Radio over fiber transmission circuit of high-voltage pulse

Abstract

The invention discloses a radio-over-fiber transmission circuit of a high-voltage pulse, and belongs to the technical field of radio-over-fiber transmission. A second resistor; a third resistor; the input end of the radio frequency buffer is electrically connected with the second end of the first resistor, and the cathode of the radio frequency buffer is electrically connected with the ground; the first end of the temperature compensation resistor is electrically connected with the output end of the radio frequency buffer; the first end of the first capacitor is electrically connected with the second end of the temperature compensation resistor; the first end of the first magnetic bead is electrically connected with the first end of the first capacitor; the first end of the second capacitor is electrically connected with the second end of the first magnetic bead; the first end of the second magnetic bead is electrically connected with the second end of the first capacitor, and the second end of the second magnetic bead is electrically connected with the second end of the second capacitor; the positive electrode of the semiconductor laser is electrically connected with the second end of the first capacitor, and the negative electrode is electrically connected with the ground. The circuit is simple and easy to implement, and is suitable for designing a rapid and low-cost system.

Description

Technical Field

[0001] The present invention relates to an optical radio frequency transmission circuit, specifically 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 transient discharge signals of high-voltage pulse type. It is required to stably transmit within a certain bandwidth, and at the same time be able to appropriately limit the input signal to meet the transmission and processing of the optical radio frequency output signal at the back end. In the process of this 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 temperature changes 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: An optical radio frequency transmission circuit for high-voltage pulses, comprising: A first resistor, the first end of which is used for inputting high-voltage pulses; 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; 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; 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; A temperature compensation resistor, the first end of which is electrically connected to the output end of the radio frequency buffer; A first capacitor, the first end of which is electrically connected to the second end of the temperature compensation resistor; A first bead, the first end of which is electrically connected to the first end of the first capacitor; A second capacitor, the first end of which is electrically connected to the second end of the first magnetic bead; A second magnetic bead, the first end of which is electrically connected to the second end of the first capacitor, and the second end of which is electrically connected to the second end of the second capacitor; A semiconductor laser, the positive electrode of which is electrically connected to the second end of the first capacitor, and the negative electrode of which is electrically connected to the ground.

[0006] The first resistor, the second resistor, and the third resistor are all low-temperature-drift and high-precision resistors.

[0007] The resistance value of the first resistor is 99 kΩ, the resistance value of the second resistor is 1 kΩ, and the resistance value of the third resistor is 1 MΩ.

[0008] The RF buffer includes: An operational amplifier, the non-inverting input terminal of which serves as the input terminal of the RF buffer, the output terminal of which is electrically connected to its inverting input terminal, and the output terminal of which serves as the output terminal of the RF buffer.

[0009] The operational amplifier is OPA659.

[0010] The semiconductor laser is a semiconductor photodiode.

[0011] The beneficial technical effects of the present invention are as follows: Compared with the prior art, the circuit of the present invention is simple and easy to implement, suitable for designing a fast and low-cost system. It adopts a full analog optoelectronic conversion design, has good responsivity, and can maintain good performance within a 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is the circuit schematic diagram of the present invention; Figure 2 is the characteristic curve diagram of the temperature-compensated resistor. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0013] The present invention will be further described below through specific embodiments, but not limited thereto.

[0014] See Figure 1 , an optical carrier radio frequency transmission circuit for high-voltage pulses of the present invention includes a first resistor R 1 , a second resistor R 2 , a third resistor R 3 , a temperature-compensated resistor R 4 , an operational amplifier OP, a first capacitor C 1, the second capacitor C 2 , the first bead FB 1 , the second bead FB 2 and the semiconductor laser LD.

[0015] The first end of the first resistor R 1 is used to input a high-voltage pulse.

[0016] The first end of the second resistor R 2 is electrically connected to the second end of the first resistor R 1 , and the second end of the second resistor R 2 is electrically connected to the ground.

[0017] The first end of the third resistor R 3 is electrically connected to the second end of the first resistor R 1 , and the second end of the third resistor R 3 is electrically connected to the ground.

[0018] The non-inverting input terminal of the operational amplifier OP is electrically connected to the second end of the first resistor R 1 , and the output terminal of the operational amplifier OP is electrically connected to the inverting input terminal of the operational amplifier OP.

[0019] The first end of the temperature-compensating resistor R 4 is electrically connected to the output terminal of the operational amplifier OP.

[0020] The first end of the first capacitor C 1 is electrically connected to the second end of the temperature-compensating resistor R 4 .

[0021] The first end of the first bead FB 1 is electrically connected to the first end of the first capacitor C 1 .

[0022] The first end of the second capacitor C 2 is electrically connected to the second end of the first bead FB 1 .

[0023] The first end of the second bead FB 2 is electrically connected to the second end of the first capacitor C 1 , and the second end of the second bead FB 2 is electrically connected to the second end of the second capacitor C 2 .

[0024] The positive electrode of the semiconductor laser LD is electrically connected to the second end of the first capacitor C 1 , and the negative electrode of the semiconductor laser LD is electrically connected to the ground. The semiconductor laser can be a semiconductor photodiode.

