Modulation and demodulation method based on array antenna rotation electromagnetic wave orbital angular momentum

Abstract

A modulation and demodulation method based on array antenna rotation electromagnetic wave orbital angular momentum relates to the technical field of wireless transmission, and comprises the following steps: a signal generator generates a sinusoidal signal of a required radio frequency point; the phase encoder generates a feed phase of the required orbital angular momentum according to the number of array antenna arrays; the array antenna generates a rotary orbital angular momentum electromagnetic wave with a corresponding digital modulation mode according to the feed phase of the phase encoder; the receiving antenna is used for receiving part of energy of the rotating orbital angular momentum electromagnetic wave propagated in the free space; the radio frequency unit is used for down-converting a radio frequency signal received by the receiving antenna to an intermediate frequency; and the demodulation unit 203 decodes and recovers the original baseband signal. According to the invention, the software and hardware structures are simplified, the system complexity is reduced, modulation and demodulation based on the rotating electromagnetic wave orbital angular momentum are realized, and long-distance transmission of the electromagnetic wave orbital angular momentum becomes possible.

Description

Technical Field

[0001] The present invention relates to the field of wireless transmission technology, and in particular to a modulation and demodulation method based on orbital angular momentum of rotating electromagnetic waves of array antennas. Background Art

[0002] The orbital angular momentum (OAM) of electromagnetic waves has received extensive attention and in-depth research in the academic community since it was theoretically derived by Allen et al. using Maxwell's equations in 1992 and experimentally verified in 1994. The angular momentum of electromagnetic waves consists of two parts: spin angular momentum and orbital angular momentum. Spin angular momentum corresponds to the polarization of electromagnetic waves. It has two degrees of freedom, left and right. Since it was proposed in the early 1950s, it has developed rapidly. Today, research and products on polarization are very mature. As a new degree of freedom, the orbital angular momentum of electromagnetic waves moves in a spiral around the propagation axis.

[0003] Electromagnetic waves have used amplitude as a means of information transmission since the time of Marconi. Among them, frequency indicates how fast the amplitude changes, while phase indicates when the amplitude changes. The transmission method of using electromagnetic wave amplitude as an information carrier has not changed to this day. What exactly is electromagnetic wave? People's understanding of it has only remained in the Marconi era. However, orbital angular momentum, as another typical physical quantity of electromagnetic waves, provides people with a new perspective to study and develop electromagnetic waves. It has potential applications in many aspects. In terms of transmission, different orbital angular momenta of electromagnetic waves are orthogonal to each other. By multiplexing different orbital angular momenta and transmitting or receiving through the same aperture, the transmission spectrum efficiency can be greatly improved. In astronomy, electromagnetic waves with orbital angular momentum can be used to detect the vortex characteristics of the electromagnetic layer. In terms of particle manipulation, light waves with orbital angular momentum have the effect of optical spanners and can realize the rotation of particles. Therefore, different from conventional electromagnetic waves, orbital angular momentum provides a new dimension for electromagnetic waves and a new perspective for people to understand electromagnetic waves. It must have great application value in transmission and detection.

[0004] Since there is an energy singularity in the electromagnetic wave beam with orbital angular momentum, its energy is distributed in a circular ring. When transmitting over long distances, the radius of the energy ring will become larger and larger, and the receiving end cannot receive all the electromagnetic wave energy, but can only receive part of the electromagnetic wave energy. The transmitting end rotates the electromagnetic wave with orbital angular momentum, converting the electromagnetic wave with different orbital angular momentum at the transmitting end into electromagnetic waves with different frequency deviations at the receiving end, thereby achieving long-distance and high spectral efficiency transmission. Based on this dynamic rotational frequency shift characteristic, it is of great significance to design corresponding modulation and demodulation methods. Summary of the invention

[0005] The purpose of the present invention is to solve the problems raised in the above background technology, and then proposes a modulation and demodulation method based on the orbital angular momentum of rotating electromagnetic waves of array antennas.

[0006] The technical solution adopted by the present invention to solve the technical problem is:

[0007] A modulation and demodulation method based on orbital angular momentum of rotating electromagnetic waves of an array antenna comprises the following steps:

[0008] S1, the signal generator generates a sinusoidal signal at the required RF frequency;

[0009] S2, the phase encoder generates the required orbital angular momentum feeding phase according to the number of array antenna elements; the array antenna generates a rotating orbital angular momentum electromagnetic wave with a corresponding digital modulation method according to the feeding phase of the phase encoder;

[0010] S3, the receiving antenna is used to receive part of the energy of the rotating orbital angular momentum electromagnetic wave propagating in free space; the radio frequency unit is used to down-convert the radio frequency signal received by the receiving antenna to an intermediate frequency; and the demodulation unit 203 decodes and restores the original baseband signal.

