CN114124231B - Parallel multi-band multi-lattice microwave signal generator - Google Patents
Parallel multi-band multi-lattice microwave signal generator Download PDFInfo
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- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
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- H04L25/40—Transmitting circuits; Receiving circuits
- H04L25/49—Transmitting circuits; Receiving circuits using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels ; Baseband coding techniques specific to data transmission systems
- H04L25/4917—Transmitting circuits; Receiving circuits using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels ; Baseband coding techniques specific to data transmission systems using multilevel codes
- H04L25/4919—Transmitting circuits; Receiving circuits using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels ; Baseband coding techniques specific to data transmission systems using multilevel codes using balanced multilevel codes
- H04L25/4921—Transmitting circuits; Receiving circuits using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels ; Baseband coding techniques specific to data transmission systems using multilevel codes using balanced multilevel codes using quadrature encoding, e.g. carrierless amplitude-phase coding
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Abstract
The invention discloses a parallel multi-band multi-lattice microwave signal generating device, which comprises: the laser is used for emitting optical signals; the microwave source is used for adjusting the power of the microwave signal input into the parallel modulation module and sending out a microwave signal; the first voltage source is used for inputting a direct current bias voltage; the second voltage source is used for inputting a direct current bias voltage; an arbitrary waveform generator for emitting a baseband signal including a baseband chirp signal and a baseband coding control signal; the parallel modulation module is used for generating mutually orthogonal optical frequency comb signals and optical signals loaded with baseband signals; and the detection module is used for carrying out differential detection on the optical signals so as to obtain multi-band double-chirp signals or multi-band phase coded signals after photoelectric conversion. The parallel coding and microwave signals can be realized, the wavelength crosstalk problem caused by a serial structure is avoided, a mode-locked laser or a laser plus an additional modulator is not required to be used as a light source, the structure is simple, the cost is low, and the integration is easy.
Description
Technical Field
The invention relates to the fields of microwave photonics and radars, in particular to a parallel multi-band multi-lattice type microwave signal generating device.
Background
With the continuous development of modern radar technology, radar systems evolve from a single frequency band to multiple frequency bands and multifunctional directions. The double chirp signal and the phase coding signal have good pulse compression characteristics, and can be widely applied to signal sources of remote early warning radar and high-resolution radar systems. Typically the double chirp signal and the phase encoded signal can be achieved by conventional electronic methods and photonic microwave signal generation techniques. However, conventional electronics methods produce microwave signals with limited bandwidth due to limitations in the electronics bottlenecks. Microwave photonics has the advantages of large bandwidth, low loss and strong anti-interference performance, and is widely used for generating chirp signals and phase coding signals in recent years. The existing multiband chirp signal or phase coding signal based on microwave photonics is mainly generated by taking a mode-locked laser as a light source, inputting the mode-locked laser into a polarization modulator loading a baseband signal (such as a coding control signal or a baseband linear frequency modulation signal) to form a serial structure, outputting two paths of signals with orthogonal polarization through a polarization beam splitter by adjusting the polarization angle of the optical signal, and injecting the signals into a balanced photoelectric detector for photoelectric conversion. Or the modulation characteristic of the electro-optic modulator is utilized to generate an optical frequency comb to replace a mode locking laser as an input light source, and the optical frequency comb and the electro-optic modulator loaded with the baseband signals form a serial structure, so that multi-band signal generation is realized. The existing series structure needs a multi-wavelength light source, the cost is high, and the optical power loss of the system is high.
Disclosure of Invention
First, the technical problem to be solved
The invention discloses a parallel multi-band multi-lattice microwave signal generating device, which at least solves the problems of the prior art.
