A microwave photonic filtering method and apparatus

Abstract

This invention discloses a microwave photonic filtering method. The method includes: splitting an optical frequency comb into two paths; performing dispersion compensation on the first optical frequency comb and then splitting it into two local oscillator optical frequency comb signals; using the radio frequency signal to be filtered to perform carrier-suppressed single-sideband modulation on the second optical frequency comb, and performing the same dispersion compensation on the generated modulated optical signal before splitting it into two radio frequency modulated optical frequency comb signals; performing a 90° optical phase shift on one of the local oscillator optical frequency comb signals / radio frequency modulated optical frequency comb signals and coupling it with the other radio frequency modulated optical frequency comb signal / local oscillator optical frequency comb signal, and performing photoelectric detection on the coupled signal to obtain a first electrical signal; coupling the other local oscillator optical frequency comb signal with the other radio frequency modulated optical frequency comb signal and performing photoelectric detection to obtain a second electrical signal; and performing an electrical phase shift on the first electrical signal and then coupling it with the second electrical signal. This invention also discloses a microwave photonic filtering device. Compared with the prior art, this invention can significantly expand the frequency tunable range.

Description

Technical Field

[0001] This invention relates to a microwave photonic filtering method, belonging to the field of microwave photonics technology. Background Technology

[0002] In designing future mobile communication systems, multi-band communication technology has seen significant development due to the increasing demand for multi-band capabilities across various fields, including mobile communications, satellite communications, radar, embedded systems, and heterogeneous wireless networks. The challenge of multi-band communication lies in the generation, connection, and aggregation of discontinuous multi-channels at flexible frequencies, necessitating microwave filters capable of adjusting the center frequency and programming the bandwidth of each passband to a high-frequency range. Tunable and programmable microwave filters can not only select appropriate channels, suppress interleaved channels, mitigate interference signals, and adapt to environmental changes, but also aggregate signals in multi-band links. Against this backdrop, research on wideband, high-frequency, interference-resistant, and tunable multi-band filters helps meet the urgent needs of various wireless communication systems. Traditional electrical filters, based on electronic circuit principles, utilize electronic components such as capacitors, inductors, and resistors to filter and attenuate signals in specific frequency bands. However, with the continuous development of mobile communication technology, traditional methods are facing technological bottlenecks. Microwave photonic filters, due to their large operating bandwidth, low loss, rapid programmability, tunability, and insensitivity to electromagnetic interference, have been studied to improve microwave signal processing capabilities.

[0003] There are many schemes for realizing tunable microwave photonic filters, and optical frequency combs can provide a large number of taps and flexible tap coefficients. Therefore, microwave photonic filter schemes based on optical frequency comb structures have become a potential solution for reconfigurable microwave photonic filters and have attracted widespread attention from researchers. Microwave photonic filters based on optical frequency combs provide multiple taps through the optical frequency comb, and the time delay between these taps is correspondingly controlled by combining a broadband dispersive medium. By adjusting the amplitude and phase information of each tooth of the optical frequency comb, the response of the microwave photonic filter can be completely reconfigured. In existing microwave photonic filter schemes based on optical frequency comb structures, to avoid spectral aliasing, the frequency tuning range of the filter is usually set at half of the free spectrum range of the optical frequency comb, which greatly limits the frequency tuning range of this type of filter. Therefore, it is necessary to study how to effectively extend the frequency tuning range of microwave photonic filter schemes based on optical frequency comb structures. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of existing microwave photonic filtering schemes based on optical frequency combs, and to provide a microwave photonic filtering method and device that can significantly expand the frequency tunable range.

[0005] The present invention specifically adopts the following technical solutions to solve the above-mentioned technical problems:

[0006] A microwave photonic filtering method includes the following steps:

[0007] Optical frequency combs with the same initial phase information for each comb tooth are divided into two paths;

[0008] After performing dispersion compensation on the first optical frequency comb, the beam is split to obtain two local oscillator optical frequency comb signals; the carrier-suppressed single-sideband modulation of the second optical frequency comb is performed using the radio frequency signal to be filtered, and the generated modulated optical signal is split after the same dispersion compensation to obtain two radio frequency modulated optical frequency comb signals.