[0011] In step S2, the feeding phase of each array antenna element is controlled, and the feeding phase of the subsequent array antenna element replaces the feeding phase of the previous array antenna element in turn, so that the feeding phase of the array rotates in a clockwise or counterclockwise direction, thereby generating a corresponding frequency shift at the receiving end. Thereafter, the feeding phase rotation rate, rotation direction and starting feeding position are controlled according to the required digital modulation method, thereby directly generating the required digital modulation method on the RF antenna.

[0012] Furthermore, the phase rotation encoding module calculates the feeding phase of each array in the array antenna, and then rotates the feeding phase at a rotation speed r. The feeding phase is then fed into each array of the array antenna in turn through the transmission line. The array converts the guided wave in the transmission line into an electromagnetic wave in the free space and radiates it, thereby generating a rotating orbital angular momentum.

[0013] In step S1, the bit information of the baseband data source is sent to the modulator after being compressed by the source encoder and the channel encoder adds error correction information. The modulator changes the amplitude, frequency or phase of the carrier according to the encoded baseband data, and the RF unit up-converts the intermediate frequency signal to the required RF frequency.

[0014] In step S3, when the demodulation unit decodes and recovers the original baseband signal, the demodulator strips off the intermediate frequency carrier and uses the OFDM signal demodulation method to recover the encoded baseband data. The channel decoder then completes the error correction and error detection of the source data, and the source decoder then completes the source decoding, thereby recovering the original baseband signal and completing a transmission process.

[0015] Furthermore, the rotational orbital angular momentum electromagnetic wave includes one or more of light waves, microwaves, millimeter waves and terahertz waves.

[0016] Furthermore, the array antenna and the receiving antenna are one of a horn antenna, a parabolic antenna, a Cassegrain antenna, a patch antenna, and an array antenna.

[0017] In step S2, for an array antenna with N elements, an electromagnetic wave with an orbital angular momentum of l is generated, and the feeding phase of each element is:

[0018]

[0019] Among them, φ n is the feeding phase of the nth array.

[0020] Furthermore, the feeding phase of the nth oscillator at time t is:

[0021]

[0022] in, Indicates the feeding phase of the nth oscillator at time t, [n+rt] N It represents n+rt modulo N, r represents the rotation rate, N represents the number of array antenna elements, and l represents the number of OAM modes.

[0023] Furthermore, the feed phase rotation rate and orbital angular momentum mode number have the following relationship with the generated signal frequency shift:

[0024] Δf=l·r,

[0025] Among them, Δf is the corresponding frequency shift, l is the orbital angular momentum mode number, and r is the rotation speed.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention can be widely used in wireless transmission systems in the optical wave, microwave, millimeter wave and terahertz bands. First, the electromagnetic waves with different orbital angular momentum at the transmitting end are converted into electromagnetic waves with different frequency deviations at the receiving end by rotation, and then the rotation rate, rotation direction and feeding starting point of the feeding phase are controlled, so as to directly realize the required digital modulation mode on the radio frequency antenna, and the existing receiver structure with the corresponding digital demodulator does not need to be modified, which simplifies the software and hardware structure, reduces the system complexity, realizes modulation and demodulation based on the orbital angular momentum of the rotating electromagnetic wave, makes the long-distance transmission of the orbital angular momentum of the electromagnetic wave possible, and has the characteristics of large transmission capacity, flexibility and convenience. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1It is a structural schematic diagram of a modulation and demodulation method based on orbital angular momentum of rotating electromagnetic waves of an array antenna according to an embodiment of the present invention;

[0028] Figure 2 A schematic diagram of a frequency shift keying (FSK) structure based on the orbital angular momentum of a rotating electromagnetic wave of an array antenna according to a specific embodiment of the present invention;

[0029] Figure 3 A schematic diagram of a phase shift keying (PSK) structure based on the orbital angular momentum of a rotating electromagnetic wave of an array antenna according to a specific embodiment of the present invention;

[0030] Figure 4 The figure is a schematic diagram of an orthogonal frequency division multiplexing (OFDM) structure of the orbital angular momentum of rotating electromagnetic waves based on an array antenna according to a specific embodiment of the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The present invention is further described in combination with the drawings and embodiments:

[0032] like Figure 1 As shown, the wireless transmission system 10 includes: a signal modulation subsystem 100 and a signal demodulation subsystem 200. The signal modulation subsystem 100 includes: a signal generator 101, a phase encoder 102, and an array antenna 103; the signal demodulation subsystem 200 includes: a receiving antenna 201, a radio frequency unit 202, and a demodulation unit 203.

