BJT avalanche transistor test circuit and method for ground penetrating radar pulse source

Abstract

This invention discloses a test circuit and method for BJT avalanche transistors used in ground-penetrating radar pulse sources, relating to the field of transistor performance testing. In this circuit, a DC source is connected to the collector of the BJT transistor under test (DUT); a signal source is connected to the base of the DUT via a switch; the collector of the DUT is also connected to a signal output terminal; the signal output terminal is connected to an oscilloscope; the DC source, signal source, and oscilloscope are all connected to a host computer; the switch controls one DUT transistor to turn on during each test; the host computer controls the output voltage of the DC source and the frequency of the signal output from the signal source to obtain the collector-emitter avalanche breakdown voltage and avalanche breakdown equivalent velocity of the target transistor; the performance of the BJT transistor is determined based on the avalanche breakdown voltage and avalanche breakdown equivalent velocity. This invention enables the testing of the collector-emitter breakdown performance parameters of BJT transistors.

Description

Technical Field

[0001] This invention relates to the field of transistor performance testing, and in particular to a test circuit and method for a BJT avalanche transistor used in ground penetrating radar pulse sources. Background Technology

[0002] To improve the detection accuracy and depth of shock pulse ground-penetrating radar (GPR), it is necessary to increase the electromagnetic wave transmission frequency and power. To achieve high-frequency, high-power electromagnetic wave transmission, a high-amplitude, narrow-pulse-width pulse source needs to be designed. A high-amplitude pulse source can improve the detection depth of GPR; a narrow-pulse-width pulse source can improve the detection resolution. To achieve these pulse source characteristics, a Marx circuit is used to design an ultra-wideband pulse signal source.

[0003] BJT transistors are the core components of Marx circuits. With a fixed number of cascaded BJT transistors in a Marx circuit, the operating voltage depends on the avalanche breakdown voltage (Vceo) of the BJT transistors. Therefore, when selecting BJT transistors for a pulse source, the most important parameter to consider is the collector-emitter breakdown voltage (Vceo). Avalanche performance parameters of BJT transistors from different manufacturers vary significantly, and even transistors of the same model and batch from the same manufacturer still exhibit some differences. To ensure the consistency of BJT transistor performance parameters in ground-penetrating radar pulse sources and to improve the manufacturing speed of pulse sources, large-scale, rapid testing of BJT transistor avalanche performance parameters is necessary.

[0004] In the test parameters, the BJT transistor reached the breakdown voltage V. ceo The breakdown speed after the BJT transistor reaches its breakdown voltage V directly affects the pulse width and peak value of the Marx circuit output pulse. ceo The faster the speed, the closer the waveform of the Marx circuit output pulse is to the ideal state, i.e., narrow pulse width and high amplitude. Simultaneously, the narrower the pulse width of the Marx circuit output pulse, the higher the upper limit of the pulse source repetition frequency. If the BJT transistor reaches its breakdown voltage V... ceo The slower the speed, the more limited the adjustment of the pulse source repetition frequency will be, making it impossible to apply in some situations where the pulse source repetition frequency requirement is high.

[0005] To test the collector-emitter breakdown performance parameters of BJT transistors used in ground-penetrating radar pulse sources, it is particularly important to design a test circuit and method for BJT avalanche transistors used in ground-penetrating radar pulse sources. Summary of the Invention

[0006] Based on this, embodiments of the present invention provide a test circuit and method for BJT avalanche transistors used in ground-penetrating radar pulse sources, so as to test the collector-emitter breakdown performance parameters of BJT transistors, thereby manufacturing high-amplitude, narrow-pulse-width pulse sources.

[0007] To achieve the above objectives, embodiments of the present invention provide the following solutions:

[0008] A test circuit for a ground-penetrating radar pulse source using a BJT avalanche transistor includes: a DC source, a signal source, a switch, a signal output terminal, an oscilloscope, and a host computer;

[0009] The DC source is connected to the collector of the BJT transistor under test; the signal source is connected to the base of the BJT transistor under test via the switch; the collector of the BJT transistor under test is also connected to the signal output terminal; the signal output terminal is connected to the oscilloscope; the DC source, the signal source, and the oscilloscope are all connected to the host computer; there is at least one BJT transistor under test.

[0010] The switch is used to control the BJT transistor under test to turn on during each test;

[0011] The host computer is used for:

[0012] When the target transistor is turned on, the voltage output by the DC source is controlled to increase from a first set voltage value to a second set voltage value in a set voltage step value. Each increase in voltage value is a voltage level. At each voltage level, the frequency of the TTL signal output by the signal source is controlled to increase from a first set frequency value to a second set frequency value in a set frequency step value. The target transistor is a BJT transistor under test in the current test.

