CN110177067A - It is suitble to the orbital angular momentum index modulation Transmission system and method for long distance transmission - Google Patents

It is suitble to the orbital angular momentum index modulation Transmission system and method for long distance transmission Download PDF

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CN110177067A
CN110177067A CN201910411329.XA CN201910411329A CN110177067A CN 110177067 A CN110177067 A CN 110177067A CN 201910411329 A CN201910411329 A CN 201910411329A CN 110177067 A CN110177067 A CN 110177067A
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oam
antenna
index
phase
bit information
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CN110177067B (en
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张超
赵宇飞
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Tsinghua University
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Tsinghua University
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0008—Modulated-carrier systems arrangements for allowing a transmitter or receiver to use more than one type of modulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
    • H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
    • H04L27/345—Modifications of the signal space to allow the transmission of additional information
    • H04L27/3461—Modifications of the signal space to allow the transmission of additional information in order to transmit a subchannel
    • H04L27/3483—Modifications of the signal space to allow the transmission of additional information in order to transmit a subchannel using a modulation of the constellation points

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Radio Transmission System (AREA)
  • Variable-Direction Aerials And Aerial Arrays (AREA)

Abstract

The invention discloses a kind of orbital angular momentum index modulation Transmission system of suitable long distance transmission and methods.In transmitting terminal, which is combined selection using the orbital angular momentum electromagnetic of different mode, forms different mode combination, user's bit information is mutually modulated with width respectively and is transmitted with orbital angular momentum electromagnetic mode combinations index modulation；In receiving end, on fractional phase face, which group orbital angular momentum mode combinations had received by the method judgement of phase difference index mapping, to complete electromagnetic wave orbital angular momentum mode combinations to the mapping between transmitted user's bit, the method that width mutually demodulates simultaneously restores another part bit information, combines with the bit information that phase difference indexes mapping recovery and finally recovers raw information.The spectrum efficiency of communication system not only can be improved in the present invention, while the orbital angular momentum electromagnetic long range fractional phase face reception of reliability, low complex degree may be implemented.

Description

It is suitble to the orbital angular momentum index modulation Transmission system and method for long distance transmission
Technical field
The present invention relates to radio magnetic wave field of communication technology, in particular to a kind of track angular motion of suitable long distance transmission Measure index modulation Transmission system and method.
Background technique
Electromagnetic wave orbital angular momentum (Orbital Angular Momentum, OAM) is electromagnetic wave build-in attribute and area Another important physical amount not except traditional wave frequency, electric field strength etc..Electromagnetic wave with OAM is claimed again For " vortex electromagnetic wave ", spiral distribution is presented in phase face and direction of propagation out of plumb.The conventional plane wave phase generallyd use Face is vertical with the direction of propagation, therefore does not have OAM.Electromagnetic wave and conventional plane electromagnetic wave with OAM have significant difference, It allows people that can remove exploitation electromagnetic wave from a new dimension, carries out information transmission and target acquisition field in application electromagnetic wave All there is great value.
In recent years, OAM is in the research in low-frequency electromagnetic wave field also increasingly by the extensive concern of domestic and foreign scholars.2007 Year, B, Thid é et al. demonstrate low-frequency electromagnetic wave (frequency is lower than 1GHz) by the numerical simulation of aerial array and can equally produce Raw OAM.Analyzing existing electromagnetic wave OAM transmission mode can find: with the increase of OAM number, OAM electromagnetic wave divergent angle increases, from The electromagnetic wave beam that first dual-mode antenna issues is at cone cell.Transmission range is longer, and wave beam more dissipates.2012, F, Tamburini Et al. for the first time realize 442m long range OAM point-to-point transmission experiment, it was demonstrated that OAM have long range multiplexing transmission improve communication The potentiality of system spectral efficiency.Its method of reseptance used is two o'clock difference, it may be assumed that phase gradient method.But phase gradient method needs Two receiving points are wanted to be respectively positioned on the same circumference perpendicular to propagation axis, and the center of circle and propagation overlapping of axles.Phase is misaligned will Reduce the correctness of OAM mode detection.Also, detection accuracy is reduced with the reduction of the subtended angle between two receiving antennas, it may be assumed that when two When receiving antenna spacing is fixed, detection accuracy is reduced with the increase of transmission range.In December, 2016, Tsinghua University's aviation aerospace Electronic system laboratory completes 27.5 kilometers of long distance transmission experiments, and 2018, which further expanded transmission range 172 kilometers have been opened up, and has finally realized four tunnels, four mode OAM multiplexing transmission.
Summary forefathers' the study found that the very few nothing of research achievement in terms of microwave band long range OAM electromagnetic transmission It is several.OAM wave beam is inverted cone shape, and distance is remoter, and cyclic annular phase face is bigger, and coaxial all phase face reception is more difficult, such as more than 100 km transmissions, then phase face diameter even can achieve several kilometers.At this point, fractional phase can only be used in practical projects Face method of reseptance, and the reception of fractional phase face cannot obtain the orthogonal bring of OAM dimension significantly capacity gain, be only capable of obtaining The little nonopiate OAM of one capacity is multiplexed bring extra channel.It is passed therefore, it is also desirable to further improve OAM signal Defeated modulation and detection method.In addition, " long range " in " suitable long distance transmission " described in the present invention refers generally to be greater than 100 meters of linear distance, long distance transmission are suitable for long-distance radio communication, mobile relay, microwave relay, vehicle-carrying communication, sky Ground communication, satellite communication and space communication etc..