[0009] One of the local oscillator optical frequency comb signals / RF modulation optical frequency comb signals is optically phase-shifted by 90° and then coupled with another RF modulation optical frequency comb signal / local oscillator optical frequency comb signal. The coupled signal is then photodetected to obtain the first electrical signal. The other local oscillator optical frequency comb signal is coupled with another RF modulation optical frequency comb signal and then photodetected to obtain the second electrical signal.

[0010] Electrical phase shifting is performed on the first electrical signal: if the carrier-suppressed single-sideband modulation is a carrier-suppressed single-sideband modulation retaining +1st order sidebands, and the local oscillator optical frequency comb signal is optically phase-shifted by 90° and then coupled with a radio frequency modulated optical frequency comb signal, then a 90° electrical phase shift is performed; if the carrier-suppressed single-sideband modulation is a carrier-suppressed single-sideband modulation retaining +1st order sidebands, and the radio frequency modulated optical frequency comb signal is optically phase-shifted by 90° and then coupled with a local oscillator optical frequency comb signal, then a 270° electrical phase shift is performed; if the carrier-suppressed single-sideband modulation is a carrier-suppressed single-sideband modulation retaining -1st order sidebands, and the local oscillator optical frequency comb signal is optically phase-shifted by 90° and then coupled with a radio frequency modulated optical frequency comb signal, then a 270° electrical phase shift is performed; if the carrier-suppressed single-sideband modulation is a carrier-suppressed single-sideband modulation retaining -1st order sidebands, and the radio frequency modulated optical frequency comb signal is optically phase-shifted by 90° and then coupled with a local oscillator optical frequency comb signal, then a 90° electrical phase shift is performed.

[0011] The first electrical signal after phase shifting is coupled with the second electrical signal to obtain the filtered radio frequency signal.

[0012] Furthermore, the microwave photonic filtering method further includes:

[0013] Independent amplitude and phase modulation are applied to each tooth in the first or second optical frequency comb to achieve tuning and reconstruction of the filter function.

[0014] More preferably, a programmable optical filter is used to independently control the amplitude and phase of each tooth in the first or second optical frequency comb.

[0015] Preferably, the carrier-suppressed single-sideband modulation is implemented using a dual parallel Mach-Zehnder modulator (DPMZM).

[0016] Preferably, the modulated optical signal is amplified before dispersion compensation is performed.

[0017] Based on the same inventive concept, the following technical solutions can also be obtained:

[0018] A microwave photonic filter device, comprising:

[0019] An optical frequency comb source is used to generate an optical frequency comb in which each comb tooth has the same initial phase information.

[0020] An optical beam splitter is used to split the optical frequency into two paths;

[0021] The local oscillator signal branch is used to split the first optical frequency comb after dispersion compensation to obtain two local oscillator optical frequency comb signals.

[0022] The radio frequency signal branch is used to perform carrier-suppressed single-sideband modulation on the second optical frequency comb with the radio frequency signal to be filtered, and to split the generated modulated optical signal after performing the same dispersion compensation to obtain two radio frequency modulated optical frequency comb signals.

