WO2020057112A1

WO2020057112A1 - Signal conversion device for terahertz radar, and terahertz radar

Info

Publication number: WO2020057112A1
Application number: PCT/CN2019/082376
Authority: WO
Inventors: 杨彬; 李程; 丁庆
Original assignee: 雄安华讯方舟科技有限公司; 深圳市太赫兹科技创新研究院有限公司
Priority date: 2018-09-18
Filing date: 2019-04-12
Publication date: 2020-03-26
Also published as: CN110907924A

Abstract

Disclosed are a signal conversion device (100) for a terahertz radar, and a terahertz radar, wherein the signal conversion device (100) for a terahertz radar comprises an optical signal conversion unit (110) and a microwave signal conversion unit (120), with the optical signal conversion unit (110) comprising an optical reference signal source (111), a microwave signal generation module (112), a first optical modulation module (113), a first optical filter module (114), a first optical true time delay module (115) and a first photoelectric conversion module (116) connected in series in sequence; and the microwave signal conversion unit (120) comprises a second photoelectric conversion module (121), a second optical modulation module (122), a second optical true time delay module (123), a second optical filter module (124) and an analog-to-digital conversion module (125) connected in series in sequence. According to the signal conversion device (100) for a terahertz radar, a processing problem of an ultra-wideband microwave signal is converted into a processing problem of a narrow-band photon in an optical threshold by means of combining microwave technology with photon technology, thereby breaking the bottleneck that conventional electronics technology cannot break and effectively improving the function and performance of a radar.

Description

Signal conversion device for terahertz radar and terahertz radar

Technical field

The invention relates to the technical field of radar, in particular to a signal conversion device of a terahertz radar and a terahertz radar including the device.

Background technique

Radar is an electronic device that uses electromagnetic waves to detect a target. It can irradiate the target by receiving electromagnetic waves and receive its echoes, in order to obtain information about the distance from the target to the point where the electromagnetic wave is emitted, the distance change rate, the orientation, and the altitude. At present, the frequency band of radar has extended to millimeter waves. As the wavelength becomes shorter, the detection accuracy of the radar will increase accordingly. In the continuous development of radar, terahertz radar has gradually become one of the development directions of high-precision, anti-stealth radar in the future due to its short wavelength and rich frequency. It has broad application prospects in military and civilian applications.

In the prior art, terahertz radars are generally constructed by solid-state electronics, that is, the transmission of radar signals in the terahertz frequency band is achieved by microwave upconversion and multiple frequency doubling. However, it is difficult for electronic systems to generate and process them. Ultra-wideband radar signals with instantaneous bandwidth exceeding 2GHz and electronic devices are limited by frequency bands. In the terahertz band, there are problems such as poor signal quality, large cable transmission loss, low system sensitivity, and poor detection ability for weak targets. Therefore, the bottleneck of solid-state electronics restricts the further improvement and development of terahertz radar capabilities.

Summary of the Invention

Based on this, it is necessary to provide a signal conversion device for a terahertz radar capable of solving the problem of ultra-wideband microwave signal processing and improving the performance of the radar, and a terahertz radar including the device.

A signal conversion device for a 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 filter module, a first optical true delay module, and a first photoelectric conversion module connected in series in order;

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 filter module, and an analog-to-digital conversion module connected in series in order;

The optical reference signal source is used to generate an optical reference signal;

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

A first optical modulation module for modulating an optical signal in a preset frequency band;

The first optical filter module is configured to perform noise reduction processing on the modulated optical signal;

The first optical true delay module is used for delay processing the optical signal after noise reduction processing;

The first photoelectric conversion module is used to convert the time-delayed optical signal into a microwave signal, so that the signal transmitting and receiving device sends a microwave signal;

The second photoelectric conversion module is configured to convert the reflected microwave signal received by the signal transceiver to an optical signal;

The second optical modulation module is configured to demodulate the converted optical signal;

The second optical true delay module is used for delay processing the demodulated optical signal;

The second filtering module is used to perform noise reduction processing on the delayed optical signal;

The analog-to-digital conversion module is used to convert the noise-reduced optical signal into a digital signal, so that the signal processing device processes the digital signal.

