Phase-locked loop circuits, optoelectronic systems and electronic equipment

Abstract

A phase-locked loop (PLL) circuit, an optoelectronic system, and an electronic device are disclosed. The PLL circuit includes: a signal processing circuit for converting the output signal of the laser into a difference frequency signal; a dual frequency and phase detector circuit configured to output a first error correction signal and a second error correction signal with opposite polarity to the first error correction signal based on the difference frequency signal output by the signal processing circuit; and a modulation circuit configured to perform calculations on the pre-correction signal and either the first or second error correction signal to obtain a modulation signal, the modulation signal being used to control the driving of the laser to modulate the laser output. By using two frequency and phase detectors to output the first and second error correction signals with only opposite polarities, the polarity reversal circuit in the prior art is eliminated, reducing the overall circuit delay and improving circuit performance.

Description

Technical Field

[0001] This application belongs to the field of modulation signal technology, and particularly relates to phase-locked loop circuits, optoelectronic systems and electronic equipment. Background Technology

[0002] In frequency-modulated continuous wave (FMCW) laser absolute measurement technology, ranging accuracy is significantly affected by the linearity of frequency modulation and is also subject to the inherent nonlinearity of the light source. Furthermore, this nonlinearity becomes increasingly severe as the frequency modulation speed increases. Therefore, it is essential to precisely control the instantaneous frequency of the laser at high-speed frequency modulation to ensure good linearity in its modulation characteristics. For this purpose, phase-locked loops (PLLs) are commonly used for precise laser control.

[0003] Most existing phase-locked loop circuits use a frequency and phase detector. The signal output from the frequency and phase detector is split into two outputs by a direction selection switch. The polarity of one of the outputs is changed by a subsequent polarity reversal circuit so that the two outputs are used for rising-side control and falling-side control of the signal, respectively. However, the added circuitry includes the need to add a time delay circuit, resulting in a large overall circuit delay. Summary of the Invention

[0004] The purpose of this application is to provide phase-locked loop circuits, optoelectronic systems, and electronic devices, aiming to solve the problem of large time delays in traditional phase-locked loop circuits.

[0005] A first aspect of this application provides a phase-locked loop circuit for a laser, comprising: a signal processing circuit for converting the output signal of the laser into a difference frequency signal; a dual frequency and phase detector circuit, including a first frequency and phase detector and a second frequency and phase detector, wherein the first frequency and phase detector is used to output a first error correction signal based on the difference frequency signal, and the second frequency and phase detector is used to output a second error correction signal with the opposite polarity to the first error correction signal based on the difference frequency signal; and a modulation circuit configured to perform calculations on a pre-correction signal and either the first error correction signal or the second error correction signal to obtain a modulation signal, wherein the modulation signal is used to control the driving of the laser to modulate the output of the laser.

[0006] Compared with the prior art, the beneficial effects of this embodiment are as follows: by using two frequency and phase detectors to output a first error correction signal and a second error correction signal with only opposite polarities, the output signal is modulated, eliminating the polarity reversal circuit in the prior art, reducing the overall circuit delay, and improving the circuit performance.

[0007] In one embodiment, the first frequency-phase detector is used to output a first error correction signal based on the phase difference between the difference frequency signal and the reference signal, and the second frequency-phase detector is used to output a second error correction signal based on the phase difference between the difference frequency signal and the reference signal.

[0008] In one embodiment, the operation is to perform an integral operation on the first error correction signal or the second error correction signal and then add it to the pre-correction signal.

[0009] In one embodiment, the output signal is an optical signal, and the signal processing circuit includes: an optical interferometer, the input of which is connected to the output of the laser, for converting the output signal into a beat frequency optical signal; a balanced detector, the input of which is connected to the output of the optical interferometer, for converting the beat frequency optical signal into a difference frequency electrical signal; and a comparator, the input of which is connected to the input of the balanced detector, and the output of which is connected to the input of the dual frequency and phase detector circuit, for waveform shaping of the difference frequency electrical signal into the difference frequency signal.