[0023] The image frequency suppression and output module is used to couple one local oscillator optical frequency comb signal / RF modulation optical frequency comb signal after a 90° optical phase shift, and then couple it with another RF modulation optical frequency comb signal / local oscillator optical frequency comb signal, and perform photoelectric detection on the coupled signal to obtain a first electrical signal; to couple another local oscillator optical frequency comb signal with another RF modulation optical frequency comb signal and then perform photoelectric detection to obtain a second electrical signal; to perform an electrical phase shift on the first electrical signal: if the carrier suppression single-sideband modulation is a carrier suppression single-sideband modulation that retains +1 order sidebands and the local oscillator optical frequency comb signal is coupled with an RF modulation optical frequency comb signal after a 90° optical phase shift, then a 90° electrical phase shift is performed; if the carrier suppression single-sideband modulation is a carrier suppression single-sideband modulation that retains +1 order sidebands... If the carrier-suppressed single-sideband modulation is performed and the RF-modulated optical frequency comb signal is optically phase-shifted by 90° and then coupled with a local oscillator optical frequency comb signal, then a 270° electrical phase shift is performed; if the carrier-suppressed single-sideband modulation is performed with a -1st order sideband retained and the local oscillator optical frequency comb signal is optically phase-shifted by 90° and then coupled with a local oscillator optical frequency comb signal, then a 270° electrical phase shift is performed; if the carrier-suppressed single-sideband modulation is performed with a -1st order sideband retained and the RF-modulated optical frequency comb signal is optically phase-shifted by 90° and then coupled with a local oscillator optical frequency comb signal, then a 90° electrical phase shift is performed; the first electrical signal after electrical phase shift is coupled with the second electrical signal, and the filtered RF signal is output.

[0024] Furthermore, the microwave photonic filter device also includes:

[0025] The amplitude and phase control module is used to independently adjust the amplitude and phase of each tooth in the first or second optical frequency comb to achieve the tuning and reconstruction of the filter function.

[0026] More preferably, the amplitude and phase control module is a programmable optical filter.

[0027] Preferably, the carrier-suppressed single-sideband modulation is implemented using a dual parallel Mach-Zehnder modulator (DPMZM) in the radio frequency signal branch.

[0028] Preferably, the radio frequency signal branch further includes an optical amplifier for amplifying the modulated optical signal before performing dispersion compensation.

[0029] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0030] This invention breaks the limitation of existing microwave photonic filtering schemes based on optical frequency combs, which set the frequency tuning range of the filter at half of the free spectrum range of the optical frequency comb to avoid spectral aliasing, without changing the free spectrum range of the optical frequency comb. It significantly improves the frequency tuning range of the microwave photonic filter, reduces the requirement for a large free spectrum range optical frequency comb source in the microwave photonic filter structure, and also reduces the cost of the system. Attached Figure Description

[0031] Figure 1 This is a schematic diagram illustrating the structural principle of the microwave photonic filter of the present invention;

[0032] Figure 2 This is a schematic diagram of a specific embodiment of the microwave photonic filter of the present invention;

[0033] Figure 3 This is a schematic diagram of the internal structure of DPMZM;

[0034] Figure 4 The simulated frequency response diagram of the single-channel microwave photonic filter using the scheme of this invention is shown below.

[0035] Figure 5 The simulated frequency response diagram of the dual-channel microwave photonic filter using the scheme of this invention is shown. Detailed Implementation

[0036] To overcome the limitation of existing microwave photonic filtering schemes based on optical frequency combs, which set the frequency tuning range of the filter at half the free spectrum range of the optical frequency comb to avoid spectral aliasing, and to significantly improve the frequency tuning range of microwave photonic filters, the present invention proposes a solution based on a special image frequency suppression structure to eliminate spectral aliasing caused by image frequency spurious signals. This effectively improves the frequency tuning range of microwave photonic filters without changing the free spectrum range of the optical frequency comb.

[0037] The basic structure and principle of the microwave photonic filter proposed in this invention are as follows: Figure 1 As shown, it specifically includes:

[0038] An optical frequency comb source is used to generate an optical frequency comb in which each comb tooth has the same initial phase information.

[0039] An optical beam splitter is used to split the optical frequency into two paths;

[0040] The local oscillator signal branch is used to split the first optical frequency comb after dispersion compensation to obtain two local oscillator optical frequency comb signals.

[0041] The radio frequency signal branch is used to perform carrier-suppressed single-sideband modulation on the second optical frequency comb with the radio frequency signal to be filtered, and to split the generated modulated optical signal after performing the same dispersion compensation to obtain two radio frequency modulated optical frequency comb signals.