[0033] A modulation and demodulation method based on orbital angular momentum of rotating electromagnetic waves of an array antenna comprises the following steps:

[0034] S1, signal generator 101 generates a sinusoidal signal at a required radio frequency point;

[0035] S2, the phase encoder 102 generates the required orbital angular momentum feeding phase according to the number of array antenna elements; the array antenna 103 generates a rotating orbital angular momentum electromagnetic wave with a corresponding digital modulation method according to the feeding phase of the phase encoder 102;

[0036] S3, the receiving antenna 201 is used to receive part of the energy of the rotating orbital angular momentum electromagnetic wave propagating in free space; the radio frequency unit 202 is used to down-convert the radio frequency signal received by the receiving antenna to an intermediate frequency; and then the demodulation unit 203 decodes and restores the original baseband signal.

[0037] In step S2, the feeding phase of each array antenna element is controlled, and the feeding phase of the subsequent array antenna element replaces the feeding phase of the previous array antenna element in turn, so that the feeding phase of the array rotates in a clockwise or counterclockwise direction, thereby generating a corresponding frequency shift at the receiving end. Thereafter, the feeding phase rotation rate, rotation direction and starting feeding position are controlled according to the required digital modulation method, thereby directly generating the required digital modulation method on the RF antenna.

[0038] Furthermore, the phase rotation encoding module 102 calculates the feeding phase of each array in the array antenna 103, and then rotates the feeding phase at a rotation speed r. The feeding phase is then fed into each array of the array antenna 103 in sequence through the transmission line. The array converts the guided wave in the transmission line into an electromagnetic wave in the free space and radiates it, thereby generating a rotating orbital angular momentum.

[0039] like Figure 2 Shown is the schematic diagram of a wireless transmission system based on the orbital angular momentum of rotating electromagnetic waves (taking the millimeter wave band as an example).

[0040] In step S1, the bit information of the baseband data source 1011 is sent to the modulator 1014 after being compressed by the source encoder 1012 and the channel encoder 1013 adds error correction information. The modulator changes the amplitude, frequency or phase of the carrier according to the encoded baseband data, and the RF unit 1015 up-converts the intermediate frequency signal to the required RF frequency.

[0041] In step S3, when the demodulation unit 203 decodes and recovers the original baseband signal, the demodulator 2031 strips off the intermediate frequency carrier and uses the OFDM signal demodulation method to recover the encoded baseband data. Thereafter, the channel decoder 2032 completes the error correction and error detection of the source data, and then the source decoder 2033 completes the source decoding, thereby recovering the original baseband signal 2034 and completing a transmission process.

[0042] Furthermore, the rotational orbital angular momentum electromagnetic wave includes one or more of light waves, microwaves, millimeter waves and terahertz waves.

[0043] Furthermore, the modulation and demodulation method based on the orbital angular momentum of rotating electromagnetic waves of array antennas of the embodiments of the present invention can be widely used in wireless transmission systems in optical wave, microwave, millimeter wave and terahertz bands. First, the electromagnetic waves with different orbital angular momentum at the transmitting end are converted into electromagnetic waves with different frequency deviations at the receiving end by rotation, and then the rotation rate, rotation direction and feeding starting point of the feeding phase are controlled, so as to directly realize the required digital modulation mode on the radio frequency antenna, and the existing receiver structure with the corresponding digital demodulator does not need to be modified, which simplifies the software and hardware structure, reduces the system complexity, realizes the modulation and demodulation based on the orbital angular momentum of rotating electromagnetic waves, makes the long-distance transmission of the orbital angular momentum of electromagnetic waves possible, and has the characteristics of large transmission capacity, flexibility and convenience.

[0044] Furthermore, in the signal demodulation subsystem 200, signal demodulation can be completed by only using a conventional receiver structure with a corresponding digital demodulator.

[0045] In one embodiment of the present invention, the transmitting antenna element and the receiving antenna are any one of horn antennas, parabolic antennas, Cassegrain antennas, patch antennas, array antennas, and the like.

