Photon time-stretching coherent radar chip

Abstract

A photon time-stretch coherent radar chip includes a femtosecond pulse generating part, a radar transmitting part and a radar receiving part. The femtosecond pulse generating part generates high-repetition-frequency, wide-spectrum femtosecond pulses; the radar transmitting part is used to transmit radar signals, and the radar receiving part is used to receive and process radar echo signals. The present invention adopts high-repetition-frequency, wide-spectrum femtosecond pulses based on an on-chip Kerr optical microcavity as a carrier light source, and utilizes the high repetition-frequency characteristics of the femtosecond pulses. The radar transmission can generate high-frequency broadband microwave signals through heterodyne beat frequency. The high repetition-frequency and wide-spectrum characteristics of the femtosecond pulses are utilized to increase the coverage of the radar receiving aperture, and at the same time reduce the dispersion amount required for photon time stretching in radar reception, so that the radar can use integrated dispersion devices for time stretching, thereby realizing the monolithic integration of the photon time-stretch coherent radar system.

Description

Technical Field

[0001] The invention belongs to the technical field of integrated photons, and in particular is a photon time-stretching coherent radar chip. Background Art

[0002] Radar is an important means of target detection and identification. The key to determining radar functions, detection accuracy, response time and other important performance is that the radar can generate, receive and process broadband microwave signals. Photonic technology has the advantages of high speed, broadband and anti-electromagnetic interference, which can effectively overcome the "bandwidth bottleneck" of electronic devices and become a key enabling technology for improving radar performance. Pulse radar technology has the advantages of long detection distance, strong anti-interference ability and shared transmitting and receiving antennas, while coherent technology can accumulate the pulse echoes returned in a single radar scan to improve detection sensitivity, and obtain the Doppler frequency shift of the target to detect moving targets. On the other hand, photon integration technology can reduce the size, power consumption and cost of radar systems, and enhance programmability and reconfigurability. Therefore, the coherent photon radar chip that organically combines broadband photon processing technology, pulse radar technology, coherent technology and photon integration technology has the advantages of broadband cross-band, real-time high precision, multi-function integration and system integration. It belongs to the next generation of radar chips and has important application potential in national defense and civilian fields such as small satellites, drones, robots and autonomous driving.

[0003] At present, the transmitter of coherent photon radar mainly generates broadband microwave signals through heterodyne beat frequency, and the receiver mainly receives broadband echo signals by optical channelization, optical analog-to-digital conversion and photon time stretching. In comparison, the photon time stretching method can reduce the frequency and bandwidth of broadband echo signals by multiples, and the back-end only needs to use low-speed ADC to process broadband echo signals, which is one of the important implementation schemes of coherent photon radar (i.e. photon time stretching coherent radar, W. Zou, et al. All-optical central-frequency-programmable and bandwidth-tailorable radar. Scientific reports, 2016, 6(1): 1-8.). However, the current photon time stretching coherent radar requires a high repetition rate and wide spectrum femtosecond light source to provide femtosecond pulses, and the receiver needs a dispersive medium with a large dispersion to achieve time stretching of broadband echo signals. The generation of mode-locked stretched pulse solitons based on on-chip Kerr optical microresonator (Kerr optical microcavity for short) is expected to solve the problem of high repetition rate and wide spectrum femtosecond light source. First, the on-chip Kerr optical microcavity has a length ranging from centimeters to micrometers, and can generate mode-locked pulses with repetition frequencies ranging from 10 GHz to several THz. Second, by managing the dispersion of the Kerr optical microcavity, the laser mode-locking works in the dispersion management mechanism. At this time, the stretched pulse solitons generated have the characteristics of large spectral width and narrow pulse width. Third, the on-chip Kerr optical microcavity preparation process is compatible with CMOS and can be integrated with other optoelectronic devices to realize the photon time-stretch coherent radar system chip. However, there are currently no on-chip integrated large dispersion waveguides or dispersion devices that meet the application requirements of receivers. In contrast, other key components of the photon time-stretch coherent radar, such as electro-optical modulators, couplers, photodetectors, etc., have been integrated. Therefore, innovating the system architecture of the photon time-stretch coherent radar and reducing the demand for on-chip integrated dispersion devices are the core keys to achieve full integration and truly practical application of the photon time-stretch coherent radar. Summary of the invention