Summary of the invention
The presence of the OAM channel dimension new as one can construct in conjunction with index modulation and be suitble to long distance transmission part The received new types of data chain of phase face.Due to combining index modulation, it can be further increased on the basis of width is mutually modulated and be The spectrum efficiency of system, in addition in receiving end, due to can only OAM Information in receiving portion phase face, it is therefore desirable to establish and be suitble to The received associated detecting method in fractional phase face distinguishes the bit map that OAM bit map is mutually modulated with width.To reach above-mentioned mesh , the invention proposes a kind of electromagnetic wave orbital angular momentum index modulation Transmission systems of suitable long distance transmission, including signal Subsystem, transmitting antenna subsystem, fractional phase face receiving subsystem occurs, wherein
Subsystem occurs for signal
Combined coding module: the raw information coding that user is sent becomes bit information；
Bit decomposing module: bit information is resolved into two parts, a part input width mutually modulates mapping block, another portion Divide input OAM index modulation mapping block；
Width mutually modulates mapping block: not using any bit information by input in constellation modulation system and each representative Width phase constellation point with amplitude and phase establishes one-to-one relationship；
OAM index modulation mapping block: being provided with the look-up table comprising different OAM mode combinations, by bit information with it is right The OAM mode combinations of transmitting should be selected to establish mapping relations one by one；
Virtual arbitrary waveform generator module: width mutually modulates mapping block and the information of OAM index modulation mapping block output is logical It crosses waveform generator and synthesizes joint transmitting symbol；
The joint transmitting symbol that transmitting antenna subsystem is used to generate waveform generator is by up-conversion and power amplification After be fed to different OAM and occur on a period of time, multichannel OAM combination transmitting signal is formed, by reflecting surface and lens to energy centralization It transmits in free space afterwards；
Fractional phase face receiving subsystem includes:
Receiving antenna array: being converted into radiofrequency signal for the electromagnetic wave transmitted in free space, and radio frequency link is by the radio frequency Signal down-converts to intermediate-freuqncy signal, and fractional phase face refers to that the partial region of same phase face is arranged in receiving antenna array；
Prefilter: intermediate-freuqncy signal exports two-way after passing through prefilter, all the way input phase difference index mapping mould Block, another way input width phase modulation detection module；
Phase difference indexes mapping block: by phase difference between receiving antenna on fractional phase face, from different OAM mode combinations Between establish mapping relations one by one, thus by bit information be mapped to index domain；
Index domain filter: the signal after indexing mapping block building mapping relations by phase difference passes through the filtering of index domain After device filtering output, different spectral lines, and the corresponding spectral line of combination of each OAM mode are formed in index domain；
Width phase modulation detection module: receiving the filtered carrier signal of prefilter, so that width phase constellation point is demodulated, And bit information corresponding with width phase constellation point is obtained in turn；
OAM mode combinations index modulation detection module: each spectral line in detection identification index domain, according to the lookup Table, detection determine the bit information transmitted by OAM mode combinations；
Planisphere combinatorial mapping module: the bit for the width phase constellation point output that width phase modulation detection module is detected is believed The bit information that breath is demodulated with OAM mode combinations index modulation detection module will according to the bit exploded relationship of transmitting terminal Two parts bit information reconfigures, to form the corresponding bit information of the complete raw information；
Combined decoding module: for receiving the original user bit information of planisphere combinatorial mapping module output to restore The raw information of user's transmission.
Preferably, transmitting antenna subsystem includes the antenna feed and its radio frequency link for generating different OAM modes, rf chain Road includes power splitter, frequency mixer, amplifier and radio frequency original part, and antenna feed is the form of antenna element or resonant cavity, antenna Feed is the form of antenna element or resonant cavity；
Reflecting surface is the paraboloid with or without Meta Materials；
Lens are convex lens or Meta Materials lens；Receiving antenna includes frequency mixer, amplifier, power splitter and rf chain Road, receiving antenna are aerial array, resonant cavity or the sensor that detection is received for OAM.
Preferably, constellation modulation system includes BPSK, QPSK, QAM.
Preferably, the electromagnetic wave includes one of light wave, microwave, millimeter wave and THz wave or a variety of.
Preferably, the antenna feed and/or the receiving antenna are electromagnetic horn, parabola antenna, card plug brother's human relations day One of line, paster antenna, array antenna.
Preferably, the equipment for generating different mode OAM electromagnetic wave is spiral phase plate, specific reflection surface antenna, specific feedback One of source antenna, phased array antenna, spatial light modulator, diffraction grating and Meta Materials are a variety of.
Preferably, the raw information coding of user is become into the bit information to be transmitted；
Bit information is decomposed into two parts, and a part input width mutually modulates mapping block, and mapping becomes the width to be transmitted Phase constellation point, another part enter OAM index modulation mapping block, establish one by one by searching for table from different OAM mode combinations Mapping relations；
Two parts information synthesizes the IF carrier to be transmitted, the OAM of control antenna feed transmitting different mode combination In free space transmission after electromagnetic wave, emitted face and lens energy centralization；
Receiving antenna receives the electromagnetic wave in free space on fractional phase face, is translated into intermediate frequency letter Number, bit information corresponding to width phase modulation detection module detection output width phase constellation point, intermediate-freuqncy signal is indexed by phase difference Different spectral lines is formed in index domain after mapping block and index domain filter, by judging that different spectral lines occur in index domain Position, and then demodulate the bit information that is transmitted of OAM mode combinations, the merging of two parts bit information recovers the original letter Breath.
Preferably, the big bit information of the small OAM mode combinations configuration Hamming distance of difference is transmitted, wherein OAM mould Small the distance between the spectral line for referring to that OAM mode combinations are converted in index domain of the difference of formula combination is less than preset apart from threshold Value.
Preferably, transmitting antenna subsystem generates NtThe OAM electromagnetic wave of kind mode, receiving antenna array includes NrRoot antenna, connects Width when receiving antenna array transmission mutually modulates selection M-PSK, and the expression of various constellations point is denoted as d (m), wherein m ∈ [1,2 ..., M], M indicates m-th constellation point, and transmitting antenna subsystem common property is rawKind OAM mode combinations mode, it is corresponding The joint transmitting symbol of the combination of kind bit symbol, each OAM combination is expressed asEllipsis in formula indicates to send arbitrary 0 or 1 bit letter in sequence Breath, 1 × NtIndicate X(k)It is 1 row NtThe vector of column, wherein k ∈ [1,2 ..., K], indicates the kth group OAM mode combinations rope of activation Draw, the position of element 1 means that position of the OAM mode to be transmitted in combination, the group that thus receiving antenna array receives Transmission signal is closed to be simplified shown as:
Wherein,Indicate the power partition coefficient of each mode combinations, X(k)It is joint transmitting symbol,When indicating the mode combinations k of transmission OAM index modulation, the activation OAM mode of transmitting antenna subsystem The channel matrix that the channel coefficients transmitted between receiving antenna array are constituted, z are the white Gaussian noise matrixes that mean value is zero.
Preferably, it is every OAM mode weights assigned coefficient, establishes and optimize equation, in the feelings that total transmission power is constant Under condition, power discrete is passed through by meter by the power distribution that AWG adjusts all OAM modes for participating in superposition in different mode The mode of calculation machine search spread, determines optimal weighting coefficients, to realize that all OAM integrated modes of adjustment are corresponding in index domain Spectral line between Euclidean distance it is equal.
Electromagnetic wave orbital angular momentum index modulation long haul transmission system of the invention and transmission method, this transmission method is not But the OAM electromagnetic transmission and reception being suitable within 1 kilometer, and it is also applied for 1 kilometer or more of long range OAM electromagnetic wave Transmission and reception.Since Angle of beam divergence limits, with the increase of distance, OAM helical phase face constantly expands, kilometer rank Transmission can not receive simultaneously entire OAM helical phase face, and when fractional phase face receives, can bring between different mode Crosstalk, the orthogonality between mode is destroyed, that is, freedom degree is reduced with the reduction in receiving phase face.Therefore in length When Distance Transmission, OAM multiplex mode can be degenerated to the mode of low degree-of-freedom transmission, and the present invention is new free using OAM as one The characteristic of degree forms index modulation in transmitting terminal using the combination of different mode, expands OAM communication from the angle of index modulation The spectrum efficiency of system.Because OAM is the new dimension for being different from other physical quantitys of electromagnetic wave, after index modulation simultaneously The transmission of width phase modulated signal is not influenced, therefore can mutually modulate star with width with simultaneous transmission OAM index modulation information in transmitting terminal Seat, to realize purpose of the OAM over long distances with spectral efficient transmission.