[0013] Determine the collector-emitter avalanche breakdown voltage and avalanche breakdown equivalent velocity of the target transistor;

[0014] Wherein, the avalanche breakdown voltage is the DC source output voltage that increases as the DC source output voltage increases, and the increase in the output voltage detected by the oscilloscope is greater than the first preset increment; when the increase in the output voltage detected by the oscilloscope is greater than the first preset increment, and the DC source output voltage continues to increase until the second voltage preset value is reached, the change in the output voltage detected by the oscilloscope is less than the second preset increment; the first preset increment is greater than the second preset increment;

[0015] Wherein, the avalanche breakdown equivalent velocity is the frequency of the TTL signal output by the signal source when the DC source outputs at the avalanche breakdown voltage, and as the frequency of the TTL signal output by the signal source increases, the output voltage detected by the oscilloscope decreases to a set proportion of the maximum output voltage.

[0016] Based on the avalanche breakdown equivalent velocity, the output parameter results are determined; the output parameter results include: the amplitude of the output voltage detected by the oscilloscope at each frequency point of each voltage level and the expected repetition frequency of the target transistor.

[0017] The performance of the target transistor is determined based on the output parameter results.

[0018] Optionally, the ground-penetrating radar pulse source test circuit using a BJT avalanche transistor further includes: a current-limiting resistor;

[0019] The DC source is connected to the collector of the BJT transistor under test through the current-limiting resistor.

[0020] Optionally, the ground-penetrating radar pulse source test circuit using a BJT avalanche transistor further includes: an attenuator;

[0021] The signal output terminal is connected to the oscilloscope via the attenuator.

[0022] Optionally, the ground-penetrating radar pulse source test circuit using a BJT avalanche transistor further includes: a filtering module;

[0023] The DC source is connected to the current-limiting resistor through the filter module.

[0024] Optionally, the ground-penetrating radar pulse source test circuit using a BJT avalanche transistor further includes: an RC differentiating circuit and an RC charging and discharging circuit;

[0025] The signal source is connected to the switch through the RC differentiating circuit; the collector of the BJT transistor under test is connected to the signal output terminal through the RC charging and discharging circuit.

[0026] Optionally, the switch is a DIP switch; the number of bits in the DIP switch is not less than the number of BJT transistors under test; one bit in the DIP switch is used to control one BJT transistor under test.

[0027] Optionally, in determining the performance of the target transistor based on the output parameter results, the host computer is specifically used for:

[0028] The performance score of the target transistor is calculated based on the output parameter results; the performance score is a first score, a second score, or a total score; the total score is the sum of the first score and the second score.

[0029] The performance of the target transistor is determined based on the performance score.

[0030] The formula for calculating the first fraction is as follows:

[0031]

[0032] Where g1 represents the first fraction; f1 represents the expected repetition frequency; and f0 represents the applied repetition frequency. Indicates not greater than The largest integer;

[0033] The formula for calculating the second fraction is:

[0034]

[0035] Where g2 represents the second fraction; V1 is the amplitude of the maximum output voltage detected by the oscilloscope; and V0 is the applied output voltage. Indicates not greater than The largest integer.

[0036] Optionally, the host computer is also used for:

[0037] After all the BJT transistors under test have been tested, their performance scores are sorted from high to low to obtain a score sequence.

[0038] The BJT transistors corresponding to the pre-set number of performance scores in the scoring sequence are determined as preferred BJT transistors; the preferred BJT transistors are used to construct ground-penetrating radar pulse sources.

[0039] This invention also provides a test method for a BJT avalanche transistor used in a ground-penetrating radar pulse source. The method is used in the aforementioned test circuit for a BJT avalanche transistor used in a ground-penetrating radar pulse source. The method includes:

[0040] When the target transistor is turned on, the voltage output by the DC source is increased from a first set voltage value to a second set voltage value in set voltage step values. Each voltage increase is a voltage level. At each voltage level, the frequency of the TTL signal output by the signal source is increased from a first set frequency value to a second set frequency value in set frequency step values. The target transistor is a BJT transistor under test in the current test. During each test, a switch controls one BJT transistor under test to be turned on.

[0041] Determine the collector-emitter avalanche breakdown voltage and avalanche breakdown equivalent velocity of the target transistor;

[0042] Wherein, the avalanche breakdown voltage is the DC source output voltage that increases as the DC source output voltage increases, and the increase in the output voltage detected by the oscilloscope is greater than the first preset increment; when the increase in the output voltage detected by the oscilloscope is greater than the first preset increment, and the DC source output voltage continues to increase until the second voltage preset value is reached, the change in the output voltage detected by the oscilloscope is less than the second preset increment; the first preset increment is greater than the second preset increment;

[0043] Wherein, the avalanche breakdown equivalent velocity is the frequency of the TTL signal output by the signal source when the DC source outputs at the avalanche breakdown voltage, and as the frequency of the TTL signal output by the signal source increases, the output voltage detected by the oscilloscope decreases to a set proportion of the maximum output voltage.

