An adaptive gain adjustment APD

Abstract

An adaptive gain adjustment APD. The present invention discloses an APD with autonomous gain tuning and high stability, comprising a voltage tuning control unit A, a boost circuit unit, a signal output unit C, and a reference signal unit D. The voltage tuning control unit A includes ADC acquisition, main control chip calculation, and DAC output control subunits. The boost circuit unit includes a DC / DC boost circuit signal channel and a DC / DC boost circuit reference channel. The signal output unit C includes a signal APD and a signal filtering and amplifying circuit. The reference signal unit D includes a reference light source, a reference APD, and a signal filtering and amplifying circuit. The reference light source outputs light waves to the reference APD. The reference APD output signal is filtered and amplified before being sent to the ADC for acquisition. The ADC acquisition is connected to the main control chip. The main control chip is connected to the DAC output and then output to the signal channel and reference channel of the DC / DC boost circuit. The DC / DC boost circuit reference channel is connected to the positive pole of the reference APD. The DC / DC boost circuit signal channel is connected to the positive pole of the signal APD. The negative pole signal of the signal APD is filtered and amplified before being output.

Description

Technical Field

[0001] The present invention belongs to the field of optoelectronic technology, and in particular relates to an adaptive gain adjustment APD, in particular to an APD with autonomous gain tuning and high stability. Background Art

[0002] Avalanche photodiodes (APDs) are important devices for detecting weak light signals. They utilize the avalanche multiplication effect of carriers at the breakdown voltage to achieve high gain. APDs are a crucial bridge in photoelectric signal conversion and are widely used in a variety of applications requiring weak light detection.

[0003] According to theoretical research, the relationship between the multiplication factor M of the avalanche photodetector and the bias voltage V is:

[0004]

[0005] Where V B is the breakdown voltage; n is a parameter related to the specific material of the detector and can be considered as a fixed value near room temperature.

[0006] The breakdown voltage V B The relationship between the temperature T is

[0007] V B (T)=V B (T0)[1+a(T-T0)] (2)

[0008] Where a is a constant, T is the actual temperature, T0 is the reference temperature, V B (T0) is the breakdown voltage of the avalanche photodetector at the reference temperature T0, V B (T) is the breakdown voltage of the avalanche photodetector at temperature T.

[0009] In practical applications, the change of ambient temperature T has a great influence on the gain characteristics of APD. When the temperature T increases, the breakdown voltage V B If the APD's reverse bias operating voltage V remains unchanged, the APD's photodetection gain M will decrease, reducing sensitivity. This means that for the same input optical power, the APD's output voltage signal will vary under different temperature conditions, leading to distortion of the acquired optical signal. Applications that require the absolute value of optical power changes place high demands on the photodetector's gain stability.

[0010] To achieve stable APD gain, it's necessary to compensate for the APD's reverse-bias operating voltage at different temperatures. Several compensation methods exist. One approach involves testing the APD's breakdown voltage or its relationship to temperature through full-temperature modeling. In practice, a temperature lookup table is used to output the corresponding APD reverse-bias operating voltage to achieve stable gain. However, this approach requires testing the APD's breakdown voltage at different temperatures, which is labor-intensive and inefficient.

[0011] A method for tuning the reverse bias operating voltage of an APD using a thermistor network feedback system. This method stabilizes the APD gain by aligning the thermistor's temperature sensitivity with that of the APD's breakdown voltage. However, due to the nonlinearity of the thermistor feedback, the APD gain stabilization accuracy is limited over all temperature conditions.

[0012] One approach, using temperature control, requires real-time measurement of the APD die temperature. Since APDs typically lack integrated temperature sensors, obtaining true temperature values is difficult. Furthermore, this approach draws high currents at high and low temperatures, resulting in high module power consumption. This increases the module's size and engineering costs.

