Terahertz radar signal conversion device and terahertz radar

Abstract

The present invention relates to a signal conversion device for a terahertz radar and a terahertz radar. The signal conversion device for the terahertz radar includes an optical signal conversion unit and a microwave signal conversion unit. The optical signal conversion unit includes an optical reference signal source, a microwave signal generation module, a first optical modulation module, a first optical filtering module, a first optical true delay module, and a first photoelectric conversion module, which are connected in series. The microwave signal conversion unit includes a second photoelectric conversion module, a second optical modulation module, a second optical true delay module, a second optical filtering module, and an analog-to-digital conversion module, which are connected in series. The signal conversion device for the terahertz radar combines microwave and photonic technologies to convert ultra-wideband microwave signal processing into narrowband photon processing above the optical threshold. This overcomes a bottleneck that is difficult to overcome with conventional electronics technology and effectively improves the function and performance of the radar.

Description

Technical Field

[0001] The present invention relates to the field of radar technology, and in particular to a signal conversion device for a terahertz radar and a terahertz radar comprising the device. Background Art

[0002] Radar is an electronic device that uses electromagnetic waves to detect targets. It transmits electromagnetic waves to illuminate the target and receives the echoes, thereby obtaining information such as the distance from the target to the emission point, the rate of change of distance, direction, and altitude. Currently, radar frequency bands have extended to millimeter waves. As the wavelength shortens, radar detection accuracy increases. In the continuous development of radar, terahertz radar, due to its short wavelength and rich frequency range, is gradually becoming a development direction for high-precision, anti-stealth radar, and has broad application prospects in both military and civilian applications.

[0003] In existing technologies, terahertz radars are typically constructed using solid-state electronics, using microwave upconversion and multiple frequency multiplication to transmit radar signals in the terahertz band. However, electronic systems struggle to generate and process ultra-wideband radar signals with instantaneous bandwidths exceeding 2 GHz, and electronic components are limited by the frequency band. This leads to problems in the terahertz band, such as poor signal quality, high cable transmission losses, low system sensitivity, and poor detection of small and weak targets. Consequently, the bottleneck of solid-state electronics is hindering the further improvement and development of terahertz radar capabilities. Summary of the Invention

[0004] Based on this, it is necessary to provide a terahertz radar signal conversion device and a terahertz radar including the device that can solve the above-mentioned problems and improve the performance of the radar.

[0005] A signal conversion device for a terahertz radar includes an optical signal conversion unit and a microwave signal conversion unit.

[0006] The optical signal conversion unit includes an optical reference signal source, a microwave signal generation module, a first optical modulation module, a first optical filtering module, a first optical true delay module and a first photoelectric conversion module connected in series in sequence;

[0007] The microwave signal conversion unit includes a second photoelectric conversion module, a second optical modulation module, a second optical true delay module, a second optical filtering module and an analog-to-digital conversion module connected in series in sequence;

[0008] The optical reference signal source is used to generate an optical reference signal;

[0009] The microwave signal generating module is used to convert the optical reference signal into an optical signal of a preset frequency band;

[0010] The first optical modulation module is used to modulate the optical signal of a preset frequency band;

[0011] The first optical filter module is used to perform noise reduction processing on the modulated optical signal;

[0012] The first optical true delay module is used to perform delay processing on the optical signal after noise reduction processing;

[0013] The first photoelectric conversion module is used to convert the delayed optical signal into a microwave signal so that the signal transceiver device sends the microwave signal;

[0014] The second photoelectric conversion module is used to convert the reflected microwave signal received by the signal transceiver into an optical signal;

[0015] The second optical modulation module is used to demodulate the converted optical signal;

[0016] The second optical true delay module is used to perform delay processing on the demodulated optical signal;

[0017] The second filtering module is used to perform noise reduction processing on the optical signal after delay processing;

[0018] The analog-to-digital conversion module is used to convert the optical signal after noise reduction processing into a digital signal, so that the signal processing device can process the digital signal.

