Balance detection device based on transformer

Abstract

The invention discloses a transformer-based balance detection device, which comprises a first photodiode and a second photodiode, and is characterized in that the anodes of the first photodiode and the second photodiode are grounded; the first resistor and the second resistor are respectively connected between the cathodes of the first photodiode and the second photodiode and a bias voltage source; the first isolation capacitor and the second isolation capacitor are respectively connected to the cathodes of the first photodiode and the second photodiode and the two ends of the primary side of the transformer; one end of the secondary side of the transformer is grounded, and the other end is connected to the input end of the transimpedance amplifier; compared with the balance detector realized by the traditional technology, the signal-to-noise ratio of the balance detector provided by the invention is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lidar, and particularly to a balanced detection device based on a transformer. Background Art

[0002] In coherent Doppler wind lidar, a high signal-to-noise ratio optoelectronic conversion technology is the balanced detection technology. In traditional balanced detection technology, two photodiodes with connected cathodes and anodes are used to suppress the common-mode signal and amplify the differential-mode signal. Subsequently, a transimpedance amplifier is used for the transimpedance amplification of the photocurrent to output a radio frequency signal. This radio frequency signal is then filtered and analog-to-digital converted, and the obtained digital waveform is used for the inversion calculation of the Doppler wind speed.

[0003] In practical applications, due to the difference in the mobility of free electrons and holes in the photodiode, their migration speeds are different. This causes a certain difference in the amplitude and delay of the current waveforms of the cathode and anode when the photodiode receives an optical signal. This difference results in the incomplete symmetry between the cathode current and the anode current, thus affecting the full amplification of the differential-mode signal and ultimately leading to the signal-to-noise ratio of the differential-mode signal not reaching the optimum. The loss of the signal-to-noise ratio will further affect the data accuracy in the signal processing process, especially in the wind speed inversion calculation, which will directly affect the final detection result. Therefore, reducing the signal distortion caused by the difference in the mobility of free electrons and holes and improving the symmetry of the differential-mode signal contribute to improving the signal-to-noise ratio of the balanced detection technology.

[0004] In addition, in traditional balanced detection technology, in order to bias the two photodiodes with a positive voltage and a negative voltage respectively, this requires the circuit to provide two power supplies, increasing the cost of the circuit. This is also where traditional balanced detection technology needs to be improved. Summary of the Invention

[0005] Object of the Invention: The object of the present invention is to provide a balanced detection device based on a transformer to overcome the problem of incomplete symmetry of the differential-mode signal caused by the difference in the mobility of free electrons and holes in traditional balanced detection technology.

[0006] Technical Solution: A balanced detection device based on a transformer according to the present invention includes: a first photodiode and a second photodiode, with the anodes of the first photodiode and the second photodiode grounded; a first resistor and a second resistor are respectively connected between the cathodes of the first photodiode (D1) and the second photodiode and a bias voltage source; a first isolation capacitor and a second isolation capacitor are respectively connected between the cathodes of the first photodiode and the second photodiode and both ends of the primary side of the transformer; one end of the secondary side of the transformer is grounded, and the other end is connected to the input end of a transimpedance amplifier.

[0007] Further, the transimpedance amplifier is configured to convert the differential-mode current signal output by the transformer into a radio-frequency voltage signal; the bias voltage source is a single-power-supply structure for providing a bias voltage with the same polarity to the two photodiodes.

[0008] Further, the first resistor and / or the second resistor is an adjustable resistor for adjusting the responsivity of the corresponding photodiode to match the symmetry of the output signal.

[0009] Further, the turns ratio of the primary side to the secondary side of the transformer is an adjustable parameter, and the amplification gain of the differential-mode signal is optimized by adjusting the turns ratio.

[0010] Further, a reference voltage module, which is connected to the anodes of the two photodiodes, dynamically adjusts the reference voltage of the anodes to control the operating state of the photodiodes.

[0011] Further, the cathodes of the first photodiode and the second photodiode are grounded, the anodes are respectively connected to the bias voltage source through resistors, and the reference voltage module is connected to the cathodes.

