Tunable frequency locking device with ultra-large dynamic range

Abstract

The invention relates to the technical field of microwave laser, in particular to an ultra-large dynamic range tunable frequency locking device, which is characterized in that a frequency generation module is composed of a laser device of which the frequency is to be locked; the signal extraction filtering module comprises a first filter and a first low-noise amplifier; the shunt frequency mixing module consists of a group of radio frequency switches, a plurality of groups of signal branches and a radio frequency source signal output circuit; the intermediate-frequency filtering module comprises a second filter and a second low-noise amplifier; the phase frequency detection module comprises a phase frequency detector, a first power divider and a direct digital frequency synthesizer; the servo control module is composed of a PID servo controller. According to the invention, a multi-branch signal processing mode is adopted, the advantages of large frequency range, flexibility and variability of a programmable radio frequency source are combined, the limitation of a traditional single channel by the working frequency of a device is broken through, and tunable frequency locking in an ultra-large frequency range is realized.

Description

Technical Field

[0001] The present application relates to the field of microwave laser technology, and in particular to an ultra-large dynamic range tunable frequency locking device. Background Art

[0002] Frequency locking technology is an important basic technology in the field of laser and microwave technology. It reduces line width, improves stability and coherence by locking the frequency signal. It has extremely wide applications in microwave and photonic technology fields such as the generation and transmission of time-frequency benchmarks, cold atom manipulation and sensing, laser sensing and communications. It is also one of the most frequently used and widely used tools in the current field of quantum technology.

[0003] Frequency locking technology can usually be implemented through a frequency-locked loop or a phase-locked loop. By using a negative feedback loop, the frequency difference or phase difference of the comparison signal is locked at a fixed value, thereby achieving high-precision and high-stability frequency output.

[0004] In previous applications, the frequency locking requirement was usually only to achieve a fixed frequency lock, and there was no need to satisfy locking and tuning within a larger frequency range; however, with the development of microwave photonic technology, the demand for frequency locking and tuning within a large range has become increasingly urgent, especially in wide-band optical frequency synthesis. Due to the limited operating frequency of microwave devices, the problem of large-range frequency locking and tuning has not been effectively solved. Summary of the invention

[0005] The present application provides an ultra-large dynamic range tunable frequency locking device, which adopts a method of integrating multi-branch frequency segmentation processing, programmable mixing, and local oscillator tunable frequency and phase detection technical means to overcome the problems of small dynamic range and inconvenient tuning in current frequency locking technology.

[0006] In order to achieve the above-mentioned purpose, the present application provides an ultra-large dynamic range tunable frequency locking device, comprising a frequency generating module, a signal extraction and filtering module, a branch mixing module, an intermediate frequency filtering module, a frequency detection and phase detection module and a servo control module connected in sequence, wherein: the frequency generating module is composed of a laser device of the frequency to be locked; the signal extraction and filtering module includes a first filter and a first low-noise amplifier; the branch mixing module is composed of a group of radio frequency switches, multiple groups of signal branches and a radio frequency source signal output circuit, and is used to select a group of signal branches through the radio frequency switch according to the target value of the beat frequency locking, and mix with the radio frequency source signal output circuit to generate a mixed signal; the intermediate frequency filtering module includes a second filter and a second low-noise amplifier; the frequency detection and phase detection module includes a frequency detection and phase detection device, a first power divider and a direct digital frequency synthesizer; the servo control module is composed of a PID servo controller.

[0007] Furthermore, the frequency to be locked of the laser device has a range of DC to 15 GHZ, and the frequency locking value is tunable.

[0008] Furthermore, each group of signal branches is provided with a mixer.

[0009] Furthermore, the RF source signal output circuit includes a programmable RF source, a third low noise amplifier and a second power divider, wherein: the programmable RF source is connected to the second power divider through the third low noise amplifier; the second power divider is connected to the mixer on each group of signal branches.

[0010] Furthermore, the output signal of the coupling end of the first power divider is directly used for evaluating the locking result, and the output signal of the through end is transmitted to the frequency and phase detector.