[0004] The purpose of the present invention is to propose a photon time-stretch coherent radar chip in view of the deficiencies of the prior art. By using high repetition rate and wide spectrum femtosecond pulses based on the on-chip Kerr optical micro-resonator mode-locked output as the radar light source, the radar can generate high-frequency broadband microwave signals through heterodyne beat frequency, and improve the coverage range of the radar receiving aperture, while reducing the dispersion required for photon time-stretch reception, so that the radar can use integrated dispersion devices for time stretching, thereby realizing the monolithic integration of the photon time-stretch coherent radar system. The photon time-stretch coherent radar chip of the present invention belongs to the next generation of radar chips, and has important applications in national defense and civilian fields such as small satellites, drones, robots and autonomous driving.

[0005] The technical solution of the present invention is as follows:

[0006] A photon time-stretch coherent radar chip is characterized in that it includes a femtosecond pulse generating part, a radar transmitting part and a radar receiving part, wherein the femtosecond pulse generating part includes a pump laser, an on-chip Kerr optical microcavity and a first optical splitter; the radar transmitting part includes a signal generator, a first electro-optic modulator, a first photodetector, a power amplifier and a transmitting antenna; the radar receiving part includes a first dispersive medium, a receiving antenna, a low-noise amplifier, a second electro-optic modulator, a second dispersive medium, an optical amplifier, a second optical splitter, a second photodetector, a first analog-to-digital converter, a third dispersive medium, a third photodetector, a second analog-to-digital converter and a digital signal processor (hereinafter referred to as DSP); the connection relationship of the above components is as follows:

[0007] The pump laser is connected to the on-chip Kerr optical microcavity. The optical signal output by the on-chip Kerr optical microcavity is divided into two paths by the first optical splitter: one path of light enters the first electro-optical modulator as a carrier, and then passes through the first photodetector and the first power amplifier in sequence before entering the transmitting antenna. The signal generator is connected to the radio frequency input end of the first electro-optical modulator. The other path of light separated by the first optical splitter enters the first dispersive medium of the radar receiving part, and then passes through the second electro-optical modulator, the second dispersive medium, and the optical amplifier in sequence, and is divided into two paths by the second optical splitter: one path passes through the second photodetector and the first analog-to-digital converter before entering the DSP, and the other path passes through the third dispersive medium, the third photodetector and the second analog-to-digital converter in sequence before entering the DSP. The receiving antenna is connected to the radio frequency input end of the second electro-optical modulator after passing through the low-noise amplifier.

[0008] The high repetition rate and wide spectrum femtosecond pulse generation part is a femtosecond light source based on the on-chip Kerr optical microcavity. Since the Kerr optical microcavity laser mode locking works in the dispersion management mechanism, the output stretched pulse soliton is a femtosecond pulse with high repetition rate and wide spectrum characteristics, which can meet the application requirements of photon time stretching coherent radar chip. The first electro-optical modulator in the radar transmitting part loads the baseband radar signal generated by the signal generator onto the optical carrier through the electro-optical modulation effect, and then generates a microwave signal of the required frequency and bandwidth through the heterodyne beat frequency of the first photodetector. After amplification by the power amplifier, the transmitting antenna transmits the microwave signal. In the radar receiving part, after the optical carrier pulse is photon time stretched by the first dispersive medium, the formed receiving window covers the entire radar detection distance. The specific implementation needs to satisfy the following formula:

[0009] B·D1≥Trep (1)

[0010]

