DE102017125386A1 - Pulse generator, test and selection method and imaging system - Google Patents

Abstract

The invention relates to a pulse generator for generating high repetition rate pulses comprising a pulse generating unit and a control unit. The pulse generation unit has a plurality of pulse generation sections. The control unit is signal-technically connected to each pulse generation section of the pulse generation unit. The control unit is configured to generate a plurality of trigger signals offset in time with respect to one another and to sequentially supply the individual time-offset trigger signals to different pulse generation sections, such that the pulse generation unit generates an output pulse sequence comprising a plurality of output pulses offset in time from one another and generated by different pulse generation sections. The invention also relates to a test method for determining a breakdown voltage of a bipolar transistor and a selection method for selecting matching breakdown voltages having bipolar transistors. The invention further relates to an imaging system having a pulse generator of the type mentioned.

Description

The invention relates to a pulse generator for generating pulses with high repetition frequency.

The invention further relates to a test method for determining a breakdown voltage of a bipolar transistor, in particular an avalanche transistor, and to a selection method for selecting bipolar transistors having matching breakdown voltages, in particular avalanche transistors.

The invention also relates to an imaging system comprising a pulse generator.

The pulses generated by the pulse generator may in particular be pulses of an electrical voltage (voltage pulses) or pulses of an electrical current (current pulses).

Pulse generators for generating very short pulses, in particular voltage pulses or current pulses, with a pulse duration of the order of nanoseconds are used for a variety of applications. In particular, this includes a variety of applications and applications in connection with electro-optical devices in various imaging systems (imaging systems). An imaging system is a system that performs an imaging procedure.

Furthermore, such pulse generators are used, for example, to control diode lasers, Pockels cells, electro-optic modulators and image intensifiers.

An image intensifier can be considered as a light amplifying non-linear modulator. By, for example, controlling the photocathode of an image intensifier with voltage pulses of sufficiently large amplitude, it is possible to provide a fast, electronically controllable shutter. The gain window of the image intensifier, i. the time window within which the image intensifier amplifies the optical signal received at its input, is thereby controlled via a gate input of the image intensifier to which a voltage pulse is supplied. This technique is called time gating. The optical amplification of the image intensifier can be used advantageously for the imaging or image acquisition of objects or processes that generate very low light intensities.

Time gating further reduces the number of photons that can be detected per unit of time. For this reason, multiple gating cycles may be necessary to produce images of sufficient quality. Therefore, a synchronization of the pulses supplied to the gate input of the image intensifier (so-called gating pulses) with an external reference is necessary in order to be able to realize imaging processes for repetitive dynamic processes.

Applications of such image intensifiers which have a short gain time window (so-called fast-gated image intensifiers) are, for example, in the field of medical imaging methods such as diffuse optical tomography, diffuse fluorescence tomography, fluorescence molecular tomography and time-resolved fluorescence lifetime imaging. In physics, applications of such image intensifiers are, for example, in the field of time-resolved spectroscopy, the imaging of trapped ions and plasma dynamics.

All of these applications require the generation of pulses of sufficiently large amplitude, short pulse duration and short rise and fall time, i. high slope.

To generate pulses having such properties, the prior art discloses the use of avalanche transistors, also referred to as avalanche transistors (avalanche transistors). In the context of the present application, an avalanche transistor is understood as meaning a bipolar transistor which is intended and / or suitable for operation in the avalanche breakdown region, in particular in the avalanche breakdown region of the collector-base diode (pn junction between collector and base) become. In the avalanche breakdown area, an avalanche effect occurs, through which the number of free charge carriers in the conduction band increases in an avalanche manner. This effect is used in avalanche transistors to produce very short pulses of high amplitude and very short rise and fall times. The known from the prior art, based on avalanche transistors circuits usually have a charge storage element, which is adapted to store an electric charge. This charge storage element is discharged at a very high speed when the avalanche transistor triggers, i. from a locked state to a conductive state.

Under a locked state of a transistor or a transistor arrangement is in the context of this application a Understood state in which the collector-emitter paths of the transistor or the collector-emitter path (s) of the transistor arrangement have a high resistance. A conducting state of a transistor or a transistor arrangement is understood to mean a state in which the collector-emitter paths of the transistor or the collector-emitter path (s) of the transistor arrangement have a very low resistance.

For example, is from the US 3,555,301 discloses a device for generating pulses with variable delay, having a plurality of avalanche transistors connected in parallel with associated charge storage elements in the form of capacitors in order to provide current pulses with a large amplitude can. It is provided that the voltage applied to the collector of the respective avalanche voltage bias is individually adjustable in order to achieve that the avalanche transistors connected in parallel triggers despite individually different breakdown voltages, ie transition from a locked state to a conductive state, if the bases of the avalanche transistors Trigger pulse is supplied.

Such pulse generators, which are based on avalanche transistors, however, have only limited suitability for generating pulses with a high repetition frequency.

This is partly due to the fact that the repetition frequency with which pulses can be generated in circuits based on avalanche transistors is limited by the speed with which the associated charge storage element (concentrated or distributed capacitance) with that necessary to generate the pulse electric charge can be charged. This charging speed is limited and therefore represents a limiting factor for the repetition frequency of the pulse generation in the known from the prior art, based on avalanche transducers pulse generators.

On the other hand, the repetition rate of the pulse generation in the avalanche transistor-based circuits known from the prior art is limited by the power dissipation of the transistors, which leads to a heating of the transistors and the associated circuit. If a maximum allowable power loss is exceeded, this can lead to damage or destruction of the transistors due to the strong heating, so that the repetition frequency of the pulse generation can not be increased arbitrarily. Although this problem can be counteracted to a limited extent by the use of heat sinks, the realizable repetition frequencies of the pulse generation, however, remain limited in practice to a few MHz in continuous operation.

A further problem in avalanche-based pulse generators known from the state of the art is that the avalanche transistors used, because of unavoidable manufacturing tolerances, also exhibit distinctly distinct properties, i. Characteristic values and characteristic curves, in particular clearly differing breakdown voltages, if the transistor type of the avalanche transistors used is identical. As a result, the parameters of the generated pulses, in particular their amplitude, pulse duration, rise and fall time, vary unpredictably depending on the generally unknown properties of the avalanche transistors used.

Based on this, it is an object of the present invention to provide a pulse generator which overcomes the disadvantages described above and with the generation of pulses, in particular voltage and / or current pulses having a high amplitude, very short pulse duration and short rise and fall times, with high repetition frequency allows.

A further object of the present invention is to provide methods for determining the breakdown voltage of bipolar transistors, in particular of avalanche transistors, as well as for selecting such transistors, with the aid of which it is possible to easily determine the breakdown voltage of the transistors used for the pulse generation, and transistors to select with matching breakdown voltages.

Another object of the present invention is to provide an imaging system that takes advantage of the pulse generator of the present invention to improve the imaging system and the imaging method thereby realized.

The first object is achieved by a pulse generator for generating pulses with high repetition frequency with the features of claim 1. Advantageous developments of the invention are described in the subclaims.

Proposed is a pulse generator for generating high repetition rate pulses comprising a pulse generating unit and a control unit. The pulse generating unit has an output terminal connectable to a load and a plurality of pulse generating sections, i. at least two pulse generation sections, on.

At least two of these pulse generating sections or each of the pulse generating sections are constructed so that the pulse generating section has a control input, to which a trigger signal can be supplied, and a charging circuit which can be connected to a supply voltage and which has at least one charge storage element arranged to store an electrical charge. In addition, the pulse generating section has a transistor arrangement connected between the charging circuit and the output terminal of the pulse generating unit. The various pulse generation sections of the pulse generator can be connected to one another, in particular, at the output terminal of the pulse generation unit. The transistor arrangement of the pulse generation section can assume a blocked and a conductive state and comprises at least one avalanche transistor.

In this case, the charging circuit is adapted to charge the charge storage element with an electrical charge when the charging circuit is connected to the supply voltage and the transistor arrangement has assumed a locked state. Moreover, the transistor device is configured to transition from the locked state to the conductive state when the trigger signal is supplied to the control input, and to provide an output pulse in the conductive state by discharging the charge storage element utilizing an avalanche effect occurring in the at least one avalanche transistor to generate at the output terminal of the pulse generating unit.

