CN115941052A - A quadruple-frequency communication-aware integrated transmission system based on a single modulator - Google Patents

Abstract

The invention belongs to the technical field of communication, and particularly relates to a quadruple frequency communication perception integrated transmission system based on a single modulator. The system comprises a sending end, a communication receiving end and a perception receiving end: the transmitting end comprises a polarization division multiplexing Mach-Zehnder modulator, an external cavity laser, a waveform generator, a polarization controller, a polarization beam splitter, a fiber Bragg grating, an optical coupler, a photoelectric detector, a transmitting antenna and the like; the communication receiving end comprises a receiving antenna, a mixer and an oscilloscope; the perception receiving end comprises a receiving antenna, two mixers and an oscilloscope; the system adopts the time division multiplexing LFM-MQAM signal, which is equivalent to inserting the block pilot frequency, can generate a broadband LFM signal and improve the ranging precision; outputting an optical signal with an even-order sideband dominating position through the fiber Bragg grating, and assisting the photoelectric detector to beat frequency to generate a high-frequency millimeter wave signal; the communication and sensing function sharing device avoids hardware resource waste and improves device integration level.

Description

A quadruple frequency communication sensing integrated transmission system based on a single modulator

Technical Field

The present invention belongs to the field of communication technology, and in particular relates to a quadruple frequency communication perception integrated transmission system based on a single modulator.

Background Art

With the continuous evolution of emerging services such as autonomous driving, drones, immersive extended reality, and industrial Internet, future data-driven intelligent applications will break the boundaries between the three major application scenarios of enhanced mobile broadband, low-latency and high-reliability communication, and ultra-large-scale machine-type communication in the existing fifth-generation mobile communication system. The sixth-generation mobile communication system will be divided into more detailed scenarios and need to meet multi-dimensional extreme performance requirements. In the past communication methods, communication and perception functions existed independently. Due to the lack of feedback information brought by the perception function, the quality of communication often could not be received in real time at the sending end, which had a certain negative impact on efficiency. If the communication part and the perception part of the system can be combined to a certain extent, and the communication and perception functions can be integrated on one device, the communication quality of the system can be greatly improved, and power consumption and hardware costs can be reduced. There is a good development space in the future application of 6G technology. Future intelligent applications not only require more extreme communication performance, but also need to use positioning, detection, imaging and other technologies to perceive the environment in real time. It also needs to use ultra-wideband communication to transmit perception information to widely distributed computing nodes for intelligent processing, decision-making and control of perception information, and finally achieve ideal end-to-end performance. 6G is no longer just a simple bit transmission channel centered on humans, but also an intelligent and simplified network that can sense and connect everything and has inherent intelligence for the full interconnection of humans, machines and objects.

Summary of the invention

The purpose of the present invention is to provide a quadruple frequency communication and perception integrated transmission system based on a single modulator with compact structure, simple operation, strong frequency multiplication capability, and flexible and adjustable frequency, so as to realize hardware resource sharing between communication equipment and perception equipment, and realize high-speed communication and high-precision perception.

The quadruple frequency communication and perception integrated transmission system based on a single modulator provided by the present invention comprises a transmitting end, a communication receiving end, and a perception receiving end: wherein:

(1) The sending end includes:

An external cavity laser (ECL), the light wave emitted by the laser is injected into the PDM-MZM modulator, and is divided into two paths by the built-in 3-dB coupler of the PDM-MZM, and enters the two sub-modulators (MZM1 and MZM2) of the PDM-MZM respectively. One part is modulated by the sub-modulator MZM1 working at the maximum bias point to produce even-order sidebands; the other part is modulated by the sub-modulator MZM2 working at the minimum bias point to de-chirp the echo signal received by the sensing end;

An arbitrary waveform generator (AWG) for generating time-division multiplexed LFM and MQAM signals to drive the sub-modulator MZM1 of the optical modulator PDM-MZM;

A polarization division multiplexing Mach-Zehnder modulator (PDM-MZM), which consists of two sub-modulators (MZM1 and MZM2), a 90-degree polarization rotator (PR) and a polarization beam combiner (PBC); MZM1 modulates the electrical signal generated by the AWG onto the optical carrier, and MZM2 de-chirps the echo signal after down-conversion; PBC synthesizes the two signals into a polarization multiplexed signal for output;

a polarization controller (PC) for controlling the polarization state of the PDM-MZM output signal;

