Low phase noise microwave generation system and method

Abstract

The invention provides a low-phase-noise microwave generation system and method, which can be applied to the technical field of microwaves, and the system comprises a mode-locked laser used for generating an optical pulse signal with repetition frequency, a modulator used for dividing the optical pulse signal into two beams and modulating a microwave signal to one beam of optical pulse signal to obtain a first modulation signal, and performing direct current signal bias on the other beam of light pulse signal to obtain a second modulation signal, performing interference on the first modulation signal and the second modulation signal to obtain two beams of light pulses containing phase difference information, and performing balance detection on the two beams of light pulses containing the phase difference information by the balance detector, the dielectric oscillator is used for generating phase difference information and outputting a voltage signal linearly related to the phase difference information, the controller performs linear control processing on the voltage signal and outputs a linear control signal, and the dielectric oscillator is used for generating a microwave signal and controlling frequency jitter of the microwave signal through the linear control signal. And the frequency stability on the optical domain can be transmitted to the microwave domain in a high-fidelity manner.

Description

Technical Field

[0001] The present disclosure relates to the field of microwaves, and in particular to a low phase noise microwave generation system and method. Background Art

[0002] Microwave signals have been widely used in various scientific research and engineering practice fields such as wireless communication, measurement and control, and remote synchronization of large scientific devices. With the development of technology, microwave signals generated by microwave sources must develop in the direction of high frequency, low phase noise and large bandwidth. Traditional low phase noise microwave signals are mainly generated based on quartz crystal oscillators, low temperature sapphire oscillators and optoelectronic oscillators, but the above methods have their own defects: the phase noise of microwave signals generated based on quartz crystal oscillators will increase with the frequency multiplication factor; the microwave generation device based on low temperature sapphire oscillators has a complex structure and is not easy to apply; and the optoelectronic oscillator has low phase noise only at high frequency deviation. In comparison, the use of optical signals to generate microwave signals has higher short-term frequency stability and ultra-low phase noise. At present, the use of laser pulse signals to generate microwave signals usually uses fiber sagnac loops to realize microwave photon phase detection, but this solution is relatively complicated, and the fiber loop and the spatial optical devices therein are large and difficult to integrate, and the loop needs to be finely controlled during phase detection. Summary of the invention

[0003] In view of the above problems, the present disclosure provides a low phase noise microwave generation system and method.

[0004] According to a first aspect of the present disclosure, a low phase noise microwave generation system is provided, characterized in that it comprises:

[0005] A mode-locked laser for generating an optical pulse signal with a stable repetition frequency;

[0006] a dual-output Mach-Zehnder modulator, used to divide the optical pulse signal into two beams, modulate the received microwave signal onto one beam of the optical pulse signal to obtain a first modulation signal, the first modulation signal carries the phase information of the microwave signal, bias the other beam of the optical pulse signal with a DC signal to obtain a second modulation signal, interfere the first modulation signal with the second modulation signal, convert the phase difference information into light intensity difference information, and obtain two optical pulses containing the phase difference information;

[0007] a balanced detector, used for performing balanced detection on the two light pulses containing phase difference information, and outputting a voltage signal which is linearly related to the phase difference information;

[0008] a controller, configured to perform linear control processing on the voltage signal and output a linear control signal;

[0009] A dielectric oscillator is used to generate the microwave signal and control the frequency jitter of the microwave signal through the linear control signal.

[0010] According to an embodiment of the present disclosure, the balanced detector includes two photodiodes and a differential module;

[0011] Each of the two photodiodes is used to perform balanced detection on one of the two light pulses containing phase difference information, and convert it into an electrical signal containing light intensity information;

[0012] The differential module is used to perform differential processing on two electrical signals containing light intensity difference information, and output a voltage signal that is linearly related to the phase difference information.

[0013] According to an embodiment of the present disclosure, the controller includes a proportional module and an integral module;

[0014] The proportional module is used to perform linear control processing on the voltage signal and output the linear control signal;

[0015] The integration module is used to eliminate the steady-state error of the linear control signal.

[0016] According to an embodiment of the present disclosure, the time period of the optical pulse signal and the repetition frequency of the comb teeth in the frequency domain are reciprocals of each other.

[0017] According to an embodiment of the present disclosure, the frequency of the microwave signal is an integer multiple of the repetition frequency of the optical pulse signal.

[0018] According to an embodiment of the present disclosure, the mode-locked laser is a passive mode-locked laser.

[0019] According to an embodiment of the present disclosure, the dielectric oscillator is a voltage-controlled oscillator.

[0020] According to an embodiment of the present disclosure, the dual-output Mach-Zehnder modulator is an electro-optic modulator.

