JPS6114469B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for measuring cross-modulation characteristics and two-signal amplification load characteristics of transistors, particularly ultra-high frequency transistors.

When evaluating ultra-high frequency transistors and designing applied circuits, it is necessary to understand third-order intermodulation distortion and amplification load characteristics, and the measurement method becomes an issue.

The magnitude of cross-modulation distortion largely depends on the load impedance of the transistor even when the output power is constant. Normally, the intermodulation distortion characteristics and the two-signal amplification load characteristics with respect to the load impedance of a transistor are measured by changing the load using an impedance matching tuner (tuner) and measuring the relationship between the load impedance and the third-order intermodulation distortion ratio and output power. It is measured by a method called -pull method. In this measurement method, it is necessary to know the load impedance at each measurement point, so the tuner is removed at each measurement point and the load impedance is measured. However, in this case, there is a problem with the reproducibility of the connections, especially in the ultra-high frequency range, and when the impedance of the matching box is measured and calibrated in advance, there is a problem with the mechanical reproducibility of the impedance.

Furthermore, in general, the higher the frequency, the more difficult it is to manufacture a matching box with low loss and excellent mechanical reproducibility of impedance, and this is especially problematic when measuring the intermodulation distortion vs. load impedance characteristics of ultra-high frequency, low impedance power transistors. It was hot. Regarding output load characteristic measurement, refer to "equivalent load
There is a method called the "pull method" that measures the output power by electrically changing the load impedance without using an impedance tuner, but the load impedance can only be changed at a single frequency at which the amplification operation is being performed; It could not be used to measure cross-modulation characteristics or two-signal amplification load characteristics where multiple frequencies coexist.

SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus for measuring cross-modulation characteristics and two-signal amplification load characteristics of ultra-high frequency transistors that does not have the above-mentioned drawbacks.

The details of the present invention will be explained below using the drawings.

FIG. 1 is a diagram for explaining the principle of the present invention. In the figure, 19 is a jig that mounts the transistor to be measured and is equipped with ultra-high frequency signal input/output terminals, 15 is a matching circuit that constitutes the transistor input circuit, and P _1j is the frequency f _j to the transistor input circuit. , (j=1,2) input signal power, V
_2i , V _3i and V _Ti are the frequencies f _i to the transistor output terminal A, respectively (where i=1, 2, 3,
4) are the injected wave voltage, reflected wave voltage, and terminal voltage, and Z _O represents the characteristic impedance of the measurement circuit system. Frequency f _i when looking at the load from output terminal surface A
Let _{Γ Li} be _the reflection coefficient and _{Y Li be the admittance at}
Since there is a relationship of i=1, 2, 3, 4(1), the following equation holds true.

From equation (2), the load admittance Y at each frequency
_Li can be changed by changing V _2i /V _3i .

Here, when signal powers P ₁₁ and P ₁₂ at frequencies f ₁ and f ₂ are added to the input circuit of the transistor under test, due to the nonlinearity of the transistor, in addition to the output powers at frequencies f ₁ and f ₂ , the output power is Output powers at frequencies 2f ₁ -f ₂ and 2f ₂ -f ₁ , which are third-order intermodulation distortion components, are also generated at the same time. To measure the third-order intermodulation distortion versus load impedance characteristics, f ₁ , f ₂ , 2f ₁ −
The impedance for frequencies f ₂ and 2f ₂ −f ₁ must be controlled simultaneously. Here f ₃ = 2f ₁
If −f ₂ , f ₄ = 2f ₂ −f ₁ , then from equation (2) the load impedance for the above four frequencies is an appropriate V _2i
can be controlled by injecting

Let the amplitude of each voltage V _Ti , V _2i and V _3i be V〓
_Ti , V〓 _2i and V〓 _3i , the power injected into the output terminal P _2i and the reflected wave power P _3i are respectively P _2i = 1/2Y _O V〓 ² _2i i = 1, 2, 3, 4(
3) P _3i = 1/2Y _O V〓 ² _3i i=1, 2, 3, 4(
4) is given by. However, Y _O =Z _O ^-1 .

Here, if G _Li = Re (Y _Li ), the output generated power P _Ti for each signal of the transistor is P _Ti = P _3i - P _2i = 1/2 G _Li V 〓 ² _Ti where i = 1, 2, 3, 4 (5) is given. Here, the subscript i means a signal of frequency f _i . Therefore, when P ₁₁ and P ₁₂ are made equal and all V _2i are controlled to make all Y _Li equal, the third-order intermodulation distortion ratio IM ₃ (d _B ) is given by the following equation (where Y _Li is When taking frequency characteristics into consideration, all Y _i are not made equal, but each Y _Li is set to a desired value.

