A millimeter-wave communication and sensing integrated transmission system

Abstract

The present invention belongs to the field of communication technologies, and specifically relates to a millimeter-wave communication and sensing integrated system based on frequency-division multiplexed LFM-OFDM signals. The system of the present invention includes a base station and a data center; the base station mainly includes an antenna, an electrical amplifier, a photodetector, a circulator, and a mixer; the antenna is used for transmitting and receiving millimeter-wave signals; the electrical amplifier is used for amplifying weak electrical signals; the photodetector is used for photoelectric conversion; the circulator controls signal transmission and reception; the mixer down-converts the signal to an intermediate frequency for easy acquisition; the data center mainly includes an input module, a light source, and an output module; the input module is used for generating information to be modulated; the laser serves as the light source; the output module is used for outputting the information demodulated by the demodulator. This system can simultaneously achieve the hardware combination of a millimeter-wave band communication system and a sensing system, can simultaneously generate broadband LFM signals to achieve high-precision sensing, and can also achieve high-speed communication.

Description

Technical Field

[0001] The present invention belongs to the field of communication technologies, and particularly relates to a millimeter-wave communication and sensing integrated transmission system based on frequency-division multiplexed LFM-OFDM signals. Background Art

[0002] With the development of technologies, communication and sensing integrated technologies have become very important in civilian and military applications, and radar and communication are developing in the direction of joint design. In the past, radar communication systems were generally independently developed and designed according to their respective functions and frequency bands, and there was a lack of communication between systems. Jointly designing a communication and sensing system can alleviate the spectrum scarcity problem brought about by the exponential growth of wireless devices and data traffic. At the same time, multiple radars need to be networked through communication technologies to quickly fuse a large amount of detection data. Especially in scenarios where space and power are extremely limited, such as vehicle-to-vehicle networks, flying ad-hoc networks, and convoys, there is a strong demand for the integration of radar and communication. Radar can also help communication discover surrounding signal sources faster, achieve more accurate channel estimation and beam alignment. It can be seen that integrating the communication function and the radar function into the same device can improve performance simultaneously, and has good development prospects in future 6G communication, driverless, multi-radar information fusion, etc. Summary of the Invention

[0003] The purpose of the present invention is to provide a millimeter-wave communication and sensing integrated transmission system with high signal transmission quality and low equipment cost, so as to achieve hardware resource sharing between communication devices and sensing devices, and achieve high-rate communication and high-precision sensing.

[0004] The millimeter-wave communication and sensing integrated transmission system provided by the present invention is based on frequency-division multiplexed LFM-OFDM signals, and includes a data center and a base station; wherein:

[0005] The data center includes:

[0006] A laser, denoted as (Laser), which provides an optical carrier signal;

[0007] A signal generator, which is used to generate frequency-division multiplexed LFM-OFDM signals and drive an optical modulator;

[0008] A group (two) of digital-to-analog converters (DACs), which are used to convert two orthogonal digital signals into analog signals to modulate an IQ modulator;

[0009] A group (two) of electrical amplifiers (EAs), which are used to amplify tiny electrical signals;

[0010] An in-phase / quadrature optical modulator (IQMOD), which uses two orthogonal digital signals to modulate an optical signal to achieve single-sideband signal generation;

[0011] An Optical Fiber Amplifier for amplifying the single-sideband optical signal output by an orthogonal modulator;

[0012] A circulator for distinguishing the bidirectional signal transmission directions in an optical fiber;

[0013] A photodetector for performing optoelectronic conversion on the received radar optical signal;

[0014] A signal acquisition device (such as an oscilloscope) for observing and storing the time information and frequency information of a signal;

[0015] A bidirectional optical fiber for bidirectionally transmitting optical signals between a data center and a base station;

[0016] The base station includes:

[0017] A circulator for distinguishing the signal transceiver relationship in an optical fiber;

[0018] An optical splitter that divides the LFM-OFDM signal optical signal into two paths. The first path signal is used as a transmission signal to propagate into free space, and the second path signal is used as a sensing reference signal to mix with the received signal at the receiving end to achieve pulse compression of the sensing signal;

[0019] An Optical Filter for filtering out the communication frequency bands in the optical signal and retaining the sensing frequency bands in the optical signal;

[0020] An electrical filter for filtering out the communication frequency bands in the communication sensing signal and retaining the sensing frequency bands;

[0021] A photodetector for achieving optoelectronic conversion through beat frequency, converting the integrated optical signal into an electrical signal for convenient transmission into free space;

[0022] A group (two) of electrical amplifiers for amplifying the transmitted electrical signal and the received electrical signal respectively;

[0023] An optical modulator for modulating the received sensing electrical signal onto an optical signal;

[0024] A transmitting antenna for transmitting the millimeter-wave frequency-division multiplexing LFM-OFDM signal generated after beat frequency;

[0025] A receiving antenna for acquiring the multiplexed signal reflected from a detection target.