[0011] Furthermore, the direct digital frequency synthesizer outputs a reference signal to the phase frequency detector, and the reference signal and the through-end output signal of the first power divider form an error signal in the phase frequency detector.

[0012] Furthermore, a third filter is provided between the frequency and phase detector and the servo control module.

[0013] Furthermore, the servo control module calculates the received error signal to obtain a feedback control voltage, and loads the feedback control voltage to the feedback control terminal of the frequency generation module.

[0014] The present application provides an ultra-large dynamic range tunable frequency locking device, which has the following beneficial effects:

[0015] This application adopts a multi-branch signal processing method, combined with the advantages of a programmable RF source with a large frequency range and flexible variability, breaking through the limitations of the traditional single-channel device operating frequency, and realizing tunable frequency locking in an ultra-large frequency range, providing a more flexible frequency locking method for laser communications, time-frequency transmission and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings constituting a part of this application are used to provide a further understanding of this application, so that other features, purposes and advantages of this application become more obvious. The schematic embodiment drawings and their descriptions of this application are used to explain this application and do not constitute an improper limitation on this application. In the drawings:

[0017] Figure 1 It is a schematic diagram of the module composition of the ultra-large dynamic range tunable frequency locking device provided in an embodiment of the present application;

[0018] Figure 2 It is a schematic diagram of the structure of a super-large dynamic range tunable frequency locking device provided in an embodiment of the present application;

[0019] In the figure: 1-frequency generating module, 2-first filter, 3-first low noise amplifier, 4, 10-RF switch, 5-programmable RF source, 6-third low noise amplifier, 7-first power divider, 8, 9-mixer, 11-second filter, 12-second low noise amplifier, 13-second power divider, 14-direct digital frequency synthesizer, 15-frequency detector, 16-third filter, 17-servo control module. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0021] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0022] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0023] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0024] In addition, the term "plurality" shall mean two or more.

[0025] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0026] like Figure 1-2 As shown, the present application provides a super-large dynamic range tunable frequency locking device, comprising a frequency generating module 1, a signal extraction and filtering module, a branch mixing module, an intermediate frequency filtering module, a frequency detection and phase detection module and a servo control module 17 connected in sequence, wherein: the frequency generating module 1 is composed of a laser device of a frequency to be locked; the signal extraction and filtering module comprises a first filter 2 and a first low noise amplifier 3; the branch mixing module is composed of a group of radio frequency switches (4, 10), multiple groups of signal branches and a radio frequency source signal output circuit, and is used to select a group of signal branches through the radio frequency switches (4, 10) according to the target value of the beat frequency locking, and mix with the radio frequency source signal output circuit to generate a mixed signal; the intermediate frequency filtering module comprises a second filter 11 and a second low noise amplifier 12; the frequency detection and phase detection module comprises a frequency detection and phase detection device 15, a first power divider 7 and a direct digital frequency synthesizer 14; the servo control module 17 is composed of a PID servo controller.

[0027] Specifically, the ultra-large dynamic range tunable frequency locking device provided in the embodiment of the present application utilizes a multi-branch mixing processing method to break through the limitation that the operating frequency of the RF device is difficult to cover high and low frequencies at the same time, and utilizes the mixing method with the programmable RF source 5 to convert the ultra-large range of the signal frequency to be locked to the vicinity of the phase-locking frequency, and then obtains the frequency deviation signal through frequency and phase detection, and finally uses frequency locking servo control to achieve wide range, tunable frequency locking.

[0028] More specifically, the frequency signal to be locked generated by laser beat frequency or other methods in the embodiment of the present application is filtered, extracted and power amplified, and then divided into several signal branches according to the range of the signal frequency, each branch is used to process signals in different frequency ranges, and the branches are switched by radio frequency switches (4, 10); in each processing branch, the frequency signal to be locked is mixed with the programmable radio frequency source 5; by setting the output frequency of the programmable radio frequency source 5, the frequency of the signal after mixing and filtering is made equivalent to the reference frequency output by the direct digital frequency synthesizer 14; and the frequency error signal after frequency discrimination is input into the servo control module 17, and after proportional, integral and other operations, it is used to feedback control the frequency generation module to be locked 1 to achieve frequency locking. That is, the problem of limited operating frequency of radio frequency devices is solved by multi-branch signal processing, signal processing in a super-large frequency range is achieved, and the frequency to be locked is converted into a frequency value suitable for the frequency discrimination phase detector 15; after the frequency is locked, the frequency discrimination reference signal output by the direct digital frequency synthesizer 14 is fine-tuned to achieve the tunable function of the locked frequency.

