Uniform rectangular array OAM modal antenna, airspace field digital modulation orbital angular momentum broadband anti-interference communication method and system

Abstract

The invention relates to the technical field of wireless communication, in particular to an OAM modal antenna of a uniform rectangular array and an airspace field digital modulation orbital angular momentum broadband anti-interference communication method and system. The OAM modal antenna comprises a first dielectric plate and a plurality of array elements, wherein each array element comprises a left-right hand metamaterial metal patch unit and a second dielectric plate; the second dielectric plate is constructed by adopting a metamaterial mixed dielectric resonator, and left and right hand metamaterial metal patch units are printed on the surface of the second dielectric plate; the left-hand metamaterial metal patch units divide the surface of the second dielectric plate into a plurality of areas, and each area is printed with a right-hand metamaterial metal patch unit; outside an antenna working frequency band, the effective dielectric constant epsilon ilt of an array element; 0, the equivalent magnetic conductivity uegt; 0; in the working frequency band of the antenna, the effective dielectric constant epsilon e is greater than the relative dielectric constant epsilon r, and the equivalent magnetic conductivity is uegt; 0. According to the invention, the requirements of wireless communication on bandwidth and spectrum resources can be improved, and the anti-interference capability of the system is enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless communication, in particular to an OAM mode antenna of a uniform rectangular array, a spatial field digital modulation orbital angular momentum wideband anti-interference communication method and system. BACKGROUND

[0002] With the continuous growth of traffic, Internet of Everything needs high-speed data transmission as a guarantee. With the advent of the 5G era, the user peak data rate will reach 1G bps. It is expected that the user peak data rate will increase to T bps in the future 6G era. For the backhaul link between base stations, the data transmission rate will undoubtedly reach 1T bps, so it will bring huge demand for bandwidth and spectrum resources.

[0003] However, the electromagnetic wave signal spectrum resources used by the current wireless communication are limited, and the channels are extremely susceptible to mutual interference and external interference, so it is urgent to develop a new dimension of wireless transmission - orbital angular momentum. The orthogonality between the orbital angular momentum modes can simplify the complexity of the receiver signal demodulation and has anti-interference ability. However, the misalignment of the transceiver antenna of the orbital angular momentum communication system can easily cause inter-modal crosstalk problems, and the accuracy, flexibility and power distribution consistency of the current analog phase shift architecture are difficult to meet the needs of solving this problem, and the analog phase shift architecture also reduces the purity of the mode. SUMMARY

[0004] In order to solve the problems existing in the prior art, the present application provides an OAM mode antenna of a uniform rectangular array, a spatial field digital modulation orbital angular momentum wideband anti-interference communication method and system, which can improve the current demand for bandwidth and spectrum resources of wireless communication, and at the same time, the anti-interference ability of the system is strengthened.

[0005] In a first aspect, an embodiment of the present application provides an OAM mode antenna of a uniform rectangular array, comprising a first dielectric plate and a plurality of array elements arranged on the first dielectric plate, each array element comprising a right-handed metamaterial metal patch unit, a left-handed metamaterial metal patch unit and a second dielectric plate.

[0006] The second dielectric plate is constructed by a metamaterial hybrid dielectric resonator, and the right-handed metamaterial metal patch unit and the left-handed metamaterial metal patch unit are printed on the surface of the second dielectric plate; the left-handed metamaterial metal patch unit divides the surface of the second dielectric plate into a plurality of regions, and each region is printed with a right-handed metamaterial metal patch unit;

[0007] Outside the working frequency band of the antenna, the equivalent permittivity ε e <0, and the equivalent permeability u e >0; inside the working frequency band of the antenna, the equivalent permittivity ε e >0, and the relative permittivity εr , equivalent permeability u e >0.

[0008] Preferably, the left-handed metamaterial metal patch unit is distributed in a cross shape on the surface of the second dielectric plate, and the surface of the second dielectric plate is divided into four regions; the array element is provided with four, and the spacing between the array elements is 0.6 times the center frequency wavelength.

[0009] In a second aspect, the embodiment of the present application provides a spatial field digital modulation orbital angular momentum broadband anti-interference communication system, which comprises an interferer, a broadband communication system and the OAM mode antenna; the broadband communication system is provided with a transceiving digital phase shift architecture, and the interferer is used for transmitting same-frequency interference on an air interface;

[0010] The transceiving digital phase shift architecture comprises an OAM modulator and an OAM demodulator, and is used for realizing the orbital angular momentum mode transceiving communication of the OAM mode antenna, generating an OAM vortex beam through baseband digital phase shift, and resisting the interference of the interferer, wherein the OAM modulator is arranged at a transmitting end of the broadband communication system, and the OAM demodulator is arranged at a receiving end of the broadband communication system.