[0021] A second aspect of the present disclosure provides a low phase noise microwave generation method, comprising:

[0022] generating an optical pulse signal with a stable repetition frequency;

[0023] The optical pulse signal is divided into two beams, and the received microwave signal is modulated onto one beam of the optical pulse signal to obtain a first modulated signal, wherein the first modulated signal carries the phase information of the microwave signal, and the other beam of the optical pulse signal is biased with a DC signal to obtain a second modulated signal, and the first modulated signal and the second modulated signal are interfered to convert the phase difference information into light intensity difference information to obtain two optical pulses containing the phase difference information;

[0024] Performing balanced detection on the two light pulses containing phase difference information, and outputting a voltage signal that is linearly related to the phase difference information;

[0025] Performing linear control processing on the voltage signal and outputting a linear control signal;

[0026] The microwave signal is generated, and the frequency jitter of the microwave signal is controlled by the linear control signal.

[0027] According to an embodiment of the present disclosure, the frequency of the microwave signal is an integer multiple of the repetition frequency of the optical pulse signal.

[0028] According to the embodiments provided by the present disclosure, the present disclosure has at least the following technical effects:

[0029] (1) The phase jitter of the microwave signal is extracted through a dual-output Mach-Zehnder modulator and modulated onto an optical pulse signal. The optical pulse signal interferes at the output port of the dual-output Mach-Zehnder modulator, converts the phase information into light intensity information, and converts it into a voltage signal through balanced detection. After being processed by a controller, it is used to feedback control the output of the dielectric oscillator to obtain a microwave signal with low phase noise.

[0030] (2) Photonic technology is used to transfer the frequency stability in the optical domain to the microwave domain with high fidelity, greatly reducing the phase jitter of the microwave signal.

[0031] (3) Compared with the prior art, the system disclosed in the present invention has a simpler composition, is easy to implement single-chip integration and feedback control, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above contents and other purposes, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0033] Figure 1 The structure diagram of the low phase noise microwave generation system according to the embodiment of the present disclosure is schematically shown;

[0034] Figure 2 The flowchart of the method for generating low phase noise microwaves according to an embodiment of the present disclosure is schematically shown.

[0035] Description of reference numerals:

[0036] 1-mode-locked laser; 2-dual-output Mach-Zehnder modulator; 3-balanced detector; 4-controller; 5-dielectric oscillator. DETAILED DESCRIPTION

[0037] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0038] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "include", "comprising", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0039] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

[0040] When using expressions such as "at least one of A, B, and C, etc.", they should generally be interpreted according to the meaning of the expression commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0041] Figure 1 The structure diagram of a low phase noise microwave generation system according to an embodiment of the present disclosure is schematically shown.

[0042] like Figure 1 As shown, the low phase noise microwave generation system includes: a mode-locked laser 1, a dual-output Mach-Zehnder modulator 2, a balanced detector 3, a controller 4 and a dielectric oscillator 5.

[0043] The mode-locked laser 1 is used to generate an optical pulse signal with a repetition frequency.

[0044] The dual-output Mach-Zehnder modulator 2 is used to divide the optical pulse signal into two beams, modulate the received microwave signal onto one beam of the optical pulse signal to obtain a first modulation signal, the first modulation signal carries the phase information of the microwave signal, bias the other beam of the optical pulse signal with a DC signal to obtain a second modulation signal, interfere the first modulation signal and the second modulation signal, convert the phase difference information into light intensity difference information, and obtain two optical pulses containing phase difference information.

[0045] The balanced detector 3 is used to perform balanced detection on the two light pulses containing phase difference information and output a voltage signal which is linearly related to the phase difference information.

[0046] The controller 4 is used for performing linear control processing on the voltage signal and outputting a linear control signal.

[0047] The dielectric oscillator 5 is used to generate the microwave signal and control the frequency jitter of the microwave signal through the linear control signal.

[0048] It can be understood that the devices such as the mode-locked laser 1, the dual-output Mach-Zehnder modulator 2 and the balanced detector 3 in the low phase noise microwave generation system provided by the present disclosure can be monolithically integrated to achieve small-volume and modular applications.

[0049] In one embodiment of the present disclosure, the frequency of the microwave signal is an integer multiple of the repetition frequency of the optical pulse signal, so that more accurate phase jitter information can be obtained.

[0050] In one embodiment of the present disclosure, the mode-locked laser 1 is a passive mode-locked laser with a higher repetition frequency stability. The time period of the optical pulse signal and the repetition frequency of the comb teeth in the frequency domain are reciprocal to each other, that is, T r =1 / f r .