[0026] The communication receiving end includes:

[0027] A receiving antenna for receiving communication signals;

[0028] A mixer for down-converting the received communication signal from the transmitting end;

[0029] An electrical filter for filtering out the sensed frequency bands in the communication sensing signal and retaining the communication frequency band;

[0030] An oscilloscope for observing the time-domain waveform and waveform diagram of the signal;

[0031] For the millimeter-wave communication and sensing integrated transmission system provided by the present invention, the ranging principle is as follows:

[0032] Assume that the starting frequency of the original LFM signal is f1, the frequency modulation slope is k, t represents the transmission time of the LFM signal, τ represents the time delay of the echo signal, and the frequency f of the transmitted signal corresponding to digital up-conversion F is:

[0033] f F = f1 + kt; (1)

[0034] Then the frequency f of the sensing signal at the receiving end S is:

[0035] f S = f1 + kt - kτ; (2)

[0036] The base station side couples the above-mentioned transmitted optical signal and the received optical single-sideband signal through the optical modulator, and through a photodetector PD2, beats out a frequency of kτ, and the distance corresponding to the detection target and the transmitting end is:

[0037]

[0038] By detecting the LFM signal transmitted to multiple targets, multiple different frequency peaks are obtained. Assume that the difference between the frequency peaks is Δf, then the measured target distance is:

[0039]

[0040] The corresponding distance resolution can be expressed as where c is the speed of light and B is the bandwidth of the LFM signal.

[0041] Thus, a high-precision ranging process can be achieved.

[0042] In the millimeter-wave communication and sensing integrated transmission system of the present invention, the digital frequency conversion method is used, and the up-conversion of the signal is completed through two digital complex mixers, and then two high-speed digital-to-analog converters are used to generate high-frequency millimeter-wave signals.

[0043] In the millimeter-wave communication and sensing integrated transmission system of the present invention, the communication signal is an OFDM signal, and the sensing signal is a linear frequency modulation continuous wave signal.

[0044] In the millimeter-wave communication and sensing integrated transmission system of the present invention, a single-sideband frequency division multiplexing LFM-OFDM signal is generated, improving the spectrum utilization efficiency, and a broadband LFM signal is generated to achieve high-precision ranging.

[0045] In the millimeter-wave communication and sensing integrated transmission system of the present invention, a high-rate communication module and a high-precision sensing module are integrated simultaneously, reducing the consumption of equipment between different systems and lowering the system cost. The communication module includes a data center, a base station, and a receiving end. The sensing module includes a data center and a base station.

[0046] For the millimeter-wave communication and sensing integrated transmission system of the present invention, the signal transmission flow is as follows:

[0047] (1) At the data center, a digital up-converted LFM-OFDM signal is generated by a waveform generator. Through two digital-to-analog converters and an electrical amplifier, the amplified signal is input into an optical quadrature modulator to modulate the optical carrier signal generated by the laser.

[0048] (2) The optical signal amplified by the optical fiber amplifier enters the bidirectional optical fiber through the circulator and is transmitted to the base station end.

[0049] (3) The optical signal received from the base station end is sent to the photodetector PD2 through the circulator for beating. The obtained electrical signal is sent to the signal acquisition device to observe and save the time-domain spectrum and frequency-domain spectrum of the signal.

[0050] (4) The LFM-OFDM signal received at the base station end is split into two paths by an optical splitter. The first path is directly sent to the photodetector PD1 for beating, amplified by an electrical amplifier, and then enters the free space through a horn antenna.

[0051] (5) After the received sensing signal passes through the receiving antenna and the electrical filter to filter out the communication signal, it drives the optical modulator to modulate the intensity of the second path of the signal that has been filtered out of the communication signal by the optical filter and split by the optical splitter, realizing the de-chirping function of the sensing module and the ranging of the communication signal; LFM signals are respectively transmitted to multiple targets, and the distance between the two targets is solved by the difference between the two obtained frequency peaks.

[0052] (6) At the communication receiving end, after wireless transmission and down-conversion, the communication signal is coherently demodulated, and the demodulation method is the same as the modulation method.

[0053] So far, the system has completed the functions of sensing ranging and communication.