[0011] In a third aspect, the embodiment of the present application provides a spatial field digital modulation orbital angular momentum broadband anti-interference communication method, which is realized based on the anti-interference communication system, and the method comprises the following steps:

[0012] S1, continuously transmitting an interference signal directed to a receiving end on an air interface at a transmitting end, wherein the transmitted interference signal has a preset signal-to-interference ratio;

[0013] S2, processing an orbital angular momentum digital signal and an analog signal through the broadband anti-interference communication system;

[0014] S3, defining h l as a channel gain of a useful signal from the transmitting end of the OAM mode antenna to the receiving end; as a channel gain of the kth interference signal from the interferer to the receiving end; s I (t) as the corresponding kth interference signal; according to the useful signal transmitted by the transmitting end, in combination with the channel gain h l 、 and a noise signal and an interference signal, a receiving signal of the receiving end of the OAM mode antenna is obtained;

[0015] S4, utilizing the orthogonality between the orbital angular momentum modes, radiating spatial fields with the same mode at the transmitting end and the receiving end, and matching the modes, while for the interference signal, the modes are mismatched; and filtering the signal after demodulation at the receiving end.

[0016] Compared with the prior art, the present application has the following advantages:

[0017] 1) Constructing array elements by using left-hand and right-hand composite metamaterial mixed medium resonator, and realizing the wideband characteristics of antenna array by the orthogonal wideband characteristic mode of array elements.

[0018] 2) High isolation within and between array elements, so as to support simultaneous multi-mode transmission at the same frequency.

[0019] 3) Realizing the uniform rectangular array orbital angular momentum mode communication by the baseband digital phase shift architecture, solving the alignment problem of the orbital angular momentum mode transmitting and receiving antenna, and reducing the size of the array.

[0020] 4) Based on the digital domain module design, the orbital angular momentum mode matching filter signal-to-noise ratio criterion and anti-interference method are designed, which improves the transmission data rate and strengthens the anti-interference ability of the system. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is the characteristic mode saliency diagram of the array element, wherein (a) is the characteristic mode saliency diagram of the array element in the prior art, and (b) is the characteristic mode saliency diagram of the array element in the embodiment of the application;

[0022] Figure 2 It is the structure diagram of the uniform rectangular array antenna in the embodiment of the application, wherein (a) is the overall structure diagram of the uniform rectangular array antenna, (b) is the top view of the first dielectric plate, (c) is the bottom view of the first dielectric plate, (d) is the top view of the second dielectric plate, and (e) is the bottom view of the second dielectric plate;

[0023] Figure 3 It is the relationship diagram between the equivalent permittivity ε e , the equivalent permeability μ e , the relative permittivity ε r of the substrate FR4 and the frequency in the embodiment of the application;

[0024] Figure 4 It is the structure diagram of the orbital angular momentum wideband anti-interference communication system in the embodiment of the application;

[0025] Figure 5 It illustrates the constellation diagram of the receiving end when there is or is not additional interference, wherein (a) is the constellation diagram of the transmitting and receiving l = + 1 without interference, (b) is the constellation diagram of the transmitting and receiving l = + 1 with interference l = 0, (c) is the constellation diagram of the transmitting and receiving l = - 1 without interference, (d) is the constellation diagram of the transmitting and receiving l = - 1 with interference l = 0, (e) is the constellation diagram of the transmitting and receiving l = 0 without interference, and (f) is the constellation diagram of the transmitting and receiving l = 0 with interference l = 0;

[0026] Figure 6 It is the bit error rate when there is / without 15° incident interference signal in the l = ± 1 ~ ± 1 mode communication. DETAILED DESCRIPTION

[0027] The technical solutions in the present application will be clearly and completely described below with reference to the drawings in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of the present application.

[0028] Embodiment

[0029] The present embodiment first proposes an OAM modal antenna of a uniform rectangular array. From the new dimension of electromagnetic field, i.e., orbital angular momentum (OAM), a uniform rectangular array antenna of multiple modes at the same frequency and at the same time is studied. The wideband of the uniform rectangular array antenna enables the system to have the ability to transmit a larger amount of data. The wideband uniform rectangular array is realized by designing and constructing array elements using the wideband orthogonal medium characteristic mode, and arranging the array elements according to a certain wavelength to form the uniform rectangular array.

