CN100344084C - Device for conducting position detection using modulation light beam and detection method - Google Patents

Abstract

The invention discloses a device for position detection using modulated light beams. The signal processing circuit is that each pin of a position-sensitive detector is respectively connected in series with an I/V converter, a multiplier, a low-pass filter and an analog/digital converter. Four circuits are connected in parallel with the single-chip microcomputer, wherein one channel of the analog/digital converter is connected with the feedback terminal of the square wave generator, and the output terminal of the square wave generator is connected with the input terminals of each multiplier. The detection method is that the beacon light at the transmitting end is modulated by a square wave with a certain frequency, and the position-sensitive detector at the receiving end receives and outputs it to the I/V converter, and the square wave generated by the square wave generator is input into the multiplier for calculation, and the result After low-pass filtering and analog/digital conversion, four parallel input microcontrollers are used to calculate the position information; one analog/digital output is sent to the square wave generator for feedback control. Due to the square wave modulation and differential processing of the input signal by the multiplier and the filter, the background noise and dark current are eliminated, the error of the output signal is reduced, and the detection accuracy of the system is improved.

Description

Device and method for position detection using modulated light beam

1. Technical field

The invention relates to a device for detecting the position of an object, in particular to a device for detecting the position by using a modulated light beam and a detection method adopted by the device.

2. Background technology

Free space optical communication technology (FSO) is a wireless communication method that realizes point-to-point communication through one-way or two-way transmission of laser beams. It has the speed of optical fiber communication and does not require a large initial investment in scarce resources such as spectrum. , so it has won people's favor, making it an important supplement for optical fiber communication and radio wave wireless communication. Its application fields involve backbone networks, access networks, and local area networks. It is also especially suitable for emergency communications, fast service provisioning, military security communications, and special-occasion communications. Its advantages are scalable bandwidth, fast construction speed, and very economical.

The acquisition, tracking and alignment (ATP: acquisition tracking pointing) device of space light beam is one of the key equipments of free space optical communication. The location of the transmitter is captured and tracked. In the process of free space optical communication, the working precision of ATP device determines the stability and reliability of communication. The device has two main functions: position error signal extraction and servo motor system control. The extraction part of the position error signal is a very critical part of the ATP device, and its accuracy and sensitivity directly affect whether the follow-up tracking is effective. A general ATP device is composed of two parts, a rough tracking subsystem and a fine tracking subsystem. The combination of the two mainly solves the contradiction between field of view and precision. In actual use, in order to simplify the system and reduce costs, a combination of a gun sight and a position-sensitive detector (PSD) is generally used. The gun sight completes the rough alignment in the general direction, and the position-sensitive detector is used to obtain the position of the transmitter. information for fine alignment.

In the current free-space optical communication system, the position-sensitive detector in the ATP device adopts the direct detection method in the position detection application. In order to improve the performance, it is generally used to add a filter to the optical lens part to filter out part of the background light. However, since the dark current of position-sensitive detectors is generally very large, the dark current of a 10×10mm position-sensitive detector at room temperature is 200nA, coupled with the influence of background light, the sensitivity of the system is only about -20dBm. The effective distance of position detection is greatly limited. The usual compensation method is to increase the emission power of the beacon light source laser at the transmitting end, which is limited by the performance and cost of the laser. In addition, in terms of signal processing, there is also a method of modulating the signal at the transmitting end to improve the detection sensitivity. However, this requires the receiving end and the transmitting end to work under a common clock, which is unrealistic in the space optical communication system.

3. Contents of the invention

1. Purpose of the invention: The purpose of the present invention is to provide a device for position detection using modulated light beams, which has higher system position detection accuracy and sensitivity than the prior art, and also provides a detection method for the device.

