Optical Carrier Radio Frequency Transmission Circuit for High-Voltage Pulse

Abstract

The present invention discloses an optical carrier radio frequency transmission circuit for high-voltage pulses, belonging to the technical field of optical carrier radio frequency transmission. The circuit includes a first resistor; a second resistor; a third resistor; a radio frequency buffer, whose input end is electrically connected to the second end of the first resistor, and whose negative pole is electrically connected to the ground; a temperature-compensated resistor, whose first end is electrically connected to the output end of the radio frequency buffer; a first capacitor, whose first end is electrically connected to the second end of the temperature-compensated resistor; a first bead, whose first end is electrically connected to the first end of the first capacitor; a second capacitor, whose first end is electrically connected to the second end of the first bead; a second bead, whose first end is electrically connected to the second end of the first capacitor, and whose second end is electrically connected to the second end of the second capacitor; a semiconductor laser, whose positive pole is electrically connected to the second end of the first capacitor, and whose negative pole is electrically connected to the ground. The circuit of the present invention is simple and easy to implement, and is suitable for designing a fast and low-cost system.

Description

Technical Field

[0001] The present invention relates to an optical radio frequency transmission circuit, and particularly to an optical radio frequency transmission circuit for high-voltage pulses. Background Art

[0002] In the special application field of optical radio frequency signal transmission, the radio frequency level of the source signal input may be very high, up to 100V, but its source signal loading capacity is weak, such as the transient discharge signal of the high-voltage pulse type. It is required to be stably transmitted within a certain bandwidth, and at the same time, the input signal can be appropriately limited to meet the transmission and processing of the optical radio frequency output signal at the back end. In the process of optical radio frequency signal transmission, it is necessary to transmit the transient discharge signal through an optical medium by photoelectric conversion, and provide a linear low-voltage and high-linear radio frequency signal in its remote optical receiving device. Therefore, the design of the optical transmitting device is particularly important in this process.

[0003] Conventional optical radio frequency signal transmission modules cannot directly process high input voltage signals. High input levels are likely to cause signal distortion, equipment damage or difficult matching. Existing solutions are insufficient in terms of high dynamic range, linearity or reliability. In the transmission of high-level radio frequency signals (such as in the fields of power systems, radio and communication, etc.), there is an urgent need for safe and reliable signal processing and optical transmission methods. Traditional optical radio frequency transmission modules often generate linear distortion in the voltage dividing network due to high-voltage signals, especially high-frequency harmonic components, and the waveform distortion caused by its temperature change will affect signal integrity. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides an optical radio frequency transmission circuit for high-voltage pulses, which adopts a full-analog method, simplifies the circuit, and has the characteristics of high precision, strong reliability, simple circuit and strong maintainability, and can compress the circuit space to the greatest extent in the application scenario.

[0005] The technical solution of the present invention is as follows:

[0006] An optical radio frequency transmission circuit for high-voltage pulses, comprising:

[0007] A first resistor, the first end of which is used for inputting high-voltage pulses;

[0008] A second resistor, the first end of which is electrically connected to the second end of the first resistor, and the second end of which is electrically connected to the ground;

[0009] A third resistor, the first end of which is electrically connected to the second end of the first resistor, and the second end of which is electrically connected to the ground;

[0010] A radio frequency buffer, the input end of which is electrically connected to the second end of the first resistor, and the negative electrode of which is electrically connected to the ground;

[0011] A temperature-compensated resistor, with its first end electrically connected to the output end of the RF buffer;

[0012] A first capacitor, with its first end electrically connected to the second end of the temperature-compensated resistor;

[0013] A first bead, with its first end electrically connected to the first end of the first capacitor;

[0014] A second capacitor, with its first end electrically connected to the second end of the first bead;

[0015] A second bead, with its first end electrically connected to the second end of the first capacitor and its second end electrically connected to the second end of the second capacitor;

[0016] A semiconductor laser, with its positive pole electrically connected to the second end of the first capacitor and its negative pole electrically connected to ground.

[0017] The first resistor, the second resistor, and the third resistor are all low-temperature-drift high-precision resistors.

[0018] The resistance value of the first resistor is 99k, the resistance value of the second resistor is 1k, and the resistance value of the third resistor is 1M.

[0019] The RF buffer includes:

[0020] An operational amplifier, with its non-inverting input terminal serving as the input terminal of the RF buffer, its output terminal electrically connected to its inverting input terminal, and its output terminal serving as the output terminal of the RF buffer.

