阅读说明：本技术 一种基于光纤色散的光波束形成预加重装置 (Optical beam forming pre-emphasis device based on optical fiber dispersion ) 是由 林桂道 范晶晶 张昀 余博昌 陈奇 于 2020-11-18 设计创作，主要内容包括：本发明公开了一种基于光纤色散的光波束形成预加重装置,包括天线阵面通道、激光器、电光调制器、预加重延时线、波分复用器、光纤放大器、光分路器、色散光纤、光电探测器；天线阵面每一通道接收的微波信号经电光调制器调制到激光器产生的相应波长的光载波上,经过预加重延时线进入波分复用器,每一通道的预加重延时线产生不同的延时,用于各通道在不同接收角度下产生延时的预加重,波分复用器将所得的光信号复用到一根光纤传输,并经光纤放大器放大后通过光分路器,将复用的多波长光信号等功率分配到多路中,形成不同的波束指向,最终由光电探测器实现光信号到微波信号的转化。本发明结构简单、体积小、重量轻、成本低、系统能耗低、综合效能高。(The invention discloses an optical beam forming pre-emphasis device based on optical fiber dispersion, which comprises an antenna array surface channel, a laser, an electro-optic modulator, a pre-emphasis delay line, a wavelength division multiplexer, an optical fiber amplifier, an optical splitter, a dispersion optical fiber and a photoelectric detector, wherein the antenna array surface channel is connected with the laser; microwave signals received by each channel of the antenna array surface are modulated onto optical carriers with corresponding wavelengths generated by a laser through an electro-optical modulator, the optical carriers enter a wavelength division multiplexer through a pre-emphasis delay line, different delays are generated by the pre-emphasis delay line of each channel and are used for generating delayed pre-emphasis under different receiving angles of each channel, the wavelength division multiplexer multiplexes the obtained optical signals to an optical fiber for transmission, the multiplexed multi-wavelength optical signals are distributed to multiple paths in an equal power mode through an optical splitter after being amplified by an optical fiber amplifier, different beam directions are formed, and finally, the conversion from the optical signals to the microwave signals is realized through a photoelectric detector. The invention has the advantages of simple structure, small volume, light weight, low cost, low system energy consumption and high comprehensive efficiency.)

1. An optical beam forming pre-emphasis device based on optical fiber dispersion is characterized by comprising an antenna array surface channel, a laser, an electro-optic modulator, a pre-emphasis delay line, a wavelength division multiplexer, an optical fiber amplifier, an optical splitter, a dispersion optical fiber and a photoelectric detector which are sequentially arranged;

microwave signals received by each channel on an antenna array surface are modulated onto optical carriers with corresponding wavelengths generated by a laser through an electro-optical modulator, then the optical carriers enter a wavelength division multiplexer through a pre-emphasis delay line, m channels of the antenna array surface correspond to m optical carriers with different wavelengths, the pre-emphasis delay line of each channel generates different delays, the wavelength division multiplexer multiplexes the modulated and pre-emphasis delayed optical signals onto an optical fiber for transmission, the optical signals are amplified by an optical fiber amplifier and then pass through an optical splitter, the multiplexed multi-wavelength optical signals are distributed to n paths in an equal power mode, different delay amounts are realized by dispersion optical fibers of each path, different beam directions are formed, finally, the conversion from the optical signals to the microwave signals is realized by a photoelectric detector, and m and n are positive integers.

2. The optical fiber dispersion-based optical beam forming pre-emphasis apparatus according to claim 1, wherein the number m of the channels of the antenna array is adjusted according to actual conditions, and accordingly, the number of the lasers with different wavelengths, the number of the electro-optical modulators and the number of the channels of the wavelength division multiplexer are consistent with m.

3. The optical fiber dispersion-based optical beam forming pre-emphasis apparatus according to claim 1, wherein the pre-emphasis delay line is located between the electro-optical modulator and the wavelength division multiplexer, the pre-emphasis delay line of each channel generates different delays for pre-emphasis of the delay generated by each channel of the wavefront antenna at different receiving angles, the difference of the pre-emphasis delay lines between adjacent channels is equal to the delay interval introduced between adjacent channels at the maximum scanning angle of the antenna wavefront, and the sign is opposite, so as to realize single positive angle or negative angle reception when the received optical beam forming by the positive and negative angles of the wavefront antenna is performed.

4. The fiber dispersion based optical beam forming pre-emphasis apparatus of claim 1, wherein the number of optical splitter channels n is adjusted according to the actual beam forming requirement.