[0012] Further, the gain of the transimpedance amplifier is set to 30 kΩ, the voltage of the bias voltage source is 10 V, and the resistance values of the first resistor and the second resistor are 10 kΩ.

[0013] Further, the model of the transformer is Coilcraft WBC1-1, and the frequency band is 0.25 - 750 MHz.

[0014] A lidar system according to the present invention is provided with a balanced detection device of a transformer for receiving a laser echo signal and converting it into an electrical signal for Doppler wind speed inversion.

[0015] Advantages: Compared with the prior art, the present invention has the following remarkable advantages: It is powered by a single power supply, which simplifies the power circuit design and reduces the complexity and cost of the system. The single power supply can also reduce the interference of power noise on the signal, further improving the overall stability and accuracy of the system. By utilizing the function of the transformer to suppress the common-mode signals output by the two photodiodes, the signal-to-noise ratio is improved. The resistor connecting the photodiode to the bias voltage is an adjustable resistor, and the responsivity of the photodiode can be finely adjusted by adjusting the resistor value. The output current of the transformer can be adjusted by adjusting the turn ratio of the primary side and the secondary side of the transformer, so as to find the transformer with the optimal turn ratio and ultimately achieve the balanced detection with the best signal-to-noise ratio. When the cathodes of the two photodiodes output signals, the anodes can be commonly connected to a reference voltage. By quickly adjusting the reference voltage, the photodiode can be turned off for a period of time during operation, thus avoiding saturation caused by receiving too strong optical signals. The reference voltage can also keep the photodiode off usually and briefly turn it on with a higher bias voltage when needed to achieve enhanced photodetection. The test results show that the signal-to-noise ratio of this balanced detector is improved by about 0.2 dB compared with the balanced detector implemented by the traditional technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is the structural diagram of the present invention; Figure 2 is the structural diagram of the invention where the photodiode is connected to the reference voltage. DETAILED DESCRIPTION OF THE INVENTION

[0017] The technical solution of the present invention will be further described below with reference to the drawings.

[0018] As Figure 1As shown, an embodiment of the present invention provides a balance detection device based on a transformer. In this technology, two photodiodes, namely the first photodiode D1 and the second photodiode D2, are respectively equipped with the first resistor R1, the second resistor R2, the first isolation capacitor C1, and the second isolation capacitor C2. The cathodes of the two photodiodes are respectively connected to the bias voltage through resistors, and the anodes are grounded. The cathodes of the two photodiodes are respectively connected to the primary side of the transformer through isolation capacitors. One end of the secondary side of the transformer is grounded, and the other end is connected to a transimpedance amplifier. The transformer effectively suppresses the common-mode signals output by the two photodiodes, thereby improving the signal-to-noise ratio. The transimpedance amplifier receives the weak current signal output by the transformer, converts it into a radio frequency voltage signal, and amplifies the signal. Through this technical solution, both photodiodes output signals through the cathode, avoiding the problem of incomplete symmetry of the differential-mode signals caused by the difference in the mobility of free electrons and holes, thus achieving full amplification of the differential-mode signals and helping to improve the signal-to-noise ratio of the balance detection technology. In addition, compared with the traditional balance detector technology, this technology uses a single power supply method, simplifies the power circuit design, and reduces the complexity and cost of the system. The single power supply can also reduce the interference of power supply noise on the signal, further improving the overall stability and accuracy of the system.

[0019] The solution of the present invention can also be implemented such that the photodiodes output signals through the anodes. In this solution, the cathodes of the two photodiodes are grounded, and the anodes are respectively connected to the bias voltage through resistors.

[0020] There are differences in performance parameters between the two photodiodes, and the responsivities to the same optical signal are inconsistent. This will cause the amplitudes of the differential-mode signals output by the two photodiodes to be inconsistent during the balance detection process. To solve this problem, in the present invention, the resistors connecting the photodiodes to the bias voltage are adjustable resistors, and the responsivity of the photodiodes can be finely adjusted by adjusting the resistor size.