[0054] Compared with the prior art, the present invention utilizes optical signal modulation to generate a frequency-division multiplexed LFM-OFDM signal in the millimeter-wave band, realizing the integration of the hardware resources of the sensing and communication devices. By integrating the two systems into one system, the system overhead is reduced and the signal quality is improved. At the same time, by placing the signal transceiver at the base station side and the signal processing end at the data center, the equipment cost of the base station segment is greatly reduced, and the scalability of the system is enhanced, laying a system foundation for future multiple-input multiple-output radar signal systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 FIG. 1 is an architecture diagram of a millimeter-wave communication and sensing integrated transmission system based on frequency-division multiplexed LFM-OFDM signals proposed by the present invention.

[0056] Reference numerals in the figure: 1 is a laser (Laser), 2 is an optical IQ modulator, 3 is an electrical amplifier (EA1), 4 is an electrical amplifier (EA2), 5 is a digital-to-analog converter (DAC1), 6 is a digital-to-analog converter (DAC2), 7 is an arbitrary waveform signal generator (AWG), 8 is an optical fiber amplifier (OFA), 9 is a circulator (Circulator1), 10 is a bidirectional optical fiber, 11 is a circulator (Circulator2), 12 is an optical splitter (PM-OC), 13 is a first photodetector (PD1), 14 is an electrical amplifier (EA3), 15 is a transmitting antenna (HA1), 16 is an optical modulator (MZM), 17 is an optical filter, 18 is an electrical amplifier (EA4), 19 is an electrical high-pass filter (HPF), 20 is a receiving antenna (HA2), 21 is a second photodetector (PD2), 22 is an oscilloscope, 23 is a receiving antenna (HA3), 24 is an electrical amplifier (EA5), 25 is a local oscillator (ELO), 26 is a mixer, 27 is an electrical low-pass filter (LPF), 28 is an oscilloscope. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0057] The present invention will be further described below with reference to the accompanying drawings.

[0058] The architecture of the millimeter-wave communication and sensing integrated transmission system of the present invention is shown in Figure 1 FIG. 1, where:

[0059] At the data center, the quadrature signal generated by the signal generator (7) is loaded onto the IQ modulator (2) through the digital-to-analog converters (5, 6) and the electrical amplifiers (3, 4) to perform carrier modulation on the optical carrier output by the laser (1), generating a single-sideband frequency-division multiplexed LFM-OFDM signal. Through an optical fiber amplifier (8), the amplified optical signal enters the circulator (9), and the circulator (9) controls the transmission direction of the signal. Then the signal enters the bidirectional optical fiber (10) for transmission and enters the circulator (11).

[0060] The optical signal received by the base station is transmitted back to the data center, enters the photoelectric detector PD2(21) for beat frequency to complete photoelectric conversion, and the electrical signal enters the oscilloscope(22) to observe and save the time-domain spectrum and frequency-domain spectrum of the signal.

[0061] At the base station end, the received optical signal is divided into two paths by an optical splitter(12); the first path enters the photoelectric detector PD1(13) for beat frequency, is amplified by an electrical amplifier(14), and then is transmitted into free space through the transmitting antenna(15). The received echo of the detection target is received by the receiving antenna(20), and the radar signal frequency band is retained through an electrical filter(19); the weak electrical signal is amplified by an electrical amplifier(18) and modulated by an electro-optic modulator(16), and the second optical signal separated by the optical splitter after passing through the optical filter(17) is used to de-chirp to achieve pulse compression of the radar signal; the modulated signal is transmitted back to the data center for processing after passing through the circulator(11) and the bidirectional optical fiber(10).

[0062] At the receiving end, the electrical signal is received by the receiving antenna(23), amplified by an electrical amplifier(24), and the local oscillator ELO(25) is used to down-convert the communication signal with the fixed-frequency signal generated by the mixer(26), and then is filtered by an electrical filter(27) and sent to the oscilloscope(28) to receive the signal. The demodulation method of the communication signal corresponds to the modulation method.

[0063] Those of ordinary skill in the art can understand that the above embodiments are specific embodiments for implementing the present invention, and in practical applications, various changes can be made in form and details without departing from the spirit and scope of the present invention.