5. The optical fiber dispersion-based optical beam forming pre-emphasis apparatus of claim 1, wherein said dispersive optical fiber is used for optical beam forming, one beam is formed for each channel dispersive optical fiber, and a positive dispersion coefficient fiber or a negative dispersion coefficient fiber is used according to requirements.

Technical Field

The invention relates to the technical field of microwave photon, in particular to an optical beam forming pre-emphasis device based on optical fiber dispersion.

Background

The traditional phased array radar antenna adopts a microwave phase shifting method, under the condition of wide-angle scanning, the influence of beam pointing inclination and antenna aperture transit time is utilized, a large instantaneous signal bandwidth is difficult to obtain, and the light-operated phased array antenna provides a good solution for solving the problems through an optical fiber true delay beam forming technology (referred to as an optical beam forming technology for short), receives extensive attention, wherein one of the more practical technologies in engineering is the optical beam forming technology based on optical fiber dispersion, and the technology mainly has two modes during optical beam forming: one way is based on the wavelength scanning of a tunable laser, as described in the document 'Fiber-optical Prism True Time-Delay Antenna Feed' by Ronald d. When positive and negative angles of the wave beam are formed, the wave length of the tunable laser is changed, when lambda is less than lambda 0, the time delay of each path of optical fiber is increased, the direction of the wave beam is obliquely upward, and a positive angle is formed; when λ > λ 0, the beam will be transmitted downward, forming a negative angle. The other mode is realized based on a multi-wavelength laser source array, and is realized by modulating microwave signals to each path of light wave through an electro-optical modulator, multiplexing the light wave to one optical fiber through a wavelength division multiplexer, and then splitting the light wave into different light paths through an optical splitter, wherein each optical fiber consists of dispersion optical fibers with different lengths, and the dispersion optical fibers with different lengths have different delay amounts and can form different beams.

The existing optical beam forming technology based on optical fiber dispersion has the following problems:

(1) based on the realization mode of wavelength scanning of the tunable laser, a high-precision tunable laser is needed, the cost is high, secondly, the beam forming is a multi-channel beam forming system and is generated by coherent superposition of signals in each path of optical fiber, each path of delay is required to be adjusted to be equal when the central wavelength is needed, and the difficulty is high when the high-precision delay is adjusted.

(2) The method is based on the implementation mode of a multi-wavelength laser source array, a high-precision tunable laser is not needed, beam forming is a single-channel beam forming system, one path of optical fiber signal can form one beam, the requirement on the length precision of a dispersive optical fiber is low, but when the optical beam forms positive and negative angle scanning, two optical fibers with positive and negative dispersion coefficients are needed, so that two problems are brought, the first optical fiber is more in variety, and the system is complex; secondly, the positive dispersion coefficient fiber has a small dispersion coefficient, and the required fiber length is increased by tens of times compared with the negative dispersion fiber with a large dispersion coefficient, so that the weight and the volume of the system are correspondingly increased.

Disclosure of Invention

The invention aims to provide an optical beam forming pre-emphasis device which has the advantages of simple structure, small volume, light weight, low cost, low system energy consumption and high comprehensive efficiency.

The technical solution for realizing the purpose of the invention is as follows: an optical beam forming pre-emphasis device based on optical fiber dispersion is characterized by comprising an antenna array surface channel, a laser, an electro-optic modulator, a pre-emphasis delay line, a wavelength division multiplexer, an optical fiber amplifier, an optical splitter, a dispersion optical fiber and a photoelectric detector which are sequentially arranged;

microwave signals received by each channel on an antenna array surface are modulated onto optical carriers with corresponding wavelengths generated by a laser through an electro-optical modulator, then the optical carriers enter a wavelength division multiplexer through a pre-emphasis delay line, m channels of the antenna array surface correspond to m optical carriers with different wavelengths, the pre-emphasis delay line of each channel generates different delays, the wavelength division multiplexer multiplexes the modulated and pre-emphasis delayed optical signals onto an optical fiber for transmission, the optical signals are amplified by an optical fiber amplifier and then pass through an optical splitter, the multiplexed multi-wavelength optical signals are distributed to n paths in an equal power mode, different delay amounts are realized by dispersion optical fibers of each path, different beam directions are formed, finally, the conversion from the optical signals to the microwave signals is realized by a photoelectric detector, and m and n are positive integers.

Further, the number m of the channels of the antenna array surface is adjusted according to the actual situation, and correspondingly, the number of the lasers with different wavelengths, the number of the electro-optical modulators and the number of the channels of the wavelength division multiplexer are consistent with the number m.