[0029] Furthermore, the range of the frequency to be locked of the laser device to be frequency-locked is DC to 15 GHz, and the frequency locking value is tunable. The range of the frequency to be locked can cover several megahertz to tens of gigahertz, and the frequency locking value is tunable, and tunable frequency locking within the range of DC to 15 GHz can be achieved.

[0030] Furthermore, each group of signal branches is provided with a mixer (8, 9). The radio frequency switch (4, 10) is used to divide the signal processing into several branches, so as to solve the problem of limited working frequency of radio frequency devices, thereby realizing ultra-large dynamic range frequency setting without limiting the number of branches; the locking frequency is converted into a phase detection frequency by the mixer (8, 9).

[0031] Furthermore, the RF source signal output circuit includes a programmable RF source 5, a third low noise amplifier 6 and a second power divider 13, wherein: the programmable RF source 5 is connected to the second power divider 13 through the third low noise amplifier 6; the second power divider 13 is connected to the mixer (8, 9) on each group of signal branches. The programmable RF source 5 is used as a local oscillator for signal mixing, thereby converting the frequency to be locked in an ultra-large dynamic range to a phase detection frequency.

[0032] Furthermore, the output signal of the coupling end of the first power divider 7 is directly used for evaluating the locking result, and the output signal of the through end is transmitted to the frequency and phase detector 15 .

[0033] Furthermore, the direct digital frequency synthesizer 14 outputs a reference signal to the phase frequency detector 15, and the reference signal and the through-end output signal of the first power divider 7 form an error signal in the phase frequency detector 15. The local oscillator signal of the phase frequency detector is a frequency-tunable RF signal source, so that a small range tuning of the locking frequency can be achieved by changing the local oscillator frequency.

[0034] Furthermore, a third filter 16 is provided between the frequency detector 15 and the servo control module 17. The third filter 16 is a low-pass filter for filtering out high-frequency components in the differential signal.

[0035] Furthermore, the servo control module 17 calculates the received error signal to obtain a feedback control voltage, and loads the feedback control voltage to the feedback control terminal of the frequency generating module 1. The feedback control signal is generated by the servo control to achieve the final locking of the frequency.

[0036] The working process of the ultra-large dynamic range tunable frequency locking device provided by the present application is described in more detail below in conjunction with specific embodiments:

[0037] In the embodiment of the present application, the frequency generation module 1 is composed of a tunable laser, a microcavity optical comb and a photodetector, wherein the repetition frequency f of the microcavity optical comb is r is 30 GHz, and the frequency to be locked is the beat frequency signal f between the tunable laser and the microcavity optical comb.beat (0~15GHz). The beat frequency signal f converted and output by the photodetector beat After being extracted by the first filter 2 and amplified by the first low noise amplifier 3, a group of radio frequency switches (4, 10) switch the signal branches according to the frequency range of the beat frequency signal, one for processing low frequency signals in the frequency range of DC to 4 GHz, and the other for processing high frequency signals in the frequency range of 4 to 15 GHz. The target value f is locked according to the beat frequency. d The RF switch (4, 10) is controlled to select a RF mixer (8, 9) that matches the frequency thereof, and the low-noise local oscillator signal (f d +80MHz or f d -80MHz) for mixing, wherein the third low noise amplifier 6 is used to power amplify the signal of the radio frequency source; then, the 80MHz bandpass or low-pass second filter 11 is used to filter out the 80MHz mixing signal, which is then amplified by the second low noise amplifier 12 and input into the second power divider 13, the coupling end output signal of which is used for locking result evaluation, and the through end output signal is directly sent to the phase detection circuit and the 80MHz reference signal output by the direct digital frequency synthesizer 14 for frequency and phase detection to generate an error signal, the error signal is filtered out by the low-pass third filter 16 to remove the high-frequency component, and then sent to the high-performance digital PID servo control module 17, the feedback control voltage is calculated by the PID servo control module 17, and then loaded to the feedback control end of the tunable laser, so as to realize the precise locking of the tunable laser and the microcavity optical comb beat frequency signal, so that the tunable laser obtains the same stability as the microcavity optical comb teeth.

