Optoelectronic-coordinated microwave photonic frequency synthesis system and frequency generation method

Abstract

This invention relates to a microwave photonic frequency synthesis system and frequency generation method based on optoelectronic coordination. The frequency synthesis system includes an optical frequency comb for generating a narrow optical pulse signal with high stability and low phase noise; an optical frequency doubling / division unit for doubling or dividing the repetition rate of the optical pulse signal output by the optical frequency comb; a photoelectric conversion unit for photoelectric conversion of the input optical pulse signal and outputting an electrical frequency comb; a second electrical filtering unit for filtering the input electrical signal; and a second electrical amplification unit for power amplification of the input electrical signal. In this invention, an optical frequency comb is used as the frequency source. Since the operating frequency of the optical frequency comb is more than three orders of magnitude higher than that of a conventional microwave source, its performance is also more than three orders of magnitude higher. Therefore, the frequency synthesis system of this invention can generate microwave frequency signals with a wider frequency range and superior performance.

Description

Technical Field

[0001] This invention belongs to the field of microwave photonic frequency synthesis technology, and relates to a microwave photonic frequency synthesis system based on optoelectronic coordination and a frequency generation method. Background Technology

[0002] Frequency synthesis is a supporting technology for radar, satellite and terrestrial communications, position sensing and navigation technologies, as well as many core defense capabilities. With the development needs of overcoming bottlenecks and upgrading electronic information systems, ultra-low phase noise and ultra-wideband frequency synthesizers have become one of the important areas and directions for the development of frequency synthesis technology. Furthermore, with the demand for miniaturization and higher performance of electronic systems, higher requirements are being placed on the miniaturization, frequency agility, fine stepping, low spurious emissions, and low phase noise design of frequency synthesizers.

[0003] Traditional low-phase-noise microwave signal generation utilizes microwave oscillators constructed from quartz crystals and dielectric resonators. While the phase noise of quartz oscillators can reach -160 dBc / Hz or even lower at a frequency deviation of 10 kHz, the output frequency is only a few tens of MHz. The Q value of a dielectric resonator decreases linearly with increasing output frequency. High-precision atomic clocks possess very high stability and excellent phase noise, typically with an output frequency of around 10 MHz. To generate higher frequencies, electrical frequency multiplication is required, but this degrades the phase noise logarithmically by a factor of 20, which no longer meets the demands of next-generation electronic information systems for high-frequency, highly stable, and low-phase-noise signals.

[0004] With the rapid development of microwave photonics technology, X-band signal generation based on optoelectronic oscillators has achieved a phase noise level of -163 dBc / Hz@6 kHz, while X-band signal generation based on optical frequency combs has achieved a phase noise level better than -170 dBc / Hz@10 kHz. However, in terms of frequency synthesis, due to limitations in tuning mechanisms, indicators such as phase noise and stability lag far behind those of point-frequency signal generation, necessitating research into new mechanisms for high-performance frequency synthesis. Summary of the Invention

[0005] To address the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a higher-performance optoelectronic synergistic microwave photonic frequency synthesis system and frequency generation method.

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

[0007] A microwave photonic frequency synthesis system based on optoelectronic coordination, including

[0008] Optical frequency combs are used to generate narrow optical pulse signals with high stability and low phase noise.

[0009] Optical frequency doubling / division unit is used to double or divide the repetition rate of the optical pulse signal output by the optical frequency comb.

[0010] The photoelectric conversion unit is used to realize the photoelectric conversion of the input optical pulse signal and output an electrical frequency comb;

[0011] The second electrical filtering unit is used to filter the input electrical signal; and

[0012] The second electrical amplifier unit is used to amplify the power of the input electrical signal;

[0013] The optical frequency comb is connected to the optical frequency doubling / division unit, the optical frequency doubling / division unit is connected to the photoelectric conversion unit, the photoelectric conversion unit is electrically connected to the second electrical filter unit, and the second electrical filter unit is electrically connected to the second electrical amplification unit.

[0014] Furthermore, it also includes an electrical routing unit, which is used to select the path of electrical signals; the photoelectric conversion unit is electrically connected to the second electrical filtering unit through the electrical routing unit.

[0015] Furthermore, it also includes a first electrical filtering unit and an electrical frequency synthesis unit. The first electrical filtering unit is used to select the frequency of the electrical frequency comb. The electrical frequency synthesis unit is used to output a synthesized frequency signal based on the frequency reference signal or local oscillator signal input to the first electrical filtering unit. The output terminal of the photoelectric conversion unit is electrically connected to the first input terminal of the electrical routing unit and the first electrical filtering unit, respectively. The first electrical filtering unit is electrically connected to the electrical frequency synthesis unit. The electrical frequency synthesis unit is electrically connected to the second input terminal of the electrical routing unit. The output terminal of the electrical routing unit is electrically connected to the second electrical filtering unit.