[0019] The signal conversion device for the terahertz radar first converts a broadband optical reference signal into a microwave signal that can be transmitted by a signal transceiver through an optical signal conversion unit. The microwave signal conversion unit then converts the received microwave signal into an optical signal, which is then converted into a digital signal, allowing the signal processing unit to process the digital signal and obtain the information contained in the signal. By combining microwave and photonic technologies, the signal conversion device transforms the ultra-wideband microwave signal processing problem into a narrowband photon processing problem above the optical threshold. This overcomes a bottleneck that has been difficult to overcome with conventional electronics technology, effectively improving the radar's functionality and performance.

[0020] In one embodiment, the optical reference signal source is further electrically connected to the second optical modulation module and the analog-to-digital conversion module, respectively, for providing an optical reference signal.

[0021] In one embodiment, the optical reference signal source is an optical oscillator; the frequency of the optical reference signal generated by the optical oscillator is 100 GHz-500 GHz.

[0022] In one embodiment, the first optical modulation module and the second optical modulation module respectively include one or more of a phase modulator, an optical intensity modulator, a frequency modulator, and an optical pulse modulator.

[0023] In one embodiment, the first optical true delay module and the second optical true delay module respectively include any one of a fiber delay device, a fiber grating delay device and an optical waveguide delay device.

[0024] In one embodiment, the first photoelectric conversion module includes a single-row carrier high-speed photodetector.

[0025] In one embodiment, the analog-to-digital conversion module is an optically assisted analog-to-digital converter; and the sampling clock jitter of the optically assisted analog-to-digital converter is less than 100 fs.

[0026] A terahertz radar, comprising a signal transceiver, a signal processing device, and a signal conversion device as described in any one of the above embodiments;

[0027] Among them, the signal transceiver device is electrically connected to the first optoelectronic conversion module and the second optoelectronic conversion module of the signal conversion device, respectively, for transmitting and receiving microwave signals; the signal processing device is electrically connected to the optical reference signal source and the analog-to-digital conversion module of the signal conversion device, respectively, for processing digital signals and obtaining the status information of the target object based on the processing results of the digital signals.

[0028] In one embodiment, the state information of the target object includes one or more information of the distance between the target object and the transmitting point, the distance change rate of the target object, the direction and the altitude.

[0029] In one embodiment, the signal processing device is further electrically connected to a computer device, and the computer device is used to assist the signal processing device in processing the digital signal and / or uploading the status information of the target object to the Internet. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the structure of a terahertz radar in one embodiment. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0032] It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be an element centered thereon. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an element centered thereon. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementations.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0034] In one embodiment, Figure 1 As shown, the present application first provides a signal conversion device 100 for a terahertz radar, which includes an optical signal conversion unit 110 and a microwave signal conversion unit 120. The optical signal conversion unit 110 includes an optical reference signal source 111, a microwave signal generation module 112, a first optical modulation module 113, a first optical filtering module 114, a first optical true delay module 115, and a first photoelectric conversion module 116; the microwave signal conversion unit 120 includes a second photoelectric conversion module 121, a second optical modulation module 122, a second optical true delay module 123, a second optical filtering module 124, and an analog-to-digital conversion module 125.

[0035] In this embodiment, the optical signal conversion unit 110 is used to generate an optical signal and convert the optical signal into a microwave signal. The converted microwave signal can be transmitted into space through an external signal transceiver. When the microwave signal is reflected by an object in space, the reflected microwave signal will be received again by the signal transceiver. The received microwave signal can be converted into an optical signal by the microwave signal conversion unit 120, and then converted into a digital signal. Then, the microwave signal conversion unit 120 can send this digital signal to an external signal processing device. After receiving the digital signal, the signal processing device can compare and analyze the received signal with the transmitted signal to obtain information such as the distance of the measured object from the signal transceiver, the distance change rate of the object, the azimuth and height, thereby realizing the radar function.