[0011] Among them, T rep Represents the repetition period of the light pulse output by the femtosecond pulse generation part, B is the pulse spectrum width, D1 represents the dispersion coefficient of the first section of the dispersive medium; D2 represents the dispersion coefficient of the second section of the dispersive medium. The first formula ensures that within the pulse repetition period, the product of the spectrum width of the light pulse output by the femtosecond pulse generation part and the dispersion coefficient can cover the entire detection distance, and M in the second formula is the stretching factor achieved by the designed photon time stretching link. The radar echo signal received by the receiving antenna is amplified by the low-noise amplifier, and then modulated by the second electro-optical modulator and loaded on the time-stretched optical carrier pulse output by the first dispersive medium. After the optical carrier pulse loaded with the radar echo signal passes through the second dispersive medium, the echo signal is broadened due to the photon time stretching effect. After the broadened optical carrier pulse is amplified by the optical amplifier, it is divided into two paths by the second optical splitter, one of which is directly converted into an electrical signal through the second photodetector, and the other is firstly passed through the third dispersive medium for further photon time stretching, and then converted into an electrical signal through the third photodetector. Finally, the two electrical signals are respectively subjected to analog-to-digital conversion by the first analog-to-digital converter and the second analog-to-digital converter, and then enter the DSP for digital processing. Since the radar reception utilizes the high repetition rate and wide spectrum characteristics of the radar, the dispersion amount required for photon time stretching is reduced. The first dispersive medium, the second dispersive medium and the third dispersive medium can all be implemented by using existing on-chip integrated dispersive waveguides or devices, laying a foundation for the monolithic integration of photon time stretching coherent radar.

[0012] The pump laser may be, but is not limited to, a solid-state laser, a semiconductor laser, a fiber laser, and various types of on-chip light sources, and the laser form may be, but is not limited to, single-frequency continuous light, multi-wavelength laser, and pulsed laser.

[0013] The on-chip Kerr optical microcavity may be in the form of, but not limited to, microrings, microdisks, microspheres, microrods, etc. The waveguide mode may be, but not limited to, spatial radiation mode, substrate radiation mode, and guided mode; the waveguide material may be, but not limited to, magnesium fluoride, silicon, silicon dioxide, silicon nitride, III-V compounds, lithium niobate, gallium aluminum arsenide, sulfides, fluorides, etc.; the microring waveguide structure may be, but not limited to, strip waveguides, ridge waveguides, strip groove waveguides, T-shaped, L-shaped waveguides, etc.

[0014] The optical splitter may be, but is not limited to, an optical power splitter or an optical coupler.

[0015] The electro-optic modulator is used to load microwave signals, and may be, but not limited to, an optical intensity modulator or a phase modulator.

[0016] The photodetector is used to convert light signals into electrical signals, and may be, but not limited to, a PIN tube or an APD.

[0017] The optical amplifier is used to amplify the optical signal, and may be, but not limited to, an erbium-doped waveguide amplifier, a semiconductor optical amplifier or a Raman amplifier.

[0018] The dispersive medium is used to perform photon time stretching on the pulse, and may be, but is not limited to, on-chip integrated silicon-based, SiO2, silicon nitride, lithium niobate, tellurite, sulfide, fluoride and other optical waveguides or dispersive devices.

[0019] The transmitting / receiving antenna is used to transmit / receive microwave signals, and may be, but not limited to, a horn antenna, a phased array antenna or a half-wave dipole antenna.

[0020] The signal generator is used to generate a baseband radar signal, and may be, but not limited to, a DDS, an arbitrary waveform generator or a light-generated microwave.

[0021] The femtosecond pulse generating part is used to generate high repetition frequency wide spectrum pulses; the radar transmitting part is used to generate high-frequency, broadband microwave signals and transmit them; the radar receiving part is used to receive high-frequency, broadband echo signals and obtain characteristic information such as the distance of the target to be measured;

[0022] The advantages of the present invention mainly include:

[0023] (1) The present invention adopts high repetition rate and wide spectrum femtosecond pulses based on on-chip Kerr optical microcavity as carrier light source. By utilizing the high repetition rate characteristics of femtosecond pulses, radar transmission can generate high-frequency broadband microwave signals through heterodyne beat frequency. By utilizing the high repetition rate and wide spectrum characteristics of femtosecond pulses, the dispersion required for photon time stretching in radar reception is reduced, and the coverage range of radar receiving aperture is improved, laying a foundation for the monolithic integration of photon time stretching coherent radar.