The control unit is signal-technically connected to each pulse generating section of the pulse generating unit via the control input of the pulse generating section. The control unit is set up to generate a trigger signal frequency which comprises a plurality of trigger signals offset in time with respect to one another. The control unit is further configured to supply the individual time-offset trigger signals sequentially to different pulse generation sections so that the pulse generation unit generates an output pulse sequence at its output terminal. In this case, the output pulse sequence comprises a plurality of output pulses which are offset with respect to one another and generated by different pulse generation sections. In particular, the control input of the pulse generating section to which a trigger signal may be applied may be signal connected to the base of at least one or one of the avalanche transistors of the pulse generating section to trigger the avalanche transistor or the entire transistor arrangement, i.e., the base, by driving the base. Its or its transition from the locked state to the conductive state, cause.

By means of the supply voltage connected to the charging circuit, on the one hand, the electrical charge necessary for charging the charge storage element can be provided. On the other hand, by the supply voltage connected to the charging circuit, a bias voltage can be provided at the collector of at least one or precisely one avalanche transistor of the pulse generating section, which causes the avalanche transistor to trip when its base is driven by supplying the trigger signal, i. H. when the base is triggered. The charging circuit may for this purpose be connected between the collector of the avalanche transistor to be biased and a terminal for connection to the supply voltage, i. be connected between the collector and the supply voltage.

The charge storage element may have a lumped capacitance, e.g. in the form of a capacitor, and / or a distributed capacitance, e.g. in the form of a delay line. The charge storage element is charged with an electrical charge when the charging circuit is connected to the supply voltage and the transistor arrangement has assumed a locked state.

When the control input is supplied with the trigger signal, the at least one avalanche transistor is triggered, whereby the base-emitter diode (p-n junction between base and emitter) of the at least one avalanche transistor changes from a blocked to a conductive state. By utilizing an avalanche effect occurring in the base-collector diode of the at least one avalanche transistor, a very rapid increase of the collector and emitter current flowing through the at least one avalanche current is recorded, whereby the charge storage element is discharged and an output pulse is generated at the output terminal of the pulse generation unit.

The at least one avalanche transistor of the pulse generation sections can be, for example, a bipolar transistor of the type 2N2369.

The transistor arrangement assumes the function of a discharge circuit. The transistor arrangement can therefore also be referred to as a discharge circuit.

The transistor arrangement may consist of only a single avalanche transistor in the simplest case. The transistor arrangement can also be several avalanche transistors and / or resistors and / or capacitors and / or other components.

When the supply voltage is increased beyond a certain value, self-triggering of the at least one avalanche transistor of the transistor arrangement occurs, i. the transistor arrangement transitions from the locked state to the conductive state, and the pulse generator generates pulses at the output terminal of the pulse generation unit without supplying the trigger signal to the control input. This value of the supply voltage leading to a self-tripping is referred to as a self-tripping supply voltage. In order to avoid such unwanted self-triggering of the at least one avalanche transistor and at the same time to ensure that there is a triggering of the at least one avalanche transistor when the trigger input signal is supplied to the control input, the supply voltage can advantageously be chosen so that it has a slightly lower value than the self-timer supply voltage.

The control unit of the pulse generator is signal-connected to each pulse generating section of the pulse generating unit via the control input of the respective pulse generating section to be able to supply trigger signals to each pulse generating section so that the transistor arrangement of the respective pulse generating section is triggered. The control unit generates a trigger signal sequence comprising a plurality of trigger signals offset in time with respect to one another. The individual timing signals offset in time are sequentially, i. time sequentially supplied to different pulse generating sections, so that the transistor arrangements of the various pulse generating sections are sequentially triggered. As a result, the pulse generation unit generates an output pulse sequence at its output terminal. This output pulse sequence comprises a plurality of temporally offset output pulses which are generated by different pulse generating sections connected to the output terminal.

It is thus provided according to the invention that the different pulse generation sections are sequential, i. successively in time, generate output pulses which result at the output terminal of the pulse generation unit of an output signal sequence temporally mutually offset output pulses. For example, it is conceivable that the pulse generating unit supplies the trigger signals to the various pulse generating sections so that first a pulse generating section generates an output pulse, then a second pulse generating section generates an output pulse, then a third pulse generating section generates an output pulse, etc. until the last pulse generating section Pulse generating unit generates an output pulse. Advantageously, for example, the sequence of pulse generation can then begin again at the first pulse generation section.

The invention allows the generation of pulses with large amplitude, very short pulse duration and very short rise and fall times by the use of avalanche transistors. If, for example, bipolar transistors of the type 2N2369 are used as avalanche transducers, it is easily possible with the pulse generator according to the invention to generate voltage pulses with a rise time of 2 ns, a half-width of 10 ns and an amplitude of several tens of volts as output pulses.

Moreover, a significant advantage of the invention over the prior art is that by using a plurality of pulse generating sections and sequentially driving these pulse generating sections with trigger signals (i.e., sequential triggering), it is possible to generate such pulses at a very high repetition rate.

Pulse generation is parallelized by the use of multiple pulse generation sections and their sequential control. According to the invention, the abovementioned limiting factors, namely the maximum charging speed of the charge storage elements and the maximum permissible power consumption of the avalanche transistors, can be advantageously avoided.

Namely, by using a plurality of pulse generating sections and sequentially driving them, at a given repetition frequency of pulse generation, the time between two consecutive pulse generating operations of a particular pulse generating section is multiplied, so that between two pulse generating operations of a certain pulse generating section, a longer period for charging the charge storing element of the pulse generating section Available. On the other hand, the power consumption of the avalanche transistors when using multiple pulse generating sections and their sequential control distributed to the different pulse generating sections, so that per pulse generating section results in a significantly lower power consumption. This results in less heating of the individual avalanche transistors, so that their damage or destruction can be avoided.

In this way, it is advantageously possible to realize significantly higher repetition frequencies of the pulse generation, without reaching the limits imposed by the charging rate of the charge storage elements or the power consumption of the avalanche transistors. If the pulse generation unit has, for example, eight pulse generation sections, it is easily possible with the pulse generator according to the invention, voltage pulses of the aforementioned type, ie voltage pulses with a rise time of 2 ns, a half width of 10 ns and an amplitude of several tens of volts, with a repetition frequency of 25 MHz to produce.

Another advantage of the pulse generator according to the invention lies in its theoretically unlimited scalability. In order to realize higher repetition frequencies of the pulse generation, the number of pulse generation sections of the pulse generator can theoretically be arbitrarily increased.

In an advantageous development of the invention, the pulse generator may comprise at least one cooling unit, which is adapted to cool the pulse generator. Such a cooling unit may, for example, be a fan, i. a cooling fan. The fan may, for example, be arranged above the pulse generation sections, in particular via the transistor arrangements.

Such a cooling unit offers the advantage that an inadmissibly high heating of the avalanche transistors can be avoided and in this way ceteris paribus can be realized greater repetition frequencies of the pulse generation.

In a further advantageous development of the invention, the pulse generation unit has no heat sink connected to the transistor arrangements of the pulse generation sections. Such a heat sink can basically be used as a heat sink to counteract the heating of the transistor arrangements. However, it is advantageous to dispense with such a heat sink, since in this way the parasitic capacitances at the transistor terminals can be reduced.

In a further advantageous embodiment of the invention, it is provided that the control unit is set up to sequentially and cyclically supply the different pulse generation sections to the trigger signals offset in time. In this case, at least one trigger signal is supplied to each pulse generation section in each cycle. Advantageously, the same number of trigger signals can be supplied to each pulse generation section, in particular in each cycle. Advantageously, in each cycle, exactly one trigger signal can be supplied to each pulse generation section in particular.

It is thus proposed that the sequence of pulse generation by the individual pulse generation sections repeats cyclically. For example, if the pulse generator has N pulse generating sections, the output pulses generated at the output terminal of the pulse generating unit can be generated by the various pulse generating sections, for example, in the following sequence: Pulse generating section 1 , Pulse generation section 2 , Pulse generation section 3 , ..., pulse generation section N, pulse generation section 1 , Pulse generation section 2 etc.

Such cyclical supply of the trigger signals to the pulse generating sections thus causes cyclic generation of the output pulses by the various pulse generating sections. This offers the advantage that with a limited number of pulse generation sections an infinitely long output pulse sequence can be generated. Moreover, the intended even distribution of the trigger signals to the various pulse generating sections offers the advantage that the load of the pulse generation, in particular the associated power consumption of the avalanche transistors and the time required for charging the charge storage elements, is equally distributed among the various pulse generating sections, so that their Performance can be optimally utilized.