[0025] In this embodiment, as Figure 1As shown, the first resistor R 1 , the second resistor R 2 , and the third resistor R 3 form a high-precision low-temperature-drift voltage-dividing network. The first resistor R 1 , the second resistor R 2 , and the third resistor R 3 all adopt low-temperature-drift high-precision resistors to ensure that the resistance value change of its high-precision low-temperature-drift voltage-dividing 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, with the unit of ppm / °C, and the present invention requires ±5 ppm / °C; the high precision is quantified by the tolerance, with the unit of percentage, and the present invention requires ±0.1%. The operational amplifier OP forms a radio frequency buffer. The non-inverting input terminal of the operational amplifier OP serves as the input terminal of the radio frequency buffer, and the output terminal of the operational amplifier OP serves as the output terminal of the radio frequency buffer. The temperature-compensating resistor R 4 , the first capacitor C 1 , the second capacitor C 2 , the first bead FB 1 , and the second bead FB 2 form an impedance matching network.

[0026] According to the voltage division formula (1), when the ratio of the first resistor R 1 to the second resistor R 2 is 99:1, the input signal, after being voltage-divided by the high-precision low-temperature-drift voltage-dividing network, the voltage drop across the second resistor R 2 is of the input signal, and the level of the second resistor R 2 is reduced by 100 times compared to the input signal. Therefore, the magnitudes of the first resistor R 1 and the second resistor R 2 should be selected as resistance values in the kiloohm range according to the required voltage drop. 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.

[0027] (1) In the voltage division formula (1), R 1 , R 2 are the series resistance values, V in is the total input voltage, and V Ri is the voltage across the voltage-divided voltage (across R 2 ).

[0028] The third resistor R 3 is the parallel resistor of the second resistor R 2 . Compared with the dynamic impedance of the subsequent radio frequency buffer, the role of the third resistor R 3 here is to provide a static impedance to the ground, thereby reducing the third resistor R3 The voltage division effect on the output voltage of the subsequent stage, so the resistance value of the third resistor R 3 should reach the megohm level. Since the resistance value of the third resistor R 3 is much larger than the resistance value of the second resistor R 2 , when the third resistor R 3 is infinite, the third resistor R 3 is equivalent to an open circuit here. However, due to its fixed resistance value, the non-inverting input terminal of the RF buffer in the subsequent stage circuit has a static high resistance 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 greater the thermal noise. For high-speed pulses, its bandwidth is relatively narrow, so the thermal noise is relatively 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 effect.

[0029] (2) In the Johnson-Nyquist formula (2), Δf is the thermal noise bandwidth, R is the resistance value of the resistor, 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.

[0030] The function of the RF buffer is to provide a low-resistance output impedance to drive the load, while isolating the front and rear end circuits to prevent the mutual influence between the load circuit and the front stage circuit, thereby stabilizing the performance of the circuit.

[0031] 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 division network. In actual 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 to 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. Its features include: high slew rate: 2550 V / μs. The high slew rate enables the processing of high-speed changing signals, performs excellently 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-frequency signals.

[0032] It can be seen that a temperature-compensated resistor R is connected to the output terminal of the RF buffer 4, according to the appendix Figure 2 As shown, where the logarithmic coordinate unit is dB, it can be seen that its characteristic is that when the temperature rises, the attenuation becomes smaller. Similarly, when the temperature drops, the attenuation becomes larger. Select the temperature-compensated resistor R 4 The purpose 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 temperature-compensated resistors with different characteristics, stable signal transmission can be guaranteed.

[0033] At the output terminal of the temperature-compensated resistor R 4 two parallel capacitors are connected, namely the first capacitor C 1 and the second capacitor C 2 . They are connected to the positive pole 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 previous-stage circuit. Here, the first capacitor C 1 and the second capacitor C 2 are connected in series through two magnetic beads, namely the first magnetic bead FB 1 and the second magnetic bead FB 2 . The purpose of using the first magnetic bead FB 1 and the second magnetic bead FB 2 is to improve the high-frequency response, suppress high-frequency noise, and reduce distortion. At the same time, the first capacitor C 1 and the second capacitor C 2 act as a good isolation function. The other purpose of using the first capacitor C 1 and the second capacitor C 2 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 R 4 , the first capacitor C 1 , the second capacitor C 2 , the first magnetic bead FB 1 , and the second magnetic bead FB 2 combine to form an impedance matching network.

[0034] Finally, the semiconductor laser LD converts the electrical signal into an optical signal for output. Figure 1 In out , V

[0035] 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 requirement for its ADC chip is extremely high, and the circuit is complex. The present invention adopts a fully analog method, which simplifies the circuit and has the characteristics of high precision, strong reliability, and strong maintainability of the simple circuit, and can compress the circuit space to the greatest extent in the application scenario.

[0036] Based on a high-precision low-temperature-drift voltage-dividing network, the present invention provides the linear step-down ability of high-voltage signals and linearity within the bandwidth. By introducing a radio frequency buffer and an impedance matching network, the signal transmission quality and the stability of the signal at different temperatures are ensured. It can support signal inputs of 100V or even higher levels, provide a stable and high-quality optical carrier radio frequency signal output, and adapt to different application scenarios.

[0037] The high-precision low-temperature-drift voltage-dividing network of the present invention uses a low-temperature-drift resistance 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.

[0038] 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 to achieve impedance matching with the semiconductor laser LD. Using a temperature-compensated resistor R 4 can ensure the signal fluctuation stability 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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