[0016] Furthermore, it also includes a first optical routing unit and a second optical routing unit. The first optical routing unit is used to select the path when performing optical splitting, and the second optical routing unit is used to select the path when performing optical combining. The optical frequency doubling / division unit is connected to the photoelectric conversion unit through the first optical routing unit and the second optical routing unit. The output terminal of the optical frequency doubling / division unit is connected to the input terminal of the first optical routing unit, the first output terminal of the first optical routing unit is connected to the first input terminal of the second optical routing unit, and the output terminal of the second optical routing unit is connected to the photoelectric conversion unit.

[0017] Furthermore, it also includes an optical splitter unit, an optical combiner unit, an optical frequency shifter unit, and a first electrical amplifier unit;

[0018] The optical splitting unit is used to split the optical pulse signal output from the second output terminal of the first optical routing unit into two paths, one of which is output to the optical combining unit and the other of which is output to the optical frequency shifting unit.

[0019] The optical combining unit is used to combine the optical pulses sent from the optical splitting unit and the optical frequency shifting unit into one path and then send it to the second input terminal of the second optical routing unit.

[0020] The optical frequency shifting unit is used to perform up or down frequency shifting processing on the optical pulse signal sent by the optical splitting unit according to the electrical frequency signal sent by the first electrical amplification unit;

[0021] The first electrical amplification unit is electrically connected to the electrical frequency synthesis unit and is used to amplify the electrical signal output by the electrical frequency synthesis unit before sending it to the optical frequency shifting unit.

[0022] A microwave photon frequency generation method based on optoelectronic coordination includes the following steps:

[0023] S1. After multiplying or dividing the narrow optical pulse signal generated by the optical frequency comb, can the frequency of the desired signal be obtained through photoelectric conversion? If yes, proceed to step S2; otherwise, proceed to step S3.

[0024] S2. The required signal is generated using a direct photoelectric conversion method;

[0025] S3. Is the frequency of the signal to be generated lower than the predetermined frequency threshold? If it is lower than the predetermined frequency threshold, proceed to step S4; otherwise, proceed to step S5.

[0026] S4. The required signal is generated using an electrical frequency synthesis method;

[0027] S5. The required signal is generated using an optical frequency shifting method.

[0028] Furthermore, generating the desired signal using the direct photoelectric conversion method includes the following steps:

[0029] S101. A narrow optical pulse signal with high stability and low phase noise is generated by an optical frequency comb;

[0030] S102. Perform frequency doubling or frequency division processing on the repetition frequency of the narrow optical pulse signal;

[0031] S103. Photoelectric conversion of narrow optical pulse signals to generate an electrical frequency comb;

[0032] S104. Filter the signal of the desired frequency from the electrical frequency comb by electrical filtering;

[0033] S105. Amplify the power of the filtered signal of the desired frequency.

[0034] Furthermore, the method of generating the desired signal using electrical frequency synthesis includes the following steps:

[0035] S201. A narrow optical pulse signal with high stability and low phase noise is generated by an optical frequency comb;

[0036] S202. Perform frequency doubling or frequency division processing on the repetition frequency of the narrow optical pulse signal;

[0037] S203. Photoelectric conversion of narrow optical pulse signals to generate an electrical frequency comb;

[0038] S204. Filter out a signal of a specific frequency from the electrical frequency comb through electrical filtering and use it as a frequency reference signal or local oscillator signal;

[0039] S205. Generate a synthesized frequency signal including the desired frequency by using the input frequency reference signal or local oscillator signal;

[0040] S206. Filter the desired frequency signal from the synthesized frequency signal using electrical filtering;

[0041] S207. Amplify the power of the filtered signal of the desired frequency.

[0042] Furthermore, generating the desired signal using an optical frequency shifting method includes the following steps:

[0043] S301, A narrow optical pulse signal with high stability and low phase noise is generated by an optical frequency comb;

[0044] S302. Perform frequency doubling or frequency division processing on the repetition rate of narrow optical pulse signals;

[0045] S303. The optical pulse signal after frequency doubling or frequency division is divided into two paths. The first optical pulse signal is optically shifted by the optical frequency shifting unit and then combined with the second optical pulse signal that has not been shifted into one path.

[0046] S304. The narrow optical pulse signal after frequency shifting is photoelectrically converted to generate an electrical frequency comb.

[0047] S305. The electrical frequency comb is divided into two paths. The first electrical frequency comb filters out a signal of a specific frequency through electrical filtering as a frequency reference signal or local oscillator signal, and generates a synthesized frequency signal accordingly. The synthesized frequency signal is then amplified to drive the optical frequency shift unit. The second electrical frequency comb filters out the signal of the required frequency through electrical filtering.

[0048] S306. Amplify the power of the filtered signal of the desired frequency.

[0049] In this invention, an optical frequency comb is used as the frequency source. Since the operating frequency of the optical frequency comb is more than three orders of magnitude higher than that of a conventional microwave source, its performance is also more than three orders of magnitude higher. Therefore, the frequency synthesis system of this embodiment can generate frequencies with a wider frequency range and higher performance. Furthermore, this embodiment can switch between three operating modes as needed: direct photoelectric conversion mode, electrical frequency synthesis mode, and optical frequency shifting mode. This allows for frequency shifting of the narrow optical pulse signal generated by the optical frequency comb, thereby obtaining a continuously tuned frequency signal. Attached Figure Description

[0050] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0051] Figure 1 This is a structural block diagram of a preferred embodiment of the optoelectronic synergistic microwave photonic frequency synthesis system of the present invention.