Detailed description of the invention
By the way that embodiment is described in conjunction with following accompanying drawings, features described above of the invention and technological merit will become More understands and be readily appreciated that.
Fig. 1 is that a kind of electromagnetic wave orbital angular momentum index modulation of suitable long distance transmission of the embodiment of the present invention transmits system The overall structure diagram of system；
Fig. 2 is that the bit information mapping of the embodiment of the present invention becomes the realization side of OAM mode combinations and width phase modulation constellation Formula schematic diagram；
Fig. 3 is vector superposed principle signal of the different OAM integrated mode signals of the embodiment of the present invention on receiving antenna Figure；
Fig. 4 is the OAM index modulation system of the embodiment of the present invention and the bit error rate of mimo system and High Order Modulation System Property comparison schematic diagram.
Specific embodiment
Electromagnetic wave orbital angular momentum index modulation long distance transmission of the present invention system described below with reference to the accompanying drawings The embodiment of system and transmission method.It will also be recognized by those skilled in the art that without departing from the spirit and scope of the present invention In the case of, described embodiment can be modified with a variety of different modes or combinations thereof.Therefore, attached drawing and description exist Substantially be it is illustrative, be not intended to limit the scope of the claims.In addition, in the present specification, attached drawing is not pressed Ratio is drawn, and identical appended drawing reference indicates identical part.
It is said in principle, OAM can use specific OAM sensor, or be received using antenna.It is received using antenna It needs to other domains indirectly to be measured OAM this dimension map, such as uses antenna array when the coaxial reception in all phase face OAM is mapped to airspace, the change of OAM can cause the change of spatially electromagnetic wave phase plane distribution, so as to use antenna array It measures the spatially electromagnetic wave phase differences of different location and then speculates the variation of OAM, for this angle, OAM can be recognized It is a kind of OAM in fact to space with antenna array measurement OAM for a kind of special subset for being MIMO, and from physical essence The mapping relations in domain.Further analysis, other than the mapping to airspace, OAM, which can also be formed other domains, to be mapped, such as logical The variation of OAM, has actually been mapped to time domain, and then be mapped to frequency domain by frequency spectrograph by the method measurement OAM for crossing rotation, The electromagnetic wave of different OAM modes is under the mapping of rotation function relationship, the corresponding several different spectral lines become in frequency domain.And it is special The method of virtual interpolation (Virtual Rotating Antenna, VRA) disclosed in benefit number 2016109163094 can pass through The setting of prefilter, building index domain (herein, the first frequency domain refer to commonly receiving signal pass through Fourier transformation it The frequency domain being mapped to afterwards, index domain refers to the homogenous frequency signal received, because containing different OAM modes, by virtual interpolation After rotation process, then Fourier transformation is carried out, the spectral line that original homogenous frequency signal can be different with different OAM pattern formations, This is called index domain), different spectral lines and different OAM electromagnetic waves equally can be constructed in index domain by virtual interpolation algorithm Mapping relations one by one.
Therefore, by analyze above it is recognised that OAM this dimension can by difference can mapping relations be mapped to difference Transform domain measure, and the set that these all mapping functions are constituted is exactly new index domain.Construct OAM index domain Method has very much, and different methods is actually corresponding to be different mapped function relation, and identical index domain even can also It is obtained with by different mapping functions, so as to form complicated variation space.OAM is mapped to the mapping side in index domain Method is diversified, therefore the index domain of OAM can also be very big, this provides very big research just for OAM index modulation Space.Illustrate the long range index modulation Transmission system of electromagnetic wave OAM of the invention below.
As shown in Figure 1, a kind of electromagnetic wave orbital angular momentum index modulation Transmission system 10 of suitable long distance transmission includes Subsystem 100, transmitting antenna subsystem 200 and signal receiving subsystem 300 occur for signal.Wherein, subsystem 100 occurs for signal Including combined coding module 101, bit decomposing module 102, width mutually modulate mapping block 103, OAM index modulation mapping block 104 and virtual arbitrary waveform generator module 105；Transmitting antenna subsystem 200 includes antenna feed module 201 and radio frequency link module 202；Fractional phase face receiving subsystem 300 includes receiving antenna array 301, prefilter 302, phase difference index mapping mould Block 303, index domain filter 304, width phase modulation detection module 305, OAM mode combinations index modulation detection module 306, constellation Figure combinatorial mapping module 307 and combined decoding module 308.Illustrate the composition of each subsystem separately below.
1. subsystem occurs for signal, including
(1) the raw information coding of user combined coding module 101: is become into the bit information to be transmitted.
(2) bit decomposing module 102: the corresponding bit information data of user's raw information are decomposed, are divided into two Point, a part input width mutually modulates mapping block 103, and width mutually modulates mapping block 103 using the electromagnetism of different amplitude and phase Wave characterizes the bit information information of input, i.e. the width phase constellation point of bit information information amplitude and phase different from representing formed Mapping relations；Another part inputs OAM index modulation mapping block 104, forms mapping relations from the combination of different OAM modes；
(3) width mutually modulates mapping block 103: using BPSK (binary phase shift keying.It is that analog signal is converted into data One of conversion regime of value), QPSK (quadrature phase shift keying), in a series of constellation modulation systems such as QAM (quadrature amplitude modulation) The bit information inputted above and each width phase constellation point are established one-to-one relationship by any method；
(4) OAM index modulation mapping block 104: generating the syntagmatic of various OAM modes, forms look-up table, will input User's bit information it is corresponding with the OAM mode combinations that corresponding selection emits, different use are transmitted using different integrated mode Family bit information；
(5) virtual arbitrary waveform generator module 105: the constellation point that width is mutually modulated to mapping selects different OAM modes to carry out group It closes, to form compound joint transmitting symbol.Also, also while utilizing the range-adjusting function inside arbitrary waveform generator Can, transmission power is distributed by programming freedom, so that the transimission power of each group of joint transmitting symbol is equal, is further controlled Transmitting antenna subsystem.
2. transmitting antenna subsystem
(1) antenna feed 201: the OAM for being provided with multiple modes generates antenna element, to generate multiple modes OAM can use the form of such as resonant cavity or aerial array, but be not limited to these types of typical OAM producing method, may be used also To adjust annular radii according to the OAM electromagnetic wave of different mode, so that the OAM Angle of beam divergence of different mode is consistent, hair Energy is penetrated to concentrate in the same annulus phase face；
(2) it radio frequency link module 202: including power splitter, frequency mixer, filter and signal power amplifier submodule, uses Emit symbol in the compound joint for generating arbitrary waveform generator, is fed to difference after up-conversion and power amplification OAM occurred on a period of time, formed the road n OAM combination transmitting signal, after reflecting surface and lens are to energy centralization in free space Transmission.