(II) technical scheme
To achieve the above object, the present invention provides a parallel multi-band multi-lattice microwave signal generating apparatus, comprising: the laser is used for emitting optical signals; the output end of the laser is connected with the first input end of the parallel modulation module; the output end of the microwave source is connected with the second input end of the parallel modulation module and is used for adjusting the power of the microwave signal input into the parallel modulation module and sending out the microwave signal; the output end of the arbitrary waveform generator is connected with the third input end of the parallel modulation module; for emitting a baseband signal comprising a baseband chirp signal and a baseband coding control signal; the first voltage source is used for inputting a direct-current bias voltage to the parallel modulation module; the second voltage source is used for inputting a direct-current bias voltage to the parallel modulation module; and the detection module is used for differentially detecting the signals input by the parallel modulation module and outputting multi-band double-chirp signals or multi-band phase coded signals.
The parallel modulation module modulates the optical signals input by the laser, the microwave signals input by the microwave source and the baseband signals input by the arbitrary waveform generator to generate mutually orthogonal optical frequency comb signals and optical signals loaded with the baseband signals, and synthesizes one path of modulated signals to be input to the detection module.
The parallel modulation module comprises a first electro-optical modulator, a second electro-optical modulator, a 90-degree polarization rotator and a polarization beam combiner; the first electro-optical modulator forms a first serial branch of the parallel modulation module, the output end of the second electro-optical modulator is connected with the input end of the 90-degree polarization rotator to form a second serial branch of the parallel modulation module, the first serial branch and the second serial branch are connected in parallel to the input end of the polarization beam combiner, and the polarization beam combiner is used for combining optical signals generated by the first serial branch and the second serial branch into one path.
The detection module comprises a polarization controller, a polarization beam splitter and a balanced photoelectric detector; the polarization beam combiner, the polarization controller, the polarization beam splitter and the balance photoelectric detector are connected in sequence; the two output ends of the polarization beam splitter are respectively connected with the two input ends of the balance photoelectric detector; the polarization controller rotates one path of signal sent by the polarization beam combiner by 45 degrees relative to the original main axis direction, and the one path of signal is divided into two paths of signals under the action of the polarization beam splitter and is input to the balance photoelectric detector.
Optionally, the first electro-optical modulator generates and outputs at least five optical frequency comb signals by adjusting the microwave signal power of the microwave source and the direct current bias voltage of the first voltage source.
Optionally, the polarization state of the optical signal output by the second electro-optical modulator is perpendicular to the polarization state of the optical frequency comb signal output by the first electro-optical modulator by adjusting the 90-degree polarization rotator.
The balance photoelectric detector carries out differential detection on two paths of input signals, so that the two paths of signals are subjected to beat frequency and then subtracted to generate multiband and multi-format microwave signal output.
The first electro-optical modulator and the second electro-optical modulator are one or more of a commercial lithium niobate modulator, a silicon-based integrated modulator, a dual-polarization dual-parallel Mach-Zehnder modulator, a dual-polarization dual-drive Mach-Zehnder modulator and a dual-polarization Mach-Zehnder modulator.
Optionally, the first electro-optic modulator is formed by connecting a first mach-zehnder modulator with a second mach-zehnder modulator in parallel; the second electro-optic modulator is formed by connecting a first Mach-Zehnder modulator and a second Mach-Zehnder modulator in parallel.
Optionally, the first electro-optic modulator is a first dual drive mach-zehnder modulator, and the second electro-optic modulator is a second dual drive mach-zehnder modulator.
Optionally, the first electro-optic modulator is a first mach-zehnder modulator, and the second electro-optic modulator is a second mach-zehnder modulator.
The parallel multi-band multi-format microwave signal generation method comprises the following steps: the first electro-optical modulator in the parallel modulation module generates at least 5 optical frequency comb signals by adjusting direct current bias voltage, microwave signal input power and phase difference input by the first voltage source; while a second electro-optic modulator in the parallel modulation module generates an optical signal loaded with the baseband signal. The 90-degree polarization rotator is used for orthogonally polarizing the optical frequency comb signal and the optical signal loaded with the baseband signal, and combining the optical frequency comb signal and the optical signal loaded with the baseband signal through the polarization beam combiner; the polarization controller rotates the polarization state of the combined beam signal by 45 degrees relative to the original main axis direction, and the combined beam signal is divided into two paths of input balanced photoelectric detectors by a polarization beam splitter for differential detection, and finally a double-chirp signal or a multi-band phase coding signal of the multi-band signal is obtained.