[0052] Figure 2 This is a structural block diagram of another preferred embodiment of the optoelectronic synergy-based microwave photonic frequency synthesis system of the present invention.

[0053] Figure 3 This is a structural block diagram of another preferred embodiment of the optoelectronic synergistic microwave photonic frequency synthesis system of the present invention.

[0054] Figure 4 This is a flowchart of a preferred embodiment of the microwave photon frequency generation method based on optoelectronic coordination of the present invention.

[0055] Figure 5 This is a flowchart illustrating how to generate the desired signal using a direct photoelectric conversion method.

[0056] Figure 6 This is a flowchart illustrating how to generate the desired signal using an electrical frequency synthesis method.

[0057] Figure 7 This is a flowchart illustrating how to generate the desired signal using an optical frequency shifting method. Detailed Implementation

[0058] The following specific examples illustrate the implementation of the present invention. The illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0059] This invention discloses a microwave photonic frequency synthesis system based on optoelectronic coordination. The following three embodiments illustrate this system:

[0060] Example 1

[0061] like Figure 1 As shown, a preferred embodiment of the optoelectronic synergistic microwave photonic frequency synthesis system of the present invention includes an optical frequency comb, an optical frequency doubling / division unit, a photoelectric conversion unit, a second electrical filtering unit, and a second electrical amplification unit. The optical frequency comb is connected to the optical frequency doubling / division unit via an optical path (such as an optical fiber), the optical frequency doubling / division unit is connected to the photoelectric conversion unit via an optical path, the photoelectric conversion unit is electrically connected to the second electrical filtering unit, and the second electrical filtering unit is electrically connected to the second electrical amplification unit.

[0062] The optical frequency comb is used to generate narrow optical pulse signals with high stability and low phase noise; for example, the optical frequency comb can output narrow optical pulse signals with a pulse width of 100 fs; of course, the pulse width can also be greater than or less than 100 fs. The optical frequency doubling / division unit is used to double or divide the repetition rate of the optical pulse signal output by the optical frequency comb, and can be a frequency converter constructed using fiber MZI (Mach-Zehnder interferometer), photonic crystal, etc. The photoelectric conversion unit is used to realize the photoelectric conversion of the optical pulse signal from the optical frequency doubling / division unit and output an electrical frequency comb. The second electrical filtering unit is a bandpass filter used to filter the electrical signal from the photoelectric conversion unit. The second electrical amplification unit is used to amplify the power of the electrical signal filtered by the second electrical filtering unit.

[0063] The working principle of this embodiment is as follows:

[0064] like Figure 1 As shown, this embodiment adopts a direct photoelectric conversion mode. During operation, the optical frequency comb generates a narrow optical pulse signal with high stability and low phase noise, and sends it to the optical frequency doubling / division unit. After the optical frequency doubling / division unit performs frequency doubling or division processing on the narrow optical pulse signal, the photoelectric conversion unit performs photoelectric conversion on the narrow optical pulse signal to generate an electrical frequency comb. Then, the second electrical filtering unit performs filtering processing on the electrical frequency comb. The signal of the required frequency is filtered out from the electrical frequency comb. Finally, the second electrical amplification unit amplifies the power of the filtered signal of the required frequency and outputs it.

[0065] The following explanation uses a microwave signal with a frequency of 9.6 GHz as an example:

[0066] First, an optical frequency comb generates a highly stable, low-phase-noise 200MHz narrow optical pulse signal with a high repetition rate. Then, an optical frequency doubling / division unit performs an 8x frequency multiplication on the narrow optical pulse signal, and a photoelectric conversion unit performs photoelectric conversion to generate an electrical frequency comb with 1.6GHz intervals. The second electrical filtering unit is set to a pass frequency of 9.6GHz, thereby filtering out a 9.6GHz frequency signal from the 1.6GHz interval electrical frequency comb. The second electrical amplification unit amplifies the filtered 9.6GHz frequency signal to obtain the desired frequency signal, which is then output to the user.

[0067] This embodiment uses an optical frequency comb as the frequency source. Since the operating frequency of an optical frequency comb is more than three orders of magnitude higher than that of a conventional microwave frequency source (e.g., a crystal oscillator), its performance is also more than three orders of magnitude higher. Therefore, the frequency synthesis system of this embodiment can generate frequencies with a wider frequency range and higher performance. Furthermore, this embodiment uses a direct photoelectric conversion mode to obtain the signal of the desired frequency, resulting in a simple structure. However, this embodiment can only filter the desired frequency from the optical frequency comb, and the frequency points generated are discrete, unable to generate continuously tuned frequency signals.