[0042] The image frequency suppression and output module is used to couple one local oscillator optical frequency comb signal / RF modulation optical frequency comb signal after a 90° optical phase shift, and then couple it with another RF modulation optical frequency comb signal / local oscillator optical frequency comb signal, and perform photoelectric detection on the coupled signal to obtain a first electrical signal; to couple another local oscillator optical frequency comb signal with another RF modulation optical frequency comb signal and then perform photoelectric detection to obtain a second electrical signal; to perform an electrical phase shift on the first electrical signal: if the carrier suppression single-sideband modulation is a carrier suppression single-sideband modulation that retains +1 order sidebands and the local oscillator optical frequency comb signal is coupled with an RF modulation optical frequency comb signal after a 90° optical phase shift, then a 90° electrical phase shift is performed; if the carrier suppression single-sideband modulation is a carrier suppression single-sideband modulation that retains +1 order sidebands... If the carrier-suppressed single-sideband modulation is performed and the RF modulation optical frequency comb signal is optically phase-shifted by 90° and then coupled with a local oscillator optical frequency comb signal, then a 270° electrical phase shift is performed; if the carrier-suppressed single-sideband modulation is performed with a -1st order sideband retained and the local oscillator optical frequency comb signal is optically phase-shifted by 90° and then coupled with a local oscillator optical frequency comb signal, then a 270° electrical phase shift is performed; if the carrier-suppressed single-sideband modulation is performed with a -1st order sideband retained and the RF modulation optical frequency comb signal is optically phase-shifted by 90° and then coupled with a local oscillator optical frequency comb signal, then a 90° electrical phase shift is performed; the first electrical signal after electrical phase shift is coupled with the second electrical signal, and the filtered RF signal is output.

[0043] To facilitate the tuning and reconstruction of the filter function, an amplitude and phase control module can be further configured in the local oscillator signal branch or the radio frequency signal branch to independently adjust the amplitude and phase of each tooth in the first or second optical frequency comb. The amplitude and phase control module can be a programmable optical filter.

[0044] The carrier-suppressed single-sideband modulation can be implemented using various existing methods, such as direct implementation with a dual parallel Mach-Zehnder modulator or indirect implementation with a Mach-Zehnder modulator (MZM) combined with a periodic optical filter; preferably, the carrier-suppressed single-sideband modulation is implemented using a dual parallel Mach-Zehnder modulator in the radio frequency signal branch.

[0045] It should be noted that in the technical solution of this invention, a 90° phase shift can be introduced into one of the two local oscillator optical frequency comb signals output from the local oscillator signal branch, or a 90° phase shift can be introduced into one of the two radio frequency modulated optical frequency comb signals output from the radio frequency signal branch. Correspondingly, the beat frequency signal of the coupled optical signal with the introduced 90° phase shift needs to undergo the electrical phase shift. The phase shift angle of the electrical phase shift needs to be determined based on the specific method of the carrier-suppressed single-sideband modulation and whether the 90° phase shift is introduced into the local oscillator optical frequency comb signal or the radio frequency modulated optical frequency comb signal. For example, if the carrier-suppressed single-sideband modulation is to retain the +1st order sideband... If the carrier-suppressed single-sideband modulation (CSSM) is performed and the local oscillator optical frequency comb signal is optically phase-shifted by 90° and then coupled with a radio frequency modulated optical frequency comb signal, then a 90° electrical phase shift is performed. If the carrier-suppressed single-sideband modulation is performed with a +1st-order sideband and the radio frequency modulated optical frequency comb signal is optically phase-shifted by 90° and then coupled with a local oscillator optical frequency comb signal, then a 270° electrical phase shift is performed. If the carrier-suppressed single-sideband modulation is performed with a -1st-order sideband and the local oscillator optical frequency comb signal is optically phase-shifted by 90° and then coupled with a radio frequency modulated optical frequency comb signal, then a 270° electrical phase shift is performed. If the carrier-suppressed single-sideband modulation is performed with a -1st-order sideband and the radio frequency modulated optical frequency comb signal is optically phase-shifted by 90° and then coupled with a local oscillator optical frequency comb signal, then a 90° electrical phase shift is performed.