3. fractional phase face receiving subsystem
(1) receiving antenna array 301: the electromagnetic wave transmitted in free space is converted into radiofrequency signal, i.e., in transmission line Guided electromagnetic wave, the radiofrequency signal down-converts to intermediate-freuqncy signal by radio frequency link；
(2) prefilter 302: intermediate-freuqncy signal enters prefilter 302, and prefilter 302 can use band logical Filter, filters out out-of-band interference information, frequency point required for obtaining it is modulated after carrier signal, intermediate-freuqncy signal passes through preposition filter Two-way is exported after wave device, inputs virtual interpolation rotary module all the way, and another way inputs width phase modulation detection module；
(3) phase difference indexes mapping block 303: it can be using virtual interior disclosed in the patent No. 2016109163094 Slotting method, the OAM electromagnetic wave on the fractional phase face that antenna is received carry out virtual interpolation rotation process, transform to index Domain, the composite signal of same frequency point can become different spectral lines, such as Fig. 4 in the expansion of index domain originally after Fourier transformation Shown, different spectral lines correspond to the integrated mode of different OAM, by phase difference different between receiving antenna and different OAM modal sets Build vertical mapping relations one by one jointly；
(4) it indexes domain filter 304: after the signal after virtual interpolation is exported by index domain filter filtering, indexing Domain forms different spectral lines, and the corresponding spectral line of combination of each OAM mode, forms the relationship mapped one by one；
(5) width phase modulation detection module 305: the filtered carrier signal of prefilter is received, for demodulating width phase Modulation constellation points, such as BPSK, QPSK, QAM；
(6) OAM mode combinations index modulation detection module 306: each spectral line in detection identification index domain, according to one The look-up table of one mapping, detection determine the user's bit information transmitted by OAM index modulation；
(7) planisphere combinatorial mapping module 307: the width phase constellation point output that width phase modulation detection module is detected The information that information and OAM mode combinations index modulation detection module demodulate, according to the bit exploded relationship of transmitting terminal, by two Partial bit information reconfigures, to form the complete raw information.
(8) combined decoding module 308: for receive planisphere combinatorial mapping module output original user bit information from And restore the initial data of user's transmission.
The signal processing workflow of the electromagnetic wave orbital angular momentum index modulation Transmission system of entire suitable long distance transmission Journey is as follows: as shown in Figure 1, the raw information coding of user is become the bit information to be transmitted, bit information information is passed through Two parts are decomposed into after bit decomposing module 102, a part input width mutually modulates mapping block 103, and mapping becomes to be transmitted Width phase constellation point, another part enters OAM index modulation mapping block 104, builds jointly by searching for table from different OAM modal sets Vertical mapping relations one by one, two parts information is combined into the IF carrier to be transmitted by arbitrary waveform generator 105 later, After the mixing amplification of radio frequency link 202, control antenna feed 201 emits the OAM electromagnetic wave of various combination mode, emitted face With after lens energy centralization in free space transmission.Receiving end antenna array is arranged in OAM ring part phase face, passes through reception Aerial array 301 receives the electromagnetic wave in free space, the guided electromagnetic wave being translated into transmission line, and passes through Received bandpass signal is wanted in output after prefilter, the method remerged using separation detection, width phase modulation detection module 305 are responsible for bit information corresponding to detection output width phase constellation point, and signal indexes mapping block 303 and rope by phase difference Draw and form different spectral lines in index domain after domain filter module 304, OAM mode combinations index modulation detection module 306 is used for The integrated mode for detecting different OAM recovers transmitted bit information, final two parts bit data by Map Searching table one by one The original bit data of user is exported after merging by planisphere combinatorial mapping module 307.Combined decoding module 308 receives constellation The original user bit information that figure combinatorial mapping module 307 exports, to restore the initial data of user's transmission.
In conclusion a kind of electromagnetic wave orbital angular momentum index modulation Transmission system of suitable long distance transmission of the invention The OAM Information transmission that can be realized long range spectral efficient, since receiving portion helical phase face can only be sampled in receiving end Information, cannot keep orthogonality between the OAM signal of each mode, if be bound to using the multiplexing transmission mode of transmission It will cause mutual crosstalk between each path channels, in turn result in the reduction of channel capacity.And it innovatively proposes to adopt in the present invention It is combined to form index with the OAM of different mode, and establishes mapping relations one by one with user's bit information, mutually modulated in width in this way On the basis of, since the introducing of the new dimension of OAM further improves system under conditions of not increasing original system link circuit resource The spectrum efficiency of transmission.In receiving end, the present invention using prefilter 302 and index domain filter 304 width mutually modulated with OAM index modulation two parts mapping signal separation detection, and in such a way that virtual interpolation rotates, it is realized on fractional phase face Accurate detection to different OAM integrated modes, had both reduced the complexity of index modulation maximum likelihood joint-detection, simultaneously in this way The reliability for improving information transmission demodulation again can be realized system long range, narrow bandwidth, low complex degree, high reliability, quick Received transmission requirement.
In addition, a kind of electromagnetic wave orbital angular momentum index modulation Transmission system of suitable long distance transmission according to the present invention There can also be following additional technical characteristic:
In one alternate embodiment, the electromagnetic wave includes one of light wave, microwave, millimeter wave and THz wave Or it is a variety of.
In one alternate embodiment, the antenna in the transmitting antenna array and/or the receiving antenna array is loudspeaker One of antenna, parabola antenna, card plug brother's human relations antenna, paster antenna, array antenna.
Further, be suitble to the transmitting antenna that transmits at a distance include can produce different OAM modes antenna feed and Its radio frequency link, radio frequency link include that power splitter, frequency mixer, amplifier and radio frequency original part, antenna feed can be antenna element Or the form of resonant cavity, but it is not limited to these forms.
In one alternate embodiment, it is suitable for the remote received antenna in fractional phase face, including frequency mixer, amplification Device, power splitter and other necessary radio frequency links, receiving antenna can be aerial array, resonant cavity or other be used for OAM Receive the sensor of detection.
In one alternate embodiment, the plus lens can be one in ordinary optical lens or Meta Materials lens Kind is a variety of, and lens can select to arrange in pairs or groups according to actual needs with paraboloid.
In one alternate embodiment, the reflecting surface can be in ordinary optical reflecting surface or Meta Materials reflecting surface It is one or more, for converging electromagnetic wave.
In one alternate embodiment, the producing method of different mode OAM electromagnetic wave is spiral phase plate, specific reflection face One of antenna, specific feed antenna, phased array antenna, spatial light modulator, diffraction grating and Meta Materials are a variety of.
In one alternate embodiment, can be according to the combination of different OAM modes, different OAM index modulations are corresponding Different coding transmission symbols can further increase system transmission by the Hamming distance joint index modulation between coding Reliability.Specifically, the various combination mode of OAM mode is when indexing domain demapping, the distance between corresponding difference spectral line It is not consistent, therefore increased in the combined coding module 101 of transmitting terminal using Hamming distance different between different coding symbol Discrimination when receiving end is detected.The big coding of configuration Hamming distance is transmitted, so as to further increase receiving end connection Close the reliability of detection.Wherein, the Hamming distance between two isometric character strings is the different words of two character string corresponding positions The number of symbol.
In one alternate embodiment, the diversity receiving method of receiving antenna array, for further increasing the channel of system Capacity.When receiving antenna number is more than or equal to 2, it can use and be combined with each other between different receiving antennas, obtain receiving end Multi-antenna diversity gain, while different antennae acquires the information of OAM phase face different location respectively, can pass through maximum-ratio combing Mode, improve signal-to-noise ratio before the detection of signal, thus when detecting width phase modulation constellation points improve system stability.
