JP2008541031A - Dynamic measurement of the impedance of microwave components. - Google Patents

Abstract

The present invention relates to the field of dynamic measurement of properties associated with electronic components, which can be performed for continuous (CW) or pulsed operating modes. The subject is the following steps:
a) during which a CW signal of duration T is applied to the input of the component at the time of occurrence t0 to stimulate the component;
b) measuring the amplitude and phase of the input and reflected signals to the component at the stimulated input;
c) calculating the instantaneous impedance of the component starting from the amplitude and phase of the measured signal;
d) a method for measuring the dynamic impedance of the electronic component comprising the step of stopping the stimulation. In this method, steps a) to d) are performed in such a way that the duration of the stimulation T and the value of the time interval Δt increase during each iteration, and two successive iterations during which the internal temperature returns to ambient temperature. Characterized in that it is repeated in an iterative manner, separated by an intermediate step in which the voltage of the component is cut off. The invention is particularly applicable to the dynamic measurement of the nonlinear impedance of microwave electronic components such as diodes or transistors.
[Selection] Figure 1

Description

  The present invention relates to the field of dynamic measurement of properties associated with electronic components. The invention is particularly applicable to dynamic measurements of nonlinear impedances of microwave electronic components such as diodes or transistors, which can be performed for continuous (CW) or pulsed operating modes.

  To date, measurements made in the laboratory have determined the optimum impedance to be applied to the electronic components, such as diodes or transistors, that are being tested to optimize their performance in terms of power, efficiency, or more generally gain. It is possible. This type of measurement is well known to those skilled in the art, for example based on the use of load pull type test equipment. Such test equipment generally operates at the fundamental frequency of the signal for which optimization of the component under test is desired. They make use of mechanical or sometimes electronic type adjustment means.

  For components operating in pulse mode, impedance determination is always performed using a fixed pulse duration and a fixed repetition period of the signal applied to the component under test. Furthermore, this determination is made only when the component under test reaches thermodynamic equilibrium, in other words, when its junction temperature is practically stable. Finally, as described above, impedance measurements are generally performed at the fundamental frequency of the signal.

  Current measurements thus only allow the average value in the pulse of the impedance of the component to be tested to be determined. They do not produce any indication for the dynamic variation of the component's impedance within one pulse, for example, at the fundamental and harmonic frequencies of the signal required to optimize the component under test.

  Furthermore, the use of uniform stimuli with fixed pulse duration and repetition period is particularly inconvenient for determining the impedance of a component when the actual operation of the component differs from this simple schematic. Prove that. This is especially the case for microwave components applied in radar transmission or reception systems where the duration and repetition period of transmitted or received pulses varies according to the mode of operation performed at a given moment.

  Current measurements also allow for fluctuations in impedance to the output of the component during the transmission of the first few pulses while the temperature at the junction of the component to be evaluated is rapidly changing Don't make it. This temperature measurement is actually very important because it is linked to the pulse-to-pulse stability, phase and amplitude characteristics of the subassembly that integrates the component being tested.

  The impedance measurements that have been made so far only allow a limited characterization of the impedance of a given component.

  One of the objects of the present invention is to improve the determination of the impedance of an electronic component that is desired to characterize its operation in the presence of a given signal, particularly a pulse signal of variable duration and repetition period. . Another object of the present invention is to allow the establishment of a variation curve with respect to time of this impedance when a signal is applied to a component.

For this reason, one of the subjects of the present invention is the following steps:
a) during which a CW signal of duration T is applied to the input of the component at the time of occurrence t0 to stimulate the component;
b) measuring the amplitude and phase of the input and reflected signals to the component at the stimulated input;
c) calculating the instantaneous impedance of the component starting from the amplitude and phase of the measured signal;
d) a method for measuring the dynamic impedance of an electronic component comprising the step of stopping stimulation.

  In this method, steps a) to d) are performed in such a way that the duration of the stimulation T and the value of the time interval Δt increase during each iteration, and two successive iterations during which the internal temperature returns to ambient temperature. It is further characterized in that it is repeated in an iterative manner, separated by an intermediate step in which the component voltage is cut off.