The above-mentioned terahertz radar signal conversion device first converts a broadband optical reference signal into a microwave signal that can be transmitted through a signal transmitting and receiving device through an optical signal conversion unit, and then converts the received microwave signal into an optical signal through the microwave signal conversion unit. It is then converted into a digital signal, so that the signal processing device can process the digital signal and learn the information carried in the signal. The signal conversion device of the above terahertz radar, by combining microwave technology and photon technology, converts the problem of ultra-wideband microwave signal processing into the problem of narrow-band photon processing above the optical threshold, breaking the bottleneck that conventional electronics technology is difficult to break through. Improved radar function and performance.

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.

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.

In one embodiment, the first optical modulation module and the second optical modulation module include one or more of a phase modulator, a light emphasis modulator, a frequency modulator, and a light pulse modulator, respectively.

In one embodiment, the first optical true delay module and the second optical true delay module include any one of a fiber delayer, a fiber grating delayer, and an optical waveguide delayer.

In one embodiment, the first photoelectric conversion module includes a single-line carrier high-speed photodetector.

In one embodiment, the analog-to-digital conversion module is a light-assisted analog-to-digital converter; the sampling clock jitter of the light-assisted analog-to-digital converter is less than 100 fs.

A terahertz radar includes a signal transceiving device, a signal processing device, and a signal conversion device according to any one of the foregoing embodiments;

The signal transceiver 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 respectively connected to the optical reference signal source and analog-to-digital conversion of the signal conversion device. The module is electrically connected to process digital signals and obtain status information of the target object based on the processing results of the digital signals.

In one embodiment, the status information of the target object includes one or more pieces of information about the distance of the target object from the emission point, the rate of change in the distance of the target object, the position and the height.

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 to process digital signals and / or upload status information of the target object to the Internet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural diagram of a terahertz radar in an embodiment.

detailed description

In order to make the purpose, technical solution, and advantages of the present application clearer, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the application, and are not used to limit the application.

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 a centered element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and are not meant to be the only implementations.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of the present application is only for the purpose of describing specific embodiments, and is not intended to limit the present application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

In one embodiment, as shown in FIG. 1, the present application first provides a signal conversion device 100 for a terahertz radar. The device 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 filter 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 filter module 124, and an analog-to-digital conversion module 125.

In this embodiment, the optical signal conversion unit 110 is configured to generate an optical signal and convert the optical signal into a microwave signal. The converted microwave signal can be transmitted to the space through an external signal transmitting and receiving device. When the microwave signal is transmitted by the space, After an object is reflected, the reflected microwave signal will be received by the signal transceiver again. 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 This digital signal can be sent to an external signal processing device. After receiving the digital signal, the signal processing device can compare and analyze the received signal and the transmitted signal to know the distance signal receiving and transmitting device of the measured object. Distance, the rate of change of the distance of the object, the azimuth, and the altitude to achieve the radar function.

Specifically, in the optical signal conversion unit 110, the input end of the optical reference signal source 111 is connected to a signal processing device, and the output end is connected to the first optical modulation module 113. Its main role is to generate a light reference signal in the terahertz frequency band. The reference signal can be converted into an optical signal of a preset frequency band by the microwave signal generating 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 generating 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 valid information. Further, the output end of the first optical module 113 can be connected to the first optical filter module. 114 input, the output of the first optical filter module 114 can be connected to the input 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 filter The delay module 115 can perform delay processing on the optical signal after noise reduction processing, and the optical signal after noise reduction and delay processing can have It can effectively improve the measurement accuracy of the radar, for example, it can effectively distinguish two objects that are 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. The conversion module 116 can convert the optical signal after the noise reduction and delay processing into a microwave signal, so that the microwave signal is transmitted into the space through the transmitting end of the signal transceiver.