In one alternate embodiment, due to needing the OAM of different mode transforming to index when signal processing is received in docking Domain maps one by one with each relative line strengths after virtual interpolation rotation interpolation, however, in index domain, any OAM mode combinations The distance between corresponding spectral line interval is simultaneously unequal, or even several modes can occur to combine distance between corresponding spectral line special Nearly the phenomenon that even overlapping, this detection just to OAM index modulation bring difficulty.It can be widened by power distribution Spectrum intervals of the different OAM mode combinations in index domain, the selection of transmitting terminal OAM mode and power distribution algorithm are as follows: root It is believed that number vector superposed principle, be every OAM mode weights assigned coefficient, establish and optimize equation, total transmission power not In the case where change, the power point of all OAM modes for participating in superposition in different mode is adjusted by AWG (arbitrary waveform generator) Match, power discrete is determined into optimal weighting coefficients in such a way that computer search traverses, to realize all OAM of adjustment Integrated mode is equal in the Euclidean distance in index domain between corresponding spectral line, improves the reliability of detection.
Illustrate some concrete operations in Transmission system of the invention below with several specific examples, and calculates related ginseng Number verifies reliability of the invention.
First example
Transmitting terminal (transmitting antenna subsystem) can generate NtThe OAM electromagnetic wave of kind mode, and receiving end (receiving antenna Battle array) it is by NrWhat root antenna was constituted.Illustrate the information transmission side of the long range index modulation Transmission system of electromagnetic wave OAM below Formula, and spectrum efficiency and bit error rate performance when analyzing long distance transmission.Emit structural schematic diagram such as Fig. 2 institute of index modulation Show, it is assumed that width when transmission mutually modulates the phase-modulation side of selection M-PSK (multi-system digital phase modulation, also known as polyphase system) The expression of formula, various constellations point (signal of each constellation point corresponding a certain amplitude and phase) is denoted as d (m), wherein m ∈ [1,2 ..., M], M indicate m-th constellation point.Transmitting terminal can produce altogetherKind OAM mode combinations mode, can correspond toThe combination of kind bit symbol, therefore the joint transmitting symbol of each OAM combination can be expressed asArbitrary 0 or 1 bit information in ellipsis expression transmission sequence therein, 1 ×NtIndicate X(k)It is 1 row NtThe vector of column, wherein k ∈ [1,2 ..., K], indicates the kth group OAM mode combinations index of activation, member The position of element 1 means that position of the OAM mode to be transmitted in combination.In this way, the combination of transmitted letter that receiving end receives Number it can simplify expression are as follows:
Wherein,Indicate the power partition coefficient of each mode combinations, X(k)It is joint transmitting symbol,When indicating the mode combinations k of transmission OAM index modulation, transmitting terminal activate OAM mode and receiving end it Between the channel matrix that is constituted of the channel coefficients that transmit, z is the white Gaussian noise matrix that mean value is zero.The spectrum efficiency of system can To indicate are as follows:
Wherein, NaIndicate the OAM pattern count activated in index modulation, α indicates the selection coefficient of transmission mode.When each When OAM mode multiplexing transmits different information, α=1；When each OAM mode transmits identical information, α Na=1.Assuming that transmitting terminal Width mutually modulate using BPSK debud mode, it is desirable to transmission rate reaches the transmission rate of each symbol 4bit, then transmitting terminal It can produce 4 kinds of different OAM modes to be combined, sharing 15 kinds of combinations can be used to be indexed modulation transmissions, appoint Meaning selects 8 kinds in these integrated modes, with BPSK modulation be combined mapping, form joint and emit symbol, each joint Emit symbol transmission 4bit information, specific mapping relations are as shown in table 1:
The mapping relations between symbol are sent after 1 original bit sequence of table and combined coding
After free space transmission, the electromagnetic wave for carrying index modulation and M-PSK modulation intelligence reaches receiving end antenna Array, after prefilter, index modulation information and M-PSK modulation intelligence are by separate detection.In OAM part helix phase It can be by the way of virtual interpolation rotation disclosed in the patent No. 2016109163094, by the combination of different OAM modes on face Index domain is transformed to, a plurality of nonoverlapping spectral line is formed.Assuming that NrRoot receiving antenna can be indicated in the signal that t moment receives Are as follows:
Wherein,Indicate that the reception signal on each antenna, y (t) indicate that these receive the vector of signal composition, Autocorrelation operation is carried out to signal is received, autocorrelation operation, that is, signal takes expectation after being multiplied with itself, available:
Wherein, t indicates the time, and θ indicates Angle of beam divergence, φiIndicate that the radian between i-th pair receiving antenna, D indicate to pass Defeated distance, k1、k2Indicate the number of antenna, J0Indicate 0 rank Bessel function, Λ0Expression is cut in the annulus vertical with the direction of propagation The effective wavelength of OAM electromagnetic wave on direction.To go out the antenna of an equivalent rotary in the virtual interpolation in receiving end, then really Aerial array and virtual interpolation equivalent aerial between cross-correlation coefficient P (φ, t) can be represented as:
Wherein, ω indicates the revolving speed of virtual interpolation antenna.Assuming that weighting coefficient is wT(φ), for kth kind OAM mode Combination passes through the result of the available interpolation output of MMSE criterion (minimum mean square error criterion) are as follows:
Wherein, y(k)(t) original signal that antenna receives is indicated,It indicates The signal matrix obtained after being handled by the way of the virtual interpolation rotation disclosed in the patent No. 2016109163094, it is assumed that The data of index modulation can be represented as It indicates to be transmitted using OAM index modulation Data, R (K) indicates their relationships that can map one by one with virtual interpolation relative line strengths of k-th index modulation data, i.e., logical It crosses which root spectral line detection occurs in the index domain of receiving end, that is, can determine that transmitting terminal transmits any index modulation symbol.
And the data of M-PSK modulation can be represented as D={ d (1), d (2) ..., d (M) }, in receiving end, reaction is The difference of constellation point is also mapping relations one by one between constellation point and transmitting terminal data symbol, passes through the side of Maximum Likelihood Detection Formula can obtain the M-PSK modulation data that transmitting terminal is transmitted by demodulation planisphere, finally merge two parts solution adjusting data, Original user information can be obtained.
Second example
Based on a kind of electromagnetic wave orbital angular momentum index modulation Transmission system of suitable long distance transmission proposed by the present invention, Transmitting terminal combined coding emitting structural is described in detail in this example, and combines the combined decoding mistake of Viterbi decoding in receiving end Journey, it may be assumed that width phase constellation point and OAM mode combinations are placed in the same constellation space and carry out combined modulation, while in receiving end Joint decoding is carried out in conjunction with viterbi decoder, structure is as shown in Figure 2.
