A photogenerated microwave source system and method

Abstract

The application discloses a kind of light microwave source system and method, the system includes light signal generation module, for generating CPT phenomenon, output optical filtered laser beam;Photodetector, for converting optical signal into electrical signal;Electric signal adjustment module, for amplifying the electrical signal output by photodetector, and carry out beam splitting;Crystal oscillator locking module, including crystal oscillator, for the second road signal after beam splitting is modulated and input to frequency divider, with the signal output by crystal oscillator after frequency division is phase detected and forms error check signal, crystal oscillator locking module generates the microwave signal of the microwave source system;PID control module, for processing error check signal, forms voltage control signal to control voltage control phase shifter.The application has the stability of CPT atomic clock and the advantage of low phase noise of photoelectric oscillator, improves the stability of microwave signal, can provide high-stability and low-phase-noise microwave and time frequency signal.

Description

Technical Field

[0001] This invention relates to the field of photogenerated microwave technology. More specifically, it relates to a photogenerated microwave source system and method. Background Technology

[0002] Low-phase-noise, high-stability microwave frequency sources are widely used in radar, communication metrology, and other fields, and are core components of modern electronic devices. There are generally three ways to obtain a microwave source: 1. Frequency doubling using a standard crystal oscillator; 2. Utilizing the low loss of the dielectric material, designing a high-Q dielectric resonant cavity, constructing a positive feedback amplifier circuit, and controlling the phase and amplitude to improve the stability of the output signal; 3. Using optically generated microwaves, mainly in two categories: 1. Locking an ultra-stable laser onto a high-stable optical resonant cavity and converting it to the desired frequency using an optical comb; 2. The photoelectric oscillator method; using optical fibers or optical filters to filter the light, converting the optical signal into an electrical signal, amplifying the electrical signal, and then loading it onto the modulator of the laser to form an oscillation loop.

[0003] In the process of realizing this invention, the inventors discovered at least the following problems in the prior art: Of the methods described above, the first method is currently the most mature, but its phase noise and stability indicators are poor. The second method has extremely high stability and phase noise indicators, but the equipment is large and heavy, limiting its application. The third method, locking an ultra-stable laser onto an optical resonant cavity, can achieve extremely high stability and phase noise indicators, but due to laser wavelength drift and aging, its continuous operating time is short, and its optical path structure is complex and costly. The optoelectronic oscillator method can achieve better phase noise indicators, and it has a compact structure, long continuous operating time, and a wide range of applications. The main components of an optoelectronic oscillator are a laser, an optical filter cavity (generally composed of fiber or micro / nano structure optical filter cavities), a photodetector, an electrical amplifier, and an optical modulator. Based on the main working principle, different devices can be selected to construct various optoelectronic oscillators for generating high-quality microwave signals. Optically generated microwave technology can obtain microwave signal phase noise indicators, and CPT-type atomic clocks can obtain high-stability microwave signals. However, many more applications require microwave signal sources with both superior phase noise and stability.

[0004] Therefore, there is a need to provide a photogenerated microwave source system and method. Summary of the Invention

[0005] The purpose of this invention is to provide a photogenerated microwave source system and method to solve at least one of the problems existing in the prior art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The first aspect of this invention provides a photoelectric microwave source system, which includes a light signal generation module, a photodetector, an electrical signal adjustment module, a crystal oscillator locking module, and a PID control module, wherein...

[0008] The optical signal generation module is used to generate the CPT phenomenon and form an optical filter;

[0009] The photodetector is used to convert optical signals into electrical signals;

[0010] The electrical signal adjustment module is used to amplify the electrical signal output by the photodetector and split it through the first coupler;

[0011] The crystal oscillator locking module includes a crystal oscillator for modulating the second signal after beam splitting, dividing the modulated signal by a frequency divider, comparing the divided signal with the signal output by the crystal oscillator to form an error verification signal, and generating the microwave signal of the microwave source system.