[0024] (2) The fabrication processes of all devices in the photonic time-stretch coherent radar chip are compatible with CMOS processes and can achieve monolithic integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the structure of the photon time-stretch coherent radar chip of the present invention.

[0026] Figure 2 Schematic diagram of the radar signal transmission and reception principle. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0028] The terms "first", "second", "third", "fourth", etc. in the specification and claims of this application and the above drawings are used to distinguish different objects rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but may include steps or units that are not listed.

[0029] See also Figure 1 , Figure 1The schematic diagram of the structure of the photon time-stretch coherent radar chip of the present invention shows that a photon time-stretch coherent radar chip includes a femtosecond pulse generating part 1, a radar transmitting part 2 and a radar receiving part 3. The femtosecond pulse generating part 1 includes a pump laser 1-1, a Kerr optical microcavity 1-2 and an optical splitter 1-3; the radar transmitting part 2 includes a signal generator 2-1, a first electro-optical modulator 2-2, a first photodetector 2-3, a power amplifier 2-4 and a transmitting antenna 2-5; the The radar receiving part 3 includes a first dispersive medium 3-1, a receiving antenna 3-2, a low noise amplifier 3-3, a second electro-optical modulator 3-4, a second dispersive medium 3-5, an optical amplifier 3-6, a second optical splitter 3-7, a second photodetector 3-8, a first analog-to-digital converter 3-9, a third dispersive medium 3-10, a third photodetector 3-11, a second analog-to-digital converter 3-12 and a digital signal processor (hereinafter referred to as DSP) 3-13; the pump laser 1-1 and the on-chip Kerr The optical microcavity 1-2 is connected, and the optical signal output by the on-chip Kerr optical microcavity 1-2 is divided into two paths by the first optical splitter 1-3: one path of light enters the first electro-optical modulator 2-2 as a carrier, and then passes through the first photodetector 2-3 and the first power amplifier 2-4 in sequence before entering the transmitting antenna 2-5. The signal generator 2-1 is connected to the RF input end of the first electro-optical modulator 2-2. The other path of light separated by the first optical splitter 1-3 enters the first dispersive medium 3-1 of the radar receiving part 3, and then passes through the second electro-optical modulator 3-4, the second dispersive medium 3-5, and the optical amplifier 306 in sequence, and is divided into two paths by the second optical splitter 3-7: one path passes through the second photodetector 3-8 and the first analog-to-digital converter 3-9 and then enters the DSP3-13, and the other path passes through the third dispersive medium 3-10, the third photodetector 3-11 and the second analog-to-digital converter 3-12 in sequence before entering the DSP3-13. The receiving antenna 3-2 is connected to the radio frequency input end of the second electro-optical modulator 3-2 after passing through the low noise amplifier 3-3.

[0030] The specific working principle of the present invention is as follows: the high repetition rate and wide spectrum femtosecond pulse generation part is a femtosecond light source based on the on-chip Kerr optical microcavity 1-2. Since the on-chip Kerr optical microcavity 1-2 laser mode locking works in the dispersion management mechanism, the output stretched pulse soliton is a femtosecond pulse with high repetition rate and wide spectrum characteristics, which can meet the application requirements of photon time stretching coherent radar chip. The first electro-optical modulator 2-2 in the radar transmitting part 2 loads the baseband radar signal generated by the signal generator 2-1 onto the optical carrier through the electro-optical modulation effect, and then generates a microwave signal of the required frequency and bandwidth through the heterodyne beat frequency of the first photodetector 2-3. After amplification by the power amplifier 2-4, the transmitting antenna 2-5 transmits the microwave signal. After the optical carrier pulse in the radar receiving part 3 is photon time stretched by the first dispersive medium 3-1, the formed receiving window covers the entire radar detection distance. The radar echo signal received by the receiving antenna is amplified by the low noise amplifier, and then modulated by the second electro-optical modulator 3-4 and loaded on the time-stretched optical carrier pulse output by the first dispersive medium 3-1. After the optical carrier pulse loaded with the radar echo signal passes through the second dispersive medium 3-5, the echo signal is widened due to the photon time stretching effect. After the widened optical carrier pulse is amplified by the optical amplifier, it is divided into two paths by the second optical splitter 3-7, one of which is directly converted into an electrical signal through the second photodetector 3-8, and the other is firstly passed through the third dispersive medium 3-10 for further photon time stretching, and then converted into an electrical signal through the third photodetector 3-11. Finally, the two electrical signals are respectively converted from analog to digital by the first analog-to-digital converter 3-9 and the second analog-to-digital converter 3-12, and then enter the DSP for digital processing. Since radar reception utilizes the high repetition rate and wide spectrum characteristics of radar, the amount of dispersion required for photon time stretching is reduced. Dispersive medium 1, dispersive medium 2 and dispersive medium 3 can all be implemented using existing on-chip integrated dispersive waveguides or devices, laying the foundation for the monolithic integration of photon time stretch coherent radar.