[0036] Specifically, in the optical signal conversion unit 110, the input end of the optical reference signal source 111 is connected to the signal processing device, and the output end is connected to the first optical modulation module 113. Its main function is to generate an optical reference signal in the terahertz frequency band. The optical reference signal can be converted into an optical signal of a preset frequency band by the microwave signal generation module 112 connected to the other input end of the first optical modulation module 113. This preset frequency band can be selected according to the microwave signal generated by the microwave signal generation module 112. Then, the first optical module 113 can modulate the optical signal of the preset frequency band so that the optical signal carries specific effective information. Furthermore, the output end of the first optical module 113 can be connected to the first optical filtering module 114. The input end, the output end of the first optical filter module 114 can be connected to the input end of the first optical true delay module 115, wherein the first optical filter module 114 can perform noise reduction processing on the modulated optical signal, and the first optical true delay module 115 can perform delay processing on the optical signal after noise reduction processing. The optical signal after noise reduction and delay processing can effectively improve the measurement accuracy of the radar, for example, it can effectively distinguish two objects that are very close to each other. Finally, the output end of the first optical true delay module 115 can be connected to the input end of the first photoelectric conversion module 116, and the first photoelectric conversion module 116 can convert the optical signal after noise reduction and delay processing into a microwave signal, so that the microwave signal is transmitted into space through the transmitting end of the signal transceiver device.

[0037] Specifically, in the microwave signal conversion unit 120, the input end of the second photoelectric conversion module 121 is connected to the receiving end of the signal transceiver device, which is used to receive the microwave signal reflected from the space. Then, the second photoelectric conversion module 121 can convert the received microwave signal into an optical signal. The output end of the second photoelectric conversion module 121 can be connected to the input end of the second optical modulation module 122, and the second optical modulation module 122 can demodulate the converted optical signal. Furthermore, the output end of the second optical modulation module 122 can be connected to the input end of the second optical true delay module 123, and the output end of the second optical true delay module 123 can be connected to the input end of the second filtering module 124. End, wherein the second optical true delay module 123 can perform delay processing on the demodulated optical signal, and the second filtering module 124 can perform noise reduction processing on the optical signal after delay processing. The optical signal after delay processing can effectively compensate for the offset and jitter in the signal caused by the influence of the atmosphere, and the optical signal after noise reduction processing can effectively filter out the signal outside the preset frequency band, thereby obtaining a high-quality optical signal. Finally, the output end of the second filtering module 124 can be connected to the output end of the analog-to-digital conversion module 125, and the analog-to-digital conversion module 125 can convert the optical signal after delay and noise reduction processing into a digital signal, so that the digital signal can be received and processed by the signal processing device.

[0038] The signal conversion device for the terahertz radar first converts a broadband optical reference signal into a microwave signal that can be transmitted by a signal transceiver through an optical signal conversion unit. The microwave signal conversion unit then converts the received microwave signal into an optical signal, which is then converted into a digital signal, allowing the signal processing unit to process the digital signal and obtain the information contained in the signal. By combining microwave and photonic technologies, the signal conversion device transforms the ultra-wideband microwave signal processing problem into a narrowband photon processing problem above the optical threshold. This overcomes a bottleneck that has been difficult to overcome with conventional electronics technology, effectively improving the radar's functionality and performance.

[0039] In one embodiment, Figure 1 As shown, the optical reference signal source 111 is also electrically connected to the second optical modulation module 122 and the analog-to-digital conversion module 125, respectively, and is used to provide an optical reference signal for the demodulation process and the analog-to-digital conversion process of the optical signal. Specifically, the optical reference signal is required as a reference during both the modulation and demodulation processes of the optical signal to ensure accurate modulation and demodulation of the optical signal; and the optical reference signal is also required as a basis for time calibration during the analog-to-digital conversion process of the optical signal. In this embodiment, the analog-to-digital conversion performed with optical assistance has higher resolution, which can effectively improve the performance of the radar.