[0068] Example 2

[0069] like Figure 2 As shown, a preferred embodiment of the optoelectronic synergistic microwave photonic frequency synthesis system of the present invention includes an optical frequency comb, an optical frequency doubling / division unit, a photoelectric conversion unit, a first electrical filtering unit, an electrical frequency synthesis unit, an electrical routing unit, a second electrical filtering unit, and a second electrical amplification unit. The optical frequency comb is connected to the optical frequency doubling / division unit via an optical path. The optical frequency doubling / division unit is connected to the photoelectric conversion unit via an optical path. The photoelectric conversion unit is electrically connected to the second electrical filtering unit via the electrical routing unit. Specifically, the output terminal of the photoelectric conversion unit is electrically connected to the first input terminal of the electrical routing unit, the output terminal of the electrical routing unit is electrically connected to the input terminal of the second electrical filtering unit, and the output terminal of the second electrical filtering unit is electrically connected to the input terminal of the second electrical amplification unit. The output terminal of the photoelectric conversion unit is also electrically connected to the input terminal of the first electrical filtering unit, the output terminal of the first electrical filtering unit is electrically connected to the input terminal of the electrical frequency synthesis unit, and the output terminal of the electrical frequency synthesis unit is electrically connected to the second input terminal of the electrical routing unit.

[0070] The functions of the optical frequency comb, optical frequency multiplier / divider unit, photoelectric conversion unit, second electrical filter unit, and second electrical amplification unit are the same as in Embodiment 1. The first electrical filter unit is a bandpass filter used to select the frequency from the electrical frequency comb sent by the photoelectric conversion unit. The electrical frequency synthesis unit outputs a synthesized frequency signal based on the frequency reference signal or local oscillator signal input from the first electrical filter unit. The electrical frequency synthesis unit can use an electrical phase-locked loop (PLL) method to achieve frequency synthesis. The electrical routing unit is used to select the path of the electrical signal. It can select whether the photoelectric conversion unit is connected to the second electrical filter unit, or disconnected from the electrical frequency synthesis unit, or disconnected from the photoelectric conversion unit and connected to the second electrical filter unit, as needed. The second electrical filter unit is used to filter the frequency signal from the electrical routing unit.

[0071] The working principle of this embodiment is as follows:

[0072] like Figure 2 As shown, this embodiment has two operating modes. The first operating mode is the direct photoelectric conversion mode. In this mode, the electrical routing unit connects the photoelectric conversion unit to the second electrical filtering unit and disconnects the electrical frequency synthesis unit from the second electrical filtering unit. The working principle of the direct photoelectric conversion mode is the same as in Embodiment 1, and will not be described again here. The second operating mode is the electrical frequency synthesis mode. In this mode, the electrical routing unit disconnects the photoelectric conversion unit from the second electrical filtering unit and connects the electrical frequency synthesis unit to the second electrical filtering unit. The working process of the electrical frequency synthesis mode is as follows:

[0073] An optical frequency comb generates a narrow optical pulse signal with high stability and low phase noise, and sends it to an optical frequency doubling / division unit. After the optical frequency doubling / division unit performs frequency doubling or division processing on the narrow optical pulse signal, the photoelectric conversion unit performs photoelectric conversion on the narrow optical pulse signal to generate an electrical frequency comb. Because the electrical routing unit disconnects the photoelectric conversion unit from the second electrical filtering unit, the electrical frequency comb generated by the photoelectric conversion unit is sent to the first electrical filtering unit for filtering. The first electrical filtering unit filters out a specific frequency signal from the electrical frequency comb as a frequency reference signal or local oscillator signal, and sends it to the electrical frequency synthesis unit. The electrical frequency synthesis unit outputs a synthesized frequency signal based on the frequency reference signal or local oscillator signal input from the first electrical filtering unit. Because the electrical routing unit connects the electrical frequency synthesis unit to the second electrical filtering unit, the second electrical filtering unit filters out the desired frequency signal from the electrical frequency signal, and the second electrical amplification unit amplifies the power of the desired frequency signal filtered by the second electrical filtering unit before outputting it.

[0074] The following explanation uses a microwave signal with a frequency of 350MHz as an example:

[0075] First, an optical frequency comb generates a highly stable, low-phase-noise 200MHz narrow-repetition-rate optical pulse signal. Then, an optical frequency doubling / division unit divides the narrow-repetition-rate signal by 2, and a photoelectric conversion unit converts the narrow-repetition-rate signal to generate an electrical frequency comb with 100MHz intervals. The first electrical filtering unit has a pass frequency set to 100MHz, filtering out a 100MHz signal from the electrical frequency comb as a frequency reference signal or local oscillator signal, which is then sent to the electrical frequency synthesis unit. The electrical frequency synthesis unit uses an electrical phase-locked loop to generate the required 350MHz frequency signal based on the 100MHz signal, and sends it to the second electrical filtering unit via an electrical routing unit. The second electrical filtering unit has a pass frequency set to 350MHz, filtering out harmonics and other frequency signals. The second electrical amplification unit amplifies the filtered frequency signal to obtain the required 350MHz frequency signal, which is then output to the user.