[0046] To facilitate public understanding, the technical solution of the present invention will be described in detail below through a specific embodiment:

[0047] The structure of the microwave photonic filter device in this embodiment is as follows: Figure 2 As shown, it includes:

[0048] An optical frequency comb source is used to generate an optical frequency comb in which each comb tooth has the same initial phase.

[0049] Optical beam splitters 1-3 are used to split optical signals into two paths;

[0050] Programmable optical filters are used to control the amplitude and phase of each tooth of an optical frequency comb.

[0051] Dispersion compensation module 1; used to introduce a corresponding time delay into the optical frequency comb after passing through the programmable optical filter, thereby adjusting the free spectrum range of the microwave photonic filter accordingly.

[0052] A vector network analyzer is used to output a swept frequency signal within a frequency range as the radio frequency signal to be filtered, and to analyze the filtered radio frequency signal output by the system to obtain the frequency response curve of the microwave photonic filter.

[0053] The DPMZM is used to perform carrier-suppressed single-sideband modulation on the RF signal to be filtered output from a vector network analyzer; its internal structure is as follows: Figure 3 As shown, the internal components include an optical beamsplitter, two sub-Mach-Zehnder modulators (MZM1 and MZM2), a shared-arms Mach-Zehnder modulator (MZM3), and an optical beam combiner. The optical beamsplitter splits the input optical signal into two paths. MZM1 and MZM2 are both biased at their minimum bias points to modulate the RF signal output from the vector network analyzer onto each tooth of the optical frequency comb, achieving a suppressed-carrier double-sideband modulation signal. In this embodiment, a 270° phase shift is introduced into the modulated optical signal output from MZM2 by adjusting the DC bias voltage applied to MZM3. The optical beam combiner couples the upper and lower optical signals of the DPMZM into one, thereby eliminating the -1st-order sideband in the suppressed-carrier double-sideband modulation signal and retaining only the +1st-order sideband, thus achieving suppressed-carrier single-sideband modulation. Similarly, suppressed-carrier single-sideband modulation with only the -1st-order sideband can also be achieved.

[0054] An optical amplifier is used to amplify the optical power of a suppressed-carrier single-sideband modulated signal.

[0055] The dispersion compensation module 2 introduces a corresponding time delay to suppress the carrier single-sideband modulation signal, thereby adjusting the free spectrum range of the microwave photonic filter accordingly. It has the same dispersion value as the dispersion compensation module 1.

[0056] A 90° optical phase shifter is used to introduce a 90° phase shift into one of the two local oscillator optical frequency comb signals output from the local oscillator signal branch;

[0057] Optical beam combiner 1 couples the local oscillator optical frequency comb signal that has passed through the 90° optical phase shifter with one of the two RF modulated optical frequency comb signals output from the RF branch signal, to obtain a coupled signal with a 90° phase difference between the local oscillator optical frequency comb signal and the RF modulated optical frequency comb signal.

[0058] Optical beam combiner 2 couples another local oscillator optical frequency comb signal with another radio frequency modulated optical frequency comb signal to obtain a coupled signal with the same phase between the local oscillator optical frequency comb signal and the radio frequency modulated optical frequency comb signal;

[0059] Photodetector 1 is used to perform photoelectric conversion on the coupled signal output by optical beam combiner 1. The resulting electrical signal contains two radio frequency signal components a and b with a phase difference of 180° (corresponding to the local oscillator optical frequency comb signal in the coupled signal after passing through a 90° optical phase shifter, which are obtained by photoelectric conversion with the radio frequency modulated optical frequency comb signals of its +1st and -1st sidebands, respectively).

[0060] Photodetector 2 is used to perform photoelectric conversion on the coupled signal output by optical beam combiner 2. The resulting electrical signal contains two radio frequency signal components a' and b' with the same phase (obtained by photoelectric conversion of the other local oscillator optical frequency comb signal in the coupled signal with the radio frequency modulated optical frequency comb signals of its +1st and -1st order sidebands, respectively).