[0021] The operational amplifier is OPA659.

[0022] The semiconductor laser is a semiconductor photodiode.

[0023] The beneficial technical effects of the present invention are as follows:

[0024] Compared with the prior art, the circuit of the present invention is simple and easy to implement, suitable for designing fast and low-cost systems. It adopts a full analog optoelectronic conversion design, has good responsivity, and can maintain good performance within a relatively wide frequency range. Especially in the application of pulse signals, the frequency response is not significantly limited. The circuit of the present invention is simple, highly maintainable, low-cost, and highly reliable. The present invention is a pure analog optoelectronic conversion circuit, without a digital-to-analog conversion circuit, has high in-band stability, has a self-compensation characteristic, and strong temperature stability. Description of the Drawings

[0025] Figure 1 is the circuit schematic diagram of the present invention;

[0026] Figure 2 is the characteristic curve graph of the temperature-compensated resistor. Detailed Embodiments

[0027] The present invention will be further described below through specific embodiments, but not limited thereto.

[0028] Refer to Figure 1 , an optical carrier radio frequency transmission circuit for high-voltage pulses of the present invention includes a first resistor R1, a second resistor R2, a third resistor R3, a temperature compensation resistor R4, an operational amplifier OP, a first capacitor C1, a second capacitor C2, a first magnetic bead FB1, a second magnetic bead FB2, and a semiconductor laser LD.

[0029] The first end of the first resistor R1 is used to input high-voltage pulses.

[0030] The first end of the second resistor R2 is electrically connected to the second end of the first resistor R1, and the second end of the second resistor R2 is electrically connected to the ground.

[0031] The first end of the third resistor R3 is electrically connected to the second end of the first resistor R1, and the second end of the third resistor R3 is electrically connected to the ground.

[0032] The non-inverting input terminal of the operational amplifier OP is electrically connected to the second end of the first resistor R1, and the output terminal of the operational amplifier OP is electrically connected to the inverting input terminal of the operational amplifier OP.

[0033] The first end of the temperature compensation resistor R4 is electrically connected to the output terminal of the operational amplifier OP.

[0034] The first end of the first capacitor C1 is electrically connected to the second end of the temperature compensation resistor R4.

[0035] The first end of the first magnetic bead FB1 is electrically connected to the first end of the first capacitor C1.

[0036] The first end of the second capacitor C2 is electrically connected to the second end of the first magnetic bead FB1.

[0037] The first end of the second magnetic bead FB2 is electrically connected to the second end of the first capacitor C1, and the second end of the second magnetic bead FB2 is electrically connected to the second end of the second capacitor C2.

[0038] The positive electrode of the semiconductor laser LD is electrically connected to the second end of the first capacitor C1, and the negative electrode of the semiconductor laser LD is electrically connected to the ground. The semiconductor laser can be a semiconductor photodiode.

[0039] In this embodiment, as Figure 1As shown in the figure, the first resistor R1, the second resistor R2, and the third resistor R3 form a high-precision low-temperature-drift voltage division network. The first resistor R1, the second resistor R2, and the third resistor R3 all use low-temperature-drift high-precision resistors to ensure that the resistance value change of its high-precision low-temperature-drift voltage division network due to temperature is not too large. For the low-temperature-drift high-precision resistor of the present invention, the low-temperature drift is measured by the temperature coefficient, and the unit is ppm / °C. The present invention requires ±5 ppm / °C; the high precision is quantified by the tolerance, and the unit is a percentage. The present invention requires ±0.1%. The operational amplifier OP constitutes a radio frequency buffer. The non-inverting input terminal of the operational amplifier OP is used as the input terminal of the radio frequency buffer, and the output terminal of the operational amplifier OP is used as the output terminal of the radio frequency buffer. The temperature compensation resistor R4, the first capacitor C1, the second capacitor C2, the first bead FB1, and the second bead FB2 form an impedance matching network.

[0040] According to the voltage division formula (1), when the ratio of the first resistor R1 to the second resistor R2 is 99:1, the input signal is divided by the high-precision low-temperature-drift voltage division network, and the voltage drop across the second resistor R2 is of the input signal, and the level of the second resistor R2 is reduced by 100 times compared with the input signal. Therefore, the magnitudes of the first resistor R1 and the second resistor R2 should be selected according to the required voltage drop magnitude to be in the range of kiloohms. Assuming that when a 100V high-speed pulse signal is input, resistors of 99k and 1k can be correspondingly selected to ensure that the selected resistors meet their power capacity requirements.