(III) beneficial effects
From the above technical scheme, the invention has the following beneficial effects:
1. the parallel multi-band multi-format microwave signal generating device provided by the invention can generate optical frequency comb signals and optical signals loaded with baseband signals, and the signals are in a parallel connection mode, so that the wavelength crosstalk problem caused by a serial structure can be avoided.
2. The parallel multi-band multi-format microwave signal generating device provided by the invention can simultaneously generate double chirp signals of a plurality of wave bands or simultaneously generate phase coding signals of a plurality of wave bands.
3. The parallel multi-band multi-grid microwave signal generating device provided by the invention does not need to use a mode-locked laser or a laser plus an additional modulator as a light source, has a simple structure, is low in cost and is easy to integrate.
Drawings
Fig. 1 is a schematic diagram of a multi-band multi-lattice type microwave signal generating apparatus based on a parallel structure.
Fig. 2 is a schematic diagram of a multi-band multi-lattice microwave signal generating apparatus based on a dual-polarization dual-parallel mach-zehnder modulator.
Fig. 3 is a schematic diagram of a multi-band multi-lattice microwave signal generating apparatus based on a dual-polarization dual-drive mach-zehnder modulator.
Fig. 4 is a schematic diagram of a multi-band multi-lattice microwave signal generating apparatus based on a dual polarization mach-zehnder modulator.
Fig. 5 (a) is a waveform diagram of a multi-band dual chirp signal obtained according to the principle simulation shown in fig. 4; fig. 5 (b) is a graph of the instantaneous frequency of a multi-band dual chirp signal obtained by short-time fourier transform according to the principle shown in fig. 4.
FIG. 6 (a) is a waveform diagram of a multi-band phase encoded signal obtained according to the principle simulation shown in FIG. 4; FIG. 6 (b) is a block diagram of a baseband encoded control signal analog loaded onto the second serial-leg Mach-Zehnder modulator of FIG. 4; FIG. 6 (c) is a waveform diagram of the phase encoded signal of 6GHz generated simultaneously with the simulation of FIG. 4; FIG. 6 (d) is a simulation of the phase of the simultaneously generated 6GHz phase encoded signal from FIG. 4; FIG. 6 (e) is a waveform diagram of the 12GHz phase encoded signal generated simultaneously with the simulation of FIG. 4; fig. 6 (f) is a simulation of the phase of the 12GHz phase encoded signal obtained in fig. 4.
Reference numerals:
1-laser
2-microwave source
3-first voltage source
4-first electro-optic modulator
5-second electro-optic modulator
6-90 degree polarization rotator
7-second voltage source
8-Arbitrary waveform generator
9-polarization beam combiner
10-polarization controller
11-polarization beam splitter
12-balanced photodetector
13-first Mach-Zehnder modulator
14-second Mach-Zehnder modulator
15-third Mach-Zehnder modulator
16-fourth Mach-Zehnder modulator
17-first dual drive Mach-Zehnder modulator
18-second dual drive Mach-Zehnder modulator
19-first phase shifter
20-second phase shifter
Detailed Description
The present invention will be further described in detail below with reference to specific embodiments and with reference to the accompanying drawings, in order to make the objects, technical solutions and advantages of the present invention more apparent.
Fig. 1 is a schematic diagram of a multi-band multi-lattice type microwave signal generating apparatus based on a parallel structure. As shown in fig. 1, the apparatus includes: a laser 1 for emitting an optical signal; the output end of the laser 1 is connected with the first input end of the parallel modulation module; the output end of the microwave source 2 is connected with the second input end of the parallel modulation module and is used for adjusting the power of the microwave signal input into the parallel modulation module and sending out the microwave signal; the output end of the arbitrary waveform generator 8 is connected with the third input end of the parallel modulation module; for emitting a baseband signal comprising a baseband chirp signal and a baseband coding control signal; the first voltage source 3 is used for inputting direct-current bias voltage to the parallel modulation module; the second voltage source 7 is used for inputting a direct current bias voltage to the parallel modulation module; and the detection module is used for differentially detecting the signals input by the parallel modulation module and outputting multi-band double-chirp signals or multi-band phase coded signals.