[0012] The PID control module is used to process the error verification signal output by the crystal oscillator locking module to form a voltage control signal to control the voltage-controlled phase shifter.

[0013] Optionally, the optical signal generation module includes a VCSEL laser and a rubidium bulb unit, wherein the rubidium bulb unit generates the CPT phenomenon under the excitation of an external optical field and an electric field.

[0014] Optionally, the system further includes a beam shaping module located between the VCSEL laser and the rubidium bulb unit, the beam shaping module being used to adjust the light generated by the VCSEL laser to form circularly polarized light.

[0015] Optionally, the electrical signal adjustment module includes a first electrical amplification module and a first coupler. The first coupler splits the electrical signal that has passed through the first electrical amplification module. The first electrical signal after splitting passes through a voltage-controlled phase shifter and is then input to the VCSEL laser to form a closed loop.

[0016] Optionally, the crystal oscillator locking module includes a second electrical amplifier module, a second coupler, a frequency divider, a crystal oscillator, and a phase detector module. The second electrical signal after being split by the first coupler is amplified by the second electrical amplifier module and then enters the second coupler. The second coupler splits the electrical signal, and the first signal of the second coupler enters the frequency divider. The second signal of the second coupler is output as a 6.8 GHz microwave signal.

[0017] Optionally, the second signal output by the crystal oscillator is used as the standard time signal of the microwave source system.

[0018] Optionally, the frequency divider is used to divide the first electrical signal output by the second coupler.

[0019] Optionally, the phase detection module is used to perform phase calculation on the frequency-divided signal and the electrical signal output by the crystal oscillator, and output the phase detection result to the PID control module.

[0020] Optionally, the PID control module includes a PID controller and a voltage-controlled phase shifter. The PID controller processes the phase detection result to generate a voltage control signal to control the voltage-controlled phase shifter.

[0021] A second aspect of the present invention provides a method for photogenerated microwaves, the method comprising:

[0022] The light source generated by the VCSEL laser is passed through a rubidium metal gas cell to produce the CTP phenomenon, forming an optical filter, and then the laser beam is output after optical filtering;

[0023] The filtered optical signal is converted into an electrical signal by a photodetector.

[0024] The electrical signal is amplified and modulated. The modulated electrical signal is split by the first coupler. The first signal after splitting is connected to the VCSEL laser through the voltage-controlled phase shifter to form a closed loop.

[0025] The second signal after beam splitting is amplified and modulated, and the modulated signal is input to the frequency divider for frequency division. The frequency-divided signal is phase-detected with the first signal output by the crystal oscillator and an error verification signal is formed. The crystal oscillator locking module generates the microwave signal of the microwave source system, and the second signal output by the crystal oscillator is used as the standard time signal of the microwave source system.

[0026] The PID control module processes the error verification signal generated after phase detection to form a voltage control signal to control the voltage-controlled phase shifter.

[0027] The beneficial effects of this invention are as follows:

[0028] This invention provides a system and method for generating a photoelectric microwave source. The method utilizes a VCSEL laser, employing the CPT phenomenon generated by a rubidium metal gas cell to form an optical filter. This filter is then converted into an electrical signal by a detector, amplified, and modulated to form a positive feedback loop. The extremely narrow optical equivalent filter of the CPT reduces noise, generating a low-phase-noise microwave signal. Furthermore, locking the 6.8 GHz microwave signal to a crystal oscillator improves the signal's stability. This invention combines the stability of a CPT atomic clock with the low phase noise of a photoelectric oscillator, providing both high-stability and low-phase-noise microwave and time-frequency signals. Attached Figure Description

[0029] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0030] Figure 1 A schematic diagram of the photogenerated microwave source system of the present invention is shown.