[0013] In addition to their respective shortcomings, the aforementioned methods share a common drawback: they cannot adjust or arbitrarily set the APD gain as needed. The present invention achieves stable, constant APD gain across all temperature conditions through the coordinated operation of a voltage tuning control unit, a boost circuit unit, a signal output unit, and a reference signal unit. Furthermore, the main control chip design enables real-time, autonomous tuning of the APD's target gain. Summary of the Invention

[0014] The purpose of the present invention is to make up for the shortcomings of the existing technology and provide an adaptive gain adjustment APD, including a voltage tuning control unit, a boost circuit unit, a signal output unit, and a reference signal unit, to achieve the function of autonomous tuning and stabilizing the APD gain under full temperature conditions.

[0015] The purpose of the present invention is achieved through the following technical means:

[0016] An adaptive gain adjustment APD, comprising a voltage tuning control unit A, a boost circuit unit, a signal output unit C, and a reference signal unit D; wherein the voltage tuning control unit A comprises: ADC acquisition, main control chip calculation, and DAC output control subunits;

[0017] ADC acquisition is connected to the main control chip,

[0018] The main control chip is connected to the DAC output.

[0019] The DAC output is connected to the signal channel and reference channel of the DC / DC boost circuit.

[0020] The boost circuit unit includes: a DC / DC boost circuit signal channel and a DC / DC boost circuit reference channel;

[0021] The DC / DC boost circuit signal channel is connected to the positive electrode of the signal APD.

[0022] The reference channel of the DC / DC boost circuit is connected to the positive electrode of the reference APD.

[0023] The signal output unit C includes: a signal APD and a signal filtering and amplifying circuit;

[0024] The negative signal of the APD is output after filtering and amplification.

[0025] The reference signal unit D includes a reference light source, a reference APD and a signal filtering and amplifying circuit;

[0026] The reference light source outputs light waves to the reference APD.

[0027] The reference APD negative output signal is filtered and amplified before being collected by the ADC.

[0028] Preferably, the main control chip is a single chip microcomputer, FPGA or DSP.

[0029] Preferably, the signal APD and the reference APD are APDs from the same manufacturer, the same batch, and the same process.

[0030] Preferably, the reference light source is a reference light source with constant power at all temperatures.

[0031] The beneficial effects of the present invention are:

[0032] 1. The present invention uses a voltage tuning control unit, a boost circuit unit, a signal output unit, and a reference signal unit to synchronously tune the reverse bias operating voltage of the signal APD and the reference APD, thereby achieving a stable constant gain of the APD under full temperature conditions. In addition, the main control chip is designed with the function of real-time autonomous tuning of the APD target gain value.

[0033] 2. The present invention uses a light source with constant power under full temperature conditions as a reference light source, which improves the module gain control accuracy; the signal APD and the reference APD are APDs from the same batch under the same process by the same manufacturer. The APD manufacturing process has high batch consistency and has better nonlinear effect than the thermistor solution.

[0034] 3. The present invention overcomes the shortcomings of conventional solutions: the temperature lookup table method requires testing the APD breakdown voltage at different temperatures, which is too labor-intensive and has low economic benefits; the temperature control method requires real-time measurement of the temperature of the APD die, but the APD generally does not have an integrated temperature sensor, making it difficult to obtain the true temperature value; at the same time, the temperature control method uses a relatively large temperature control current under high and low temperature conditions, resulting in large power consumption of the module, increased volume, and high engineering implementation costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural diagram of an adaptive gain adjustment APD. DETAILED DESCRIPTION

[0036] The following is combined with Figure 1 The present invention is further illustrated with examples.

[0037] An adaptive gain adjustment APD, characterized by comprising a voltage tuning control unit A, a boost circuit unit, a signal output unit C, and a reference signal unit D; wherein the voltage tuning control unit A comprises: ADC acquisition, main control chip calculation, and DAC output control subunits;

[0038] ADC acquisition is connected to the main control chip,

[0039] The main control chip is connected to the DAC output.