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 transmitting and receiving device for receiving the microwave signal reflected from the space. Then, the second photoelectric conversion module 121 may convert The received microwave signal is converted into an optical signal. The output of the second photoelectric conversion module 121 can be connected to the input of the second optical modulation module 122. The second optical modulation module 122 can demodulate the converted optical signal. The output of the second optical modulation module 122 can be connected to the input of the second optical true delay module 123, and the output of the second optical true delay module 123 can be connected to the input of the second filtering module 124. Among them, the second The 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 delayed optical signal, and the delayed optical signal can effectively compensate the signal The offset and jitter caused by the atmospheric influence in the middle, and the optical signal after noise reduction processing can effectively filter the signals outside the preset frequency band, so that Obtain a high-quality optical signal. Finally, the output of the second filtering module 124 can be connected to the output of the analog-to-digital conversion module 125. The analog-to-digital conversion module 125 can convert the delayed and noise-reduced optical signals into digital signals. Thereby, the digital signal can be received and processed by the signal processing device.

In an embodiment, as shown in FIG. 1, 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 for demodulating the optical signal and analog-to-digital conversion of the optical signal. The process provides a light reference signal. Specifically, the optical reference signal needs to be used as a reference in the modulation process and the demodulation process of the optical signal, so that the modulation and demodulation process of the optical signal can be accurately performed; and during the analog-to-digital conversion process of the optical signal It is also necessary to use an optical reference signal as the basis for time calibration. In this embodiment, the analog-to-digital conversion performed with light assistance has a higher resolution, which can effectively improve the performance of the radar.

In one embodiment, the optical reference signal source may be an optical oscillator. Preferably, the optical reference signal source may specifically select an optical frequency comb. Specifically, the optical frequency comb can generate a series of uniformly spaced light 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. Large, and can achieve a large bandwidth, compared to electrical devices in the high frequency band has obvious advantages. In addition, the frequency of the optical reference signal generated by the optical oscillator may be between 100 GHz and 500 GHz. Preferably, the frequency of the optical reference signal generated by the optical oscillator may be 100 GHz-300 GHz. In this frequency band, the optical signal processing technology is more Mature, radar performance is more stable.

In one embodiment, the first optical modulation module and the second optical modulation module may include one or more of a phase modulator, a light emphasis modulator, a frequency modulator, and a light pulse modulator, respectively. In this embodiment, a phase modulator and a light emphasis controller are more commonly included in the first optical modulation module and the second optical modulation module. The phase modulator is a light modulator that changes the phase of light according to a certain rule. The light emphasis controller is a light modulator that changes the light intensity according to a certain law. Specifically, after the optical signal is modulated by an optical modulator such as a phase modulator and a light emphasis modulator, some signals carrying specific information are superimposed on the optical reference signal, so that certain parameters in the optical signal such as amplitude and frequency , Phase, polarization state and duration change according to certain rules. In this embodiment, the first optical modulation module is used for modulation of the optical signal, and the second optical modulation module is used for demodulation of the optical signal. The processes of modulation and demodulation are opposite to each other, and it is necessary to use the same modulation rule and the same type. Light reference signal.

In one embodiment, the first optical true delay module and the second optical true delay module may include any one of a fiber delayer, a fiber grating delayer, and an optical waveguide delayer. Specifically, the principle of optical delay is: the frequency of the electrical signal is extremely low relative to the optical frequency. You can load it onto the optical signal, then delay the optical signal loaded with the electrical signal, and then use light detection The device extracts the electrical signal. The extracted electrical signal and the electrical signal before modulation have the same characteristics except that there is a certain delay in the phase. This method can effectively combine the electrical signal with the optical signal. To make the radar get better performance. Preferably, the first optical true delay module and the second optical true delay module may specifically be optical fiber delayers. The optical fiber delayer may obtain several discrete delay values by selecting different optical fiber paths, and the transmission path may also be There are many options. In this type of technology, delay accuracy can be guaranteed by precisely controlling the length of the fiber.