Furthermore, the pre-emphasis delay line is positioned between the electro-optical modulator and the wavelength division multiplexer, the pre-emphasis delay line of each channel generates different delays for pre-emphasis of each channel of the array antenna for generating delays under different receiving angles, the difference value of the pre-emphasis delay lines between adjacent channels is equal to the delay interval introduced between adjacent channels under the maximum scanning angle of the antenna array, and the signs are opposite, so that single positive angle or negative angle receiving is realized when the received light beams of positive and negative angles of the array antenna form a beam.

Further, the number n of optical splitter channels is adjusted according to the number of actual beam forming requirements.

Furthermore, the dispersive optical fiber is used for forming optical beams, each channel dispersive optical fiber forms one optical beam, and a positive dispersion coefficient optical fiber or a negative dispersion coefficient optical fiber is adopted according to requirements.

Compared with the prior art, the invention has the following remarkable advantages: (1) compared with the realization mode based on the wavelength scanning of the tunable laser, the realization method does not need the tunable laser with high performance, has relatively low cost, and the optical beam forming is a single-channel beam forming system, and has relatively low control precision on the length of the optical fiber; (2) when the positive and negative angle receiving is realized, two optical fibers with positive and negative dispersion coefficients are not needed to be adopted at the same time, the forming performance of the optical beam is kept, the system structure is simplified, the system loss, the volume, the weight and the like are reduced, and the comprehensive efficiency is improved.

Drawings

FIG. 1 is a block diagram of an optical beam forming pre-emphasis apparatus based on fiber dispersion according to the present invention.

Fig. 2 is a schematic diagram of the scanning angle of the antenna array of ± 30 ° in the embodiment of the present invention.

Fig. 3 is a graph of channel delay for each scan angle of the antenna array before pre-emphasis delay in an embodiment of the present invention.

Fig. 4 is a graph of the delay of each channel of the antenna array and the corresponding scan angle after the pre-emphasis delay in the embodiment of the present invention.

Fig. 5 is a plot of the antenna wavefront scan direction before pre-emphasis delay in an embodiment of the invention.

Fig. 6 is a diagram of the scanning direction of the antenna wavefront after pre-emphasis delay in an embodiment of the invention.

Detailed Description

The invention is described in further detail below with reference to the figures and specific embodiments.

With reference to fig. 1, the optical beam forming pre-emphasis apparatus based on optical fiber dispersion of the present invention includes an antenna array channel, a laser, an electro-optical modulator, a pre-emphasis delay line, a wavelength division multiplexer, an optical fiber amplifier, an optical splitter, a dispersion optical fiber, and a photodetector;

microwave signals received by each channel on an antenna array surface are modulated onto optical carriers with corresponding wavelengths generated by a laser through an electro-optical modulator, then enter a wavelength division multiplexer through pre-emphasis delay lines, m channels of the antenna array surface correspond to m optical carriers with different wavelengths, the pre-emphasis delay lines of each channel generate different delays for pre-emphasis of the channels of the array surface antenna for generating delays under different receiving angles, the wavelength division multiplexer multiplexes the modulated and pre-emphasis delayed optical signals to an optical fiber for transmission, the optical signals are amplified through an optical fiber amplifier and then pass through an optical splitter to distribute the equal power of the multiplexed multi-wavelength optical signals to n paths, different delay amounts are realized through dispersive optical fibers of each path to form different beam directions, and finally, the photoelectric detector realizes the conversion of the optical signals to the microwave signals.

Because each channel signal is pre-emphasized by the pre-emphasis delay line at the front end before entering the dispersion optical fiber, the beam receiving angle formed by the dispersion optical fiber at the rear end generates certain deflection relative to the array antenna, so that the single positive angle or negative angle receiving is realized when the received light beam of the positive angle or the negative angle of the array antenna is formed, at the moment, the dispersion optical fiber only needs to realize the positive angle or negative angle receiving, and the dispersion optical fiber of the positive dispersion coefficient and the negative dispersion coefficient is not needed when the light beam is formed.

Furthermore, the number m of the channels of the antenna array surface can be adjusted according to the actual situation, and the number of the corresponding lasers with different wavelengths, the number of the electro-optical modulators and the number of the channels of the wavelength division multiplexer are consistent with the number of the corresponding lasers with different wavelengths, the number of the electro-optical modulators and the number of the channels of the wavelength division multiplexer.