[0044] Based on the avalanche breakdown equivalent velocity, the output parameter results are determined; the output parameter results include: the amplitude of the output voltage detected by the oscilloscope at each frequency point of each voltage level and the expected repetition frequency of the target transistor.

[0045] The performance of the target transistor is determined based on the output parameter results.

[0046] Optionally, the performance of the target transistor is determined based on the output parameter results, specifically including:

[0047] The performance score of the target transistor is calculated based on the output parameter results; the performance score is a first score, a second score, or a total score; the total score is the sum of the first score and the second score.

[0048] The performance of the target transistor is determined based on the performance score.

[0049] The formula for calculating the first fraction is as follows:

[0050]

[0051] Where g1 represents the first fraction; f1 represents the expected repetition frequency; and f0 represents the applied repetition frequency. Indicates not greater than The largest integer;

[0052] The formula for calculating the second fraction is:

[0053]

[0054] Where g2 represents the second fraction; V1 is the amplitude of the maximum output voltage detected by the oscilloscope; and V0 is the applied output voltage. Indicates not greater than The largest integer.

[0055] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0056] This invention proposes a test circuit and method for BJT avalanche transistors used in ground-penetrating radar pulse sources. The method involves setting up a DC source, a signal source, a switch, a signal output terminal, an oscilloscope, and a host computer. During each test, the switch controls the activation of one BJT transistor under test. The host computer controls the output voltage of the DC source and the frequency of the signal output from the signal source to obtain the avalanche breakdown voltage and equivalent avalanche breakdown velocity of the target transistor. Based on these parameters, the performance of the BJT transistor is determined, enabling the testing of its collector-emitter breakdown performance parameters. Subsequently, based on the test results, a high-performance BJT transistor is selected to manufacture the pulse source, resulting in a high-amplitude, narrow-pulse-width pulse source. Attached Figure Description

[0057] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0058] Figure 1 This is a schematic diagram of the BJT avalanche transistor test circuit for a ground-penetrating radar pulse source provided in an embodiment of the present invention.

[0059] Figure 2 This is a structural layout diagram of the BJT avalanche transistor test circuit for a ground-penetrating radar pulse source provided in an embodiment of the present invention.

[0060] Figure 3 The circuit schematic diagram of the BJT avalanche transistor test circuit for ground-penetrating radar pulse source provided in the embodiment of the present invention;

[0061] Figure 4 A schematic diagram of the waveform of the TTL signal acting on the base after passing through the differentiating circuit at the start of the test, provided for an embodiment of the present invention;

[0062] Figure 5 This is a schematic diagram of the waveform of a TTL signal acting on the base after passing through a differentiating circuit when it is at a low level, as provided in an embodiment of the present invention. Detailed Implementation

[0063] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0064] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0065] See Figure 1 The BJT avalanche transistor test circuit for the ground-penetrating radar pulse source in this embodiment includes: a DC source, a signal source, a switch, a signal output terminal, an oscilloscope, and a host computer.

[0066] The DC source is connected to the collector of the BJT transistor under test; the signal source is connected to the base of the BJT transistor under test through the switch; the collector of the BJT transistor under test is also connected to the signal output terminal; the signal output terminal is connected to the oscilloscope; the DC source, the signal source, and the oscilloscope are all connected to the host computer; there is at least one BJT transistor under test.

[0067] The switch is used to control the BJT transistor under test to turn on during each test.

[0068] The host computer is used for:

[0069] When the target transistor is turned on, the voltage output by the DC source is controlled to increase from a first set voltage value to a second set voltage value in a set voltage step value. Each increase in voltage value is a voltage level. At each voltage level, the frequency of the TTL signal output by the signal source is controlled to increase from a first set frequency value to a second set frequency value in a set frequency step value. The target transistor is a BJT transistor under test in the current test.

[0070] Determine the collector-emitter avalanche breakdown voltage and avalanche breakdown equivalent velocity of the target transistor.

[0071] Wherein, the avalanche breakdown voltage is the DC source output voltage that increases as the DC source output voltage increases, and the increase in the output voltage detected by the oscilloscope is greater than the first set increment; when the increase in the output voltage detected by the oscilloscope is greater than the first set increment, and the DC source output voltage continues to increase until the second voltage set value is reached, the change in the output voltage detected by the oscilloscope is less than the second set increment; the first set increment is greater than the second set increment.

[0072] In practical applications, the second setting increment is much smaller than the first setting increment. The second setting increment can be 0. That is to say, in the process of controlling the DC source output voltage to increase from the first setting voltage value to the second setting voltage value in a set voltage step value, the output voltage detected by the oscilloscope is significantly increased compared with the output voltage after the last change, and the DC source output voltage detected by the oscilloscope does not increase or change significantly after the DC source voltage is subsequently increased. The DC source output voltage when this occurs is the avalanche breakdown voltage.