[0031] 1. VCSEL laser; 2. Beam shaping module; 3. Rubidium bulb unit

[0032] 4. Photodetector; 5. First electrical amplifier module; 6. First coupler

[0033] 7 Voltage-controlled phase shifter; 8 Second electrical amplifier module; 9 Second coupler

[0034] 10. Frequency divider; 11. Crystal oscillator; 12. Phase detector module

[0035] 13 PID controller Detailed Implementation

[0036] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0037] This invention provides a photogenerated microwave source system and method that improves the stability of the microwave signal, enabling the provision of microwave signals with high stability and low phase noise, as well as time and frequency signals.

[0038] The first aspect of this invention provides a photoelectric microwave source system, which includes a light signal generation module, a photodetector, an electrical signal adjustment module, a crystal oscillator locking module, and a PID control module, wherein...

[0039] The optical signal generation module is used to generate the CPT phenomenon, and outputs a laser beam after optical filtering;

[0040] A photodetector is used to convert optical signals into electrical signals;

[0041] The electrical signal adjustment module is used to amplify the electrical signal output by the photodetector and split it through the first coupler;

[0042] The crystal oscillator locking module includes a crystal oscillator for modulating the second signal after beam splitting, dividing the modulated signal by a frequency divider, comparing the divided signal with the signal output by the crystal oscillator to form an error verification signal, and generating the microwave signal of the microwave source system.

[0043] The PID control module processes the error verification signal output by the crystal oscillator locking module to generate a voltage control signal for voltage control of the voltage-controlled phase shifter.

[0044] The optical signal generation module includes a VCSEL laser, a beam shaping module, and a rubidium bulb unit. The VCSEL laser is the system's light source and optical carrier, transmitting the modulated microwave signal. The beam shaping module is used to adjust the laser's polarization state and intensity distribution. Rubidium vapor exists in the rubidium bulb unit, and the hyperfine energy levels of the rubidium vapor atoms can form the CPT phenomenon under the excitation of external optical and electric fields.

[0045] The electrical signal adjustment module includes a first electrical amplification module and a first coupler. The first coupler splits the electrical signal passing through the first electrical amplification module. The first electrical signal after splitting passes through a voltage-controlled phase shifter and is then input to the VCSEL laser to form a closed loop.

[0046] The crystal oscillator locking module includes a second electrical amplifier module, a second coupler, a frequency divider, a crystal oscillator, and a phase detector module. The second electrical signal, after being split by the first coupler, is amplified by the second electrical amplifier module and then enters the second coupler. The second coupler splits the electrical signal from the second electrical amplifier module, and the split first electrical signal enters the frequency divider, with the second signal being output as a 6.8GHz microwave signal. The frequency divider is used to divide the electrical signal output by the second coupler from the high frequency of 6.8GHz to around 10MHz. The phase detector module includes a phase detector, which is used to perform phase measurement on the first signal output by the second coupler and the signal output by the crystal oscillator. The phase difference is used to determine the fluctuation level of the microwave signal, and the error verification signal formed after phase detection is output to the PID control module.

[0047] The PID control module includes a PID controller and a voltage-controlled phase shifter. The PID controller processes the error verification signal output from the phase detection module to generate a voltage control signal, which controls the voltage-controlled phase shifter. The voltage-controlled phase shifter controls the phase of the 6.8GHz microwave signal through a slowly varying voltage, thus controlling the time delay. The voltage-controlled phase shifter controls the phase of the first signal output from the first coupler based on the voltage control signal output from the PID controller. The voltage-controlled phase shifter can be considered a three-port device; two ports transmit the microwave signal, and the remaining port is fitted with a bias voltage or a slowly varying voltage.

[0048] In one specific embodiment, for example, the fourth electrical signal is a 6.8GHz microwave signal. After passing through a frequency divider, a 10MHz signal is obtained. This 10MHz signal is phase-detected with the 10MHz of the crystal oscillator. The fluctuation level of the microwave signal is judged by the phase difference, forming an error verification signal. The PID controller processes the error verification signal and then controls the voltage-controlled phase shifter to improve the stability of the 6.8GHz microwave signal.