[0010] In one embodiment, the input terminals of both the first and second frequency-phase detectors are connected to the output terminal of the signal processing circuit. The output terminals of the first and second frequency-phase detectors are connected to the input terminal of the control circuit through a first loop filter and a second loop filter, respectively. The first frequency-phase detector outputs a first frequency-discriminating current signal based on the phase difference between the difference frequency signal and the reference signal. The second frequency-phase detector outputs a second frequency-discriminating current signal based on the phase difference between the difference frequency signal and the reference signal. The first loop filter converts the first frequency-discriminating current signal into a voltage signal and outputs the first error correction signal after smoothing and filtering. The second loop filter converts the second frequency-discriminating current signal into a voltage signal and outputs the second error correction signal after smoothing and filtering.

[0011] In one embodiment, the dual frequency and phase detector circuit further includes a control unit, which is connected to the first frequency and phase detector and the second frequency and phase detector respectively, for setting the polarity of the first frequency current signal and the second frequency current signal output by the first frequency and phase detector and the second frequency and phase detector.

[0012] In one embodiment, the control circuit includes: a direction selection switch, the two input terminals of which are respectively connected to the output terminals of the first loop filter and the second loop filter, and the direction selection switch is configured to select either the first error correction signal or the second error correction signal to be transmitted to the output terminal of the direction selection switch according to a trigger signal; an integrator circuit, the input terminal of which is connected to the output terminal of the direction selection switch, and the integrator circuit is configured to integrate the first error correction signal or the second error correction signal to generate an error signal with positive and negative slopes; and an adder circuit, the input terminal of which is connected to the output terminal of the integrator circuit, and the output terminal of which is connected to the input terminal of the laser, and the adder circuit is configured to output the modulation signal to the laser according to the pre-correction signal and the error signal.

[0013] In one embodiment, the pre-correction signal is a triangular wave, the trigger signal is a square wave, and the trigger signal undergoes a level jump between the peak and trough of the pre-correction signal to control the direction selection switch.

[0014] A second aspect of this application provides an optoelectronic system for generating linear phase chirp using a laser source, comprising a laser and the aforementioned phase-locked loop circuit applied to the laser. The laser includes: a controllable power supply for outputting a drive current according to the modulation signal; and a laser source for outputting a swept-frequency optical signal according to the drive current. The swept-frequency optical signal is output through a coupler and is the output of the laser.

[0015] A third aspect of this application provides an electronic device including the aforementioned optoelectronic system that generates linear phase chirp using a laser light source. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of an embodiment of this application;

[0017] Figure 2 This is a circuit diagram of an embodiment of this application;

[0018] Figure 3 This is a waveform diagram of the pre-calibration signal and the trigger signal according to an embodiment of this application.

[0019] In the above figures: 100, signal processing circuit; 101, optical interferometer; 102, balanced detector; 103, comparator; 200, dual frequency and phase detector circuit; 201, first frequency and phase detector; 202, second frequency and phase detector; 203, first loop filter; 204, second loop filter; 205, control unit; 300, control circuit; 301, direction selection switch; 302, integrator circuit; 303, adder circuit; 400, laser; 401, controllable power supply; 402, laser source; 403, coupler. Detailed Implementation

[0020] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0021] When a component is said to be "connected to" another component, it can be directly connected to the other component or indirectly connected to that other component.

[0022] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0023] like Figure 1 As shown, in one embodiment, a phase-locked loop circuit for a laser 400 is provided, comprising: a signal processing circuit 100 for converting the output signal of the laser 400 into a difference frequency signal; a dual frequency and phase detector circuit 200 configured to output a first error correction signal and a second error correction signal with opposite polarity to the reference voltage based on the difference frequency signal output by the signal processing circuit 100; and a modulation circuit 300 configured to perform calculations based on the pre-correction signal and the first error correction signal or the second error correction signal to obtain a modulation signal, and to control the driving of the laser 400 according to the modulation signal to modulate the output of the laser 400, thereby realizing closed-loop control of the laser 400.