In a further advantageous embodiment of the invention, it is provided that the pulse generation sections are connected in parallel to each other.

Such a parallel connection of the pulse generation sections may, for example, be effected in that the pulse generation sections are connected in parallel between a supply voltage connection, via which the charging circuit can be connected to the supply voltage, and the output connection of the pulse generation unit.

Such a parallel connection of the pulse generating sections offers the advantage that, with a comparatively simple circuit structure, the parallelization of the pulse generation in the sense of the present invention, i. the use of multiple pulse generating sections and their sequential control by the control unit, can be realized.

In a further advantageous embodiment of the invention it is provided that the charge storage element comprises a capacitor. In a simple embodiment of the invention the charge storage element in particular consist of a single capacitor.

Such a realization of the charge storage element as a capacitor offers the advantage of a compact design and advantageously allows the generation of short, needle-shaped output pulses by a rapid discharge of the capacitor.

In a further advantageous embodiment of the invention it is provided that the charge storage element comprises a delay line (delay line). The charge storage element may in particular comprise a line section of an electrical line. In particular, the charge storage element may comprise a line section of a coaxial line, a line section of a strip line and / or a line section of another electrical waveguide.

In a simple embodiment of this development of the invention, the charge storage element consists only of a single delay line of the type mentioned.

The line section of the respective type in each case has the function of an electrical energy store.

The line section also has the function of a delay line (delay line), which is also referred to as a delay line. The line section of the electrical line can therefore also be referred to as a delay line, delay line or delay line.

The line section of the electrical line may in particular be a line section open at the end, for example a coaxial line section open at the end or a stripline section open at the end.

Such an embodiment of the pulse generator according to the invention, in which the charge storage element comprises a delay line or consists of a delay line, offers the advantage that in this way the generation of output pulses with a defined pulse duration, in particular the generation of rectangular output pulses with a defined pulse duration, is possible , The pulse duration is determined by the length of the delay line and the propagation speed of the electromagnetic wave on the delay line.

In a further advantageous development of the invention, it is provided that the pulse generation sections each have a drive circuit connected between the control input and the transistor arrangement for driving the transistor arrangement.

The drive circuit can have a terminating resistor. The terminating resistor terminates a connecting line, via which the control unit is signal-connected to the control input of the pulse-generating section, with the line-wave resistance of this connecting line. This offers the advantage that a reflection of the trigger signal supplied to the control input by the control unit can be avoided.

Alternatively or additionally, the drive circuit may have a coupling capacitor, which produces a capacitive coupling between the control input and the transistor arrangement. This offers the advantage that the unwanted transmission of a DC component from the control unit to the pulse generating section can be prevented.

Alternatively or additionally, the drive circuit may have a signal transformer, which separates the control input galvanically from the transistor arrangement. This offers the advantage that the electromagnetic compatibility of the pulse generator can be improved because electromagnetic interference caused by common impedances of the pulse generation section with the control unit can be reduced.

In a further advantageous development of the invention, the charging circuit has a charging resistor, which is connected between a supply voltage connection, via which the charging circuit can be connected to the supply voltage, and the transistor arrangement. With such a charging resistor can be adjusted by an appropriate dimensioning advantageously the current intensity of the current with which the charge storage element is charged to an appropriate value. In addition, can be advantageously prevented by the charging resistor, that it comes to a self-triggering of the at least one avalanche transistor of the transistor arrangement by the collector current is limited by the charging resistor.

The pulse generator may in particular comprise input means with which the control unit of the pulse generator can be programmed and / or configured.

In an advantageous development of the invention, it is provided that the input means of the pulse generator are galvanically isolated from the other components of the pulse generator, in particular from the control unit and the pulse generation unit. The input means can do this For example, by an optocoupler, in particular a digital optocoupler, and / or be isolated by a capacitive coupling and / or by an inductive coupling. Such galvanic isolation offers the advantage that interference can be reduced and the electromagnetic compatibility of the pulse generator can be improved.

In a further advantageous embodiment of the invention, it is provided that the transistor arrangement has a series connection of avalanche transistors and / or a parallel connection of avalanche transistors and / or a Marx circuit constructed from avalanche transistors.

A series connection of several avalanche transistors offers the advantage that the total breakdown voltage of the transistor arrangement can be increased, since the serially connected avalanche transistors form a voltage divider. As a result, it is advantageously possible to generate pulses having a greater amplitude, in particular voltage pulses having a greater amplitude, at the output terminal of the pulse generation unit.

Similarly, parallel connection of several avalanche transistors can advantageously bring about an increase in the current intensity delivered by the pulse generation section and thus also an increase in the amplitude of the output pulses generated at the output terminal of the pulse generation unit.

By virtue of a Marx circuit constructed from a plurality of avalanche transistors, it is advantageously possible to utilize the advantages of the above-described series connection of several avalanche transistors and in this way to generate output pulses with a greater amplitude. The Marx circuit offers the advantage over the series circuit that it requires a lower supply voltage for charging the charge storage elements.

In a further advantageous embodiment of the invention it is provided that the pulse generation sections are identical to each other. The pulse generation sections may in particular have an identical structure and / or components of the same type.

Such an embodiment of the pulse generator according to the invention, in which the pulse generation sections are identical to one another, has the advantage that the output pulses generated by the different pulse generation sections have essentially the same properties, in particular substantially equal amplitudes, pulse durations, rise and fall times. Furthermore, this embodiment facilitates the generation of output pulses at uniform time intervals at the output terminal of the pulse generation unit. In addition, this embodiment offers the advantage that a pulse generator with a particularly simple circuit structure and resulting low production costs can be provided.

In a further advantageous development of the invention, it is provided that the pulse generation unit has at least four or at least six or at least eight or at least ten or at least twelve or at least 16 or at least 20 or at least 100 pulse generating sections. A higher number of pulse generating sections offers the advantage that a particularly high repetition frequency of the pulse generation can be realized.

In a further advantageous embodiment of the invention, it is provided that the trigger signal is a trigger pulse. The trigger pulse may in particular be a voltage pulse. The trigger pulse may in particular be a rectangular voltage pulse. Such a form of trigger signal has the advantage that the trigger signal can be provided in a particularly simple manner, for example by means of an FPGA or a simple signal generator.

In a further advantageous embodiment of the invention it is provided that the pulse generation unit has a load resistor connected to the output terminal, via which a voltage pulse can be tapped as an output pulse. This offers the advantage that voltage pulses can be provided in a simple manner at the output terminal, as are required for a large number of applications, for example for controlling image intensifiers.

In a further advantageous embodiment of the invention, it is provided that the control unit has a synchronization input and the control unit is set up to synchronize the generation of the trigger signals of the trigger signal frequency to a reference signal supplied to the synchronization input. The reference signal may in particular be a high-frequency reference signal (RF reference signal).

Such synchronization of the control unit can e.g. realized by a clock recovery circuit which converts an RF reference signal into a digital signal, for example. A CMOS digital signal, which can be used as a clock input signal (clock input signal) for generating the trigger signals in the control unit.

Such a possibility of synchronizing the control unit to a reference signal offers the advantage that it allows the use of the pulse generator to investigate repetitive dynamic processes. If, for example, the pulse generator is used to drive an image intensifier as part of an imaging system, the time gating of the image intensifier reduces the number of photons detected per unit of time. For this reason, multiple gating cycles may be necessary to produce images of sufficient quality. The synchronization of the control unit of the pulse generator to a reference signal advantageously allows a synchronization of the gate input of the image intensifier supplied pulses (so-called gating pulses) to the external reference signal. In this way, it is possible to generate images from multiple gating cycles by capturing in-phase images of the repeating dynamic process in various iterations of the process, thereby accumulating the detected intensities of light. This is particularly advantageous when images of objects or processes are to be detected, which generate very low light intensities or light intensities.

In a further advantageous embodiment of the invention, it is provided that the control unit has a configurable delay element with which the phase shift between the reference signal and the trigger signals of the trigger signal sequence can be configured. For example, in the use of the pulse generator in conjunction with an imaging system, this provides the advantage of enabling the acquisition of static images representing different phases of the temporal evolution of an observed dynamic process, i. Various phases of the dynamic process may be detected by the imaging system by driving the imaging system with a correspondingly configured delay of the pulse generator.

In a further advantageous embodiment of the invention, it is provided that the avalanche transistors of the various pulse generation sections have matching electrical parameters, in particular matching breakdown voltages. This offers the advantage that in this way the generation of an output pulse sequence is possible which has output pulses with uniform time intervals and / or output pulses having a particularly uniform appearance, d. H. Output pulses having highly consistent characteristics (e.g., amplitude, pulse duration, rise and fall times).