[0049] In one specific embodiment, the connection method of the photogenerated microwave source system provided by the present invention is as follows:

[0050] The output of the VCSEL laser is connected to the input of the beam shaping module. The output of the beam shaping module is connected to the input of the rubidium bulb unit. The output of the rubidium bulb unit is connected to the input of the photodetector. The output of the photodetector is connected to the input of the first electrical amplifier module. The output of the first electrical amplifier module is connected to the first coupler. One end of the output of the first coupler is connected to the input of the voltage-controlled phase shifter, and the other end is connected to the input of the second electrical amplifier module. The output of the second electrical amplifier module is connected to the input of the second coupler. One end of the output of the second coupler is connected to the input of the frequency divider, and the other output port outputs a 6.8 GHz microwave signal. The outputs of the frequency divider and the crystal oscillator are both connected to the input of the phase detector module. The other output of the crystal oscillator outputs a 10 MHz time signal. The output of the phase detector module is connected to the input of the PID controller. The output of the PID controller is connected to the input of the voltage-controlled phase shifter, and the output of the voltage-controlled phase shifter is connected to the input of the VCSEL laser.

[0051] A second aspect of the present invention provides a method for generating a photomicrowave source, the method comprising:

[0052] The light source generated by the VCSEL laser is passed through a rubidium metal gas cell to produce the CTP phenomenon, forming an optical filter, and then the laser beam is output after optical filtering;

[0053] The filtered optical signal is converted into an electrical signal by a photodetector.

[0054] The electrical signal is amplified and modulated. The modulated electrical signal is split by the first coupler. The first electrical signal after splitting is connected to the VCSEL laser through the voltage-controlled phase shifter to form a closed loop.

[0055] The second signal after beam splitting is amplified and modulated, and the modulated signal is input to the frequency divider for frequency division. The frequency-divided signal is phase-detected with the first signal output by the crystal oscillator and an error verification signal is formed. The crystal oscillator locking module generates the microwave signal of the microwave source system, and the second signal output by the crystal oscillator is used as the standard time signal of the microwave source system.

[0056] The PID control module processes the error verification signal generated after phase detection to form a voltage control signal to control the voltage-controlled phase shifter.

[0057] Specifically, the optical signal generation module, photodetector, electrical signal adjustment module, and voltage-controlled phase shifter form a closed loop. The closed loop is a positive feedback loop, and a microwave signal will be generated when the gain of the closed loop is greater than the loss.

[0058] Low phase noise is achieved through optical filtering utilizing the CPT phenomenon. The optical equivalent filter of CPT is extremely narrow, reducing noise. High stability is achieved through the locking module of the crystal oscillator.

[0059] In one specific embodiment, according to Figure 1 The circuit assembly process involves using a VCSEL semiconductor laser with an output wavelength of 794nm. The light emitted by the VCSEL laser is shaped by a beam shaping module into circularly polarized light with a small divergence angle. This light then illuminates a rubidium bulb unit, which consists of a glass bulb containing rubidium 87 gas, a coil wound around the bulb, and a temperature control system. The rubidium bulb unit is filled with rubidium vapor, and the hyperfine energy levels of the rubidium vapor atoms can form the CPT phenomenon under the excitation of external light and electric fields. The light passing through the rubidium bulb unit is detected by a photodetector, which converts the optical signal into an electrical signal. This signal is then processed by a first... The amplification module amplifies the electrical signal, which is then split by the first coupler. The first electrical signal is connected to the VCSEL laser via a voltage-controlled phase shifter, forming a closed loop. The second electrical signal from the first coupler is amplified by the second amplification module and then enters the second coupler. After being split by the second coupler, the first signal from the second coupler enters the frequency divider for frequency division. The frequency-divided signal and the 10MHz signal output from the crystal oscillator are input to the phase detection module for phase detection and to form an error verification signal. The error verification signal after phase detection is used by a PID controller to generate a voltage-controlled voltage to control the voltage-controlled phase shifter. The second signal from the second coupler is used as the output of the 6.8GHz microwave signal, and the second signal from the crystal oscillator is used as the output of the 10MHz standard time signal of the microwave source system.