In two dimensional constellation optimization, the constellation point being arranged on unit circle needs to meet following principle: being arranged in same The quantity of constellation point on circle is proportional to round radius；Constellation point needs on the same circle are uniformly distributed.According to these originals Then, the optimization of constellation point can be obtained in the case where constraining average energy by maximizing Euclidean distance, it may be assumed that
Wherein, dminIndicate the minimum Eustachian distance between constellation point, EavgIndicate constellation point average energy, s.t. refers to suffered Constraint.M indicates constellation point total quantity, NiExpression radius is RiI-th of constellation circumference.The three-dimensional constellation map of the present embodiment In optimization process, each constellation point can be extended to multilayered structure, construct the star based on OAM mode combinations Yu PSK constellation space The step of optimization of seat point, is as follows:
(1) optimization PSK modulates two dimensional constellation, so that all PSK constellation points are uniformly distributed on corresponding unit circle, and Different OAM mode combinations transmit different PSK planispheres；
(2) by power distribution, spectrum intervals of the different OAM mode combinations in index domain is widened, that is, is expanded every The distance between one layer of constellation；
(3) each layer of PSK constellation point is superimposed first phase, so that constellation rotation between adjacent two layers, OAM adjustable in this way Euclidean distance between the PSK constellation point of mode combinations transmission, so that the minimum euclidean distance of entire three-dimensional constellation point is maximum.
From figure 2 it can be seen that different OAM mode combinations can be used to transmit different or identical constellation point, together Shi Butong OAM mode combinations can also transmit information as index, and z-axis side is constructed on the basis of the two dimensional constellation figure that width is mutually modulated To the third dimension modulate space, thus formed OAM-PSK joint constellation space (i.e. three-dimensional constellation map).For the modal sets of OAM Conjunction and PSK combined modulation, in transmitting terminal, raw information carries out grid coding first, is later mapped as the symbol after coding OAM-PSK combines the point in constellation space.In receiving end, signal can be received with a two array-element antenna battle arrays, using using special The OAM mode combinations of the method estimation transmitting terminal transmission of virtual interpolation rotation disclosed in benefit number 2016109163094, are adopted later It is decoded with standard Viterbi decoding algorithm to by the symbol of grid coding, psk signal constellation point is obtained, to get Original bit data.
OAM transmission is general only to apply in sighting distance (LOS) transmission environment of single diameter, and interchannel noise can regard as additive Gaussian White noise (AWGN).Receiving signal can indicate are as follows:
Wherein, fcIndicate carrier frequency, r indicate receive signal, n be mean value be zero, variance σ2White Gaussian noise, s is The transmitting signal encoded using combined modulation, l are OAM pattern count,For azimuth, k=2 π/λ is wave constant, and λ is wavelength, (x, y, z) indicates coordinate of the constellation point in three-dimensional constellation map.
If dminIndicate the Euclidean distance between grid coding three-dimensional constellation point, it can be dminAs a key index, For judging the system performance under white noise environment.Then, the bit error rate may be expressed as:
Wherein Q () is Gaussian function, EbIndicate symbol energy, N0Indicate the energy of noise
Third example
Assuming that transmitting terminal can produce multiple OAM modes, the method structure that receiving end is rotated using the virtual interpolation of two antennas Index domain.Assuming that a receiving antenna is as reference position, the initial phase of all OAM modes is aligned on reference position, then On second antenna, the combination signal of different OAM modes can be written as follow form:
After abbreviation, superimposed signal can be expressed as the form of vector:
If
So receiving signal can further be write
As shown in Figure 3, whereinIndicate signal amplitude, liIndicating OAM pattern count, L indicates total OAM mode quantity, Indicate that the phase difference that each OAM mode generates between two receiving antennas, S indicate that superimposed signal, X indicate superposed signal In the projection of x-axis direction, Y indicate superposed signal in the projection of x-axis direction,Indicate superposed signal two receiving antennas it Between the phase difference that generates, ω indicates that the angular frequency of signal, t indicate the time, and the OAM mode superposition of different mode meets parallel four side The vector superposed rule of shape, therefore in the case where the phase difference that different OAM modes are formed between the antenna of receiving end two is certain, The amplitude that the different OAM modes of superposition can be participated in by changing realizes that control changes the purpose of superposed signal phase.
Assuming that transmitting terminal can generate NtKind OAM electromagnetic wave, selects N every timeaA OAM emits identical M-PSK signal, and All OAM modes realize phase alignment on the reference antenna of receiving end first, then for kth kind integrated mode, second The phase difference of OAM mode combinations between root receiving antenna and first receiving antenna are as follows:
Wherein,Indicate the phase difference between kth group antenna,It indicates from NtN is selected inside root antennaaAll groups of kind At mode moreover, each phase difference corresponds to a kind of OAM transmitting integrated mode after rotating interpolation by virtual interpolation, it is assumed that transmitting terminal It can produce the OAM signal of 4 kinds of different modes, pattern count is respectively 1,2,3,4 to be combined transmitting, can at most be formed in 15 Different combinations can choose 8 kinds therein and be indexed modulation transmissions, in conjunction with BPSK constellation point, so that combined system reaches The transmission rate of each symbol 4bit.And in selected mode combinations, if the power of all OAM modes evenly distributes, It is essentially identical that phase difference is formed by when so the combination of mode 1 and 3 individually emits with mode 2 on the antenna of receiving end two, It namely causes in index domain due to not being easily distinguishable between spectral line since distance is too close.Therefore, this example is by changing not With power partition coefficient of the OAM mode in various combinationTo control the phase difference for changing adduction signal, that is to say, that pass through Change power distribution of the transmitting terminal difference OAM when transmitting identical signal weighting, the mode combinations of each OAM can be made to exist Index domain corresponding spectral line separation, thus realize the combinations of different OAM modes in index domain between different spectral lines one by one Mapping relations.
It is as equal as possible in order to reach the Euclidean distance between all spectral lines, in other words, that is, realize all combinations The minimum phase difference of pattern vector superposed signal maximizes, as far as possible the Euclidean distance between expansion different mode, the function of transmitting terminal Rate distribution can further be modeled as following optimization problem:
Wherein,Indicate the power partition coefficient of different mode, εkIndicate phase differenceThe smallest mode combinations,Table Show and selects L from L kind mode combinationsAThe number of combinations of kind,Indicate the phase difference between two antennas, PtolIndicate general power.It is logical Optimization power distribution model is crossed, in the case where total transmission power is constant, all participations in different mode is adjusted by AWG and are superimposed OAM signal power distribution.The step of specific power distribution, is as follows:
(1) under the premise of all OAM integrated modes known, transmission power discrete quantized can be become different first Small section, the quantity setting in specific section can be to be determined according to the computing capability of transmitting terminal computer；
(2) for each integrated mode, successively change the power partition coefficient of difference OAM mode in integrated mode Further calculate difference OAM integrated mode phase difference caused by receiving end under this distribution coefficient；
(3) it in the case where guaranteeing the constant restrictive condition of total transmission power, in such a way that computer search traverses, successively traverses The phase for making all OAM combinations is found in power combination mode of all integrated modes under the distribution coefficient of division, search The equal power distribution mode of difference is implemented as optimal power distribution mode in transmitting terminal, to realize that adjustment is all OAM integrated mode is equal in the Euclidean distance in index domain between corresponding spectral line, improves the reliability of detection.Corresponding reality Power distribution result of all OAM modes in different index combinations of modulation applied in example is as shown in table 2:
Power distribution result of the 2 OAM mode of table in different index combinations of modulation
Wherein, the power partition coefficient for indicating each OAM mode in various combination, in the case where general power is constant, root The transmission power of each mode is adjusted flexibly according to different mode combination, forms combination and sends symbol, to realize rope in receiving end Draw the highly reliable detection in domain between integrated mode and spectral line.