[0031] Embodiment 1 (High-resolution photon time-stretch coherent radar chip)

[0032] Its main parameters are as follows:

[0033] The pump laser 1-1 is an on-chip integrated semiconductor laser, and the laser form is single-frequency continuous light.

[0034] The on-chip Kerr optical microcavity 1-2 adopts a microring structure, has a length of 2 cm, a guided mode waveguide mode, a waveguide material of silicon nitride, and a strip waveguide structure. The microring laser mode locking works in a dispersion management mechanism, and the output stretched pulse soliton has a repetition frequency of 10 GHz, a spectral width of 100 nm, and a pulse width of 200 fs.

[0035] The optical splitter 1-3 is an optical power splitter.

[0036] The electro-optical modulators 2-2 and 3-4 are light intensity modulators.

[0037] The photoelectric detectors 2-3, 3-8 and 3-11 are PIN tubes.

[0038] The optical amplifiers 3-6 are semiconductor optical amplifiers.

[0039] The dispersive media 3-1, 3-5, and 3-10 use on-chip integrated optical waveguides.

[0040] The transmitting antenna 2-5 / receiving antenna 3-2 adopts a phased array antenna.

[0041] The signal generator 2-1 is an arbitrary waveform generator.

[0042] Figure 2 The schematic diagram of the radar signal transmission and reception principle of this embodiment is shown in FIG. The first electro-optic modulator 2-2 in the radar transmitting part 2 loads the linear frequency modulation signal with a bandwidth of 4 GHz generated by the signal generator 2-1 (DDS can be used) onto the optical carrier through the electro-optic modulation effect, and then the heterodyne beat frequency of the first photodetector 2-3 with a bandwidth greater than 12 GHz generates a microwave signal covering the X-band with a bandwidth of 4 GHz, which is amplified by the power amplifier 2-4 and radiated by the transmitting antenna 2-5.

[0043] After the optical carrier pulse in the radar receiving part 3 is time-stretched by the first dispersive medium 3-1 with a dispersion of 1 ps / nm, the formed receiving window covers the entire radar detection distance. The specific implementation needs to satisfy the following formula:

[0044] B·D1≥T rep (1)

[0045]

[0046] Among them, T rep represents the repetition period of the passive mode-locked laser output light pulse, B is the pulse spectrum width, D1 represents the dispersion coefficient of the first dispersive medium; D2 represents the dispersion coefficient of the second dispersive medium. The first formula ensures that within the pulse repetition period, the product of the filter bandwidth and the dispersion coefficient can cover the entire detection distance, and the second formula M is the stretch factor achieved by the designed photon time stretch link.