[0030] The wideband orthogonal medium characteristic mode significance (modal significance) is shown in Figure 1 . Figure 1 The first six characteristic modes numbered M1-M6 are given in the middle. The modes numbered M1-M2 are a pair of orthogonal surface current modes; and the modes numbered M3-M4 and M5-M6 are two pairs of characteristic modes with out-of-phase surface currents. Compared with the mode significance obtained by the current metamaterial antenna, the mode significance of the OAM modal antenna of the present embodiment has two main differences: the first difference is that there are only two orthogonal modes in the band, and the value is close to 1, while other unwanted modes that can easily cause the antenna pattern to be distorted are frequency-shifted to the outside of the band or suppressed, so that the value is less than 0.3; the second difference is that the frequency band width covered by the mode value greater than 0.8 is conducive to the design of wideband performance.

[0031] In the present embodiment, the OAM modal antenna of the uniform rectangular array adopts a wideband uniform rectangular array for generating an OAM beam by baseband digital phase shift, develops a dual-polarized array element using a pair of wideband orthogonal medium resonance characteristic modes, and arranges the dual-polarized array element according to a certain wavelength to form a uniform rectangular array. Specifically, the uniform rectangular array includes four array elements, and the spacing between the array elements is 0.6 times the center frequency wavelength.

[0032] As shown in Figure 2 , in the OAM modal antenna, a right-handed metamaterial metal patch unit 201 with an electromagnetic band gap (EBG) is embedded into a left-handed metamaterial metal patch unit 202 mixed dielectric resonator (DR) to form a composite metamaterial unit. The right-handed metamaterial metal patch unit 201 and the left-handed metamaterial metal patch unit 202 are printed on the surface of the second dielectric plate 209 to construct an array element. The equivalent permittivity εe , and the equivalent permeability u e <0, the equivalent permeability u e >0, which is the characteristic of plasmonic material, showing attenuation characteristics to electromagnetic waves; and in the antenna operating frequency band, the equivalent permittivity ε e >0, and the equivalent permeability u r >0, which is the characteristic of plasmonic material, showing attenuation characteristics to electromagnetic waves; and in the antenna operating frequency band, the equivalent permittivity ε e >0, and the equivalent permeability u

[0033] Therefore, the OAM mode antenna of the embodiment has high isolation between the array elements and between the array elements, so that the array supports simultaneous multi-mode transmission at the same frequency, and improves the spectral efficiency. The equivalent permittivity ε e , the equivalent permeability u e , the relative permittivity ε r of the substrate FR4, and the frequency are related, as shown in Figure 3 .

[0034] More specifically, the OAM mode antenna of the embodiment adopts a 2x2 array, including 4 first dielectric plates 208 and 2 second dielectric plates 209. Each second dielectric plate 209 is constructed by a metamaterial (MTM) unit mixed dielectric resonator, which can also be called a rectangular dielectric resonator; wherein the MTM unit includes 4 left-handed metamaterial metal patch units 201, right-handed metamaterial metal patch units 202, and metalized vias 203, and the left-handed metamaterial metal patch units and the right-handed metamaterial metal patch units are printed on the surface of the second dielectric plate; the left-handed metamaterial metal patch units 202 are distributed in a cross shape on the surface of the second dielectric plate, dividing the surface of the second dielectric plate 209 into 4 areas, and each area is printed with a right-handed metamaterial metal patch unit 201. The first dielectric plate 208 is printed with two microstrip line structures for polarization feeding in each array element, which are designed as typical "U" shaped microstrip lines 210 and "M" shaped microstrip lines 211. The first dielectric plate is also provided with a first gap 206 and a second gap 207 for coupling to excite the selected array element broadband characteristic mode, and the distribution of the first gap and the second gap on the first dielectric plate matches the distribution of the left-handed metamaterial metal patch units on the surface of the second dielectric plate. The first dielectric plate and the second dielectric plate can be bonded together, or fixed together by plastic screws through non-metalized vias 204 and 205.

[0035] Further, the relative permittivity of the rectangular dielectric resonator is replaced by the equivalent permittivity of the array element proposed in the embodiment, so that the resonant frequency is reduced, the antenna radiation performance is improved, and the size is reduced, and the relative permittivity εr ≥20, to improve the antenna performance. The fundamental mode is thus calculated In the S band, the array element size is about 0.26λ.

