阅读说明：本技术 一种基于双平行相位调制器的镜像抑制混频器 (Image rejection mixer based on double parallel phase modulators ) 是由 胡大鹏 金长新 刘强 于 2020-05-25 设计创作，主要内容包括：一种基于双平行相位调制器的镜像抑制混频器,两个光纤输出到相位调制器Ⅰ和相位调制器Ⅱ,相位调制器Ⅰ和相位调制器Ⅱ用于对分布式反馈激光器输出的光信号进行调制,超宽带天线的接收端面向无线信道,用于接收射频信号和镜像信号,参考微波信号源用于提供特定频率的稳定参考微波信号。偏振合束器将相位调制器Ⅰ和相位调制器Ⅱ输出的两束偏振方向正交的线偏振光合成一束后通过掺铒光纤放大器进行功率放大,放大后通过光带通滤波器滤除光信号中的正一阶边带,之后通过光耦合器均分两路光信号,最终通过90°电混合器混合两路电信号,从而进行消除镜像信号。基于相位调制器实现镜像干扰的一致,以摆脱强度调制器存在的直流偏置偏移的问题。(The image rejection mixer based on the double parallel phase modulators is characterized in that two optical fibers are output to a phase modulator I and a phase modulator II, the phase modulator I and the phase modulator II are used for modulating optical signals output by a distributed feedback laser, a receiving end of an ultra-wideband antenna faces a wireless channel and is used for receiving radio frequency signals and image signals, and a reference microwave signal source is used for providing stable reference microwave signals with specific frequency. The polarization beam combiner combines two linearly polarized light beams output by the phase modulator I and the phase modulator II and with orthogonal polarization directions into one beam, the power amplification is carried out through the erbium-doped fiber amplifier, a positive first-order sideband in an optical signal is filtered through the optical band-pass filter after the amplification, then the two optical signals are equally divided through the optical coupler, and finally two paths of electric signals are mixed through the 90-degree electric mixer, so that the mirror image signal is eliminated. The phase modulator is used for realizing the consistency of image interference so as to get rid of the problem of DC offset existing in the intensity modulator.)

1. An image reject mixer based on a dual parallel phase modulator, comprising:

the distributed feedback laser (1) is used for emitting optical signals with the wavelength of 1530nm-1610 nm;

the input end of the polarization controller I (2) is connected to the distributed feedback laser (1) and is used for changing the polarization state of the optical signal;

the input end of the polarization beam splitter I (3) is connected to the output end of the polarization controller I (2) and is used for coupling the light containing orthogonal linear polarization light output by the polarization controller I (2) to two optical fiber outputs;

the input end of the phase modulator I (4) is connected to one optical fiber output end of the polarization beam splitter I (3) and used for modulating an optical signal, and the input end of the phase modulator II (6) is connected to the other optical fiber output end of the polarization beam splitter I (3) and used for modulating the optical signal;

the ultra-wideband antenna (8) is connected with the phase modulator I (4) and is used for receiving radio frequency signals and image signals;

a reference microwave signal source (7) connected to the phase modulator II (6);

the input end of the polarization beam combiner (9) is respectively connected with the output end of the phase modulator I (4) and the output end of the phase modulator II (6);

the input end of the erbium-doped fiber amplifier (10) is connected with the output end of the polarization beam combiner (9);

an optical bandpass filter (11), the input end of which is connected to the output end of the erbium-doped fiber amplifier (10), for filtering the positive first-order sideband of the optical signal;

an optical coupler (12) having an input end connected to an output end of the optical bandpass filter (11);

polarization controller II (13) and polarization controller III (16), its input is connected respectively in the output of optical coupler (12), the output of polarization controller II (13) is connected in the input of polarization beam splitter II (14), the output of polarization beam splitter II (14) is connected in the input of photoelectric balance detector I (15), the output of polarization controller III (16) is connected in the input of polarization beam splitter III (17), the output of polarization beam splitter III (17) is connected in the input of photoelectric balance detector II (18), the output of photoelectric balance detector I (15) and photoelectric balance detector II (18) is connected in 90 electric blender (19).

2. The dual parallel phase modulator based image reject mixer of claim 1, wherein: the ultra-wideband antenna is characterized by further comprising a power attenuator I (5), wherein the input end of the power attenuator I (5) is connected with the ultra-wideband antenna (8), and the output end of the power attenuator I (5) is connected with the phase modulator I (4).

Technical Field

The invention relates to the field of microwave photons, in particular to an image rejection mixer based on a double parallel phase modulator.

Background

In recent years, the development of microwave photonics has attracted extensive attention, and compared with the traditional electrical technology, microwave photonics has the advantages of larger bandwidth, better isolation, electromagnetic interference resistance, light weight, small size and the like. The microwave photonic mixer plays an important role in the process of down-converting a high-frequency signal or up-converting a low-frequency signal. However, in practical applications, the artificially generated image signal significantly interferes with the frequency conversion result of the mixer. Because the intermediate frequency signal after the frequency conversion of the image signal and the intermediate frequency signal after the frequency conversion of the radio frequency signal have the same frequency, the intermediate frequency signal and the radio frequency signal cannot be separated through a filter, and finally, the information carried in the signal is distorted. Therefore, mixers having image rejection techniques have been widely studied.

