An ultra-wideband differential pulse source for ground penetrating radar

Abstract

The application discloses a kind of ultra-wideband differential pulse sources for ground penetrating radar, it is related to ground penetrating radar field, the ultra-wideband differential pulse source, comprising: power supply port, DC power module, trigger signal input port, positive polarity pulse output port, negative polarity pulse output port and differential pulse generation module;Differential pulse generation module, comprising: multiple triode module;Triode module, comprising: BJT triode, energy storage capacitor, adjusting capacitor and first current-limiting resistor;BJT triode collector is connected with energy storage capacitor;Adjusting capacitor is connected with energy storage capacitor in parallel;BJT triode emitter is connected with ground through first current-limiting resistor;Power supply port is connected with the collector of BJT triode by DC power module;Trigger signal input port is connected with two pulse output ports by differential pulse generation module.The application can generate the bipolar differential pulse signal with greater amplitude and narrower pulse width.

Description

Technical Field

[0001] This invention relates to the field of ground-penetrating radar, and in particular to an ultra-wideband differential pulse source for ground-penetrating radar. Background Technology

[0002] Detection depth and resolution are two key technical indicators of ground-penetrating radar (GPR). Ultra-wideband narrow-pulse technology is one of the key technologies in shock pulse-based GPR systems. The pulse width and amplitude of the ultra-wideband narrow-pulse technology significantly affect the detection depth and accuracy of GPR, making it crucial for designing high-performance GPR systems. The higher the required detection accuracy of a GPR, the higher the frequency of the required pulse signal, resulting in a narrower pulse from the pulse source and a wider bandwidth. Simultaneously, a larger pulse amplitude from the pulse source leads to a deeper detection depth, clearer echo signals received by the receiver, and easier processing.

[0003] Furthermore, the unipolar Marx pulse circuit obtains positive pulses by connecting an inductor in parallel with the load at the output stage. This method results in poor symmetry of the positive pulses, severe pulse tailing, and an unsatisfactory waveform. In contrast, bipolar differential output, compared to inductive differential bipolar output, offers better waveform symmetry and a larger peak-to-peak value, allowing the antenna to transmit pulse signals more effectively and the receiver to process the received echo signals more efficiently.

[0004] Therefore, to improve the detection depth and accuracy of ground-penetrating radar (GPR) and enhance its performance, it is necessary to generate bipolar differential pulse signals with larger amplitude and narrower pulse width. Currently, designing a pulse source capable of generating such bipolar differential pulse signals is a pressing issue that needs to be addressed. Summary of the Invention

[0005] Based on this, embodiments of the present invention provide an ultra-wideband differential pulse source for ground penetrating radar to generate bipolar differential pulse signals with larger amplitude and narrower pulse width.

[0006] To achieve the above objectives, embodiments of the present invention provide the following solutions:

[0007] An ultra-wideband differential pulse source for ground-penetrating radar includes: a power supply port, a DC power supply module, a trigger signal input port, a positive polarity pulse output port, a negative polarity pulse output port, and a differential pulse generation module;

[0008] The differential pulse generation module includes: multiple transistor modules; each transistor module includes: a BJT transistor, an energy storage capacitor, an adjustment capacitor, and a first current-limiting resistor; the collector of the BJT transistor is connected to the energy storage capacitor; the adjustment capacitor is connected in parallel with the energy storage capacitor; the emitter of the BJT transistor is grounded through the first current-limiting resistor;

[0009] Multiple transistor modules are connected in sequence. In two adjacent transistor modules, the collector of one BJT transistor is connected to the base and emitter of the other BJT transistor through an energy storage capacitor. The base of the first BJT transistor serves as the input terminal of the differential pulse generation module, the emitter of the first BJT transistor serves as the first output terminal of the differential pulse generation module, and the collector of the last BJT transistor serves as the second output terminal of the differential pulse generation module.

[0010] The power supply port is connected to the collector of the BJT transistor in the transistor module through the DC power supply module; the trigger signal input port is connected to the input terminal of the differential pulse generation module; the first output terminal of the differential pulse generation module is connected to the positive polarity pulse output port; and the second output terminal of the differential pulse generation module is connected to the negative polarity pulse output port.

[0011] Optionally, the DC power supply module includes: a boost power supply module and a filter module connected in sequence; the input terminal of the boost power supply module is connected to the power supply port; the filter module is connected to the collector of the BJT transistor in the transistor module.

[0012] The boost power supply module is used to boost the voltage signal provided by the power supply port to obtain a boost signal; the filtering module is used to filter the boost signal.