It is to illustrate by taking two receiving antennas as an example above, actually receiving subsystem is the reception that can have two or more Antenna, for wantonly two receiving antennas, the method in building index domain and the method for above-mentioned two receiving antennas are not different, The descriptions thereof are omitted for this.
4th example
The present embodiment is similar with first, 3rd embodiment, it is still assumed that the transmitting terminal of OAM index modulation system in this example It can produce the OAM signal of 4 kinds of different modes, in order to as a comparison, assume that MIMO (refers in transmitting terminal and receiving end in simulations Multiple transmitting antennas and receiving antenna are used respectively, make signal by the transmission of the mutiple antennas of transmitting terminal and receiving end and is received) The transmitting terminal of system also configures 4 identical antennas, and total transmission power is certain, and receiving end configures NrThe common receiving antenna of root, The bit error rate performance and system transmission capacity of simulation analysis Transmission system are with the variation for receiving diversity.
In OAM index modulation method proposed by the present invention, transmitting terminal respectively selects the combination of different OAM modes And power distribution, transmitted OAM integrated mode, while detection combination are determined using the method for virtual interpolation rotation in receiving end The BPSK constellation point that mode is transmitted, combined demodulation go out user data.And multi-aerial transmission system as a comparison is sighting distance MIMO (LoS-MIMO) communication system, receiving end determines the characteristic of channel by the method that open loop channel is estimated, that is, does not need pilot tone Information, directly according to the characteristic estimating channel information of signal, simulation process calculates different in the case where known channel characteristic The bit error rate performance of Transmission system, as shown in Figure 4.
Wherein, the AWGN in annotating in figure indicates that additive white Gaussian noise, OAM:4 indicate that transmitting terminal transmits 4 kinds of different moulds The OAM signal of formula, Rx:2 indicate that there are two antennas in receiving end, and Tx:4 indicates that transmitting terminal has 4 antennas.
It is passed figure 4, it is seen that carrying out joint index modulation using 4 kinds of OAM mode combination QPSK width phase modulation systems It is defeated, and three-dimensional space constellation point, receiving end N are formed by combined codingr=2, each symbol transmission 4bit/ may be implemented in system The communication efficiency of s/Hz, and to reach identical communications rate.Width phase modulator approach generallys use the transmission of high order modulation Mode can compare the error performance that constellation point modulation is carried out using 16QAM.And use the LoS-MIMO of 4 same antennas configuration Transmission system will realize that identical symbol transmission rate is similarly needed using in each antenna multiplexed transmission QPSK constellation Point.Emulation display, LoS-MIMO of the OAM index modulation system proposed by the present invention compared to known channel characteristic CSI transmit system System has the lower bit error rate, because OAM index modulation system can preferably avoid intercarrier interference, and introduces Spatial gain, therefore error performance can be further decreased than Generic MIMO systems the case where realizing same frequency spectrum efficiency.Together When OAM each activating part radio frequency link of index modulation system, so complicated conflict avoidance algorithm there is no need to.It receives Machine design is simpler than V-BLAST, therefore has lower system implementation complexity, can reduce link overhead.And compared to High-order modulating under same frequency spectrum efficiency term, OAM index modulation method error performance proposed by the present invention are decreased obviously, This is because the method that OAM index modulation system proposed by the present invention uses combined coding, ordinary two dimensional planisphere is changed At three-dimensional space planisphere, and using the phase rotation between Different Plane planisphere, further widen between constellation point Euclidean distance, therefore the reliability of system greatly enhances.
The present invention also provides a kind of electromagnetic wave orbital angular momentum index modulation transmission method of suitable long distance transmission, this biographies Transmission method is not only applicable to the OAM electromagnetic transmission within 1 kilometer and receives, and is also applied for 1 kilometer or more of long range The transmission and reception of OAM electromagnetic wave, comprising the following steps:
The raw information coding of user is become into the bit information to be transmitted；
Bit information is decomposed into two parts, and a part input width mutually modulates mapping block, and mapping becomes the width to be transmitted Phase constellation point, another part enter OAM index modulation mapping block, establish one by one by searching for table from different OAM mode combinations Mapping relations；
Two parts information synthesizes the IF carrier to be transmitted, the OAM of control antenna feed transmitting different mode combination In free space transmission after electromagnetic wave, emitted face and lens energy centralization；
Fractional phase face receiving antenna receives the electromagnetic wave in free space, is translated into intermediate-freuqncy signal, width Bit information corresponding to phase modulation detection module detection output width phase constellation point, intermediate-freuqncy signal index mapping mould by phase difference Different spectral lines is formed in index domain after block and index domain filter, the position occurred in index domain by judging different spectral lines It sets, and then demodulates the bit information that OAM mode combinations are transmitted, the merging of two parts bit information recovers the raw information.
Preferably, the big bit information of the small OAM mode combinations configuration Hamming distance of difference is transmitted.
Preferably, it detects phase difference different between receiving antenna and establishes mapping one by one from different OAM mode combinations and close The method of system includes virtual interpolation spinning solution, two o'clock phase gradient direct Detection Method, point approximation detection method, phase accumulation inspection One of survey method is a variety of.
Preferably, it is every OAM mode weights assigned coefficient, establishes and optimize equation, in the feelings that total transmission power is constant Under condition, power discrete is passed through by meter by the power distribution that AWG adjusts all OAM modes for participating in superposition in different mode The mode of calculation machine search spread, determines optimal weighting coefficients, to realize that all OAM integrated modes of adjustment are corresponding in index domain Spectral line between Euclidean distance it is equal.
The above description is only a preferred embodiment of the present invention, is not intended to restrict the invention, for those skilled in the art For member, the invention may be variously modified and varied.All within the spirits and principles of the present invention, it is made it is any modification, Equivalent replacement, improvement etc., should all be included in the protection scope of the present invention.