2. Technical solution: The device for position detection using modulated light beams in the present invention includes an antenna, a transmitting unit, a receiving unit, and a control unit, wherein the transmitting unit includes a beacon light source, beam expander and collimation equipment, and the beacon generated by the beacon light source The light is emitted by the antenna after beam expansion and collimation; the receiving unit includes a position-sensitive detector and a signal processing circuit. The circuit performs processing, and transmits the position deviation information obtained after processing to the control unit; the control unit includes a servo controller and a servo mechanism. The servo controller receives the position deviation information from the signal processing circuit, and then controls the servo mechanism to complete the adjustment of the beam. Alignment, characterized in that: the signal processing circuit includes a multi-stage amplified I/V converter, a phase-adjustable bipolar square wave generator, a two-quadrant analog multiplier, a low-pass filter, an analog/digital converter, and a signal Process single-chip microcomputer or digital signal processing chip; each of the four pins of the position-sensitive detector is connected in series with a multi-stage amplified I/V converter, a two-quadrant analog multiplier, a low-pass filter and An analog/digital converter, the last four routes are connected in parallel to the signal processing single-chip microcomputer or digital signal processing chip, and then the signal processing single-chip microcomputer or digital signal processing chip is connected to the control unit, and the analog/digital converter of one road is also connected with the phase. The feedback end of the modulated bipolar square wave generator is connected, and the output end of the square wave generator is respectively connected to an input end of each multiplier.

The square wave generator can be composed of a square wave generating single-chip microcomputer and a power converter.

In addition, the loop formed by the two-quadrant analog multiplier, low-pass filter, analog/digital converter and phase-adjustable bipolar square wave generator can be replaced by a single-chip microcomputer.

The detection method adopted in the present invention includes firstly emitting beacon light from the transmitting end, after the position-sensitive detector at the receiving end receives the beacon light, it is transmitted to the signal processing circuit for processing, and the processed signal is then input to the servo controller , the servo controller outputs a control signal to control the servo mechanism to complete the alignment of the beam. The beacon light at the transmitting end is modulated by a square wave with a certain frequency, and the signal processing at the receiving end is carried out according to the following steps:

1) After the position-sensitive detector at the receiving end receives the modulated beacon light from the transmitting end, it first converts the optical signal into a current signal, and outputs the current signal from one of its pins to the multi-stage amplified I/V converter , converting the current signal into a voltage value V _i in a suitable range;

2) Use a phase-adjustable bipolar square wave generator to generate a bipolar square wave V _p with an amplitude of +1, -1, and the frequency is consistent with the frequency of the square wave modulation at the transmitting end;

3) Connect V _i and V _p to a two-quadrant analog multiplier for calculation, and input the result of the calculation into a low-pass filter or integrator, so as to filter out the dark current and background noise generated by the position-sensitive detector Component, get the response voltage value Vo completely generated by the beacon light;

4) Each of the four pins of the position-sensitive detector is processed by the method of steps 1)-3), and four response quantities completely generated by the beacon light are obtained, and then input in parallel after digital sampling Signal processing single-chip microcomputer or digital signal processing chip, the position deviation information is calculated by the signal processing single-chip microcomputer or digital signal processing chip and output to the servo controller;

5) Take one of the outputs Vo to the square wave generator for feedback control of the phase of V _p , so that the phase difference between V _i and V _p is zero.

The square wave generator can be realized by a square wave generating single-chip microcomputer. The method is to first send the sampled digital signal to the square wave generating single-chip microcomputer, and the square wave generating single-chip microcomputer generates a phase-controllable square wave, and then converts the power supply to obtain a phase-controllable bipolar square wave.

The invention uses a weak signal processing method to filter out the background noise and dark current in the position sensitive detector, so as to improve the accuracy and sensitivity of system position detection.

During work, the interference received by position-sensitive detectors is mostly natural light or artificial lighting, which is characterized by slow changes in brightness and azimuth, and the response caused by position-sensitive detectors is DC and low-frequency components. If the beacon light is periodically modulated by a square wave, after the position-sensitive detector receives the signal, the detected photocurrent signal waveform of any pin is roughly as shown in Figure 1. It can be seen from Figure 1 that the current when there is no beacon light is caused by the background light and dark current; when there is a beacon light, the current is caused by the background light, dark current and beacon light. When the difference between the response when there is beacon light and the response when there is no beacon light is made, the influence of background noise and dark current that basically does not change with time is eliminated, and the current completely caused by beacon light is obtained.