[0041] (1)

[0042] In the voltage division formula (1), R1 and R2 are the resistance values of the series resistors, V in is the total input voltage, V Ri is the voltage across the voltage-divided voltage (across R2).

[0043] The third resistor R3 is a parallel resistor of the second resistor R2. Compared with the dynamic impedance of the subsequent radio frequency buffer, the role of the third resistor R3 here is to provide a static impedance to the ground, thereby reducing the voltage division effect of the third resistor R3 on the output voltage of the subsequent stage. Therefore, the resistance value of the third resistor R3 should reach the megohm level. Since the resistance value of the third resistor R3 is much larger than the resistance value of the second resistor R2, when the third resistor R3 is infinite, the third resistor R3 is equivalent to an open circuit here. However, due to its fixed resistance value, the non-inverting input terminal of the radio frequency buffer of the subsequent circuit is a static high impedance to the ground. According to the Johnson-Nyquist formula (2), the larger the resistance value of the resistor, the larger the mean square value of the thermal noise voltage of the resistor. Its physical meaning is that the resistance value of the resistor is related to the thermal noise of the resistor, and the larger the resistance value of the resistor, the larger the thermal noise. For high-speed pulses, its bandwidth is relatively narrow, so the thermal noise is small. According to actual tests, when the pulse width is in the millisecond level, it is more appropriate to use a resistor with a resistance value of 1M after weighing the noise influence.

[0044] (2)

[0045] In Johnson - Nyquist formula (2), Δf is the thermal noise bandwidth, R is the resistance value, T is the absolute temperature, k is the Boltzmann constant, and v is the mean square value of the thermal noise voltage of the resistor.

[0046] The function of the RF buffer is to provide a low - impedance output impedance to drive the load, while isolating the front - end and back - end circuits to prevent the mutual influence between the load circuit and the front - stage circuit, thereby stabilizing the performance of the circuit.

[0047] It should be noted that the power supply of the RF buffer should provide an appropriate bias in combination with the signal after being divided by a high - precision low - temperature - drift voltage - dividing network. In practical applications, the bias should be greater than 20% - 30% of the input signal level amplitude to ensure that the signal operates within the power supply rail and avoid signal distortion. When applied to high - speed pulse transient response, it is recommended to select a high - performance amplifier such as OPA659 from TI. Its excellent performance can meet most transient response applications, and its features include: high slew rate: 2550 V / μs. The high slew rate enables the processing of rapidly changing signals, performs well in high - frequency signal amplification and processing, can significantly improve the pulse response, and is suitable for time - domain and pulse - type applications with high requirements for signal integrity; low noise: the input voltage noise is as low as 8.9 nV / Hz 1 / 2 , combined with the high input impedance and low bias current provided by the JFET input stage, can achieve extremely low integrated noise, which is beneficial to improving the quality and accuracy of the signal; high gain - bandwidth product: the gain - bandwidth product of 350 MHz can provide stable amplification performance within a wide frequency band range, which is of great significance for applications that need to process wide - band signals.

[0048] It can be seen that a temperature - compensated resistor R4 is connected to the output end of the RF buffer. As shown in the appendix Figure 2 , where the logarithmic coordinate unit is dB. It can be seen that its characteristic is that when the temperature rises, the attenuation becomes smaller, and similarly, when the temperature drops, the attenuation becomes larger. The purpose of selecting the temperature - compensated resistor R4 here is to ensure that within a certain temperature range of the entire device, the influence of temperature stability on the signal is minimized. By selecting different characteristic temperature - compensated resistors, the stable transmission of the signal can be guaranteed.