[0061] A 90° phase shifter is used to introduce a 90° phase shift into the radio frequency signal output by photodetector 1, so that the amplitude and phase of radio frequency signal components a and a' are the same, and the amplitudes of b and b' are the same but the phase difference is 180°.

[0062] An electrical combiner is used to couple two sets of radio frequency signal components a and a' and b and b' into one path, so that b and b' cancel each other out.

[0063] Assume the angular frequency of the optical frequency comb generated by the optical frequency comb source is w. n The amplitude is A n The phase is φ n Where n is the nth tooth of the optical frequency comb, the optical frequency comb generated by the optical frequency comb source can be expressed as:

[0064]

[0065] The optical frequency comb is split into upper and lower paths by an optical beam splitter. The upper path inputs the local oscillator signal branch, and the lower path inputs the radio frequency signal branch. In the local oscillator signal branch, the amplitude and phase of each tooth of the optical frequency comb are adjusted by controlling a programmable optical filter. The adjusted optical signal is then connected to the dispersion compensation module 1, introducing a corresponding time delay. The output optical signal of this branch can be expressed as:

[0066]

[0067] Among them, B n and ψ2 represents the amplitude and phase of the optical frequency comb added by the programmable optical filter, and ψ2 represents the dispersion value of the dispersion compensation module. The phase change of the optical signal caused by the introduction of time delay into the dispersion compensation module.

[0068] In the RF signal branch, the optical frequency comb modulates the RF signal output from the vector network analyzer onto each tooth of the optical frequency comb via the DPMZM. The DPMZM includes MZM1, MZM2, and an MZM3 sharing two arms. MZM1 and MZM2 are both biased at the minimum bias point. The output optical signals of MZM1, MZM3, and the DPMZM can be expressed as follows under small-signal modulation conditions:

[0069]

[0070] Among them, w RF Let ω be the angular frequency of the RF signal output by the vector network analyzer, and J1(γ) be a first-order Bessel function. The output optical signal after passing through dispersion compensation module 2 can be expressed as:

[0071]

[0072] The local oscillator optical frequency comb signal output from the local oscillator signal branch and the radio frequency modulated optical frequency comb signal output from the radio frequency signal branch are split into two paths by optical beamsplitter 2 and optical beamsplitter 3, respectively. One path of the local oscillator optical frequency comb signal is coupled to the radio frequency modulated optical frequency comb signal via a 90° optical phase shifter, while the other path of the local oscillator optical frequency comb signal is directly coupled to the radio frequency modulated optical frequency comb signal. These paths are then input to photodetector 1 and photodetector 2 for photoelectric conversion, respectively. Assume the radio frequency modulated optical frequency comb signal is A. n (t), the local oscillator optical frequency comb signal is B n (t), where n represents the nth comb tooth of the optical signal. Taking the nth comb tooth of the local oscillator optical frequency comb signal as an example, the electrical signal output after photoelectric detection of the local oscillator optical frequency comb signal and its +1st and -1st order sideband RF modulated optical frequency comb signals can be expressed as:

[0073]

[0074] Where I1(t) and I2(t) represent the electrical signals obtained by photoelectric conversion after the local oscillator optical frequency comb signal and the radio frequency modulated optical frequency comb signal are coupled through optical beam combiner 2 and input into photodetector 2, and I3(t) and I4(t) represent the electrical signals obtained by photoelectric conversion after the local oscillator optical frequency comb signal and the radio frequency modulated optical frequency comb signal are coupled through optical beam combiner 1 and input into photodetector 1, and B' n (t) represents the local oscillator frequency comb signal after passing through the 90° optical phase shifter. The electrical signal output from photodetector 1, after passing through the 90° electrical phase shifter, can be expressed as:

[0075]