[0073] Wherein, the avalanche breakdown equivalent velocity is the frequency of the TTL signal output by the signal source when the DC source outputs at the avalanche breakdown voltage, and as the frequency of the TTL signal output by the signal source increases, the output voltage detected by the oscilloscope decreases to a set proportion of the maximum output voltage.

[0074] The output parameters are determined based on the avalanche breakdown equivalent velocity. These output parameters include: the amplitude of the output voltage detected by the oscilloscope at each frequency point for each voltage level, and the expected repetition frequency of the target transistor. The output parameters may also include: the collector-emitter breakdown time of the target transistor and the peak output voltage within the scanning frequency range. The expected repetition frequency of the target transistor is determined based on the avalanche breakdown equivalent velocity; specifically, the avalanche breakdown equivalent velocity is used as the expected repetition frequency. The collector-emitter breakdown time of the target transistor is also determined based on the avalanche breakdown equivalent velocity, and the expected repetition frequency is no greater than the reciprocal of the avalanche breakdown time.

[0075] The performance of the target transistor is determined based on the output parameter results.

[0076] In one example, the ground-penetrating radar pulse source test circuit using a BJT avalanche transistor further includes a current-limiting resistor; the DC source is connected to the collector of the BJT transistor under test through the current-limiting resistor. The resistance value of the current-limiting resistor can be 10kΩ.

[0077] In one example, the ground-penetrating radar pulse source test circuit using a BJT avalanche transistor further includes an attenuator; the signal output terminal is connected to the oscilloscope through the attenuator.

[0078] In one example, the ground-penetrating radar pulse source uses a BJT avalanche transistor test circuit, which further includes a filtering module; the DC source is connected to the current-limiting resistor through the filtering module. The filtering module may include three parallel filtering capacitors, each with a capacitance of 100nF.

[0079] In one example, the ground-penetrating radar pulse source using a BJT avalanche transistor test circuit further includes an RC differentiating circuit and an RC charge-discharge circuit. The signal source is connected to the switch via the RC differentiating circuit; the collector of the BJT transistor under test is connected to the signal output terminal via the RC charge-discharge circuit. The RC differentiating circuit and the RC charge-discharge circuit have the same structure, both consisting of a capacitor and a resistor, with slightly different parameter selections. The RC differentiating circuit consists of a 100pF capacitor and a 51Ω resistor; the RC charge-discharge circuit consists of a 30pF capacitor and a 51Ω resistor.

[0080] In this example, the RC charging and discharging circuit functions as follows: when the BJT transistor is not avalanche breakdown, the power supply charges the capacitor, and the capacitor stores energy; after the BJT transistor is avalanche breakdown, the transistor conducts, the capacitor discharges as an equivalent power source, and the discharged current generates a voltage pulse through the resistor.

[0081] In one example, the switch is a DIP switch; the number of bits in the DIP switch is not less than the number of BJTs under test; one bit in the DIP switch is used to control one BJT under test. For example, the number of bits in the DIP switch can be 10, corresponding to testing the performance of 10 BJTs under test.

[0082] In one example, in determining the performance of a target transistor based on the output parameter results, the host computer is specifically configured to: calculate a performance score for the target transistor based on the output parameter results; the performance score is a first score, a second score, or a total score; the total score is the sum of the first score and the second score; and determine the performance of the target transistor based on the performance score.

[0083] The formula for calculating the first fraction is as follows:

[0084]

[0085] Where g1 represents the first fraction; f1 represents the expected repetition frequency; and f0 represents the applied repetition frequency. Indicates not greater than The maximum integer value is f1. f1 is obtained from the test circuit measurement; that is, the expected repetition frequency is the repetition frequency applied when the circuit produces the highest output signal in the frequency scan of the above steps. The expected repetition frequency of the target transistor in the above output parameter results can be directly substituted. f0 is set manually, depending on how many repetition frequency the transistor under test will be used in the circuit. In practical applications, the value of f0 can be 200kHz.

[0086] The formula for calculating the second fraction is:

[0087]

[0088] Where g2 represents the second fraction; V1 is the amplitude of the maximum output voltage detected by the oscilloscope; and V0 is the applied output voltage. Indicates not greater than The largest integer. V1 is the voltage value measured by the test circuit, that is, the voltage value that causes a sudden increase in the output voltage of the test circuit during the voltage scan in the above steps. It is determined based on the amplitude of the output voltage detected by the oscilloscope at each frequency point of each voltage range in the output parameter results. V0 is set manually, depending on how many output voltage circuits the transistor under test will be used in. The value of V0 can be 110V.

[0089] Furthermore, this embodiment can also demonstrate the collector-emitter breakdown time of the target transistor and the peak output voltage within the scanning frequency range, which also helps to understand the performance of the target transistor.