The parallel modulation module modulates the optical signals input by the laser 1, the microwave signals input by the microwave source 2 and the baseband signals input by the arbitrary waveform generator 8 to generate optical frequency comb signals with orthogonal polarization and optical signals loaded with the baseband signals, and synthesizes the modulated signals into one path to be input to the detection module.
The parallel modulation module comprises a first electro-optical modulator 4, a second electro-optical modulator 5, a 90-degree polarization rotator 6 and a polarization beam combiner 9; the first electro-optical modulator 4 forms a first serial branch of the parallel modulation module, the output end of the second electro-optical modulator 5 is connected with the input end of the 90-degree polarization rotator 6 to form a second serial branch of the parallel modulation module, the first serial branch and the second serial branch are connected in parallel to the input end of the polarization beam combiner 9, and the polarization beam combiner 9 is used for combining optical signals generated by the first serial branch and the second serial branch into one path.
The detection module comprises a polarization controller 10, a polarization beam splitter 11 and a balanced photoelectric detector 12; the polarization beam combiner 9, the polarization controller 10, the polarization beam splitter 11 and the balance photoelectric detector 12 are connected in sequence; the two output ends of the polarization beam splitter 11 are respectively connected with the two input ends of the balance photoelectric detector 12; the polarization controller 10 rotates one path of signal sent by the polarization beam combiner 9 by 45 degrees relative to the original main axis direction, and the one path of signal is divided into two paths of signals under the action of the polarization beam splitter 11 and is input to the balance photoelectric detector 12.
The first electro-optical modulator 4 generates and outputs at least five optical frequency comb signals by adjusting the microwave signal power of the microwave source 2 and the direct current bias voltage of the first voltage source 3.
By adjusting the 90 ° polarization rotator 6, the polarization state of the optical signal output by the second electro-optical modulator 5 is perpendicular to the polarization state of the optical frequency comb signal output by the first electro-optical modulator 4.
The balanced photodetector 12 performs differential detection on two input signals, so that the two signals are subjected to beat frequency and then subtracted to generate multi-band multi-format microwave signal output.
Fig. 2 is a schematic diagram of a multi-band multi-lattice microwave signal generating apparatus based on a dual-polarization dual-parallel mach-zehnder modulator. As shown in fig. 2, the first mach-zehnder modulator 13 and the second mach-zehnder modulator 14 form a first serial branch, the third mach-zehnder modulator 15 and the fourth mach-zehnder modulator 16 are connected in parallel and then connected in series with the 90 ° polarization modulator 6 to form a second serial branch, and the first serial branch and the second serial branch are connected in parallel to the polarization beam combiner 9 to form a parallel modulation module; the input end of the first mach-zehnder modulator 13, the input end of the second mach-zehnder modulator 14, the input end of the third mach-zehnder modulator 15 and the input end of the fourth mach-zehnder modulator 16 in the parallel modulation module are respectively connected with the output ends of the laser 1, the microwave source 2 inputs microwave signals to the first mach-zehnder modulator 13, and the first voltage source 3 respectively inputs direct current bias voltages to the first mach-zehnder modulator 13, the second mach-zehnder modulator 14 and the first serial branch; the arbitrary waveform generator 8 inputs a baseband signal to the fourth Mach-Zehnder modulator 16, and the second voltage source 7 inputs direct current biases to the third Mach-Zehnder modulator 15, the fourth Mach-Zehnder modulator 16 and the second serial branch, respectively; the polarization beam combiner 9, the polarization controller 10, the polarization beam splitter 11 and the balance photoelectric detector 12 are sequentially connected.