[0049] At the output end of the temperature-compensated resistor R4, two parallel-connected capacitors, namely the first capacitor C1 and the second capacitor C2, are connected to the positive electrode of the semiconductor laser LD. Their function is to isolate the DC signal and ensure that the bias DC of the semiconductor laser LD does not affect the front-stage circuit. Here, the first capacitor C1 and the second capacitor C2 are connected in series through two magnetic beads, namely the first magnetic bead FB1 and the second magnetic bead FB2. The purpose of using the first magnetic bead FB1 and the second magnetic bead FB2 here is to improve the high-frequency response, suppress high-frequency noise, and reduce distortion. At the same time, the first capacitor C1 and the second capacitor C2 act as a good isolation function. Another purpose of using the first capacitor C1 and the second capacitor C2 is that at low frequencies, a capacitor with a larger capacitance value is required to meet the low-frequency response. Therefore, the lower the frequency, the larger the capacitance value should be selected. Here, the temperature-compensated resistor R4, the first capacitor C1, the second capacitor C2, the first magnetic bead FB1, and the second magnetic bead FB2 are combined into an impedance matching network.

[0050] Finally, the semiconductor laser LD converts the electrical signal into an optical signal for output. Figure 1 In, V out is the output signal.

[0051] In the prior art, a digital-to-analog conversion chip is usually used to convert the optical carrier radio frequency signal into a digital signal for transmission. The accuracy requirements for its ADC chip are extremely high, and the circuit is complex. The present invention adopts a fully analog method, simplifies the circuit, and has the characteristics of high precision, strong reliability, simple circuit, and strong maintainability. It can compress the circuit space to the greatest extent in the application scenario.

[0052] The present invention is based on a high-precision low-temperature-drift voltage-dividing network, providing the linear step-down ability of high-voltage signals and the linearity within the bandwidth. By introducing a radio frequency buffer and an impedance matching network, it ensures the signal transmission quality and the stability of the signal at different temperatures. It can support the input of signals with a level of 100V or even higher, provide a stable high-quality optical carrier radio frequency signal output, and adapt to different application scenarios.

[0053] The high-precision low-temperature-drift voltage-dividing network of the present invention uses a low-temperature-drift resistor voltage-dividing method to perform signal level conversion, retains the characteristics of analog signals, does not require analog-to-digital conversion, and reduces signal noise.

[0054] The radio frequency buffer and impedance matching network of the present invention are used for high-low voltage pulse isolation on the one hand and for improving the load-carrying capacity of the backend on the other hand. Its matching network is used to ensure the in-band impedance stability of the radio frequency buffer and at the same time achieve impedance matching with the semiconductor laser LD. Using the temperature-compensated resistor R4 can ensure the stability of the signal fluctuation within a certain temperature range, thereby realizing the stable transmission of the signal.

Claims

1. A high voltage pulse optical radio frequency transmission circuit, characterized in that: include: A first resistor, a first end of which is used to input a high voltage pulse; a second resistor, a first end of which is electrically connected to the second end of the first resistor, and a second end of which is electrically connected to ground; a third resistor, a first end of which is electrically connected to the second end of the first resistor, and a second end of which is electrically connected to the ground; a radio frequency buffer, an input end of which is electrically connected to the second end of the first resistor, and a negative electrode of which is electrically connected to the ground; a temperature compensation resistor, a first end of which is electrically connected to the output end of the RF buffer; A first capacitor, a first end of which is electrically connected to a second end of the temperature compensation resistor; A first magnetic bead, a first end of which is electrically connected to a first end of a first capacitor; A second capacitor, a first end of which is electrically connected to the second end of the first magnetic bead; A second magnetic bead, a first end of which is electrically connected to the second end of the first capacitor, and a second end of which is electrically connected to the second end of the second capacitor; The semiconductor laser has an anode electrically connected to the second end of the first capacitor and a cathode electrically connected to the ground.

2. The high-voltage pulse optical radio frequency transmission circuit according to claim 1, characterized in that: The first resistor, the second resistor and the third resistor are all low temperature drift and high precision resistors.

3. The high-voltage pulse optical radio frequency transmission circuit according to claim 1, characterized in that: The resistance value of the first resistor is 99k, the resistance value of the second resistor is 1k, and the resistance value of the third resistor is 1M.

4. The high-voltage pulse optical radio frequency transmission circuit according to claim 1, characterized in that: The radio frequency buffer comprises: The operational amplifier has a non-inverting input terminal as the input terminal of the radio frequency buffer, an output terminal electrically connected to its inverting input terminal, and an output terminal as the output terminal of the radio frequency buffer.

5. The high-voltage pulse optical radio frequency transmission circuit according to claim 4, characterized in that: The operational amplifier is OPA659.

6. The high-voltage pulse optical radio frequency transmission circuit according to claim 1, characterized in that: The semiconductor laser is a semiconductor photodiode.

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