3. Beneficial effects: the present invention redesigns the signal processing circuit in the ATP system, and multiplies the signal output by the position sensitive sensor with the bipolar square wave output by the square wave generator through a multiplier, so that there is no beacon light When the low-level quantity E ₀ is multiplied by -1, it becomes negative, and the high-level quantity E of the beacon light is multiplied by +1, which remains unchanged. Poor handling. According to the characteristics of the correlation operation of the signal, in the input signal, only the components related to the bipolar square wave can have output, that is, only the bipolar square wave component with a mean value of zero in the input signal can pass through, and other components will pass through. It cannot pass, especially the DC component is also greatly attenuated. In this way, the influence of background noise and dark current on the input beacon light is basically eliminated, and the calculated position information is more accurate, thereby improving the position detection accuracy and sensitivity of the system.

4. Description of drawings

Fig. 1 is a signal waveform of a pin PSD receiving modulated beacon light.

Figure 2 is a block diagram of an ATP system with an independent beacon light.

Figure 3 is a block diagram of the signal processing circuit.

Figure 4 is a block diagram of a signal processing circuit that uses a general-purpose single-chip microcomputer to replace the circuit.

Figure 5 is a schematic diagram of the correlation operation waveform between the beacon photoelectric signal and the bipolar square wave at different phase differences ψ

Figure, a: when ψ=π, b: when ψ=π/6, c: when ψ=0, d: the relationship between the output after correlation and the misalignment angle.

5. Specific implementation

As shown in Figure 2, it is a block diagram of an ATP system with an independent beacon light. The system includes a shared antenna, a transmitting unit, a receiving unit, and a control unit, wherein the transmitting unit includes a beacon light source, a signal light source, a beam expander collimator and a combination The wave plate, the beacon light generated by the beacon light source and the signal light generated by the signal light source are respectively beam expanded and collimated, and the two optical signals are combined into one by the wave combining plate, and then transmitted by the common antenna; the receiving unit includes The wave plate, the signal light processing device, the position sensitive detector and the signal processing circuit, share the light beam emitted by the space object received by the antenna and transmit it to the sub-wave plate, and the signal light and the beacon light are separated by the sub-wave plate, wherein the signal light Transmitted to the signal light detection device, the beacon light is transmitted to the position-sensitive detector and converted into an electrical signal, then input to the signal processing circuit for processing, and then the processed electrical signal is transmitted to the control unit; the control unit mainly includes a servo controller And the servo mechanism, the servo controller receives the signal from the signal processing circuit, and controls the servo mechanism to complete the alignment of the spatial light beam. The signal processing circuit is shown in Figure 3, which includes a multi-stage amplified I/V converter, phase adjustable Modulated bipolar square wave generator, two-quadrant analog multiplier, low-pass filter, and signal processing microcontroller or digital signal processing chip. Each of the four pins of the position-sensitive detector is sequentially connected in series with a multi-stage amplified I/V converter, a two-quadrant analog multiplier, a low-pass filter and an analog/digital converter, and finally The signal processing single-chip microcomputer or digital signal processing chip is connected in parallel in four ways, and the signal processing single-chip microcomputer or digital signal processing chip is connected to the control unit. Simultaneously, the analog-to-digital converter of one path is connected to the feedback end of the phase-adjustable bipolar square wave generator, and the output end of the square wave generator is respectively connected to an input end of each multiplier.

As an improvement of the present invention, the loop formed by the two-quadrant analog multiplier, low-pass filter, analog/digital converter and phase-adjustable bipolar square wave generator can be replaced by a single-chip microcomputer, and the single-chip microcomputer can Realize the function of this circuit. Refer to Figure 4 for the signal processing circuit using a single-chip microcomputer to replace the loop.