Fig. 3 is a schematic diagram of a multi-band multi-lattice microwave signal generating apparatus based on a dual-polarization dual-drive mach-zehnder modulator. As shown in fig. 3, the first dual-drive mach-zehnder modulator 17 forms a first serial branch of the parallel modulation module, the second dual-drive mach-zehnder modulator 18 and the 90 ° polarization modulator 6 are connected in series to form a second serial branch of the parallel modulation module, and the first serial branch and the second serial branch are connected in parallel to the polarization beam combiner 9 to form the parallel modulation module; the input end of the first dual-drive mach-zehnder modulator 17 and the input end of the second dual-drive mach-zehnder modulator in the parallel modulation module are respectively connected with the output ends of the laser 1, the microwave source 2 inputs microwave signals to the first dual-drive mach-zehnder modulator 17, the first voltage source 3 inputs direct current bias voltage to the first dual-drive mach-zehnder modulator 17, and the second voltage source 7 inputs direct current bias voltage to the second dual-drive mach-zehnder modulator 18. The microwave signal sent by the microwave source is divided into two paths, wherein one path of signal is directly input into the first double-drive Mach-Zehnder modulator 17, and the other path of signal is input into the first double-drive Mach-Zehnder modulator 17 through the first phase shifter 19; the baseband signal from the arbitrary waveform generator 8 is split into two paths, one of which is directly input to the second dual-drive mach-zehnder modulator 18, and the other of which is input to the second dual-drive mach-zehnder modulator 18 via the second phase shifter 20. The polarization beam combiner 9, the polarization controller 10, the polarization beam splitter 11 and the balance photoelectric detector 12 are sequentially connected.
Fig. 4 is a schematic diagram of a multi-band multi-lattice microwave signal generating apparatus based on a dual polarization mach-zehnder modulator. As shown in fig. 4, the first mach-zehnder modulator 13 forms a first serial branch of the parallel modulation module, the second mach-zehnder modulator 14 and the 90 ° polarization modulator 6 are connected in series to form a second serial branch of the parallel modulation module, and the first serial branch and the second serial branch are connected in parallel to the polarization beam combiner 9 to form the parallel modulation module; the input end of the first Mach-Zehnder modulator 13 and the input end of the second Mach-Zehnder modulator in the parallel modulation module are respectively connected with the output ends of the laser 1, the microwave source 2 inputs microwave signals to the first Mach-Zehnder modulator 13, the first voltage source 3 inputs direct current bias voltage to the first Mach-Zehnder modulator 13, and the second voltage source 7 inputs direct current bias voltage to the second Mach-Zehnder modulator 14; the polarization beam combiner 9, the polarization controller 10, the polarization beam splitter 11 and the balance photoelectric detector 12 are sequentially connected.
The theory of the parallel multi-band multi-lattice microwave signal generating device provided by the invention is as follows:
the optical field output by the laser 1 can be expressed asThe frequency of the output of the microwave source 2 is omega 1 The microwave signal of the (a) is loaded on a first electro-optical modulator 4 with the polarization state of X to generate an optical frequency comb signal; the arbitrary waveform generator 8 generates a baseband coding control signal mb (t) to be loaded on the second electro-optical modulator 5 with the polarization state of Y, and the two paths of optical signals are as follows:
wherein A is the amplitude of the input light field, e is the natural index, j is the imaginary number, ω 0 Is the angular frequency of the light field, t is the time, omega 1 For the radio frequency, E, of the microwave source 2 output x ，E y The optical fields with two vertical polarization states are respectively in parallel connection structure, and m is the modulation coefficient of the coded signal.
The two paths of optical signals are sent to a polarization controller 10 after being combined by a polarization beam combiner 9, and the two optical fields in two perpendicular polarization states are rotated by 45 degrees along the main axis direction by adjusting the polarization controller 10 and then are separated by a polarization beam splitter 11 to serve as two input signals of a balance photoelectric detector 12. The polarization beam splitter 11 outputs an optical signal of:
wherein E is 1 For one output light field of the polarizing beam splitter 11, E 2 The light field is output for the other path of the polarizing beam splitter 11.