IM ₃ (d _B )=10 log ₁₀ P _T1 /P _T3 or 10 log ₁₀ P _T2 /P _T4 (6) Y _Li can be moved on the entire admittance plane by changing the magnitude and phase of the injection signal V _2i It can be seen that the cross-modulation characteristics of a transistor can be measured based on this principle. Also P _T
1 /P ₁₁ and P _T2 /P ₁₂ allows the gain of each of the two input signals to be known. Furthermore (P _T1
+P _T2 )/(P ₁₁ +P ₁₂ ), the output load characteristics in the normal sense (in the case of only a single frequency) can be approximated (in actual circuit design, an amplifier with multiple input signals is designed (in many cases, it is designed from the load characteristics of only a single frequency). Therefore, it is possible to measure not only the intermodulation distortion ratio but also the amplification load characteristics at the same time.
Equal distortion rate curves and equal gain curves can be obtained without removing the tuner unlike load bull measurements. FIG. 2 is a configuration diagram of a measuring device showing an embodiment of the present invention based on the principle explained above.

In the figure, the outputs of a microwave oscillator 1 with an oscillation frequency f ₁ and a microwave oscillator 2 with an oscillation frequency f ₂ are composed of a mixer, an amplifier, a duplexer, etc., and a third-order distortion generation mechanism, the generated frequency 2f ₁ −f ₂ , The signal is input to a signal generator 3 equipped with a mechanism for demultiplexing the third-order intermodulation distortion component of 2f ₂ -f ₁ and fundamental wave components of f ₁ and f ₂ , and a mechanism for amplifying the separated four waves. The signal generator 3 has an output terminal 4 with a frequency f ₁ , an output terminal 5 with a frequency f ₂ , an output terminal 7 with a frequency 2f ₁ −f ₂ , and an output terminal 6 with a frequency 2f ₂ −f ₁ , the output of the terminal 4 is divided into two into B and C by the 3d _B directional coupler 8, and the output of the terminal 5 is divided into two into D and E by the 3d _B directional coupler 9.
To divide. The divided signal D is passed through the variable resistance attenuator 1
0, the signal B is combined with the 3D _B directional coupler 11, and the signal to be measured passes through the variable resistance attenuator 12, the signal branching directional coupler 13 for power and frequency measurement, the bias network 14, and the impedance tuner 15. It is injected into the input side of transistor 19. Here, 17 is a wavelength meter for measuring input signal frequency;
18 is a power meter for measuring input signal power, and 16 is a resistance attenuator. On the other hand, a signal C with a frequency of f ₁ , a signal E with a frequency of f ₂ , a signal F with a frequency of 2f ₁ - f ₂ , and
The signal G with a frequency of 2f ₂ −f ₁ is transmitted through a variable phase shifter 20,
21, 22 and 23, variable resistance attenuator 24, 2
5, 26 and 27, three 3D _B directional couplers 2 placed to combine these four signals.
8, 29 and 30, a directional coupler 31 used for signal branching for injected signal spectrum measurement, a circulator 36 whose third terminal H is terminated with a 50Ω termination 37 for use as an isolator, a bias network 38, an output wave signal It is injected into the output terminal A of the transistor via the isolation circulator 39. 32 is a variable resistance attenuator, 35 is a spectrum analyzer for measuring the power spectrum of injected waves, 34 is a power meter for calibrating the injected power, 33 is a directional coupler, 40 is a DC block, and 44 is a spectrum analyzer for measuring the power spectrum of output waves. , 41 is a directional coupler, 42 is a resistance attenuator, 4
3 is a power meter for calibrating the reflected wave power. The outputs of the spectrum analyzers 35 and 44 are each input as a function of frequency, and the output of the wattmeter 18 is input to a data integrator 62, which is connected to the display unit 6.
4, and displays the relationship between the input two-wave total signal power and the output fundamental two-wave total signal power. In order to measure the impedance Z ₂ looking at the transistor output terminal or the reflection coefficient Γ ₂ or its reciprocal value 1/Γ ₂ looking at the output terminal, the wave injected into the output terminal A and the wave reflected are separated. Therefore, two directional couplers 74 and 45 are connected to separate the injected wave as a reference signal to the J terminal, and the reflected wave to the I terminal.

In order to measure the reflection coefficient (or impedance), it is necessary to compare the phase and amplitude of the incident wave and reflected wave at a single frequency, so before inputting the four signals to the amplitude/phase comparator,
Need to separate signals. In this case, if the four signals are arranged in a periodic time series, one amplitude phase comparator can calculate the reflection coefficient (or impedance) of the four signals.
can be measured. For this reason, these four signals are demultiplexed, but with a large relative detuning degree,
In order to ensure demultiplexing, the I and J terminals are connected to frequency converters 46 and 47, respectively, to lower the center frequency and increase the relative detuning between the four signals. After that, the output wave signals of four frequencies are separated into terminals 50, 51, 52, and 53 by the splitter 48, and the four output wave signals are arranged in a periodic time series by the time division circuit 58, and then the frequency is lowered to improve measurement accuracy. The signal is input to a harmonic converter 60 for increasing the pitch. Similarly, a splitter 49 separates the injection wave signal of four frequencies into terminals 54, 55, 56, and 57, and a time division circuit 59 synchronized with a time division circuit 58
After the four input wave signals are arranged in time series, they are input to the harmonic converter 60. Two waves, an injection wave signal and an output wave signal, output from the harmonic converter 60 are input to an amplitude/phase comparator 61 equipped with a display section.