[0024] In this circuit, the two frequency and phase detectors of the dual frequency and phase detector circuit 200 output a first error correction signal and a second error correction signal, respectively. The polarities of the first error correction signal and the second error correction signal are opposite to those of the reference voltage, while the other parameters are the same. The first error correction signal is used to obtain a modulation signal by performing a calculation with the rising edge of the pre-correction signal through the control circuit 300. The second error correction signal is used to obtain a modulation signal by performing a calculation with the falling edge of the pre-correction signal through the control circuit 300. This eliminates the need for the polarity reversal circuit required when using a single frequency and phase detector in the prior art. During correction, either the first error correction signal or the second error correction signal can be arbitrarily selected to correct the output signal through the control circuit 300.

[0025] like Figure 2 As shown, in one embodiment, the dual frequency and phase detector circuit 200 includes a first frequency and phase detector 201 and a second frequency and phase detector 202. The input terminals of both the first and second frequency and phase detectors 201 and 202 are connected to the output terminal of the signal processing circuit 100. The output terminals of the first and second frequency and phase detectors 201 and 202 are connected to the input terminal of the control circuit 300 through a first loop filter 203 and a second loop filter 204, respectively. The first and second frequency and phase detectors 201 and 202 are used to compare the frequency and phase of the difference frequency signal with the reference signal to obtain the phase difference between the difference frequency signal and the reference signal. The first and second frequency and phase detectors 201 and 202 output a first frequency-discriminating current signal and a second frequency-discriminating current signal, respectively, based on the phase difference. The first and second frequency-discriminating current signals are converted into a first error correction signal and a second error correction signal through the first loop filter 203 and the second loop filter 204, respectively. Specifically, the first loop filter 203 converts the first frequency-discriminating current signal into a voltage signal and smooths and filters it, while the second loop filter 204 converts the second frequency-discriminating current signal into a voltage signal and smooths and filters it. Both the first error correction signal and the second error correction signal are voltage signals. By using two frequency and phase detectors to generate the first error correction signal and the second error correction signal (which has the opposite polarity to the reference voltage) respectively, the polarity reversal circuit is omitted, reducing the overall circuit delay compared to existing technologies.

[0026] like Figure 2As shown, in one embodiment, the dual frequency and phase detector circuit 200 further includes a control unit 205. The control unit 205 may be a microcontroller unit (MCU), a field-programmable gate array (FPGA), or a digital signal processor (DSP). The control unit 205 is connected to the first frequency and phase detector 201 and the second frequency and phase detector 202 respectively, for setting the polarity of the first error correction signal and the second error correction signal.

[0027] In the prior art, the polarity of the signal is changed by using a polarity reversal circuit. If the polarity reversal circuit has a problem, the circuit cannot be adjusted quickly and directly. However, by controlling the first frequency and phase detector 201 and the second frequency and phase detector 202 through the control unit 205, the subsequent debugging and modification costs can be effectively reduced.

[0028] like Figure 2 As shown, in one embodiment, the output signal can be an optical signal, such as a swept-frequency optical signal. The signal processing circuit 100 includes an optical interferometer 101, a comparator 103, and a balanced detector 102.

[0029] The input terminal of the optical interferometer 101 is connected to the output terminal of the laser 400 to convert the output signal into a beat frequency optical signal; the input terminal of the balanced detector 102 is connected to the output terminal of the optical interferometer 101 to convert the beat frequency optical signal into a difference frequency electrical signal.

[0030] Comparator 103 can be a high-speed comparator. The input terminal of comparator 103 is connected to the input terminal of the balanced detector 102, and the output terminal of comparator 103 is connected to the input terminal of the dual frequency and phase detector circuit 200. It is used to shape the waveform of the difference frequency electrical signal into a difference frequency signal and output the difference frequency signal to the dual frequency and phase detector circuit 200. Specifically, comparator 103 converts the difference frequency electrical signal into a difference frequency signal, that is, it converts the sine wave signal into a square wave signal with uniform amplitude, so that the frequency and phase detector can obtain the phase difference between the difference frequency signal and the reference signal.