[0046] In summary, large-capacity and high-spectral-efficiency transmission can be achieved based on the orbital angular momentum of electromagnetic waves. However, since the electromagnetic wave beam with orbital angular momentum is distributed in a ring shape, the radius of its energy ring will become larger and larger during long-distance transmission, and the receiving end cannot receive all the electromagnetic wave energy, but can only receive part of the electromagnetic wave energy. By rotating the orbital angular momentum of the electromagnetic wave at the transmitting end, and then generating a corresponding frequency shift at the receiving end, the electromagnetic waves with different orbital angular momentum at the transmitting end are converted into electromagnetic waves with different frequency deviations at the receiving end through rotation, so that electromagnetic wave long-distance transmission can be achieved. Based on the design of the corresponding modulation and demodulation method of rotating the orbital angular momentum of the electromagnetic wave, the embodiment of the present invention first rotates the orbital angular momentum of the electromagnetic wave by rotating the feeding phase of the array antenna, and then controls the rotation rate, rotation direction and starting position of the array feeding phase, and directly realizes the required digital modulation on the RF antenna; the receiving end directly adopts the corresponding digital demodulation method to complete the signal demodulation.

[0047] The system of the embodiment of the present invention converts different orbital angular momentum into different receiving frequencies by rotating the orbital angular momentum of electromagnetic waves, thereby reducing the difficulty of receiving and making large-capacity and long-distance transmission based on the orbital angular momentum of electromagnetic waves possible.

[0048] like Figure 3 As shown, for a circular array antenna with N elements, an electromagnetic wave with orbital angular momentum of l is generated, and the feeding phase of each element is:

[0049]

[0050] Among them, φ n is the feeding phase of the nth array.

[0051] In order to rotate the orbital angular momentum of the electromagnetic wave on the antenna array, it is necessary to calculate the feeding phase of each oscillator according to formula (1), and rotate the feeding phase of the oscillator along the array ring in sequence. The principle is as follows Figure 3 As shown. Assume that there are now 8 oscillators, labeled 1 to 8. According to formula (1), the feeding phase of each oscillator is calculated to be 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°. The corresponding relationship between the feeding phase and the oscillator is: 0°→1, 45°→2, 90°→3, 135°→4, 180°→5, 225°→6, 270°→7, 315°→8. When the initial feeding phase of each oscillator remains unchanged, the conventional electromagnetic wave orbital angular momentum is generated. When the initial feeding phase of the oscillator is rotated in sequence, that is, 0°→2, 45°→3, 90°→4, 135°→5, 180°→6, 225°→7, 270°→8, 315°→1, and so on, the rotation of the electromagnetic wave orbital angular momentum can be achieved. According to this rotation mode, the feeding phase of the nth vibrator at time t is:

[0052]

[0053] in, Indicates the feeding phase of the nth oscillator at time t, [n+rt] N It represents n+rt modulo N, r represents the rotation rate, N represents the number of array antenna elements, and l represents the number of OAM modes.

[0054] like Figure 4 As shown in the figure, the signal frequency shift generated under different rotation speeds and different orbital angular momentum. The rotation speed and orbital angular momentum mode number have the following relationship with the generated signal frequency shift:

[0055] Δf=l·r, (3)

[0056] Among them, Δf is the corresponding frequency shift, l is the orbital angular momentum mode number, and r is the rotation speed.

[0057] like Figure 4As shown, it is a schematic diagram of an array antenna multiplexing transmission system based on the orbital angular momentum of rotating electromagnetic waves (taking the millimeter wave band as an example). The signal generator module 101 generates multiple transmission signals at the same time, and each transmission signal passes through a corresponding phase rotation encoding module 102 to generate a corresponding rotational electromagnetic wave orbital angular momentum signal. The OAM modes of the circular arrays with different radii in the module 103 are all different, and the multiple signals are transmitted through their respective array antennas 103; after propagation in free space, at the receiving end, the antenna 201 receives the multiple signals at the same time, and then sends them to the signal receiver module 202 to separate the multiple signals, and then 203 demodulates and decodes them to restore the original baseband signal.

[0058] In the array antenna wireless transmission system based on the orbital angular momentum of rotating electromagnetic waves of the embodiment of the present invention, information data first passes through a signal transmitter, which completes the encoding and modulation of the baseband data, and then sends the radio frequency signal to a phase rotation encoding module through a data line to generate a feeding phase, which is fed into each array through a feeder line, thereby generating an electromagnetic wave with rotating orbital angular momentum, which propagates through free space to reach a receiving end, which receives part of the energy of the electromagnetic wave with an antenna, and then sends it to a signal receiver, which completes down-conversion, demodulation and decoding of the radio frequency signal, and finally recovers the baseband signal, thereby realizing large-capacity and long-distance transmission of electromagnetic waves in free space, reducing the difficulty of receiving, and greatly improving the spectrum efficiency of transmission.