[0040] In one embodiment, the optical reference signal source can be an optical oscillator. Preferably, the optical reference signal source can be an optical frequency comb. Specifically, the optical frequency comb can generate a series of evenly spaced optical pulses with a coherent and stable phase relationship. Using the optical frequency comb as the optical reference signal source can easily adjust the frequency difference so that the phase noise does not increase with the increase of the carrier frequency, and can achieve a large bandwidth, which has obvious advantages over electrical devices in the high frequency band. In addition, the frequency of the optical reference signal generated by the optical oscillator can be between 100GHz and 500GHz. Preferably, the frequency of the optical reference signal generated by the optical oscillator can be between 100GHz and 300GHz. In this frequency band, optical signal processing technology is more mature and radar performance is more stable.

[0041] In one embodiment, the first and second optical modulation modules may each include one or more of a phase modulator, an optical intensity modulator, a frequency modulator, and an optical pulse modulator. In this embodiment, the first and second optical modulation modules typically include a phase modulator and an optical intensity modulator. A phase modulator is an optical modulator that changes the phase of light according to a certain pattern, and an optical intensity modulator is an optical modulator that changes the intensity of light according to a certain pattern. Specifically, after the optical signal is modulated by an optical modulator such as a phase modulator and an optical intensity modulator, some signals carrying specific information are superimposed on the optical reference signal, causing certain parameters of the optical signal, such as amplitude, frequency, phase, polarization state, and duration, to change according to a certain pattern. In this embodiment, the first optical modulation module is used to modulate the optical signal, and the second optical modulation module is used to demodulate the optical signal. Modulation and demodulation are mutually exclusive processes and require the use of the same modulation rule and the same optical reference signal.

[0042] In one embodiment, the first and second optical true delay modules can each comprise any one of a fiber optic delay device, a fiber grating delay device, and an optical waveguide delay device. Specifically, the principle of optical delay is as follows: the frequency of an electrical signal is extremely low relative to the optical frequency, so it can be loaded onto an optical signal. This loaded optical signal is then delayed, and then the electrical signal is extracted using a photodetector. The extracted electrical signal is identical to the pre-modulated electrical signal, except for a certain phase delay. This method effectively combines the electrical and optical signals, enabling radar to achieve superior performance. Preferably, the first and second optical true delay modules can be fiber optic delay devices. Fiber optic delay devices can achieve a number of discrete delay values by selecting different optical fiber paths, and multiple transmission paths are also available. In this type of technology, delay accuracy can be ensured by precisely controlling the length of the optical fiber.

[0043] In one embodiment, the first photoelectric conversion module can be a single-row carrier high-speed photodetector. Among them, the single-row carrier photodetector (UTC-PD) is a high-speed photodetector that only uses electrons as active carriers. Its main function is to convert the incident light signal into an electrical signal output, and it can effectively suppress the space charge effect. Specifically, the single-row carrier photodetector includes a highly doped light absorption layer and a wide-bandgap low-doped or undoped electron collection layer. The light absorption layer and the electron collection layer are completely separated in space. Since the bandgap width of the electron collection layer is greater than the energy of the incident photon, the electron collection layer is transparent to the incident light. Then, the incident light can excite the electrons in the valence band of the highly doped light absorption layer to the conduction band, forming electron-hole pairs. For photogenerated holes, holes are majority carriers and respond to form current within their dielectric relaxation time; photogenerated electrons are minority carriers. They are blocked by the wide-bandgap barrier layer and can only diffuse to the collection layer, i.e., forming a single-row carrier. The response time of a single-line carrier photodetector is mainly determined by the diffusion time of electrons in the absorption layer and the drift time in the collection layer. Therefore, a single-line carrier photodetector can produce high bandwidth and saturation output current and is a highly efficient photoelectric converter.

