A balance detection device based on transformer

Abstract

The present invention discloses a transformer-based balanced detection device, comprising: a first photodiode and a second photodiode, wherein the anodes of the first photodiode and the second photodiode are grounded; a first resistor and a second resistor are respectively connected between the cathodes of the first photodiode 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 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; the signal-to-noise ratio of the balanced detector of the present invention is greatly improved compared with the balanced detector implemented by traditional technology.

Description

Technical Field

[0001] The present invention relates to the field of laser radar technology, and in particular to a transformer-based balanced detection device. Background Art

[0002] In coherent Doppler wind lidar, balanced detection is a photoelectric conversion technology that provides a high signal-to-noise ratio. Traditional balanced detection uses two photodiodes connected to the cathode and anode to suppress common-mode signals and amplify differential-mode signals. The photocurrent is then amplified by a transimpedance amplifier (TIA) to output an RF signal. This RF signal is then filtered and converted to analog-to-digital. The resulting digital waveform is used to invert Doppler wind speed.

[0003] In practical applications, the difference in mobility between free electrons and holes in photodiodes leads to different migration speeds. This results in a certain difference in the amplitude and delay of the cathode and anode current waveforms when the photodiode receives the light signal. This difference causes the cathode and anode currents to be asymmetrical, thus affecting the full amplification of the differential-mode signal and ultimately resulting in a suboptimal signal-to-noise ratio (SNR) of the differential-mode signal. This loss in SNR further affects data accuracy during signal processing, particularly in wind speed inversion calculations, which directly impacts the final detection results. Therefore, reducing the signal distortion caused by this difference in free electron and hole mobility and improving the symmetry of the differential-mode signal can help improve the SNR of balanced detection technology.

[0004] Furthermore, in traditional balanced detection technology, the two photodiodes require a positive bias voltage and a negative bias voltage, respectively. This requires the circuit to provide two power supplies, increasing circuit costs. This is also an area where traditional balanced detection technology needs improvement. Summary of the Invention

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

[0006] Technical solution: The transformer-based balance detection device described in the present invention includes: a first photodiode and a second photodiode, the anodes of the first photodiode and the second photodiode are 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 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.

[0007] Furthermore, 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 bias voltages of the same polarity to the two photodiodes.

[0008] Furthermore, the first resistor and / or the second resistor is an adjustable resistor, which is used to adjust the responsivity of the corresponding photodiode to match the symmetry of the output signal.

[0009] Furthermore, the turns ratio between the primary side and 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] Furthermore, a reference voltage module is provided, which 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.

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

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

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

[0014] The laser radar system described in the present invention is provided with a balanced detection device of a transformer, which is used to receive laser echo signals and convert them into electrical signals for Doppler wind speed inversion.

[0015] Beneficial Effects: Compared to existing technologies, the present invention offers the following significant advantages: Single-power supply simplifies power supply circuit design, reducing system complexity and cost. Single-power supply also reduces signal interference from power supply noise, further improving overall system stability and accuracy. A transformer is used to suppress the common-mode signal output by the two photodiodes, thereby improving the signal-to-noise ratio. The resistor connecting the photodiode to the bias voltage is an adjustable resistor, allowing the photodiode's responsivity to be fine-tuned by adjusting the resistor's value. The transformer's output current can be adjusted by adjusting the turns ratio between the primary and secondary sides of the transformer, thereby finding the transformer with the optimal turns ratio and ultimately achieving balanced detection with the best signal-to-noise ratio. When the cathodes of the two photodiodes output signals, their anodes can be connected to a common reference voltage. Rapidly adjusting the reference voltage can shut off the photodiodes for a period of time during operation, preventing them from saturating due to excessively strong light signals. The reference voltage also allows the photodiodes to be turned off normally and briefly turned on with a higher bias voltage when needed, achieving enhanced photodetection. 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 achieved with traditional technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural diagram of the present invention;