The two paths of signals are input to the balance photoelectric detector 12 for differential detection, and photoelectric conversion is carried out to obtain a photocurrent signal:
wherein i is BPD To balance the photocurrent output by the photodetector 12,
when the baseband signal generated by the arbitrary waveform generator 8 is a baseband chirp signal, i.e., mb (t) =kt 2 When the photocurrent is generated, the:
i BPD (t)＝sin(kt 2 )-sin(ω 1 t-kt 2 )+sin(ω 1 t+kt 2 )-sin(2ω 1 t-kt 2 )+sin(2ω 1 t+kt 2 ) (4)
where k is the chirp rate of the chirp signal generated by the arbitrary waveform generator 8,
the baseband signal may be filtered by a suitable electrical filter, so that the present solution may produce a multi-band double-chirped microwave signal.
When the arbitrary waveform generator 8 generates the baseband coding control signal, the photocurrent after photoelectric conversion by the balanced photodetector 12 is:
i BPD (t)＝sin(mb(t))+cos(ω 1 t)sin(mb(t))+cos(2ω 1 t)sin(mb(t)) (5)
wherein, the liquid crystal display device comprises a liquid crystal display device,
it follows that, since the value of the code signal mb (t) is "+1" or "—1" having positive and negative polarities, the phase code of "0" or "pi" of the multiband microwave signal can be realized. Therefore, the parallel structure can also simultaneously generate phase-coded microwave signals of a plurality of frequency bands.
The first electro-optical modulator and the second electro-optical modulator are one or more of a commercial lithium niobate modulator, a silicon-based integrated modulator, a dual-polarization dual-parallel Mach-Zehnder modulator, a dual-polarization dual-drive Mach-Zehnder modulator and a dual-polarization Mach-Zehnder modulator.
The first branch modulators 1 corresponding to different parallel modulation modules have different principles of generating optical frequency combs, but can generate at least 5 optical frequency comb signals. And loading baseband signals corresponding to different direct current bias states of the second electro-optic modulators in the second serial branches of different parallel modulation modules. The polarization states of the first serial branch and the second serial branch are mutually orthogonal.
Based on the analysis of the foregoing parallel multi-band multi-format signal generation, in some alternative embodiments, as shown in fig. 2, when the parallel modulation module is a dual-polarization dual-parallel mach-zehnder modulator, the first electro-optical modulator in the first serial branch of the parallel modulation module is a dual-parallel mach-zehnder modulator, one radio frequency input end of the first electro-optical modulator loads the microwave signal output by the microwave source 2, and the other radio frequency input end is idle, and the optical field thereof can be expressed as:
wherein phi is x1 、φ x2 、φ x3 The phase difference of the sub-arm and the main arm, which are respectively introduced by DC bias, and the beta is the modulation coefficient of the microwave signal.
The intensity of the optical carrier and the n-order sidebands can be expressed as:
wherein J is n Respectively n-th order bezier functions of the first class.
To obtain a flat optical frequency comb, the harmonic signal strengths of the different orders should be equal. When the first order harmonic and the second order harmonic are equal in intensity, i.e. solve for I x，±1 (t)＝I x，±2 (t) to obtain formula (9); when the first order harmonic is equal to the optical carrier intensity, i.e. solve for I x，±1 (t)＝I x，0 (t), then the formula (10) is obtained:
wherein beta is the modulation factor of the microwave signal, J 0 ，J 1 ，J 2 The first class Bessel functions are 0 th order, 1 st order and 2 nd order respectively.
Thereby can be used forSee, phase difference phi introduced by adjusting DC signal x1 、φ x2 、φ x3 And the value of the modulation factor beta, five flat optical frequency combs can be realized.