[0090] In one example, the host computer is also used for:

[0091] After all the BJT transistors under test have been tested, their performance scores are sorted from high to low to obtain a score sequence. The BJT transistors corresponding to the first set number of performance scores in the score sequence are determined as preferred BJT transistors. The preferred BJT transistors are used to construct ground-penetrating radar pulse sources.

[0092] In one example, the DC source could be V. CC Power supply terminal; TTL signal terminal can be selected for the signal source; OUTPUT antenna terminal can be selected for the signal output terminal.

[0093] The following example uses 10 BJT transistors under test, combined with... Figure 2 and Figure 3 The specific structure and testing process of the BJT avalanche transistor test circuit for the aforementioned ground-penetrating radar pulse source are further explained in detail.

[0094] To quickly test the overall performance of BJT transistors, BJT transistors suitable for ground-penetrating radar pulse sources are selected, and the design layout is as follows. Figure 2 As shown, its schematic diagram is as follows: Figure 3 As shown.

[0095] The test circuit for the BJT avalanche transistor used in the ground penetrating radar pulse source mainly consists of V CCThe circuit consists of power supply terminal RF3, TTL signal terminal RF1, OUTPUT antenna terminal RF2, filter capacitors C3-C5, current limiting resistor R1, BJT transistors under test Q1, Q2, Q3, Q4, Q5, Q6, Q7, Q8, Q9, Q10, 10-bit DIP switch SW1, an RC differentiating circuit (including resistor R2 and capacitor C1), and an RC charging / discharging circuit (including resistor R3 and capacitor C2). A 90-160V adjustable regulated DC power supply output is connected to the V... CC Power terminal, V CC The power supply output, after being filtered by capacitors C3, C4, and C5 to remove high-frequency noise, is applied to the collector of the BJT transistor through current-limiting resistor R1; the collectors of the ten BJT transistors under test are connected together and connected to V through the current-limiting resistor. CC The power supply terminals are connected, and the emitter is connected to ground. Simultaneously, the base of the selected BJT transistor is grounded via a 10-bit DIP switch and resistor R2. V CC The power supply terminal RF3, TTL signal terminal RF1, and OUTPUT antenna terminal RF2 can all be BWSMA-KE-P001; the 10-bit DIP switch SW1 can be DSWB10LHGET.

[0096] The signal source is connected to the TTL signal terminal of the BJT avalanche transistor test circuit for the ground-penetrating radar pulse source via a coaxial RF cable. The output of the TTL signal terminal is connected to the base of the BJT transistor under test via an RC differentiating circuit. At this time, the reverse bias voltage of the PN junction between the collector and base of the BJT transistor is slightly less than the avalanche breakdown voltage of the PN junction. The unselected BJT transistor has an open base, which has no effect on the rest of the circuit during testing.

[0097] The OUTPUT antenna terminal of the ground-penetrating radar pulse source test circuit using a BJT avalanche transistor is connected to a 20GHz, 10GSa / s oscilloscope via a 20dB attenuator. The DC power supply, signal source, and oscilloscope are connected to a host computer (which can be a computer) via an RS485 module, USB cable, and network cable, respectively, and are controlled by the host computer to send data to the host computer.

[0098] The testing method is as follows:

[0099] Step 1: Select a BJT transistor to be tested by moving the 10-position DIP switch. Only one BJT transistor can be tested at a time, meaning only one of the 10 DIP switches can be turned on at any given time.

[0100] The second step is to start the Matlab automated testing program on the host computer. After the Matlab automated testing program starts, it sends a control word to the 90-160V adjustable regulated DC power supply via the USB to RS485 module to set the power supply's output voltage. This control word includes start / stop and control over the maximum voltage / current values.

[0101] The third step is to obtain the collector-emitter avalanche breakdown voltage V of the BJT transistor. ceo Breakdown equivalent velocity. Specifically:

[0102] 3.1 Sending control signals

[0103] The computer sends commands to the signal source (acting as a signal generator) via the USB cable, controlling the signal source to generate a TTL signal at a set frequency. The TTL signal is a square wave with a 50% duty cycle, a peak-to-peak value of 5V, and a minimum value of 0V. The operating mode is scanning: the power supply output voltage steps from a first set voltage value (e.g., 90V) in 1V increments to a second set voltage value (e.g., 160V). At each voltage level, the TTL signal frequency steps from a first set frequency value (e.g., 10kHz) to a second set frequency value (e.g., 700kHz) in 1kHz increments.

[0104] 3.2 Obtaining the collector-emitter avalanche breakdown voltage V of a BJT transistor ceo Breakdown equivalent velocity

[0105] During the voltage scanning process of the computer-controlled signal source, as the DC source output voltage increases, the output voltage of the ground-penetrating radar pulse source using the BJT avalanche transistor test circuit suddenly increases. The DC source output voltage value at which this sudden increase occurs is the collector-emitter avalanche breakdown voltage V of the BJT transistor. ceo .