[0013] Optionally, the ultra-wideband differential pulse source for ground-penetrating radar further includes: an output resistor;

[0014] One end of the output resistor is connected to the collector of the last BJT transistor in the differential pulse generation module and the negative pulse output port, and the other end of the output resistor is grounded.

[0015] Optionally, the transistor module further includes: a second current-limiting resistor;

[0016] The DC power supply module is connected to the collector of the BJT transistor in the transistor module through the second current-limiting resistor.

[0017] Optionally, the filtering module includes three filter capacitors connected in parallel.

[0018] Optionally, the ultra-wideband differential pulse source for ground-penetrating radar further includes: an RC differentiating circuit;

[0019] The trigger signal input port is connected to the input terminal of the differential pulse generation module through the RC differentiating circuit.

[0020] Optionally, the capacitance of both the energy storage capacitor and the regulating capacitor is 20pF; the resistance of the second current-limiting resistor is 51Ω.

[0021] The resistance of the first current-limiting resistor in the first transistor module of the differential pulse generation module is 51Ω, and the resistance of the first current-limiting resistor in the other transistor modules is 10kΩ.

[0022] Optionally, the capacitance of the filter capacitor is 100nF.

[0023] Optionally, the power supply port is V CC Power terminals.

[0024] Optionally, the trigger signal input port is a TTL signal terminal.

[0025] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0026] The differential pulse generation module of this invention includes: multiple transistor modules; each transistor module includes: a BJT transistor, an energy storage capacitor, an adjustment capacitor, and a first current-limiting resistor; the collector of the BJT transistor is connected to the energy storage capacitor; the adjustment capacitor is connected in parallel with the energy storage capacitor; the emitter of the BJT transistor is grounded through the first current-limiting resistor. By adding a first current-limiting resistor to the emitter of the BJT transistor and connecting an adjustment capacitor in parallel across the energy storage capacitor, this invention provides a more ideal waveform, a larger adjustable pulse amplitude, lower cost, and a narrower adjustable pulse width compared to traditional Marx circuits. Therefore, this invention can generate bipolar differential pulse signals with larger amplitude and narrower pulse width. Attached Figure Description

[0027] 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.

[0028] Figure 1 The circuit schematic diagram of an ultra-wideband differential pulse source for ground-penetrating radar provided in an embodiment of the present invention;

[0029] Figure 2 This is a structural layout diagram of an ultra-wideband differential pulse source for ground-penetrating radar provided in an embodiment of the present invention;

[0030] Figure 3 A schematic diagram of the charging equivalent circuit provided in an embodiment of the present invention;

[0031] Figure 4 A schematic diagram of the discharge equivalent circuit provided in an embodiment of the present invention;

[0032] Figure 5 This is a schematic diagram of the output waveform of a TTL signal after passing through a differentiating circuit, provided in an embodiment of the present invention.

[0033] Figure 6 This is a schematic diagram of the output waveforms of the two differential signal output terminals provided in an embodiment of the present invention. Detailed Implementation

[0034] 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.

[0035] 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.

[0036] See Figure 1 The ultra-wideband differential pulse source for ground-penetrating radar in this embodiment includes: a power supply port CN1, a DC power supply module, a trigger signal input port RF1, a positive polarity pulse output port RF3, a negative polarity pulse output port RF2, and a differential pulse generation module.

[0037] The differential pulse generation module includes: multiple transistor modules; each transistor module includes: a BJT transistor, an energy storage capacitor, an adjustment capacitor, and a first current-limiting resistor; the collector of the BJT transistor is connected to the energy storage capacitor; the adjustment capacitor is connected in parallel with the energy storage capacitor; the emitter of the BJT transistor is grounded through the first current-limiting resistor. The BJT transistor is an avalanche transistor.

[0038] Multiple transistor modules are connected in sequence. In two adjacent transistor modules, the collector of one BJT transistor is connected to the base and emitter of the other BJT transistor through an energy storage capacitor. The base of the first BJT transistor serves as the input terminal of the differential pulse generation module, the emitter of the first BJT transistor serves as the first output terminal of the differential pulse generation module, and the collector of the last BJT transistor serves as the second output terminal of the differential pulse generation module.

[0039] The power supply port CN1 is connected to the collector of the BJT transistor in the transistor module through the DC power supply module; the trigger signal input port RF1 is connected to the input terminal of the differential pulse generation module; the first output terminal of the differential pulse generation module is connected to the positive polarity pulse output port RF3; and the second output terminal of the differential pulse generation module is connected to the negative polarity pulse output port RF2.