In addition, to measure the transistor output impedance Z ₂ or the equivalent load impedance Z _L = -Z ₂ which is its opposite sign value -Z ₂ , the reference signal channel (injection wave channel) and the test signal channel (output wave channel) are connected. Just replace it. In this measurement method, an impedance matching device for output matching is not used to measure intermodulation distortion characteristics and two-signal amplification load, and the output load can be changed equivalently by injection waves. The load impedance of the transistor during 2-signal amplification load measurement operation can be viewed directly. Such effects of the present invention become noticeable in the measurement of high frequency bands and low impedance elements in the microwave band, where it is difficult to manufacture highly accurate impedance matching devices.

Further, as an applied device of the present invention, means for detecting the transistor output generated power P _Ti , which is the difference between the injected power P _2i of each frequency to the transistor output terminal A and the reflected wave power P _3i , is provided in the device configuration diagram of FIG. and an attenuator 2 so as to draw an impedance curve of the output terminal impedance of the transistor to be measured or its negative value on the display device based on the detected value so that the intermodulation distortion ratio gives a desired constant value.
4, 25, 26 and 27, variable phase shifters 20, 2
1, 22, and 23, and also accumulates data of two-signal amplification gain when measuring the third-order intermodulation distortion ratio curve, and simultaneously displays the third-order intermodulation distortion curve and equal amplification gain curve. A device for automatically measuring ultra-high frequency transistor characteristics can also be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the principle of the present invention, and FIG. 2 is a configuration diagram showing an embodiment of the present invention. In the figure, 19 is a transistor to be measured, 15
is an impedance matching device, 3 is a four-signal generator with a constant frequency difference between adjacent signals, 8, 9, 11,
28, 29 and 30 are 3d _B directional couplers, 2
0, 21, 22 and 23 are variable phase shifters, 13,
31, 33, 41, 74 and 45 are directional couplers, 17 is a wavelength meter, 18, 34 and 43 are power meters, 35 and 44 are spectrum analyzers,
40 is a DC block, 46 and 47 are frequency converters, 48 and 49 are duplexers, 58 and 59
60 is a time division circuit, 60 is a harmonic converter, 61 is a phase and amplitude comparator, 62 is a data integrator, 63 is a minicomputer, and 64 is a display section.

Claims (1)

[Claims] 1. An ultra-high frequency signal generator that generates four signals each having an oscillation frequency with a constant frequency difference between adjacent signals; A circuit that divides each of the two signal powers other than the low frequency signal power into two and combines the two divided signal powers, and connects the combined two signal powers to the input terminal of the transistor under test. an attenuating control circuit and a phase control circuit for attenuating each of the four signal powers of the other two divided signal powers and the two signal powers of the highest frequency and the lowest frequency that were not divided; and a second terminal for injecting the combined four signal powers into the output terminal of the transistor under test, the second terminal of the transistor connected to the second terminal. Two directional couplers are connected in cascade between the terminal of the terminal and the transistor output terminal for monitoring the forward wave and the backward wave, respectively, and two terminals to which the forward wave and the backward wave are output for monitoring. A cascade connection circuit of each frequency converter and a duplexer for demultiplexing the four signals is connected to the duplexer, and a total of eight forward waves and backward waves regarding the four signals taken out from the duplexer are connected to the duplexer. An ultra-high frequency transistor measuring device characterized by having means for independently measuring amplitude and phase. 2. In order to generate four ultra-high frequency signals, each with a constant frequency difference between adjacent signals, use two arbitrary signals with different frequencies as input signals, and separate the desired four signals using a mixer and a splitter. An ultra-high frequency transistor characteristic measuring instrument according to claim 1, comprising means for generating ultra-high frequency transistor characteristics. 3 In the difference between the reflected wave power and the injected wave power from the transistor output terminal at each frequency of the four detected signals, the sum of the detected power regarding the highest frequency and the lowest frequency and 2 excluding the highest frequency and the lowest frequency Claim 1, comprising a device for displaying the sum of detected powers for each signal.
The ultra-high frequency transistor characteristic measuring device described in Section 1. 4. A first terminal for extracting a wave incident on the output terminal of the transistor as a reference signal of a device for measuring the reflection coefficient (or the reciprocal value of the reflection coefficient) looking at the output terminal of the transistor to be measured; The second one extracts the reflected wave from the output terminal of
a terminal, two branching filters connected to these first and second terminals for separating the four signal frequencies, and a time division circuit synchronized with both the incident wave circuit and the reflected wave circuit. and arrange each of the incident waves and reflected waves of the four signal frequencies in time series to calculate the impedance (or the opposite sign value of the impedance) or the reflection coefficient (or the reciprocal value of the reflection coefficient) regarding the four signal frequencies. An ultra-high frequency transistor characteristic measuring device according to claim 1, which is adapted to measure ultra-high frequency transistor characteristics. 5. In the device according to claim 4,
An ultra-high frequency transistor characteristic measuring device that includes a frequency converter between a first terminal, a second terminal, and two branching filters.