Claims

1. A millimeter-wave communication and sensing integrated transmission system based on frequency-division multiplexing LFM-OFDM signals, characterized in that, It includes a data center, a base station, and a communication receiver; where: The data center includes: A laser for providing an optical carrier signal; A signal generator for generating a frequency-division multiplexed LFM-OFDM signal to drive an optical modulator; Two digital-to-analog converters for converting two orthogonal digital signals into analog signals to modulate an IQ modulator; Two electrical amplifiers for amplifying tiny electrical signals; An orthogonal optical modulator for modulating an optical signal using two orthogonal digital signals to achieve single-sideband signal generation; An optical fiber amplifier for amplifying the single-sideband optical signal output by the orthogonal modulator; A circulator for distinguishing the bidirectional signal transmission directions in an optical fiber; An optical detector for performing optoelectronic conversion on the received radar optical signal; A signal acquisition device for observing and saving the time information and frequency information of the signal; A bidirectional optical fiber for bidirectional transmission of optical signals between the data center and the base station; The base station includes: A circulator for distinguishing the signal transceiver relationship in an optical fiber; An optical splitter for splitting the LFM-OFDM signal optical signal into two paths. The first path signal is propagated into free space as a transmission signal, and the second path signal is used as a sensing reference signal to mix with the receiver signal to achieve pulse compression of the sensing signal; An optical filter for filtering out the communication part frequency band in the optical signal and retaining the sensing part frequency band in the optical signal; An electrical filter for filtering out the communication part frequency band in the communication sensing signal and retaining the sensing frequency band; An optical detector for performing optoelectronic conversion through beat frequency, converting the integrated optical signal into an electrical signal for convenient transmission to free space; Two electrical amplifiers for amplifying the transmitted electrical signal and the received electrical signal respectively; An optical modulator for modulating the received sensing electrical signal onto an optical signal; A transmitting antenna for transmitting the millimeter-wave frequency-division multiplexed LFM-OFDM signal generated after beat frequency; A receiving antenna for acquiring the multiplexed signal reflected from the detection target; The communication receiver includes: A receiving antenna for receiving communication signals; A mixer for performing down-conversion processing on the communication signal transmitted from the transmitting end; An electrical filter for filtering out the sensing part frequency band in the communication sensing signal and retaining the communication frequency band; An oscilloscope for observing the time-domain waveform and waveform diagram of the signal.

2. The integrated millimeter-wave communication and sensing transmission system according to claim 1, characterized in that, Use the digital frequency conversion method to complete the up-conversion of the signal through two digital complex mixers, and then use two high-speed digital-to-analog converters to generate high-frequency millimeter-wave signals.

3. The integrated millimeter-wave communication and sensing transmission system according to claim 2, characterized in that, The communication signal is an OFDM signal, and the sensing signal is a linear frequency modulation continuous wave signal.

4. The integrated millimeter-wave communication and sensing transmission system according to any one of claims 1-3, characterized in that The signal transmission flow direction of the system is: (1) At the data center, a digital up-converted LFM-OFDM signal is generated by a waveform generator. Through two digital-to-analog converters and electrical amplifiers, the amplified signal is input into the optical orthogonal modulator to modulate the optical carrier signal generated by the laser; (2) The optical signal amplified by the optical fiber amplifier enters the bidirectional optical fiber through the circulator and is transmitted to the base station end; (3) The optical signal received from the base station is sent into the photodetector PD2 through the circulator for beat frequency, and the obtained electrical signal is sent into the signal acquisition device to observe and save the time-domain spectrum and frequency-domain spectrum of the signal; (4) The LFM-OFDM signal received by the base station is split into two paths through the optical splitter. The first path is directly sent into the photodetector PD1 for beat frequency, amplified by the electrical amplifier and then enters the free space through the horn antenna; (5) After the received sensing signal is filtered by the receiving antenna and electrical filter to remove the communication signal, it drives the optical modulator to modulate the intensity of the second path signal that has passed through the optical filter to remove the communication signal and is split by the optical splitter, realizing the de-chirping function of the sensing module and the ranging of the communication signal; LFM signals are respectively transmitted to multiple targets, and the distance between the two targets is solved by the difference between the two obtained frequency peaks; (6) At the communication receiving end, after wireless transmission and down-conversion, the communication signal is coherently demodulated, and the demodulation method is the same as the modulation method; So far, the system has completed sensing ranging and communication.

5. The integrated millimeter-wave communication and sensing transmission system according to claim 4, characterized in that, The principle of the system for ranging is: Assume that the starting frequency of the original LFM signal is ƒ1 and the frequency modulation slope is k , t represents the transmission time of the LFM signal, τ represents the time delay of the echo signal, and the transmitted signal frequency ƒ corresponding to digital up-conversion F is: ƒ F = ƒ1+ kt (1); Then the frequency ƒ of the received end's sensed signal S is as follows: ƒ S = ƒ1+ kt - kτ (2); The base station side couples the above-mentioned transmitted optical signal with the received optical single-sideband signal through the optical modulator, and through a photodetector PD2, beats out a frequency of kτ , and the distance between the corresponding detection target and the transmitting end is: （3）； By detecting multiple targets by transmitting LFM signals, multiple different frequency peaks are obtained. Assuming that the difference between the frequency peaks is Δƒ, the target spacing is measured as: （4）； The corresponding range resolution is expressed as , where c is the speed of light, B is the bandwidth of the LFM signal; High-precision ranging is thus achieved.

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