  In accordance with the present invention, the method may include a stop condition corresponding to the mode of operation in which it is desired to know that the dynamic impedance of the component is being confirmed. The iteration is interrupted when the condition is confirmed.

  According to one variant embodiment, the stopping condition is confirmed when the stimulation duration T is longer than the pulse duration of the signal for which optimization of the component under test is desired. .

  According to another variant of the method according to the invention, the stopping condition is satisfied when the calculated impedance becomes substantially constant.

  According to another variant, the method according to the invention further comprises a step e) for storing a dynamic value of the calculated impedance, which allows the variation of the impedance with respect to time to be determined.

  This method advantageously performs temporal analysis of the applied and reflected signals in amplitude and phase. This temporal analysis may be associated with, for example, a multi-harmonic load-pull type matching test apparatus.

Another subject of the present invention is a generator of CW waves of at least -frequency FRF;
-Means for performing active impedance matching of components for which instantaneous impedance measurement is desired;
Means for performing a temporal measurement of the input signal and the reflected signal at the input of the component at a given time after the start of the CW wave. A device for measuring dynamic impedance, wherein the impedance of the component is calculated starting from the measured input signal and the reflected signal.

According to the invention, the device also comprises
A non-linear element that allows harmonics of the frequency FRF to be generated;
-Means for separating the harmonics, each harmonic traveling along a separate channel;
-Means for performing active matching of components for which instantaneous impedance measurement is desired for each harmonic;
-Means for recombining channels carrying various harmonics at the input of the component.

  The device according to the invention thus advantageously makes it possible to determine even if the impedance of the component under test matches several frequencies simultaneously.

A further subject of the present invention is
A measuring device according to the invention;
An automatic measuring and testing device comprising means for automatically executing the method according to the invention.

  Other features and advantages will become apparent during the description with reference to the accompanying drawings.

  Reference is first made to FIG. As will be described later, the figure shows a schematic flow chart of the main steps of the method according to the invention.

  The purpose of the method according to the invention is to allow, inter alia, fluctuations in the impedance of a component to which a composite microwave signal is applied to be measured at various times following the instant of the start of signal application to the component. It is. This composite signal, which can be, for example, a variable duration and repetitive period pulse signal, is simulated using a chopped CW stimulus signal applied in an iterative manner to an electronic component to be tested over a very long period of time. Is done. During the application of the stimulus, the instantaneous impedance of the component is calculated at a given time.

  The method according to the invention mainly comprises a first step 11 for stimulating the component to be tested, a second step 12 for measuring input and reflected signals present at the input of the component during the stimulus, and stopping the stimulus. 3rd step 13 for doing is included. These three steps are repeated in an iterative manner.

  Step 11 consists in stimulating the input of the component to be measured over the period T1 = Δt + T0 in the form of a chopped CW signal.

  The period T1 is here defined as being equal to the sum of the variable time interval Δt and the fixed time interval T0.

  According to the invention, the time interval Δt is reset to the value Δt0. With respect to the value of T0, this is determined as a function of the time taken to perform the measurement of step 12.

  Step 12 is performed during the execution of step 11. This step consists in measuring the amplitude and phase of the input and reflected signals present at the input of the electronic component under test after the time Δt defined in the previous section. A waiting loop 14 precedes it. The time taken to make these measurements of amplitude and phase determines a period T0 which must be at least equal to this measurement time. Here, the measurement of the input signal and the reflected signal is achieved by fast digitization over a very short time frame and storage of the digitized signal in memory. The impedance calculation of the component at the moment of measurement is then carried out conventionally, starting from the digitized signal.

  Step 13 constitutes a step for stopping the measurement. During this step, stimulus generation stops and voltage is removed from the component.

  If the form of the signal that it is desired to simulate at the input of the component is intended to consider the variation in the impedance of the component over the period that the signal continues, operations 11-13 are performed a fixed number of times at various times. Need to be repeated. For this purpose, the method according to the invention comprises an iterative loop consisting of steps 15, 16 and 17.