In one embodiment, the first photoelectric conversion module may be a single-row carrier high-speed photodetector. Among them, the single-line carrier photodetector (UTC-PD) is a high-speed photodetector that uses only electrons as active carriers. Its main function is to convert the incident optical signal into an electrical signal output, and it can effectively Suppresses space charge effects. Specifically, the single-row carrier photodetector includes a highly doped light absorption layer and a wide band gap low-doped or undoped electron collection layer. The light absorption layer and the electron collection layer are completely separated in space. The band gap width of the collection layer is greater than the energy of the incident photons, so 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 electrons- Hole pairs. For photo-generated holes, holes are the majority carriers, which respond to form a current within their dielectric relaxation time. Photo-generated electrons are minority carriers, which are blocked by a wide band gap barrier. Can only diffuse into the assembly layer, that is, form a single row of carriers. 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 generate high bandwidth and saturated output current. Efficient photoelectric converter.

In one embodiment, the analog-to-digital conversion module may be a light-assisted analog-to-digital converter. Among them, the analog-to-digital converter is a device that converts analog signals into digital signals. Traditional analog-to-digital converters are mainly electrical analog-to-digital converters. Electrical analog-to-digital converters are usually in the jitter of the sampling clock. Over time, there are many problems with the accuracy of the comparator and the mismatch between the threshold value of the transistor and the threshold value of the passive component, and the greater the frequency of the RF signal, the more obvious its limitation becomes. To address these shortcomings, the photo-assisted analog-to-digital converter based on the photon time-domain broadening auxiliary structure can well break through the above bottlenecks. It can decelerate pre-processing of high-speed RF signals and reduce the speed of the Nyquist sampling rate. Capture RF signals at a rate to achieve ultra-high-speed, large-bandwidth signal processing. Compared with the hundreds of femtoseconds of sampling clock jitter of traditional electric analog-to-digital converters, the sampling clock jitter of photon-assisted analog-to-digital converters can be reduced by more than an order of magnitude to less than 100fs, which can effectively improve the analog-to-digital conversion. Converter's conversion accuracy.

In one embodiment, as shown in FIG. 1, a terahertz radar is further provided. The terahertz radar includes the signal conversion device 100, the signal transceiver device 200, and the signal processing device 300 described in the above embodiment. The signal transceiving device 200 further includes 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 transceiving device 200 is electrically connected to the first photoelectric conversion module 116 of the signal conversion device 100, and is used to transmit the microwave signal converted by the optical signal conversion unit 110 into the space through the antenna 240 ; The radio frequency receiving module 220 of the signal transceiving device 200 may be electrically connected to the second photoelectric conversion module 121 of the signal converting device 100, for receiving a microwave signal reflected from an object in a certain direction in space, and transmitting the microwave signal to The microwave signal conversion unit 120 enables the microwave signal conversion unit 120 to convert a microwave signal into an optical signal and then into a digital signal. Further, the signal processing device 300 may be electrically connected to the optical reference signal source 111 and the analog-to-digital conversion module 125 of the signal conversion device 100 respectively. On the one hand, the signal processing device 300 may control the optical reference signal source 111 to generate an optical reference signal, and the other In one aspect, the signal processing device 300 may also compare and analyze the generated optical reference signal with the received digital signal, and obtain related information of the target object according to the comparison and analysis result of the digital signal. The wavelength of the terahertz radar in this embodiment is very short, much smaller than the wavelengths of microwaves and millimeter waves, so it can detect very small targets and have very accurate positioning.

The above terahertz radar can have a frequency of more than 300 GHz, a bandwidth of more than 10 GHz, and a modulation rate of more than 40 GHz. Compared with the current solid-state electronics radar, its frequency can only reach about 300 GHz and its bandwidth is only about 2 GHz. The modulation rate is only around 10GHz. It can be seen that the terahertz radar based on microwave photonics provided in this embodiment can effectively improve the function and performance of the radar, and is an important implementation method of the terahertz radar in the future.

In one embodiment, the state information of the target object may include information such as the distance of the target object from the emission point, the rate of change of the distance of the target object, the orientation, and the height. We know that radar is an electronic device that uses electromagnetic waves to detect targets. It can find targets by radio and determine their spatial position. Specifically, the radar can measure the rate of change of the distance of the target object from the emission point through the frequency Doppler effect caused by the relative movement between itself and the target, thereby measuring the speed of the object's movement; the radar can also use the sharp azimuth beam of the antenna, and The height of the target object is calculated by the elevation angle and the distance; the 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.