[0047] The radar echo signal with a bandwidth of 4 GHz and covering the X-band received by the receiving antenna 3-2 is amplified by the low noise amplifier 3-3, and then modulated by the second electro-optical modulator 3-4 and loaded on the optical carrier pulse after time stretching by the first dispersive medium 3-1. After the optical carrier pulse loaded with the radar echo signal passes through the second dispersive medium 3-5 with a dispersion amount of 3 ps / nm, the echo signal is widened due to the photon time stretching effect. After the widened optical carrier pulse is amplified by the optical amplifier 3-6, it is divided into two paths by the second optical splitter 3-7: one path is directly converted into an electrical signal by the second photodetector 3-8, and the other path is firstly passed through the third dispersive medium 3-10 with a dispersion amount of 1 ps / nm for further photon time stretching, and then converted into an electrical signal by the third photodetector 3-11. Finally, the two electrical signals are respectively converted from analog to digital by the first analog-to-digital converter 3-9 and the second analog-to-digital converter 3-12, and then enter the DSP 3-13 for digital processing to obtain the information of the detected target. The echo signal of the present invention is broadened by 4 times due to the photon time stretching effect, and the frequency and bandwidth of the signal are equivalently reduced by 4 times. After matched filtering and photoelectric conversion, the echo signal frequency is 2-3GHz and the bandwidth is 1GHz. Therefore, only a low-speed ADC is needed to process it, which greatly reduces the analog bandwidth pressure of the back-end ADC. Theoretically, the radar can achieve a detection resolution of Where c is the speed of light and B is the radar bandwidth.

[0048] The dispersion amounts of the second dispersive medium 3-5 and the third dispersive medium 3-10 are 3ps / nm and 1ps / nm respectively. Therefore, the multiples of the photon time stretching of the two channels are 4 times and 5 times respectively. The delay difference between the reference target echo signal and the target echo signal can be obtained by matching filtering. By comparing with the derived delay difference, the actual delay difference of the target to be measured relative to the reference target before the photon time stretching process can be solved, and then the location information of the target can be obtained.

[0049] Example 2 (Millimeter-wave photon time-stretch coherent radar chip)

[0050] Millimeter wave radar has the advantages of high frequency, high accuracy and good penetration, so it is mainly suitable for long-distance detection. Its main parameters are as follows:

[0051] The pump laser 1-1 is an on-chip integrated semiconductor laser, and the laser form is single-frequency continuous light.

[0052] The on-chip Kerr optical microcavity 1-2 adopts a microring structure, has a length of 2.5 mm, a guided mode as a waveguide mode, a waveguide material of silicon nitride, and a strip waveguide as a waveguide structure. The microring laser mode locking works in a dispersion management mechanism, and the output stretched pulse soliton has a repetition frequency of 80 GHz, a spectral width of 50 nm, and a pulse width of 200 fs.

[0053] The optical splitter 1-3 is an optical coupler.

[0054] The electro-optical modulators 2-2 and 3-4 are light intensity modulators.

[0055] The photoelectric detectors 2-3, 3-8 and 3-11 are PIN tubes.

[0056] The optical amplifiers 3-6 are semiconductor optical amplifiers.

[0057] The dispersive media 3-1, 3-5, and 3-10 adopt on-chip integrated chalcogenide optical waveguides.

[0058] The transmitting antenna 2-5 / receiving antenna 3-2 adopts a phased array antenna.

[0059] The signal generator 2-1 adopts DDS.

[0060] Figure 2 The schematic diagram of the radar signal transmission and reception principle of this embodiment is shown in FIG. The first electro-optic modulator 2-2 in the radar transmitting part 2 loads the linear frequency modulation signal with a bandwidth of 800MHz generated by the signal generator 2-1 onto the optical carrier through the electro-optic modulation effect, and then the heterodyne beat frequency of the first photodetector 2-3 with a bandwidth greater than 80GHz generates a microwave signal with a bandwidth of 800MHz and a millimeter wave frequency band of 80GHz, which is amplified by the power amplifier 2-4 and radiated by the transmitting antenna 2-5.

[0061] After the optical carrier pulse in the radar receiving part 3 is time-stretched by the first dispersive medium 3-1 with a dispersion of 0.25ps / nm, the receiving window formed covers the entire radar detection distance. The specific implementation needs to satisfy the following formula:

[0062] B·D1≥T rep (1)

[0063]

[0064] Among them, T reprepresents the repetition period of the passive mode-locked laser output light pulse, B is the pulse spectrum width, D1 represents the dispersion coefficient of the first dispersive medium; D2 represents the dispersion coefficient of the second dispersive medium. The first formula ensures that within the pulse repetition period, the product of the spectrum width of the output light pulse generated by the femtosecond pulse and the dispersion coefficient can cover the entire detection distance. In the second formula, M is the stretch factor achieved by the designed photon time stretch link.