[0036] The array elements are arranged in the rectangular coordinates (x, y, z) as a URA, and the array element spacing is about 0.5λ. The array element pattern function is calculated as follows:

[0037]

[0038] wherein, is the array element pattern, The atan2(x, y) function is a four-quadrant arctangent function; is the beam azimuth angle, and θ is the beam elevation angle, is the beam target pointing azimuth angle, and θ1 is the beam target pointing elevation angle.

[0039] As shown in Figure 4 , the tested OAM mode antenna is used to build an orbital angular momentum wideband anti-interference communication system with spatial field digital modulation, so as to solve the mode interference problem that easily occurs due to misalignment of the transmitting and receiving antennas of the orbital angular momentum communication system.

[0040] The orbital angular momentum wideband anti-interference communication system with spatial field digital modulation provided in the embodiment comprises a wideband uniform rectangular array antenna (i.e. an OAM mode antenna), an interferer 412, and a wideband communication system. The wideband communication system is provided with a transmitting and receiving digital phase shift architecture, and the interferer is used to transmit same-frequency interference on the air interface to verify the anti-interference capability of the system. The orthogonal medium characteristic mode of the wideband realizes the wideband characteristics of the uniform rectangular array, and the high isolation within and between the array elements enables the support of simultaneous same-frequency multi-mode transmission.

[0041] In the embodiment, the wideband communication system comprises an encoder 401, an IQ modulator 402, a digital-to-analog converter 404, a low-pass filter 405, a mixer 406, a band-pass filter 407, a high-power amplifier 408, and a radio frequency interface 409 connected in sequence at the transmitting end, and a radio frequency interface, a low-noise amplifier 414, a band-pass filter, a mixer, a low-pass filter, an analog-to-digital converter 415, an IQ demodulator 417, and a decoder 418 connected in sequence at the receiving end.

[0042] The transceiving digital phase shift architecture includes an OAM modulator 403 and an OAM demodulator 416 for realizing modal OAM antenna orbital angular momentum modal transceiving communication, generating OAM vortex beams through baseband digital phase shift, resisting interference of an interferometer, wherein the OAM modulator 403 is arranged at a transmitting end of a broadband communication system, and the OAM demodulator 416 is arranged at a receiving end of the broadband communication system. Specifically, the OAM modulator is connected between an IQ modulator and a digital-to-analog converter, and the OAM demodulator is connected between an analog-to-digital converter and an IQ demodulator. The orbital angular momentum modal matching filtering of the spatial electromagnetic wave field interferes with the signal, so that the system can resist the interference signal of a certain interference-to-signal ratio (ISR).

[0043] Wherein, the broadband uniform rectangular array antenna includes a transmitting end uniform rectangular array OAM modal antenna 411 and a receiving end uniform rectangular array OAM modal antenna 413, and the transmitting end uniform rectangular array OAM modal antenna and the receiving end uniform rectangular array OAM modal antenna are connected with a radio frequency interface of the broadband communication system through a cable 410. The transmitting end uniform rectangular array OAM modal antenna transmits a vortex wave beam 420 to the receiving end uniform rectangular array OAM modal antenna.

[0044] In the anti-interference communication system, the transceiving digital phase shift architecture realizes the phase required by the orbital angular momentum in the signal baseband. More importantly, each baseband signal at the transmitting end is multiplied by a complex number through the OAM modulator 403 The array element feeding phase is a m The array element feeding amplitude is that each baseband signal at the receiving end is multiplied by a complex conjugate quantity through the OAM demodulator 416 The phase quantity and signal strength required by different orbital angular momentum modes are realized in a digital manner, which can not only realize the port phase required for generating the orbital angular momentum, but also improve the beam pointing, achieve transceiving beam alignment, and reduce the beam sidelobe. Wherein, the port phase difference satisfies 2π*l / N, l is the OAM mode order, and N is the number of array elements.

[0045] Further, the channel initial phase difference of the transceiving digital phase shift architecture is 0, the system adopts the transceiving channel reciprocity and channel relative reference mechanism, first completes the receiving channel initial power and phase difference compensation calibration through the software design of local variables at the receiving end. Then, the global variables at the transmitting and receiving ends are designed, the channel amplitude and phase of the transmitting end are calculated based on the calibrated receiving end phase and amplitude, and the amplitude and phase difference compensation between channels is completed with the first channel as the reference.