[0060] In the description of this invention, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0061] It should also be noted that in the description of this invention, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0062] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A photogenerated microwave source system, characterized in that, The system includes: an optical signal generation module, a photodetector, an electrical signal adjustment module, a crystal oscillator locking module, and a PID control module. The optical signal generation module is used to generate the CPT phenomenon and output a laser beam after optical filtering; The photodetector is used to convert optical signals into electrical signals; The electrical signal adjustment module is used to amplify the electrical signal output by the photodetector and split it through the first coupler; The crystal oscillator locking module includes a crystal oscillator for modulating the second signal after beam splitting, dividing the modulated signal by a frequency divider, comparing the divided signal with the signal output by the crystal oscillator to form an error verification signal, and generating the microwave signal of the microwave source system. The PID control module is used to process the error verification signal output by the crystal oscillator locking module to form a voltage control signal to control the voltage-controlled phase shifter. The electrical signal adjustment module includes a first electrical amplification module and a first coupler. The first coupler splits the electrical signal that has passed through the first electrical amplification module. The first electrical signal after splitting passes through a voltage-controlled phase shifter and is then input to the VCSEL laser to form a closed loop. The crystal oscillator locking module includes a second electrical amplifier module, a second coupler, a frequency divider, a crystal oscillator, and a phase detector module. The second electrical signal after being split by the first coupler is amplified by the second electrical amplifier module and then enters the second coupler. The second coupler splits the electrical signal, and the first signal of the second coupler enters the frequency divider. The second signal of the second coupler is output as a 6.8 GHz microwave signal. The second signal output by the crystal oscillator serves as the standard time signal for the microwave source system. The frequency divider is used to divide the first signal output by the second coupler.

2. The system according to claim 1, characterized in that, The optical signal generation module includes a VCSEL laser and a rubidium bulb unit, which generates the CPT phenomenon under the excitation of an external optical field and an electric field.

3. The system according to claim 2, characterized in that, The system also includes a beam shaping module located between the VCSEL laser and the rubidium bulb unit, the beam shaping module being used to shape the light generated by the VCSEL laser into circularly polarized light.

4. The system according to claim 1, characterized in that, The phase detection module is used to perform phase calculation on the frequency-divided signal and the signal output by the crystal oscillator, and output the phase detection result to the PID control module.

5. The system according to claim 1, characterized in that, The PID control module includes a PID controller and a voltage-controlled phase shifter. The PID controller processes the phase detection result and generates a voltage control signal to control the voltage-controlled phase shifter.

6. A method for generating microwaves by light, characterized in that, This method comprises a photogenerated microwave source system according to any one of claims 1-5, the method including... The light source generated by the VCSEL laser is passed through a rubidium metal gas cell to produce the CTP phenomenon, forming an optical filter, and then the laser beam is output after optical filtering; The filtered optical signal is converted into an electrical signal by a photodetector. The electrical signal is amplified and modulated. The modulated electrical signal is split by the first coupler. The first signal after splitting is connected to the VCSEL laser through the voltage-controlled phase shifter to form a closed loop. The second signal after beam splitting is amplified and modulated, and the modulated signal is input to the frequency divider for frequency division. The frequency-divided signal is phase-detected with the first signal output by the crystal oscillator and an error verification signal is formed. The crystal oscillator locking module generates the microwave signal of the microwave source system, and the second signal output by the crystal oscillator is used as the standard time signal of the microwave source system. The PID control module processes the error verification signal generated after phase detection to form a voltage control signal to control the voltage-controlled phase shifter.

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