[0076] In this embodiment, an optical frequency comb is used to provide a frequency reference signal or local oscillator signal to the electrical frequency synthesis unit. Since the operating frequency of the optical frequency comb is more than three orders of magnitude higher than that of a conventional microwave frequency source, its performance is also more than three orders of magnitude higher. Therefore, the frequency synthesis system of this embodiment can generate continuously tuned frequencies with higher performance. However, since the frequencies in this embodiment are synthesized by the electrical frequency synthesis unit using methods such as electrical phase-locked loop, it is more suitable for generating lower frequency signals.

[0077] Example 3

[0078] like Figure 3 As shown, a preferred embodiment of the optoelectronic synergistic microwave photonic frequency synthesis system of the present invention includes an optical frequency comb, an optical frequency doubling / division unit, a first optical routing unit, a second optical routing unit, an optical splitting unit, an optical combining unit, an optical frequency shifting unit, a first electrical amplification unit, an optoelectronic conversion unit, a first electrical filtering unit, an electrical frequency synthesis unit, an electrical routing unit, a second electrical filtering unit, and a second electrical amplification unit.

[0079] The optical frequency comb is connected to the optical frequency doubling / division unit via an optical path. The optical frequency doubling / division unit is connected to the photoelectric conversion unit via a first optical routing unit and a second optical routing unit. The output end of the optical frequency doubling / division unit is connected to the input end of the first optical routing unit via an optical path. The first output end of the first optical routing unit is connected to the first input end of the second optical routing unit via an optical path. The output end of the second optical routing unit is connected to the photoelectric conversion unit via an optical path.

[0080] The second output of the first optical routing unit is connected to the input of the optical splitter unit via an optical path. The first output of the optical splitter unit is connected to the first input of the optical combiner unit via an optical path. The optical splitter unit and the optical combiner unit form an MZI structure. The second output of the optical splitter unit is connected to the optical input of the optical frequency shifter unit via an optical path. The output of the optical frequency shifter unit is connected to the second input of the optical combiner unit via an optical path. The output of the optical combiner unit is connected to the second input of the second optical routing unit via an optical path.

[0081] The output terminal of the photoelectric conversion unit is electrically connected to the first input terminal of the electrical routing unit. The output terminal of the photoelectric conversion unit is also electrically connected to the first electrical filtering unit. The first electrical filtering unit is electrically connected to the electrical frequency synthesis unit. The output terminal of the electrical frequency synthesis unit is electrically connected to the input terminal of the first electrical amplification unit. The output terminal of the first electrical amplification unit is electrically connected to the electrical input terminal of the optical frequency shifting unit. The output terminal of the electrical frequency synthesis unit is also electrically connected to the second input terminal of the electrical routing unit. The output terminal of the electrical routing unit is electrically connected to the input terminal of the second electrical filtering unit, and the output terminal of the second electrical filtering unit is electrically connected to the input terminal of the second electrical amplification unit.

[0082] The functions of the optical frequency comb, optical frequency multiplication / division unit, photoelectric conversion unit, first electrical filtering unit, electrical frequency synthesis unit, electrical routing unit, second electrical filtering unit, and second electrical amplification unit are the same as in Embodiment 2. The first optical routing unit is used for path selection during optical splitting, and the second optical routing unit is used for path selection during optical combining. The optical splitting unit splits the optical pulse signal output from the second output terminal of the first optical routing unit into two outputs. The optical combining unit combines the optical pulses from the optical splitting unit and the optical frequency shifting unit into one output. The optical frequency shifting unit performs up or down frequency shifting on the optical pulse signal from the optical splitting unit based on the electrical frequency signal from the first electrical amplification unit. The first electrical amplification unit amplifies the electrical signal output from the electrical frequency synthesis unit before sending it to the optical frequency shifting unit.

[0083] The working principle of this embodiment is as follows:

[0084] like Figure 3As shown, this embodiment has three working modes. When the input terminal of the first optical routing unit is connected to its first output terminal and the output terminal of the second optical routing unit is connected to its first input terminal, the optical frequency multiplication / division unit is directly connected to the photoelectric conversion unit through the first optical routing unit and the second optical routing unit. The working principle at this time is the same as that in embodiment 2, that is, according to the two connection methods of the electrical routing unit, there are two working modes: direct photoelectric conversion mode and electrical frequency synthesis mode, which will not be described in detail here.

[0085] When the input terminal of the first optical routing unit is connected to its second output terminal, and the output terminal of the second optical routing unit is connected to its second input terminal, the electrical routing unit also connects the photoelectric conversion unit to the second electrical filtering unit and disconnects the electrical frequency synthesis unit from the second electrical filtering unit. At this time, this embodiment is in optical frequency shifting mode, and the working process of optical frequency shifting mode is as follows:

[0086] The optical frequency comb generates a narrow optical pulse signal with high stability and low phase noise, and sends it to the optical frequency doubling / division unit. After the optical frequency doubling / division unit performs frequency doubling or division processing on the narrow optical pulse signal, it is sent to the optical splitting unit via the first optical routing unit and split into two outputs: one output to the optical combining unit and the other output to the optical frequency shifting unit. The optical frequency shifting unit performs up or down frequency shift processing on the optical pulse signal sent from the optical splitting unit according to the electrical frequency signal input from the first electrical amplification unit, and also sends it to the optical combining unit. The optical combining unit combines the optical pulses sent from the optical splitting unit and the optical frequency shifting unit into one, and sends it to the photoelectric conversion unit via the second optical routing unit for photoelectric conversion to generate the electrical frequency comb.