[0021] The output current size of the transformer can be adjusted by adjusting the turn ratio of the primary side and the secondary side of the transformer, so as to find a transformer with the optimal turn ratio and finally achieve balance detection with the best signal-to-noise ratio.

[0022] Based on the method of the present invention, when the cathodes of the two photodiodes output signals, the anodes can be commonly connected to a reference voltage. As Figure 2 shown, by quickly adjusting the reference voltage, the photodiodes can be turned off for a period of time during operation, thus avoiding saturation of the photodiodes due to receiving too strong optical signals. The reference voltage can also keep the photodiodes off usually and briefly turn them on with a higher bias voltage when needed to achieve enhanced photodetection. When the anodes of the two photodiodes output signals, the reference voltage is applied to the cathodes of the photodiodes.

[0023] Specific solution: As Figure 1 shown, the power supply is 10V, and the resistance values of resistors R1 and R2 are both 10 kohm. The capacitance values of capacitors C1 and C2 are both 10nF. The transimpedance amplifier is built with the OPA847IDBVR chip to achieve a transimpedance gain of 30 kohm. Photodiodes D1 and D2 with a response wavelength of 1064 nm are used as optical signal receiving elements, and the transformer model is Coilcraft WBC1-1L. The test results show that the signal-to-noise ratio of this balanced detector is improved by about 0.2 dB compared with the balanced detector implemented by traditional technology.

Claims

1. A transformer-based balance detection device, characterized in that, Comprising: A first photodiode (D1) and a second photodiode (D2), the anodes of the first photodiode (D1) and the second photodiode (D2) are grounded; a first resistor (R1) and a second resistor (R2) are respectively connected between the cathodes of the first photodiode (D1) and the second photodiode (D2) and a bias voltage source; a first isolation capacitor (C1) and a second isolation capacitor (C2) are respectively connected between the cathodes of the first photodiode (D1) and the second photodiode (D2) and both ends of the primary side of a transformer; one end of the secondary side of the transformer is grounded, and the other end is connected to the input end of a transimpedance amplifier.

2. The balanced detection device based on a transformer according to claim 1, characterized in that The transimpedance amplifier is configured to convert the differential-mode current signal output by the transformer into a radio frequency voltage signal; the bias voltage source is a single-power-supply structure for providing a bias voltage with the same polarity to the two photodiodes.

3. The balanced detection device based on a transformer according to claim 1, characterized in that, The first resistor (R1) and / or the second resistor (R2) is an adjustable resistor for adjusting the responsivity of the corresponding photodiode to match the symmetry of the output signal.

4. The balanced detection device based on a transformer according to claim 1, characterized in that, The turn ratio of the primary side to the secondary side of the transformer is an adjustable parameter, and the amplification gain of the differential-mode signal is optimized by adjusting the turn ratio.

5. The balanced detection device based on a transformer according to claim 1, characterized in that, A reference voltage module, the reference voltage module is connected to the anodes of the two photodiodes, and dynamically adjusts the reference voltage of the anodes to control the working state of the photodiodes.

6. The balanced detection device based on a transformer according to claim 1, characterized in that, The cathodes of the first photodiode (D1) and the second photodiode (D2) are grounded, the anodes are respectively connected to the bias voltage source through resistors and the reference voltage module is connected to the cathodes.

7. The balanced detection device based on a transformer according to claim 1, characterized in that, The gain of the transimpedance amplifier is set to 30 kΩ, the voltage of the bias voltage source is 10 V, and the resistance values of the first resistor (R1) and the second resistor (R2) are 10 kΩ.

8. The balanced detection device based on a transformer according to claim 1, wherein The model of the transformer is Coilcraft WBC1-1, and the frequency band is 0.25 - 750 MHz.

9. A lidar system, characterized in that, A balanced detection device provided with a transformer is used to receive a laser echo signal and convert it into an electrical signal for Doppler wind speed inversion.

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