[0038] Specifically, the target value f of the beat frequency signal is calculated according to the frequency of the required tunable laser. d The tunable laser is roughly adjusted by wavelength adjustment to make the beat frequency signal close to f d When the beat frequency locks the target value f d The frequency of the programmable RF source 5 is set to P d +80MHz; when the beat frequency is locked to the target value f d When the frequency is greater than 4 GHz, the RF switch (4, 10) is turned on to select the high frequency branch, and the output frequency of the programmable RF source 5 is set to f d -80MHz; therefore, the signal to be locked after mixing processing is converted to around 80MHz, and the loop is locked after phase detection with the 80MHz reference signal generated by the direct digital frequency synthesizer 14; changing the output frequency of the direct digital frequency synthesizer 14 can achieve tuning of the beat frequency locking value.

[0039] More specifically, the embodiment of the present application adopts a multi-branch signal processing method, combined with the advantages of the programmable RF source 5 with a large frequency range and flexible variability, breaking through the limitations of the traditional single-channel device operating frequency, and realizing tunable frequency locking in an ultra-large frequency range, which can be used to lock the laser frequency to a reference laser or an optical frequency comb and other applications.

[0040] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An ultra-large dynamic range tunable frequency locking device, characterized in that: It includes a frequency generation module, a signal extraction and filtering module, a branch mixing module, an intermediate frequency filtering module, a frequency and phase discrimination module and a servo control module connected in sequence, wherein: The frequency generation module is composed of a laser device whose frequency is to be locked; The signal extraction and filtering module includes a first filter and a first low noise amplifier; The branch mixing module is composed of a group of RF switches, multiple groups of signal branches and a RF source signal output circuit, and is used to select a group of signal branches through the RF switch according to the target value of the beat frequency locking, and mix with the RF source signal output circuit to generate a mixed signal; The intermediate frequency filtering module includes a second filter and a second low noise amplifier; The frequency and phase detection module includes a frequency and phase detector, a first power divider and a direct digital frequency synthesizer; The servo control module is composed of a PID servo controller.

2. The ultra-large dynamic range tunable frequency locking device according to claim 1, characterized in that: The frequency to be locked of the laser device to be frequency locked has a range of DC to 15 GHZ, and the frequency locking value is tunable.

3. The ultra-large dynamic range tunable frequency locking device according to claim 2, characterized in that: Each group of signal branches is provided with a mixer.

4. The ultra-large dynamic range tunable frequency locking device according to claim 3, characterized in that: The radio frequency source signal output circuit comprises a programmable radio frequency source, a third low noise amplifier and a second power divider, wherein: The programmable radio frequency source is connected to the second power divider via the third low noise amplifier; The second power divider is connected to the mixer on each group of the signal branches.

5. The ultra-large dynamic range tunable frequency locking device according to claim 4, characterized in that: The output signal of the coupling end of the first power divider is directly used for locking result evaluation, and the output signal of the through end is transmitted to the frequency and phase detector.

6. The ultra-large dynamic range tunable frequency locking device according to claim 5, characterized in that: The direct digital frequency synthesizer outputs a reference signal to the phase frequency detector, and the reference signal and the through-end output signal of the first power divider form an error signal in the phase frequency detector.

7. The ultra-large dynamic range tunable frequency locking device according to claim 6, characterized in that: A third filter is arranged between the frequency detector and the servo control module.

8. The ultra-large dynamic range tunable frequency locking device according to claim 7, characterized in that: The servo control module calculates the received error signal to obtain a feedback control voltage, and loads the feedback control voltage to the feedback control terminal of the frequency generation module.

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