[0031] Among them, the optical interferometer 101 can be a Mach-Zehnder interferometer (MZI interferometer), which can generate a phase difference by splitting the output signal into two beams and passing the two beams through optical fibers of different lengths, and then mixing the two beams to obtain a low-frequency and stable beat frequency optical signal.

[0032] The reference signal is generated by a crystal oscillator and is a standard difference frequency signal generated based on the pre-calibration signal. It is used to determine the frequency and phase of the difference frequency signal output by the balanced detector 102 to ensure the stability of the output signal. At the same time, modifying the reference signal will still cause the difference frequency signal to relock to the reference signal frequency, thereby modulating the output signal.

[0033] like Figure 2 As shown, in one embodiment, the control circuit 300 includes: a direction selection switch 301, an integrator circuit 302, and an adder circuit 303. The direction selection switch 301 can be an analog switch.

[0034] The two input terminals of the direction selection switch 301 are connected to the output terminals of the first loop filter 203 and the second loop filter 204, respectively. The direction selection switch 301 is configured to transmit a first error correction signal or a second error correction signal to the output terminal of the direction selection switch 301 according to a trigger signal. The trigger signal is generated according to the pre-correction signal. The input terminal of the integrator circuit 302 is connected to the output terminal of the direction selection switch 301. The integrator circuit 302 is configured to integrate the first error correction signal or the second error correction signal to generate an error signal with positive and negative slopes. The input terminal of the adder circuit 303 is connected to the output terminal of the integrator circuit 302. The output terminal of the adder circuit 303 is connected to the input terminal of the laser 400. The adder circuit 303 is configured to output a modulation signal to the laser 400 according to the pre-correction signal and the error signal.

[0035] like Figure 3 As shown, in one embodiment, the pre-correction signal is a triangular wave, and the trigger signal is a square wave signal corresponding to the pre-correction signal. The trigger signal undergoes a level transition at the peak and trough of the pre-correction signal. The amplitude of the pre-correction signal corresponds to the modulation bandwidth of the output signal.

[0036] It should be noted that the transition edge of the trigger signal can periodically control the direction selection switch 301. For example, when the pre-correction signal is at a trough, the falling edge of the trigger signal controls the direction selection switch 301 to connect the integrator circuit 302 to the first loop filter 203, so as to transmit the first error correction signal to the integrator circuit 302. This allows the first error correction signal to generate a modulation signal by combining the rising edge of the pre-correction signal with the control circuit 300. Correspondingly, when the pre-correction signal is at a peak, the rising edge of the trigger signal controls the direction selection switch 301 to connect the integrator circuit 302 to the second loop filter 204, so as to transmit the second error correction signal to the integrator circuit 302. This allows the second error correction signal to generate a modulation signal by combining the falling edge of the pre-correction signal with the control circuit 300. This eliminates the need for the polarity reversal circuit in the prior art and improves the overall circuit performance.

[0037] The second aspect of this application provides a photoelectric system for generating linear phase chirp using a laser source, including the phase-locked loop circuit applied to the laser 400 described above. The laser 400 includes: a controllable power supply 401, which outputs a drive current according to a modulation signal; and a laser source 402, which outputs a swept-frequency optical signal according to the drive current. The swept-frequency optical signal is output through a coupler 403 and is the output of the laser 400.

[0038] A third aspect of this application provides an electronic device including the aforementioned optoelectronic system that generates linear phase chirp using a laser light source.

[0039] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A phase-locked loop circuit for use in lasers, characterized in that, include: A signal processing circuit is used to convert the output signal of the laser into a difference frequency signal; A dual frequency and phase detector circuit includes a first frequency and phase detector and a second frequency and phase detector. The first frequency and phase detector is used to output a first error correction signal based on the difference frequency signal, and the second frequency and phase detector is used to output a second error correction signal with the opposite polarity to the first error correction signal based on the difference frequency signal. The control circuit is configured to perform calculations on the pre-correction signal and the first error correction signal or the second error correction signal to obtain a modulation signal, the modulation signal being used to control the drive of the laser to modulate the output of the laser.