A polarization beam splitter (PBS) for splitting the optical signal modulated by PDM-MZM and passing through the polarization controller into two paths;

a fiber Bragg grating (FBG) to suppress the optical carrier of the signal output by the MZM-1 and output ±2nd and ±4th order sideband optical signals;

Two optical couplers, denoted as a first optical coupler PM-OC1 and a second optical coupler PM-OC2, wherein the first optical coupler PM-OC1 is used to split the optical signal after PDM-MZM modulation and optical carrier suppression by the fiber Bragg grating into two paths, and the second optical coupler PM-OC2 is used to couple the downlink optical signal separated by the polarization beam splitter with the -4th order sideband optical signal selected by the wavelength selective switch (WSS);

Two photodetectors (PDs) are used to complete the photoelectric conversion by beat frequency. In the transmitting part, the beat frequency generates the time-division multiplexed LFM and MQAM signals in the millimeter wave band. For the sensing part, the electrical signal generated by the beat frequency of PD2 is used for de-chirping.

a wavelength selective switch (WSS) to select the -4th order sideband for use as a reference for the radar;

A transmitting antenna transmits the millimeter-wave time-division multiplexing LFM and MQAM signals generated after the frequency beating.

(2) Communication receiving end, including:

a communication receiving antenna for receiving millimeter wave signals;

A mixer for down-converting the communication signal received from the transmitter;

An oscilloscope is used to detect the received communication signal and observe the signal time domain waveform and spectrum diagram.

(3) Perception receiving end, including:

A sensing receiving antenna for acquiring the signal reflected from the receiving end;

Two mixers, one is used to convert the received reflected signal frequency to a lower frequency for down-conversion processing, and the other is used to down-convert the signal after PD2 beat frequency processing to facilitate oscilloscope sampling;

An oscilloscope is used to detect the received perception signal and observe the signal time domain waveform and spectrum diagram.

The millimeter wave communication perception integrated transmission system provided by the present invention performs perception ranging principle as follows:

Assuming the sampling frequency is _fs , the frequency modulation slope is k, τ represents the delay of the echo signal, and c is the speed of light, the instantaneous frequency _fN of the W-band LFM signal is:

f _N =4f _s +4kt; (1)

At the sensing demodulation end, the frequency of the de-modulated signal output by the second photodetector PD2 is 4kτ. Move the target to another position, obtain another de-modulated signal with a frequency of 4kτ′, calculate the frequency difference Δf between the two positions, and obtain the distance difference L between the two positions as:

In the present invention, the time-division multiplexed LFM-MQAM signal is used, which is equivalent to inserting a block pilot, and can generate a broadband LFM signal, thereby improving the ranging accuracy;

In the present invention, the optical signal with even-order sidebands as the dominant part is outputted by the fiber Bragg grating, so as to assist the first photodetector PD1 to generate a high-frequency millimeter wave signal by beating the frequency.

In the present invention, the communication signal is a multi-carrier MQAM signal, and the perception signal is a linear frequency modulation signal.

In the present invention, the communication and perception functions share equipment, thus avoiding the waste of hardware resources.

The present invention also relates to a communication perception integrated transmission method based on LFM-MQAM signals based on the above transmission system, and the specific steps are:

At the transmitting end, the light wave emitted by the external cavity laser is injected into the modulator PDM-MZM, and is divided into two paths by the built-in 3-dB coupler of the PDM-MZM, and enters the two sub-modulators (MZM1 and MZM2) of the PDM-MZM respectively. Among them, one part is modulated by the first sub-modulator MZM1 working at the maximum bias point to generate even-order sidebands, and then combined with the other part of the light wave modulated by the second sub-modulator MZM2 working at the minimum bias point by the built-in polarization beam combiner of the optical modulator to output. The first optical coupler PM-OC1 is used to divide the optical carrier dominated by the ±2nd and ±4th order sidebands output by the FBG into upper and lower paths. The upper optical carrier output by the first optical coupler PM-OC1 is beat by the first photodetector PD1 to generate high-frequency millimeter waves for communication functions, and the lower optical carrier output by the first optical coupler PM-OC1 is used as a part of the reference signal for sensing the radar at the receiving end through the wavelength selection switch;

The first optical coupler (PM-OC1) separates the upper sideband signal and the lower sideband signal of the Bragg grating output signal. The upper sideband signal is used for communication and perception after subsequent processing, and the lower sideband signal is used as a reference optical signal for the ranging receiving end.