The working method of the present invention is to firstly carry out square wave modulation of a certain frequency on the beacon light at the transmitting end, and then emit the modulated beacon light through the transmitting device, and after the position-sensitive detector at the receiving end receives the beacon light, firstly It is converted into a current signal and output from four pins, and the output of each pin is sent to a multi-stage amplified I/V conversion unit to convert the current signal into a voltage value V _i of a suitable range, which is determined by It consists of three parts:

V _i ＝V _i0 +S _i (t)+n _i (t)

Among them, S _i (t) is a bipolar square wave with the same frequency and phase modulated by the beacon light square wave, and its function expression is:

${\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{<span\; class="notranslate">\; \&infin;</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}\frac{\mathrm{<span\; class="notranslate">\; n\&pi;</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; t</span>}$

V _i0 and n _i (t) are DC component and low frequency AC noise respectively;

At the same time, use a square wave generator to generate a bipolar square wave V _p with an amplitude of +1, -1, and the frequency is consistent with the frequency of the square wave modulation at the transmitting end. The function expression is:

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{<span\; class="notranslate">\; \&infin;</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}\frac{\mathrm{<span\; class="notranslate">\; n\&pi;</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; )</span>$

Then, V _i and V _p are connected to a two-quadrant analog multiplier for calculation, and the multiplied result is then input into a low-pass filter or an integrator to extract DC and low-frequency components to obtain Vo. The combination of the two forms a correlator. According to the characteristics of the correlation operation of the signal, in the V _i signal, only the component related to V _p can have an output, that is, the bipolar square wave component with a mean value of zero in V _i , other components will not pass through, especially The DC component is also greatly attenuated; and the output value Vo of the filter has a cosine relationship with the phase difference Ψ of V _i and V _p . The function expression of Vo is:

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&CircleTimes;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; \&Right\; Arrow;</span><span\; class="notranslate">\; \&infin;</span>}{\mathrm{<span\; class="notranslate">\; lim</span>}}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; NT</span>}}{<span\; class="notranslate">\; \&Integral;</span>}_{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; NT</span>}}^{\mathrm{<span\; class="notranslate">\; NT</span>}}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; dt</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&psi;</span>}$

Therefore, the phase of _Vp can be controlled by output Vo feedback, and when the phase difference is zero, the output reaches the maximum value. The maximum value V _omax has a corresponding relationship with the average difference EE ₀ between when there is a beacon light and when there is no beacon light in the input signal. See Figure 4.

The four pins of the position-sensitive detector are processed in the same way to obtain four response quantities completely generated by the beacon light. After digital sampling, the signal processing microcontroller is input in parallel, and the signal processing microcontroller performs position information calculation and outputs it to the servo. The controller finally realizes the alignment of the beam through the servo mechanism.

In the actual signal processing circuit, the feedback loop should not only search for the maximum value of the output, but also ensure that the output is the maximum value. There is a certain contradiction between the two, and the output is often not stable. In order to improve performance and solve this contradiction, a part of the input signal V _i is divided according to a strict ratio for a large-scale search of the phase, and then the searched phase with the maximum value is sent to the local bipolar of the channel with stable output square wave generator, forming a double ring structure. In this way, one path is responsible for large-scale tracking of the phase, and the other path provides a stable output of the maximum value.

The working mode of the square wave generating microcontroller in the square wave generator is as follows:

First store the waveform file in the memory, the positive half cycle is all 1, and the negative half cycle is all 0. The square wave generation MCU sequentially reads the waveform files in the memory and outputs a square wave from the port. If you want to shift the phase, you can jump a certain step in the waveform file according to the amount you want to shift, and finally get the waveform of the required phase.