[0076] Finally, the electrical signal output from the 90° phase shifter is coupled with the electrical signal output from the photodetector 2 through an electrical combiner. Comparing I1(t) and I2(t) and I5(t) and I6(t), in the two branches coupled by the electrical combiner, the amplitude and phase of the electrical signal obtained by photoelectric conversion of the nth comb tooth of the local oscillator optical frequency comb signal and the nth comb tooth of the radio frequency modulated optical frequency comb signal are equal, while the amplitude and phase of the electrical signal obtained by photoelectric conversion of the nth comb tooth of the local oscillator optical frequency comb signal and the (n-1)th comb tooth of the radio frequency modulated optical frequency comb signal are equal and opposite, so they are canceled out, thereby eliminating the spectral aliasing caused by the image frequency spurious signal and improving the frequency tuning range of the microwave photonic filter.

[0077] Figure 4 The simulation frequency response diagram of the single-channel microwave photonic filter of the above device is shown. The device structure was built using Optisystem simulation software. A 0-40GHz sweep frequency signal was generated by the electrical filter analyzer in the simulation software and input into the DPMZM. The comb tooth spacing of the optical frequency comb was set to 40GHz. The three curves in the figure are the frequency response curves of the microwave photonic filter with center frequencies of 18GHz, 24GHz and 30GHz, respectively. It can be seen that the microwave photonic filter still maintains good tunability in the frequency range of 20GHz-40GHz and is not affected by image frequency spurious signals.

[0078] Figure 5 The simulated frequency response diagram of the dual-channel microwave photonic filter of the above-mentioned device is shown. The device structure was systematically built using Optisystem simulation software. A 0-40GHz swept frequency signal was generated by the electrical filter analyzer in the simulation software and input into the DPMZM. At the same time, two clusters of optical frequency combs with different center frequencies were constructed. The comb tooth spacing of the optical frequency combs was set to 40GHz to generate a dual-channel microwave photonic filter. The three curves in the figure are the frequency response curves of the microwave photonic filter with center frequencies of 12GHz and 26GHz, 12GHz and 29GHz, and 12GHz and 32GHz. It can be seen that under the condition of introducing dual channels, the center frequency of the microwave photonic filter still maintains good tunability in the frequency range of 20GHz-40GHz and is not affected by image frequency spurious signals.

Claims

1. A microwave photonic filtering method, characterized in that, Includes the following steps: Optical frequency combs with the same initial phase information for each comb tooth are divided into two paths; After performing dispersion compensation on the first optical frequency comb, the beam is split to obtain two local oscillator optical frequency comb signals; The second optical frequency comb is modulated with carrier-suppressed single-sideband modulation using the radio frequency signal to be filtered, and the generated modulated optical signal is split after the same dispersion compensation to obtain two radio frequency modulated optical frequency comb signals. One of the local oscillator optical frequency comb signals / RF modulated optical frequency comb signals is optically phase-shifted by 90° and then coupled with another RF modulated optical frequency comb signal / local oscillator optical frequency comb signal. The coupled signal is then photoelectrically detected to obtain the first electrical signal. After coupling another local oscillator optical frequency comb signal with another radio frequency modulated optical frequency comb signal, photoelectric detection is performed to obtain a second electrical signal; Electrical phase shifting is performed on the first electrical signal: if the carrier-suppressed single-sideband modulation is a carrier-suppressed single-sideband modulation retaining +1st order sidebands, and the local oscillator optical frequency comb signal is optically phase-shifted by 90° and then coupled with a radio frequency modulated optical frequency comb signal, then a 90° electrical phase shift is performed; if the carrier-suppressed single-sideband modulation is a carrier-suppressed single-sideband modulation retaining +1st order sidebands, and the radio frequency modulated optical frequency comb signal is optically phase-shifted by 90° and then coupled with a local oscillator optical frequency comb signal, then a 270° electrical phase shift is performed; if the carrier-suppressed single-sideband modulation is a carrier-suppressed single-sideband modulation retaining -1st order sidebands, and the local oscillator optical frequency comb signal is optically phase-shifted by 90° and then coupled with a radio frequency modulated optical frequency comb signal, then a 270° electrical phase shift is performed; if the carrier-suppressed single-sideband modulation is a carrier-suppressed single-sideband modulation retaining -1st order sidebands, and the radio frequency modulated optical frequency comb signal is optically phase-shifted by 90° and then coupled with a local oscillator optical frequency comb signal, then a 90° electrical phase shift is performed. The first electrical signal after phase shifting is coupled with the second electrical signal to obtain the filtered radio frequency signal; Independent amplitude and phase modulation are applied to each tooth in the first or second optical frequency comb to achieve tuning and reconstruction of the filter function.