The upper sideband optical signal output by the first optical coupler PM-OC1 enters the first photodetector PD1 to complete the beat frequency;

The first photodetector PD1 completes the photoelectric conversion by beating the frequency to obtain the LFM-MQAM signal in the millimeter wave band, and thus the generation of the communication sensing signal has been completed;

The above signal is transmitted through the antenna and sent into the wireless channel;

At the communication receiving end, after wireless reception by the communication receiving end, the communication signal is coherently demodulated, and the demodulation method is consistent with the modulation method;

At the sensing receiving end, the reflected ranging signal is received through the antenna;

The down-converted signal obtained by mixing with the local oscillator signal is used to drive the sub-modulator MZM2 of the PDM-MZM modulator working at the minimum bias point, and the -4-order sideband optical signal output by the WSS is coupled by the second optical coupler PM-OC2;

The second photodetector PD2 receives the coupling signal output by the second optical coupler PM-OC2, obtains a frequency peak by beating the frequency, transmits LFM signals to the two targets respectively, calculates the difference between the two frequency peaks, and solves the distance between the two targets.

At this point, the system has completed the perception, ranging and communication functions.

Compared with the prior art, the present invention is based on a single modulator and a single ECL to generate time-division multiplexed LFM and MQAM signals in the millimeter wave band using optical heterodyne beat frequency, thereby realizing the integration of hardware resources of perception and communication equipment, improving the integration of hardware, and also meeting the trend that higher-frequency communication signal bands will gradually overlap with radar signal spectrum bands in the future.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a diagram of the architecture of the quadruple frequency communication sensing integrated transmission system based on a single modulator of the present invention.

The numbers in the figure are: 1 is a laser generator ECL, 2 is an arbitrary waveform generator AWG, 3 is a sub-modulator MZM1 of the optical modulator PDM-MZM, 4 is a sub-modulator MZM2 of the optical modulator PDM-MZM, 5 is a 90-degree polarization rotator PR of the optical modulator PDM-MZM, 6 is a polarization beam combiner PBC of the optical modulator PDM-MZM, 7 is a polarization controller PC, 8 is a polarization beam splitter PBS, 9 is a fiber Bragg grating FBG, 10 is a first optical coupler PM-OC1, 11 is the first photodetector PD1, 12 is the transmitting antenna HA1, 13 is the communication receiving antenna HA2, 14 is the local oscillator ELO1, 15 is the first mixer, 16 is the oscilloscope OSC, 17 is the wavelength selection switch WSS, 18 is the second mixer, 19 is the local oscillator ELO2, 20 is the sensing receiving antenna HA3, 21 is the target to be measured, 22 is the second optical coupler PM-OC2, 23 is the second photodetector PD2, 24 is the third mixer, and 25 is the oscilloscope OSC.

DETAILED DESCRIPTION

The present invention will be further described below in conjunction with the accompanying drawings.

The quadruple frequency communication perception integrated transmission system based on a single modulator provided by the present invention has an architecture as shown in FIG1 , wherein:

At the transmitting end, based on the LFM of time division multiplexing, the MQAM signal is generated by MATLAB programming. Since the MQAM signal of the communication function is frequency-doubled, the MQAM signal is pre-coded at this stage and then uploaded to the arbitrary waveform generator (2). The intermediate frequency signal generated by the arbitrary waveform generator (2) drives the first sub-modulator MZM1 (3) of the optical modulator to modulate the optical carrier output by the laser (1) to generate even-order sidebands. The polarization beam combiner PBC (6) of the optical modulator PDM-MZM synthesizes the two signals of the two sub-modulators into a polarization multiplexing signal output. The polarization multiplexing signal output by the polarization beam combiner PBC (6) is divided into two paths by the polarization beam splitter (8) after the polarization state is controlled by the polarization controller (7). One path is suppressed by the fiber Bragg grating (9) and then further divided into two paths by the first optical coupler PM-OC1 (10). After the upper path passes through the first photodetector PD1 (11) for frequency beat, it is transmitted through a suitable transmitting antenna (12).

At the communication receiving end, the millimeter wave signal is received by the communication receiving antenna (12) in the W band used for the communication function. The fixed frequency signal generated by the local oscillator ELO1 (14) is down-converted by the first mixer (15), the demodulation method corresponds to the modulation method, the MQAM signal is restored by a series of digital signal processing, and the signal is received by the oscilloscope (16).