In recent years, many microwave photonic mixer schemes with image rejection have been proposed. In order to eliminate the image signal, the simplest and straightforward method is to filter out the image signal with an optical or electrical filter before it enters the mixer. Although this solution is simple in principle and structure, it cannot achieve broadband operation. Furthermore, when low if reception is used, this method is not applicable due to the limitation of the Q value of the filter.

In addition to the above methods, the phase cancellation method (Hartley structure) can also realize the image rejection function. The basic idea of the method is to introduce two local oscillator signals with equal frequency and orthogonal phase, and finally eliminate components generated by image signals by using a 90-degree electric domain orthogonal coupler at the output end. Most current image rejection mixers are based on intensity modulators and suffer from dc offset drift problems. Compared with an intensity modulator, the phase modulator has low insertion loss and high optical power processing capability, and can eliminate the direct current bias drift problem. However, many current mixers based on phase modulators can only achieve frequency conversion function, and do not have image rejection function.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides an image rejection mixer based on a double parallel phase modulator, which gets rid of the problem of DC offset drift of an intensity modulator.

The technical scheme adopted by the invention for overcoming the technical problems is as follows:

an image reject mixer based on a dual parallel phase modulator, comprising:

the distributed feedback laser is used for emitting optical signals with the wavelength of 1530nm-1610 nm;

the input end of the polarization controller I is connected to the distributed feedback laser and used for changing the polarization state of the optical signal;

the input end of the polarization beam splitter I is connected with the output end of the polarization controller I and is used for coupling the polarized light containing the orthogonal linear polarization light output by the polarization controller I to the output of the two optical fibers;

the input end of the phase modulator I is connected to one optical fiber output end of the polarization beam splitter I and used for modulating an optical signal, and the input end of the phase modulator II is connected to the other optical fiber output end of the polarization beam splitter I and used for modulating the optical signal;

the ultra-wideband antenna is connected with the phase modulator I and used for receiving radio frequency signals and image signals;

the reference microwave signal source is connected to the phase modulator II;

the input end of the polarization beam combiner is respectively connected with the output end of the phase modulator I and the output end of the phase modulator II;

the input end of the erbium-doped fiber amplifier is connected with the output end of the polarization beam combiner;

the input end of the optical bandpass filter is connected to the output end of the erbium-doped fiber amplifier and is used for filtering a positive first-order sideband of an optical signal;

the input end of the optical coupler is connected with the output end of the optical band-pass filter;

polarization controller II and polarization controller III, its input is connected respectively in the output of optical coupler, the output of polarization controller II is connected in the input of polarization beam splitter II, the output of polarization beam splitter II is connected in the input of photoelectric balance detector I, the output of polarization controller III is connected in the input of polarization beam splitter III, the output of polarization beam splitter III is connected in the input of photoelectric balance detector II, output of photoelectric balance detector I and photoelectric balance detector II is connected in 90 electric mixers.

Furthermore, the ultra-wideband antenna also comprises a power attenuator I, wherein the input end of the power attenuator I is connected with the ultra-wideband antenna, and the output end of the power attenuator I is connected with the phase modulator I.

The invention has the beneficial effects that: the two optical fibers are output to a phase modulator I and a phase modulator II, the phase modulator I and the phase modulator II are used for modulating optical signals output by the distributed feedback laser, a receiving end of the ultra-wideband antenna faces a wireless channel and is used for receiving radio frequency signals and image signals, and a reference microwave signal source is used for providing stable reference microwave signals with specific frequency. The polarization beam combiner combines two beams of linearly polarized light with orthogonal polarization directions output by the phase modulator I and the phase modulator II into a beam, the beam is subjected to power amplification through an erbium-doped fiber amplifier, a positive first-order sideband in an optical signal is filtered through an optical band-pass filter after amplification, then two paths of optical signals are equally divided through an optical coupler, one path of optical signals is subjected to polarization state change through a polarization controller II, single output containing the orthogonal linearly polarized light is respectively coupled to two optical fibers through a polarization beam splitter II to be output, then the optical signals output by the two optical fibers are converted into electric signals through an optical balance detector I, the other path of optical signals is subjected to polarization state change through a polarization controller III, then the single output containing the orthogonal linearly polarized light is respectively coupled to the two optical fibers through a polarization beam splitter III, and then the optical signals output by the two optical fibers through an optical balance detector II are converted into electric signals, and finally, mixing the two paths of electric signals through a 90-degree electric mixer so as to eliminate the mirror image signal. The phase modulator is used for realizing the consistency of image interference so as to get rid of the problem of DC offset existing in the intensity modulator. The structure is simple, and the problem of direct current offset drift is eliminated.