[0106] Correspondingly, when the DC source outputs at the avalanche breakdown voltage, as the frequency of the signal output from the signal source increases, the output voltage of the BJT avalanche transistor test circuit for the ground penetrating radar pulse source decreases to a set ratio (e.g., 90%) of the maximum output voltage. The frequency of the TTL signal output by the signal source is then regarded as the equivalent avalanche breakdown speed of the collector-emitter junction of the BJT transistor.

[0107] The principle is as follows: After the test begins, the TTL signal generated by the signal source is transformed into a bidirectional spike signal by an RC differentiating circuit composed of capacitor C1 and resistor R2, which acts on the base of the BJT transistor under test. The waveform is as follows: Figure 4 As shown.

[0108] When the TTL signal is high, the voltage across the PN junction between the collector and base of the BJT transistor does not reach the avalanche breakdown voltage, and the power supply charges capacitor C2 until the voltage across C2 equals the power supply voltage VCC. When the TTL signal is low, the voltage across the PN junction between the collector and base of the BJT transistor reaches the avalanche breakdown voltage, and the PN junction between the emitter and base is cut off. At this time, the PN junction between the collector and base of the BJT transistor is avalanche broken down, forming a circuit. The energy stored in capacitor C2 is released in the circuit R2-C2-R3, causing resistor R3 to generate a negative pulse with a rapid rise and a slow fall (relative to the rise speed), as shown in the waveform. Figure 5 As shown: The pulse width and amplitude of this pulse are the references for considering the above parameters of the BJT transistor. In this pulse, the rise time of the pulse is positively correlated with the avalanche breakdown time of the BJT avalanche transistor. Therefore, the rise time of the pulse is used to represent the equivalent breakdown speed of the BJT avalanche transistor.

[0109] The fourth step is to obtain the output parameter results based on the output of the BJT transistor test and evaluation circuit.

[0110] An oscilloscope acquires the output of a BJT avalanche transistor test circuit for a ground-penetrating radar pulse source and uploads it to a computer via network cable for storage as a two-dimensional vector. The acquisition depth is controlled by Matlab, adjustable from 1000, 1024 to 4096. Matlab processes the stored series of two-dimensional vectors and outputs the parameter results, including: ① the collector-emitter breakdown time of the BJT transistor at each voltage frequency point; ② the amplitude of the output voltage of the BJT avalanche transistor test circuit for the ground-penetrating radar pulse source; ③ the expected repetition frequency of the BJT transistor at each voltage frequency point and the peak output voltage within the scanning frequency range.

[0111] In this process, the signal is sampled at a certain sampling frequency and then quantized into a binary coded stream with a certain quantization precision. The number of bits in this coded stream is the sampling depth. In this embodiment, the sampling depth is expressed as a power of 2 of the number of sampling bits.

[0112] In this process, the breakdown time is measured at each voltage level. The breakdown time is related to the pulse width of the circuit's output pulse; generally, the shorter the breakdown time, the narrower the pulse width. The breakdown time is used in step five, method ①. The maximum repetition frequency in method ① is affected by the breakdown time; the two are negatively correlated. The shorter the breakdown time, the greater the theoretical maximum repetition frequency. The amplitude of the output voltage of the ground-penetrating radar pulse source test circuit using a BJT avalanche transistor is applied in step five, method ②.

[0113] The repetition frequency is the frequency of the TTL signal, which is used in ground-penetrating radar to control the antenna to repeatedly transmit electromagnetic waves.

[0114] The fifth step is to conduct a comprehensive evaluation of the BJT transistor, as follows:

[0115] Method ①: Using the set application repetition frequency as the center, if the equivalent velocity of avalanche breakdown between the collector and emitter of the BJT transistor is within ±5% of the center, that part is considered usable, and a score of 0-20 is awarded depending on how close it is to the center. The calculation formula is as follows:

[0116]

[0117] Since the performance of a transistor changes with the frequency of the control signal, the expected repetition frequency is the optimal application repetition frequency for a computer to evaluate the transistor under test; the application repetition frequency refers to the repetition frequency at which the transistor under test will operate.

[0118] Method ②: With the set application output voltage as the center, if the avalanche breakdown voltage of the BJT transistor collector-emitter is within ±10% of the center, it is considered that the part is usable, and the value will be 0-30 points depending on how close it is to the center.

[0119]

[0120] The model can provide the final test result in three ways: using the first score obtained from method ①, the second score obtained from method ②, or the sum of both (the total score). The final results are arranged from highest to lowest according to the scores of the tested BJT transistors, and detailed information on the corresponding judgment criteria is listed.

[0121] Step 6: Obtain the test results, toggle the 10-bit DIP switch to select the next BJT transistor to be tested and repeat the test until all 10 BJT transistors have been tested.

[0122] The BJT transistors selected through the above testing methods are suitable for use in pulse sources with the expected amplitude and frequency.