[0087] In optical frequency shift mode, the electrical routing unit connects the photoelectric conversion unit and the second electrical filtering unit. Therefore, the electrical frequency comb generated by the photoelectric conversion unit is sent to both the second and first electrical filtering units. One path passes through the second electrical filtering unit, filtering out the desired frequency signal from the electrical frequency comb. This signal is then amplified by the second electrical amplification unit before being output. The other path passes through the first electrical filtering unit, filtering out a specific frequency signal from the electrical frequency comb as a frequency reference signal or local oscillator signal. This signal is then sent to the electrical frequency synthesis unit, which outputs a synthesized frequency signal based on the input frequency reference signal or local oscillator signal from the first electrical filtering unit. In optical frequency shift mode, the electrical routing unit disconnects the electrical frequency synthesis unit from the second electrical filtering unit. Therefore, the synthesized frequency signal output by the electrical frequency synthesis unit is first amplified by the first electrical amplification unit and then sent to the optical frequency shift unit as a drive signal for up or down frequency shifting.

[0088] The following explanation uses a microwave signal with a frequency of 32.3 GHz as an example:

[0089] First, an optical frequency comb generates a 200MHz narrow optical pulse signal with high stability and low phase noise. Then, an optical frequency multiplication / division unit performs an 8x frequency multiplication on the narrow optical pulse signal. An optical splitting unit and an optical combining unit form an MZI structure. The frequency-multiplication processed optical pulse signal is split into two paths. One path is shifted upwards by 300MHz by an optical frequency shifting unit. This path is then combined with the other unshifted signal in an optical combining unit. The narrow optical pulse signal is then converted into an electrical frequency comb by a photoelectric conversion unit. This electrical frequency comb is split into two paths. One path is sent to a first electrical filtering unit, whose pass frequency is set to 1.6GHz. This filters out a 1.6GHz signal, which serves as a frequency reference signal or local oscillator signal and is sent to an electrical frequency synthesis unit. The electrical frequency synthesis unit outputs a 300MHz synthesized frequency signal based on the 1.6GHz signal. This 300MHz synthesized frequency signal is amplified by a first electrical amplification unit and then sent to the optical frequency shifting unit as a drive signal for upward frequency shifting. Another electrical frequency comb is sent to the second electrical filter unit, which is set to pass frequency of 32.3 GHz, thereby filtering out the 32.3 GHz frequency signal from the electrical frequency comb; the second electrical amplifier unit amplifies the filtered 32.3 GHz frequency signal to obtain the required frequency signal and output it to the user.

[0090] This embodiment uses an optical frequency comb as a frequency source and provides a frequency reference signal or local oscillator signal to the electrical frequency synthesis unit. Since the optical frequency comb operates at a frequency more than three orders of magnitude higher than that of a conventional microwave source, its performance is also more than three orders of magnitude higher. Therefore, the frequency synthesis system of this embodiment can generate frequency signals with a wider frequency range and higher performance. Furthermore, this embodiment can switch between three operating modes as needed: direct photoelectric conversion mode, electrical frequency synthesis mode, and optical frequency shifting mode. It can also shift the frequency of the narrow optical pulse signal generated by the optical frequency comb, thereby obtaining an ultra-wideband continuously tuned frequency signal.

[0091] This invention also discloses a method for generating microwave photon frequencies based on optoelectronic coordination. A preferred embodiment of this method includes the following steps:

[0092] S1. After multiplying or dividing the narrow optical pulse signal generated by the optical frequency comb, can the desired signal frequency be obtained through photoelectric conversion? If yes, proceed to step S2; otherwise, proceed to step S3. For example, assuming the optical frequency comb generates a 200MHz repetition rate narrow optical pulse signal, to generate a 9.6GHz signal, since the 200MHz repetition rate narrow optical pulse signal generated by the optical frequency comb can be multiplied by 8 and then photoelectric converted to obtain an electrical frequency comb with a 1.6GHz interval, this electrical frequency comb includes the 9.6GHz signal. Therefore, step S2 can be performed to generate the signal through direct photoelectric conversion. If a signal with a frequency of 350MHz or 32.3GHz is to be generated, the above frequencies cannot be generated through direct photoelectric conversion, and step S3 will be performed.

[0093] S2. Generate the desired signal using a direct photoelectric conversion method. This step may specifically include the following steps:

[0094] S101. A narrow optical pulse signal with high stability and low phase noise is generated by an optical frequency comb.

[0095] S102. Perform frequency multiplication or frequency division processing on the narrow optical pulse signal generated by the optical frequency comb according to the frequency of the signal to be generated.

[0096] S103. The narrow optical pulse signal after frequency doubling or frequency division is photoelectrically converted to generate an electrical frequency comb.