[0046] The power and phase consistency of the system transceiver link channel is an important prerequisite for transmitting OAM beams. The host computer defines the center frequency of the USPR at the transmitting end, and then connects the vector signal transmitter (VST) RF in port, and the RF in superposition +33dBm signal source, tests the output signal power of the four channels after superposition, takes the first channel as a reference, compensates for the power difference to calibrate the transmitting channel power. Similarly, the RF out of the transmitter VST is connected to the receiving USRP four channels, the VST outputs a single signal with a signal strength of -20dBm, i.e. 0.01mW. After the signal passes through the USRP, the signal is collected and the power spectrum is calculated. Taking the first channel as a reference, the power values received by the remaining channels are also obtained and compensated. The results show that the power consistency between the transmitting and receiving channels of the USRP-based system is good.

[0047] Then, the initial phase difference between the transmitting and receiving channels of the USRP-based system is calibrated. The relative reference principle is adopted, and the calibration program is written to complete the initial phase difference calibration of the transmitting and receiving channels. First, the initial phase difference between the receiving channels is calibrated. Specifically, the first channel of the transmitting USRP is taken as the transmission, and a one-to-four power divider is connected. Then, the four ports of the receiving USRP are connected in turn, the host computer 419 defines the transmitting USRP to transmit a single signal, the phase difference of the four ports of the receiving USRP is tested (taking the first channel as a reference), and the phase compensation is made to make the phases of the four ports of the receiving USRP substantially consistent. Finally, taking the calibrated initial phase difference between the receiving channels as a reference, the four ports of the transmitting / receiving USRP are connected in turn, the initial phase difference between the transmitting channels is tested, and the global variable is set. The program automatically compensates for the phase difference between the four channels of the transmitting USRP.

[0048] Based on the same inventive concept, to solve the technical problem that wireless communication channels are easily interfered by each other and external interference, based on the orthogonality between orbital angular momentum modes, the embodiment also proposes a spatial field digital modulation orbital angular momentum wideband anti-interference communication method, which adopts mode matching filtering signal-to-noise ratio criterion and anti-interference technology, improves the transmission data rate and solves the interference problem.

[0049] In the embodiment, the above-mentioned wideband anti-interference communication method comprises the following steps:

[0050] S1, first, continuously transmit an interference signal directed to the receiving end through the air interface at the transmitting end, and the transmitted interference signal has a preset interference-to-signal ratio.

[0051] Specifically: in the transmitting end, the useful signal transmitter and the jammer transmit signals respectively, according to the single variable method, in the receiving end, the receiver and the receiving power, the communication link environment are ensured to be the same, the transmitting signal power and the radiator gain of the useful signal transmitter and the jammer in the transmitting end are adjusted respectively, the power spectrum received by the receiving end is calculated in turn, the size of the ISR is determined and the parameters are saved.

[0052] S2, the orbital angular momentum broadband anti-jamming communication system processes the digital signal and the analog signal of the orbital angular momentum through the spatial field digital modulation, wherein:

[0053] The processing of the digital signal, the transmitting end modulates the multi-phase shift keying (MPSK) baseband signal through the OAM modulator, and after digital-to-analog conversion, the signal is moved to the intermediate frequency or directly to the radio frequency band, and then is transmitted through the transmitting end uniform rectangular array antenna. The receiving end receives the electromagnetic wave signal through the receiving end uniform rectangular array antenna, and after frequency conversion, the frequency-converted signal is directly discretized after analog-to-digital conversion; the discrete data is subjected to OAM mode demodulation processing to obtain digital IQ signals, and the IQ demodulator further processes and analyzes the digital IQ signals to obtain recovered data.

[0054] The processing of the analog signal, the transmitting end filters the signal through a band-pass filter and then performs power amplification through a power amplifier, and the receiving end signal low-noise amplifier is filtered through a band-pass filter and then frequency-converted to an intermediate frequency (IF) signal. In order to ensure the synchronization of the channel data of the entire system, the system controls the input and output of each module through a global high-precision clock source 421.

[0055] S3, define h l as the channel gain of the useful signal from the transmitting end of the OAM mode antenna to the receiving end; as the channel gain of the kth (1≤k≤K) interference signal from the jammer to the receiving end; s I (t) as the corresponding kth interference signal; according to the useful signal transmitted by the transmitting end, combined with the channel gain h l , and the noise signal and the interference signal, the receiving signal of the OAM mode antenna receiving end is obtained, denoted as R x (t), specifically:

[0056]

[0057] In the formula, the useful signal transmitted from the transmitting end is denoted as T x (t); n(t) is the received additive white Gaussian noise; ε(t-t h ) is the impulse function at time t h .

[0058] S4, using the orthogonality between the orbital angular momentum modes, the transmitting end and the receiving end radiate spatial fields with the same mode, and the mode is matched, while for the interference signal, the mode is mismatched; and the signal is demodulated and filtered at the receiving end.