[0123] This invention also provides a test method for a BJT avalanche transistor used in a ground-penetrating radar pulse source. The method is used in the aforementioned test circuit for a BJT avalanche transistor used in a ground-penetrating radar pulse source. The method includes:

[0124] (1) When the target transistor is turned on, the voltage output by the DC source is controlled to increase from the first set voltage value to the second set voltage value in a set voltage step value. Each increase in voltage value is a voltage level. At each voltage level, the frequency of the TTL signal output by the signal source is controlled to increase from the first set frequency value to the second set frequency value in a set frequency step value. The target transistor is a BJT transistor under test in the current test. During each test, the switch controls one BJT transistor under test to be turned on.

[0125] (2) Determine the avalanche breakdown voltage and avalanche breakdown equivalent velocity of the collector-emitter junction of the target transistor.

[0126] Wherein, the avalanche breakdown voltage is the DC source output voltage that increases as the DC source output voltage increases, and the increase in the output voltage detected by the oscilloscope is greater than the first set increment; when the increase in the output voltage detected by the oscilloscope is greater than the first set increment, and the DC source output voltage continues to increase until the second voltage set value is reached, the change in the output voltage detected by the oscilloscope is less than the second set increment; the first set increment is greater than the second set increment.

[0127] Wherein, the avalanche breakdown equivalent velocity is the frequency of the TTL signal output by the signal source when the DC source outputs at the avalanche breakdown voltage, and as the frequency of the TTL signal output by the signal source increases, the output voltage detected by the oscilloscope decreases to a set proportion of the maximum output voltage.

[0128] (3) Based on the avalanche breakdown equivalent velocity, determine the output parameter results; the output parameter results include: the amplitude of the output voltage detected by the oscilloscope at each frequency point of each voltage level and the expected repetition frequency of the target transistor.

[0129] (4) Determine the performance of the target transistor based on the output parameter results. Specifically:

[0130] The performance score of the target transistor is calculated based on the output parameter results; the performance score is a first score, a second score, or a total score; the total score is the sum of the first score and the second score; the performance of the target transistor is determined based on the performance score.

[0131] The formula for calculating the first fraction is as follows:

[0132]

[0133] Where g1 represents the first fraction; f1 represents the expected repetition frequency; and f0 represents the applied repetition frequency. Indicates not greater than The largest integer.

[0134] The formula for calculating the second fraction is:

[0135]

[0136] Where g2 represents the second fraction; V1 is the amplitude of the maximum output voltage detected by the oscilloscope; and V0 is the applied output voltage. Indicates not greater than The largest integer.

[0137] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. The methods disclosed in the embodiments are described simply because they correspond to the circuits disclosed in the embodiments; relevant parts can be referred to the circuit section description.

[0138] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A test circuit for a BJT avalanche transistor used in a ground-penetrating radar pulse source, characterized in that, include: DC power source, signal source, switch, signal output terminal, oscilloscope and host computer; The DC source is connected to the collector of the BJT transistor under test; The signal source is connected to the base of the BJT transistor under test via the switch; the collector of the BJT transistor under test is also connected to the signal output terminal; the signal output terminal is connected to the oscilloscope; the DC source, the signal source, and the oscilloscope are all connected to the host computer; there is at least one BJT transistor under test. The switch is used to control the BJT transistor under test to turn on during each test; The host computer is used for: When the target transistor is turned on, the voltage output by the DC source is controlled to increase from a first set voltage value to a second set voltage value in a set voltage step value. Each increase in voltage value is a voltage level. At each voltage level, the frequency of the TTL signal output by the signal source is controlled to increase from a first set frequency value to a second set frequency value in a set frequency step value. The target transistor is a BJT transistor under test in the current test. Determine the collector-emitter avalanche breakdown voltage and avalanche breakdown equivalent velocity of the target transistor; Wherein, the avalanche breakdown voltage is the DC source output voltage that increases as the DC source output voltage increases, and the increase in the output voltage detected by the oscilloscope is greater than the first preset increment; when the increase in the output voltage detected by the oscilloscope is greater than the first preset increment, and the DC source output voltage continues to increase until the second preset voltage value is reached, the change in the output voltage detected by the oscilloscope is less than the second preset increment; the first preset increment is greater than the second preset increment; Wherein, the avalanche breakdown equivalent velocity is the frequency of the TTL signal output by the signal source when the DC source outputs at the avalanche breakdown voltage, and as the frequency of the TTL signal output by the signal source increases, the output voltage detected by the oscilloscope decreases to a set proportion of the maximum output voltage. Based on the avalanche breakdown equivalent velocity, the output parameter results are determined; the output parameter results include: the amplitude of the output voltage detected by the oscilloscope at each frequency point of each voltage level and the expected repetition frequency of the target transistor. The performance of the target transistor is determined based on the output parameter results.