In a further advantageous embodiment of the invention, it is provided that the supply voltages of the pulse generating sections are different. Alternatively or additionally, the supply voltages of the pulse generation sections can be configured independently of each other. Alternatively or additionally, the supply voltages of the pulse generation sections can each be adapted to a breakdown voltage of the at least one avalanche transistor of the respective pulse generation section.

These advantageous developments of the pulse generator according to the invention have the advantage that individually different electrical parameters, in particular individually different breakdown voltages, of the avalanche transistors of the different pulse generation sections can be compensated by the different or configurable or adjusted supply voltages. Thus, in spite of different electrical parameters of the avalanche transistors of the various pulse generating sections, it is advantageously possible to produce an output pulse sequence of output pulses with uniform time intervals and a uniform appearance in terms of their properties, i.e., their output characteristics. in particular amplitude, pulse duration, rise and fall times of the pulses to bring about.

In a further advantageous embodiment of the invention, it is provided that the control unit has an FPGA. This offers the advantage that, due to the versatility of an FPGA, different functionalities of the control unit can be implemented in the FPGA. These include, for example, the generation of a clock signal (clock), the provision of fixed and adjustable delays and the generation of the trigger signals, for example in the form of trigger pulses.

In a further advantageous embodiment of the invention it is provided that the pulse generator is adapted to generate the output pulses of the output pulse sequence with a repetition frequency of at least 10 MHz or at least 20 MHz or at least 25 MHz. This offers the advantage that the pulse generator can also be used for applications which require the provision of pulse sequences with a particularly high repetition frequency.

The second object mentioned above is achieved by a test method for determining a breakdown voltage of a bipolar transistor having the features of patent claim 18. The bipolar transistor may in particular be a avalanche transistor.

In step a) of the test method according to the invention, a test circuit is provided.

The test circuit has a base terminal connectable to the base of the bipolar transistor, a collector terminal connectable to the collector of the bipolar transistor, and an emitter terminal connectable to the emitter of the bipolar transistor.

The test circuit further includes an adjustable voltage source that provides an adjustable test voltage.

Furthermore, the test circuit has a charging circuit connected between the collector terminal and the adjustable voltage source. In this case, the charging circuit has at least one charge storage element configured to store an electrical charge, which can be charged with an electrical charge provided by the adjustable voltage source.

The test circuit also has a load resistor arrangement connected to the emitter terminal, which comprises at least one load resistor.

The test circuit furthermore has a drive circuit connected to the base terminal. The drive circuit in this case has a signal generator and is set up such that a sequence of trigger signals generated by the signal generator is supplied to the base terminal. The trigger signals have the form of voltage pulses.

The test circuit further comprises a voltage measuring device, which is set up to measure and display the time profile of an output voltage drop across the load resistor arrangement. Such a voltage measuring device can be, for example, an oscilloscope.

In step b) of the test method according to the invention it is provided that a bipolar transistor to be tested is provided. The bipolar transistor to be tested may in particular be a avalanche transistor.

In step c) of the test method according to the invention, it is provided that the bipolar transistor to be tested is connected to the test circuit. In this case, the base of the bipolar transistor is connected to the base terminal of the test circuit, the emitter of the bipolar transistor to the emitter terminal of the test circuit and the collector of the bipolar transistor to the collector terminal of the test circuit.

In step d) of the test method according to the invention, it is provided that the adjustable test voltage, which is supplied by the adjustable voltage source, is increased until the voltage measuring device displays a stable voltage pulse sequence as a time profile of the output voltage.

A continuous voltage pulse sequence is understood to be a sequence of voltage pulses which have a constant amplitude, a voltage pulse being generated for each trigger signal supplied to the base terminal. A constant amplitude of the voltage pulses can be defined, for example, by limiting values. For example. For example, the amplitude of the voltage pulses may be considered constant if the amplitude of the voltage pulses varies less than ± 0.4 V and / or less than ± 1%.

During the test procedure, the drive circuit continuously supplies to the base terminal the sequence of voltage pulses generated by the signal generator. As a result, the bipolar transistor to be tested connected to the base terminal is triggered at regular intervals.

If the voltage measuring device indicates a stable voltage pulse sequence, then it can be deduced that the bipolar transistor to be tested triggers at regular intervals as a result of the trigger signals applied to its base, i. from a locked state to a conductive state, thereby generating voltage pulses on the load resistor array at regular intervals.

The persistent voltage pulse sequence thus indicates that the set test voltage is sufficiently large to cause the bipolar transistor to trip when its base is triggered by the trigger signal. At the same time, the persistent voltage pulse train indicates that the set test voltage is not so high that self-triggering of the bipolar transistor under test, i. triggering without supplying a trigger signal, is brought about. The set test voltage is therefore suitable for bringing about a transition of the bipolar transistor from the locked state to the conductive state in the manner desired for use of the bipolar transistor in a pulse generator when the trigger signal is supplied to the base of the bipolar transistor to be tested.

In step e) of the test method according to the invention, therefore, the last set test voltage is determined as the breakdown voltage of the bipolar transistor to be tested. The breakdown voltage of the to be tested bipolar transistor thus results as the last set test voltage.

As already explained, the bipolar transistors used for pulse generators, in particular avalanche transients, can also have distinctly different properties, i.e., differing production tolerances, which are difficult to avoid. Characteristics and characteristics, have, if the transistor type of the transistors used is identical. As a result, the characteristics of the pulses generated by these transistors vary unpredictably.

The test method according to the invention therefore offers the advantage that it enables a determination of the breakdown voltage of the bipolar transistor to be tested so that the parameters of the pulse generator, in particular the value of the supply voltage and the amplitude of the trigger pulses, can be adapted to the breakdown voltage of the transistor determined by means of the test method , In addition, it is advantageously possible with the aid of the test method according to the invention to select from a set of bipolar transistors, in particular avalanche transistors, those transistors which have matching breakdown voltages, or at least to sort out those transistors whose breakdown voltage deviates significantly from the breakdown voltage of the other transistors.

Advantageously, the test method according to the invention can thus be used in particular to determine the breakdown voltage of avalanche transistors of a pulse generator, in particular of a pulse generator according to the invention of the type described above.

The aforementioned second object is further achieved by a selection method for selecting bipolar transistors having matching breakdown voltages. The bipolar transistors may be avalanche transistors in particular.

In a first step of the selection method according to the invention, provision is made for a number of bipolar transistors of the same type to be tested to be provided. In particular, the bipolar transistors may be avalanche transistors of the same type. The bipolar transistors can be, for example, avalanche transistors of the type 2N2369.

In a further step of the selection method according to the invention, it is provided that the breakdown voltage of each bipolar transistor to be tested is determined by a test method of the type described above.

In a further step of the selection method according to the invention, it is provided that those bipolar transistors are selected for which matching breakdown voltages have been determined in the step described above.

The selection method according to the invention offers the advantageous possibility that for a pulse generator, in particular for a pulse generator of the type described above, avalanche transistors with matching breakdown voltages can be selected. As a result, it is advantageously possible to avoid negative effects on the generation of pulses that result from the fact that the avalanche transistors used in the pulse generator have different breakdown voltages due to manufacturing tolerances. If the avalanche transistors of the pulse generator are selected with the selection method according to the invention, it is advantageously possible to use the pulse generator to generate an output pulse sequence whose output pulses have uniform time intervals and / or a particularly uniform appearance, i. have highly consistent properties (e.g., amplitude, pulse duration, rise and fall times).

Advantageously, the selection method according to the invention can therefore be used to select avalanche transistors with matching breakdown voltages for an avalanche-based pulse generator, in particular for a pulse generator according to the invention of the type described above.

In a further advantageous development of the pulse generator according to the invention described above, it is therefore provided that the avalanche transistors of the various pulse generation sections of the pulse generation unit of the pulse generator have matching breakdown voltages and have been selected by a selection method according to the invention of the type described above.

With regard to the advantages of such a development of the pulse generator according to the invention can be made to the above statements on the advantages of the test method according to the invention and the selection method according to the invention.

The third mentioned object is achieved by an imaging system having the features of claim 21. The imaging system comprises a pulse generator according to the invention of the type described above and an image intensifier with a controllable gain time window.