[0059] Specifically, in order to demodulate and recover the transmitted signal of the transmitting end (i.e. the useful signal transmitted by the transmitting end) at the receiving end, it is necessary to demodulate the received signal R x (t) by the Fourier transform operator. First, the complex signal after orthogonalization is weighted by a complex number, that is, the received signal is multiplied by to realize the phase shift of the received signal, so as to meet the mode matching filter, for the phase-shifted received signal; further, the phase-shifted received signal is demodulated and operated, specifically:

[0060]

[0061] wherein s(t) and t are defined as the transmitted modulated signal and the time variable, is the received noise corresponding to the demodulated signal.

[0062] For the interference signal, the mode is mismatched. The signal is demodulated and filtered at the receiving end.

[0063] Further, the interference signal strength is minimum, and the useful signal is maximum, and the SNR is maximum, as shown in equation (4), so that the receiving end is less affected by the jammer, and the symbol is easy to detect, and the receiving end signal MPSK-OAM demodulation is completed.

[0064]

[0065] wherein, is the received noise variance corresponding to the OAM mode l; E h is the transmitted power of the signal.

[0066] The test settings of the wideband anti-jamming communication system in this embodiment are as follows:

[0067] (1) System architecture

[0068] The tested OAM mode antenna is used to build a wideband anti-jamming communication system, as shown in Figure 4 , the system includes the following parts: dual-mode transmitter / receiver, jammer, host computer, high-precision clock source.

[0069] (2) System calibration

[0070] The power and phase consistency of the system transceiver link channel is an important prerequisite for transmitting OAM beams. The host computer defines the transmitting end USPR to work at 3.38 GHz, and the output signal power spectrum of the four channels is-47.55 dBm, -47.75 dBm, -47.15 dBm, and-47.80 dBm in turn. Taking the first channel as the reference, the power differences of the four channels are 0 dBm, -0.2 dBm, 0.4 dBm, and-0.25, respectively. Finally, the power difference is compensated to calibrate the transmitting channel power. Further, the receiving end power spectrum is tested. Taking the first channel as the reference, the power values received by the remaining channels are also obtained and compensated.

[0071] Then, the initial phase difference between the transceiver channels of the USRP-based system is calibrated. First, the initial phase difference between the receiving end channels is calibrated, and the phase difference of the four ports of the receiving end USRP is tested (taking the first channel as the reference). After compensating for the tested initial phase difference, the phase differences of the four ports are 0°, -1.01°, 2.93°, and-2.56°, respectively. Finally, taking the calibrated initial phase difference between the receiving end channels as the reference, the four ports of the transmitting / receiving end USRP are connected in turn, and the initial phase difference between the transmitting end channels is tested. The global variable is set to automatically compensate the phase difference between the four channels of the transmitting USRP, and the phase differences of the four ports are 0°, -1.3°, 4.2°, and-5.6°, respectively. At this point, the phase consistency of the four channels of the receiving USRP has been calibrated.

[0072] (3) Experimental parameter setting

[0073] The created interference signal with a jamming ratio of 10.4 dB and a bandwidth of BW=7.5 kHz is directed to the receiver of the same mode transceiver link at an incident angle of θ=15°, and the transceiver antenna distance is 1.5 m. The antenna operating frequency is 3.38 GHz, and the gain is 6.9 dBi. The signal is modulated based on QPSK modulation to complete QPSK-OAM joint modulation. The antenna transmits two modes at the same time, so the symbol rate of each mode is 2M Symbol / s, and the signal frequency band bandwidth BW=symbol rate*(1+α)=3 MHz, the IQ Symbol sample rate is 4MSymbol / s, and the filter roll-off coefficient α=0.5.

[0074] (4) Spatial mode matching filtering

[0075] Specifically, when there is no additional interference signal, the receiving end 4-way power of the transceiving l=+1 mode is:

[0076] Receiver P Rx1 =-65.4 dBm, P Rx2 =-68.5 dBm, P Rx3 =-67.5 dBm, PRx4 = -67.3 dBm, phase given 45°, 135°, -135°, -45°.

[0077] Transmitter P Tx = -18.9 dBm, P Tx = -21.9 dBm, P Tx = -20.9 dBm, P Tx = -20.7 dBm, phase given 45°, 135°, -135°, -45°.

