Problems In order to solve the above-mentioned problems, in the present invention, after error correction of an impedance measurement reference plane of an impedance measurement system,
Connect one end of the unit to be measured with two terminals to the impedance measurement reference plane, and connect the other end of the unit to be measured with 50 ohm load, short load, and open load in sequence, and measure the impedance of the unit to be measured from the impedance measurement reference plane. Measure each. From the impedance value obtained by sequentially connecting a 50 ohm load, a short load, and an open load to the other end of this unit to be measured, select the unit to be measured from the other end of the unit to be measured that is not connected to the impedance measurement reference plane. Calculate the observed impedance.

Effect The present invention calculates the impedance of the other end of the unit to be measured from the values of the three types of impedances seen from one end of the unit to be measured having two terminals according to the configuration described above. It is not necessary to previously configure the unit to be measured having the output circuit into the input side and the output side, and it is possible to measure the unit to be measured that cannot be separated. Further, according to the present invention, it is not necessary to newly connect a connector to the input or output circuit for measuring the signal source and the load impedance, and therefore, it is possible to perform the measurement accurately even in the high frequency region.

EXAMPLE FIG. 1 is a block diagram showing the principle of the impedance measuring method of the present invention. In FIG. 1, a measuring connector 3 is pulled out from an impedance measuring device 1 via a coaxial cable 2. The impedance measurement reference plane 4 is corrected in advance and set on the end face of the measurement connector 3. The unit under test 5 has an input terminal 6 and an output terminal 7
It has two terminals. The input terminal 6 is connected to the measurement connector 3 which is the impedance measurement reference plane 4, and the following procedure is used to obtain the impedance value viewed from the output terminal 7.

1. With the input terminal 6 connected to the measurement connector 3 which is the impedance measurement reference plane 4, connect the output terminal 7 to the 50 ohm load 8 and measure the impedance viewed from the impedance measurement reference plane 4 with the impedance measuring device 1. To do.

2. Remove the 50 ohm load 8 from the output terminal 7, connect the short-circuit load 9, and measure the impedance viewed from the impedance measurement reference plane 4 with the impedance measuring device 1.

3. Remove the short load 9 from the output terminal 7 and open the load.
10 is connected and the impedance measured from the impedance measurement reference plane 4 is measured by the impedance measuring device 1.

4. The impedance value seen from the output terminal 7 of the unit to be measured 5 is calculated from the above three measurement results.

FIG. 2 is a signal flow graph explaining this calculation method. The output end face 11 in FIG. 2 corresponds to the end face of the output terminal 7 in FIG. If the unit to be measured is expressed by S parameters, four parameters (E11, E21, E12, E2
An equivalent circuit can be created in 2). The impedance seen from the output terminal 7 of the unit to be measured 5 in FIG.
It corresponds to E22 in the signal flow graph shown in the figure. Therefore, three loads that are already known as the reflection coefficient EN of the load (reflection coefficient 0 from 50 ohm load, -1 for short load, +1 for open load) are connected to the output end face 11 and the impedance measurement reference plane 4 The impedance seen from E22, that is, the impedance seen from the output terminal 7 of the unit to be measured 5, can be obtained by calculating the impedance from Eq.

FIG. 3 is a plan view and a sectional view of a transistor evaluation unit showing an embodiment of the impedance measuring method of the present invention. In FIG. 3, components and elements equivalent to those in FIG. 5 are designated by the same reference numerals and symbols. As shown in FIG. 3A, the impedance measurement reference plane 4 can be obtained by using the impedance measuring method of the present invention.
With the circuit connected to the input terminal of the evaluation unit, the impedance of the signal source or the load can be measured from the center of the evaluation unit where the transistor was located.

For example, when measuring the signal source impedance, the impedance measurement reference surface 4 is connected to the input end of the input side printed board 12 of the evaluation unit, and the reflection coefficient is known at the center of the evaluation unit where the transistor was located. The reference load 21 is connected to the input side printed board 12 and the impedance is measured from the impedance measurement reference surface 4. Standard load 21
A 50 ohm load, a short load, and an open load are connected, and the signal source impedance is calculated from the obtained three impedance values. When measuring the load impedance, it can be calculated by connecting the impedance measurement reference plane 4 to the output side of the output side printed board 13 and following the same procedure.

FIG. 3 (b) is a sectional view taken along the line AA 'in FIG. 3 (a). Even if the measurement block 16 cannot be separated when the impedance measuring method of the present invention is used. It indicates that the signal source or load impedance can be measured.

The impedance measuring method of the present invention is not limited to the measurement of the signal source or the load impedance of the transistor evaluation unit, and is very effective for the measurement of the impedance measured object to which the impedance measurement reference plane cannot be directly connected. Needless to say.

Effects of the Invention As described above, the present invention provides the following effects.

(1) The impedance value seen from the other end can be obtained in a state where one end of the unit to be measured is connected to the impedance measurement reference plane.

(2) It is possible to measure the signal source or the load impedance seen from the transistor side of the evaluation unit of the transistor in which the input / output circuit, which cannot be measured conventionally, cannot be separated.

(3) Since it is not necessary to connect a new connector to measure the signal source or the load impedance, the error is small and the impedance can be measured accurately.

[Brief description of drawings]

FIG. 1 is a block diagram showing the principle of the impedance measuring method of the present invention, FIG. 2 is a signal flow graph explaining the impedance calculating method of the impedance measuring method of the present invention, and FIG. A plan view of a transistor evaluation unit showing an embodiment of an impedance measuring method of the present invention, FIG. 3 (b) is a sectional view taken along line AA ′ of the plan view shown in FIG. 3 (a), and FIG. FIG. 1A is a plan view of an evaluation unit used in a conventional impedance measuring method,
FIG. 4 (b) is a plan view taken along the line BB ′ of FIG. 4 (a).
5 is a sectional view taken along the line, and FIG. 5 is a sectional view showing a conventional impedance measuring method. 1 ... Impedance measuring device, 2 ... Coaxial cable,
3 ... Measurement connector, 4 ... Impedance measurement reference plane, 5 ... Unit to be measured, 6 ... Input terminal, 7 ...
Output terminal, 8 ... 50 ohm load, 9 ... short load,
10 …… Open load, 12 …… Input side printed board, 13 ……
Output side printed board, 14 …… Microstrip line, 16
…… Measurement block, 21 ………… Standard load.

Claims (1)

[Claims] 1. An impedance measurement system is error-corrected and an impedance measurement reference plane is set, and then one end of a unit to be measured having two terminals is connected to the impedance measurement reference plane and at the other end of the unit to be measured 50. Ohm load, short load, open load are connected in sequence and the impedance of the unit to be measured viewed from the impedance measurement reference plane is measured, and the unit to be measured is viewed from the other end of the unit to be measured that is not connected to the impedance measurement reference plane. Impedance, characterized in that it is calculated using the impedance of the unit to be measured seen from the impedance measurement reference plane obtained by sequentially connecting a 50 ohm load, a short load, and an open load to the other end of the unit to be measured. Measuring method.