2. The microwave photonic filtering method as described in claim 1, characterized in that, The amplitude and phase of each tooth in the first or second optical frequency comb are independently controlled using a programmable optical filter.

3. The microwave photonic filtering method as described in claim 1, characterized in that, The carrier-suppressed single-sideband modulation is achieved using a dual parallel Mach-Zehnder modulator.

4. The microwave photonic filtering method as described in claim 1, characterized in that, The modulated optical signal is amplified and then dispersion compensation is performed.

5. A microwave photonic filter device, characterized in that, include: An optical frequency comb source is used to generate an optical frequency comb in which each comb tooth has the same initial phase information. An optical beam splitter is used to split the optical frequency into two paths; The local oscillator signal branch is used to split the first optical frequency comb after dispersion compensation to obtain two local oscillator optical frequency comb signals. The radio frequency signal branch is used to perform carrier-suppressed single-sideband modulation on the second optical frequency comb with the radio frequency signal to be filtered, and to split the generated modulated optical signal after performing the same dispersion compensation to obtain two radio frequency modulated optical frequency comb signals. The image frequency suppression and output module is used to couple one of the local oscillator optical frequency comb signals / RF modulation optical frequency comb signals after 90° optical phase shift with one of the RF modulation optical frequency comb signals / local oscillator optical frequency comb signals, and to perform photoelectric detection on the coupled signal to obtain the first electrical signal; After coupling another local oscillator optical frequency comb signal with another radio frequency modulated optical frequency comb signal, photoelectric detection is performed to obtain a second electrical signal. The first electrical signal is then electrically phase-shifted: if the carrier-suppressed single-sideband modulation is changed to carrier-suppressed single-sideband modulation retaining +1st order sidebands, and the local oscillator optical frequency comb signal is optically phase-shifted by 90° and then coupled with one radio frequency modulated optical frequency comb signal, then a 90° electrical phase shift is performed; if the carrier-suppressed single-sideband modulation is changed to carrier-suppressed single-sideband modulation retaining +1st order sidebands, and the radio frequency modulated optical frequency comb signal is optically phase-shifted by 90° and then coupled with one local oscillator optical frequency comb signal... If the carrier-suppressed single-sideband modulation is a carrier-suppressed single-sideband modulation that retains the -1st order sideband and the local oscillator optical frequency comb signal is optically phase-shifted by 90° and then coupled with one RF modulation optical frequency comb signal, then a 270° electrical phase shift is performed; if the carrier-suppressed single-sideband modulation is a carrier-suppressed single-sideband modulation that retains the -1st order sideband and the RF modulation optical frequency comb signal is optically phase-shifted by 90° and then coupled with one local oscillator optical frequency comb signal, then a 90° electrical phase shift is performed; the first electrical signal after electrical phase shift is coupled with the second electrical signal, and the filtered RF signal is output; The amplitude and phase control module is used to independently adjust the amplitude and phase of each tooth in the first or second optical frequency comb to achieve the tuning and reconstruction of the filter function.

6. The microwave photonic filtering device as described in claim 5, characterized in that, The amplitude and phase control module is a programmable optical filter.

7. The microwave photonic filtering device as described in claim 5, characterized in that, The carrier-suppressed single-sideband modulation is achieved using a dual parallel Mach-Zehnder modulator in the radio frequency signal branch.

8. The microwave photonic filtering device as described in claim 5, characterized in that, The radio frequency signal branch also includes an optical amplifier, which amplifies the modulated optical signal before performing dispersion compensation.

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