[0040] The DAC output is connected to the signal channel and reference channel of the DC / DC boost circuit.

[0041] The boost circuit unit includes: a DC / DC boost circuit signal channel and a DC / DC boost circuit reference channel;

[0042] The DC / DC boost circuit signal channel is connected to the positive electrode of the signal APD.

[0043] The reference channel of the DC / DC boost circuit is connected to the positive electrode of the reference APD.

[0044] The signal output unit C includes: a signal APD and a signal filtering and amplifying circuit;

[0045] The negative signal of the APD is output after filtering and amplification.

[0046] The reference signal unit D includes a reference light source, a reference APD and a signal filtering and amplifying circuit;

[0047] The reference light source outputs light waves to the reference APD.

[0048] The reference APD negative output signal is filtered and amplified before being collected by the ADC.

[0049] Specifically, the main control chip is a single chip microcomputer, FPGA or DSP.

[0050] The signal APD and the reference APD are APDs from the same manufacturer, the same batch, and the same process.

[0051] The reference light source is a reference light source with constant power at all temperatures.

[0052] The reference light source has a constant power at all temperatures, and the reference optical path unit obtains the real-time gain value of the APD. In the voltage tuning control unit, the ADC collects the output voltage of the reference APD signal after filtering and amplification to obtain the reference APD channel gain, and the DAC tunes the boost circuit unit to output a high reverse bias voltage. The main control chip synchronizes the input voltage of the DC / DC boost circuit module in real time based on the real-time sampling gain M changes, achieving the function of synchronously tuning the reverse bias operating voltage of the signal APD and the reference APD. At the same time, through closed-loop control, the reference channel gain M is always kept stable or changes according to the preset value, and the signal channel gain M is also stable or changes according to the preset value, achieving the function of autonomously tuning and stabilizing the APD gain under all temperature conditions.

[0053] Obviously, the above embodiments of the present invention are merely examples for the purpose of illustrating the present invention and are not intended to limit the implementation of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to provide an exhaustive list of implementations. However, obvious variations or modifications arising from the essence of the present invention remain within the scope of protection of the present invention.

Claims

1. An adaptive gain adjustment APD, characterized in that: It includes a voltage tuning control unit A, a boost circuit unit, a signal output unit C, and a reference signal unit D; The voltage tuning control unit A includes: ADC acquisition, main control chip calculation and DAC output; The boost circuit unit includes: a DC / DC boost circuit signal channel and a DC / DC boost circuit reference channel; The signal output unit C includes: a signal APD and a signal filtering and amplifying circuit A, and the negative signal of the signal APD is output after passing through the signal filtering and amplifying circuit A; The reference signal unit D includes: a reference light source, a reference APD and a signal filtering and amplifying circuit B. The reference light source outputs light waves to the reference APD, and the negative output signal of the reference APD is collected by the ADC after passing through the filtering and amplifying circuit B. The ADC acquisition and DAC output are connected to the main control chip calculation respectively. The DAC output is connected to the DC / DC boost circuit signal channel and the DC / DC boost circuit reference channel input. The DC / DC boost circuit signal channel output is connected to the positive pole of the signal APD, and the DC / DC boost circuit reference channel output is connected to the positive pole of the reference APD. The signal APD and the reference APD are APDs from the same manufacturer, batch, and process; The reference light source is a reference light source with constant power at all temperatures; A reference light source is obtained by reference APD, and a reference APD signal is obtained by ADC acquisition. After filtering and amplification, the output voltage is controlled by the voltage tuning control unit A to control the boost circuit unit to output a high reverse bias voltage. The main control chip calculates the reference APD gain change through real-time sampling, and synchronously tunes the input voltage of the boost circuit unit in real time to achieve the function of synchronously tuning the reverse bias working voltage of the signal APD and the reference APD. At the same time, through closed-loop control, the gain of the reference APD is always kept stable or changes according to the preset value, and the gain of the signal APD is also kept stable or changes according to the preset value.

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