[0065] The radar echo signal with a millimeter wave frequency band and a bandwidth of 4 GHz received by the receiving antenna 3-2 is amplified by the low noise amplifier 3-3, modulated by the second electro-optical modulator 3-4 and loaded on the optical carrier pulse after time stretching by the first dispersive medium 3-1. After the optical carrier pulse loaded with the radar echo signal passes through the second dispersive medium 3-5 with a dispersion of 5ps / nm (a sulfide material optical waveguide with a larger dispersion value can be used), the echo signal is broadened due to the photon time stretching effect. The broadened optical carrier pulse is amplified by the optical amplifier 3-6 and then divided into two paths by the second optical splitter 3-7: one path is directly converted into an electrical signal through the second photodetector 3-8, and the other path first passes through the third dispersive medium 3-10 with a dispersion of 1ps / nm for further photon time stretching, and then passes through the third photodetector 3-11 to convert it into an electrical signal. Finally, the two electrical signals are respectively converted from analog to digital by the first analog-to-digital converter 3-9 and the second analog-to-digital converter 3-12, and then enter the DSP3-13 for digital processing to obtain the detected target information. The echo signal of the present invention is broadened by 20 times due to the photon time stretching effect, and the frequency and bandwidth of the signal are equivalently reduced by 20 times. After matched filtering and photoelectric conversion, the echo signal frequency is 4GHz and the bandwidth is 20MHz. Therefore, only a low-speed narrowband ADC is needed to process it, which greatly reduces the analog bandwidth pressure of the back-end ADC. The detection distance of the millimeter wave radar chip is greater than 200m, and the detection resolution that the radar can achieve in theory is Where c is the speed of light and B is the radar bandwidth.

[0066] The dispersion amounts of the second dispersive medium 3-5 and the third dispersive medium 3-10 are 5ps / nm and 1ps / nm respectively. Therefore, the multiples of the photon time stretching of the two channels are 20 times and 24 times respectively. The delay difference between the reference target echo signal and the target echo signal can be obtained by matching filtering. By comparing with the derived delay difference, the actual delay difference of the target to be measured relative to the reference target before the photon time stretching process can be solved, and then the target information can be obtained.

[0067] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A photon time-stretch coherent radar chip, comprising a femtosecond pulse generating part (1), a radar transmitting part (2) and a radar receiving part (3), characterized in that: The femtosecond pulse generating part (1) is used to generate femtosecond pulses with high repetition frequency and wide spectrum, and is divided into two paths, one path is used as an optical carrier to input the radar transmitting part (2), and the other path is input to the radar receiving part (3); The radar transmitting part (2) comprises a signal generator (2-1), a first electro-optical modulator (2-2), a first photoelectric detector (2-3), a power amplifier (2-4) and a transmitting antenna (2-5), wherein the signal generator (2-1) is connected to a radio frequency input end of the first electro-optical modulator (2-2); the optical carrier is input into the first electro-optical modulator (2-2), the first electro-optical modulator (2-2) loads the baseband radar signal generated by the signal generator (2-1) onto the optical carrier through an electro-optical modulation effect, and then generates a microwave signal of a required frequency and bandwidth through a heterodyne beat frequency of the first photoelectric detector (2-3), and after being amplified by the power amplifier (2-4), the microwave signal is transmitted by the transmitting antenna (2-5); The radar receiving part (3) comprises a first dispersive medium (3-1), a receiving antenna (3-2), a low noise amplifier (3-3), a second electro-optical modulator (3-4), a second dispersive medium (3-5), an optical amplifier (3-6), a second optical splitter (3-7), a second photodetector (3-8), a first analog-to-digital converter (3-9), a third dispersive medium (3-10), a third photodetector (3-11), a second analog-to-digital converter (3-12) and a DSP (3-13), wherein the output end of the low noise amplifier (3-3) is connected to the radio frequency input end of the second electro-optical modulator (3-4); a path of light input into the radar receiving part (3) enters the first dispersive medium (3-1) and after the photon time is stretched, the formed receiving window covers the entire radar detection distance, and the radar echo signal received by the receiving antenna (3-2) passes through the first dispersive medium (3-1). After being amplified by the low-noise amplifier (3-3), the optical carrier pulse loaded on the optical carrier pulse after photon time stretching is modulated by the second electro-optical modulator (3-4). The optical carrier pulse loaded with the radar echo signal is photon time stretched by the second dispersive medium (3-5). The stretched optical carrier pulse is amplified by the optical amplifier (3-6) and then divided into two paths by the second optical splitter (3-7). One path is converted into an electrical signal by the second photodetector (3-8), and the other path is firstly further photon time stretched by the third dispersive medium (3-10), and then converted into an electrical signal by the third photodetector (3-11); the two electrical signals are respectively converted from analog to digital by the first analog-to-digital converter (3-9) and the second analog-to-digital converter (3-12), and then enter the DSP (3-13) for digital processing to obtain the detected target information; The femtosecond pulse generating part (1) comprises a pump laser (1-1), an on-chip Kerr optical microcavity (1-2) and an optical splitter (1-3); the pump light generated by the pump laser (1-1) enters the on-chip Kerr optical microcavity (1-2) to generate a high repetition frequency wide spectrum femtosecond pulse, and then is split into two paths by the optical splitter (1-3).