Claims (6)

1. A device for position detection using a modulated light beam, including an antenna, a transmitting unit, a receiving unit, and a control unit, wherein the transmitting unit includes a beacon light source, beam expansion and collimation equipment, and the beacon light generated by the beacon light source is expanded. After the beam is collimated, it is emitted by the antenna; the receiving unit includes a position-sensitive detector and a signal processing circuit. After the antenna receives the beacon light, it is sent to the position-sensitive detector to convert the optical signal into a current signal, and then input to the signal processing circuit for processing. , and transmit the position deviation information obtained after processing to the control unit; the control unit includes a servo controller and a servo mechanism, the servo controller receives the position deviation information from the signal processing circuit, and then controls the servo mechanism to complete the alignment of the beam, It is characterized in that the signal processing circuit includes a multi-stage amplified I/V converter, a phase-adjustable bipolar square wave generator, a two-quadrant analog multiplier, a low-pass filter, an analog/digital converter, and a signal processing microcontroller or Digital signal processing chip; each of the four pins of the position-sensitive detector is connected in series with a multi-stage amplified I/V converter, a two-quadrant analog multiplier, a low-pass filter and an analog/ digital converter, and the last four channels are connected in parallel to the signal processing single-chip microcomputer or digital signal processing chip, and then the signal processing single-chip microcomputer or digital signal processing chip is connected to the control unit, and the analog/digital converter of one channel is also connected with the phase-adjustable bipolar The feedback terminal of the linear square wave generator is connected, and the output terminal of the square wave generator is respectively connected with an input terminal of each multiplier. 2. The device for position detection using modulated beams according to claim 1, characterized in that: a two-quadrant analog multiplier, a low-pass filter, an analog/digital converter and a phase-adjustable bipolar square wave generator The loop is replaced by a single chip microcomputer. 3. The device for position detection using modulated light beams according to claim 1, characterized in that: the square wave generator in the signal processing circuit is composed of a square wave generating single-chip microcomputer and a power converter. 4. A detection method of a device for position detection using a modulated light beam as claimed in claim 1, comprising firstly emitting a beacon light from the transmitting end, and after the position-sensitive detector at the receiving end receives the beacon light, transmits it to the signal processing The circuit is processed, and the processed signal is input to the servo controller, and the control signal is output by the servo controller to control the servo mechanism to complete the alignment of the beam. The characteristic is that the beacon light at the transmitting end is modulated by a square wave with a certain frequency The signal processing at the receiving end is carried out in the following steps: 1) After the position-sensitive detector at the receiving end receives the modulated beacon light from the transmitting end, it first converts the optical signal into a current signal, and outputs the current signal from one of its pins to a multi-stage amplified I/O V converter, converting the current signal into a voltage value V _i in a suitable range; 2) At the same time, use a phase-adjustable bipolar square wave generator to generate a bipolar square wave V _p with an amplitude of +1, -1, and the frequency is consistent with the frequency modulated by the square wave at the transmitting end; 3) Connect V _i and V _p to a two-quadrant analog multiplier for calculation, and input the result of the calculation into a low-pass filter or integrator, so as to filter out the dark current and background noise generated by the position-sensitive detector Component, get the response voltage value Vo completely generated by the beacon light; 4) Process each of the four pins of the position-sensitive detector according to steps 1)-3) to obtain four responses completely generated by the beacon light, and perform digital sampling on them in parallel Input signal processing single-chip microcomputer or digital signal processing chip, the position deviation information is calculated by the signal processing single-chip microcomputer or digital signal processing chip and output to the servo controller; 5) Take one of the outputs Vo to the square wave generator for feedback control of the phase of V _p , so that the phase difference between V _i and V _p is zero. 5. The working method of the device for position detection using modulated light beams according to claim 4, characterized in that: the square wave generator is implemented by a square wave generating single-chip microcomputer, and the digital signal obtained by sampling is first sent to the square wave generating single chip microcomputer , the square wave is generated by the single-chip microcomputer to generate a phase-controllable square wave, and then a phase-controllable bipolar square wave is obtained by power conversion. 6. The working method of the device for position detection using modulated light beams according to claim 5, characterized in that the working method of the square wave generating single-chip microcomputer is: first store the waveform file in the memory, and the positive half cycle is all 1 , the negative half cycle is all 0, the square wave is generated. When the microcontroller is working, it sequentially reads the waveform files in the memory, and outputs the square wave from the port.

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