  Step 15 consists in increasing the time period Δt during which the chopped CW stimulus is applied to the component by a predetermined time period τ. This period τ is specifically defined as the number of impedance measurement points that it is desired to obtain over the duration of the signal simulated using the stimulus.

  Step 16 consists of a standby loop that occurs after stage 13 where the stimulation is stopped and the voltage is removed from the component under test. The purpose of this step is to allow the component to return to an internal temperature close to ambient temperature before proceeding with the new iteration of steps 11-13 with a new value of Δt.

  The waiting step advantageously makes it possible to ensure that the measurements made for subsequent iterations are not dependent on the preceding iterations, and in particular the component heat generated therefrom. This exotherm actually has the known result of changing the impedance value of the component.

  The number of iterations performed by the method according to the invention naturally depends on the signal that needs to be simulated. By changing the period Δt during each iteration, it is possible to form continuous pulses of increasing width and to make impedance measurements at a further distance from the start of stimulation. Thus, a measurement of the instantaneous impedance of the component distributed over the entire period of the simulated signal is obtained. Therefore, the entire set of measurements is obtained when the duration of the stimulus is equal to the duration of the signal that it is desired to simulate. The iterative process then ends.

  This stop condition is controlled, for example, by a test step 17 which tests whether the value of Δt after increasing by τ is greater or less than the duration of the simulated signal. If this is not the case, a new iteration is performed. Otherwise, the process ends.

  In order to process the measurements made in this way, the method according to the invention also includes a step 18 for storing the measurements made for each iteration and a step 19 for processing the stored data. be able to. The storage of the measured values advantageously enables off-line processing of the variation values over time of the component impedance values over the duration of the simulated signal.

  The method according to the invention, in its basic form illustrated in FIG. 1, is suitable for the instantaneous impedance of the component under test, particularly when a sinusoidal signal step or alternatively a microwave pulse signal with its long repetition period is applied to it. Handles the determination of variation.

  Indeed, in the case of a sinusoidal signal step, the impedance variation occurs within a predetermined time interval that follows the moment the step is applied. After this time interval, the impedance is stable at a given value and remains substantially constant. The stopping condition of step 17 is therefore applied for a period of time sufficient for the impedance to reach a substantially constant value that can be measured in a known manner, rather than over the duration of the signal.

  Similarly, if the applied signal is a narrow, long repetition period pulse signal, the temperature of the component will be equal to the ambient temperature or equal to the fixed temperature at each new pulse generation, It can then be considered that the impedance of the component follows the same variation for each pulse. The stop condition of step 17 is then applied for the duration of one pulse.

  If the applied signal takes a more complex form, the determination of component impedance variation can itself be more complicated. In order to determine the law of variation of the impedance corresponding to the applied signal, it may be necessary to chain the sequence of steps described for example in FIG. 1 several times.

  Nevertheless, the principle described in FIG. 1 remains valid.

  FIG. 2 illustrates by way of example the execution of the method according to the invention when the signal applied at time t 0 is a sinusoidal step 21.

  As shown in FIG. 2, the method according to the invention now includes N iterations, each iteration resulting in a measurement of the instantaneous impedance 22. During each new iteration, the duration 23 of the CW stimulus increases by a period τ, as well as the delay between the start time t0 of the stimulus and the time 24 of acquisition of the input and reflected signals.

  As illustrated in the figure, the graphs 26 and 27 of fluctuations in the amplitude and phase of the instantaneous impedance thus begin at the time t0 of the application of the stimulus 21 and the instant at which a substantially constant value 25 of the instantaneous impedance is established. Can be obtained.

  In this particular example, since the signal for which it is desired to know the impedance of the component is a step, the condition 17 for stopping the iteration shown in FIG. 1 is compared to the phenomenon represented by the impedance variation It is not a condition for the duration of this signal, which is theoretically infinite or at least very long. This condition here relates to the stabilization of the impedance value after a predetermined time ΔtN.