[0040] In one example, the DC power supply module includes: a boost power supply module U1 and a filter module connected in sequence; the input terminal of the boost power supply module U1 is connected to the power supply port CN1; and the filter module is connected to the collector of the BJT transistor in the transistor module.

[0041] The boost power supply module U1 is used to boost the voltage signal provided by the power supply port CN1 to obtain a boost signal; the filtering module is used to filter the boost signal.

[0042] In one example, the ultra-wideband differential pulse source for ground-penetrating radar further includes an output resistor R12.

[0043] One end of the output resistor R12 is connected to the collector of the last BJT transistor in the differential pulse generation module and the negative pulse output port RF2, and the other end of the output resistor R12 is grounded.

[0044] In one example, the transistor module further includes a second current-limiting resistor; the DC power supply module is connected to the collector of the BJT transistor in the transistor module through the second current-limiting resistor.

[0045] In one example, the filtering module includes three filter capacitors connected in parallel: a first filter capacitor C1, a second filter capacitor C2, and a third filter capacitor C3. In practical applications, the capacitance values ​​of the three filter capacitors can be 100nF.

[0046] In one example, the ultra-wideband differential pulse source for ground-penetrating radar further includes an RC differentiator circuit; the trigger signal input port RF1 is connected to the input of the differential pulse generation module through the RC differentiator circuit.

[0047] The RC differentiating circuit includes: a resistor R6 and a capacitor C9; one end of the capacitor C9 is connected to the trigger signal input port RF1, the other end of the capacitor C9 is connected to the input terminal of the differential pulse generation module, one end of the resistor R6 is connected to the other end of the capacitor C9, and the other end of the resistor R6 is grounded.

[0048] In one example, the capacitance of both the energy storage capacitor and the regulating capacitor is 20pF; the resistance of the second current-limiting resistor is 51Ω.

[0049] If the differential pulse generation module includes a transistor module, the resistance of the first current-limiting resistor in the transistor module is 10kΩ.

[0050] If the differential pulse generation module includes multiple transistor modules, the resistance of the first current-limiting resistor in the first transistor module is 51Ω, and the resistance of the first current-limiting resistor in the other transistor modules is 10kΩ.

[0051] In one example, the power supply port CN1 is V CC Power supply terminal; the trigger signal input port RF1 is a TTL signal terminal.

[0052] The following example uses a differential pulse generation module comprising five transistor modules. Figure 1 The implementation principle of the ultra-wideband differential pulse source will be further explained.

[0053] To further enhance the amplitude of the pulse signal generated by the pulse source, a method was designed by adding a resistor to the emitter of the BJT avalanche transistor in the primary Marx circuit, connecting adjustable capacitors in parallel across the energy storage capacitors in each stage of the Marx circuit, and adjusting the capacitance and resistance values ​​of the differentiating circuit. Figure 2 The ultra-wideband differential pulse source shown is used for ground-penetrating radar. Compared to the original circuit, this design circuit has a more ideal waveform, a larger adjustable pulse amplitude, lower cost, and a narrower adjustable pulse width. Its circuit schematic is shown below. Figure 1 As shown.

[0054] The ultra-wideband differential pulse source circuit for this ground-penetrating radar mainly consists of a power supply port (using VCC power terminal), a DC power supply module (including a boost power supply module U1 and a filter module), a trigger signal input port RF2 (using TTL signal terminal), two differential signal output terminals (including a positive pulse output port RF3 and a negative pulse output port RF2), current-limiting resistors (including a first current-limiting resistor R7 to R11 and a second current-limiting resistor R1 to R5), BJT transistors, energy storage capacitors C4 to C8, an output resistor R12, and an RC differentiating circuit.

[0055] See Figure 1The DC power supply is connected to the VCC power terminal, and the output of the VCC power terminal is connected to the DC power module. The DC power module amplifies the input voltage and then connects it to the left side of the energy storage capacitors C4-C8 and the collectors of the five BJT transistors Q1-Q5 through the filter capacitors C1-C3. Before the TTL trigger signal arrives, the five energy storage capacitors C4-C8 are charged through the first current limiting resistor R7-R11, the second current limiting resistor R1-R5, and the output resistor R12.

[0056] The external TTL trigger signal is connected to the TTL signal terminal. The TTL trigger signal is differentiated by the differentiating circuit composed of R6 and C9 and then applied to the base of BJT transistor Q1. Except for Q1, all the emitters of the BJT transistors are connected to ground after being connected to a 10kΩ resistor. The emitter of Q1 is connected to ground after being connected to a 51Ω resistor.