[0059] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of the present invention is defined by the attached claims and their equivalents.

Claims

1. A modulation and demodulation method based on orbital angular momentum of rotating electromagnetic waves of array antenna, characterized in that: The following steps are involved: S1, the signal generator generates a sinusoidal signal at the required RF frequency; S2, the phase encoder generates the required orbital angular momentum feeding phase according to the number of array antenna elements; the array antenna generates a rotating orbital angular momentum electromagnetic wave with a corresponding digital modulation method according to the feeding phase of the phase encoder; S3, the receiving antenna is used to receive part of the energy of the rotating orbital angular momentum electromagnetic wave propagating in free space; The radio frequency unit is used to down-convert the radio frequency signal received by the receiving antenna to an intermediate frequency; the demodulation unit 203 decodes and restores the original baseband signal.

2. The modulation and demodulation method based on orbital angular momentum of rotating electromagnetic waves of array antenna according to claim 1, characterized in that: In step S2, the feeding phase of each array antenna element is controlled, and the feeding phase of the subsequent array antenna element replaces the feeding phase of the previous array antenna element in turn, so that the feeding phase of the array rotates in a clockwise or counterclockwise direction, thereby generating a corresponding frequency shift at the receiving end. Thereafter, the feeding phase rotation rate, rotation direction and starting feeding position are controlled according to the required digital modulation method, thereby directly generating the required digital modulation method on the RF antenna.

3. The modulation and demodulation method based on orbital angular momentum of rotating electromagnetic waves of array antenna according to claim 2, characterized in that: The phase rotation encoding module calculates the feeding phase of each array in the array antenna, and then rotates the feeding phase at a rotation speed r. The feeding phase is then fed into each array of the array antenna in turn through the transmission line. The array converts the guided wave in the transmission line into an electromagnetic wave in the free space and radiates it, thereby generating a rotating orbital angular momentum.

4. A modulation and demodulation method based on orbital angular momentum of rotating electromagnetic waves of array antenna according to claim 2 or 3, characterized in that: In step S1, the bit information of the baseband data source is sent to the modulator after being compressed by the source encoder and the channel encoder adds error correction information. The modulator changes the amplitude, frequency or phase of the carrier according to the encoded baseband data, and the RF unit up-converts the intermediate frequency signal to the required RF frequency.

5. The modulation and demodulation method based on orbital angular momentum of rotating electromagnetic waves of array antenna according to claim 4, characterized in that: In step S3, when the demodulation unit decodes and recovers the original baseband signal, the demodulator strips off the intermediate frequency carrier and uses the OFDM signal demodulation method to recover the encoded baseband data. The channel decoder then completes the error correction and error detection of the source data, and the source decoder then completes the source decoding, thereby recovering the original baseband signal and completing a transmission process.

6. The modulation and demodulation method based on orbital angular momentum of rotating electromagnetic waves of array antenna according to claim 1, characterized in that: The rotation orbital angular momentum electromagnetic wave includes one or more of light waves, microwaves, millimeter waves and terahertz waves.

7. The modulation and demodulation method based on orbital angular momentum of rotating electromagnetic waves of array antenna according to claim 1, characterized in that: The array antenna and the receiving antenna are one of a horn antenna, a parabolic antenna, a Cassegrain antenna, a patch antenna, and an array antenna.

8. The modulation and demodulation method based on orbital angular momentum of rotating electromagnetic waves of array antenna according to claim 3 is characterized in that: In step S2, for an array antenna with N elements, an electromagnetic wave with an orbital angular momentum of l is generated, and the feeding phase of each element is: Among them, φ n is the feeding phase of the nth array.

9. The modulation and demodulation method based on orbital angular momentum of rotating electromagnetic waves of array antenna according to claim 8, characterized in that: The feeding phase of the nth oscillator at time t is: in, Indicates the feeding phase of the nth oscillator at time t, [n+rt] N It represents n+rt modulo N, r represents the rotation rate, N represents the number of array antenna elements, and l represents the number of OAM modes.

10. The modulation and demodulation method based on orbital angular momentum of rotating electromagnetic waves of array antenna according to claim 3, characterized in that: The feed phase rotation rate and orbital angular momentum mode number are related to the generated signal frequency shift as follows: Δf=l·r, Among them, Δf is the corresponding frequency shift, l is the orbital angular momentum mode number, and r is the rotation speed.

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