  Note that, as described above, a waiting phase 16 occurs between the two measurements that is designed to allow the internal temperature of the component to return to the initial ambient temperature.

  FIG. 3 also shows by way of example a second specific description of the method according to the invention. In this example, the method is applied to the dynamic determination of the impedance of an electronic component in which a sinusoidal pulse 31 is applied starting at time t0. This pulse is of constant duration and repetition period.

  The principle of carrying out the method according to the invention is the same as in the example of FIG. The stimulus applied to the input of the component to be tested consists in this example of a chopped CW signal 32 applied in a discontinuous manner for increasing periods.

  The condition 17 for stopping the iteration in this particular example takes into account that the impedance variation during one pulse is a function of the internal temperature of the component itself depending on the number of pulses already applied, It applies to many pulses that need to be simulated to account for the full variation law of component impedance. Thus, if the component is at its equilibrium temperature after P pulses, the determination of the impedance variation is determined by N of P consecutive cycles where each cycle is performed according to the method according to the invention as illustrated in FIG. Multiple measurements may be required. The applied stimulus then corresponds to a chopped CW signal as shown in FIG.

  The example in FIG. 3 illustrates the conditions for performing the method according to the invention when the applied signal is a pulsed sinusoidal signal of constant pulse duration and repetition period. This particular case can be easily generalized to a pulsed sinusoidal signal that exhibits pulses of variable duration and repetition period. In this more general case, illustrated in FIG. 4, the signal applied here consists of pulses 41 and 42 of different durations, and the time interval separating the two pulses is not constant.

  In this example, the time interval during which an instantaneous impedance measurement needs to be made again depends on the duration of the applied signal and the repetition period of these pulses, and the law of variation of impedance is such that the internal temperature is continuous. Is fully determined when measurements are made on components at equilibrium temperature.

  Reference is now made to FIG. 5 which schematically shows the structure of an apparatus that allows the method according to the invention to be carried out.

  As shown in the figure, the apparatus comprises a stimulus generating subassembly 51 that is applied to a component 52 under test. The subassembly 51 in particular comprises a sine wave (CW) generator Eg having an impedance Zg and a controllable chopper circuit 53.

  The device according to the invention also comprises acquisition means 54 which allow the determination of the instantaneous impedance value starting from the measurement of the input signal and the reflected signal present at the input of the component whose impedance is desired to be known.

  The acquisition means 54 can comprise a temporal acquisition system that performs ultra-high speed sampling of the input signal and the reflected signal, for example. This sampling is followed, for example, by digital processing of these signals. The sampling frequency of the acquisition means is much higher to enable sampling under Shannon conditions.

  The acquisition is controlled in particular by an acquisition command that defines the acquisition start time.

  The acquisition means 54 further comprises means for storing continuously calculated impedance values in the course of the continuous measurement performed, and means for displaying a curve of the calculated variation of impedance with respect to time. be able to.

  The device according to the invention also allows its direct channel to apply the stimulus generated by the subassembly 51 to the input of the component whose impedance is desired to be known and is connected to the input of the acquisition means 54. The disconnected channel comprises a coupling means 55 that allows the acquisition of the input (Ie) signal and the reflected (Re) signal simultaneously.

  As illustrated in FIG. 5, the device according to the invention can be advantageously completed as long as the acquisition means comprises two measurement channels by means of the second coupling means 56. The direct channel of this second coupling means is used to connect the output of the component under test 52 to the matching load 57, while the disconnected channel is connected to the input of the acquisition means 54.

  Such a device offers the advantage of allowing variations in component input and output impedances over time to be determined simultaneously.

  The device according to the invention shown in FIG. 5 can be used either manually or automatically, and all measurements, their parameterization and the execution of the method according to the invention are then controlled by the control computer 58.