[0057] The five capacitors C10-C14 connected in parallel with the energy storage capacitors C4-C8 are adjustment capacitors. Their function is to adjust the capacitance value of the energy storage capacitor in this stage of the Marx circuit through the equivalent principle of parallel capacitors. These adjustment capacitors can also be omitted. After the trigger signal arrives, the equivalent capacitance C eq Series discharge generates positive and negative pulses, with an equivalent capacitance C. eq This represents the parallel equivalent capacitance of the energy storage capacitor and the regulating capacitor.

[0058] Of the two differential signal output terminals, RF2 outputs a negative pulse and RF3 outputs a positive pulse. Care should be taken not to reverse the connections when connecting them.

[0059] based on Figure 1 The circuit diagram shown illustrates the implementation principle of this ultra-wideband differential pulse source for ground-penetrating radar:

[0060] When the TTL signal has not arrived, the voltages across the collector and base of the BJT transistor are reverse biased, and the voltage V between the collector and emitter is simultaneously... CE Critical avalanche breakdown voltage V of a BJT transistor CEO The BJT transistor is cut off, and the five energy storage capacitors are charged and stored.

[0061] When the TTL signal arrives: During the positive half-cycle (i.e., half a cycle when the TTL signal voltage is 5V), the RC differentiating circuit outputs a positive pulse. This positive pulse acts on the base of the BJT transistor, reducing the reverse bias voltage across the collector and base of the BJT transistor. This weakens the electric field in the space charge region, consequently reducing the energy gained by the charge carriers passing through the barrier region, and thus decreasing the reverse breakdown current I. CBOThe voltage decreases; during the zero half-cycle (i.e., the half-cycle when the TTL signal voltage is 0), the RC differentiating circuit outputs a negative pulse. This negative pulse acts on the base of the BJT transistor, increasing the reverse bias voltage across the collector and base of the BJT transistor. This strengthens the electric field in the space charge region, increasing the energy gained by the charge carriers passing through the barrier region, and thus increasing the reverse breakdown current I. CBO The increase causes the BJT transistor to enter the negative resistance region, increasing the reverse breakdown voltage V between the collector and emitter. CEO The voltage V across the collector-emitter junction decreases, which in turn leads to a decrease in the collector-emitter voltage V. CE Greater than its reverse breakdown voltage V CEO This triggers avalanche breakdown. After an avalanche breakdown, the collector and emitter of a BJT transistor are essentially short-circuited, and the charging equivalent circuit and discharging equivalent circuit are as follows: Figure 3 and Figure 4 As shown, the output waveform of the TTL signal after passing through the differentiating circuit and the output waveforms of the two differential signal output terminals are as follows: Figure 5 and Figure 6 As shown.

[0062] After a BJT transistor undergoes avalanche breakdown, a circuit is formed between the collector and emitter, and the five energy storage capacitors discharge through the circuit Req-Q1-C4-Q2-C5-Q3-C6-Q4-C7-Q5-C8-R12 (R12 is used here). eq (This represents the equivalent resistance of R6 connected in parallel with R7). The discharge current initially rises rapidly and then gradually decreases. This discharge current acts on R... eq A positive pulse and a negative pulse are output through R3 and R2 respectively via R12. The amplitude of the output pulse can be adjusted by adjusting the resistance values ​​of R7 and R12 to match the antenna impedance.

[0063] Figure 6 The upper middle side is a positive pulse, and the lower side is a negative pulse. Compared with the previous unipolar pulse source, the pulse signal generated by this ultra-wideband differential pulse source has excellent symmetry and a large peak-to-peak value. Compared with other bipolar pulse sources, this ultra-wideband differential pulse source combines the two pulse signal generation circuits into one, which not only simplifies the circuit design and occupies a smaller area, but also reduces the cost by half.

[0064] The ultra-wideband differential pulse sources for ground-penetrating radar described in all the above embodiments have the following advantages:

[0065] This ultra-wideband differential pulse source adds a first current-limiting resistor to the emitter of a BJT transistor and connects an adjustable capacitor in parallel across the energy storage capacitor. Adding the adjustable capacitor changes the capacitance value of the energy storage capacitor, thereby altering the discharge rate and achieving a narrower adjustable pulse width. Simultaneously, adjusting the value of the first current-limiting resistor changes the impedance of the discharge circuit, resulting in a larger adjustable pulse amplitude. Therefore, compared to traditional Marx circuits, this ultra-wideband differential pulse source exhibits a more ideal waveform, a larger adjustable pulse amplitude, lower cost, and a narrower adjustable pulse width, thus generating a bipolar differential pulse signal with a larger amplitude and narrower pulse width.