[0051] In one embodiment of the present disclosure, the dual-output Mach-Zehnder modulator 2 is an electro-optical modulator. Its specific structure may include a Y-type beam splitter, two phase modulation arms and a 2×2 coupler. The optical pulse signal is divided into two paths in the Mach-Zehnder modulator, which are modulated by microwave signals and biased by DC signals respectively, to generate phase differences, and interfere at the output port of the Mach-Zehnder modulator.

[0052] In one embodiment of the present disclosure, the balanced detector 3 includes two photodiodes and a differential module. Each of the two photodiodes is used to perform balanced detection on one of the two light pulses containing phase difference information, and convert it into an electrical signal containing light intensity information. The differential module is used to perform differential processing on the two electrical signals containing light intensity difference information, and output a voltage signal that is linearly related to the phase difference information.

[0053] In one embodiment of the present disclosure, the controller 4 includes a proportional module and an integral module. The proportional module is used to perform linear control processing on the voltage signal and output the linear control signal. The integral module is used to eliminate the steady-state error of the linear control signal.

[0054] In one embodiment of the present disclosure, the dielectric oscillator 5 is a voltage-controlled oscillator.

[0055] The following specific embodiments are listed to illustrate the technical solution of the present invention in detail. It should be noted that the following specific embodiments are only used for illustration and are not used to limit the present invention.

[0056] Assume that the angular frequency of the input microwave signal in the present invention is ω RF , θ is the phase difference between the zero-crossing point of the microwave signal and the center of the optical pulse signal, then the phase difference introduced on the dual-output Mach-Zehnder modulator 2 is for:

[0057]

[0058] Where β is the modulation coefficient. Assuming that the central wavelength of the input optical pulse signal is around 1550nm, the optical pulse signal can be expressed as E 0 , the optical power is P 0 , after being modulated by the microwave signal, the phase of the optical pulse signal changes:

[0059]

[0060] The phase information of the microwave signal is loaded on the optical pulse signal through modulation. The other optical pulse signal is affected by the DC bias to produce a fixed π phase difference. The two optical pulse signals interfere in the 2×2 coupler and output the optical power P of the two optical pulses containing the phase difference information. 1 , P 2 for:

[0061]

[0062] Assuming that the transconductance gain of the balanced detector 3 is G, and the responsivity of the balanced photodetector is R, the power difference of the two light pulses containing phase difference information is detected by the balanced detector 3 and converted into a voltage signal. The voltage value output by the balanced detector 3 is:

[0063]

[0064] When the microwave signal frequency is equal to the optical pulse repetition frequency f r The integer multiple of ω RF =2πnf r When the pulse time period is T r , only when t=mT r When the optical pulse signal can be sampled, the voltage of the voltage signal that is linearly related to the phase difference information output by the balanced detector 3 is:

[0065] V d =GRP 0 sin(βsinθ)

[0066] In the case of a small phase difference, the balanced detector 3 outputs a voltage V d It is approximately linearly related to the phase difference θ of the microwave signal. When the microwave signal produces phase jitter, the output voltage of the balanced detector 3 will also change.

[0067] The voltage signal is processed by the controller 4 to form a feedback voltage, thereby controlling the dielectric oscillator 5 to output a microwave signal with low phase noise.

[0068] Figure 2 The flowchart of the method for generating low phase noise microwaves according to an embodiment of the present disclosure is schematically shown.

[0069] like Figure 2 As shown, the low phase noise microwave generation method includes operations S210 to S250.

[0070] In operation S210 , an optical pulse signal having a stable repetition frequency is generated.

[0071] In operation S220, the optical pulse signal is divided into two beams, and the received microwave signal is modulated onto one beam of the optical pulse signal to obtain a first modulation signal, which carries the phase information of the microwave signal. The other beam of the optical pulse signal is biased with a DC signal to obtain a second modulation signal. The first modulation signal and the second modulation signal are interfered, and the phase difference information is converted into light intensity difference information to obtain two optical pulses containing phase difference information.

[0072] In operation S230, the two light pulses containing phase difference information are subjected to balanced detection, and a voltage signal linearly correlated with the phase difference information is output.

[0073] In operation S240, a linear control process is performed on the voltage signal to output a linear control signal.

[0074] In operation S250, the microwave signal is generated, and the frequency jitter of the microwave signal is controlled by the linear control signal.

[0075] In one embodiment, operation S210 may be performed by a mode-locked laser to generate a microwave signal with a frequency that is an integer multiple of a repetition frequency of the optical pulse signal.

[0076] In one embodiment, operation S220 can be performed by a dual-output Mach-Zehnder modulator to modulate a microwave signal onto an optical pulse, and the microwave signal is sampled using the optical pulse signal. The modulated optical pulse signal carries the phase information of the microwave signal and interferes with another optical pulse with a fixed phase difference introduced by a DC bias at the output port of the modulator to generate two optical pulses containing phase difference information.