  Reference is now made to FIG. 6, which shows a variant embodiment of the device according to the invention. In this variation forming the preferred embodiment, the apparatus illustrated in FIG. 5 determines the instantaneous impedance of the component 52 by performing dynamic matching of the input and output of the component under test. It is completed by the addition of means 61 that make it possible. Matching is now done to the (RF) frequency of the pulse signal for which it is desired to know the component impedance, but also the second harmonic (H2) and third harmonic of this signal. Also for (H3) or higher harmonics. Here, matching is achieved by adjusting the amplitude and phase of the signals applied to the input and output of the component by using appropriate means 62. Amplitude and phase matching is further performed separately for the fundamental signal, the second harmonic, and the third harmonic. Similarly, this matching is done independently of component inputs and outputs. Thus, correct alignment of the components can be achieved not only at the frequency of the pulse signal in question, but also at the nearest harmonic frequency that constitutes this pulse signal.

  Generation of stimuli including sufficiently high levels of harmonics is achieved using a subassembly 51 associated with a non-linear element 63, which can be, for example, a frequency multiplier. The signal produced by element 63 is then distributed across various channels 64, each including means 62 for controlling the amplitude and phase of the signal. Each of these means has a filter 65 for the input, which is adjusted in such a way that the channel is considered to process only one frequency. The signals thus processed are substantially recombined and applied directly to the input of the component under test and to its output via a single coupler 66.

  The use of dynamic matching means has the advantage that the device according to the invention can be used for multiple components and signals of various frequencies, in contrast to the use of conventional matching by wired electronic components. Have

  The device in the embodiment illustrated in FIG. 6 according to the invention can of course be used in a manual or automatic manner.

4 is a schematic flow chart of the steps of the method according to the invention. Fig. 2 is an implementation diagram of the method according to the invention with a stimulus having the form of a temporal step function. FIG. 2 is an implementation of the method according to the invention with a stimulus having the form of a pulse train of constant duration and repetition period. FIG. 2 is an embodiment of the method according to the invention with a stimulus having the form of a pulse train of variable duration. Fig. 2 is a schematic block diagram of an apparatus that enables execution of the method according to the invention. Fig. 2 is a detailed block diagram of an example of an apparatus that enables execution of the method according to the present invention.

Claims (9)

A method for measuring the instantaneous impedance of an electronic component comprising the following steps:
a) stimulating the component, wherein a stimulus of duration T is applied to the input of the component;
b) measuring, at the stimulated input, the amplitude and phase of the input and reflected signals for the component;
c) calculating the instantaneous impedance of the component starting from the amplitude and phase of the measured signal;
d) a method comprising: stopping the stimulation;
The steps a) to d) are repeated in an iterative manner, the value of the duration T of the stimulus and the value of the time interval Δt increase during each iteration, and two successive iterations between which the internal temperature is ambient The method is characterized in that it is separated by an intermediate step in which the voltage of the component is cut off in such a way that   The method of claim 1, wherein the iteration is interrupted when a stop condition corresponding to a mode of operation in which it is desired to know the dynamic impedance of the component relative thereto is determined.   If the duration T is longer than the duration of the pulse of the signal for which it is desired that the component under test be optimized, or the calculated impedance becomes substantially constant 3. The method of claim 2, wherein the stopping condition is satisfied.   4. The method according to any one of claims 1 to 3, further comprising step e) for storing the calculated dynamic impedance value. An apparatus for measuring the dynamic impedance of a component performing the method according to claim 1, comprising at least
-A CW wave generator of frequency FRF;
Means for performing active impedance matching of said component for which instantaneous impedance measurement is desired;
Means for performing measurements of input and reflected signals at the input of the component at a given time after the start of the CW wave. A non-linear element that generates harmonics of the frequency FRF;
-Means for separating said harmonics, each harmonic traveling along a separate channel;
Means for performing active matching of said components, for which instantaneous impedance measurement is desired, for each harmonic;
6. The apparatus of claim 5, further comprising means for recombining channels carrying various harmonics at the input of the component.   A system for simultaneously measuring input and output dynamic impedance of an electronic component, which incorporates two devices according to claim 6, one of which applies to the input of the component And the other device is applied to the output of the component.   The system of claim 7, wherein the two devices share a single CW generator. A measurement system according to claim 7;
Means for automatically performing the method according to any one of claims 1 to 4;

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