Furthermore, the pre-emphasis delay line is positioned between the electro-optical modulator and the wavelength division multiplexer, the pre-emphasis delay line can be an optical fiber delay line with a fixed length or an adjustable optical fiber delay line, the pre-emphasis delay line of each channel generates different delays and is used for pre-emphasis of delay of each channel of the array plane antenna under different receiving angles, the difference value of the pre-emphasis delay lines between adjacent channels is equal to the delay interval introduced between adjacent channels under the maximum scanning angle of the antenna array plane, the signs are opposite, and single positive angle or negative angle receiving is realized when the received light beams of positive and negative angles of the array plane antenna form.

Further, the number n of optical splitter channels can be adjusted according to the number of actual beam forming requirements.

Furthermore, the dispersive optical fiber is used for forming optical beams, each channel dispersive optical fiber can form one optical beam, and a positive dispersion coefficient optical fiber or a negative dispersion coefficient optical fiber can be adopted according to design requirements.

The invention has the advantages of simple structure, small volume, light weight, low cost, low system energy consumption and high comprehensive efficiency. Compared with the realization mode based on the wavelength scanning of the tunable laser, the realization method does not need the tunable laser with high performance, has relatively low cost, and the optical beam forming is a single-channel beam forming system, and has relatively low control precision on the length of the optical fiber; compared with the original implementation mode based on the multi-wavelength laser source array, the optical fiber with two positive and negative dispersion coefficients is not needed to be adopted simultaneously when the positive and negative angle receiving is realized, the system structure is simplified while the forming performance of the optical beam is kept, the system loss, the volume, the weight and the like are reduced, and the comprehensive efficiency is improved.

The invention is described in further detail below with reference to the figures and the embodiments.

Examples

Fig. 1 is a block diagram of an optical beam forming pre-emphasis apparatus based on fiber dispersion according to this embodiment, and the structure takes an antenna array as 16 channels and 8 optical beam forming channels as an example. As shown in fig. 1, this embodiment sets the antenna array channels (channel 1, channel 2, …, channel 16, respectively), lasers (wavelength λ 1, λ 2, …, λ 16, respectively), electro-optic modulators, pre-emphasis delay lines (pre-emphasis delay line 1, pre-emphasis delay line 2, …, pre-emphasis delay line 16, respectively), wavelength division multiplexers, fiber amplifiers, optical splitters, dispersive fibers, and photodetectors.

Microwave signals received by each channel on an antenna array surface are modulated onto optical carriers with corresponding wavelengths generated by a laser through an electro-optical modulator, then enter a wavelength division multiplexer through a pre-emphasis delay line, 16 channels of the antenna array surface respectively correspond to 16 optical carriers with different wavelengths, the pre-emphasis delay line of each channel is used for generating different delays and is used for generating time-delayed pre-emphasis of each channel of the array surface antenna under different receiving angles, the wavelength division multiplexer multiplexes the modulated and pre-emphasis delayed optical signals to an optical fiber for transmission, the optical signals are amplified through an erbium-doped fiber amplifier (EDFA) and then pass through an optical splitter, the multiplexed multi-wavelength optical signals are distributed to 9 paths with equal power, different delay amounts are realized through dispersion optical fibers of each path, different beam directions are formed, and finally, the conversion from the optical signals to the microwave signals is realized through a photoelectric detector. Because each channel signal is pre-emphasized by the pre-emphasis delay line at the front end before entering the dispersion optical fiber, the beam receiving angle formed by the dispersion optical fiber at the rear end is deflected to a certain degree relative to the array antenna, so that the single positive angle or negative angle receiving is realized when the positive and negative angles of the received light beam of the array antenna are formed, at the moment, the dispersion optical fiber only needs to realize the positive angle or negative angle receiving, and the dispersion optical fiber of the positive and negative dispersion coefficient is not needed when the light beam is formed.

Specific calculation examples are as follows:

with reference to fig. 2, it is assumed that the distance d between the front antenna channels is 8.33mm, the reception angle of the front antenna is-30 ° to-30 °, and the two reception angles of-30 ° and 30 ° are taken as examples for calculation.