2. The BJT avalanche transistor test circuit for ground-penetrating radar pulse source according to claim 1, characterized in that, Also includes: Current-limiting resistor; The DC source is connected to the collector of the BJT transistor under test through the current-limiting resistor.

3. The BJT avalanche transistor test circuit for ground-penetrating radar pulse source according to claim 1, characterized in that, Also includes: Attenuator; The signal output terminal is connected to the oscilloscope via the attenuator.

4. The BJT avalanche transistor test circuit for ground-penetrating radar pulse source according to claim 2, characterized in that, Also includes: Filtering module; The DC source is connected to the current-limiting resistor through the filter module.

5. The BJT avalanche transistor test circuit for ground-penetrating radar pulse source according to claim 1, characterized in that, Also includes: RC differentiating circuit and RC charging / discharging circuit; The signal source is connected to the switch via the RC differentiating circuit; The collector of the BJT transistor under test is connected to the signal output terminal through the RC charge-discharge circuit.

6. The BJT avalanche transistor test circuit for ground-penetrating radar pulse source according to claim 1, characterized in that, The switch is a DIP switch; the number of bits in the DIP switch is not less than the number of BJT transistors under test; one bit in the DIP switch is used to control one BJT transistor under test.

7. The BJT avalanche transistor test circuit for ground-penetrating radar pulse source according to claim 1, characterized in that, In determining the performance of the target transistor based on the output parameter results, the host computer is specifically used for: The performance score of the target transistor is calculated based on the output parameter results; the performance score is a first score, a second score, or a total score; the total score is the sum of the first score and the second score. The performance of the target transistor is determined based on the performance score. The formula for calculating the first fraction is as follows: Where g1 represents the first fraction; f1 represents the expected repetition frequency; and f0 represents the applied repetition frequency. Indicates not greater than The largest integer; The formula for calculating the second fraction is: Where g2 represents the second fraction; V1 is the amplitude of the maximum output voltage detected by the oscilloscope; and V0 is the applied output voltage. Indicates not greater than The largest integer.

8. The BJT avalanche transistor test circuit for ground-penetrating radar pulse source according to claim 7, characterized in that, The host computer is also used for: After all the BJT transistors under test have been tested, their performance scores are sorted from high to low to obtain a score sequence. The BJT transistors corresponding to the pre-set number of performance scores in the scoring sequence are determined as preferred BJT transistors; the preferred BJT transistors are used to construct ground-penetrating radar pulse sources.

9. A method for testing BJT avalanche transistors for ground-penetrating radar pulse sources, characterized in that, The method is used in the BJT avalanche transistor test circuit for ground-penetrating radar pulse sources according to any one of claims 1-8, and the method includes: When the target transistor is turned on, the voltage output by the DC source is increased from a first set voltage value to a second set voltage value in set voltage step values. Each voltage increase is a voltage level. At each voltage level, the frequency of the TTL signal output by the signal source is increased from a first set frequency value to a second set frequency value in set frequency step values. The target transistor is a BJT transistor under test in the current test. During each test, a switch controls one BJT transistor under test to be turned on. Determine the collector-emitter avalanche breakdown voltage and avalanche breakdown equivalent velocity of the target transistor; Wherein, the avalanche breakdown voltage is the DC source output voltage that increases as the DC source output voltage increases, and the increase in the output voltage detected by the oscilloscope is greater than the first preset increment; when the increase in the output voltage detected by the oscilloscope is greater than the first preset increment, and the DC source output voltage continues to increase until the second preset voltage value is reached, the change in the output voltage detected by the oscilloscope is less than the second preset increment; the first preset increment is greater than the second preset increment; Wherein, the avalanche breakdown equivalent velocity is the frequency of the TTL signal output by the signal source when the DC source outputs at the avalanche breakdown voltage, and as the frequency of the TTL signal output by the signal source increases, the output voltage detected by the oscilloscope decreases to a set proportion of the maximum output voltage. Based on the avalanche breakdown equivalent velocity, the output parameter results are determined; the output parameter results include: the amplitude of the output voltage detected by the oscilloscope at each frequency point of each voltage level and the expected repetition frequency of the target transistor. The performance of the target transistor is determined based on the output parameter results.

10. The test method for BJT avalanche transistors used in ground-penetrating radar pulse sources according to claim 9, characterized in that, The performance of the target transistor is determined based on the output parameter results, specifically including: The performance score of the target transistor is calculated based on the output parameter results; the performance score is a first score, a second score, or a total score; the total score is the sum of the first score and the second score. The performance of the target transistor is determined based on the performance score. The formula for calculating the first fraction is as follows: Where g1 represents the first fraction; f1 represents the expected repetition frequency; and f0 represents the applied repetition frequency. Indicates not greater than The largest integer; The formula for calculating the second fraction is: Where g2 represents the second fraction; V1 is the amplitude of the maximum output voltage detected by the oscilloscope; and V0 is the applied output voltage. Indicates not greater than The largest integer.

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