[0044] In one embodiment, the analog-to-digital conversion module can be a light-assisted analog-to-digital converter (ADC). An ADC is a device that converts analog signals into digital signals. Traditional ADCs are primarily electrical, which often suffer from issues such as sampling clock jitter, sample-and-hold circuit transition time, comparator accuracy, and mismatches between transistor thresholds and passive component thresholds. Furthermore, these limitations become more pronounced with increasing RF signal frequencies. To address these limitations, an optically assisted ADC based on a photonic time-domain stretching-assisted structure can effectively overcome these bottlenecks. It can pre-process high-speed RF signals at a reduced speed and capture them at a rate below the Nyquist sampling rate, enabling processing of ultra-high-speed, wideband signals. Compared to the sampling clock jitter of traditional electrical ADCs, which is on the order of hundreds of femtoseconds, the sampling clock jitter of a photon-assisted ADC can be reduced by more than an order of magnitude, reaching below 100 fs, effectively improving the conversion accuracy of the ADC.

[0045] In one embodiment, Figure 1A terahertz radar is also provided, comprising the signal conversion device 100, signal transceiver 200, and signal processing device 300 described in the above embodiment. The signal transceiver 200 further comprises a radio frequency transmitting module 210, a radio frequency receiving module 220, a radio frequency switch 230, and an antenna 240. In this embodiment, the radio frequency transmitting module 210 of the signal transceiver 200 is electrically connected to the first photoelectric conversion module 116 of the signal conversion device 100, and is configured to transmit the microwave signal converted by the optical signal conversion unit 110 into space via the antenna 240. The radio frequency receiving module 220 of the signal transceiver 200 can be electrically connected to the second photoelectric conversion module 121 of the signal conversion device 100, and is configured to receive microwave signals reflected from objects in a certain direction in space, and transmit the microwave signals to the microwave signal conversion unit 120, so that the microwave signal conversion unit 120 can convert the microwave signals into optical signals and then into digital signals. Furthermore, the signal processing device 300 can be electrically connected to the optical reference signal source 111 and the analog-to-digital conversion module 125 of the signal conversion device 100. On the one hand, the signal processing device 300 can control the optical reference signal source 111 to generate an optical reference signal. On the other hand, the signal processing device 300 can also compare and analyze the generated optical reference signal with the received digital signal and obtain relevant information about the target object based on the comparison and analysis results of the digital signal. The terahertz radar in this embodiment has a very short wavelength, much smaller than that of microwaves and millimeter waves, and can therefore detect very small targets and achieve very precise positioning.

[0046] The terahertz radar described above can achieve frequencies exceeding 300 GHz, bandwidths exceeding 10 GHz, and modulation rates exceeding 40 GHz. This compares to current solid-state radars, which can only achieve frequencies around 300 GHz, bandwidths of only around 2 GHz, and modulation rates of only around 10 GHz. This demonstrates that the microwave photonics-based terahertz radar provided in this embodiment can effectively enhance radar functionality and performance, and is an important approach to future terahertz radar implementations.

[0047] In one embodiment, the target object's status information may include information such as the target object's distance from the transmission point, the target object's distance change rate, azimuth, and altitude. As we all know, radar is an electronic device that uses electromagnetic waves to detect targets. It can detect targets and determine their spatial positions using radio frequency methods. Specifically, radar can measure the target object's distance change rate from the transmission point through the frequency Doppler effect generated by the relative motion between itself and the target, thereby measuring the object's movement speed. Radar can also use the antenna's sharp azimuth beam to calculate the target object's altitude based on the elevation angle and distance. Radar can also accurately calculate the distance between the radar and the target object by measuring the time difference between the transmitted pulse and the echo pulse.

[0048] In one embodiment, Figure 1 As shown, the signal processing device 300 can also be electrically connected to the computer device 400. Specifically, the computer device 400 can assist the signal processing device 300 in further processing the digital signal, and can also upload information such as the distance of the target object from the transmitting point, the rate of change of the distance of the target object, the direction and altitude, etc. obtained by the signal processing device 300 to the Internet.