(1) The receiving angle is-30 °

Setting the delay difference between adjacent channels of the antenna array at the time as tau

Where c is the speed of light in vacuum. Channel 2 is now delayed by τ with respect to channel 1, channel 3 is delayed by τ with respect to channel 2, and so on for other adjacent channels. After the microwave signal is modulated to an optical carrier by an electro-optical modulator, the microwave signal is subjected to delay pre-emphasis by a pre-emphasis delay line, and the delay interval tau of the pre-emphasis delay line₁Is arranged as

The delay difference introduced by the pre-emphasis delay line between adjacent channels is now τ for channel 2 relative to channel 1₁Channel 3 is delayed by tau with respect to channel 2₁And the other adjacent channels are analogized. After the optical signal passes through the pre-emphasis delay line, the delay difference between every two adjacent channels is tau₂The sum of the delay introduced for the antenna array spacing and the delay introduced by the pre-emphasis delay line, i.e.

Let the delay difference between adjacent channels be tau₂The receiving angle of time is theta_xAnd the formula for calculating the delay difference between adjacent channels can be obtained as follows:

at this time theta_xAt 0 deg., i.e. when the beam pointing corresponds to 0 deg., the actual antenna array reception angle is-30 deg..

Optical signals of each channel are multiplexed by wavelength divisionThe rear end of the optical splitter is composed of dispersion optical fibers with different lengths. The delay tau introduced by dispersive optical fiber between adjacent channels can be known from the principle of dispersive delay₃Is composed of

τ₃＝D·Δλ·L

D is the dispersion coefficient of the dispersive fiber, Delta lambda is the laser wavelength interval between adjacent channels (wavelength lambda 1 is more than lambda 2 and less than … and less than lambda 16, Delta lambda is more than 0), and L is the length of the dispersive fiber.

When forming optical beams, requires

τ₃＝-τ₂

I.e. the delay between adjacent channels introduced by the dispersive fiber compensates for the sum of the delay introduced between the channels of the antenna array and the delay introduced by the pre-emphasis delay line.

When the delay difference between adjacent channels entering the dispersive fiber is

τ₃＝-τ₂＝0

Therefore, when D is 0, the zero-dispersion-coefficient fiber can form a beam pointing to 0 ° for reception.

(2) The receiving angle is 30 DEG

Let the delay difference between adjacent channels of the antenna array be τ'

Where c is the speed of light in vacuum. Channel 2 is now delayed by τ with respect to channel 1, channel 3 is delayed by τ with respect to channel 2, and so on for other adjacent channels. After the microwave signal is modulated to an optical carrier by an electro-optical modulator, the microwave signal is subjected to delay pre-emphasis by a pre-emphasis delay line, and the delay interval tau of the pre-emphasis delay line₁Is composed of

The delay difference introduced by the pre-emphasis delay line between adjacent channels is now τ for channel 2 relative to channel 1₁Channel 3 is delayed by tau with respect to channel 2₁And the other adjacent channels are analogized. After the optical signal passes through the pre-emphasis delay line, the delay difference between adjacent channels is tau'₂The sum of the delay introduced for the antenna array spacing and the delay introduced by the pre-emphasis delay line, i.e.

Let the delay difference between adjacent channels be τ'₂Reception angle of (2) 'theta'_xAnd the formula for calculating the delay difference between adjacent channels can be obtained as follows:

at this time of'_xAt 90 deg., i.e. when the beam is pointed corresponding to 90 deg., the actual antenna front reception angle is 30 deg..

In this case, the beam formation via the dispersive optical fiber is required

τ₃＝-τ′₂

The principle of time delay of dispersive optical fiber shows that the length of the optical fiber requiring negative dispersion coefficient (D < 0) is as follows:

other array surface receiving angles can be obtained by the same method, the calculation shows that the negative receiving angle of the antenna array surface can be converted into the beam direction equivalent to the angle from 0 degree to positive through the pre-emphasis delay technology, and when the rear end adopts the dispersive optical fiber beam forming, except for the zero-dispersion optical fiber adopted in the 0 degree direction, only the negative-dispersion optical fiber is adopted, and two optical fibers with positive and negative dispersion coefficients are not required to be adopted at the same time.

Fig. 3 is a graph of channel delay for each scanning angle of the antenna array surface before pre-emphasis delay, fig. 4 is a graph of channel delay and corresponding scanning angle for the antenna array surface after pre-emphasis delay, fig. 5 is a graph of scanning direction of the antenna array surface before pre-emphasis delay, and fig. 6 is a graph of scanning direction of the antenna array surface after pre-emphasis delay. As can be seen from fig. 3 to 6, the device of the present invention does not need to use two optical fibers with positive and negative dispersion coefficients when realizing positive and negative angle reception, and simplifies the system structure, reduces the system loss, volume and weight, and improves the comprehensive efficiency while maintaining the performance of forming the optical beam.