The gain time window of the image intensifier is the time window within which the image intensifier amplifies the optical signal received at its input. The optical signal received at the input of the image intensifier can have the form of light, ie the form of photons, which impinges on a photocathode of the image intensifier.

The image intensifier of the imaging system according to the invention has at least one gate input. The gain time window of the image intensifier can be controlled via a voltage applied to the gate input. Accordingly, the gain time window of the image intensifier can be controlled in particular by supplying a voltage pulse to the gate input. This technique is called time gating.

The output terminal of the pulse generating unit of the pulse generator of the imaging system according to the invention is connected to the gate input of the image intensifier to supply output pulses generated by the pulse generator to the image intensifier and thereby control the gain window of the image intensifier in the manner previously described.

The length of the amplification time window is determined by the pulse duration of the output pulses generated by the pulse generator. A short pulse duration therefore allows the generation of images with a particularly high temporal resolution. This is particularly relevant for the use of imaging processes in connection with dynamic processes.

The rise and fall times of the output pulses generated by the pulse generator that are applied to the image intensifier must be significantly shorter than the pulse duration to ensure that the resulting gain window has a clearly defined length.

The repetition rate at which the pulse generator generates the output pulses applied to the image intensifier determines the total acquisition time necessary to capture an image of a repeating dynamic process over a plurality of gating cycles. The higher the repetition frequency of the pulse generation of the pulse generator, the lower the required total acquisition time.

The imaging system according to the invention has a pulse generator according to the invention, which, as already explained above, allows the generation of output pulses of large amplitude with very short rise time, very low pulse duration and very high repetition frequency. The imaging system according to the invention therefore offers the advantage that images with high temporal resolution and clearly defined amplification time windows can be generated with a low total acquisition time.

Ideally, the repetition rate of the pulse generation corresponds to an excitation frequency that is used to excite a physical process so that the pulse generator generates an output pulse per period of excitation of the physical process. With the imaging system according to the invention, it is possible to realize this ideal case also for physical processes that are excited with a very high excitation frequency.

The imaging system according to the invention therefore offers considerable advantages with regard to the necessary total acquisition time, in particular when images of objects or processes are to be acquired which generate very low light intensities or light intensities. Such applications include, for example, the imaging of trapped ions in an ion trap, the resolution of small concentrations of fluorescent labels, the recovery of information from highly attenuated optical signals, or imaging in dimly lit scenes.

In an advantageous development of the imaging system according to the invention, it is provided that the gate input of the image intensifier is subjected to an inverse bias voltage. The inverse bias voltage is a bias voltage having an inverse sign compared to the voltage of the voltage pulse applied to the image intensifier from the pulse generator for controlling the boost time window. For example, if the gain window of the image intensifier is controlled by a negative voltage pulse (i.e., the image intensifier is amplified when a negative voltage is applied to its gate input), then the inverted bias has a positive sign. Conversely, if the gain window of the image intensifier is controlled by a positive voltage pulse (i.e., the image intensifier is amplified when a positive voltage is applied to its gate input), the inverted bias has a negative sign.

Such loading of the gate input of the image intensifier with an inverted bias voltage has the advantage that capacitive effects of the image intensifier which result in a reduced edge steepness of the falling edge of the output pulse supplied by the pulse generator to the image amplifier can be counteracted. As a result, it is advantageously possible to improve the temporal resolution of the imaging system.

In an advantageous development of the imaging system according to the invention it is provided that the pulse generator of the imaging system is a pulse generator of the type described above, the control unit has a synchronization input, wherein the control unit is adapted to synchronize the generation of the trigger signals of the trigger signal frequency to a reference signal, which is supplied to the synchronization input. The reference signal may in particular be a high-frequency reference signal. In particular, the reference signal may be a periodic electrical signal, for example in the form of a sinusoidal signal or a pulse train.

In addition, the imaging system in this advantageous development, a reference signal source, which generates a reference signal.

In addition, the imaging system in this advantageous development, a driver unit which is adapted to stimulate a physical process and / or a physical object for generating a primary optical signal in response to the reference signal. The driver unit can be, for example, an electrical power amplifier or a light source, for example a laser. The driver unit serves as a means for conditioning between the reference signal source and the physical process or the physical object. In this case, the physical process and / or the physical object is a process or an object that generates an optical signal (the primary optical signal) in response to an excitation, which can take place, for example, in the form of an electrical or optical signal.

For this purpose, the reference signal source is signal-connected to the driver unit in order to supply the reference signal to the driver unit.

Furthermore, in this advantageous development of the imaging system according to the invention, the reference signal source is signal-technically connected to the synchronization input of the control unit of the pulse generator in order to supply the reference signal to the control unit. This ensures that the generation of pulses by the pulse generator can be synchronized with the excitation of the physical process or of the physical object.

In addition, in this advantageous development of the imaging system according to the invention, the image intensifier is set up to amplify the primary optical signal within the amplification time window to a secondary optical signal as a function of the output pulses supplied to the image intensifier by the pulse generator. The gain window of the image intensifier is thus controlled in the manner described above (time gating) by the output pulses generated by the pulse generator.

Furthermore, the imaging system in this advantageous development, a camera which is adapted to detect the secondary optical signal and to generate an image thereof. The camera can in particular serve to cumulate the photons detected in several gating cycles and thus the light intensities detected in several gating cycles over the image acquisition time of the camera, i. to integrate over time.

The optical amplification of the image intensifier serves, in particular, to overcome a limitation of its photosensitivity caused by the background noise of the camera. This is particularly advantageous in applications which have particularly low light intensities down to the region of individual photons.

By synchronizing both the pulse generator and the physical process excitation to the same reference signal, the gain window of the image intensifier can be synchronized with the timing of the physical process.

Moreover, it is advantageously possible with the imaging system according to the invention to delay the generation of the output pulses by the pulse generation unit of the pulse generator by a delay of defined length by a configurable delay element of the control unit of the pulse generator is configured accordingly. As a result, it is advantageously possible to bring about a defined phase shift between the excitation of the physical process or of the physical object and the output pulses supplied to the image intensifier. By configuring different delays, multiple static images can be generated that represent different phases of a temporal development of a dynamic physical process or of a dynamic behavior of a physical object.

In this way it is possible, for example with the aid of the imaging system according to the invention, to generate images which contain information about the movement of trapped ions in an ion trap. In another example of application, information about the concentration of a specific fluorescent label in a sample or in a biological tissue can be obtained by fluorescence lifetime imaging.

The information obtained via the dynamics of the process is not contained in a single image, but rather in the difference between at least two images which were generated at different times in relation to the time difference predetermined by the reference signal.

• 1 eine schematische Darstellung eines erfindungsgemäßen Impulsgenerators mit einer Impulserzeugungseinheit und einer Steuereinheit;
• 2 eine schematische Darstellung zeitlich zueinander versetzter Triggersignale;
• 3 ein schematisches Schaltbild eines Impulserzeugungsabschnitts;
• 4 ein schematisches Schaltbild einer Impulserzeugungseinheit mit zueinander parallel geschalteten Impulserzeugungsabschnitten;
• 5 ein schematisches Schaltbild einer Testschaltung zur Durchführung der erfindungsgemäßen Prüf- und Auswahlverfahren;
• 6 eine schematische Darstellung eines erfindungsgemäßen bildgebenden Systems.

The invention will be explained in more detail below with reference to the embodiments schematically illustrated in the accompanying drawings. Show it:

• 1 a schematic representation of a pulse generator according to the invention with a pulse generating unit and a control unit;
• 2 a schematic representation of time-staggered trigger signals;
• 3 a schematic diagram of a pulse generating section;
• 4 a schematic circuit diagram of a pulse generating unit with mutually parallel pulse generating sections;
• 5 a schematic circuit diagram of a test circuit for carrying out the testing and selection method according to the invention;
• 6 a schematic representation of an imaging system according to the invention.

The 1 shows a schematic representation of an embodiment of a pulse generator according to the invention 1 , The pulse generator 1 has a pulse generation unit 2 and a control unit 3 on. The pulse generation unit 2 has an output terminal connectable to a load OUT and a plurality of pulse generating sections 4 on. In this embodiment, the pulse generating unit 2 a total of four pulse generation sections 4 on, which are identical to each other.

Each pulse generation section 4 each has a control input IN on which a trigger signal TS1 . TS2 . TS3 . TS4 can be supplied.