[0049] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0050] The above-described embodiments merely represent several implementation methods of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A signal conversion device for a terahertz radar, characterized in that: The signal conversion device of the terahertz radar includes an optical signal conversion unit and a microwave signal conversion unit. The optical signal conversion unit includes an optical reference signal source, a microwave signal generation module, a first optical modulation module, a first optical filtering module, a first optical true delay module and a first photoelectric conversion module connected in series in sequence; the first optical modulation module includes one or more of a phase modulator, an optical intensity modulator, a frequency modulator and an optical pulse modulator; The microwave signal conversion unit includes a second photoelectric conversion module, a second optical modulation module, a second optical true delay module, a second optical filtering module and an analog-to-digital conversion module connected in series. The optical reference signal source is used to generate an optical reference signal; the optical reference signal source is an optical oscillator; The microwave signal generating module is used to convert the optical reference signal into an optical signal of a preset frequency band; The first optical modulation module is used to modulate the optical signal of the preset frequency band; The first optical filtering module is used to perform noise reduction processing on the modulated optical signal; The first optical true delay module is used to perform delay processing on the optical signal after noise reduction processing; The first photoelectric conversion module is used to convert the delayed optical signal into a microwave signal so that the signal transceiver device sends the microwave signal; The second photoelectric conversion module is used to convert the reflected microwave signal received by the signal transceiver into an optical signal; The second optical modulation module is used to demodulate the converted optical signal; The second optical true delay module is used to perform delay processing on the demodulated optical signal; The second optical filtering module is used to perform noise reduction processing on the optical signal after delay processing; The analog-to-digital conversion module is used to convert the optical signal after noise reduction processing into a digital signal, so that the signal processing device can process the digital signal.

2. The signal conversion device of the terahertz radar according to claim 1, characterized in that: The optical reference signal source is also electrically connected to the second optical modulation module and the analog-to-digital conversion module respectively, and is used to provide an optical reference signal.

3. The signal conversion device for terahertz radar according to claim 1 or 2, characterized in that: The frequency of the optical reference signal generated by the optical oscillator is 100 GHz-500 GHz.

4. The signal conversion device for terahertz radar according to claim 1 or 2, characterized in that: The second optical modulation module includes one or more of a phase modulator, an optical intensity modulator, a frequency modulator, and an optical pulse modulator.

5. The signal conversion device of terahertz radar according to claim 1 or 2, characterized in that: The first optical true delay module and the second optical true delay module respectively include any one of a fiber delay device, a fiber grating delay device and an optical waveguide delay device.

6. The signal conversion device for terahertz radar according to claim 1 or 2, characterized in that: The first photoelectric conversion module includes a single-row carrier high-speed photodetector.

7. The signal conversion device for terahertz radar according to claim 1 or 2, characterized in that: The analog-to-digital conversion module is an optically assisted analog-to-digital converter; the sampling clock jitter of the optically assisted analog-to-digital converter is less than 100 fs.

8. A terahertz radar, characterized in that: The terahertz radar comprises a signal transceiver, a signal processing device, and a signal conversion device according to any one of claims 1 to 7; The signal transceiver device is electrically connected to the first photoelectric conversion module and the second photoelectric conversion module of the signal conversion device, respectively, for transmitting and receiving microwave signals; The signal processing device is electrically connected to the optical reference signal source and the analog-to-digital conversion module of the signal conversion device respectively, and is used to process the digital signal and obtain the status information of the target object according to the processing result of the digital signal.

9. The terahertz radar according to claim 8, characterized in that The state information of the target object includes one or more information of the distance between the target object and the transmitting point, the distance change rate of the target object, the direction and the height.

10. The terahertz radar according to claim 9, characterized in that: The signal processing device is also electrically connected to a computer device, and the computer device is used to assist the signal processing device in processing the digital signal and / or uploading the status information of the target object to the Internet.

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