[0097] S104. Filter the signal of the desired frequency from the electrical frequency comb through electrical filtering.

[0098] S105. Amplify the power of the signal filtered in step S104 to obtain the signal of the desired frequency.

[0099] S3. Check if the frequency of the signal to be generated is lower than a predetermined frequency threshold. If it is lower than the predetermined frequency threshold, proceed to step S4; otherwise, proceed to step S5. For example, for a 350MHz signal, since its frequency is relatively low, step S4 can be performed to generate it using an electrical frequency synthesis method. However, for a 32.3GHz signal, since its frequency is high, step S5 needs to be performed to generate it using an optical frequency shifting method.

[0100] S4. Generate the desired signal using electrical frequency synthesis. This step may specifically include the following steps:

[0101] S201. A narrow optical pulse signal with high stability and low phase noise is generated by an optical frequency comb.

[0102] S202. Based on the frequency of the frequency reference signal or the local oscillator signal, the narrow optical pulse signal generated by the optical frequency comb is subjected to frequency doubling or frequency division processing.

[0103] S203. The narrow optical pulse signal after frequency doubling or frequency division is photoelectrically converted to generate an electrical frequency comb.

[0104] S204. Filter a signal of a specific frequency from an electrical frequency comb using electrical filtering to serve as a frequency reference signal or a local oscillator signal.

[0105] S205. Generate a synthesized frequency signal including the required frequency based on the input frequency reference signal or local oscillator signal.

[0106] S206. Filter the desired frequency signal from the synthesized frequency signal using electrical filtering.

[0107] S207. Amplify the power of the signal filtered in step S206 to obtain the signal of the desired frequency.

[0108] S5. Generate the desired signal using an optical frequency shifting method. This step may specifically include the following steps:

[0109] S301, generates a narrow optical pulse signal with high stability and low phase noise through an optical frequency comb.

[0110] S302. The frequency repetition rate of the narrow optical pulse signal generated by the optical frequency comb is multiplied or divided according to the frequency of the signal to be generated.

[0111] S303. The optical pulse signal after frequency doubling or frequency division is divided into two paths. The first optical pulse signal is optically shifted by the optical frequency shifting unit and then combined with the second optical pulse signal that has not been shifted into one path.

[0112] S304. The narrow optical pulse signal after frequency shifting is photoelectrically converted to generate an electrical frequency comb.

[0113] S305. The electrical frequency comb is divided into two paths. The first electrical frequency comb filters out a signal of a specific frequency through electrical filtering as a frequency reference signal or a local oscillator signal, and generates a synthesized frequency signal based on the frequency reference signal or the local oscillator signal. The synthesized frequency signal is then amplified by power and used as the frequency shifting drive signal of the optical frequency shifting unit to drive the optical frequency shifting unit. The second electrical frequency comb filters out a signal of the required frequency through electrical filtering.

[0114] S306. Amplify the power of the signal filtered in step S305 to obtain a signal of the desired frequency.

[0115] This embodiment uses an optical frequency comb as a frequency source and provides a frequency reference signal or local oscillator signal to the electrical frequency synthesis unit. Since the optical frequency comb operates at a frequency more than three orders of magnitude higher than that of a conventional microwave source, its performance is also more than three orders of magnitude higher. Therefore, the frequency synthesis system of this embodiment can generate frequencies with a wider frequency range and higher performance. It can also frequency-shift the narrow optical pulse signal generated by the optical frequency comb to obtain an ultra-wideband continuously tuned frequency signal.

[0116] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A microwave photonic frequency synthesis system based on optoelectronic synergy, characterized in that: include Optical frequency combs are used to generate narrow optical pulse signals with high stability and low phase noise. Optical frequency doubling / division unit is used to double or divide the repetition rate of the optical pulse signal output by the optical frequency comb. The photoelectric conversion unit is used to realize the photoelectric conversion of the input optical pulse signal and output an electrical frequency comb; The second electrical filtering unit is used to filter the input electrical signal; as well as The second electrical amplifier unit is used to amplify the power of the input electrical signal; The optical frequency comb is connected to the optical frequency doubling / division unit, the optical frequency doubling / division unit is connected to the photoelectric conversion unit, the photoelectric conversion unit is electrically connected to the second electrical filtering unit, and the second electrical filtering unit is electrically connected to the second electrical amplification unit. It also includes an electrical routing unit, which is used to select the path of electrical signals; the photoelectric conversion unit is electrically connected to the second electrical filtering unit through the electrical routing unit; It also includes a first electrical filtering unit and an electrical frequency synthesis unit. The first electrical filtering unit is used to select the frequency of the electrical frequency comb. The electrical frequency synthesis unit is used to output a synthesized frequency signal based on the frequency reference signal or local oscillator signal input to the first electrical filtering unit. The output terminal of the photoelectric conversion unit is electrically connected to the first input terminal of the electrical routing unit and the first electrical filtering unit, respectively. The first electrical filtering unit is electrically connected to the electrical frequency synthesis unit. The electrical frequency synthesis unit is electrically connected to the second input terminal of the electrical routing unit. The output terminal of the electrical routing unit is electrically connected to the second electrical filtering unit. The electrical signal includes the electrical frequency comb and the synthesized frequency signal.