2. The phase-locked loop circuit applied to a laser as described in claim 1, characterized in that, The first frequency and phase detector is used to output a first error correction signal based on the phase difference between the difference frequency signal and the reference signal, and the second frequency and phase detector is used to output a second error correction signal based on the phase difference between the difference frequency signal and the reference signal.

3. The phase-locked loop circuit applied to a laser as described in claim 1 or 2, characterized in that, The operation involves integrating the first error correction signal or the second error correction signal and then adding it to the pre-correction signal.

4. The phase-locked loop circuit applied to a laser as described in claim 1 or 2, characterized in that, The output signal is an optical signal, and the signal processing circuit includes: An optical interferometer, wherein the input end of the optical interferometer is connected to the output end of the laser to convert the output signal into a beat frequency optical signal; A balanced detector, the input of which is connected to the output of the optical interferometer, is used to convert the beat frequency optical signal into a difference frequency electrical signal. A comparator, the input of which is connected to the input of the balanced detector, and the output of which is connected to the input of the dual frequency and phase detector circuit, are used to shape the waveform of the difference frequency electrical signal into the difference frequency signal.

5. The phase-locked loop circuit applied to a laser as described in claim 2, characterized in that, The input terminals of the first and second frequency and phase detectors are both connected to the output terminal of the signal processing circuit, and the output terminals of the first and second frequency and phase detectors are connected to the input terminal of the control circuit through the first loop filter and the second loop filter, respectively. The first frequency and phase detector is used to output a first frequency-discriminating current signal based on the phase difference between the difference frequency signal and the reference signal. The second frequency and phase detector is used to output a second frequency-discriminating current signal based on the phase difference between the difference frequency signal and the reference signal. The first loop filter converts the first frequency-discriminating current signal into a voltage signal and outputs the first error correction signal after smoothing and filtering. The second loop filter converts the second frequency-discriminating current signal into a voltage signal and outputs the second error correction signal after smoothing and filtering.

6. The phase-locked loop circuit applied to a laser as described in claim 5, characterized in that, The dual frequency and phase detector circuit also includes a control unit, which is connected to the first frequency and phase detector and the second frequency and phase detector respectively, for setting the polarity of the first frequency current signal and the second frequency current signal output by the first frequency and phase detector and the second frequency and phase detector.

7. The phase-locked loop circuit applied to a laser as described in claim 5 or 6, characterized in that, The control circuit includes: A direction selection switch, wherein the two input terminals of the direction selection switch are respectively connected to the output terminals of the first loop filter and the second loop filter, and the direction selection switch is configured to select the first error correction signal or the second error correction signal to be transmitted to the output terminal of the direction selection switch according to the trigger signal; An integrator circuit, the input of which is connected to the output of the direction selection switch, is configured to integrate the first error correction signal or the second error correction signal to generate an error signal with positive and negative slopes. An adder circuit, wherein the input of the adder circuit is connected to the output of an integrator circuit, and the output of the adder circuit is connected to the input of the laser, and the adder circuit is configured to output the modulation signal to the laser based on the pre-correction signal and the error signal.

8. The phase-locked loop circuit applied to a laser as described in claim 7, characterized in that, The pre-calibration signal is a triangular wave, and the trigger signal is a square wave signal. The trigger signal undergoes a level jump between the peak and trough of the pre-calibration signal to control the direction selection switch.

9. A photoelectric system for generating linear phase chirp using a laser light source, characterized in that, Includes a laser and a phase-locked loop circuit for the laser as described in any one of claims 1 to 8, wherein the laser comprises: A controllable power supply, wherein the controllable power supply is used to output a drive current according to the modulation signal; A laser source is provided, which is used to output a swept-frequency optical signal according to the driving current. The swept-frequency optical signal is output through a coupler and is the output of the laser.

10. An electronic device, characterized in that, This includes an optoelectronic system that generates linear phase chirp using a laser source as described in claim 9.

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