2. The photon time-stretching coherent radar chip according to claim 1, characterized in that: The formed receiving window covers the entire radar detection distance, and the femtosecond pulse width and repetition frequency generated by the femtosecond pulse generating part, as well as the first dispersive medium (3-1) and the second dispersive medium (3-5) need to satisfy the following formula: B·D1>T rep (1) Among them, T rep represents the repetition period of the output light pulse of the femtosecond pulse generating part, B is the pulse spectrum width, D1 represents the dispersion coefficient of the first dispersion medium (3-1); D2 represents the dispersion coefficient of the second dispersion medium (3-5), and M is the stretching factor of the photon time stretching link.

3. The photon time-stretching coherent radar chip according to claim 1, characterized in that The pump laser (1-1) is a solid laser, a semiconductor laser, a fiber laser and various types of on-chip light sources, and the laser form is single-frequency continuous light, multi-wavelength laser and pulse laser.

4. The photon time-stretching coherent radar chip according to claim 1, characterized in that The on-chip Kerr optical microcavity (1-2) is in the form of a microring, a microdisk, a microsphere, or a microrod; the waveguide modes are space radiation modes, substrate radiation modes, and guided modes; the waveguide materials are silicon, silicon dioxide, silicon nitride, III-V compounds, lithium niobate, gallium aluminum arsenide, and sulfides or fluorides; and the microring waveguide structure is a strip waveguide, a ridge waveguide, a strip groove waveguide, and a T-shaped or L-shaped waveguide.

5. The photon time-stretching coherent radar chip according to claim 1, characterized in that: The optical splitter (1-3) may be, but is not limited to, an optical power splitter or an optical coupler.

6. The photon time-stretching coherent radar chip according to claim 1, characterized in that: The first electro-optic modulator and the second electro-optic modulator are used to load microwave signals and are optical intensity modulators or phase modulators.

7. The photon time-stretching coherent radar chip according to claim 1, characterized in that: The first photodetector and the second photodetector are used to convert optical signals into electrical signals and are PIN tubes or APDs.

8. The photon time-stretching coherent radar chip according to claim 1, characterized in that: The optical amplifier is used to amplify optical signals and is an erbium-doped waveguide amplifier, a semiconductor optical amplifier or a Raman amplifier.

9. The photon time-stretching coherent radar chip according to claim 1, characterized in that: The first dispersive medium, the second dispersive medium and the third dispersive medium are used for photon time stretching of pulses and are on-chip integrated silicon-based, SiO2, silicon nitride, lithium niobate, tellurite, sulfide, fluoride optical waveguides or dispersive devices.

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