Drawings

FIG. 1 is a schematic structural view of the present invention;

in the figure, 1 is a distributed feedback laser 2, a polarization controller I3, a polarization beam splitter I4, a phase modulator I5, a power attenuator I6, a phase modulator II 7, a reference microwave signal source 8, an ultra wide band antenna 9, a polarization beam combiner 10, an erbium-doped fiber amplifier 11, an optical bandpass filter 12, an optical coupler 13, a polarization controller II 14, a polarization beam splitter II 15, a photoelectric balance detector I16, a polarization controller III 17, a polarization beam splitter III 18 and a photoelectric balance detector II 19.90-degree electric mixer.

Detailed Description

The invention is further described below with reference to fig. 1.

An image reject mixer based on a dual parallel phase modulator, comprising: the distributed feedback laser 1 is used for emitting optical signals with the wavelength of 1530nm-1610 nm; the input end of the polarization controller I2 is connected to the distributed feedback laser 1 and is used for changing the polarization state of the optical signal; the input end of the polarization beam splitter I3 is connected to the output end of the polarization controller I2 and is used for coupling the light containing orthogonal linear polarization light output by the polarization controller I2 to the output of two optical fibers; the input end of the phase modulator I4 is connected to one optical fiber output end of the polarization beam splitter I3 and used for modulating an optical signal, and the input end of the phase modulator II 6 is connected to the other optical fiber output end of the polarization beam splitter I3 and used for modulating the optical signal; the ultra-wideband antenna 8 is connected with the phase modulator I4 and used for receiving radio frequency signals and image signals; a reference microwave signal source 7 connected to the phase modulator II 6; the input end of the polarization beam combiner 9 is respectively connected with the output end of the phase modulator I4 and the output end of the phase modulator II 6; an input end of the erbium-doped fiber amplifier 10 is connected with an output end of the polarization beam combiner 9; an optical bandpass filter 11, the input end of which is connected to the output end of the erbium-doped fiber amplifier 10, for filtering the positive first-order sideband of the optical signal; an optical coupler 12 having an input end connected to an output end of the optical bandpass filter 11; polarization controller II 13 and polarization controller III 16, its input is connected respectively in the output of optical coupler 12, the output of polarization controller II 13 is connected in the input of polarization beam splitter II 14, the output of polarization beam splitter II 14 is connected in the input of photoelectric balance detector I15, the output of polarization controller III 16 is connected in the input of polarization beam splitter III 17, the output of polarization beam splitter III 17 is connected in the input of photoelectric balance detector II 18, the output of photoelectric balance detector I15 and photoelectric balance detector II 18 is connected in 90 electric mixer 19. An optical signal with a wavelength of 1530nm-1610nm emitted by the distributed feedback laser 1 is changed in polarization state through a polarization controller I2 and then is respectively coupled to two optical fibers through a polarization beam splitter I3 for output, the two optical fibers are output to a phase modulator I4 and a phase modulator II 6, the phase modulator I4 and the phase modulator II 6 are used for modulating the optical signal output by the distributed feedback laser, a receiving end of an ultra-wideband antenna 8 faces to a wireless channel and is used for receiving a radio frequency signal and an image signal, and a reference microwave signal source 7 is used for providing a stable reference microwave signal with a specific frequency. The polarization beam combiner 9 combines two beams of linearly polarized light with orthogonal polarization directions output by the phase modulator I4 and the phase modulator II 6 into one beam, the beam is subjected to power amplification through an erbium-doped optical fiber amplifier 10, a positive first-order sideband in an optical signal is filtered through an optical band pass filter 11 after amplification, then two paths of optical signals are equally divided through an optical coupler 12, one path of optical signals is subjected to polarization state change through a polarization controller II 13 and then is respectively coupled to two optical fibers for output through a polarization beam splitter II 14, then the optical signals output by the two optical fibers are converted into electric signals through an optical balance detector I15, the other path of optical signals is subjected to polarization state change through a polarization controller III 16 and then is respectively coupled to the two optical fibers for output through a polarization beam splitter III 17, and then the optical signals output by the two optical fibers are converted into electric signals through an optical balance detector II 18, finally, the two electrical signals are mixed by a 90-degree electrical mixer 19, so that the image signal is eliminated. The phase modulator is used for realizing the consistency of image interference so as to get rid of the problem of DC offset existing in the intensity modulator. The structure is simple, and the problem of direct current offset drift is eliminated.

Furthermore, the ultra-wideband antenna further comprises a power attenuator I5, wherein the input end of the power attenuator I5 is connected with the ultra-wideband antenna 8, and the output end of the power attenuator I5 is connected with the phase modulator I4. The output end of the power attenuator I5 is connected with the microwave access port of the phase modulator I4 and is used for attenuating overhigh received signal power.

The above description is only a preferred embodiment of the present invention, and is only used to illustrate the technical solutions of the present invention, and not to limit the protection scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.