The control unit 3 has an FPGA 9 on. The FPGA 9 implements various functionalities of the control unit 3 including the generation of a clock signal (Clock), the provision of a configurable delay element and the generation of the trigger signals TS1 . TS2 . TS3 . TS4 , which are realized in this embodiment as trigger pulses in the form of rectangular voltage pulses.

The control unit 3 is with each pulse generation section 4 the pulse generation unit 2 via the respective control input IN of the pulse generation section 4 connected by signal technology. The control unit 3 is further configured to have a trigger signal frequency that is a plurality of timing signals offset in time TS1 . TS2 . TS3 . TS4 includes generating. Furthermore, the control unit 3 adapted to the individual time-offset trigger signals TS1 . TS2 . TS3 . TS4 sequentially, ie temporally successively, the different pulse generation sections 4 so that the pulse generating unit 2 at its output terminal OUT generates an output pulse sequence having a plurality of time offset and different pulse generating sections 4 generated output pulses.

The control unit 3 of the pulse generator 1 also has a sync input 8th and is set up to generate the trigger signals TS1 . TS2 . TS3 . TS4 the trigger signal sequence to a synchronization input 8th to synchronize supplied high-frequency reference signal.

With the help of the FPGA 9 the control unit 3 implemented configurable delay element, a phase shift between the reference signal and the carrier signals TS1 . TS2 . TS3 . TS4 the carrier signal sequence are configured.

The 2 schematically shows the four carrier signals TS1 . TS2 . TS3 . TS4 in the form of rectangular voltage pulses of the voltage U (t). Here is the carrier signal TS1 the carrier signal corresponding to the first pulse generation section 4 is supplied, the carrier signal TS2 the carrier signal supplied to the second pulse generating section is the carrier signal TS3 is the carrier signal supplied to the third pulse generation section and the carrier signal TS4 is the carrier signal corresponding to the fourth pulse generation section of the pulse generation unit 2 of the pulse generator 1 is supplied.

By the respective carrier signal is the respective pulse generating section 4 triggered, ie the transistor arrangement of the pulse generating section 4 goes from a locked state to a conductive state, so that an output pulse is generated. The triggering takes place with the rising edge of the rectangular voltage pulse, which is the trigger signal TS1 . TS2 . TS3 . TS4 forms.

The presentation of the 2 lets recognize that the trigger signals TS1 . TS2 . TS3 . TS4 are temporally offset from each other and the various pulse generating sections 4 sequentially, ie sequentially, from the control unit 3 supplied become. The temporally offset trigger signals TS1 . TS2 . TS3 . TS4 become the different pulse generation sections 4 In addition, in this embodiment, each of the four pulse generating sections is supplied cyclically in this cycle 4 exactly one trigger signal is supplied.

The four pulse generation sections 4 are thereby triggered sequentially and cyclically, so that that of the pulse generator 1 generated output pulses sequentially and cyclically from the various pulse generating sections 4 be generated. This happens in the in 2 in the following sequence: first pulse generating section, second pulse generating section, third pulse generating section, fourth pulse generating section, first pulse generating section, second pulse generating section, etc.

The 3 shows a schematic diagram of an embodiment of a pulse generating section 4 the pulse generation unit 2 of the pulse generator 1 ,

The pulse generation section 4 has a control input IN, to which a trigger signal TS can be supplied.

In addition, the pulse generation section 4 a charging circuit 5 which is connectable to a supply potential + Vs of a supply voltage via a supply voltage terminal and which has a charge storage element TL arranged to store an electric charge. The charge storage element TL consists of a delay line in the form of a line section of a coaxial line. The coaxial line is in this embodiment of the type RG- 58 and the line section of the coaxial line has a length of 90 cm. By the delay line is advantageously the generation of rectangular output pulses with a defined pulse duration, which is determined by the length of the delay line TL and the propagation velocity of the electromagnetic wave on the delay line TL, possible.

The charging circuit 5 moreover, one between the supply voltage terminal and the transistor arrangement 6 switched charging resistor R1 via which the charge storage element TL is charged. The charging resistance R1 may for example have a value of 2 kΩ. By the charging resistance R1 The current value of the current with which the charge storage element TL is charged is set to an appropriate value. In addition, the charging resistance limits R1 the collector current flowing into the collector of the avalanche transistor T1 flows, thus preventing it from self-triggering the avalanche transistor T1 comes.

The charging circuit 5 also has a filter capacitor C1 on, the positive supply voltage close to the charging resistor R1 filters and thus serves to improve the electromagnetic compatibility and interference, especially crosstalk, between different pulse generating sections 4 via one of the various pulse generation sections 4 to avoid common supply voltage line. The filter capacitor C1 is connected for this purpose between the supply voltage terminal, to which the supply potential + Vs is applied, and a reference potential terminal GND, to which a reference potential is applied.

The pulse generation section 4 also has a between the charging circuit 5 and the output terminal OUT the pulse generation unit 2 switched transistor arrangement 6 on. The transistor arrangement 6 consists of a series connection of two avalanche transistors T1 and T2 which are npn bipolar transistors. The avalanche transistors T1 . T2 are of the type 2N2369 in this embodiment. The transistor arrangement 6 may assume a locked state and a conductive state. In the locked state of the transistor arrangement 6 have the collector-emitter paths of both avalanche transistors T1 . T2 a high resistance. In the conducting state of the transistor arrangement 6 have the collector-emitter paths of both avalanche transistors T1 . T2 a very low resistance, so that a fast discharge of the charge storage element TL is possible. A triggering of the avalanche transistor T1 also causes a triggering of the avalanche transistor T2 so that the transistor arrangement 6 in total triggers, that is, from the locked to the conducting state, when the transistor T1 triggers.

The charging circuit 5 is configured to charge the charge storage element TL with an electric charge when the charging circuit 5 is connected to the supply voltage, ie to the supply potential + Vs, and the transistor arrangement 6 has taken a locked state. In the locked state of the transistor arrangement 6 namely, only a very small current flows through the transistor arrangement 6 , so no significant charge transport across the transistor array 6 takes place and the charge storage element TL can be charged by the supply voltage.

The transistor arrangement 6 is arranged to go from the locked state to the conductive state, ie to trigger when the control input IN the trigger signal TS is supplied, and in the conductive state by discharging the charge storage element TL an output pulse at the output terminal OUT the pulse generation unit 2 to create. It will be in the avalanche transistors T1 . T2 exploited occurring avalanche effects, which is a particularly rapid discharge of the charge storage element TL allow. This makes it possible to generate output pulses with large amplitude, very short pulse duration and very short rise and fall times.

The 3 further indicates that the pulse generation unit 2 whose component is the pulse generation section shown 4 is one with the output terminal OUT the pulse generation unit 2 connected load resistor RL having. About the load resistance RL a voltage pulse can be tapped as output pulse. The load resistance RL is for this purpose between the emitter of the avalanche transistor T2 and the reference potential terminal GND connected.

This in 3 shown embodiment of a pulse generating section 4 moreover, one between the control input IN and the transistor arrangement 6 switched drive circuit 7 for driving the transistor arrangement 6 on. The drive circuit 7 has a terminating resistor R2 on, the one connecting line through which the control unit 3 with the control input IN of the pulse generation section 4 is connected by signal technology, with the line impedance of the connecting line terminates. The terminator R2 has a value of 200 Ω in this embodiment. The drive circuit 7 also has a coupling capacitor C2 on, a capacitive coupling between the control input IN and the transistor arrangement 6 manufactures. The coupling capacitor C2 has a capacity of 10 nF in this embodiment.

The drive circuit 7 also has a signal transformer TR1 on. The signal transformer TR1 disconnects the control input IN galvanic from the transistor arrangement 6 ,

The supply voltage, ie the potential difference between the supply potential + Vs and the reference potential connection GND , is preferably between 100 V and 110 V. The voltage of the trigger signals TS serving voltage pulses can be between 1.3 V and 3.5 V. Preferably, the voltage of the voltage pulses serving as trigger signals is approximately 2 V.

With the in 3 As shown in the embodiment of a pulse generating section, it is possible to generate as output pulses voltage pulses having a rise time of 2 ns, a half width of 10 ns and an amplitude of several tens of volts.

The 4 shows a schematic diagram of an embodiment of a pulse generating unit 2 , a total of four pulse generation sections 4 having. The individual pulse generation sections 4 correspond to the in the 3 shown embodiment. The four pulse generation sections 4 are therefore identical to each other. They have both an identical structure and identical components, ie components of the same type on.