The polarization state of the second serial branch dual parallel mach-zehnder modulator of the parallel modulation module is perpendicular to that of the dual parallel mach-zehnder modulator in the first serial branch, one radio frequency input end of the second serial branch dual parallel mach-zehnder modulator loads the baseband signal generated by the arbitrary waveform generator 8, the other radio frequency input end is idle, the two parallel mach-zehnder modulators are biased at the maximum transmission point, and the downlink optical field signal can be expressed as:
in some alternative embodiments, as shown in fig. 3, when the parallel modulation module is a dual-polarization dual-drive mach-zehnder modulator, the first serial-branch electro-optical modulator is a first dual-drive mach-zehnder modulator 17, and the output signal of the microwave source 2 is divided into two paths, one path is directly loaded to one radio frequency input end of the first dual-drive mach-zehnder modulator 17, and the other path is loaded to the other radio frequency input end of the second dual-drive mach-zehnder modulator 18 after passing through the first phase shifter 19. Its light field can be expressed as:
wherein phi is x1 、φ x2 The phase difference introduced for the dc offset of the upper path,for the phase shift introduced by the phase shifter, to obtain a flat optical frequency comb, the harmonic signal intensities of different orders should be equal, i.e. solve equation (13):
|E x，0 (t)| 2 ＝|E x，±1 (t)| 2 ＝|E x，±2 (t)| 2 (13)
wherein E is x，0 ，E x，±1 ，E x，±2 The optical fields of the optical signals of 0 order, 1 order and 2 order in the X polarization state respectively.
It can be solved that, when beta 1.84 is satisfied,(φ x1 -φ x2 ) With/2=0.498, 5 optical frequency combs can be produced.
In this embodiment, the polarization state of the second dual-drive mach-zehnder modulator 18 in the second series leg is orthogonal to the polarization state of the first dual-drive mach-zehnder modulator 17 in the first series leg. The baseband signal generated by the arbitrary waveform generator 8 is split into two paths, one of which is loaded onto the second dual-drive mach-zehnder modulator 18 after passing through the phase shifter, and the other of which is directly loaded onto the second dual-drive mach-zehnder modulator 18. By adjusting the second phase shifter 20 to have the phase difference of two arms pi, the second dual-drive mach-zehnder modulator 18 optical field signal is:
in some alternative embodiments, as shown in fig. 4, when the parallel modulation module is a dual polarization mach-zehnder modulator, the output signal of the microwave source 2 is connected to the rf input terminal of the upper mach-zehnder modulator, and the optical field thereof may be expressed as:
wherein phi is x A phase difference introduced for the up dc bias.
The harmonic signal strengths of the different orders can be expressed as equation (16):
wherein E is x，n For the optical field of the optical signal of order n,
to obtain flat optical frequency comb, the harmonic signal strength of different orders is equal, i.e. solving I x，0 (t)＝I x，±1 (t)＝I x，±2 (t) wherein I x，0 (t)，I x，±1 (t)，I x，±2 (t)，I x，±n (t) are the 0 order, 1 order, 2 order and n order photocurrents in the X polarization state, respectively. When beta-1.84 is satisfied,φ x approximately 0.9949, 5 optical frequency combs can be produced.
In this embodiment, the drop is another mach-zehnder modulator, the radio frequency input end of which is loaded with the baseband signal generated by the arbitrary waveform generator 8 and biased at the minimum transmission point, and the optical field signal of the drop is:
fig. 5 shows simulation results of a multi-band dual chirp signal. (a) A multi-band double-chirp signal waveform diagram obtained through simulation; (b) And (b) obtaining a multi-band double-chirp signal instantaneous frequency map after short-time Fourier transform. It can be seen that the parallel multi-band signal generator of the present invention can be used to realize a dual chirp signal of a simultaneous multi-center frequency.
Fig. 6 shows simulation results of a multi-band phase encoded signal. (a) The simulation results show that the waveform diagram of the multiband phase coded signal comprises a frequency doubling 6GHz coded signal and a frequency doubling 12GHz coded signal; (b) For the analog of the 8 bit format "-1, -1,1" -generated by the arbitrary waveform generator 8, the code rate of the baseband code control signal is 2Gbit/s, two cycles are shown in the figure; (c) And (e) respectively generating a 6GHz phase coding signal waveform diagram and a 12GHz phase coding signal waveform diagram simultaneously by simulation; (d) And (f) are the phases of the 6GHz and 12GHz signals recovered after Hilbert transform, respectively. It can be seen that the parallel multi-band signal generator of the present invention can be used to achieve a phase encoded signal of simultaneous multi-center frequencies.