[0078] Jammer P Ix = -8.4 dBm, bandwidth BW = 7.5 kHz, the useful signal and the jamming signal transmitted to the receiving end are respectively:

[0079]

[0080] In fact, the receiving end power and the transmitting end power can be related by the path loss formula, that is, The system receiving end has:

[0081]

[0082] Based on the above formula, the received signal After demodulation, the useful signal after filtering out the jamming signal can be obtained:

[0083]

[0084] The jamming signal without OAM mode is filtered out and suppressed. If there is no mode matching filter criterion, then the formula The jamming signal is difficult to effectively filter out and suppress.

[0085] It can be seen that at this time l = ±1, the receiving end constellation diagram has a smaller error in amplitude and phase compared to the ideal reference constellation point, and can detect the symbol. Figure 5 The constellation diagram of the receiving end when there is additional interference is shown, where the constellation diagrams of (e) and (f) show that when the transceiving mode l = 0 and the jamming signal appears, the received useful signal is weak, causing the amplitude and phase error of the signal to increase, the receiving end constellation diagram becomes difficult to detect the symbol, and the communication quality deteriorates.

[0086] In Figure 6 In order to better compare the anti-jamming performance, the same jamming signal hits the plane wave (i.e. l = 0 case) transceiving link, when SNR = 14.5 dB, the sample transmission error rate. When the system gain is properly adjusted, the SINR reaches 15.5 dB, and the BER = 5.46 x 10 -6and the sample transmission bit error rate of the plane wave (i.e. l=0) transceiving link is 3.02*10 -3 .

[0087] Overall, the application adopts the orbital angular momentum mode matching filter signal-to-noise ratio maximum criterion demodulation anti-interference technology, the system can generate modes with double orbital angular momentum at the same time, and the modes have orthogonality. The transceiver transmits the useful signal by radiating a carrier with the same mode, and the transceiver radiates the mode matching, enhances the reception of the useful signal, and the carrier mode is mismatched for external interference signals. At the receiving end, the useful signal is demodulated by the OAM mode demodulator, and then the interference signal is filtered out. Based on the OAM mode matching maximum SINR criterion, the receiving end receives the useful signal enhancement, and the received interference machine power is very small, so the SINR is large, so the receiving end is less affected by the interference machine, and the symbol is easy to detect, and finally the receiving end signal MPSK-OAM joint demodulation is completed.

[0088] Among them, the implementation of the receiving end OAM mode demodulator is to integrate the sampled useful signal with OAM modulation information, specifically: the real signal received by the array element containing OAM modulation information is converted into a complex signal by a certain orthogonal transformation, that is, the analytic signal of the real signal. The complex signal after orthogonalization is weighted by conjugate complex number and integrated to output the calculated signal power, and the system distinguishes the index of the matching mode with the highest output power to demodulate the signal. When a specific symbol s is sent, the s-th spatial matching mode will output the highest power among all spatial matching filters, and the mismatched mode will show orthogonality, which is 0. Therefore, the greater difference between the output power of the "matching mode" and the output power of the "mismatched mode" can result in lower bit error rate (BER) and stronger anti-noise ability.

[0089] The application takes the maximum signal-to-interference-and-noise ratio (SINR) as the criterion, and based on the maximum SINR criterion, without changing the traditional digital communication architecture, the proposed orbital angular momentum mode baseband modulation and demodulation is combined with the phase shift keying modulation (MPSK) to realize spatial field mode matching filter anti-interference and improve the anti-interference ability of the digital communication system. A pair of wideband characteristic modes with orthogonality is designed to realize the wideband characteristics of the uniform rectangular array antenna, improve the high isolation within and between array elements, and enable the system to support simultaneous multi-mode transmission and reception at the same frequency. The baseband digital phase shift architecture modulates the spatial electromagnetic wave field to generate orbital angular momentum modes based on the uniform rectangular array antenna, and performs mode matching filter demodulation at the receiving end to realize anti-interference transmission and reception communication of the digital communication system, and solves the alignment problem of the orbital angular momentum mode transmission and reception antenna and reduces the array size, providing an important foundation for realizing orbital angular momentum digital communication, effectively improving the data transmission rate of the communication system, and solving the interference problem.

[0090] The above is the preferred embodiment of the present application, it should be noted that for those skilled in the art, without departing from the principles of the present application, can also make several improvements and refinements, these improvements and refinements are also considered the scope of protection of the present application.