That in the 4 In addition, the embodiment shown in FIG. 1 shows that the four pulse-generating sections 4 are connected in parallel to each other. The parallel connection of the pulse generation sections 4 is thereby realized that the pulse generation sections 4 between a common supply voltage terminal to which the supply potential + Vs is applied, and the output terminal OUT the pulse generation unit 2 are connected in parallel. This makes it possible in a particularly simple manner to parallelize the pulse generation in the sense of the present invention, ie the use of several pulse generation sections 4 and their sequential control by the control unit 2 , realize.

All four transistor arrangements 6 of the four pulse generation sections 4 are between the charging circuit 5 of the respective pulse generation section 4 and the output terminal OUT the pulse generation unit 2 connected. For this purpose, the emitters of the avalanche transistors T2 the transistor arrangements 6 in a common connection point with the output terminal OUT the pulse generation unit 2 connected. Above that with the output terminal OUT connected load resistor RL can voltage pulses as from the pulse generating sections 4 generated output pulses are tapped.

Because the control unit 3 of the pulse generator 1 the individual time-offset trigger signals TS1 . TS2 . TS3 . TS4 the four different pulse generation sections 4 sequentially, generates the pulse generation unit 2 at its output terminal OUT an output pulse sequence having a plurality of time-shifted and different pulse generating sections 4 generated output pulses in the form of voltage pulses.

With the in 4 shown embodiment of a pulse generating unit 2 , the four pulse generation sections 4 has, it is possible to voltage pulses with the aforementioned Characteristics (rise time of 2 ns, half width of 10 ns and amplitude of several 10 V) with a repetition frequency of 12.5 MHz. The number of pulse generation sections 4 the pulse generation unit 2 increases from four to eight, the realizable repetition frequency increases to 25 MHz. The realizable repetition frequency of the pulse generation thus scales linearly with the number of pulse generation sections. This makes it advantageous to realize a pulse generation with very high repetition frequencies possible.

The 5 shows a schematic diagram of an embodiment of a test circuit 10 for carrying out the test method according to the invention for determining a breakdown voltage of a bipolar transistor and for carrying out the inventive selection method for selecting matching breakdown voltages having bipolar transistors.

The test circuit 10 has one with the base of the bipolar transistor T3 connectable basic connection 11 one with the collector of the bipolar transistor T3 connectable collector connection 12 and one with the emitter of the bipolar transistor T3 connectable emitter terminal 13 on. The bipolar transistor to be tested T3 which is a type 2N2369 avalanche transistor in this embodiment is disclosed in US Pat 5 shown embodiment already connected to the test circuit.

In addition, the test circuit points 10 an adjustable voltage source 14 which provides an adjustable test voltage Ut.

Between the collector connection 12 and the adjustable voltage source 14 is a charging circuit 19 connected. The charging circuit 19 has a charge storage element configured to store an electrical charge C3 in the form of a capacitor connected to one of the adjustable voltage source 14 provided electric charge is rechargeable. The charge storage element C3 is doing about the charging resistance R3 and R4 between the charge storage element C3 and the adjustable voltage source 14 are switched, loaded. The charging circuit 19 also has a filter capacitor C5 on, which serves to improve the electromagnetic compatibility by the voltage source 14 locally decoupled and attenuated parasitic inductances of the connecting lines to the voltage source.

The test circuit 10 further includes one with the emitter terminal 13 connected load resistor arrangement 15 on. The load resistor arrangement 15 consists in this embodiment of four parallel load resistors R5 . R6 . R7 . R8 , About this load resistor arrangement 15 is through the test circuit 10 generates a voltage pulse train.

The in the 5 shown test circuit 10 also has one with the base connector 11 connected drive circuit 16 on. The drive circuit 16 has a signal generator 17 which is an arbitrary generator in this embodiment, and is arranged to connect to the base terminal 11 one from the signal generator 17 generated sequence of trigger signals in the form of voltage pulses is supplied. The signal generator 17 generates for this purpose a sequence of similar, rectangular voltage pulses at regular intervals around the avalanche transistor to be tested T3 to trigger at regular intervals.

The drive circuit 16 also has a fast diode D1 on, which serves the signal generator 17 in front of one of the avalanche transients to be tested T3 caused kickback voltage to protect. The drive circuit 16 also has two terminators R9 and R10 which serve as termination of the transmission line and prevent line reflections. The drive circuit 16 also has a coupling capacitor C4 auf which serves to filter out a DC voltage component, ie to block.

The test circuit 10 also has a tension measuring device 18 , which is adapted to the timing of the over the load resistor arrangement 15 to measure and display the decreasing output voltage. The tension measuring device 18 is in the in 5 shown embodiment, an oscilloscope. To the over the load resistance arrangement 15 To measure and display falling output voltage is the voltage measuring device 18 to the load resistor arrangement 15 connected in parallel.

In this way, the tension measuring device 18 as a time course of the output voltage indicate a stable voltage pulse sequence, which is above the load resistor arrangement 15 is generated when the avalanche transistor to be tested T3 triggers on each trigger signal and thereby generates an output pulse. The of the tension measuring device 18 indicated steady voltage pulse sequence indicates that the set test voltage Ut has reached the breakdown voltage.

The 6 shows a schematic representation of an embodiment of an imaging system according to the invention 30 , The imaging system 30 has a pulse generator according to the invention 1 of the type described above and an image intensifier 31 with a controllable gain time window.

The pulse generator 1 has a pulse generation unit 2 with four pulse generating sections and a control unit 3 with each pulse generation section of the pulse generation unit 2 is technically connected. The pulse generation unit 2 has an output terminal OUT at which an output pulse sequence is generated, which comprises a plurality of output pulses in the form of rectangular voltage pulses offset in time from one another and generated by different pulse generation sections. The control unit 2 of the pulse generator 1 has a synchronization input 8th and is adapted to generate the trigger signals corresponding to the pulse generation sections of the pulse generation unit 2 are fed to a synchronization input 8th to synchronize supplied high-frequency reference signal.

The image intensifier 31 has a gate input 32 on. Above one at the gate entrance 32 applied voltage is the gain time window of the image intensifier 31 controllable. The output terminal OUT the pulse generation unit 2 of the pulse generator 1 is with the gate input 32 of the image intensifier 31 connected to the image intensifier 31 supplied by the pulse generator output pulses in the form of voltage pulses and thereby the gain time window of the image intensifier 31 to control.

The imaging system 30 of in 6 embodiment shown also has a reference signal source 33 which generates a high frequency reference signal. Furthermore, the imaging system 30 a driver unit 34 which is adapted to a physical process depending on the high frequency reference signal 35 for generating a primary optical signal 36 to stimulate.

The reference signal source 33 is with the driver unit 34 technically connected to the driver unit 34 to supply the high frequency reference signal. Furthermore, the reference signal source 33 with the synchronization input 8th the control unit 3 of the pulse generator 1 signal connected to the control unit 3 also to supply the high frequency reference signal. The image intensifier 31 is set up depending on the image intensifier 31 from the pulse generator 1 supplied output pulses, that is, depending on the voltage pulses, the primary optical signal 36 within the gain window to a secondary optical signal 37 to reinforce.

Finally, the imaging system points 30 a camera 38 which is adapted to the secondary optical signal 37 to capture and create an image from it.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 3555301 [0013]

Claims (22)