2. The microwave photonic frequency synthesis system based on optoelectronic synergy according to claim 1, characterized in that: It also includes a first optical routing unit and a second optical routing unit. The first optical routing unit is used to select the path when performing optical splitting, and the second optical routing unit is used to select the path when performing optical combining. The optical frequency multiplication / division unit is connected to the photoelectric conversion unit through the first optical routing unit and the second optical routing unit. The output terminal of the optical frequency multiplication / division unit is connected to the input terminal of the first optical routing unit, the first output terminal of the first optical routing unit is connected to the first input terminal of the second optical routing unit, and the output terminal of the second optical routing unit is connected to the photoelectric conversion unit.

3. The microwave photonic frequency synthesis system based on optoelectronic synergy according to claim 2, characterized in that: It also includes an optical splitter unit, an optical combiner unit, an optical frequency shifter unit, and a first electrical amplifier unit; The optical splitting unit is used to split the optical pulse signal output from the second output terminal of the first optical routing unit into two paths, one of which is output to the optical combining unit and the other of which is output to the optical frequency shifting unit. The optical combining unit is used to combine the optical pulses sent from the optical splitting unit and the optical frequency shifting unit into one path and then send it to the second input terminal of the second optical routing unit. The optical frequency shifting unit is used to perform up or down frequency shifting processing on the optical pulse signal sent by the optical splitting unit according to the electrical frequency signal sent by the first electrical amplification unit; The first electrical amplification unit is electrically connected to the electrical frequency synthesis unit and is used to amplify the electrical signal output by the electrical frequency synthesis unit before sending it to the optical frequency shifting unit.

4. A microwave photon frequency generation method based on optoelectronic coordination, characterized in that: The microwave photonic frequency synthesis system based on optoelectronic coordination according to any one of claims 1 to 3 includes the following steps: S1. After multiplying or dividing the narrow optical pulse signal generated by the optical frequency comb, can the frequency of the desired signal be obtained through photoelectric conversion? If so, proceed to step S2. Otherwise, proceed to step S3; S2. The required signal is generated using a direct photoelectric conversion method; S3. Is the frequency of the signal to be generated lower than the predetermined frequency threshold? If it is lower than the predetermined frequency threshold, then proceed to step S4. Otherwise, proceed to step S5; S4. The required signal is generated using an electrical frequency synthesis method; S5. The required signal is generated using an optical frequency shifting method.

5. The microwave photon frequency generation method based on optoelectronic coordination according to claim 4, characterized in that: Generating the desired signal using direct photoelectric conversion involves the following steps: S101. A narrow optical pulse signal with high stability and low phase noise is generated by an optical frequency comb; S102. Perform frequency doubling or frequency division processing on the repetition frequency of the narrow optical pulse signal; S103. Photoelectric conversion of narrow optical pulse signals to generate an electrical frequency comb; S104. Filter the signal of the desired frequency from the electrical frequency comb by electrical filtering; S105. Amplify the power of the filtered signal of the desired frequency.

6. The microwave photon frequency generation method based on optoelectronic coordination according to claim 4, characterized in that: The method of generating the desired signal using electrical frequency synthesis includes the following steps: S201. A narrow optical pulse signal with high stability and low phase noise is generated by an optical frequency comb; S202. Perform frequency doubling or frequency division processing on the repetition frequency of the narrow optical pulse signal; S203. Photoelectric conversion of narrow optical pulse signals to generate an electrical frequency comb; S204. Filter out a signal of a specific frequency from the electrical frequency comb through electrical filtering and use it as a frequency reference signal or local oscillator signal; S205. Generate a synthesized frequency signal including the desired frequency by using the input frequency reference signal or local oscillator signal; S206. Filter the desired frequency signal from the synthesized frequency signal using electrical filtering; S207. Amplify the power of the filtered signal of the desired frequency.

7. The microwave photon frequency generation method based on optoelectronic coordination according to claim 4, characterized in that: Generating the desired signal using optical frequency shifting involves the following steps: S301, A narrow optical pulse signal with high stability and low phase noise is generated by an optical frequency comb; S302. Perform frequency doubling or frequency division processing on the repetition rate of narrow optical pulse signals; S303. The optical pulse signal after frequency doubling or frequency division is divided into two paths. The first optical pulse signal is optically shifted by the optical frequency shifting unit and then combined with the second optical pulse signal that has not been shifted into one path. S304. The narrow optical pulse signal after frequency shifting is photoelectrically converted to generate an electrical frequency comb. S305. The electrical frequency comb is divided into two paths. The first electrical frequency comb filters out a signal of a specific frequency through electrical filtering as a frequency reference signal or local oscillator signal, and generates a synthesized frequency signal accordingly. The synthesized frequency signal is then amplified to drive the optical frequency shift unit. The second electrical frequency comb filters out the signal of the required frequency through electrical filtering. S306. Amplify the power of the filtered signal of the desired frequency.

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