[0017] Figure 2 This is a structural diagram of the invention in which a photodiode is connected to a reference voltage. DETAILED DESCRIPTION

[0018] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0019] like Figure 1As shown, an embodiment of the present invention provides a transformer-based balanced detection device. This technology utilizes two photodiodes, namely a first photodiode D1 and a second photodiode D2, each equipped with a first resistor R1, a second resistor R2, and a first isolation capacitor C1, and a second isolation capacitor C2. The cathodes of the two photodiodes are connected to a bias voltage via resistors, and the anodes are grounded. The cathodes of the two photodiodes are connected to the primary side of the transformer via 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 signal 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 an RF voltage signal, and amplifies the signal. Through this technical solution, both photodiodes output signals through their cathodes, avoiding the problem of asymmetric differential-mode signals caused by differences in the mobility of free electrons and holes. This allows for full amplification of the differential-mode signal, helping to improve the signal-to-noise ratio of balanced detection technology. Furthermore, compared to traditional balanced detector technology, this technology uses a single power supply, simplifying the power supply circuit design and reducing system complexity and cost. 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.

[0020] The solution of the present invention can also be implemented as the photodiode outputting signals through the anode. In this solution, the cathodes of the two photodiodes are grounded, and the anodes are respectively connected to the bias voltage through resistors.

[0021] The performance parameters of two photodiodes differ, resulting in inconsistent responsivity to the same light signal. This can lead to inconsistent amplitudes of the differential-mode signals output by the two photodiodes during balanced detection. To address this issue, the present invention uses an adjustable resistor connecting the photodiode to the bias voltage. The responsivity of the photodiode can be fine-tuned by adjusting the resistor's value.

[0022] The output current of the transformer can be adjusted by adjusting the turns ratio of the primary and secondary sides of the transformer, thereby finding the transformer with the optimal turns ratio and ultimately achieving balanced detection with the best signal-to-noise ratio.

[0023] Based on the method of the present invention, when the cathodes of the two photodiodes output signals, the anodes can be connected to a common reference voltage, such as Figure 2 As shown in the figure, by quickly adjusting the reference voltage, the photodiode can be turned off for a period of time during operation, thereby preventing the photodiode from receiving excessive light signals and becoming saturated. The reference voltage can also shut down the photodiode normally and briefly turn it on with a higher bias voltage when needed, achieving enhanced photodetection. When the anodes of the two photodiodes output signals, the reference voltage is applied to the cathodes of the photodiodes.

[0024] Specific plan: Figure 1 As shown, the power supply is 10V, and resistors R1 and R2 are both 10 kohm. Capacitors C1 and C2 are both 10nF. The transimpedance amplifier is constructed using the OPA847IDBVR chip, achieving a transimpedance gain of 30 kohm. Photodiodes D1 and D2 with a response wavelength of 1064 nm serve as optical signal receivers, and the transformer is a Coilcraft WBC1-1L. Test results show that the signal-to-noise ratio of this balanced detector is approximately 0.2 dB higher than that of balanced detectors implemented using traditional technology.

Claims

1. A transformer-based balance detection device, characterized in that: include: 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 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.

2. The transformer-based balance detection device 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 bias voltages of the same polarity to the two photodiodes.

3. The transformer-based balance detection device according to claim 1, characterized in that: The first resistor (R1) and / or the second resistor (R2) are adjustable resistors for adjusting the responsivity of the corresponding photodiode to match the symmetry of the output signal.

4. The transformer-based balance detection device according to claim 1, characterized in that: The turns ratio between the primary side and 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.

5. The transformer-based balance detection device according to claim 1, characterized in that: 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 transformer-based balance detection device 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.

7. The transformer-based balance detection device according to claim 1, characterized in that: The transformer model is Coilcraft WBC1-1, and the frequency band is 0.25-750MHz.

8. A laser radar system, characterized in that: A transformer-based balanced detection device according to any one of claims 1 to 7, configured to receive a laser echo signal and convert it into an electrical signal for Doppler wind speed inversion.

Images