A high repetition frequency pulse generator (1) comprising a pulse generating unit (2) and a control unit (3), the pulse generating unit (2) having a load terminal connectable output terminal (OUT) and a plurality of pulse generating sections (4) and each pulse generation section (4) a control input (IN) to which a trigger signal (TS, TS1, TS2, TS3, TS4) can be supplied, - Has a charging circuit (5) which is connectable to a supply voltage and which has at least one arranged for storing an electric charge charge storage element (C3, TL), and - A between the charging circuit (5) and the output terminal (OUT) of the pulse generating unit (2) connected transistor arrangement (6), which can take a locked and a conductive state and at least one avalanche transistor (T1, T2), wherein - The charging circuit (5) is adapted to charge the charge storage element (C3, TL) with an electrical charge when the charging circuit (5) is connected to the supply voltage and the transistor arrangement (6) has assumed a locked state, and - The transistor arrangement (6) is adapted to pass from the locked state to the conductive state, when the control input (IN), the trigger signal (TS, TS1, TS2, TS3, TS4) is supplied, and in the conductive state by discharging the Charge storage element (C3, TL) utilizing an avalanche effect occurring in the at least one avalanche transistor (T1, T2) to generate an output pulse at the output terminal (OUT) of the pulse generation unit (2), and wherein the control unit (3) - is signal-technically connected to each pulse generation section (4) of the pulse generation unit (2) via the control input (IN) of the pulse generation section (4), is configured to generate a trigger signal sequence comprising a plurality of trigger signals (TS, TS1, TS2, TS3, TS4) offset in time from one another, - And is arranged to supply the individual temporally offset trigger signals (TS, TS1, TS2, TS3, TS4) sequentially different pulse generating sections (4), so that the pulse generating unit (2) at its output terminal (OUT) generates an output pulse sequence comprising a plurality comprises output pulses offset in time and generated by different pulse generating sections (4). Pulse generator (1) after Claim 1 Characterized in that the control unit (3) is adapted to the various pulse generating portions (4) supplying the temporally mutually offset trigger signals (TS, TS1, TS2, TS3, TS4) sequentially and cyclically, wherein in each cycle of each pulse generating section (4) at least one trigger signal (TS, TS1, TS2, TS3, TS4), in particular exactly one trigger signal (TS, TS1, TS2, TS3, TS4), is supplied. Pulse generator (1) after Claim 1 or 2 , characterized in that the pulse generating sections (4) are connected in parallel with each other. Pulse generator (1) according to one of the preceding claims, characterized in that the charge storage element (C3, TL) comprises a capacitor (C3). Pulse generator (1) according to one of the preceding claims, characterized in that the charge storage element (C3, TL) comprises a delay line (TL), in particular a line section of an electrical line, in particular a line section of a coaxial line, a line section of a stripline and / or a Line section of another electrical waveguide comprises. Pulse generator (1) according to one of the preceding claims, characterized in that the pulse generating sections (4) each have a control circuit (7) connected between the control input (IN) and the transistor arrangement (6) for driving the transistor arrangement (6), the drive circuit (7) - a terminating resistor (R2) which terminates a connection line, via which the control unit (3) is signal-connected to the control input (IN) of the pulse generation section (4), with the line impedance of the connection line, and / or - a coupling capacitor (C2), which produces a capacitive coupling between the control input (IN) and the transistor arrangement (6), and / or - a signal transformer (TR1), which galvanically isolates the control input (IN) from the transistor arrangement (6). Pulse generator (1) according to one of the preceding claims, characterized in that the transistor arrangement (6) comprises a series connection of avalanche transistors (T1, T2) and / or a parallel connection of avalanche transistors (T1, T2) and / or avalanche transistors (T1, T2 ) constructed Marx circuit. Pulse generator (1) according to one of the preceding claims, characterized in that the pulse generation sections (4) are identical to each other. Pulse generator (1) according to one of the preceding claims, characterized in that the pulse generation unit (2) has at least four or at least six or at least eight or at least ten or at least twelve or at least sixteen or at least twenty or at least one hundred pulse generating sections (4). Pulse generator (1) according to one of the preceding claims, characterized in that the trigger signal (TS, TS1, TS2, TS3, TS4) is a trigger pulse, in particular a trigger pulse in the form of a voltage pulse, in particular a trigger pulse in the form of a rectangular voltage pulse. Pulse generator (1) according to one of the preceding claims, characterized in that the pulse generating unit (2) has a load resistor (RL) connected to the output terminal (OUT), via which a voltage pulse can be tapped as an output pulse. Pulse generator (1) according to one of the preceding claims, characterized in that the control unit (3) has a synchronization input (8) and the control unit (3) is adapted to generate the trigger signals (TS, TS1, TS2, TS3, TS4). the trigger signal sequence to a synchronizing input (8) supplied reference signal, in particular a high-frequency reference signal to synchronize. Pulse generator (1) according to the preceding claim, characterized in that the control unit (3) has a configurable delay element with which the phase shift between the reference signal and the trigger signals (TS, TS1, TS2, TS3, TS4) of the trigger signal sequence can be configured. Pulse generator (1) according to one of the preceding claims, characterized in that the avalanche transistors (T1, T2) of the different pulse generating sections (4) have matching electrical parameters, in particular matching breakdown voltages. Pulse generator (1) according to one of the preceding claims, characterized in that the supply voltages of the pulse generation sections (4) are different and / or independently configurable and / or in each case to a breakdown voltage of the at least one avalanche transistor (T1, T2) of the respective pulse generation section ( 4) are adjusted. Pulse generator (1) according to one of the preceding claims, characterized in that the control unit (3) has an FPGA (9). Pulse generator (1) according to one of the preceding claims, characterized in that the pulse generator (1) is adapted to generate the output pulses of the output pulse sequence with a repetition frequency of at least 10 MHz or at least 20 MHz or at least 25 MHz. A test method for determining a breakdown voltage of a bipolar transistor (T3), in particular an avalanche transistor, comprising the steps of: a) providing a test circuit (10) comprising - a base terminal (11) connectable to the base of the bipolar transistor (T3), one connected to the collector of the Bipolar transistor (T3) connectable collector terminal (12) and an emitter of the bipolar transistor (T3) connectable emitter terminal (13), - an adjustable voltage source (14), which supplies an adjustable test voltage (Ut), - one between the collector terminal ( 12) and the adjustable voltage source (14) connected charging circuit (19), wherein the charging circuit (19) has at least one arranged to store an electrical charge charge storage element (C3), which can be charged with an electric charge provided by the adjustable voltage source (14) is a load resistor connected to the emitter terminal (13) having at least one load resistor (R5, R6, R7, R8), - one with the base terminal (11) connected to drive circuit (16), wherein the drive circuit (16) comprises a signal generator (17) and the Drive circuit (16) is adapted to supply to the base terminal (11) a sequence of trigger signals generated by the signal generator (17) in the form of voltage pulses, and - a voltage measuring device (18) which is adapted to the temporal course of one above the B) providing a bipolar transistor (T3) to be tested, in particular an avalanche transistor, c) connecting the bipolar transistor (T3) to be tested to the test circuit (10), the base of the bipolar transistor (T3 ) to the base terminal (11), the emitter of the bipolar transistor (T3) to the emitter terminal (13) and the collector of the bipolar transistor (T3) be connected to the collector terminal (12), d) increasing the adjustable test voltage until the voltage measuring device (18) displays as a time characteristic of the output voltage a continuous voltage pulse sequence, e) determining the last set test voltage as the breakdown voltage of the bipolar transistor to be tested (T3). Selection method for selecting matching breakdown voltages having bipolar transistors (T3), in particular avalanche transistors, comprising the steps - Providing a number to be tested bipolar transistors (T3), in particular avalanche transistors of the same type, - Determining the breakdown voltage of each bipolar transistor to be tested (T3) by a test method the characteristics of the Claim 18 , - Selecting those bipolar transistors (T3) for which matching breakdown voltages have been determined. Pulse generator (1) according to one of Claims 1 to 17 , characterized in that the avalanche transistors (T1, T2) of the different pulse generating sections (4) have matching breakdown voltages and by a selection method with the characteristics of Claim 19 have been selected. An imaging system (30) comprising a pulse generator (1) following one of Claims 1 to 17 or after Claim 20 and an image intensifier (31) having a controllable gain time window, wherein - the image intensifier (31) has at least one gate input (32) and the gain time window of the image intensifier (31) can be controlled via a voltage applied to the gate input (32) and - the output terminal (OUT) of the pulse generating unit (2) of the pulse generator (1) is connected to the gate input (32) of the image intensifier (31) for supplying output pulses generated by the pulse generator (1) to the image intensifier (31) and thereby to control the gain window of the image intensifier (31). Imaging system (30) according to the preceding claim, characterized in that the pulse generator (1) is a pulse generator (1) according to Claim 12 and - the imaging system (30) has a reference signal source (33) which generates a reference signal, and - the imaging system (30) has a driver unit (34) which is set up in dependence on the reference signal a physical process (35 ) and / or a physical object for generating a primary optical signal (36), and - the reference signal source (33) is signal-connected to the driver unit (34) in order to supply the reference signal to the drive unit (34), and the reference signal source (33 ) is signal-connected to the synchronization input (8) of the control unit (3) of the pulse generator (1) in order to supply the reference signal to the control unit (3), and - the image intensifier (31) is set up in dependence on the image intensifier (31) from the pulse generator (1) supplied output pulses, the primary optical signal (36) within the gain time window to a secondary optical S signal (37), and - the imaging system (30) comprises a camera (38) adapted to detect the secondary optical signal (37) and to form an image therefrom.

Images