At the sensing receiving end, the echo signal from the target (21) is received by the sensing receiving antenna (20), and the signal is down-converted at the second mixer (18) and the local oscillator ELO2 (19). At this time, the down-converted signal is transmitted back to the optical modulator PDM-MZM to drive the second sub-modulator MZM2 (4) to de-chirp, and then passes through the 90-degree polarization rotator PR (5) and the signal output by the first sub-modulator MZM1 (3) through the polarization beam combiner PBC (6) to synthesize the polarization multiplexing signal output. The downlink optical signal separated by the first optical coupler PM-OC1 (10) at the transmitting end is selected by a wavelength selection switch (17) to obtain a -4-order sideband optical signal, and then coupled with the downlink signal separated by the polarization beam splitter (8) at the second optical coupler PM-OC2 (22), and then the photoelectric conversion is completed through the beat frequency of the second photodetector PD2 (23), and the received signal is detected by the OSC oscilloscope (25) after down-conversion through the third mixer (24).

Those skilled in the art will appreciate that the above embodiments are specific examples for implementing the present invention, and in actual applications, various changes may be made thereto in form and detail without departing from the spirit and scope of the present invention.

Claims (7)

1. A quadruple frequency communication and perception integrated transmission system based on a single modulator, characterized by comprising a transmitting end, a communication receiving end, and a perception receiving end: wherein: The sending end comprises: A polarization division multiplexing Mach-Zehnder modulator (PDM-MZM), the modulator (PDM-MZM) is composed of a first sub-modulator (MZM1), a second sub-modulator (MZM2), a 90-degree polarization rotator (PR) and a polarization beam combiner (PBC); the first sub-modulator (MZM1) is used to modulate the electrical signal generated by the waveform generator (AWG) onto the optical carrier, and the second sub-modulator (MZM2) is used to de-chirp the echo signal after down-conversion; the polarization beam combiner (PBC) synthesizes the two signals into a polarization multiplexed signal for output; An external cavity laser (ECL), the light wave emitted by the external cavity laser is injected into the polarization division multiplexing Mach-Zehnder modulator (PDM-MZM), and is divided into two paths by the built-in 3-dB coupler of the modulator (PDM-MZM), respectively entering the first sub-modulator (MZM1) and the second sub-modulator (MZM2) of the modulator (PDM-MZM), among which one part is modulated by the sub-modulator (MZM1) working at the maximum bias point to generate even-order sidebands; the other part is modulated by the second sub-modulator (MZM2) working at the minimum bias point to de-chirp the echo signal received by the sensing end; a waveform generator (AWG) for generating time-division multiplexed LFM and MQAM signals to drive the first optical sub-modulator (MZM1); a polarization controller (PC) for controlling the polarization state of the output signal of the modulator (PDM-MZM); a polarization beam splitter (PBS) for splitting the optical signal modulated by the modulator (PDM-MZM) and passing through the polarization controller into two paths; a fiber Bragg grating (FBG) for suppressing an optical carrier of a signal output by the first sub-modulator (MZM-1) and outputting ±2nd-order and ±4th-order sideband optical signals; Two optical couplers, namely a first optical coupler (PM-OC1) and a second optical coupler (PM-OC2), wherein the first optical coupler (PM-OC1) is used to split the optical signal modulated by a modulator (PDM-MZM) and suppressed by a fiber Bragg grating (FBG) into two paths; the second optical coupler (PM-OC2) is used to couple the downlink optical signal separated by a polarization beam splitter (PBS) with the -4th order sideband optical signal selected by a wavelength selective switch (WSS); Two photodetectors (PD), namely a first photodetector (PD1) and a second photodetector (PD2), are used to beat the frequency to complete the photoelectric conversion; wherein, in the transmitting part, the first photodetector (PD1) beats the frequency to generate a time-division multiplexed LFM, MQAM signal in the millimeter wave frequency band; for the sensing part, the electrical signal generated by the beat of the second photodetector (PD2) is used for de-chirping; a wavelength selective switch (WSS) to select the -4th order sideband for use as a reference for the radar; A transmitting antenna transmits the millimeter-wave time-division multiplexing LFM and MQAM signals generated after the beat frequency; The communication receiving end comprises: a communication receiving antenna for receiving millimeter wave signals; A mixer for down-converting the communication signal received from the transmitter; An oscilloscope, used to detect the received communication signal and observe the signal time domain waveform and spectrum; The sensing receiving end comprises: A sensing receiving antenna for acquiring the signal reflected from the receiving end; Two mixers, one for converting the received reflected signal frequency to a lower frequency for down-conversion processing, and the other for down-converting the signal after the beat frequency of the second photodetector (PD2) for oscilloscope sampling; An oscilloscope is used to detect the received perception signal and observe the signal time domain waveform and spectrum diagram. 