[0066] In addition, after adding a first current-limiting resistor to the primary BJT transistor, when the BJT transistor breaks down, the current flowing through the first current-limiting resistor will generate a voltage drop, thereby generating a positive pulse. This also eliminates the need to add a symmetrical circuit to generate a positive pulse, reducing the number of components used and thus lowering the cost.

[0067] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0068] 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 structure 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. An ultra-wideband differential pulse source for ground-penetrating radar, characterized in that, include: Power supply port, DC power supply module, trigger signal input port, positive polarity pulse output port, negative polarity pulse output port and differential pulse generation module; The differential pulse generation module includes: multiple transistor modules; each transistor module includes: a BJT transistor, an energy storage capacitor, an adjustment capacitor, and a first current-limiting resistor; the collector of the BJT transistor is connected to the energy storage capacitor; the adjustment capacitor is connected in parallel with the energy storage capacitor; the emitter of the BJT transistor is grounded through the first current-limiting resistor; Multiple transistor modules are connected in sequence. In two adjacent transistor modules, the collector of one BJT transistor is connected to the base and emitter of the other BJT transistor through an energy storage capacitor. The base of the first BJT transistor serves as the input terminal of the differential pulse generation module, the emitter of the first BJT transistor serves as the first output terminal of the differential pulse generation module, and the collector of the last BJT transistor serves as the second output terminal of the differential pulse generation module. The power supply port is connected to the collector of the BJT transistor in the transistor module via the DC power supply module; the trigger signal input port is connected to the input terminal of the differential pulse generation module; the first output terminal of the differential pulse generation module is connected to the positive polarity pulse output port; and the second output terminal of the differential pulse generation module is connected to the negative polarity pulse output port. This ultra-wideband differential pulse source adds a first current-limiting resistor to the emitter of the BJT transistor and connects an adjustable capacitor in parallel across the energy storage capacitor. The addition of the adjustable capacitor across the energy storage capacitor changes the capacitance value of the energy storage capacitor, thereby changing the capacitor discharge rate and thus obtaining a narrower adjustable pulse width. At the same time, adjusting the resistance value of the first current-limiting resistor changes the impedance value of the discharge circuit, thereby obtaining a larger adjustable pulse amplitude. The resistance of the first current-limiting resistor in the first transistor module of the differential pulse generation module is 51Ω, and the resistance of the first current-limiting resistor in the other transistor modules is 10kΩ.

2. The ultra-wideband differential pulse source for ground-penetrating radar according to claim 1, characterized in that, The DC power supply module includes: a boost power supply module and a filter module connected in sequence; the input terminal of the boost power supply module is connected to the power supply port; the filter module is connected to the collector of the BJT transistor in the transistor module. The boost power supply module is used to boost the voltage signal provided by the power supply port to obtain a boost signal; the filtering module is used to filter the boost signal.

3. The ultra-wideband differential pulse source for ground-penetrating radar according to claim 1, characterized in that, Also includes: Output resistance; One end of the output resistor is connected to the collector of the last BJT transistor in the differential pulse generation module and the negative pulse output port, and the other end of the output resistor is grounded.

4. The ultra-wideband differential pulse source for ground-penetrating radar according to claim 1, characterized in that, The transistor module also includes: a second current-limiting resistor; The DC power supply module is connected to the collector of the BJT transistor in the transistor module through the second current-limiting resistor.

5. The ultra-wideband differential pulse source for ground-penetrating radar according to claim 2, characterized in that, The filtering module includes three filter capacitors connected in parallel.

6. The ultra-wideband differential pulse source for ground-penetrating radar according to claim 1, characterized in that, Also includes: RC differentiating circuit; The trigger signal input port is connected to the input terminal of the differential pulse generation module through the RC differentiating circuit.

7. The ultra-wideband differential pulse source for ground-penetrating radar according to claim 4, characterized in that, The capacitance of both the energy storage capacitor and the regulating capacitor is 20pF; the resistance of the second current-limiting resistor is 51Ω.

8. The ultra-wideband differential pulse source for ground-penetrating radar according to claim 5, characterized in that, The capacitance of the filter capacitor is 100nF.

9. The ultra-wideband differential pulse source for ground-penetrating radar according to claim 1, characterized in that, The power supply port is V CC Power terminals.

10. The ultra-wideband differential pulse source for ground-penetrating radar according to claim 1, characterized in that, The trigger signal input port is a TTL signal terminal.

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