The foregoing description of the embodiments has been provided for the purpose of illustrating the general principles of the invention, and is not meant to limit the invention thereto, but to limit the invention thereto, and any modifications, equivalents, improvements and equivalents thereof may be made without departing from the spirit and principles of the invention.
Claims (9)
1. A parallel multi-band multi-lattice microwave signal generating apparatus, comprising:
the laser is used for emitting optical signals;
the output end of the second electro-optical modulator is connected with the input end of the 90-degree polarization rotator to form a second serial branch of the parallel modulation module, the first serial branch and the second serial branch are connected in parallel to the input end of the polarization beam combiner, and the polarization beam combiner is used for combining optical signals generated by the first serial branch and the second serial branch into one path;
the output end of the microwave source is connected with the second input end of the parallel modulation module and is used for adjusting the power of the microwave signal input into the parallel modulation module and sending out the microwave signal;
the output end of the random waveform generator is connected with the third input end of the parallel modulation module and is used for sending out a baseband signal, and the baseband signal comprises a baseband linear frequency modulation signal and a baseband coding control signal;
the first voltage source is used for inputting a direct-current bias voltage to the parallel modulation module;
the second voltage source is used for inputting a direct-current bias voltage to the parallel modulation module;
the detection module is used for differentially detecting the signals input by the parallel modulation module and outputting multi-band double-chirp signals or multi-band phase coded signals;
the parallel modulation module modulates the optical signals input by the laser, the microwave signals input by the microwave source and the baseband signals input by the arbitrary waveform generator to generate mutually orthogonal optical frequency comb signals and optical signals loaded with the baseband signals, and synthesizes one path of modulated signals to be input to the detection module.
2. The parallel multi-band multi-lattice microwave signal generating apparatus of claim 1, wherein the detection module comprises a polarization controller, a polarization beam splitter and a balanced photodetector;
the polarization beam combiner, the polarization controller, the polarization beam splitter and the balance photoelectric detector are connected in sequence;
the two output ends of the polarization beam splitter are respectively connected with the two input ends of the balance photoelectric detector;
the polarization controller rotates one path of signal sent by the polarization beam combiner by 45 degrees relative to the original main axis direction, and the one path of signal is divided into two paths of signals under the action of the polarization beam splitter and is input to the balance photoelectric detector.
3. The parallel multi-band multi-lattice microwave signal generating apparatus of claim 1, wherein the first electro-optic modulator generates and outputs no less than five optical frequency comb signals by adjusting the microwave signal power of the microwave source and the dc bias voltage of the first voltage source.
4. The parallel multi-band multi-lattice microwave signal generating apparatus of claim 1, wherein the polarization state of the optical signal output by the second electro-optical modulator is perpendicular to the polarization state of the optical frequency comb signal output by the first electro-optical modulator by adjusting the 90 ° polarization rotator.
5. The parallel multi-band multi-lattice microwave signal generator of claim 2, wherein the balanced photodetector differentially detects two input signals, and the two signals are subjected to beat frequency and then subtracted to generate multi-band multi-lattice microwave signal output.
6. The parallel multi-band multi-lattice microwave signal generator of claim 1, wherein the first electro-optic modulator is formed by parallel connection of a first mach-zehnder modulator and a second mach-zehnder modulator; the second electro-optic modulator is formed by connecting a third Mach-Zehnder modulator and a fourth Mach-Zehnder modulator in parallel.
7. The parallel multi-band multi-lattice microwave signal generating apparatus of claim 1, wherein the first electro-optic modulator is a first dual-drive mach-zehnder modulator and the second electro-optic modulator is a second dual-drive mach-zehnder modulator.
8. The parallel multi-band multi-lattice microwave signal generating apparatus of claim 1, wherein the first electro-optic modulator is a first mach-zehnder modulator and the second electro-optic modulator is a second mach-zehnder modulator.
9. The parallel multi-band multi-lattice microwave signal generator of claim 1, wherein the first and second electro-optic modulators are commercial lithium niobate modulators and/or silicon-based integrated modulators.
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