Claims (10)

1. a kind of orbital angular momentum index modulation Transmission system of suitable long distance transmission, which is characterized in that occur including signal Subsystem, transmitting antenna subsystem, fractional phase face receiving subsystem, wherein
Subsystem occurs for signal
Combined coding module: the raw information coding that user is sent becomes bit information；
Bit decomposing module: bit information is resolved into two parts, a part input width mutually modulates mapping block, and another part is defeated Enter OAM index modulation mapping block；
Width mutually modulates mapping block: representing different width from each using any bit information by input in constellation modulation system The width phase constellation point of degree and phase establishes one-to-one relationship；
OAM index modulation mapping block: being provided with the look-up table comprising different OAM mode combinations, by bit information and corresponding choosing The OAM mode combinations for selecting transmitting establish mapping relations one by one；
Virtual arbitrary waveform generator module: width mutually modulates mapping block and the information of OAM index modulation mapping block output passes through wave Shape generator synthesizes joint transmitting symbol；
The joint transmitting symbol that transmitting antenna subsystem is used to generate waveform generator is by up-conversion and power amplification rear feed Be sent to different OAM to occur on a period of time, form multichannel OAM combination transmitting signal, after reflecting surface and lens are to energy centralization It is transmitted in free space；
Fractional phase face receiving subsystem includes:
Receiving antenna array: being converted into radiofrequency signal for the electromagnetic wave transmitted in free space, and radio frequency link is by the radiofrequency signal Intermediate-freuqncy signal is down-converted to, fractional phase face refers to that the partial region of same phase face is arranged in receiving antenna array；
Prefilter: intermediate-freuqncy signal exports two-way after passing through prefilter, and input phase difference indexes mapping block all the way, separately Width phase modulation detection module is inputted all the way；
Phase difference indexes mapping block: by phase difference between receiving antenna on fractional phase face, between different OAM mode combinations Mapping relations one by one are established, so that bit information is mapped to index domain；
Index domain filter: the signal after indexing mapping block building mapping relations by phase difference passes through index domain filter filter After wave output, different spectral lines, and the corresponding spectral line of combination of each OAM mode are formed in index domain；
Width phase modulation detection module: it receives the filtered carrier signal of prefilter and goes forward side by side to demodulate width phase constellation point And obtain bit information corresponding with width phase constellation point；
OAM mode combinations index modulation detection module: each spectral line in detection identification index domain, according to the look-up table, Detection determines the bit information transmitted by OAM mode combinations；
Planisphere combinatorial mapping module: the bit information for the width phase constellation point output that width phase modulation detection module is detected with The bit information that OAM mode combinations index modulation detection module demodulates, according to the bit exploded relationship of transmitting terminal, by two Bit information is divided to reconfigure, to form the corresponding bit information of the complete raw information；
Combined decoding module: for receiving the original user bit information of planisphere combinatorial mapping module output to restore user The raw information of transmission.
2. a kind of orbital angular momentum index modulation Transmission system of suitable long distance transmission as described in claim 1, feature It is,
Transmitting antenna subsystem includes the antenna feed and its radio frequency link for generating different OAM modes, and radio frequency link includes function point Device, frequency mixer, amplifier and radio frequency original part, antenna feed are the forms of antenna element or resonant cavity, and antenna feed is antenna The form of a period of time or resonant cavity；
Reflecting surface is the paraboloid with or without Meta Materials；
Lens are convex lens or Meta Materials lens；Receiving antenna includes frequency mixer, amplifier, power splitter and radio frequency link, is connect Receiving antenna is aerial array, resonant cavity or the sensor that detection is received for OAM.
3. a kind of orbital angular momentum index modulation Transmission system of suitable long distance transmission according to claim 1, special Sign is that constellation modulation system includes BPSK, QPSK, QAM.
4. a kind of orbital angular momentum index modulation Transmission system of suitable long distance transmission according to claim 1, special Sign is,
The electromagnetic wave includes one of light wave, microwave, millimeter wave and THz wave or a variety of.
5. a kind of orbital angular momentum index modulation Transmission system of suitable long distance transmission according to claim 2, special Sign is,
The antenna feed and/or the receiving antenna be electromagnetic horn, parabola antenna, card plug brother's human relations antenna, paster antenna, One of array antenna.
6. a kind of orbital angular momentum index modulation Transmission system of suitable long distance transmission according to claim 1, special Sign is,
The equipment for generating different mode OAM electromagnetic wave is spiral phase plate, specific reflection surface antenna, specific feed antenna, phased One of array antenna, spatial light modulator, diffraction grating and Meta Materials are a variety of.
7. a kind of orbital angular momentum index modulation transmission method of suitable long distance transmission, which comprises the following steps:
The raw information coding of user is become into the bit information to be transmitted；
Bit information is decomposed into two parts, and a part input width mutually modulates mapping block, and mapping becomes the width phase star to be transmitted Seat point, another part enter OAM index modulation mapping block, map one by one by searching for table from the foundation of different OAM mode combinations Relationship；
Two parts information synthesizes the IF carrier to be transmitted, the OAM electromagnetism of control antenna feed transmitting different mode combination In free space transmission after wave, emitted face and lens energy centralization；
Receiving antenna receives the electromagnetic wave in free space on fractional phase face, is translated into intermediate-freuqncy signal, width Bit information corresponding to phase modulation detection module detection output width phase constellation point, intermediate-freuqncy signal index mapping mould by phase difference Different spectral lines is formed in index domain after block and index domain filter, the position occurred in index domain by judging different spectral lines It sets, and then demodulates the bit information that OAM mode combinations are transmitted, the merging of two parts bit information recovers the raw information.
8. a kind of orbital angular momentum index modulation transmission method of suitable long distance transmission according to claim 7, special Sign is,
The big bit information of the small OAM mode combinations configuration Hamming distance of difference is transmitted, wherein the difference of OAM mode combinations Not small the distance between the spectral line for referring to that OAM mode combinations are converted in index domain is less than preset distance threshold.
9. a kind of orbital angular momentum index modulation transmission method of suitable long distance transmission according to claim 7, special Sign is,
Transmitting antenna subsystem generates NtThe OAM electromagnetic wave of kind mode, receiving antenna array includes NrRoot antenna, receiving antenna array pass Width when defeated mutually modulates selection M-PSK, and the expression of various constellations point is denoted as d (m), wherein m ∈ [1,2 ..., M], and M indicates m-th Constellation point, transmitting antenna subsystem common property are rawKind OAM mode combinations mode, it is correspondingKind bit symbol Combination, each OAM combination joint transmitting symbol be expressed asIn formula Ellipsis indicate send sequence in arbitrary 0 or 1 bit information, 1 × NtIndicate X(k)It is 1 row NtThe vector of column, wherein k ∈ [1,2 ..., K] indicates the kth group OAM mode combinations index of activation, and the position of element 1 means that the OAM mode to be transmitted Position in combination, the combination of transmitted signal that thus receiving antenna array receives are simplified shown as:
Wherein,Indicate the power partition coefficient of each mode combinations, X(k)It is joint transmitting symbol,When indicating the mode combinations k of transmission OAM index modulation, the activation OAM mode of transmitting antenna subsystem The channel matrix that the channel coefficients transmitted between receiving antenna array are constituted, z are the white Gaussian noise matrixes that mean value is zero.
10. a kind of orbital angular momentum index modulation transmission method of suitable long distance transmission according to claim 7, special Sign is,
For every OAM mode weights assigned coefficient, establishes optimization equation and pass through AWG in the case where total transmission power is constant The power distribution of all OAM modes for participating in superposition traverses power discrete by computer search in adjustment different mode Mode, optimal weighting coefficients are determined, to realize all OAM integrated modes of adjustment in index domain between corresponding spectral line Euclidean distance is equal.
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