In one embodiment, as shown in FIG. 1, the signal processing apparatus 300 may also be electrically connected to the computer device 400. Specifically, the computer device 400 can assist the signal processing device 300 to further process the digital signal, and can also upload information such as the distance of the target object from the emission point, the distance change rate of the target object, and the orientation and height acquired by the signal processing device 300. To the internet.

The technical features of the embodiments described above can be arbitrarily combined. In order to simplify the description, all possible combinations of the technical features in the above embodiments have not been described. However, as long as there is no contradiction in the combination of these technical features, It should be considered as the scope described in this specification.

The above-mentioned embodiments only express several implementation manners of the present invention, and their descriptions are more specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be noted that, for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made, which all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent shall be subject to the appended claims.

Claims

A signal conversion device for a terahertz radar, characterized in that 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 filter module, a first optical true delay module, and a first photoelectric conversion module connected in series in order;

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 filter module, and an analog-to-digital conversion module connected in series in order;

The optical reference signal source is used to generate an optical reference signal;

The microwave signal generating module is configured to convert the optical reference signal into an optical signal of a preset frequency band;

The first optical modulation module is configured to modulate an optical signal in the preset frequency band;

The first optical filter module is configured to perform noise reduction processing on the modulated optical signal;

The first optical true delay module is configured to delay process the optical signal after the noise reduction process;

The first photoelectric conversion module is configured to convert the delayed optical signal into a microwave signal, so that a signal transmitting and receiving device sends the microwave signal;

The second photoelectric conversion module is configured to convert the reflected microwave signal received by the signal transceiver to an optical signal;

The second optical modulation module is configured to demodulate the converted optical signal;

The second optical true delay module is configured to delay process the demodulated optical signal;

The second filtering module is configured to perform noise reduction processing on the delayed optical signal;

The analog-to-digital conversion module is configured to convert the noise-reduced optical signal into a digital signal, so that a signal processing device processes the digital signal.
The signal conversion device for a terahertz radar according to claim 1, wherein 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.
The signal conversion device for a terahertz radar according to claim 1 or 2, wherein the optical reference signal source is an optical oscillator; and the frequency of the optical reference signal generated by the optical oscillator is 100 GHz-500 GHz. .
The terahertz radar signal conversion device according to claim 1 or 2, wherein the first optical modulation module and the second optical modulation module each include a phase modulator, a light emphasis modulator, and a frequency modulator. And one or more of optical pulse modulators.
The signal conversion device for a terahertz radar according to claim 1 or 2, wherein the first optical true delay module and the second optical true delay module respectively include a fiber delayer and a fiber grating delay Either a timer or an optical waveguide delay.
The signal conversion device for a terahertz radar according to claim 1 or 2, wherein the first photoelectric conversion module comprises a single-line carrier high-speed photodetector.
The signal conversion device for a terahertz radar according to claim 1 or 2, wherein the analog-to-digital conversion module is a light-assisted analog-to-digital converter; and the sampling clock jitter of the light-assisted analog-to-digital converter is less than 100fs.
A terahertz radar, characterized in that the terahertz radar includes a signal transceiver device, a signal processing device, and a signal conversion device according to any one of claims 1-7;

The signal transceiving device is electrically connected to the first photoelectric conversion module and the second photoelectric conversion module of the signal conversion device, respectively, and is configured to transmit and receive 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 configured to process the digital signal, and obtain a target object according to a processing result of the digital signal. status information.
The terahertz radar according to claim 8, wherein the state information of the target object comprises one of the distance of the target object from the emission point, the rate of change of the distance of the target object, the azimuth, and the altitude, or Multiple information.
The terahertz radar according to claim 9, wherein the signal processing device is further electrically connected to a computer device, and the computer device is used to assist the signal processing device to process the digital signal and / or The state information of the target object is uploaded to the Internet.