2. According to the quadruple frequency communication perception integrated transmission system of claim 1, it is characterized in that the time-division multiplexed LFM-MQAM signal is used, which is equivalent to inserting a block pilot, and can generate a broadband LFM signal, thereby improving the ranging accuracy. 3. The quadruple frequency communication perception integrated transmission system according to claim 1 is characterized in that a light signal dominated by even-order sidebands is output by a fiber Bragg grating to assist the photodetector (PD) in beating frequency to generate a high-frequency millimeter wave signal. 4. The quadruple frequency communication and perception integrated transmission system according to claim 1 is characterized in that the communication signal is a multi-carrier MQAM signal and the perception signal is a linear frequency modulation signal. 5. The quadruple frequency communication and perception integrated transmission system according to claim 1 is characterized in that the communication and perception functions share equipment to avoid waste of hardware resources. 6. The quadruple frequency communication perception integrated transmission system according to claim 1, characterized in that the working process is as follows: At the transmitting end, the light wave emitted by the external cavity laser is injected into the modulator (PDM-MZM), and is divided into two paths by the built-in 3-dB coupler of the modulator (PDM-MZM), and enters two sub-modulators (MZM1 and MZM2) respectively; one part is modulated by the first sub-modulator (MZM1) working at the maximum bias point to generate even-order sidebands, and the other part is modulated by the second sub-modulator (MZM2) working at the minimum bias point; the two modulated light waves are synthesized and output by the built-in polarization beam combiner (PBC) of the optical modulator, and the first optical coupler (PM-OC1) divides the optical carrier dominated by the ±2nd and ±4th order sidebands output by the fiber Bragg grating (FBG) into upper and lower paths, and the upper optical carrier output by the first optical coupler (PM-OC1) is beat by the first photodetector (PD1) to generate high-frequency millimeter waves for communication functions, while the lower optical carrier output by the first optical coupler (PM-OC1) is used as part of the reference signal for sensing the radar at the receiving end through the wavelength selective switch; The first optical coupler (PM-OC1) separates the upper sideband signal and the lower sideband signal of the Bragg grating output signal. The upper sideband signal is used for communication and perception after subsequent processing, and the lower sideband signal is used as a reference optical signal for the ranging receiving end. The upper sideband optical signal output by the first optical coupler (PM-OC1) enters the first photodetector (PD1) to complete the beat frequency; The first photodetector (PD1) completes the photoelectric conversion by beating the frequency to obtain the LFM-MQAM signal in the millimeter wave band, thus completing the generation of the communication sensing signal; The above signal is transmitted through the transmitting antenna and sent into the wireless channel; At the communication receiving end, after wireless reception by the communication receiving end, the communication signal is coherently demodulated, and the demodulation method is consistent with the modulation method; At the sensing receiving end, the reflected ranging signal is received by the sensing receiving antenna; The down-converted signal obtained by mixing with the local oscillator signal drives the second sub-modulator (MZM2) operating at the minimum bias point, and is coupled with the -4th order sideband optical signal output by the wavelength selective switch (WSS) by the second optical coupler (PM-OC2); The second photodetector (PD2) receives the coupling signal output by the second optical coupler (PM-OC2), obtains a frequency peak by beating the frequency, transmits LFM signals to the two targets respectively, calculates the difference between the two frequency peaks, and can solve the distance between the two targets; At this point, the perception, ranging and communication functions have been completed. 7. The quadruple frequency communication sensing integrated transmission system according to claim 6, characterized in that the sensing ranging principle is as follows: Assuming the sampling frequency is _fs , the frequency modulation slope is k, τ represents the delay of the echo signal, and c is the speed of light, the instantaneous frequency _fN of the W-band LFM signal is: f _N =4f _s +4kt; (1) At the sensing demodulation end, the frequency of the de-modulated signal output by the second photodetector (PD2) is 4kτ. Move the target to another position, obtain another de-modulated signal with a frequency of 4kτ′, calculate the frequency difference Δf between the two positions, and obtain the distance difference L between the two positions as:

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