[0077] In one embodiment, operation S230 can be performed using a balanced detector to perform balanced detection on two optical pulses containing phase difference information output by a dual-output Mach-Zehnder modulator. After interference, the phase difference information between the microwave signal and the optical pulse signal is converted into two-path pulse light intensity difference information. Unnecessary DC components can be offset by balanced detection, and a voltage signal linearly related to the phase difference can be output.

[0078] In one embodiment, a proportional-integral controller may be used to perform operation S240, and a dielectric oscillator may perform operation S250 to perform proportional and integral processing on the voltage signal to eliminate the steady-state error of the system, and output a voltage signal linearly related to the phase difference information to control the dielectric oscillator to generate a microwave signal with low phase noise.

[0079] It will be appreciated by those skilled in the art that the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in a variety of ways, even if such combinations and / or combinations are not explicitly described in the present disclosure. In particular, the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in a variety of ways without departing from the spirit and teachings of the present disclosure. All of these combinations and / or combinations fall within the scope of the present disclosure.

[0080] The embodiments of the present disclosure are described above. However, these embodiments are only for illustrative purposes and are not intended to limit the scope of the present disclosure. Although the embodiments are described above separately, this does not mean that the measures in the various embodiments cannot be used in combination to advantage. The scope of the present disclosure is defined by the attached claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art may make a variety of substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A low phase noise microwave generation system, characterized in that: include: A mode-locked laser for generating an optical pulse signal with a stable repetition frequency; a dual-output Mach-Zehnder modulator, used to divide the optical pulse signal into two beams, modulate the received microwave signal onto one beam of the optical pulse signal to obtain a first modulation signal, the first modulation signal carries the phase information of the microwave signal, bias the other beam of the optical pulse signal with a DC signal to obtain a second modulation signal, interfere the first modulation signal with the second modulation signal, convert the phase difference information into light intensity difference information, and obtain two optical pulses containing the phase difference information; a balanced detector, used for performing balanced detection on the two light pulses containing phase difference information, and outputting a voltage signal which is linearly related to the phase difference information; a controller, configured to perform linear control processing on the voltage signal and output a linear control signal; A dielectric oscillator is used to generate the microwave signal and control the frequency jitter of the microwave signal through the linear control signal.

2. The low phase noise microwave generation system according to claim 1, characterized in that: The balanced detector includes two photodiodes and a differential module; Each of the two photodiodes is used to perform balanced detection on one of the two light pulses containing phase difference information, and convert it into an electrical signal containing light intensity information; The differential module is used to perform differential processing on two electrical signals containing light intensity information and output a voltage signal that is linearly correlated with the phase difference information.

3. The low phase noise microwave generation system according to claim 1, characterized in that: The controller includes a proportional module and an integral module; The proportional module is used to perform linear control processing on the voltage signal and output the linear control signal; The integration module is used to eliminate the steady-state error of the linear control signal.

4. The low phase noise microwave generation system according to claim 1, characterized in that: The time period of the optical pulse signal and the repetition frequency of the comb teeth in the frequency domain are reciprocal to each other.

5. The low phase noise microwave generation system according to claim 1, characterized in that: The frequency of the microwave signal is an integer multiple of the repetition frequency of the optical pulse signal.

6. The low phase noise microwave generation system according to claim 1, characterized in that: The mode-locked laser is a passive mode-locked laser.

7. The low phase noise microwave generation system according to claim 1, characterized in that: The dielectric oscillator is a voltage-controlled oscillator.

8. The low phase noise microwave generation system according to claim 1, characterized in that: The dual-output Mach-Zehnder modulator is an electro-optic modulator.

9. A method for generating low phase noise microwaves, characterized in that: include: generating an optical pulse signal having a repetition frequency; The optical pulse signal is divided into two beams, and the received microwave signal is modulated onto one beam of the optical pulse signal to obtain a first modulated signal, wherein the first modulated signal carries the phase information of the microwave signal, and the other beam of the optical pulse signal is biased with a DC signal to obtain a second modulated signal, and the first modulated signal and the second modulated signal are interfered to convert the phase difference information into light intensity difference information to obtain two optical pulses containing the phase difference information; Performing balanced detection on the two light pulses containing phase difference information, and outputting a voltage signal that is linearly related to the phase difference information; Performing linear control processing on the voltage signal and outputting a linear control signal; The microwave signal is generated, and the frequency jitter of the microwave signal is controlled by the linear control signal.

10. The method for generating low phase noise microwaves according to claim 9, characterized in that: The frequency of the microwave signal is an integer multiple of the repetition frequency of the optical pulse signal.

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