Claims

1. An OAM mode antenna of a uniform rectangular array, characterized in that, The first dielectric plate and a plurality of array elements arranged on the first dielectric plate, each array element comprising a right-handed metamaterial metal patch unit, a left-handed metamaterial metal patch unit, and a second dielectric plate; The second dielectric plate is constructed by a metamaterial hybrid dielectric resonator, and the right-handed metamaterial metal patch unit and the left-handed metamaterial metal patch unit are printed on the surface of the second dielectric plate; The left-handed metamaterial metal patch unit divides the surface of the second dielectric plate into a plurality of regions, and each region is printed with a right-handed metamaterial metal patch unit; outside the antenna operating frequency band, the equivalent permittivity ε e <0, the equivalent permeability u e inside the antenna operating frequency band, the equivalent permittivity ε e > relative permittivity ε r , the equivalent permeability u e > 0.

2. The OAM modal antenna of claim 1, wherein, The left-handed metamaterial metal patch unit is distributed in a cross shape on the surface of the second dielectric plate, dividing the surface of the second dielectric plate into four regions; there are four array elements, and the spacing between the array elements is 0.6 times the center frequency wavelength.

3. The OAM modal antenna of claim 1, wherein, The first dielectric plate is printed with a microstrip line structure for polarized feeding in each array element; the first dielectric plate is also provided with a first slot and a second slot for coupling to excite the selected array element broadband characteristic mode.

4. The OAM modal antenna of claim 3, wherein, The distribution of the first slot and the second slot on the first dielectric plate matches the distribution of the left-handed metamaterial metal patch unit on the surface of the second dielectric plate.

5. The OAM modal antenna of claim 1, wherein, The microstrip line structure for polarized feeding includes a "U" shaped microstrip line and an "M" shaped microstrip line.

6. An airfield digital modulation orbital angular momentum broadband anti-jamming communication system, characterized in that, The system comprises an interferer, a broadband communication system, and the OAM mode antenna of any one of claims 1-5; the broadband communication system is provided with a transceiving digital phase shift architecture, and the interferer is used for air interface transmission of co-frequency interference; The transceiving digital phase shift architecture comprises an OAM modulator and an OAM demodulator, which are used for realizing OAM mode antenna orbital angular momentum mode transceiving communication, generating an OAM vortex beam through baseband digital phase shift, and resisting the interference of the interferer, wherein the OAM modulator is arranged at the transmitting end of the broadband communication system, and the OAM demodulator is arranged at the receiving end of the broadband communication system.

7. The wideband anti-jamming communication system of claim 6, wherein, Transmitting and receiving digital phase shift architecture to achieve the required phase of the signal baseband for orbital angular momentum, each baseband signal of the transmitting end is multiplied by a complex number through the OAM modulator a is the feeding phase of the array element m a is the feeding phase of the array element The required phase amount and signal intensity of different orbital angular momentum modes are realized digitally.

8. The wideband anti-jamming communication system of claim 6, wherein, The broadband communication system comprises an encoder, an IQ modulator, a digital-to-analog converter, a low-pass filter, a mixer, a band-pass filter, a high-power amplifier, and a radio frequency interface arranged in sequence at the transmitting end, and a radio frequency interface, a low-noise amplifier, a band-pass filter, a mixer, a low-pass filter, an analog-to-digital converter, an IQ demodulator, and a decoder arranged in sequence at the receiving end; The OAM modulator is connected between the IQ modulator and the digital-to-analog converter, and the OAM demodulator is connected between the analog-to-digital converter and the IQ demodulator.

9. A method for spatial field digital modulation orbital angular momentum broadband anti-jamming communication, characterized in that, The system based on claim 6 is implemented, and the method comprises the following steps: S1, continuously transmitting an interference signal directed to the receiving end through the air interface at the transmitting end, wherein the transmitted interference signal has a preset interference-to-signal ratio; S2, processing the orbital angular momentum digital signal and the analog signal through the broadband anti-interference communication system; S3, define h l channel gain for a useful signal from a transmitting end to a receiving end of the OAM modal antenna; channel gain for the kth interference signal from the jammer to the receiving end;s I (t) is the corresponding kth interference signal; according to the useful signal transmitted by the transmitting end, combined with the channel gain h l 、 and the noise signal, the interference signal, to obtain the receiving signal of the receiving end of the OAM modal antenna; S4, using the orthogonality between the orbital angular momentum modes, the transmitting end radiates a spatial field with the same mode, and the modes are matched; for the interference signal, the modes are mismatched; and the receiving end filters the signal after demodulating the mode.

10. The wideband anti-jamming communication method of claim 9, wherein, The received signal R at the receiving end of the OAM mode antenna in step S3 x (t) is: where T x (t) is the useful signal transmitted from the transmitting end; n(t) is the received additive white Gaussian noise; ε(t - t h ) is the impulse function at time t h .

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